A CYCLOPEDIA OF QUANTITATIVE CHEMICAL ANALYSIS. BY FRANK HR STORER, A. M., PROFESSOR OF GENERAL AND ANALYTICAL CHEMISTRY TN THE MASSACHUSETTS INSTITUTE OF TECHNOLOGY. SEVER, FRANCIS & CO., rosion slt C alalrb1870g. 1870. Entered according to Act of Congress, in the year 1870, by FRANK H. STORER, in the Office of the Librarian of Congress, at Washington. PtESS OF A. A. KINGMAN, BOSTON. PREFACE TO PART I. THE object of the author in compiling this book has been not only to provide the student and working chemist with a comprehensive dictionary of quantitative processes, but to call the attention of the chemical fraternity to the question of the possibility of presenting this branch of chemical art in a more serviceable and manageable form than has been customary hitherto. The experiment is certainly worth the trying whether a definite system of classifying substances in alphabetical order, and of referring each and every process to the fundamental fact or principle upon which it depends, will not greatly facilitate both the study and the practice of analysis. The difficulty of perfecting the first edition of a work of this kind will be manifest to all. The author has consequently no apology to offer for the manifold short comings of his book. He wislies it to be understood distinctly that he has copied freely from the Handbooks of Rose, Fresenius, Berzelius, and Pfaff; from the lHandwoerterbuch der Chemie, and from the Dictionary of Watts. It is to be remarked, in that connection, that the similarity of wording in the descriptions of analytical processes in these various treatises is often so close that it would frequently be very difficult to determine precisely where credit should be accorded, or to judge how much credit should be given to each author. It is evident that in a subject which depends so nearly upon the precise statement of details, no compiler would be likely to depart far from the original description, as set forth by the inventor of a process. A good illustration of this inevitable tendency to repetition may be seen in the similarity of Pfaff's, Rose's and Fresenius's descriptions of Berzelius & Hisinger's process depending upon the insolubility of succinate of iron. References are given in all cases where matter has been taken from the journals and other original sources. The manuscript of Part I. was completed, as now printed, in June, 1869. Nothing has been added to it, whether as regards matter or arrangement, from either of the treatises which have been published since that date, excepting the description, under Carbonate of Calcium, of Prof. Lawrence Smith's process, for estimating alkalies,-copied from Prof. Johnson's edition of Fresenius's Quantitative Analysis, New York, 1870. It is noteworthy that the tendency of all the works recently published on quantitative analysis is towards condensation and abbreviation, while the aim of the present book is to show that perspicuity cn be best gained by amplification, if need be, and method'ical arrangement. The author believes that the interests of chemists and of chemical students alike demand two kinds of books upon quantitative analysis. The one kind looking to completeness in all directions, while the other is given over either to specific instruction, or to the discussion of special applications of analysis in some one of the various departments of Chemistry. It is not only important that the analyst should have a dictionary of all known methods, fr'om which to choose the one which seems best to fulfil the conditions and requirements of any new problem which may come before him, but there will always PREFACE. be needed books or tables devoted to schemes for illustrating the various kinds of analyses which are likely to occur in practice. Such, for example, as the works of Wolff and Caldwell, in the department of agricultural chemistry; or, in its day, the Handbuch of Pfaff, in the branch of mineral analysis. But if we were once in possession of a General Encyclopaedia, covering the entire field of analysis, it would be easy to draw up long lists of these special schemes in very few words. For example:A residual product from some of the chemical works at Stassfurt, in Germany, sent into commerce to be sold as a fertilizer, contains the sulphates of potassium, magnesium and calcium; the chlorides of potassium, sodium and magnesium; and a quantity of oxide of iron, magnesia and sand, insoluble in water. But the commercial value of' any given sample of the substance depends upon the proportion of potassium which is contained in it. Several methods have been emplcyed for estimating the potassium,-after the matters insoluble in water have been got rid of by filtration. They might be briefly described as follows:A. Remove the SO3 with BaCI2, as Sulphate of Barium; the Mg with BaO, H,O, as Hydrate of Magnesium; the Ca and excess of Ba with (NH4)20, CO2, as Carbonate of Barium, and estimate the K as Chloride and Chloroplatinate of Potassium. B. Remove S03 by means of BaCI2, as Sulphate of Barium, decompose the Chloride of Magnesium with oxalic acid, and separate Mg as Oxide of Magnesium. Determine K as Chloroplatinate of Potassium. C. Remove the SO3 with BaCl,, as Sulphate of Barium; the Ba, Ca and Mg with Na2O, CO2, as Carbonate of Barium, etc. Acidulate the filtrate with HC1 and estimate K as Chloride and Chloroplatinate of Potassium. D. Remove the S03 with BaC12, as Sulphate of Barium, and estimate K in the filtrate as Chloroplatinate of Potassium (Stohmann's process). The author of any such tables would of' course give reasons why and when either of the processes would be preferred to the others. In the appendix to the present work, a few examples for students' practice will be given in this sense. N. B. All temperatures are given in degrees of the Centigrade thermometer, —excepting when otherwise expressly stated. In the references to authorities, the larger figures indicate the volume, and the smaller figures the page, of the journal or work alluded to; single figures in parentheses () denote the number of the series of the journal. The names of authors who have labored in concert are connected by the character C, not by and. To avoid the repeated printing of unnecessary words, cross references are indicated by printing in capitals the initial letters of the names of the substances referred to. Thus, on page 5, column 1, line 25, the capital initials in the words Oxide of Aluminum indicate that the article OXIDE OF ALUIINUM must be consulted, and that further information will be found under that head. The names of rare elements have been omitted from this edition simply from lack of time to deal with them. In order that the size and cost of the book might be kept within reasonable bounds, it has been thought best to exclude from it all figures of apparatus. The descriptions of unusual forms of apparatus have, however, been given in minute detail, and, in case of having to use any of this apparatus, the reader will do well to draw rough figures of it for himself. with pen or pencil,-fbllowing the printed description, step by step. It is believed that if the descriptions be dealt with in this way, no great difficulty will be found in comprehending them, or in choosing that one among several processes which is best suited to the wants of the operator. All ordinary implements and apparatus will be best understood from the descriptions given in works devoted specially to chemical manipulation. Boston, July, 1870. A CYCLOPEIDIA OF QUANTITATIVE CIHEMICAL ANALYSIS. Acetic Acid. is of but little significance. It was fouhd not Principle 1. Power of neutralizing alkaline to exceed one-tenth of one per cent in deterimsolutions. inations made with solutions containing ten Applications. Estimation of free acetcl acid per cent of the monohydrated acid, and is in vinegar, pyroligneous acid and other aque- usually even smaller than this, since a slight ous solutions. (Method A), Determination excess of test-alkali is almost always added to of acetic acid in certain acetates from which the solution under examination, This source caustic soda precipitates insoluble hydrates or of inaccuracy may practically be eliminated oxides. (Method B). by using a standard soda solution, the value Method A. A weighed or measured quantity of which has been determined beforehand by (10 grms. of vinegar will be enough in most means of pure acetic acid. To prepare such a cases) of the solution to be examined is red- solution, measure off a determined quantity of dened slightly with litmus, and then treated standard sulphuric acid, mix it with a moderwith test-alkali until the whole of the acid is ate excess of acetate of sodium, and determine neutralized and the color of the litmus changed how much of the standard soda solution is reto blue. (See Acidimetry). quired to neutralize the acid mixture. By A solution of caustic soda is usually em- operating with a soda solution, whose power ployed as the test-alkali, though solutions of of' changing red litmus to blue in presence of carbonate of sodium were formerly much used. acetate of sodium has been thus determined Greville Williams (Pharm. Journ. Trans.) 1854, empirically, the danger of error from the al13. 594), has urged that a standard solution kaline reaction of' the acetate may be in great of' lime in sugar water is to be preferred to measure avoided. soda, and Otto (in his Lehrbuch der Essiqfabri- According to Merz (Journ, prakt. Chem., kation, 1857, p. 77) has shown that dilute am- 101. 301), it is well to use a solution of turmonia water may sometimes be employed with'meric instead of litmus as the indicator; for advantage. Other test-liquors are employed acetate of sodium has no action upon the color in particular cases, as will be described below, of turmeric. Enough of the turmeric solution The test-alkali is added to the acid under is mixed with the acid to be tested to color it examination until the color of the litmus ap- bright yellow; the liquid is heated nearly to pears distinctly blue, or until a drop of the boiling, and the soda solution stirred in rapidly alkaline liquor is no longer seen to form a blue until the moment when the color of the yellow spot when it falls into the colored liquid. liquid changes to brown. It has been objected to the use of soda or According to Greville Williams, the best of potash in estimating acetic acid, that the way is to dispense with soda altogether, and process must be inaccurate, since the normal'to employ in its place a solution of lime in acetates of the alkali metals themselves exhibit sugar water (see Acidimnetry); for acetate of a slight alkaline reaction with litmus, or, at all calcium has not nearly so much power to disevents, change the color of litmus to violet. guise the action of acids upon litmus as the But as Otto (Annal. Chem. und Pharm., 1857, acetates of sodium and potassium have, to say 102. 71) has shown, the error from this source nothing of the advantage which the. lime soln1 2 ACETIC ACID. tion necessarily possesses, in being at all times alkaline, although no precipitate has been seen free from carbonic acid. For ordinary rapid to form in it. Mohr directs that the beaker work in testing vinegars, Williams finds that which contains the diluted vinegar be placed the process may be fully relied on to one-fourth on a black ground, and that the operator, of one per cent. while stirring the liquid, should look into it In testing crude pyroligneous acid, or highly from above. - Another method, somewhat colored vinegar, the color of the litmus added related to that of Kieffer, is to use a copper to the liquid is- so much obscured towards the salt as the indicator instead of litmus. A few close of the operation by the impurities with drops of a solution of pure sulphate of copper which the acid is charged, that the exact point are added to the vinegar, and a standard soluof neutralization cannot be determined by tion of soda is poured into the mixture until mere inspection of the liquid. It is necessary, the moment when a faint persistent cloudiness, as the point of saturation approaches, to test due to precipitated hydrate of copper, appears the liquid with litmus paper. To this end, in the liquid. The point of saturation may be after each fresh addition of the alkali, the readily hit in this way in vinegars which are point of the glass rod used for stirring is drawn transparent and free from suspended matters, across a narrow sheet of litmus paper, and even though they be somewhat colored. from the color of the mark thus formed, the Instead of the processes above referred to, progress of the neutralization is inf'erred. which are of comparatively recent invention, When the paper ceases to be reddened by vinegar makers have long been accustomed to the liquid, the operation is finished. For some determine the strength,of their products by eyes turnmeric paper may be adivantageously means of carbonate of sodium or carbonate of substituted for the litmus paper. A brown potassium. According to Otto, the method of spot or ring will form upon the yellow paper as procedure is as fobllows: —Select a suitable numsoon as the acid has all been neutralized and ber of clear, transparent, non-effloresced crysthe slightest excess of free alkali is present in tals of hydrated carbonate of sodium, rub the liquid. them to coarse powder in a mortar, and preIn the case of vinegars so highly colored serve the powder in a tightly stoppered bottle. that the point of neutralization cannot be sat- Weigh out in a capacious flask or beaker fifty isfactorily determined even with litmus paper, grms. (custom prescribes 2 Troy ounces = 960 the proportion of acetic acid may be found, grains) of the vinegar to be tested, and add according to Carl Mohr, as follows:-Boil a to it a couple of drops of a solution of litnmus. measured sample of the vinegar with a weighed Set the flask in an inclined position upon a excess of carbonate of barium until no more wire gauze support and heat it moderately carbonic acid is given off. Separate the dark with a lamp. Put 30 or 40 grins. (or about a colored, soluble acetate of barium by filtration; Troy ounce) of the powdered carbonate of throw the moist filter, with its contents of car- sodium in a weighing tube and counterpoise bonate of barium into a beaker, and pour upon the tube with its contents upon a balance. it a measured volume of standard nitric acid, By means of a small spoon or spatula, take more than sufficient to dissolve the whole of portions of the carbonate of sodium from the the carbonate. Finally determine the free weighing tube and carefully throw them into nitric acid with a standard solution of soda, the warm vinegar in the flask until the red and calculate the proportion of acetic acid color of the vinegar is changed to blue. When from the quantity of carbonate of barium the point of neutralization has been reached, which the nitric acid dissolved. The process replace the weighing tube with the unused is evidently liable to error, inasmuch as acetic portion of its contents upon the balance, and acid is readily volatile at the temperature of by adding weights to make good the loss, deboiling.. termine how much of the carbonate has been F. Mohr (Titrirmethode, 18557 p. 362) claims required to effect the neutralization. The to have obtained good results in estimating quantity of acetic acid in the solution tested is acetic acid by means of the standard solution readily obtained by the following proportion:of ammonio-sulphate of copper, proposed by Molec. Wt. of Kieffer (see Acidimetry), as a substitute for Molecularwelght weight Weight of Acetic of ~ N. ~o CQ+ 10oo:s0 (= Acid ) test-alkali.. n using this solution, however, Na2co3 + 10o2o Acetie used in the the acetic acid must be so highly diluted that Acid Sample. a precipitate shall form immediately, from the The molecular weight of acetic acid in the very first, at the point where the test solution second term of the proportion may be derived comes in contact with the acid liquor. The either from the formula C2,HO (anhydrous close of the operation will be indicated by the acetic acid), or C2H402 (monolhydrated acetic fact that the precipitate ceases to redissolve acid), according as the strength of the sample when stirred. Unless the acid be very dilute, is to be expressed in terms of anhydrous or of considerable quantities of the sub-salt of cop- hydrated acid. In practice, the strength of per will remain dissolved in the acetate of acetic acid is stated sometimes in one way, and copper whichforms. It may even happen that sometimes in the other. In case 2 ounces = the solution of acetic acid can be made strongly 960 grains of vinegar, are taken, every 27 ACETIC AcID. 8 grains of crystallized carbonate of sodium re- any druggist, For a description of a gradquired to effect neutralization will represent uated instrument specially devised for the use one per cent of anhydrous. acetic acid, or of vinegar makers, in which vinegar may be every 22.8 grains one per cent of the mono- neutralized with standard ammonia water, hydrated acid. see Otto's Lehrbuch der Essigfarbrication, p. To avoid loss of material during the tumult- 77 et seq. uous ebullition caused by the evolution of car- An old method of testing vinegar was as bonic' acid, care should be taken that the flask follows: —Weigh a lump of pure, dry marble, or beaker in which the vinegar is heated is place it in a measured quantity of vinegar, never more than about a quarter full of the insufficient to dissolve the whole lump, and liquid. The carbonate of sodium should be warm the liquid slightly, until all the acid is taken up by small fractions, and no new por- saturated with calcium. Wash the undissolved tion of it should be added to the liquid until portion of marble with boiling water, dry it at the last portion has ceased to give off gas. the same temperature as before, and again Just before each fresh addition of the carbon- weigh it. From the loss of weight calculate ate the liquid should be shaken in such man- the amount of' acid in the sample examined. ner that any drops of it which may have been Objections to this process are found in the thrown against the upper side of the inclined difficulty of washing out the acetate of calcium vessel shall be washed down into the main fiom the porous stone as well as in the slow acbody of liquor. The spoon used fbr transfer- tion of acetic acid upon marble, and the imposring the carbonate of sodium should be kept sibility of bringing the marble to absolutely the as dry as possible. ~ In case the steam from the same state of dryness before and after the flask wet it, it should be rinsed at the mouth action of the acid. (Gr. Williamsi Pharm, of the flask with a wash bottle and afterwards Journ. Trans., 1854, 13. 595). dried. Method B. To determine acetic acid in As long as the color of the solution remains acetates from which c(austic soda precipitates bright red, the carbonate of sodium may be hydrates or oxides, such as ferric acetate or added with freedom and rapidity; but when acetate of copper, mix a weighed quantity of the point of neutralization is near at hand, only the acetate with a measured quantity of a very small portions of the carbonate should be standard solution of caustic soda or carbonate added. In any event the color of the liquid of sodium, more than sufficient to decompose serves merely as a rough indication of the the whole of the acetate. Heat the mixture progress of the experiment. Litmus paper to boiling, collect the precipitate upon a filter; must be used as a test of thorough saturation. wash it with hot water, concentrate the filtrate As soon as the color of the solution becomes to a convenient bulk and determine the excess obscure, small drops of' the liquid must be of alkali with standard acid. The difference placed upon litmus paper after each addition between the amount of soda thus found and of the carbonate, until the paper ceases to be the amount of soda taken, gives the quantity of reddened, or is actually turned blue. It is not soda which has been neutralized by the acetic best to color the -vinegar intensely red at the acid in the substance analyzed. The amount start. Two or three drops of litmus will color of acetic acid is found by the proportion: - it sufficiently, When the vinegar is strongly Molec. wt. Molec. wt. Wt. of Soda. wt. of acid\ reddened at first, it is apt to acquire a violet of NaiO of CtH4e2 neutralized insample. tint towards the close of' the operation which Care must be taken that none of the acid is tends to obscure the reaction of the solution lost by precipitation as a basic acetate in the upon paper. In case the vinegar is strongly first instance. Since a good deal of carbonic heated, it is best not to add any litmus to it acid would be absorbed from the air during until the comparatively sluggish evolution of the evaporation of the filtrate in case caustic carbonic acid indicates that the point of' neu- soda were employed, it is as well to use a tralization is almost reached. The crystals of standard solution of carbonate of sodium, carbonate of sodium chosen for this use should (See Acidimetry). be free from any spots of efflorescence. In- To determine the unused excess of alkalif stead of crystals of' sal-soda, some vinegar the solution may be heated to boiling, colored makers prefer to use the anhydrous, recently with litmus, and directly saturated with stands ignited carbonate. In any event, carbonate ard acid; or an excess of standard acid may of sodium is to be preferred to carbonate of be added at once, the solution boiled to expel potassium, although the latter, at one time carbonic acid, reddened with litmus, and then exclusively employed, is still sometimes used. treated with a standard solution of caustic The use of standard solutions of carbonate of soda until a blue tint is imparted to it. sodium is not to be commended. They are inferior in all respects to solutions of the fnlike most of the other acids, the strength caustic alkalies. It has been already men- of a solution of acetic acid cannot be detertioned that. Otto recommends the use of am- mined by taking the specific gravity of the monia water four or five times diluted, chiefly solution. Not only are the differences in because this liquid may be readily obtained of density correspondint to different proportions 4 ACETATES. of acid very small,-ranging only from 1.057, is contaminated with a chloride, the salt may the specific gravity of glacial acetic acid, to be distilled with chlorhydric instead of phos1,000, the specific gravity of water,-but the phoric acid. The proportion of chlorhydric differences are not regular, or directly propor- acid in the distillate would in that case be detional to the amounts of acid in the solution. termined by titrating one portion of it with a Thus the specific gravity of a solution con- solution of silver (see Chloride of Silver), taining only 37 per cent of anhydrous acetic after the total amount of acetic acid and chloracid is almost absolutely identical with that of hydric acids had been determined in another a solution containing 85 per cent. Solutions portion with standard scda. The proportion of vinegar and of crude pyroligneous acid are of acetic acid would then be inferred froml the often met with, moreover, charged with vary- difference. Sulphuric acid cannot readily be ing proportions of other soluble substances, so employed, since sulphurous acid is formed that this method of estimation would not ad- through its action upon organic matters atmit of general application in any event. tached to the acetate of calcium. (Fresenius, The strength of pure vinegars made from Zeitsch. Analyt. Chem., 1866, 5. 315). diluted alcohol, whiskey, or other distilled Principle Ill. Feeble solvent action; or spirit, may, however, be tested with the hy- rather, power of dissolving certain substances drometer indirectly, as follows:- Add dry without acting upon others. slaked lime to a measured quantity of the Applications. Acetic acid is used to aciduvinegar, to alkaline reaction, or, better, until late liquids in many cases where stronger acids the color of the solution suddenly changes to are inadmissible. See, for example, Acetate of.yellow or brown, while a fiocculent precipitate Aluminum, Acetate of Iron, Chromate of Baforms in the liquid. This change of color, due rium, Phosphate of Iron, Phosphate of Urato the presence of impurities in the vinegar, nium, etc., etc. indicates that an excess of lime has been The commercial acid of 1.04 specific gravity, added. Cool the solution of acetate of calcium containing about 25 per cent of the anhydrous to 15~ an'd test it with a hydrometer. By ref- acid, is usually pure enough and strong enough erence to a table of specific gravities and per- for purposes of analysis. It should be tested centage composition of solutions of acetate of with solutions of nitrate of silver, nitrate of calcium, the proportion of this salt and, there- barium, and of indigo; with sulphnretted hyfrom, the proportion of acetic acid, may read- drogen, and with ammonia water and sulphyily be obtained. "The process is well adapted drate of ammonium before use, in cases where for technical determinations. (Ordway, Amer. the presence of chlorine, sulphuric acid, nitric Journ. Sci., 1861, 31. 451). It was form- acid, sulphurous acid, or of either of the heavy erly employed in' England by excise officers, metals would be prejudicial. If pure, the acid but could hardly have afforded accurate results will neither leave any residue when evaporated with vinegar made from malt, cider, etc., on on platinum foil, nor emit an empyreumatic account of the various soluble mucilaginous odor on being heated after having been satusubstances with which such vinegar is charged. rated with carbonate of sodium. Principle 11. Volatility. In order to purify an impure acid, mix it Application. Estimation of the acid in crude with some acetate of sodium, and slowly distil acetate of calcium. the liquid almost to dryness in a glass retort. Method.'Weigh out about 5 grins. of the In case sulphurous acid has been detected by acetate of calcium, place it in a small tubulated the deposition of sulphur on testing with sulretort, together with 50 c.c. of water and 50 phuretted hydrogen, digest the acid for some c.c. of ordi-nary phosphoric acid of about 1.2 time with binoxide of' lead or precipitated specific gravity, free from nitric acid. Set the binoxide of manganese, and decant the clear retort on a wire gauze support in such a posi- liquid before adding the acetate of sodium. tion that its neck may slope slightly upwards. Acetate of Aluminum. By means of tightly fitting corks and a deliv- Principle. Insolubility in water of certain ery tube, connect the mouth of the retort with basic acetates of aluminum. These acetates sepa small Liebig's condenser, and distil almost arate when neutral or nearly neutral aqueous to dryness. Collect the distillate in a quarter- solutions of acetate of aluminum, which conlitre flask, taking care that none of it is lost. tain some other salts, are heated. (Compare Allow the retort to become cold, pour into it Dictionary of Solubilities). 50 c.c. more wrater, again distil almost to dry- Applications. Determination of aluminum ness, and afterwards repeat the operation yet in most compounds of aluminum with inora third time. Add water to the distillate by ganic or volatile organic acids, which are solusmall portions, agitating the mixture after each ble in water or chblorhydric acid. Separation of addition, until the flask is filled up to the Al from Li, K, Na; Ba, Ca, -Sr, Mg, Mn, Ur, quarter-litre mark. Then draw off portions Fe (see Method B.), Co and Zn; less conmof 50 c.c. or 100 c.c. with a pipette, and de- pIetely from Ni. The method is employed termine the acid contained in them by means more particularly when both Al and Fe have of a normal solution of' caustic soda, as de- to be separated together from the other metals. scribed in A. In case the acetate of' calcium Method A. Put the cold, moderately dilute, ACETATES. 5 somewhat acid solution in a flask or beaker, long continued, lest the hydrate of aluminum and add to it carbonate of sodium by small become slimy and stop the plores of the filter. lumps, or amlmonia water little by little, until Unless a considerable excess of acetate of the acid is so nearly saturatedl that on shak- sodium be employed, an appreciiable quantity ing the liquid the l)recipitate formed by the of aluminuim will escape precipitation; the prelast addition of alkali barely dissolves. Add cipitate, in this case, has a peculiar (ranular to the clear, cold liquid a few drops of acetic appearance. In case the filtration is slow, acid, and then pour in as much of a.strong somle aluminum will pass Into the filtrate, and aqueous solution of normal acetate of sodium, may be separated therefronl on boiling.'rhis or acetate of ammlonium, as may be needed subsidiary precipitate should be collected on to convert by double decomposition all the a separate filter. - The precipitate usually bases present into normal acetates. Heat the retains insignificant traces of soda, but should mixture to boiling, and continue to boil for not exhibit a strong alkaline reaction when a short time. If the operation has been prop- moistened with water after, ignition. In case erly conducted, the precipitate will settle read- the presence of sodium salts in the filtrate is ily from the liquid in the form of transparent undesirable, ammonia-water and acetate of flocks, when the lalmp is removed. ammonium must be employed instead of the Pour the clear, hot liquor upon a filter, wash carbonate and acetate of sodium. - lThough the precipitate two or three times by (lecanta- tile precipitate cannot be very conveniently filtion with boiling water, to which some acetate tered and washed, and though traces of alumiof sodium, or acetate of anmmoninum, has been num always remain in the filtrate, the process adlded; transfer the precipitate to the filter and affords satisfactory results when carefully exe-. finish the washinT on the filter with boiling cuted. It is less esteemed, however, than the water. - The precipitate is dried, ignited corresponding process for determining iron. mand weighe as Oxile of Alumninum; with the (Se Acetate of Iron). The analogous process precautions prescribed under that head. Or, based upon the insolubility of basic Formiate in case peculiar accuracy is required, the moist of Aluminum is preferable, inasmuch as the precipitate is dissolved in chlorhydric acid and forlniate may be washed more readily than the again thrown down with acetate of sodium, to acetate. remove the last traces of the stronger bases. Acetate of Barium,.. Jlethlod B. In separating iron from alumi- Princille. Power of preciitating sulphates num by this process, the two elements are and chromates. Compare Acetic Acid (feeble thrown down together as basic acetates. The solvent power of). mixed precipitate is ignited with the precau- Al)Vlications. Acetate of barium is used as tions enjoined under Acetate of Iron, and a reagent to precipitate sulphate of' barium or weighed as alumina plus ferric oxide. The chromate of barium in cases where the presence proportion of iron is then determined by titra- of chlorllhydric or nitric acid would be inadmistion. (See prot Oxide of Iron). The differ- sible. To prepare the acetate, dissolve pure ence between the wei(ght of ferric oxide thus carbonate of barium in moderately dilute acetic obtained and that of the mixed precipitate, acid, filter, evaporate and set the strong solugives the weight of the alumina. tion aside to crystallize; keep the dry crystals Precautions. According to Gibbs & Atkin- for use. son (Anmer. Jourun. Sci., 1865, 39. 60), the' Acetate of Iron (Ferric Acemletals in the original solution had better be in tate). the form of chlorides. If the original solution' Prilciple I. Insolubility in water of certain contains any considerable excess of acid, this basic acetates of iron. These acetates separate excess should be removed by evaporation, and when neutral, or nearly neutral, aqueous soluthe solution again diluted with water before tions of ferric acetate, which contain some adding the carbonate of' sodium or flle atlmo- other salts, are boiled. (Compare Dictionary of nia. T'he solution should be so dilute that a Solubilities). litre of it would contain no more than two A)plications. Determination of iron in salts grins, of A1903, or of A1203 plus Fe2O3, in case of iron, with most inorganic or volatile organic both iron an]d aluminum were present. In acids, which are soluble in water or chlorhlydrie case the liquid become turbid through the acid. Separation of Fe from Li, K, Na; Ba, addition of too much alkali, it should be made Ca, Sr; Mg, Ur, Al, Mn, Co and Zn; less clear again by the least possible quantity of completely firoml Ni. Separation of Fe2O3 from chlorhydric acid before proceeding to add the FeO. (Iethod B). acetic acid and acetate of sodium. After boil- M]lethod A. Similar in all essential particuing the mixture,*it should be filtered hot, for lars to that described under Acetate of Aluniif the supernatant liquid were left to cool in num. contact with the precipitate, some of the latter Precautions. According to Fresenius, the would dissolve. For the same reason, it is best success of the operation depends on the iron to employ a plaited filter and to allow the filter solution being sufficiently dilute, and the free to becollme empty after each addition of liquid acid sufficiently neutralized, as well as upon before refilling it. The boiling must not be too the presence of a sufficient excess of acetate 6 ACETATES. of sodium. If these conditions are complied potassium, remove the boiling liquid from the with, all the iron will be thrown down as soon lamp, and stir into it crystals of acetate of as the liquor boils. It is not necessary in any sodium as before, to precipitate the ferric oxide. event to boil the mixture longer than two or If the oxidized solution contains no substance, three minutes. besides ferric oxide, precipitable by anllonia Unless it is intended to separate FeO from in presence of ammoniull salts, the iron may Fe2O. (as in Method B), the iron must all be of course be thrown down as Hydrate of Iron in the condition of a ferric salt before the in the usual way. liquid is neutralized. After the addition of the Manganous oxide, or a mixture of mangracarbonate of sodium, or the ammonia-water, nous and ferrous oxides, may be separated from the liquid should assume a deep brownish-red ferric oxide in a similar way by imixing thle color, but no permanent precipitate should be oririnal chlorhydric acid solution with chloride allowed to form in it before the alkaline ace- of sodinum, and hydrate or carbonate of sodium, tate is added. The filtration should be rapid, in place of' the chloride of amnlmonium and as with the aluminum salt, and the supernatant ammnonia water just described. The FeO and liquor should not be allowed to cool in contact MnO are subsequently oxidized with chlorate with the precipitate. If, after boiling, the mix- of' potassium to FeO0 and Man2%), and the ture were left to itself for several hours, a Fea03 thrown down by means of a new portion susall quantity of iron would go into solution. of acetate of sodiun. Sometimes, though not often, portions of the Reichardt recommends that the acetate of precipitate pass mechanically through the sodium be added in all cases in the form of pores of the filter, and have to be collected crvstals, as above described, after the boiling upon another filter after standing six or eirght liquid has been removed from the lamp, even hours. The washed precipitate had better be when iron is to be separated from the alkaline dissolved in chlorhydric acid while still Imoist, earths, and from phosphates of the alkaline and the iron reprecipitated with amnionia as a earths. According to him, boiling as (iirected hydrate. If the precipitate is small, however, in Method A renders the precipitate more it may be ignited and weighed directly as Oxide difficult of filtration, besides being objectionable of Iron, taking care to oxidize any ferroso-ferric on other accounts. oxide which may form, by a final ignition in Principle Ji. Colorific Power. oxygen gas, or with addition of nitric acid. Applications. Estimation of small quantities The process is convenient, and affords accu- of iron, as in the analysis of rocks. rate results, tlhough the corresponding process Jietfhod. A special instrument known as a with Formiate of. Iron is said to be prefbrable, colorimeter is required. (See Colorimletry). inasmuch as fbrmiate of iron is more readily For a description of the process of analysis, washed than the acetate. which is not yet perfected, see a paper by A. Method B. To separate Fe2O3 from FeO, Iiiller in Zeitsch. analyt. Cl/em., 1863, 2. 143. Reichardt (Zeitsch. analyt. Chemn., 1866, 5. 63, Acetate of Lead. 64) mixes the hot cllorhydric acid solution Principle. Ready solubility in water, and of the two oxides with a tolerably large quantity power of precipitating many acids. Comlpare, of chloride of ammonium, dilutes the mixture for example, Sulphate of Lead, Chromate of largely with boiling water, neutralizes the hot Lead, Phosphate of Lead, etc. solution with ammlonia, and irmlmediately re- The best commercial acetate of lead is usudissolves the precipitate with a few drops of ally pure enough. For use, dissolve one part chlorhydric acid, The clear liquid is then of the salt in ten parts of water acidulated heated to actual boiling, immediately removed with a few drops of acetic acid, from the fire and treated with an excess, but Acetate of Sodium (or of Ponot too larger an excess, of crystals of acetate of tassium). sodium. In a very short time after the crys- Principle. Easy decomposition of the salt tals have been stirred into the liquor, all the by strong acids, and feeble solvent power of iron in the ferric salt will separate as a floccu- the acetic acid set free. lent precipitate, which may be filtered imme- Applications. Substitution of acetic for diately arid washed with boiling water. The chlorhydric, sulphuric, or nitric acid in strongly province of the chloride of ammonium is to acid solutions. Compare, for example, the hinder the oxidation of the ferrous salt. It Acetates of' Aluninum and of Iron, or Phosaccomplishes this purpose so well that the fil- phate of Iron. trate fi om the precipitated ferric acetate might The commercial salt is usually pure enough; be left standing in the air for hours and still it should be free from emnpyreumnatic matter. remain clear and colorless. To determine the Dissolve one part of it in ten tarts of water. proportion of ferrous oxide: —Heat the filtrate Acetate of U ranium. to boiling, add chlorhydric acid, drop by drop, Principle. Power of precipitating Arseniate until the liquid renmains permanently clear; of Uranium and Phosphate of Uranium. throw in small crystals of chlorate of potas- To prepare the acetate, heat finely powdered sium until a drop of the liquid no longer yields pitch blende with dilute nitric acid, treat the blsUe color when tested with forri-cyanide of iltrate with sulphuretted hydrogen to throw ACIDIMETRY. 7 down copper, lead and arsenic; filter again, the common acids are volatile, it is easy to deevaporate the filtrate to dryness, and heat the tect the presence of nonvolatile impurities by residue stronfrly enough to decompose the ni- evaporating a portion of the acid to dryness in trates of iron, cobalt and manganese. Boil a suitable dish. Of the acids in common use, the residue with water and again filter. Evap- acetic acid is the only one which cannot orate the filtrate to crystallize nitrate of ura- readily be tested with the hydrometer when nium, purify the nitrate by recrystallization, pure. See Specific Gravity and Hydrometer and heat the crystals until a little of the ses- in this work, or in almost any treatise on quioxide of uranium is reduced. Dissolve the Chemical or Physical Mlanipulation. yellowish-red mass in warm acetic acid, filter Mllethod B. By neutralization with an allcaand let the filtrate crystallize. Acetate of line solution of determined strength. The prinsesquioxide of uranium will crystallize out, ciple upon which this method depends is that while the nitrate of uranium, which escaped caustic alkalies and alkaline earths combine decomposition, remains dissolvedin the mother readily with free acids to form neutral salts, liquor. Or, saturate a solution of protochlo- having no action upon litmus and certain other ride of uranium with ammonia-water, and coloring matters, while the presence of the dissolve the precipitate in hot acetic acid. smallest excess of either acid or alkali is inA solution of acetate of uranium should stantly made manifest by its action upon the give no precipitate when tested with sulphu- coloring matter. retted hydrogen. But on the addition of car- After a standard alikaline solution of definite bonate of ammonium, a precipitate, soluble in strength has once been prepared, it is easy to an excess of the carbonate, should be pro- determine the amount of' acid in any weighed duced. or measured sample of an acid solution by Acidimetry. adding to it a few drops of a solution of litmus, A term applied to methods of estimating the and then pouring in the standard alkali until amount of free acid in acid solutions. the red color of the litmus just changes to blue. Method A. By Specific Gravity. It has The quantity of alkali required to effect this been found by experience that the specific change being noted in each case, the quantity gravity of a mixture of water and an acid is -of acid contained in the sample is readily asgreater than that of pure water; that, as a certained by calculation from the known value general rule, the specific gravity of such mix- of the alkali. tures increases with the proportion of acid The standard alkaline solution. most comcontained in them, and that each particular monly employed, is prepared from caustic soda; mixture has a certain definite specific gravity but a solution of caustic potash, or of caustic peculiar to itself. Consequently, if the specific lime in sugar water, would do as well. Amgravity corresponding to each and every per monia water is sometimes used, and so are cent of any given acid be carefully determined, solutions of carbonate of sodium, of borax, and once for all, by experiments upon mixtures of of anmmonio-sulphate of copper. - Instead pure acid and pure water, made expressly for of litmus, various other coloringe matters may be the purpose, it will afterwards be easy to deter- employed to indicate the point of saturation. mine the proportion of that acid in any aque- See, in particular, Cochineal, Logwood and ous solution by taking the specific gravity of Turmeric. the latter and comparing the result with those Standard Caustic Soda [or Standard Caustic of the standard experiments, provided only Potash] is prepared through the intervention that no substance besides the acid in question of a standard acid (see Alkalimetry) as folbe dissolved in the solution. lows:-Nlake a solution of caustic soda by The relations between specific gravity and boiling carbonate of sodium with hydrate of per cent of pure acid have been determined calcium in the usual way,l and dilute the clear experimentally for solutions of all the more caustic liquor until its specific gravity is about common acids, and the results of these' ek- 1.06, corresponding to five per cent of hydrate periments, expressed in numbers arranged in of sodium. Measure off into a porcelain dish, tabular form, will be found in most of the die- or a beaker placed upon white paper, thirty tionaries of Chemistry. (See Dictionary of c.c. of' test acid (see Alkalimetry), and add to Solubilities.) the liquid as much of a violet solution of litIn testing the value of an acid mixture in mus as may be necessary to give it a faint red this way, the Hydrometer is sufficiently accu- tint. Fill a burette2 with the solution of rate for most purposes. It is very commonly caustic soda, and pour the latter into the test employed in the scientific laboratory as well as acid until the red tint just changes to blue. in the work-shop. The precautions to be no- Repeat the experiment with another portion of ticed are, that the test must either be applied at the temperature to which the Standard 1 Or Simply dissolve some caustic potash, such as surgeons use, in water, and boil the solution with enough Table refers, or the observation must be cor- slaked lime to decompose any carbonate of' potassium rected for that temperature, and that the sam- which may be present. ple of acid tested must be free, or nearly free, 2 For descriptions of the various forms of this instrumet and of Erdmann's float, used to ensure accuracy from soluble contaminations. Since many of in reading, see the works on Chemical Manipulation. ACIDIMETRY. the test acid, and if the two results agree, pro- kali used, express directly the percentage of ceed to dilute the alkaline solution in the acid (either anhydrous or hydrated) in the manner described under Alkalimetry (test sul- sample tested.'This may be accompllislle(l by phuric acidl), so that each volume of it shall using normal alkali, and operating upon a be cap>l-bie of exactly neutralizing a volume of weighed quantity of the acid to be tested e(lual test acid. In case twenty-five c. c. of the sodla to one-tenth or one twentieth of an equivalent solution were suflicient to neutralize the thirty weight of the acid sought for, expressed in c. c. of test acid, five c. c. of water would have grainnmes. The following table gives the numlto be added to every twenty-five c. c. of that her of grammes of each of the more comlnmon soda solution to reduce it to the proper extent, acids which must be taken in this event:or for every one thousand c. c. of the soda solution two hundred c. c. of water. When the \ standard solution is made of such strength that the alkali in one thousand c. c. of it will Name of the acid. exactly neutralize an equivalent weight of any acid (expressed in grammeS), it is called'. ~a nornlmal. Anhydrous Acetic Acid, 5.1 2.55 Normal solution of soda is well adapted for M1ioohydrateqd - B 6.0 3.00 Chlorhydric Acid, 8.65 1.83 the ordinary operations of acidimetry, but Anlllydrou Nitric Acid, 54 21.8 whenever the quantity Qf acid to be neutra- Hydrated... 6.3 3.15 Aniydrous Oxilic Acid, 3.6 1.80 lized is small, it is best to use comparatively Crystallize ccid, 63 8.15 dilute solutions of standard alkali. To this Anhydrous Sulphuric Acid, 4.0 2.00 end the normal solution may be diluted five 3Ionohydrated. 4.9 2.45 Anhydrous Tartaric Acid, 6.6 3.30 times, or ten times, with water. To prepare a Hydrated id,.6 3. "one-tenth normal" solution, for example, measure off fifty c. c. of the normnal solution Since the small quantities expressed in the with a pipette, allow the liquid to flow into a above table could hardly be weiglled out dilialf-litre flask, fill the latter with water to the rectly with sufficient accuracy, it is best to mark, and shake the mixture thoroughly. weigh out half equivalent weights (or in other In order to keep the standard soda solution words, five times as many gramnmes as are infree fromn carbonic acid, the bottle which con- dicated in the first columnt of figures) of the tains it may be provided with a cork carrying acids, in a five hundred c. c. flask; to fill the a bulb tube open at both ends, filled with soda- flask with water to the mark, and after shaklime, so that air free firom carbonic acid may ing its contents to measure out portions of the pass into or out of the bottle, accordingly as liquid with a pipette, for analysis. One hundred the barometric pressure or temperature of the c. c. or fifty c. c. of the liquid must be taken, air changes. Sometimes it will be found con- according as one-tenth or one-twentieth of an venient to provide a syphon tube through equivalent wei-ht of the acid is to be used. which the soda solution may be drawn off In diluting the acid with water, care must be without need of opening the bottle. In this taken if need be, to cool the mlixture before event a bent glass tube reaching nearly to the adding the last drops of water. bottom of the bottle is fitted to the cork beside A Standard Solution of Limle in szuar weater the bulb tube, and to the end of its outer limb, has the merit of' being always firee finom carwhich reaches to a point below the bottle, is bonic acid, for in case the solution absorbs any attached a short piece of caoutchouc tubing. carbonic acid from the air, insoluble carbonate After the syphon has once been filled, the of calcium is precipitated. To prepare the caoutchouc tube is kept compressed with a solution, add slaked lime to a cold, moderately spring clip, excepting at the nioments when strong, but not too strong solution of white portions of the solution are allowed to flow out, sugar, as long as any of it will dissolve. Filter In most cases, however, this syphon arrange- the solution, determine its strength by means ment may be dispensed with, of a standard acid, and dilute with as mnuch Instead of taking pains to make the soda water as may be needed. The solution of solution normal, as above described, it is often course becomes weaker in proportion as it abmore convenient to choose a solution of soda sorbs carbonic acid from the air, though the of' about the proper degree of concentration, deterioration is found to be very slow when as determined by the hydrometer; to determine the liquor is kept in tightly stoppered bottles. its strength accurately by means of a standard The strength of the solution must, on this acacid, and then to use it directly as test alkali count, be redetermlined by means of standard without any further preparation. This method acid at the beginning of any new series of of procedure of course necessitates a short determinations, or accordingr to Gr. Williams calculation in each case, in order to obtain the (Phlarm. Jolrn. Tralns., 1854, 13. 596), at inpercentage of acid. tervals of four or five weeks. One advantage It is convenient sometimes in technical anal- of the lilne solution is found in the fact that yses to have the numbll-l of cubic centimletres, acetate of calcium has less action upon the or half cubic centimetres, of the standard al- color of litmlus than the acetates of sodiulm and ACTDIMETRY. potassium. The lime solution is consequently A standard solution qf Arnmonia-water is to well fitted for testing Acetic Acid. be commended in certain cases, inasmuch as Standard SolftionZs of Linie water and of the strong liquor necessary for its preparl)'atio flaryta water are used with advantage against may be obtained ready made of every druggist. oxalic acid and sulphuric acid for estimnating Were it not for the easy volatility of ammlonia, Carbonic Acid, (After Dalton & Hadfield, and and the consequent difficulty of keeping a Pettenkofer). - Pasteur also (Dingler's standard solution of it unchanoged or any polytech. Jour., 190. 139 and Zeitsclh. analyt. great length of time, it would be often emlChlea, 8. 86) employs lime water against sul- ployed in acidimetry. phuric acid for determining the amount of acid A standarcd solution of Carbonate of Sodium in must (unfermented grape juice). For this may readily be prepared by weighing out a purpose a dilute standard acid is prepared, of convenient quantity of pure, anhydrous carsuch strength that ten c. c. of it shall contain bonate of sodium, and dissolving it in a deter0.06125 grin. of the mIonohydrate, and saturate mined quantity of water;-fifty-three grins. to about twenty-seven c. c. of lime water. This the litre would be the proportion for a normal quantity of sulphuric. acid is equivalent to solution. 0.0725 grm. of anhydrous malic acid, to 0.09375 So far as mere preparation is concerned, a grm. of crystallized tartaric acid and to 0.2351 standard alkaline solution may evidently be grin. of cream of tartar. Ten cubic centime- obtained in this wa snmore directly and with tres of clear, filtered must are taken for an less risk of error than by the roundabout experiment, and the standardized lime water methods required in the case of the caustic is poured into it from a burette graduated to alkalies. But since the reaction of carbonic tenths of cubic centimeters. Since must al- acid upon litmus interferes with the reaction ways contains substances which are colored by of the stronger acids and of the alkalies, a soalkalies, it is not necessary to add any litmus lution of carbonate of sodium is inferior-as a to indicate the point of saturation. It is not standard alkali —to a solution of caustic soda.. well, for that matter, even to use litmus paper It is seldom used in acidimetry, though someat the close of the operation, for malate and times employed in the preparation of standard tartrate of calcium exhibit an acid reaction acids, as will be explained under Alkalimletry. with litmus, just as the acetate does. (See (See standard nitric acid). If a solution of Acetic Acid). The lime water should merely cochineal be employed instead of litmus to be added to the must, rapidly and without in- indicate the point of saturation, the disturbing termission, until the character of the color of influence of carbonic acid is far less marked. the liquid changes, or in case the must be col- Instead of using a coloring matter as the inorless at first, until the appearance of a toler- dicator, the point of saturation may be deterably pronounced yellow color. One or two mined by the precipitation of carbonate of ldrops should be subtracted from the amount of barium, as follows:.-Add a small quantity of lime water actually used, in order to reduce the a solution of chloride of barium to the acid to reading from the point of supersaturation to be tested, set the beaker which contains the that of saturation. mixture upon a black ground and pour into it As a rule, no precipitate of any kind falls a standard solution of carbonate of sodium, at the moment when the color changes, but if until a persistent cloudiness, due to p)recipthe mixture be left at rest for a few minutes, itated carbonate of barium, pervades the or better, for a half hour or hour, it will be- liquor. - Acids which, like sulphuric acid, come cloudy from deposition of granular crys- form insoluble compounds with bariuim, may be tals of normal tartrate of calcium, or more treated with a slight excess of chloride of bararely, of a double compound of tartrate and riuin, the mixture filtered to separate the inmalate of calcium, which contains one mole- soluble barium salt, and the filtrate, or some cule of each salt plus sixteen molecules of definite fraction of it, may then be titrated water. These precipitates are easily distin- with the standard carbonate ofsodium (Mohr). guishable under the microscope. No hain is Standard solution of Biborate of Sodium. done in case the precipitate should form during Like carbonate of sodium, borax is an excelthe titration. lent material for preparing a standard alkaline Whenever there is any difficulty in filtering solution, inasmuch as any desired quantity of a sample of must, a quantity of the standard the dry or crystallized salt may be weighed lime water insufficient to effect complete satu- directly upon the balance. A weighed cquanration, may be added to a measured quantity tity of borax has only to be dissolved in as of the muddy liquor —enough, for example, to much water as may have been determined upon, make the liquid give a blue reaction upon in order to complete the preparation of the sensitive red litmus paper; the solution may standard solution. - The boracic acid set then be filtered, and lime water added, drop free when the borax solution is mixed with by drop, to ten c. c. of the clear filtrate, until strong acids has far less action upon the color the color changes. It is then easy to reckon of litmus than is exerted by carbonic acid. how much lime water in all has been neutra- Perfectly satisfactory results can in fact be lized by acid in the must. obtained by titrating acids with the borax solu 10) AAIDIMETRtY.. tion, even when nothing but litmus is employed phate, or some other neutral salt, of copper, to indicate the point of neutralization, espe- which has been fbrmed by the combination of cially if the solution to be tested be hot. But a portion of the acid under examination with if a fresh decoction of Brazil wood be em- some of the copper in the test liquid. At'the ployed as the indicator, instead of litmus, the end, therefore, the ammonia in the test liquid influence of boracic acid upon the final reac- combines with the acid of this neutral copper tion becomes wholly inappreciable. The solu- salt, and the copper contained in it is thrown tion of Brazil wood should be prepared from down in the form. of a subsalt at the samne time clippings taken directly from solid blocks, not with that from the test liquid, so that the volfrom the clippings which are to be found in ume of the precipitate is very considerable. commerce. The yellow Brazil wood solution The completion of the process is thus made is colored purple by alkalies, but becomes of a distinctly manifest, for the appearance of the clearer yellow or reddish tint, when brought turbidity shows that the point of saturation into contact with acids. (Stolba, Journ. pratk. has been reached. Chem., 1864, 90. 459). The solution is brought to the required Since borax is rather sparingly soluble, it is strength, and is employed for determinini impossible to employ a normal solution of it. acids in precisely the same way as a soda soluEven a one-quarter normal solution, which tion, with the single exception that the point would contain only 47.75 grins. to the litre, of saturation is indicated by the appearance,sometimes deposits crystals in cold weather. of a precipitate instead of by a change of The use of borax solutions is consequently color, as when litmus or cochineal is employed. limited to those cases where only a dilute test This modification of the ordinary acidinlealkali is needed. (Salzer, liaohr's Titrirmeelh- tric process offers no special advantages in so ode, 1856, 2. 102). far as relates to pure acids, excepting Acetic Standard Solution of Ammnonio-Sulphate of Acid, as already described, and is altogether Copper. Instead of using a standard solution inapplicable in the case of acids which form of pure alkali to neutralize the acid which is to insoluble compounds with copper, such, for be estimated, and a solution of litmus or other example, as oxalic, tartaric and phosphoric coloring matter to indicate the point of satura- acids. It is peculiarly well adapted, on the tion, it is quite possible to make a single solu- other hand, for those cases where a fi ee acid is tion serve both purposes. A solution of mixed with any of the so-called acid salts. It chloride of silver, for example, in ammonia may be employed, for example, to determine water, or of oxide of zinc in potash, soda or the free acid in the partially spent liquorsammonia, of alumina in potash or soda, or, charged with sulphate of' zinc-of galvanic best of all, of basic sulphate of copper in am- batteries, or in the mother liquors resulting monia water, may be employed both to neutra- from the manufacture of sulphate of copper or lize the acid, and to show when the neutrali- sulphate of zinc. zation is complete. Since the basic sulphate of copper is not abThe solution of ammonio-sulphate of copper solutely insoluble in solutions of ammnoniui (first proposed by Kieffer, Annal. der Chem. salts, the method is not to be commended in uwd Pharm., 93. 386) is prepared by adding cases where strict accuracy is required. Carey ammonia water to a tolerably strong, warm, Lea (Amer. Journ. Sci., 1861, 31. 190) has aqcueous solution of sulphate of copper, until shown that the precipitate dissolves with conthe basic sulphate at first thrown down has al- siderable facility in a solution of' sulphate of most completely dissolved; the liquid is then ammonium, that it is likewise soluble, though filtered, and its strength determined by titra- perhaps to a lesser degree, in solutions of chlotion with a standard acid, which may be either ride and of' nitrate of anlmonium, and that a chlorhydric, nitric or sulphuric. Oxalic acid largesr or smaller quantity is held dissolved, cannot be used in this case, since an insoluble according as the saline solution is more or less oxalate of copper would be formed and the dilute. In practice, therefore, different results liquid obscured. When the ammonio-sulphate will be obtained from solutions containing p)reof copper is dlropped into an acid solution, it cisely the same proportion of acid, in case they neutralizes the free acid just as any other al- happen to be more or less highly charged with kaline liquid would, but at the moment when ammonium salts. Fresenius (Zeitsch. anclyt. all the acid is saturated the liquid suddenly Chem., 1. 108), on the other hand, while a(lbecomes turbid from the deposition of a quan- mitting the justice of Lea's criticism, has shown tity of basic sulphate of copper. Though by experiments that the errors likely to arise readily soluble in ammonia water and in acids, from this source are not of sufficient magnitude this sulphate is well nigh insoluble in neutral to condemn the process, in so far as relates to solutions. Hence that portion of it which was its applications for technical purposes. held dissolved in the final drop of' the test It is to be observed that the acid solutions to liquor falls down when the anmmonia is taken be tested in this way must be clear; they should fioln it. Moreover, the last drop of the test be placed in beakers set upon black paper. liquor reacts not upon free acid, but upon sul- Since the copper solution is liable to lose am ACIDIMETIRY. 11 monia by standing, its strength should be re- manner described under Acetic Acid. It is to determined from time to time, or before each be observed, however, that in determining the new series of experiments. point of saturation with litmus pape, a little The Actual Deterrinalion of the 1proportion of more alkali will anlmost always be used than Acid may be performed as follows:-Weigh out would be the case if the litmus were in soluin-a small beaker or flask as much of the acid to tion. In very delicate experiments it may be tested as will probably be sufficient to neu- sometimes be worth while to determine the tralize from 15 to 30 c. c. of the standard amount of' this excess, and to allow for it in alkali, and add to it litmus enough to color the estimating the acid. This mlay be done by solution faint red. Fill a burette with the measuring off a volume of water equal to that standard soda solution, and drop the latter of the acid tested, and adding to it drops of rather quickly and without intermission into the soda solution until the reaction of the the acid, until the whole o0 the liquid in the liquid upon litmus paper is just as strong as beaker remains distinctly blue for some sec- that previously exhibited by the liquid, which onds. The acid must be stirred continually contained the acid. The quantity of alkali from first to last. After the point of neutrali- required to efftect this result is then subtracted zation has once been reached, no attention from the quantity actually employed in neuneed be paid to the gradual reversion of the tralizing the acid. blue color to violet, caused by the action of See Alkalimetry for the method of using carbonic acid fromn the air. - Note the cochineal instead of litmus. See also Cochiquantity of standard soda solution which has neal and Logwood. been consumed, and proceed to calculate the Estimation of Combined Acids. Though the proportion of acid. Suppose 4.5 grms. of dilute term acidimuetry is commonly understood to acetic acid were weighed out, and that 25 c. c. apply only to the estimation of free acids in of normal soda solution, containing 40 grms. simple solutions, or in solutions charged with ( one molecule) of hydrate of sodium to the substances having no action on alkalies, the litre, were required to neutralize the acid, then process may nevertheless be extendied in some the proportion instances to the determination of acids com0 2: Molecular] x [1- W eight of CI4O02-1 bined with metals. - A description of one Wt O~f C21021. in sample tken. -I method of this character, as applied to the will indicate how many grammes of pure acetic estimation of acetic acid when combined with acid were contained in the weighed quantity of copper, iron, and other metals precipitable as dilute acid, and the proportion hydrates, oxides or carbonates, by caustic or carbonated soda, has been given already under 4.5;1.6 = 1600: xI-~ L33.833w] Acetic Acid. will give the percentage of pure acid which the Another general method of determining the sample contained. amount of acid in a compound-based upon If the acid solution be kept hot while the the insolubility of various metallic sulphidesstandard soda solution is added to it, the point should here be mentioned. This method is of saturation can be distinguished without applicable to the estimation of non-volatile difficulty, even when the soda solution is con- acids, which are not acted upon by sulphutaminated with some carbonic acid; but in cases retted hydrogen when combined, to form coimwhere the operation has to be performed in pounds soluble in water, with any metal which the cold, as when the acid under examination can be easily and completely precipitated by is volatile, or mixed with amlnonium salts, the sulphuretted hydrogen. The process is as folcaustic soda employed should be flee, or nearly lows:-Weigh out a quantity of the salt to be free from carbonate. No matter how pure the analyzed, dissolve it in water, boil the solution, soda, the change of coloration is more readily and pass a stream of sulphuretted hydrogen recognized in hot than in cold solutions. In through the liquid until the metal is completely any event the change of color of the litmus precipitated. In order to determine when the from red to blue is less clearly defined with precipitation is complete, take out drops of the weak acids, such as most of the organic acids, clear liquid from time to time upon a glass rod, than with strong acids, such as sulphuric, chlor- place them upon porcelain, and add a drop of hydric, nitric, and the like. The blue tint, strong sulphuretted hydrogen water, or of any indicative of the point of saturation, may be other reagent specially adapted for testing the obscured also, or modified, by the presence of metal in question. When quantities of salts various substances. If the acid solution con- as large as 5 grammes are operated upon the tains ammonium salts, for example, the change precipitation is usually complete in half an of color from red to blue is less quick and hour. When all the metal has been thrown decided than when they are absent. In all down, filter the liquid rapidly, wash the precipcases of doubt, and particularly when a color itate with hot water until the washings no peculiar to the liquid obscures the color of the longer exhibit an acid reaction, and collect the dissolved litmus, it is best to determine the filtrate and wash water ill a half litre or a litre point of neutralization by placing successive flask. Cool the liquid and dilute it with water drops of the liquid upon litmus paper, in the to the volume of half a litre, or a litre. Agi 12 ACONITIN. tate the mixture thoroughly, take out with a highly colored that the ordinary inethod of pipette several portions of 50 or 100 c. c. each, acidimetry cannot be applied to them. and place theml in separate beakers, adld a few Aconitin. drops of cochineal or logwood to each of' the See loIdomercurate of Aconitin. solutions, and determline the ainmount of firee A I b U MI n acid in each with dilute standard alkali in the Prliincile 1. Coagulability by heat. usual way. As the standard alkali, Gibbs em- Apfplic/caions. Estimlation of.albumin in atploys one-tenth normal ammollonia water. The kaline solutions, suhI as urine and the serum results of the 1st determination should be re- of' blood. garded as merely approximative, and the mean 3llethod A. Acidulate the solution slightly of the 2d and 3d (or of several successive) with acetic acid and boil for several minutes. determinations taken as the true result. From Collect the precipitate on a tared filter, wash the quantity of standard alkali used, not only thoroughly with warin rwater andl dry in a curthe quantity of acid in the salt examined, but, rent of warm air at 110~ or 115~, or better, in in many cases, that of the metal also, may be vacuo, over sull)hullic aci(, until thei mllass readily calculated. ceases to lose weight. Care tmust jbe taken The precipitation of a metal bysulphuretted that the precipitate is thoroughly ldried, for as 1hydrogen from boiling solutions is usually soon as the mioistu1.re has been driiveie fi'on its comparatively slow, but the boiling is never- surface the mass acquires the consistence of theless necessary in order that the filtered horn, and forcibly retains the last poirtions of liquid may contain no sulphydric acid. - In the water. Tlle addition of acetic acid to tlhe,operating upon nitrates and chlorides, a quan- liquid is essential in order that; the albumin tity of some neutral salt of a fixed organic shall be precipitatemd comil)letely-: but no great:acid must be added to the solution before pass- excess of the acid should ble eillploed lest ing the sulphuretted hydrogen. A quantity of sonicme of the albuini be dissolved by it. The the organic acid equivalent to that of the nlin- precipitate thrown d(owvn firon solutions thus,eral acid is then set free, so that none of the acidulated is more fiocculent anld less apt to nlineral acid is lost through volatilization, and clog the pores of the filter during the lrocess none of the nitric acid destroyed by the hot of washing than that obtainled without the.sulphuretted hydrogen. A quantity of Ro- addition of an acid. - To determine albuchelle salt about equal to the quantity of the mrin in urine, place 50 to 100 c. c. of' the clear salt taken to be analyzed, may be used for this urine, previously filtered, if need be, in a flask purpose. large enough to hold twice as much of the The process is inapplicable in presence even liquid. Heat the liquor gradually, with fie-,of very small quantities of iron, aluminuml, quent shakino until the albumin begins to and various other metals, which, with cochi- coagulate, at about 700, then throw a couple neal and logwood, give reactions not easily to of drops of' acetic acid into the flask frolll tle be distinguished from those produced by the end of'a glass rod, and boil the liquor as above caustic alkalies. (Rose, Pogy. Annal., 116. described (Neubauer & Vogel). 125; Gibbs, Amer. Journ. Sci., 1867 [2] 44. 3ilethod B. Another method of estimating 207). albumin in urine, devised by Ileller (Hellcr's Principle IT. Power of acids to expel car- ArchivcJfi Cheio. und l licrosc., 1852, p. 266 bonic acid from metallic carbonates. et seq.), is said to aff'ord very accurate results M3Iethod. Aix a weighed or measured quan- in spite of being indirect:-Evaporate 10 or tity of the acid to be examined with an excess 15 grins. of the urine to dryness over sulphuric of bicarbonate of sodium in an appropriate acid, and weigh the residue. Weigh out anapparatus (see Carbonic Acid), and determine other quantity of the samle urine in a small how much carbonic acid is expelled, either by flask, acidulate it slightly with acetic acid, boil weighing the apparatus before and after the until all the albumin is precipitated, and after experiment, and calling the loss of weight car- the liquid has becoime cold place the flask upon bonic acid, or by absorbing the gas in soda- the balance and add to it, drop by drop, water lime and weighing it directly. (See Carbonic enough to replace what has evaporated. FilAcid). The amount of free acid in the sam- ter thie contents of the flmask and evaporate a ple tested is then found by the proportion: weighed portion of the filtrate to dryness over Molecular wt. Equivalent wt. Weight of CO Weight of acid sulphuriC acitl. The diffesrence between the of 2CO2 of uacid tested. found: in sample. percemntage of residue left by the original urine It will be observed that 2 molecules of CO2 and that obtained fiom the urine after -the are set free for every equivalent of acid in the separation of' the albumin gives the proportion solution:- of' the latter ingredient. Na2O, H20, 2CO2 + I52N206 - Na20, Ni2Ot + 2H20 +- 2CO2. et C. For comaring te quantities of albumin in any two dliffeient samples of urine, Enough acid should be taken to set free one or Dr. John Hjarley has adopted tile fbllowing two gramnmes of carbonic acid. - The pro- process: —iake 3 small filters froui the satme cess affords satisfactory results, and may be sheet of' palper, cut down the two heavier to employed with advantage in testing liquids so the weight of' the lightest, and mark the filters n Zo C~~~~~~~~~~~~~o ALNUIMIN. 13 with a pencil, A, B, and O. Take 1000 grain trough, and cement mr Into the ends of measures of urine A, and having boiled it, pour the trough with Canada balsam, taking care to it while hot upon filter A. Treat urine B in place the glasses parallel to one another, and a sinilar way. Wash the contents of each to leave a clear distance of 6.5 c. m. beof the filters with warm water until the last tween them. The glasses can be cemented traces of adhering urine have been removed. the more readily in case a notch or groove Then pour upon the albuminr an ounce of wan be made upon the iron in the beginning ter containing 2 drops of nitric acid, and sub- to receive them. The metal of the trough sequently wash out the acid with water. The should be painted with, asphaltum varnish to filter marked O is placed in the first instance protect it from rust. between one of the other filters and the funnelj As applied to the estimation of albumin in and is thus equally saturated with urine and urine, the process of testing is as follows:acid, anl equally washed free from both. All 3 Filter the urine, in case it is not clear, acidufilters are dried together, and the empty filter late it slightly with acetic acid, if it be not alis used as a counterpoise in determining the ready acid, and proceed to determine how weight of the albumin upon the others. much the urine nmust be diluted to fit it for the Prolperties. Albumin, as it occurs in the test. To this end prepare several dilute solustate of solution in the animal economy, is tions by mixing measured portions of the urine combined not only with water but with minute with water and boil each of the solutions in quantities of certain saline and alkaline in- regular order, until one is found in whieh the gredlients. When a solution of pure albumin albumin no longer separates in distinct flocks, is evaporated in vacuo, at temperatures below but only as a milky cloud. It is a liquid thus 500, there is left a light yellow, translucent clouded by the presence of fine particles of mass of soluble albumin, which may be read- suspended albumin, which admits of being subily rubbed to a fine white powlver. When jected to the test of opacity. - The best treated with water, this residue s'wells up to a way of preparing these dilute solutions is the jelly, without, however, dissolving to any very following: —By means of a little pipette gradiconsiderable extent, unless a small quantity uated to 0.1 c. c., take up 6 c. c. of the urine of an alkaline salt be present. By the action and transfer it to a 100 c. c. flask. Fill the of most mineral acids, and of many other flask with water to the mark, shake tie mix-. chemical agents-sometimies by mere contact ture thoroughly, pour the liquid into a beaker with atmospheric air, this soluble modification and leave the flask inverted in order that it of albumin is changed to the coagulated, in- may drain.:Meanwhile pour 6 or 8 c. c. of soluble condition. the diluted urine into a test tube of 20 or 25 Insoluble albumin, when recently precipi- c. c. capacity, heat the liquid to boiling, and tated and still moist, is a toutgh, white, opaque, afterwards cool it quickly by immersing the flocculent solid, insoluble in water, alcohol, tube in cold water. In case the precipitate ether, and most acids when dilute and cold. produced( by boiling is so slight that the form. When left moist in the air it putrefies. It is of objects placed in strong daylight can be somewhat soluble in hot acetic, tartaric, phos- (listiuguished on looking at them through thephoric, and strong chlorhydrie acids. When liquid, the sample has been too much diluted, boiled for a long time with water it decomposes and the operator will at once proceed to pre-. and dissolves. On being dried it assumes a pare a more concentrated solution by mixing yellow color and becomes brittle and'translu- 12 c. c, of the ori(inal urine with water in the cent like horn. When soaked in water, after 100 c. c. flask. But in case the first solution drying, it takes up ahlout five times its weight was not transparent, it may be tested in the of the liquid and becomes soft and elastic. trough. - In testing, fill the trough twoPrinciple II. Opacity. thirds full of the cold, boiled liquid, and look Applications. Estimation of albumin in through the liquid( at the flame of a burning aqueous and saline solutions. candlle in a dlarkened room. Repeat the exJfethod. Prepare a little trough of sheet periment with other diluted samples of the iron with glass ends, as follows:-Provide urine until a point is reached where the shape three rectangular sheets of metal, one 7 c. m. of the flame cannot be distinguished, and only square, the others 4 c. m. long by 2.5 c. m. diffused light can be seen throuogh the liquid, wide. Bend the square sheet into the form of even when the candle is brought close to the a V-shaped gutter, the upper edges of which trough. -- In case the flame is visible are 1 c. m. apart. From each of the smaller through the first solution, the next trial must sheets cut out wedged-shaped pieces of metal, be made with a solution containing a few more corresponding to the shape of the trough, so per cents of urine than the first. But if the that when the sheets are placed in an upright shape of the flanle cannot be distinguished, position, the V-shaped trough may fit into the the liquor of the subsequent trial must be more cuts and be supported as by feet. Place one dilute, and so on methodically, until a liquid is of these supports near each end of the trough obtained, through which the red(lish yellow andl solder themn to the trough. Cut out two cone of' flame can only be seen by lo(king with V-shaped pieces of window glass, fitted to the the strictest attention, as if it were in a thick 14 ALBUMIN. fog. When this point is reached it is only with much water. Some samples of albuminnecessary to add a trace more urine (0.1 or.ous urine, however, become cloudy when 0.2 per cent) in preparing the next diluted treated with a few drops of acetic acid, or sample, in order that the flame may become with 5 or 10 times their volume of pure water, completely invisible, and the operation be fin- and it is precisely this kind of urine which is ished. - To find the percentage of albumin, least readily tested by the optical method. divide the number 2.3553 by the number of Special care must be exercised in adding acid c. c. of urine taken to prepare the dilute solu- to such urine, since the presence of a trace tion through which the flame could no longer of acetic acid in excess may present the apbe seen. This number, 2.3553, is the mean of pearance of any precipitate on boiling. The 35 experiments by Dragendorff, in which the cloudy solution (paralbumiin) produced on results of the optical test were controlled by mixing the urine with water, need not be filprecipitating and weighing the albumin. tered. The mixture should be boiled at once, Precaution&s. In looking at the flame, the as if it were clear. - The process is easy trough should be held before the eye like a of execution, and is said to yield very accurate spy-glass, and moved forwards and backwards results, excepting perhaps those kinds of' urine from a distance of 0.5 metre from the candle which become cloudy on the addition of acetic close up to the flame, while the instrument acid. Ordinarily no more than 5 or 6 of the itself is continually pressed lightly against the diluted samples of' liquid have to be tested in eyebrow. Up to a certain point the last order to hit the point of obscuration, so that glimpses of the cone of flame can be seen more the determination will be finished in the course readily, in proportion as the trough is closer to of half an hour. - The several experiments the candle, but if the ilame is too near the of the series above mentioned agreed with one liquid, the latter is illuminated by a reddish another in most instances to the second deciyellow light, through which the flame is seen mnal place. Only 3 experiments out of the 35 less readily. The chamber in which the opera- differed more than 0.1, and only 11 more than tion is conducted, should always be dark 0,05, so that 21 of the trials agreed to 0.05 per enough that the yellow light of the candle may cent. (A.lfied Vogel, Zeitsch. analyt. Clhez., overpower the d(laylight. 1868, 7. 152). In case albumin separates from a diluted Principle III. Power of rotating the plane liquor in small flocks, the liquor may often be of vibration of a ray of polarized light. made cloudy and fit to be tested by shaking it Applications. Estimation of albumin in violently as soon as the flocks appear. Densely aqueous or saline solutions, such as urine and clouded liquids, on the other hand, may be the serum of blood. used for preliminary, approximative tests, by 3Method. When a ray of polarized light is mixing them with measured quantities of wa- made to pass through a column of albumin ter. But the results of such experiments must solution enclosed in a tube, it is found that the always be controlled by testing samples of plane of polarization is rotated to the left, and.urine which have been diluted before boiling. that the angle of deviation is proportional to Better results can always be obtained by boil- the length of the column of liquid. In like ing weak solutions of albumin than by boiling manner, when a tube of any given length is comparatively strong solutions and mixing the successively filled with solutions containing cloudy liquor with water, - Instead of' the diffirent quantities of albumin, the angle of 100 c. c. flask above prescribed, a 50 c. c. flask deviatiom is found to be proportional to the may be used, but rather more accurate results amount of albumin in the liquid. can be obtained when the larger volume of An apparatus, known as Soleil's Albuminimnliquid is operated upon. The pipette employed eter, used for measuring the rotatory power of must be graduated to 0.1 c. c., so that quanti- albumin, resembles ttheordinary Saccharimeter ties of liquid as small as 0.05 can be measured (see Sugar), with the exception that in place with it, of the Nichol's prism there used as the anThe chief difficulty of the process is found alyzer, a double refracting prism is employed, in endeavoring to properly acidulate the orig- cut in such manner that only a single image inal urine. Many samples of albuminous urine shall appear in the field of vision. An intense yield no precipitate, or only a comparatively white light, such, for example, as that of a feeble precipitate on boiling, when too strongly petroleum lamp, is needed. The lamp is placed acidulated with acetic acid, and, in like man- in a blackened box provided with a reflector ner, less albumin is obtained by the optical which throws the rays of light, upon a movetest than by the method of precipitation, in able lens by which they are concentrated before case the acid reaction of the urine is indistinct, reaching the apparatus. It is important that the urine should be kept After the lamp has been lighted and placed in a cool place in order that it may be as firesh in front of the apparatus, put a piece of red as possible when tested. - The original glass in fiont of the polarizing prism in the urine need not be filtered unless it contains a path of' the luminous rays, and turn the andistinct precipitate. Urine that is merely alyzing prism until the luminous image has cloudy will usually become clear when mixed completely disappeared. The zero point of ALCHOLt. 5 the apparatus having thus been determined, of 13 experiments, the least error was 0.005, fill the tube with the solution to be tested, and the greatest 0.056. (Lang, and Itaebler, place it in the apparatus and leave the liquid Zeitsch. awely. Chem., 1868, 7. pp. 513, 514). at rest during sane minutes. On again look- An article on the estimation of albumin, by ing into the apparatus it will be seen that by gramiminetric and volumetric methods, has been virtue of the rotatory power of the liquid in the published by C. Boedeker, in IHenle d' P'feutube, the luminous ray has again become visi- fer's Zeitschrift fiir rationelle MJedicin, Zuzich, ble, and it will be found that the index of the 1859, 5. 320. apparatus must be turned through a certain AlCohol. number of degrees in order to again extinguish Principle 1. Solvent power. the ray. But by counting the number of dle- Applicalions. Alcohol is used for separating grees and minutes between the two points of many substances which dissolve in it from extinction, it is easy to determine the amount others which are insoluble, as when chloride of of the rotation and to estimate therefrom the strontium is removed from chloride of bariumn; proportion of albumin in the liquor. - It is or precipitates, such as the sulphate or malate important to exclude external light as com- of calcium, are washed clean by means of it. pletely as possible; to snake several observa- Two kinds of alcohol are commonly used in tions with each sample of liquid, and to read analysis, namely; " Spirit," or ordinary alcothe divisions of the circle and.vernier care- hol of 0.83 or 0.84 specific gravity (= 88 or fully; best with a good lens. 90 per cent by volume), and "Absolute AlcoIn case serum of blood is to be tested, about hol." The latter should be at least as strong 1 grin. of sulphate of sodium should be added as 0.81 specific gravity (= 96 or 97 per cent to each 100 grins. of the liquid, and the mix- by volume). To prepare it nmix a quantity of ture filtered immediately, in order to separate ordinary alcohol in a capacious flask or retort, blood globules and other suspended particles. with something more than its own volume of The purpose of the sulphate is merely to facil- quick-lime, in small pieces. After the limen itate the filtration; in the case of urine none has slaked, leave the mixture to itself for sevof it need be added. The yellowish ora1nge eral hours, and finally distil it slowly upon a color exhibited by serum when viewed in thin water-bath. layers, becomes distinctly red when seen in a Principle I. Reducing power. long column like that in the tube of the albu- Applications. Reduction of chromic acid to minimeter. In general, however, this colora- sesquioxide of chromium, of binoxide to protion is not intense enough to do any harm; it toxide of lead, etc. simply obviates the need of using the red glass, MIethod. See, for example, Hydrate of for, like the latter, it only permits the passage Chromium. of red rays..Principle II. Volatility. In a series of 50 experiments upon blood Applications. Separation of alcohol from serum, Becquerel found that the deviation of aqueous solutions of non-volatile substances, the plane of polarization varied between 40 30' as a prelinllinary to the determination of the and 9~, or on the average 70 30'. In general, strength of wines and spirit. the deviation oscillated between 70 and 8~. Mlethod. As will appear from the article AlThe corresponding quantities of pure dry al- coholomletry, the value of spirits is usually bumin were from 4.86 to 9.44 per cent. From determined by means of the Hydrometer. these and like observations, it has been calcu- But since this instrument cannot be employed lated that with a column of liquid 20 c. m. in case the spirit contain other soluble sublong, each minute of deviation corresponds to stances besides water, the alcohol, together 0.18 grin. of albumin. (Becquerel, in Robin - with a part of the water, is first separated by Verdeil's Chimie A'natomique, 1853, 3. 316). distillation before the hydrometer is applied. Principle IV. Specific Gravity. A measured volume of the liquid to be Applications. Estimation of albumin in urine. tested is placed in a glass flask provided with Method. Take the specific gravity of the a cork and delivery tube, connected with a urine and note the temperature of the liquid worm, or with a Liebig's condenser. Most of when the observation is made. Acidulate a the liquid is then distilled over, the distillate quantity of the urine with acetic acid, place carefully measured, and the proportion of althe liquid in a flask provided with a perforated cohol contained in it is determined with the cork carrying a vertical glass tube, and boil it hydrometer. The amount of alcohol thus until all the albumin has separated in the in- found must of course be referred to the volume soluble state. Cool the boiled urine to the of liquid originally placed in the flask or still. temperature at which the specific gravity of Both the liquid to be distilled and the disthe original urine was determined, and take tillate must be brought to some common temthe specific gravity of the clear filtrate. Mul- perature before measuring, best by immersing tiply the lifference between the two specific the vessels which contain themn in flowing gravities by 210, iri order to obtain the per- water. The joints of the distillatory apparacentage of albumin in the sample. In a series tus must be tigltly fitted. In case the sub 16 ALCOHOLOM EtRYT, stance to be tested contains any free acetic In case the liquor contains no cane sugar, acid or other volatile acid, neutralize it with but only grape sugar, the number 1.39 (caustic soda before distilling. specific gravity of grape sugar) must be substiAlcoholometry." tuted for 1.606 in the formulla. A term appliedl to methods of estimating the A prominent advantage of the process is proportion of alcohol in any spirituous liquid. found in tile fact that only a comparatively Mlethod A. By Specific Gravity. See Spe- small quantity of liquid is required for an excific Gravity and Hydrometer. Compare what periment. is said of specific gravity under Acidllmetry. 3lethod B. By determiniug the boiling point ApplicatioSs. Determination of the pro- of the mixture, and comparing the result with portion of alcohol in any mixture of alcohol the results of previous experiments made with and pure water. This method is convenient, standard liquids of known composition specially accurate and rapidly executed. It is far more prepared by mixing pure alcohol and pure wafrequently employed than either of the other ter. Tables of the relations of boiling points methods of testing alcohol. It would always to per cents of alcohol will be found in most be employed for practical purposes, were it not dictionariies of general chemistry. (See, for that the presence of sugar, salts, coloring examiple, Dictionary Solubilities, Art. Alcohol). matters, etc., in spirit, sometimes precludes its Applicationis. Determination of the proporuse. tion of alcohol in mixtures of alcohol anti To estimate alcohol by this method, even in water, and in fermented liquors as well. For presence of sugar, Zenneck, and after him mixtures of' alcohol and pure water the method Aug. Vogel, Zeitsch. analyt. Chem., 6, 273, is inferior to Method A (by specific gravity). proceeds as follows:-Carefully determine, in It finds useful application, however, in testing the first place, the specific gravity of the sac- wines and beers, since it has been found that charine spirit at 15~ upon a balance. Then the foreign substances, other than alcohol and weigh out about 150 c. c. of the liquor in a water, in fermented liquors, have little influtared fisk, and boil to expel alcohol, until ence upon the boiling point of the mixed about half of the liquid has evaporated. Re- alcohol and water. Enough sugar or common move the flask fiom the lamp, place it upon a salt may be added to spirit of 20 per cent, by balance, and pour in water until the weight of volume, to reduce the liquor to 0~ of' Gaythe flask and contents is the same as before Lussac's alcoholometer without altering the boiling. Cool the aqueous solution of sugar to boiling point of the spirit to any appreciable 150, and determine its specific gravity. Look extent. Several forms of Ebullioscopes have up in the published tables (Diet. Sols., Art. been invented for testingu wine and beer. For Sugar) the percentage of' Sugar, S, which a report upon the various forms of this instrucorresponds to the observed specific gravity; ment, see Despretz and others, Comnptes lenz100-S (=-=A) will then represent the percent- dus, 27. 374. A recent form of ebullioscope, age of mixed water and alcohol in the liquor by Brossard-Vidal, is described in Zeitsch. under examination. The specific gravity of analyt. Cheom., 1864, 3. 223. Wagner, in his this plain spirit may be found by the formula: Jahresbericht chem. Tech. 1863, 9. 545, spe1.6,05 X D x A cially comme nds the ebullioscope of' Tabari6. x = - 10.-J X S 7, Ebullioscopes are much used for testing wine andl beer, and the results obtained by thelm in which D - the specific gravity of the origi- oll beer, and the results obtained by thet compare very favorably with those obtained nal mixturei of sugtar aln spirit. ilen the by the method of distillation. (See -under specific koravity of the plain spirit is knon, it Alcohol).- In boiling beer it is well to is easy to obtain its percentage composition by add to the liquic a trace of tannic acid to prereftrring to the published tables (Dict. Sols., velt frotlino'. Art. Alcohol), and from the composition of etho C By dereriilng the Telsiol of the plain spirit, that of the original saccharine the Vo1odo. An instrument called a Vaporileliquor may be easily calculatedl. The ter has been constructed by Geissler tor this frnmula above given is obtained as follows:' Tfhrnella abosp e ic vcn gv S obtane as follob s:en purpose. It consists of a vessel provided with Thle specific gravith of cane sa gar beinge 1.606, a syphon tube, fitted by grinding to an orifice an~d that of tlle orijnal sacchaine licluaor D, at its top. It is employed as follows: —Metallic let x represent the specific gravity of the plain mercluy is poured into the vessel up to a cerspirit. The volume of the plain spirit will be tm mlark, anl the space above thle mlptecury antd that of' the percentage of sugar ls,(; filled with the spirit to be tested; the syphon hence tube is then put in place, and the whole apSp. r. of the mixture:D = 100(A + S ) paratus turned upside down. The quicksilver ancid X Wt6 immediately falls into the bent tube and closes 1.i6(x x x A the spirit against contact with the air. The * lt).s; - a X S. apparatus is then placed in an atmosphere of steam, in the upper part,of a vessel in which 1 For the details of Alcoholornetry, see iatncma erter,letch der Chemic, l-raunlschlwelig, 1856. 1.49. wat eis bol i, so that vapor ma e evolve any of the large Dictionaries of (lChenistrv. from the spirit. The pressuLre exerted by the ALKALIMETRY. 17 alcohol vapor, forces a portion of the mercury the tube with the published tables, in order to to rise into the syphon tube, and from the obtain the percentage of alcohol. (Reynolds, height of this columln of mercury, corrected for Lo:znon Pharm. Journ. and Trans., [2.] 9. 171, the atmosplheric pressure at the moment of and Zeits.ch. calzolyt. Chemr., 186;8, 7. 358). observation, the tension of the vapor is deter- r3lethod F. Biy Ultinate Ana l;ysis. A weiglhed mined. The apparatus is usually provided portion of any mixture of alcohol and pure with an empirical scale, which indicates the water could be burned by means of an oxidizproportion of spirit in terms of per cent by ing agent (see Carbon), the resulting carbonic volumne. acid weighed, and the quantity of alcohol Apiplications. Determination of the propeor- comnputed from these data. But the method tion of alcohol in solutions charged with sugar. w-ould only be of scientific interest. It has no It has been found that with solutions contain- practical application. ing salts, such as chloride of sodium, the Alkalmetry. tension of the vapor evolved at any given A ternm applied to the estimation of free temperature is greater than it would be for a alkalies and alkaline carbonates. mixture of alcohol and pure water. But suTgar M3/ethod A. By Specific Gravity. In pure exerts no influence. In case the saccharine or nearly pure solutions of ammionia, or of the spirit to be tested contains carbonic acid, or hydrates of sodium and potassium, the proporany other volatile acid, the liquid must be tion of alkali may be inferred with folerable saturated with lime before placing it in tire accuracy firom the specific gravity of the soluvaporimeter. The method is of' course one of tion. (See Acidiunetry). But the method is of technical, rather than of scientific, application. less general applicability with alkalies than lMethod D. By Determinzing the Rate of with acids, since, with the exception of amExpan sioln of the Liquid by Heat. Instruments maonia-water, alkaline solutions are rarely found have been constructed for this purpose by pure. Silbermann (Coiptes RerTdus, 27. 418) and lletlhod B. By neutralization with an acid by Makins (Jourznal of Chenzical Soc., London, solutioln of (etermlined strength. This mnethod 2. 224). Silbermann's Dilatometer consists of is the precise opposite of the method of Acida thermometer tube, which is filled up to a imetry by saturation, already described. It certain mark with the spirit to be tested, at consists in deternining how much acid of the telnperature of 250. The air which the known strength is required to neutralize a liquid holds dissolved is then removed by means definite weight of the sample of alkali under of an air pump, and the tube and spirit finally examination. exposed to a temperature of 50~. The amount The chief requisite in this process is of course of expansion is observed, and the proportion the stacndard or test acid; which may be mnade of alcohol in the sample found by referring to either from sulphuric, oxalic, chl6rhydric or a scale previously graduated by direct obser- nitric acid, according to circumstances. vations upon samples of spirit of known Standard acid may be prepared either by strength. dissolving a definite weight of a crystallized Alpplicctions. The instrument can be used acid, such as oxalic acid, in water, in such with mixtures containing sugar or salt, since manner that each c. c. of the solution shall these substances have been found to exert little contain a certain proportion of the dry acid; or no influence on the expansibility of spirit. or by adding the requisite proportion of wate'r Ml1ethod E. By Capillarry Attraction. The to any moderately dilute solution of sulphuric, instrument known as a Liquometer, in which chlorhydric, or nitric acid, after the proportion the determination is made, consists of a capiil- of real acid in that particular sample has been lary glass tube 4 inches long, graduated to 20 determined by analysis or by titration. The degrees, and fitted to a hole in the cover of a details of the several methods will be given glass vessel so that it can be elevated or de- below. pressed in the vessel. After the glass vessel Standard acid is often made of such strength has been three quarters filled with the spirit to that a litre (= 1000 c. c.) of it shall contain be tested, the capillary tube is pushed down so exactly one equivalent of the dry acid, exthat about 0.1 inch of the lower end of' the pressed in terms of grammes; it is then called tube shall be immersed in the liquid; a quan- " nornmal acid." Thus normal chlorhydric tity of the spirit is drawn up into the tube by acid should contain 36.5 grins. of IHC to the sucking at the upper end to moisten its walls, litre, and normal sulphuric acid 40 grammes and the tube again drawn up carefilly until its of SO3. Equal volumes of different normal lower end is precisely level with the surface of acids have of course the same power of satuthe spirit. Again suck carefully at the top of rating alkalies. Sometimes the test acid is the tube, so that the liquid may rise in the made to contain only a fraction of the quantity tube, and afterwards note the point at which of real acid which would be required if it were the li-Jmid remains stationary when it is allowed normal. Thi' s an acid containing 7.3 arms. to sink bhTc;k towiar(ls the.g-lass vessel. Coin- I IC1 to the litre, is callel I one-fhitoll rnii,"1 aI;re the degree at which the spirit stands in while one that contains 3.65 grinS. is "11one2 18 ALKALIMETRY. tenth normal." Several methods of preparing be discovered by noting how much of this acid standard acids will be set forth in the follow- is required to neutralize a given wei(ght of ing paragraphs. pure carbonate of sodium. The determinlation Standard Sulphuric Acid. may be made either in the manner described A. Norimal Sulphuric Acid. Counterpois ~, or, more accurately, by that set forth in a small flask or beaker with shot or san upon ~ It is to be observed, as a general rule, a rough balance, andl w6eil out in it 60 grrns. that a stand(ard acid is best prepared by the a h c d' it 7 6grn.same method as that for which it is to be subof concentrated sulphuric acid. Put 1050 c. c. of water in a large flask and pour the acid into se(uently used. If sulphuric acid, for exarn the water while shaking the flask. After the ple, s to be used for testing the value of mixture has become cold, pour a part of it commercial carbonate of sodiumn, it shoull be into a burette, measure off into beakers two tnardized against pre carbonate of sodium portions, of about 20 c. c. each, of the liquid, by tile very methodcl which is aftr ds to be and determine the quantity of' sulphuric acid applied in testing the commercial carbonate. in each portion by precipitating it as Sulphate a. Weigh out (best fiom the covered platiof Barium. If the results of these determina nua crucible in which it has been ignited tions are concordant, take the mean of the two from 4.5 to 5 grms. of pure, anhydrous carbonas representing the amount of acid actually ate of sodium. Place the salt in a capacious contained in the Iniixture. Pour the rest of flask or porcelain dish, dissolve it in about 200 the acid solution into a graduated mixi.n c.c of hot water, and color the solution blue cyliner, note its volue and ur in a s mucixing with 1 or 2 c. c. of' a solution of litmus (or, as much instead of litmus, color the cold solution with water as may be required to dilute the liquid Cochineal, or with Logwood) - Mix about to the condition of normal acid (i. e., 40 gris. 60 rins. ofel, ordinary onohdrated sulphuric to the litre)'. If it were found, for example, ai rlnst of orcinary, ronohadrate solpuric that the 20 c. c. of liquid tested contained acid with 500 c. c. of water, allow the solution 0.84 grin. of sulphluric acid, then 1000 c. c. to cool, and fill a burette with the cold dilute would contain 42 grins., and to every 1000 c. c. xture Stir the solution of carboe of of the solution 50 c. c. of water would have to sodium with a fine glass rod, and gradually be added, for pour into it, from the burette, the cold dilute 40: 1000 =42: x(= 1050). acid, until the color of the solution changes to a wine red; then place the flask or dish over a In default of a mixing cylinder, the dilution lamp and heat its contents to boiling. The may be effected in a litre-flask, as follows: — wine red coloration is caused by the action of Fill the flask up to the mark upon its neck carbonic acid which has been set free, and the with the acid mixture to be diluted, so that the liquid is heated in order to drive out this vollower edge of the curved depression at the top atile acid. As soon as the color of the liquid of the liquor shall coincide with the line upon has become blue again pour more sulphuric the glass; empty the liquid carefully into a acid from the burette into the nearly boiling large stoppered bottle; measure off with A liquid, until the solution assumes the peculiar pipette or burette the amount of water re- deep red color, slightly inclined to orange, quired for the dilution; transfer this water to which is characteristic of the strong acids. the flask fiom which the acid has just been Since, in liquids thus charged with carbonic poured; shake the flask thoroughly, and add its aid it is not easy to determine when the opcontents to those of the bottle; shake the bot- eration is finished, if the color of the dissolved tle thoroughly, pour back half its contents into litmus be alone relied upon, litmus paper must the litre-flask, agritate the latter, pour back the be used towards the close of the operation in liquid from the flask into the bottle, again order to detect the precise point of saturation. shake the bottle and keep its contents for use. Hence, after the liquid has become wine red, As is the case with all standard solutions, take care to add the sulphuric acid only by the bottli should always be shaken just before small portions, finally at the rate of only two any portion of' its contents are to be poured drops at once, and after each addition of the out for use, unless indeed it be absolutely full acid draw the point of the stirring rod across a of liquid. For when a bottle is but partly strip of blue litmus paper, one or two inches filled with a solution, some water is apt to wide, so that red streaks may be formed upon evaporate into the space above the liquid and the paper in regular order, and each streak condense there upon the glass in such manner correspond to a fresh addition of the acid. that if a small portion of liquid was to be Proceed in this manner until the color of the poured out of the bottle without shaking, it liquid in the dish indicates that the point of would wash off the condensed water and( be- saturation has been passed, then note the luitncome slightly diluted, while the liquid remain- ber of c. c. of acid which have been pouredl ing in the bottle would be left a trifle stronger from the burette, dry the strip of litmus paper after each pouring. at a rgentle heat, and observe which one of the Instead of' determining the sulphuric acid streaks upon the paper just remains red when by precipitating it as sulphate of barium, the dry. The red color of all those streaks which proportion of acid in the sample chosen may were reddened with carbonic acid will coll ALKALIMETRY. 19 pletely disappear as the paper becomes dry, stant for hours; it is unaffected by the carwhile the reddening due to sulphuric acid will bonic acid of the air. When three or four remain visible; it is an easy matter, therefore, concordant results have been obtained, the to determinie how oreat an excess of' the acid average is taken as expressing the relative has been used, by simply counting the number strength of' the acid and alkali. (Luckow, of red streaks left upon the dry paper. A quarter Journ. prakt. Chem., 84. 424, through Amer. of a cubic centimetre (or whatever two drops Journ. Sci., 1863, 35. 280). may amount to in terms of the burette ecm- M. Mix concentrated sulphuric acid, of ployed) is then to be deducted from the total known specific gravity, with enough water number of c. c. of acid used for every one of that the mixture may contain rather more than the streaks. Besides the sum of these drops one equivalent of the anhydrous acid for every used in excess, it is best to subtract also from 100 parts of liquid. Weigh out 1 to 1.5 grin. the total amount of acid used one quarter of of pure anhydrous carbonate of sodium, place one c. c., which has gone to neutralize the al- it in a flask or porcelain dish of 300 or 400 kali in the litmus emlployed for coloring. c. c. capacity, dissolve it in 100 or 150 c. c. of Repeat the experiment with new, portions water, and pour into the liquid a measured of carbonate of sodium and of' the acid, and quantity a of the cold acid. Take I c. c. of in case the two results agree, proceed to dilute the acid for every 0.0053 grin. of the carbonthe acid to the desired degree in the manner ate, so that the acid may be distinctly in exalready described. cess. Boil the solution to expel the carbonic For some eyes, an infusion of Cochineal acid, then color it slightly red with a measpossesses great advantages over the solution of ured quantity of litmus solution and pour into litmus, as a means of recognizing the point of the hot liquid, from a burette, a dilute solution neutralization. To prepare the liquor, put 3 of caustic soda of undeterimined strength, ungrammes of powdered cochineal in a flask, to- til the last drop of the soda produces a distinct gether with 50 c. c. of strong alcohol and 200 light blue color, unmixed with violet. If' the c. c. of distilled water, cork the flask and let solution is only slightly colored with litmus, the mixture digest for a day or two at the and is free from carbonic acid, it is easy to ordinary temperature, shaking it frequently. determine the point of saturation with great The clear solution, which may be either de- exactitude, otherwise some difficulty is met canted or filtered fiom the residue, has a deep with from the blue tint at first formed changruby-red color. On gradually diluting it with ing to violet. pure water, free from ammonia, it becomes Write down the number of c. c., b, of the orange, and finally yellowish-orange. Caustic soda solution required to neutralize the excess alkalies and alkaline carbonates change the of acid. Then measure out a fresh portion, c color to a carmine or violet carmine, and so (= 20 or 30 c. c.), of the dilute acid, and do the alkaline earths and their carbonates; determine how many c. c., b', of the soda solue solutions of strong acids and acid salts make it tion are required to neutralize it. From this orange or yellowish-orange, but to carbonic last determination it will appear that 1 c. c. of acid it is nearly inditfferent. In using cochi- the soda solution is equivalent to c. c. of the neal, the solution to be tested should not be heated. It is simply necessary to measure out dilute acid. Hence there was employed in the a given volume, say 20 c. c. of the acid, to previous experiment -c cubic celtimnctres nlore dilute it with about 150 c. c. of water, to adde needed to neutralize 10 drops of the cochineal liquor, and to pourutralize in alkali from a burette until tile yellowish ca 0b0053 gril. of carbonate of sodium; or liquor in the flask suddenly acquires a violet- a - cubic centimetres ofthe acid would have carmine tinge through the action of a single precisely neutralized the carbonate of' sodium drop of the alkali. cb taken. Hence, if a -g~ cubic eentimetres of In nicer determinations it is important to taken. Hence, bring the liquid each time to a given volume, the acid be diluted with water to the bulk of a by adding water after the neutralization is cubic centimetres, the solution will be normal. nearly finished. To note the level of the Compare Standard Nitric Acid, below. proper amount of liquid, say 200 c. c., strips Standard sulphuric acid may be prepared of paper may be pasted upon the beakers or also by decomposing a known weight of sulwide-necked flasks employed. phate of copper with sulphydric acid, as proThe same amount of' coloring matter being posed by Gibbs (Aimer. Journ. Sci., 1867, 44. thus always diffused in the same volume of the 210). Put a quantity of' pure powdered sulsame water, errors due to varying degrees of phate of copper in a porcelain crucible placed dilution and varying amounts of ammonia, within a liessian crucible, and heat the sulWvhich is rarely absent from distilled water, are phate for about an hour, taking care to raise avoided. The contents of' one flask, in which the temperature gradually, and that the heat the neutralization has been satisfictorily ef- shall at no time exceed low redness. Transfer fected, may be kept as a standard of color for the hot anhydrous sulphate to a dry weighing the suceeding trials. The tint remains con- tube, close the tube, and after it has become 20 ALKALIMETRY. cold weigh out a quantity of the sulphate. as will be described directly under Standard Dissolve the weighed sulphate in water, heat Nitric Acid. the solution to boiling, pass a stream of sul- Standard Oxalic Acid. Weioh out 63 tirs. phuretted hydrogen through it to precipitate (the weight of one equiv.) of crystallized oxalic the copper (see Acidimetry), and dilute the acicd, transfer it to a litre flask, a(.h!l -water filtrate and wash water to a known volume. enough to nearly fill the flask, shake the umixThe quantity of sulphuric acid in the solution ture until the acid has all dissolved, bring the is known from the weight of the anhydrous liquid to the temperature of 160, and pour in sulphate taken. water up to the litre mark; again shake tlhe solution thoroughly, then pour it into a stopFor technical determinations it is convenient pered bottle and keep it plrotected f~rom sunto make the standard acid of such strength that light. Since the oxalic acid found in com50 c. c. of it will exactly neutralize 5 grnlS. of merce is usually contaminated wi-th potasslumn, pure carbonate of sodium. Such acid may be it is best to prepare a pure acid directly by used for testing the value of either of the acting upon starch with nitric acid, and recaustic or carbonated alkalies; and the number crystallizing the product. (See Oxalic Acid). of half' c. c. of it required to produce satura- Standard NAitric Acid may be readily pretion, in any particular case, will correspond pared by the method described above in ~ y directly to the per cent of alkaline carbonate under the head of standard sulphurio acid. or caustic alkali contained in the sample tested, Instead of carbonate of sodiumn, carbonate of provided there be weighed out for the analysis calcium may be employed. It has the advana quantity of material equivalent to 5 grins. tage of being more readily obtained in a state of carbonate of sodium. The equivalent of purity than carbonate of sodium. An outquantities capable of saturating 50 c. c. of line of the process mayhere be re-stated:this standard acid are respectively:- Prepare a (quantity of' dilute nitric acid, in For Carbonate of Sodium....s 5.00 grins. such wise that the strength of this acid, as inid Hydrate " i.... 8.773" dicated by the hydrometer, shall be somewhat, Carbonate of Potassium... 6.519" greater than that of the desired standardl acid. in Hydrate 6. *. 5.12092 6 _Prepare also a solution of caustic soda, about If 5 grms. of an impure carbonate of sodium, as strong as the acid, and deternle by titraor 6.519 grms. of common pearlash be weighed tion how many c. c. of this soda solution are out and titrated with the acid in question, the required to neutralize a measured quantity of number of half c. c. used will in the one case the acid. WVeigh out about 1 grin, of pure give the per cent of pure carbonate of sodium, carbonate of calcium (either powdered Iceland and in the other of pure carbonate of potas- spar or the precipitated carbonate) which has sium, which the samples contain, without need been dried at 1000, and dissolve it in a mleasof any calculation. Where substances poor in'ured quantity of the nitric acid Heat the alkali are to be tested, some multiple of the nmixture gently to expel carbonic acid, color it numbers above given may be weighed out. with litmus, and finally pour into the liquid as Standard Chlorhydric Acid. Mix 900 c. c. much of the soda as Is needed to neutralize the of water with 180 c. c. of chlorhydric acid of nitric acid which was used in excess. Note 1.12 specific gravity, measure out with a bu- the quantity of soda solution employed, calcurette two portions of from 10 to 20 c. c., and late therefrom the number of c. c of nitric acid determine the quantity of chlorhydric acid in which were used in excess, and subtract this each portion by precipitation, as Chloride of amount from the total amount of acid taken to Silver. If the two results are concordant, dissolve the carbonate. The remainder will take the mean and calculate therefrom how give the number of c. c. of acid which are much water must be added to the acid tested equivalent to the weighed quantity of' carbonto reduce it to the normal strength. If it were ate of' calcium; in other words, it will indicate found, for example, that 20 c. c. of the acid what portion of the acid was neutralized by the contained 0.81 grm. of HCl, then a litre would calcium salt. The weight of dry acid in this contain 40.5 grms. and portion may now be found by the proportion: Mol. wt. of IIC1 = 36.5:1000:: 40.5: x ( 1111). Equiv. Equiv. Wt. of Wt. of N2O0 in the volume wt. of * wt. of = CaCOs * of liquid neutralized so that 111 c. c. of water would have to be CaC03 *6205 taken by that CaCO3. added to each litre of the acid. The value of the acid having thus been deInstead of determining the amount of chlor- termined, proceed to dilute what remains of it hydric acid by precipitation, as chloride of to the required standard, in the manner alsilver, it may be estimated with carbonate of ready described. (Standard Sulphuric Acid). sodium in the manner described above, under' standard sulphuric acid; but before boiling the In some cases it may be found convenient tcf liquid to expel carbonic acid, a few grammes employ a standard solution of carbonate of of' sulphate of sodium must be added to pr(e- sodium instead of the dry salt. The. stl-tldarl vent the evolution of' chlorhylldric acid. Or it solution s:may b)e prepared with case by silsmply mLay be estimated with carbonate of calcium, dissolving a weighed qluantity of' iuLrC car ALKALIMETRY. 21 bonate of sodium in the required volume of poured upon it from a burette until the alkali water. By using measured portions of this is saturated. (See standard sulphuric acid c). solution the operator has it in his power to Or an excess of the standard acid is added in make several titrations from the product of a the beginning to the weighed sample of alkali, single weighing. Reischauer (Dingler's poly- the nmixture boiled to expel carbonic acid, and tech. dJurn., 167. 47) recommends the use of the excess of the standard acid estimated with a normal solution of the carbonate, made by a standard solution of caustic soda. (See Aciddissolving 53 grinms. of the salt to the volume of imetry and standard sulphuric acid f). a litre. To prepare a standard acid by means The quantity of material to be taken for of this solution, measure off 10 c. c. (= 0.53 analysis in any particular case, may be judged grm.) of it with a pipette, mnix it with an ex- of, fromn what has been said above, under cess of the acid to be standardized, and neu- standard sulplhuric acid. In order to diminish tralize this excess with caustic soda, as above the errors incidental to weighing, it is often described. best, in the lack of a delicate balance, to weigh Jferits oJ the several Acids. Test acid may out a quantity of material ten times as large be prepared more simply and directly from as is really wanted. The weighed substance is oxalic acid than from either of the other coni- then dissolved in half a litre of water, and one mon acids. Oxalic acid may readily be made or two portions of it, each of 50 c. c., are pure and dry, in spite of current assertions to taken out with a pipette for analysis. In case the contrary, and were it not for a certain any portion of the weighed substance refuses tendency to decomposition which is exhibited to dissolve in water, the liquid should be filby aqueous solutions of this acid when exposed tered and the residue washed before proceedto light, they would doubtless be very generally ing to the acid treatment, or better, the liquid employed in processes of alkaliumetry. mnay be allowed to stand until it has become Chlorhydric acid has special maerit, in that clear, and a definite portion of the clear liquor the fundamental determination of the propor- then taken up with a pipette for the analysis. tion of acid in any given sample may be Care must of course be taken, in the first place, made with very great accuracy by precipita- to obtain a fair sample of the material to be tion, as chloride of' sirer, tested by taking small portions of it from imany Sulphuric acid, which is perhaps more fre- parts of the entire mass and rubbing them quently employed than either oxalic or chlor- thoroughly together in a mortar. hydrle acid, has the advantage of being less According to Baugart& Wildenstein (Zeitsch. volatile than the latter, and less liable to analyt. Choei., 1864, 3. 324), it is well, in change than the former. Dilute solutions of technical determinations of the value of alkasulphuric acid may be boiled freely without line carbonates, to check the frothingr, which fear of loss. When standard cllorhydric acid, occurs when acid is added to the liquor, by on the contrary, has to be boiled, it is best to rreans of a layer of melted paraffine. A small mix witl it a quantity of sulphate of sedium quantity of paraffine thrown upon the boiling to hinder the evolution of clflorhydric acid. solution of carbonate of sodium, contained, as In any event, care should be taken both with usual, in a large evaporating, dish, will immnechlorhydric and nitric acids, that only a very diately melt and spread over the entire surface slight excess of acid be present when a liquidc of the liquor, in such manner tlat no permnais to be boiled. Nitric acid has no advantacge nent froth can form upon the surface of the over chlorhydric acid, excepting that it vela- liquid. The titration m.ay consequently be tilizes somewhat less readily than the latter proceeded with without delay or interruption. whern a dilute solution is boiled. A few decigramres of paraffine are sufficient Sulphuric acid is well suited for the estima- for a surface 12 c. m. in diameter. In order tion of sodium, potassium and magnesium, but to reduce the paraffine to convenient shape, cannot be used for determining calcium, ba- cip a not too thin glass rod into a quantity of Aium or strontium; either nitric or clhlorhydric melted paraffine, bring the rod close to the suracid must be eomployed when the oxides, hy- face of a quantity of cold water, and then drates or carbonates of these metals are to be allow the drops of' the hot liquid to fall into titrated. thel: water. Dry the solidified drops on filter Tartaric acid, at one time proposed as a sub- paper andi keep for use; 2 or 3 of theml will stitute for sulphuric acid in alkalimetry, is not be found suflicient for a single alkali deternmwell adapted for use as a standard acid, since ination. aqueous solutions of it are liable to decompose Estimation of the proportion qf Caustic Alon standing. kali and of Alkaline Carbo(nate in mixtures conThe Acttai Determinaustion of the proportier tai,ii9ng both these substances. of alkali in any sample of unknown value, fol- AWY'eigh out from 15 to 20 grons. of the imlows, fomn what has been said above, without pure carbonate to be tested, an(l dissolve it in need of further description. A weighed quan- water in a quarter-litre flask. Wl1hen the solutity of the material to be tested is dissolved in ble portion of the substance has all dissolved, about 200 c. c. of water, the solution is color'ed fiil the ilask with water to tile mark and shake with 1 or 2 c. c. of litmlts, and standard acid is its contents thoroughly. Cork the flask in 22 ALUMINATES. order to exclude the carbonic acid of the air, The process yields tolerably good results, but and allow the liquid to stand until it has be- is less accurate and far less convenient and come clear. Draw off with a pipette two por- expeditious than the method by neutralization tions of the solution, each of 100 c. c., and with a standard acid. It is consequently seldetermine the total amount of alkali in one dom employed in practice. It was at one time portion by titration with a standard acid. somewhat used for determining the proportion This "' total alkali " may be set down either as of alkaline carbonate in mixtures of caustic and carbonate of the alkali, or as caustic alkali, carbonated alkali, after the total alkali value according as one or the other of these ingre- of the sample had been ascertained. The best dients preponderates in the sample under ex- way of determining the total alkali value is by amination. Allow the other 100 c. c. portion titration with a standard acid, either directly of the solution to flow into a quarter-litre flask, or indirectly, as has been already described. add to it 100 c. c. of water and a solution of But in lack of an acid of determined strencth, chloride of barium, as long as a precipitate the total alkali value of any sample of mixed falls. Fill the flask with water to the mark, caustic and carbonated alkali may readily be cork it and leave the mixture at rest, until all determined by the method of expelling cartlhe carbonate of barium has been deposited bonic acid. To this end expose a portion of and the liquid has become clear. Draw off the sample to carbonic acid gas, until all the 100 c. c. of the clear solution, color it with caustic alkali present has been saturated, ignite litmus, add standard chlorhydric acid to dis- to destroy any bicarbonate which may have tinct acid reaction, and note the quantity of been formed, and finally determine the caracid used. Neutralize the excess of acid bonic acid in the manner already described. with a standard solution of caustic soda, and In another portion of the original sample, subtract this excess firom the whole amount which has been subjected to no treatment, of acid taken. The difference will give the except drying, determine the amount of alkaamount of acid which has been neutralized by line carbonate. The difference between the the caustic alkali in the portion of material two determinations will indicate the proportion subjected to analysis, and from the weight of of caustic alkali in the substance analyzed. the acid, that of the alkali equivalent to it may Another method of estimating caustic alkali readily be found by calculation. Finally sub- in presence of an alkaline carbonate, will be tract the weight of caustic alkali thus obtained found above, under Principle I. from the total weight of alkali as found by Each of the processes of alkalimetry above titration in the other portion of the solution, described is liable to error when the substance in order to obtain the amount of alkali which to be tested is contaminated with certain irumust be regarded as a carbonate. purities. The special precautions to be taken According to A. Mueller, the solution to in order to correct or avoid these errors, will which chloride of barium has been added must be described further on, under the heads of the not be filtered. It contains caustic baryta as several alkalies and alkaline carbonates. For well as caustic alkali and alkaline chloride. the methods of estimating potassium in presIt is found that a filter retains some of the ence of sodium, see KC1; 2KC1, PtCl C; KC104; baryta, and that a little of the caustic alkali K2SO4. might thus be lost. Aluminate of Ethylamin. See Another method of estimating caustic alkali Aluminate of Sodium. when mixed with an alkaline carbonate, will Aluminate of Potassium. See be given below, under Principle II. Aluminate of Sodium. Principle IL. Volatility of carbonic acid. Aluminate of Sodium. Applications. Determination of the amount Principle. Solubility in water. of pure alkaline carbonate in saleratus and Applications. Separation of Al from Fe, the other commercial carbonates of sodium and and fiom small quantities of NMn. Also fiorm potassium. Co and Ni (Method B). Method B is speMllethod. A weighed quantity of the alka- cially adapted fbr the treatment of mixtures of line carbonate to be examined is treated with the oxides of iron and aluminum which have an excess of sulphuric acid in an appropriate been ignited, and so rendered insoluble in apparatus (see Carbonic Acid), and the weight caustic lyes. of- the carbonic acid expelled from it is deter- Method A. Evaporate the chlorhydric acid mined either by weighing the apparatus before solution of aluminum, etc., to dryness on a and after the experiment, and calling the loss water bath, in order to remove the excess of carbonic acid, or by absorbing the gas in soda acid. Take up the residue with water, and in lime and weighing it as such. (See Carbonic case the solution is cloudy, add a drop of Acid). From the quantity of carbonic acid strong chlorhydric acid and warm the mixture found, the proportion of alkaline carbonate in upon the water bath to clear it. Pour slowly the sample tested is obtained by calculation:- a quantity of not too dilute soda or potash lye Equiv. Eqliv. wrt. Weight Wt. of NaoCO3 into a porcelain dish, or better, into a large wt. of: of Na2CO o::f Co X= or of K2CO) platinum crucible; lace the dish or CO2 (or of K2CO3) found In the sample. platinum or silver crucible; place the dish or ALUMINATE OF SODIUM. 23 crucible upon a water bath and heat the latter wash the filter with wS -aaand collect to boiling. Stir the hot lye with a stiff plati- the washings in a beaker. Add concentrated num wire, and slowly pour into it the solution soda lye to the liquid in the dish until the exof aluminum, etc. Each particle of the alu- cess of acid is almost neutralized. Heat the minum compound is thus brought into intimate liquid to boiling, remove the lamp and place contact with a large excess of free alkali, and in the dish a lump of hydrate of sodium or is converted into a soluble aluminate of the hydrate of potassium, large enough to dissolve alkali, while the iron is thrown down as a hy- all the aluminum which the mixture contains. drate. When the last portion of the aluminum If the proportion of iron in the mixture be solution has been washed into the dish which small, the precipitate produced by the soda contains the alkali, pour the alkaline mixture will, after a short time, contain little or no upon a filter, wash-the ferric hydrate and pre- aluminum, but only ferric or manganic hydrate. cipitate the aluminum from the filtrate, as Pour the contents of the dish into the beaker Hydrate of Aluminum, by boiling the liquor which contains the rinsings of the filter, and with an excess of chloride of ammonium. wash the dish thoroughly with water. Filter (Laewe, Zeitsch. analyt. Chem., 1865, 4, 357). off the aluminate of sodium from the insoluble After a little experience, the amount of precipitate, wash the latter with boiling water, alkali to be employed may be judged of from dissolve it in chlorhydric acid, and precipitate the quantity of residue left on evaporating the the iron as Hydrate of Iron. Acidulate the chlorhydric acid solution of aluminum, etc. filtrate with chlorhydric acid, and precipitate In most cases, two or three grins. of solid hy- the aluminum as Hydrate of Aluminum. drate of sodium will be enough for a single Since the residual ferric hydrate is liable operation. If the mixture to be analyzed con- to retain 1 or 2 per cent of hydrate of alutains a large proportion of iron, the ferric minum, it must be redissolved in chlorhydric hydrate precipitated by the alkali will retain a acid, and the solution treated with caustic certain amount of alumina. It is best, there- soda, as before, to ensure the complete removal fore, when the amount of ferric hydrate is of the aluminum, unless, indeed, the ferric large, to redissolve the washed precipitate in precipitate is so small that the actual weight chlorhydric acid, to evaporate the chlorhydric of the aluminum contained in it is insignificant. acid solution as before, and to pour the neutral or nearly neutral solution into a new quantity In the foregoing cases the iron is supposed of hot soda lye. This second alkaline solution to be in the form of a ferric salt, but some must of course be added to the first, after fil- chemists prefer to reduce the iron to the contering to separate the ferric hydrate, before dition of a ferrous salt, by means of a solution proceeding to precipitate the aluminum. After of sulphurous acid, or of sulphite of sodiumn, the ferric hydrate has been thoroughly washed before proceeding to separate it from aluminum. with hot water to remove the aluminate of Their method is as follows: —Heat the tolerasodium, it must be again washed with a hot, bly concentrated, acid solution of aluminum, but not too strong, solution of chloride of am- etc., to boiling, in a flask or capacious dish, monium, to remove a small quantity of alkali best of silver or platinum, remove the lamp which would otherwise be retained by the pre- and add enough sulphite of sodium to reduce cipitate. The precipitate is finally washed the iron completely to the state of protoxide. with hot water until the filtrate no longer gives Again heat the liquor to boiling, keep it boilany reaction when tested with nitrate of silver. ing for some time, and neutralize the acid with Since the aluminum is to be thrown down carbonate of sodium, added cautiously by small with chloride of ammonium, the saline wash pieces. Pour in an excess of caustic soda or liquor, above mentioned, need not be kept potash lye (or of ethylamin), and continue to separate from the remainder of the filtrate. boil sometime longer. If much iron be present, the voluminous white precipitate of ferrous An older method of procedure is to add the hydrate thrown down at first will finally be alkali to the solution of aluminum and iron, converted into black, granular ferroso-ferric instead of pouring the aluminum solution into oxide. Remove the lamp and allow the mixthe alkali. In any event, the iron and alu- ture to settle; pour the clear liquidinto a filter minum are usually precipitated together as made of not too porous paper; boil the preciphydrates in the first place, and the mixed pre- itate with a fresh quantity of soda lye, and cipitate collected on a filter and washed. In wash it thoroughly with hot water, first by dethe old process the subsequent operations are cantation, and afterwards upon the filter. The as follows:-Scrape the moist precipitate from aluminum is determined in the filtrate as Hythe filter with a platinum spatula, and place it drate of Aluminum. in a porcelain, or better, a platinum dish. Set Precautions. If, as is often the case, the the dish beneath the funnel which holds the mixture of aluminum, etc., to be analyzed, confilter, and pour drops of hot chlorhydric acid tains magnesium, a portion of the latter will into the latter until all the precipitate which be left combined with the ferric hydrate upon had adhered to it has dissolved. Remove the the filter. Some aluminum is also likely to dish and concentrate its contents, if need be; remain undissolved in combination with the 24 ALUMINUM. magnesium. So, too, in presence of calcium substance besides water and ammonia. In some aluminum is apt to escape solution. If case the matter under examination be cont amchromium be present, most of it will remain inated with any non-volatile inmpurity, distil undissolved with the hydrate of iron, but a off a lwage fiaction of a mleasured eoirtion of small quantity somietimes oxidizes and passes the liquid, as described under Alcohol (- oliinto the filtrate as chromate of sodium. tility ot), and take the specifie gravity of the In case the iron is reduced by sulphite of distillate. If any portion of the amlnionia is sodium. the liquid is liable to bump violently combined with an acid, mix a qualitity of before it actually boils. To prevent this bump- alkali with the liquid before distilliang it, as ing a spiral coil of platinum wire may be explained below under the principle Volatility. placed in the liquid, or the flask may be (Pfaff, Handbzch analyt. Cheem., 1825, 2. 25). shaken continually until its contents boil. The process is far inferior to those which deWhen boiling has once begun the bumping pend upon the neutralization of ammionia by ceases. standard acids. Special care must be taken that the soda or Principle II. Power of neutralizing acids. potash used be free from aluminum and silicon. Applicationls. Estimation of amlmonia in its The use of a porcelain dish should be avoided aqueous solution. Absorption of aun-mmonia gas if possible, since portions of the dish are dis- by acids. Use of ammonia-water as a nlnsolved by the hot alkaii, and impurities thereby tralizer and precipitant, in a multitude of added to the substance to be analyzed. cases, and as a stan(dard alkali in Acidinmetry. Method B. Fuse the mixed oxides of alu- Iethod A. To estimate ammconia in a soluminurn, iron, cobalt and nickel, with hydrate tion, weigh or measure out a quantity, say 10 of sodium or of potassium, in a silver cruci- c. c. of the sample to be tested, adld or 2 c. ce ble. Boil the cold mass with water and filter of litmus solution, and saturate with a stand(lar to separate the soluble aluminate from the acid in the manner described under Alkalimother oxides, which remain undissolved. The etry. Or measure out a lefinite quantity of residlual oxides, though free from aluminum, the standard acid, color it with litimus, and hold a certain proportion of sodium or potas- saturate with the ammonia to be teste(. In sium in combination, as well as a small quan- either case, the point of saturation is hit withtity of oxide of silver derived from the crucible. out difficulty. It is well always to weighll a The silver remains as an insoluble powder definite volumne of the liquid to be tested, for (chloride of silver) when the ferric oxide is by d(ividing the weight of the liquid in grmils. treated with chlorhydric acid. by its volume in c. c., we obtain the Specific Anhydrous oxide of aluminum, as it occurs gravity of the solution, and may subsequently in nature, is not readily attacked by alkalies. dispense with the balance in case any new Chenevix, for example (cited in Pfqtff's Hanid- portion of the liquid has to be taklen or buch anallyt. Chlem., 1824, 1. 449), found that analysis. The method of supersaturating the the mineral corundum couldnot be decomposed ammnonia-water with standard acid and deby intense ignition with 6 times its weight of termining the excess of acid with a stansiard caustic potash. To effect solution the mineral soda solution, is not to be recolmmended, ince should be fused with bisulpliate of sodium. almmornium salts, even when neutral, color iitChenevix fused with 200 to 250 parts of borax inus violet. glass and treated the product w-ith chlorhydric ellhetod B. Slightly supesaturate the amacid. maonia with chlorhydric acid, cvapor ato t Alumin um dryness at 100~ to 200~, and weitrb h tld CldcIs weigfhed in the form of anhydrous sesqui- ride of amnimonium. Or (after Alohlr, 7tir'.oxide. It is usually precipitated as a hydrate, methode, 1855, 2. 58) estimate the chlorfine ia though sometimes as a basic acetate or formni- the dry chloride of ammoniu m with a dilute ate, or as oxide. For the separation of alu- standard solution of nitrate of silver (sce ininum fromn the other metals, see the reference Chloride of Silver), and calculate Iow ci mich list in the Appendix. ammonium would be equivalent to this cleleriine. Ammon ia. (Compare Nitrogen, Nitrogen compounds, With regard to the use of almmnonla as a and Hydrate of Ammonium). reagent, the analyst should remecmbe- that the Principle I. Comparative lightness of the ordilnary anm-mnonia-water of colmm-ercec is o-fen aqueous solution, in proportion as it contains impure. Besides more or less car'bonate of nore aninmonia. alllinonium, it is liable to contain no inconsi(ApJplication. Technical estimation of the erable quantity of a soluble compound of iron value of amllmonia-water. and oroanic mnatter, which is apt to be dra,,',,'cd Method. Take the Specific Gravity of the down by gelatinous precipitates, and 1 to iIlterliquor with a Hydrometer, and refer to the fore in many ways with the accuracy of tables of " specific gravity and per cent am- ana(llyses. monlia," in any dictionary of cllenlistry. Colrn- F(ar (l flantitative work, clilcuicall, p1 rue aI — pare Acidiletry (ethodlll ly specific gravity). n)lia-water sio h(ld either be )r fil The liquid tested mllust contain no other soluble imant: tllrer of linle chemicals, (or!)i ncdt)[', AMMONIA. 25 expressly by distilling from a glass flask a chlorhydric or sulplhuric acid (see Acidimetry), mixture of 1 part of pure chloride of ammo- more thlan sufficient to absorb all the amnmonia nium, 1.25 parts of slaked lime, and 1 to 1.25 which can possibly be expelled fronm the subparts of water. The distillate is received in stance taken, and mix it with 2 or 3 c. c. of a three Woulfe bottles; of which the first, charged solution of litmrus. Pour a little of this acid with a small quantity of water, or milk of into the U tube of the apparatus, but no more lime, serves to wash the gas. The second than will fill the lower part of the tube in such bottle should contain about as much water, by manner that bubbles of air can readily pass weight, as there is chloride of ammonium in through the liquid. Pour the rest of the the flask, or in case a saturated solution is re- measured quantity of acid into'the tubulated quired, take two-thirds of this weight of water; receiver, together with a little water. the bottle should not be more than three- After proving that all the joints of the apquarters full at first, to allow for expansion. paratus are tight, heat the flask until its conThe third bottle should contain but little wa- tents boil slowly, and continue the operation ter. All the bottles should be set in a dish of until some time after the drops of ywater falling cold water to facilitate the solution of the gas. from the condenser have ceased to give the Heat the flask upon a sand bath, taking care least tinge of blue at the moment when they to avoid foaming, until half the water has dis- strike the liquid in the receiver. tilled from it. Pour the contents of the receiver and U Ammonia-water should be kept in glass- tube into a beaker, rinse with water and destoppered bottles. It should leave absolutely termine the alnount of free acid in the liquid no residue when evaporated to dryness, should by titration with a standard solution of caustic give no precipitate when diluted and tested soda (see Acidimetry). By subtractin g the with lime-water, or with chloride of barium; amount of acid thus found fromr the quantity or when tested with sulphuretted hydrogen or of aci] originally taken, we obtain the alnount nitrate of silver, after acidulationo of acid wThich has been neutralized by the Principle II. Volatility. amimonia. The amount of the latter is then Applications. Separation of ammonium from calculated (see Alkalimetry). all the elements. Estimation of ammonia in This methnod affords accurate results, and rain and river water (Method A). Estimation can be used in all cases where the substance to of ammonia in copulate ammonio-compounds, be analyzed contains no nitrogenized Lmatter, in urine, manures, etc. (Methods B and C). other than aunmmonium salts, capable of (leceomMethod A. Th4 mixture is boiled with caustic position by caustic lyes. It is to be observed soda,'potash, lime, or balryta. that the flask in which tlie decomiposition is 1. Prepare a distillatory apparatus as follows: effected must be placed in a slanting position, Fit to a glass flask a perforated cork or caout- so that no paritices of the fixed alkaline iqulid chouc stopper carrying a short delivery tube can be thrown into the delivery tube by the bent at an obtuse anlle; by means of a rubber movenment of ebullition, and that the end of connector attach this delivery tube to the head the condenser must not dip into the liAlaid in of a small worm or of a short Liebig's con- the receiver. denser, the lower end of which passes through If it be desirable to weigh the a'nmonoiuml a perforated cork into a capacious tubulated in the form of' a solid rather than to esticlate receiver; and to the second orifice of the re- it by titration, the receiver and U tub.e mlay ceiver attach a U tube, by means of bent glass be chargred with chlorhycdric acid u ard the connections. According to S. NV. Johnson, ammrnonium weighed as Chloride of' Aminothe worm or condensing tube should be made of nium or as Chlloroplat~inate of Ammionium. block tin, since glass yields a sensible amount 2. Place a litre of the water to be exainmnec of alkali to hot steam. in a retort capable of holding at least four litres, Pour into the fiask as much of a moderately add to the liquid 25 c. c. of baryta watcr,- or strong solution of caustic soda, caustic potash, in place of the baryta, lime, potash or sodta,or milk of lilme, as will fill somnething more to retain the carbonic acid. Connect -he rethan a third of it. Place the flask in a slant- tort with a condensing apparatus, and distil ing position upon a wire gauze support and the water slowly until the distillatd, anmounts to boil its contents until every trace of ammonia, a quarter litre. Determine the proportion of with which the alkali may have been contami- ammonia? by titrating with normal sulphlhiric nated, is removed. Then cork the flask andc acid (Boussingault), or deterimmlc tine aminoleave it until its contents have become ther- nia in the distillate by Nessler's testO See oughly cold. Iodide of IMlercurammoniuml (M'iller). Weirgh out the substance to be analyzed in 3. For determining ammonia in trine, F. a glass tube, 3 or 4 c. im. long by 1. c. m. wide, Mohlr (TZtrirtetuiode, 2. 216) has l prolose0d irs closed at one end. Place the tube and its con- place of }Methood C, the following modification tents in the flask after tle- latter h2as becoalme of the proccss:-Carefidly neutralize tlPc urine cold, and connect the flask with the condens- withl a. dilute solution of' caustic potash, add inr apparatus. to the neutral liqiol a mIcalsure.l qalctity of Metsure oif a quantity of sta-ndard oxalic, sland:ict potash, -noe than sufficlt A to tecelm 26 AMMONIA. pose all the ammonium salts in the solution, enough to reach from the top of the cork to a boil the mixture as long as ammonia continues point an inch or more below the rim of the to be evolved, and finally, without heeding the flask. The caoutchouc is finally tied firmly ammonia which is set free, determine the with twine, both to the neck of the flask and amnount of caustic alkali left in the urine, by to the head of the cork. When everything is means of a standard acid. The points of neu- ready, place 10 c. c. of standard acid in the tralization are determined in both cases by cylinder (Boussingault uses sulphuric acid means of litmus paper. The presence of urea strong enough that 10 c. c. shall saturate does not affect the accuracy of the results, 0.2125 grm. of ammonia), and set the cylinder although this substance is decomposed by in a beaker of cold water-ice water is best, boiling potash, nor does hippuric acid do any though the apparatus gives satisfactory results harm. In cases where no great degree of when the temperature of the water is as high accuracy is demanded, the process appears to as 12~ or 15~. Pour into the flask 50 grms. be applicable for testing human urine, though of the urine to be tested, add to it about 5 in that case it indicates rather less ammonia grins. of slaked lime, cork the flask and set it than the processes of Schloesing and Boussin- in a water bath so arranged that it may be gault. But for testing the urine of cattle it kept constantly at a temperature of 35~ to 40~. cannot be relied on. Rautenberg (Zeitsch. Close both the stop-cocks upon the apparatus, analyt. Chem., 1863, 4. 500) has shown that exhaust the receiver of the air pump, and then with the urine of oxen Mohr's method always slowly open the stop-cock on the tube which indicates a larger proportion of ammonia than connects the receiver with the cylinder charged can be obtained by the methods of Schloesing with acid. The liquid in the flask will soon and Boussingault, the accuracy of both of begin to boil. When this happens, close the which has been well established. This appar- cock again, and leave the apparatus to itself: ent excess seems to be due to the decomposi- Since the cylinder which contains the acid is tion of various ingredients of the urine which, comparatively cold, the vapors distilled fromn though originally neutral, become acid when the flask immediately condense in it. The exposed to the action of boiling potash, and liquid in the flask consequently continues to so neutralize a portion of the standard alkali. boil tranquilly, and after a short time will MIethod B. The Ammonium Compound is evaporate completely, so that nothing but a heated in a comibustion tube with an excess of dry residue is left in the flask. In order to Soda-Lime, in the manner described under sweep forward any ammonia vapor which may Nitrogen. The ammonia is collected in acid be left in the flask, open theestop-cock above it and determined as in Method A. slowly, so that air may enter. Then close the Method C. The Ammonia is set free by Hy- stop-cock, exhaust the receiver, and slowly drate of Calcium, or by potash or soda lye, at a open the second stop-cock beyond the acid low temperature. cylinder, so that the air in the flask may be 1. By ebullition in vacuo (Boussingault's pro- drawn forward through the acid. Finally decess, MIe'rmoires de Chimie Agricole, Paris, 1854, termine with a standard alkali (Boussingault p. 292). To a strong flask of about 1 litre capac- uses a solution of lime in sugar water) how ity, fit tightly a cork carrying one straight tube much of the standard acid originally taken is provided with a stop-cock and one gas delivery still left unsaturated in the absorption cylinder. tube, bent at a right angle. The straight tube (See Acidimetry). The process requires far less should reach to within a few m. m. of the bot- time than No. 2, and is equally accurate. It tom of the flask, while the bent tube merely has the disadvantage of requiring comparapasses through the cork. By means of a short tively complex apparatus. piece of rubber tubing tied tightly to the glass, Instead of this method of ebullition in vacuo, connect the gas delivery tube with another Boussingault has attempted to remove the amglass tube of' similar bore, bent at a right monia from mixtures of urine and slaked lime angle and reaching nearly to the bottom of a by means of a current of air made to bubble narrow cylinder proper to receive a charge of through the liquid continually through 4 or 5 standard acid. The cylinder is fitted with a hours, at the temperature of 350 or 400; but cork, and is connected by means of a second without good results, for a part of the ammobent glass tube, provided with a stop-cock, nia was always retained in the solution. To with the receiver of an air pump. The corks ensure the complete and speedy evolution of of the apparatus must fit tightly enough to sup- the ammonia in this way, Boussingault found port the external pressure which will be ex- that the solution must be heated to 900 or erted upon them by the atmosphere, when the 1000. But these high temperatures are inadair is pumped out from within the vessels. missible in the analysis of urine, for ammonia To strengthen the corks it is well to wind would be formed through the decomposition of about their heads strips of sheet cork or of the urea which the urine contains. sheet lead, so that the head thus thickened 2. By Exhalation at the Ordlinary Temnperamay be as wide as the neck of the flask. The ture. (Schlocsing's method). Select a shallow, whole may then be bound firmly together by flat-bottomed capsule 10 or 12 c. m. in diameter means of strips of sheet caoutchouc, wide and weigh it. Measure out something less AMMONIUM. 27 than 35 c. c. of the liquid to be tested, and strength. Sometimes the nitrogen of an amplace it in the dish. Weigh the dish and liquid. monium compound is collected and measured, Then set the dish on a common dinner plate and the amount of ammonium calculated from filled with mercury. Bend a thick glass rod that of the gas. Ammonium may be sepainto the form of a tripod, place this tripod in rated from all metals excepting those of the the capsule which contains the solution to be alkalies by precipitating the metals by means tested, set upon it another shallow dish which either of H2S, (NH4)HS, (NH4)2C03, or Na2H has been charged with 10 c. c. of standard P04. oxalic or sulphuric acid (see Alkalimetry), Ammonium Salts. and invert a beaker over the whole. Fill a (Compare Nitrogen and Nitrogen Compipette, provided with a wide aperture, with pounds.) milk of lime, lift up one side of the beaker as Principle. Volatility. far as may be necessary, and allow the con- Applications. Separation of certain ammotents of the pipette to flow into the solution of nium salts from salts of Li, Na, K; Ba, Ca, the ammonium salt. Immediately replace the Sr; Mg, Zn, Cd; Al, Cr, Ilr, Mn, Fe, Co, Ni. beaker and put a weight upon it, so that its The ammonium salt must be wholly volatile, lower edge shall be pressed into the mercury. and the mixture to be examined free from After 48 hours lift the glass at one side and other volatile or decomposable matters. thrust a bit of moistened red litmus paper into Methods. the atmosphere within; if the color of the paper remains unchanged, the first stage of 1. Separation of Ammonium Saltsfirom Salts the operation is finished; but if the paper be- of Na, Li, K; Ba, Sr, Ca, Mg and Cr. In colle blue the glass must be replaced, and the case the dry mixture to be examined contains apparatus left -to itself for another term of but a single acid, such as chlorhydric or sulhours. When all the ammonia has been ex- phuric acid, heat a weighed portion of it to pelled from the original solution, and has been faint redness in a covered platinum crucible, absorbed by the standard acid, determine how as long as any fumes are evolved. The differmuch free acid is left, by titration with a ence between the weight of the crucible and standard solution of caustic soda (see Acid- contents before and after the ignition gives the imetry), and calculate the amount of ammo- weight of the ammonium salt. The crucible nia from that of the acid which it has neu- must be heated gently at first, but must aftertralized. wards be kept for sonme time at a dull red heat. Instead of the beaker and plate of mercury In case the salts are sulphates, the crucible above described, a bell glass with ground rim must be heated with special care, in order to may be placed air tight upon a greased ground avoid loss of material through decrepitation of glass plate. A tubulated bell provided with a the sulphate of ammonium, and the residue must ground glass stopper is to be preferred, since, finally be ignited in an atmosphere of carbonate in this case a strip of litmus paper attached to of ammonium (see Sulphate of Potassium) for a thread may be introduced into any part of the purpose of decomposing a quantity of acid the jar without lifting the latter. sulphate of potassium, which is formed by the Method C, in both its modifications, is useful decomposition of a part of the sulphate of amin cases where the presence of organic matters monium. - If the mixture to be analyzed decomposable by boiling alkalies precludes the contains more than one acid, it may be mnoisuse of Method A. - Reischauer (Zeitsch. tened with a quantity of free acid, similar to analyt. Chem., 1864, 3. 138) has shown that the least volatile of the acids in the mixture, even after six months' action, cold potashor and evaporated to dryness upon a water bath. soda lye has no power to set free ammonia The operation should be repeated several from cyanogen compounds. times, or until the more volatile acids have According to Schloesing, 48 hours are al- been completely expelled. A mixture of chloways sufficient to expel 0.1 to 1 gramme of ride of ammonium and sulphates of' the alkali ammnonia from 25 to 35 c. c. of solution; but metals cannot be analyzed in this way, for on Fresenius has found that this statement is true igniting the mixture the sulphates would be only with regard to quantities less than 0.3 wholly, or in part, converted into chlorides. grin. When the quantity of ammonia exceeds 2. Secaration of Anmmonium Salts from Salts 0.3 grin., 48 hours is often insufficient for the of Zn, Cd, Al, Ur, Mn, Fe, Co, Ni. complete expulsion of the ammonia; it is well, If there is no chloride of ammonium in the therefore, to operate, if possible, upon quanti- mixture to be analyzed, a weighed quantity of ties of substance which contain no more than the mixture may be ignited directly, as in No. this proportion. 1. But if chloride of ammnonium be present, Ammoni u m. the process becomes less accurate. When For the separation of ammonium from the compounds of aluminum and iron are ignited several elements, see finding list in Appendix. with chloride of ammonium, a certain amount Alllmonium is usually determined as chlo- of chloride of aluminum or of chloride of iron, ride, chloroplatinate or tartrate; or by titrat- as the case may be, is lost through volatilizaing ammonia-water with an acid of determined tion. Under like circumstances manganese 28 ANTIMONIC ACID, compounds are converted into protochloride of the whole of the antimonic acid, anod thIe mixec manganese mixed with some manganite of man- solution mnust be heatecd to 40~ Fiinally dleter ganese; zinc compounds volatilize as chloride of mine how' much stannons chloride renl'fins in zinc, and compounds of cobalt and nickel are the solution, by means of a stand(ard solution reduced to the metallic state. The safest rule ef' iChro-late of' Potassium. oces i of in all these cases is to aix the sample with car- limited application, and is said not to viti bonate of sodium before igniting it, an(l to very accurate results. (See Chloridle of T'in)o determine the metals in the residue by some AlrliMonjiate of AntirTnony. appropriate process. The ammonia may then (Imlproperly "Antimnonious Acid ) be estimated in a separate portion of the mix- Princiople. Fixity of the compound when tnure by distillation with an alkali.'(See Ami- heated. monia). Applications. Estilmation of antimony in Ammonio-Sesquioxide of Ura antimonions and antimnonic acids, and in coinniu m. pounds of these acids with easily volatile or See Oxide of Uranium (ammofiiated). decomposable oxygenatedl acids or bases. DeAntirmon ic Acid. termination of antimony in sulphitde of anti Pri'nciple L Sparing solubility in nitric nonvy acid. 3ioethod. Antimonic acid mray hbe simply Applications. Separation of antimony from, ignited in a platinuml crucible uiitil the weight; LMg, Zn, Cd; Mn, Fe, Co, Ni; Bi, Cu, lIg, remains constant. Other coimpoutnds of amitiAg and Pb in alloys. mony should be treated with nitric acid fiee ilMethod. Dissolve the alloy in nitric acid or froni chlorllydric acid, and thlle solutionl carein aqua regia, as described under binOxide of fully evaporated to dryness before ioniting Tin. Collect the insoluble residue of antimo- the-m. Care must be taken to gu-ard the connic acid upon a filter and ignite to convert it tents of the crucible, ageinst tilaeat(ti(n of' reinto Antimoriate of Antimony. The results ducing gases coming fi om tl e filter or the are only approximative, since a small portion flame. of the antimony always remains dissolved in For converting sulphide of antiony illto the acid. Alloys of lead and antimony, con- anti-moniaite of antimlony, Bunsen has devis(ed taining a large proportion of antimony, should two methods, as follows:be fused with a weighed quantity of pure 1. With fJoniy Ai Nitric Acid. IPlace tl-hl lead before treating them with nitric acid, lest dry sulphide in a weighed porcelain crucible, a part of the alloy escape solution. Ac- moisten it with a few drops of nlitric acid of' cording to Pfaff (fandlbuch analyt. Cliem., 1.42 specific gravity, and cover the crucible 1825, 2. 416), the antimonic acid is apt to loosely with a watch glass or sm1alt funnel irom retain a certain quanitity of oxide of leadi, so which the tube has been cut axay. Carefh!iy firmly combined that it does not dissolve in pour upon the sulphide 8 or iO times its bullk nitric acid. of reld ftmiiilg nitric acid, place tie crueible on This process was formerly much employed a water bath and allow the acid to evaporate for analyzing antimony alloys, and is still used slowly. WVihel the nitric acid is first added to for technical analyses, where no great accuracy the sulphide, a quantity of sulphur Separates is required. It is now recognized, however, in ilne powder, but subsequentl y oxidizes colnthat-owing to the solubility of antimonic pletely during the process of evapeorition, so acid in nitric acid —the process yields far less t!aat noiithi g but a vhite niexture o almti onie accurate results than the corresponding method and sulphuriie acids is left in tle cru ci0ieo )y with Oxide of Tin. By repeatedly evaporat- igniting tiLs residue it is conlverted iJlto anrtiting the nitric acid solution of antimonic acidl monate of' antimony -- In'ca'o thle sulto dryness, and treating the residue again and phide ofi altin:ony urnder examini tion happens again with fresh portions of nitric acid, it is to be n ixcd with a larec pirportion of fiec indeed possible to obtain at last a solution free sullhtr, it t ustbe wasiled with b:l`;tulidce of from antimonic acid, butthe operations require carbon bel'ore addiingr the nitric acid. Th'le so much time that they are not enmployed in washing may be eflected as folowsio:- - y actual practice. neLans of a perloratcd cork, fit the fiunnc wh-li' Principl IIo. Power of changing stannous contains the filter and thle dried sulpl:ide of to stannic chloride, while it is itself reduced to aetimonv, o ir t;iht to the m out! of,;t-:t til)c, the state of a'ntire7onios acid. pour enougb sullphiilde of' carboe.. into th(e filter AppEcatio es. Estimnation of antimony in to cover the dry precipitate, then cover t11e cases where the metal can be converted into funnel ti hitly with a glass plate, an l ea ve t e antimenloni acidm. njppar:ttus at rest for several horS. o in-JtyMlethod. 4 inx a weighed quantity of the ioosen! the cork ald allow the biri,,lide of antimnonic acid with a measured volume of a carbon to lowv into the test tule. 1',,)eant til standar(t soluticn of protochloride of tin, to- operm1ation, if' needl be, withi a flesh un,' lttity- of gethier with soime iodide of' potassiuml solution bisulphide of carbon; 10 or 15 or,~uso of tlle and starch paste. The quantity of' tlhe tin bi ul phido will, ini most cases, e c i cdOlution must be imOre than suhlihicic' to reuL ce airig a uigle I'icil)iatite it'l.l a0 l wtays ANTIMIONIATES. 29 easily recovered by distillation and kept for which exactly fits the crucible. Fill the crueifuture use. ble loosely with oxide of mercury to the briAl, It is to be observed tllat fiminig nitric acid and slowly push the glass through the mercury is essential to tbe succss of this process. The to the bottom of the crucible, occasionally ordlinary strong -nitric acid of 1.42 specific sllhaking out the oxide from the interior of the gravity will not,answer. The boiling point of glass. A layer of oxide of mercury from half the acid of 1.42 specific gravity is almost 100 a line to a line thick, may thus be pressed hi her tihan the m!elting point of' sulphur, against the crucible so firmly that it will adhere while the fiminr acid boils at a temperature to the platinum after the removal of the glass. as low as 8G~, far below that at which sulphur Properties. Antimoniate of Antimony is a maelts. Thle lhot fir.fiing( acid easily oxidczes white powder when cold, but exhllbits a velthe finely divided sulphur vwith which it is in lowish tint while hot. It neither fuses nor contact, but when heated witlh acid of 1.42 decomposes when ignited in the air. It is specific gravit.y the part-icles of sulplur quickly scarcely at all soluble in water, thouglh it exmelt to a solid ball, which obstinately resists hlbits an acid reaction when placed upon moist oxidation. litmnus paper. it is not acted upon by sulphyNo chlorhydric acid should be present lest drate of anmmonimum, and dissolves in ehlorhysome of the antimon be lost through volatili- dric acid with very great difficulty. Its zation of the torchocride when the dry mass is composition is:ignited. Sb = 122 = 80.26 2. By gTnityion with Oxide of fIercury. 02 = 2 = 1'3.74 lix the sullphllde of antimony with from 30 to 1i4 100.00.50 times as much precipitated oxide of' mer- Ant3 o n~ate o ercry. cury, and heat the mixture gradually in an (Mnenious a*ti on e. r (M~ercurous antimaoniate). open weighed porcelain crucible. * lemove the Z Principle. Insolubility in water. lamp as soon as the appearance of gray fumes o ->.. t>1 h zAppications. Separation of anti-mony from of mercury indicates that oxidation has begun. and soiu. Again heat the mixture as soon as the fumes Potassium d Method. Mlix the solution of the antimoslacken, and proceed in this way as long as * t M slacken, aid Iri1oce *' i this way as l1o as niate with an excess of a solution of' nitrate of fuihes are evolved. Finally ignite the crucible su ide of merc llo t ixtre to suboxide of mercury. Allow tbe mnixture to over a blast larmp to remove the last traces of stad at rest f many hours, cllect e r stand at rest for many hours, collect th1e prooxide of mercury, and weigh the residual antimoniate of antimony. cipitate upon a filter, wash with a solution of,zntironiat ot'.~nt. ~ mercurous nitrate, dry, ignite strlong)y, and Care must be taken that no reducing gases eigh as Antimoniate of Anti rongy. eove fa 7, w el(Th as Antimoniate of Antimony. iRemove from the lamp gain access to the contents of the excess of mercuy from the filtrate by the crucible. Since oxide of mercury always means of lpurtt hydrogen or c alorhylric leaves a small quantity of fixed residue, even acid, and determ the alkalies in te fi acid, and determine the alkalies in the finsa: after intense ignition, it is well to determinesual way. of 1litrate in the usual way. - Antinioniate of' the proportion of this impurity once for all, to ercury, mixture of weigh roughly the amount of' oxide of mercury rou d'7' z7t~ -.'. crous nitrate and antimoniate of potassium or taken to oxidize any sample of the sulphide, sodium settles With extreme slowness, but the and to subtract the amount of fixed residue t nmixture may nevertheless be filtered witlhout contained in the oxide of' mercury taken from the weight of the xantimoniate of m aiiytiinony. special difficulty, if it be first allowed to stand the weight of the antimoniate of antimony. If the sulphlide of antimony is mixed with f or a long tne f odi fiee sulphur, this sulphur Ilust be removed by Atimonliate of Sodiu.e means of bisu!plpide of carbon, as in No. 1, innsolubility in dilute lohol. order to avoid slight defiagrations and conse- Applictions. Separation of antimony from quent loss of substance, which would otherwise arsenic and tin. occur when the sulphide came to be heated with oxide of mercury. 1. Place the substance to be analyzed, which The operation may be conmpleted much more may be an alloy of antimony, arsenic and tin, quickly in a platinum than in a porcelain cru- or' a mixture of sulphide of antimony and sulcible. Biut if' a platinum crucible be employed phide of tin, in a large beaker, and pour upon it must be protected fioomn the action of anti- it, little by little, nitric acid of' 1.4 specific mony by means of' a lining of oxide of iner- gravity, until the oxidation is completed; an cury. This lining may be made as follows: - alloy should be reduced to the state of fine Soften the end of a test tube at the blast lamp, powder before weighing. For an alloy, the place the soft end of the tube in the centre of nitric acid employed must be of' the prescribed the platinum crucible, and blow air into the strength, since acid of 1.52 specific gravity other end of the tube, so that the hot glass would not attack the alloy; but for the treatmnay assumle the exact form of the crucible. ment of sulplhides the stronger,tcid is to be Criack off thle ibottom of the bulb tlhus foried, preferred. When the reaction has cease(l to and carefiully smooth the sharp elgre by flssion. be violenlt, transf'er the mlixtulre firoml te;e ker:: A glasvs is, thu obtaited, opel i at both clds, to a s1,lill )i'CoChttill dish, cv1port)te to d'ryneLs 80 ANTIMONIOTTS ACID. on a water-bath, transfer the residue to a sil- nate of sodium, it always retains some carbonver crucible, rinse out the porcelain dish with ate or sulphate of sodium when washed as a solution of caustic soda, and again evaporate above directed. - The process yields exto dryness. Add to the contents of the cruci- cellent results when properly conductedl. The ble as much solid hydrate of sodium as will antimoniate of sodium settles completely friom amount to about eight times the bulk of the the alcoholic solution, and the latter is easily residue, and fuse the mixture for some time at filtered. The only real inconvenience arises a red heat. WVhen the crucible has become fiom the necessity of using a silver crucible, cold, cover the fused mass with water, and and the consequent liability of contaminating allow it to soak until it softens, then wash out the alkaline filtrate with a small amount of the contents of the crucible into a beaker, silver. with hot water, and continue to add water To determine the tin and arsenic in the filuntil the undissolved residue has assumed the trate, acidulate the liquid with chlorhydric form of a fine powder. Stannate and arseni- acid, and without heeding the precipitate of ate of sodium go into solution while most of stannic arseniate which forms, pass sulphurthe antimoniate of sodium remains undissolved. etted hydrogen gas for some time through the Add to the solution in the beaker as much al- turbid liquid. Allow the mixture to stand cohol of 0.83 specific gravity as will amount to until the odor of sulphuretted hydrogen has about one-third the volume of the solution. well nigh disappeared, collect and weigh the Cover the beaker with a glass plate, and let mixture of sulphide of tin, sulphide of arsenic the mixture stand for 24 hours with frequent and free sulphur upon a tared filter, and finally stirring. Collect the insoluble matter in a fil- heat a portion of the precipitate in a current ter, rinse the beaker with spirit made by mix- of hydrogen to expel the sulphur and Sulphide ing 1 vol. of alcohol of 0.83 specific gravity of Arsenic. with 3 vols. of water, and wash the pre- If' there be no arsenic, but only tin in the cipitate upon the filter, first with a mixture of filtrate, drive off most of the alcohol by evap1 vol. alcohol and 2 vols. water, then with a orating at a gentle heat, dilute with water and mixture of equal volumes of alcohol and water, supersaturate with sulphuric acid to precipitate and finally with a mixture of 3 vols. alcohol Hydrate of' Tin. Or precipitate Sulphide of and 1 vol. water. It is well to mix a few d(rops Tin. The precipitation with sulphuretted of a solution of carbonate of sodium with the hydrogen is safer than the other process, dilute alcohol used for washing. The carbon- though the sulphide of tin will be contaminated ate facilitates the solution of the stannate of with a trace of sulphide of silver from the sodium, and hinders the antimoniate of so- crucible, while by using sulphuric acid no comdium from passing through the pores of the pound of silver is thrown down. filter. _ Continue to wash until a portion In case there be no tin, but only antimony of the filtrate acidified with chlorhydric acid and arsenic is the substance to be analyzedc and mixed with sulphuretted hydrogen water the arsenic may be determined as Arseniate of gives no yellowish precipitate of sulphide of Magnesiuml and Anlmonium. To this end, tin after long standing. heat the alcoholic filtrate, with the addition of It is essential that the alcohol used for wash- several fresh quantities of water, until the ing shall be of the prescribed strengths. If odor of alcohol has almost disappeared, acidustrong alcohol were used at first, a quantity of late with chlorhydric acid and proceed in the carbonate of sodium formed during the fusion usual way. would be left undissolved upon the filter, and 2. In the case of mixtures of the sulphides would retain stannate of sodium in comnbina- of arsenic and antimony, together with fiee tion, to such an extent as to occasion losses sulphur, such as are often obtained in mineral even as great as 8 or 9 per cent. Weak alco- analyses, the process may be modified, as folhol, on the other hand, dissolves some anti- lows: -Place the precipitate in a porcelain moniate of sodium, together with the stannate. crucible, oxidize it with red fuming nitric acid Water alone cannot be employed for the free from chlorine, evaporate nearly to drywashing. Not only is antimoniate of sodium ness, mix the residue with an excess of carbonsomewhat soluble in water, but a portion of the ate of sodium, together with some nitrate of precipitate itself would pass through the pores sodium, and fuse at the lamp. Treat the fused of the filter as soon as the stannate and car- mass as directed in No. 1. bonate of sodium had been washed away, if Antimonious Acid, (Sb2O3). [For nothing but water was employed. the compound Sb,O4 —solnetimes imllproIerly When the antimnoniate of sodium has been called antimronious acid, see Antilmoniate of thoroughly vwashed, rinse it from the filter into Antimony.] a bleaker, leach the paper with a mixture of l'riociple 1. Oxidation by Iodline (A) or chlorhydric and tartaric acids, dissolve the by Chlorine (B) in alkaline solution; by Biprecipitate in the samle mixture of' acids, and Chromate (C) or Permlanganate of l'otassium precipitate the antimony as Sulphide of Anti- (D), or by Salts of Gold (E). mollony. The antilnoniate of sodiuiri cannot be The Applications of A, C, and D, are lindiweighed directly, since, though fiee fioml stanl- ted to the estimation of antimnonious acid ill ANTIMONIOtUS ACID, 81 pure solutions of this substance —such as the B. Oxidation by Cilorine. Same as under chlorhydric acid solution of sulphide of anti- Antimony. mony and, as regards A and D, a solution of C. Oxidation by Bichromate of Potassium, tartar-emetic — and to the determination of To the solution of antimonious acid in diluted antimonious acid when mixed with antimnonic chlorhydric acid, add a measured volume of a acid. The applications of B will appear be- standard solution of bichromate of potassium5 low under the head of Antimony. more than sufficient tp oxidize the whole of 3lethods. To separate antimonious from an- the antimony. Leave the mixture at rest for timonic acid, determine the total amount of a short time, and finally determine the amount antimony in one portion of the substance to be of unreduced chromate by means of a standanalyzed, by precipitation of Sulphide of Ain- ard solution of ferrous sulphate, added until a timony. Determine the amount of antimoni- drop of the mixture gives a blue precipitate ous acid, in another portion, by one of the when touched to a drop of ferricyanide of processes enumerated below, and calculate the potassium. (See biChromate of Potassium), amount of antimonic acid from the difference. The original chlorhydric acid solution should A. Weigh out as much of the substance to contain at least one-sixth its volume of chlorbe tested as will contain about 0.1 grm. of hydric acid of 1.12 specific gravity. It will antimonious acid. Dissolve the weighed sub- often be found convenient in practice to opestance in 10 or 12 c. c. of a strong aqueous rate with solutions composed of about equal solution of tartaric acid, in case it be not al- volumes of water and chlorhydric acid, but in ready a tartrate, and add enough carbonate of case more acid than this is present, the delisodium solution to nearly neutralize the liquid. cacy and promptitude of the final reaction Mix the solution with 20 c. c. of a cold satu- with ferricyanide of potassium is materially rated solution of bicarbonate of sodium, add a diminished. As with arsenious acid, bichrofew c. c. of thin starch paste, and pour into the mate of potassium does not act upon antitmomixture, drop by drop, from a burette, a stand- nious acid in any definite or reliable way when ard solution of Iodine in iodide of potassium the solution in which the oxidation is to be until the liquid just remains blue, or better, is effected contains less than one-sixth its volume of a faint red color. The mixture must of of chlorhydric acid. Since tartaric acid decourse be stirred continually while the iodine composes the bichromate, its presence is inadsolution is being added to it: — missible. Sb203 + 2Na2O + 41 = Sb2O - 4+ MaI. If the substance to be analyzed is free from organic matter, oxides of the heavy metals7 So long as there is any antimonious acid pres- and other substances capable of interfiring ent to be oxidized, the blue color formed at the with the titration, it may be dissolved at once surface of the liquor where the iodine solution in chlorhydrie acid; otherwise the antimony first touches the starch, will be destroyed as fast must be precipitated, in the first place, as a as it forms. But as soon as the last trace of an- Sulphide. To prepare the sulphide for titratimonious acid is oxidized, the whole solution'tion, place the washed precipitate, together will become blue. The operation must be with the filter, in a small flask, cover it with stopped at this moment. The blue color will, chlorhydric acid, heat the mixture on a water in any event, disappear after a few minutes. bath until the precipitate has dissolved, a(l(l to The value of the iodine solution may be deter- the liquid as much of a nearly saturated solumined beforehand by titrating 0.2 or 0.3 grim. tion of mercuric chloride in chlorhydric acid of pure crystallized tartar emetic. (Mohr, Tit- of 1.12 specific gravity as may be needed to rirmethode, 1855, p. 371). remove the sulphuretted hydrogen, dilute the Though the results obtained by this process mixed solution to some definite volume, allow are, on the whole, satisfactory, it is, according it to settle, and take up a measured volume of to Fresenius, essential that the proportion of the clear liquid for the analysis. (Kessler, Pogantimonious acid to that of bicarbonate of gendorf's Annalen, 95. 215; 113. 134; and sodium be maintained tolerably near that of 118. 17). the quantities above enumerated, in order to D. Oxidation by Permanyaynate of Potasensure accuracy. Bicarbonate of sodium should siumn. Pour a standard solution of permangaalways be employed as the alkaline liquor, nate of potassium from a burette into the since the monocarbonate has the power of fix- chlorhydric acid solution of antimonious acid, ing a certain amount of iodine. until the solution exhibits a permanent red Instead of titrating directly with a solution color. The permanganate solution should conof iodine, as above described, H. Rose directs tain about 1.5 grmin. of the crystallized salt to that the standard solution of iodine be added the litre, and the antimony solution at least to the slightly alkaline solution of antimony as one-sixth its volume of chlorhydric acid of long as its color continues to be discharged, 1.12 specific gravity. It is not well, however, and that the excess of iodine be then deter- to have the proportion of acid higher than mined with a stanldard solution of Ilyposul- one-third the volumle of the liquid, since tlihe phite of Sodium. final reaction would be interfitred with. The 82 ANTIMONY, presence of tartarlc acid has little or ro inrfu- rapidly wth hot water and dry at 1000, best once upon the reaction. Hence the pracss in an atmosphere of non-oxicdizin r gas. - To may be employed for analyzing tartar emetic, seare antimo.ny Pi'vn tin, boil the alloy with and thoe vie of tihe perimanganato solution chlorhydric acid [taking carae to absorb aany may be determined in the beginning by means aitimoniuretted`ydrogen that is evolved ('se of a standa-rd solution of pure tartar enetic. below, Method 3.)] until Ial I e e tin has disFor the preparation.of the antimony so- so(lved, then place a rod of pure t'n in the tion see aove, C. (Ke ssler, Poygyen'oiff's liquoor to precipitate aniy traces of anntimony Arnnalen,!!8. 17). whvich may have dissolved, and proceed as E. Oxidation by Salts of Gold. A process before. (Pfaf, lc. cit., p. 410). formeirly recomnmended by H. Rose consisted f dieod B. To analy ze an alloy of tin and in mixing the antiionicus acid, dissolved in a antimony, dissolve it completely in chlorhydric very large excess of' strong chloryric acid, acid to which a little nitrc aci'd has been with an excess of coforau'toe of sdiu r aded. lia't t 1'1 sotl.tion nearliy to boiling, chloraurate of' ammoni um, ieavin he ixtue an t' 1hrow into it bits of fine iron wNre (pianoat irest durin' sneveral days at a tempraturei' wo'e), as long as th-e latter con0inues to disslightly wor7nrer'tbn thiat of the air, and col- solve. As soon as ell the antinlony has been lecting and wei-i'ng the mietallic gold which prcoipitated, and the last piece of iron seems was deposited, as was supposed, in quantity to l:ave cenopletely disolved, adtd a little iore proportion-ato to the amnct of antisoonious chlorhydric acid; alow the precpitte to setacid in the solution. But since Dexter (1eojo. tie, decant th e clear liquid, and try whether Ann., 100. 570; conopare IL Rose, ibid., 1O0. any ihrther precicpitate can be produscld in it 511) has showin thla 1he process affords neither by means of iron. Wash the precipitated concordant nor reliable results, it can no longer antnmony at first with hot water ancindulated be cosmendied with Cn!orhidlric acid, afterwSards with pure Ps'i sieepoe I. Volatility. hot water, and finally with strong alcohol. 3fesod. To separate antimony fronm silver, To ncilitato the opacration of drying, and to gohl, tandt other noble metals, the alloy aay be still further guard against the risk of oxidation, heated upoln a cupel in a muffle. By the it is well to wash out. the alcohol with a few action of the hot air the antimony will be dropo o fther. Dry the procipitate cquickly convertced int o a anii aoenlus acid, andl the latter at I000, and wveioh. Tihe process yields will go off in the form of vapor, leaving the good results when the proportion of tin is silver or gold to be weighed. It has been lar1e, but is less accurate when the solution foundi n practice that a sinple alloy of' silver contains but little tin. (Tookey & Clasen, and astinlon y hieae I upon bone ash in a nuffle, ZLesch. ocalyt. Chems., 1865, 4. 440). until fhmes of antinonious acid are no longer if I/hod C. Plice the alloy or other convisible, still reta's about one per cent f an- pound in a small 1flask, cover it with strong tinsony, the resicdual button of' silver beinTr ci orhydric acid, heat the mixturo and add,dull and gray, and only incompletely soluble snall crystals of chlorate of potassiumn, one by in nitric acid. JTut by again heatin' the but- one, until the solution is complete. Dilute the ton on a cupel withll about 5 times its wei ht liquid to some definite volume, and divide it of lead, until the lead 1has all been oxidized into two equal parts. In one part precipitate and the mielted silver appears bright and lis- both the antimony and the tin on a rod of trous, the antimony may be completely ex- metallic zinc and wash, dry and wemigh the pelled. powder. Mix the other part with a tolerably A n til many. [Compare Antimony Coin- larglie quantity of' chlorhydric acid, place a pounds]. clan strip of mietallic tin in the liquid and Antimony is estimated as metallic Antimony, Lost the whole gently for some tine. All the as Sulphide of Antimony, Antiioniat e of An- antimony will be precipitated while the tin is timony, Anti1moniate of' Sodium, or by titration, reduced to the condition of stannous chloride. as has been explained under Antimonious Acid. Wash the precipitate with water acidulated See also Antimonic Acid, and the finding list with chlosrhydriic acid, collect it on a tared filin Appendix. ter, dry and weieh. The difference in weight P1rissciple I. Sparing solubility of the metal between tihe first and second precipitates gives in chlorhydric acid. the namount of tin. - In case the substance Apjplicelions. lEstimation of antimony in to be exasined contains nothing but antimnony antinmony salts. Separation of antimony firom and ti n, the irst prccipitsation with zisnc nsay tin. be oitted, t nd tie did-'rence between the Miethod A. Precipitate the antimony by weighit of' alloy taken anid that of' antinmony means of netallic zinc fromn a dilute nitric acid found nmay be rSeg'ded as the weiriglt of the solution. The antimony sfils as a black pow- tin. Since antitiony is not compleOtely precipder, h Ish glstents whion buasisished.. ( i s ataited by as at _ie1 orina r tc:pc:t a'tis, uss/oisu;Js, dim/?t~dit. C/ien.s, 1 825, 2. 411 So, i afuste a Jo insit iss necssary o isio ssy a u I, s 0 0 O1 i d t a Is o I s o l u tio n W - h I:, i a th e O l 1 a l,:dii' h u l y 10 1:::s os.r.....1,,,.,,,t'ii.s 1,,,id0 o rd t soluto.~VA i: tl~tt w,l air,:,i,.,t=,;~,. I,',,;.~.... ANTIMONY. 83 The liquid should contain an excess of acid with about 20 parts of metallic tin, roll the also from first to last. (Gay-Lussac). product to a sheet, anti boil it for a long time As a modification of Gay-Lussac's process, with strong chlorhydric acid. The weight of Levol precipitates the antimony and tin to- the undissolved matter, after drying, will indigether upon a zinc rod, rinses off the metallic cate very nearly the proportion of antimony in powder which adheres to the zinc when the the alloy. Next melt very carefully a new porprecipitation is complete, and, without decant- tion of the alloy with pure tin, taken in such ing the solution of' chloride of zinc, treats the proportion that there shall be in the melted. mixed precipitate of tin and antimony with product 20 parts of tin to 1 of antimony. The strong chlorhydric acidl in order to dissolve the weighed metals should be wrapped in paper, tin. He then weighs the antimony and de- placed in a small IIessian crucible, covered termines the tin in the filtrate, as Sulphide of with powdered charcoal to prevent oxidation, Tin. In reply to the criticism of Elsner that and ignited for ten minutes in a hot fire. Afthis method is inexact, inasmuch as strong ter the crucible has cooled, brush the metallic chlorhydric acid dissolves some of the anti- globule, beat or roll it to a sheet. cut the sheet mony as well as the tin, Levol remarks that metal into several pieces, roll the pieces in in presence of chloride of zinc the action of paper as before, place them in a crucible, coythe acid upon antimony is materially lessened. er with powdered charcoal and melt during The method can hardly be expected, however, another space of ten minutes in order to ohto afford very accurate results in any event. tain a thoroughly homogeneous alloy. Brush Method D. A third modification of the the new globule, roll it to a thin sheet and cut process, applicable to cases where the propor- the product into a number of pieces. Weigh tion of antimony in the alloy is small, is the out a quantity for analysis, place it in a flask, Ibllowilng: - Fit to a small flask a cork carry- cover it with strong chlorhydric acid and boil ing a thistle tube and two other short tubes, the acid during at least two and a half hours. each bent at a right angle. Put the finely di- Dilute the acid with water, collect the finely vided alloy in the flask, replace the cork, and divided antimony on a weighed filter, dry and connect one of the delivery tubes with a source weigh. The tin in the original alloy is estimof' carbonic acid, and the other with several ated fi'om the difference. As tar as the estimU-tubes charged with small quantities of' red ation of' antimony is concerned the presence fihming nitric acid friee froml chlorine. Pour even of a large proportion of lead in the origenough strong clllorhydric acid into the flask inal alloy does no harm. to seal the thistle tube, and heat the mixture Properties. Precipitated antimony is a dull gently. The tin will (lissolve completely, and black powder, which may be dried at 100~ most of the antimony remain in the metallic without alteration. It fuses at a mnoderate red, state, though a part of' it goes off in the form heat. When strongly ignited in hydrogen gas of' antimloniulretted hydrogen gas. This gas a small part of it volatilizes without chemical will be oxidized, however, and the antimony change. Nitric acid oxidizes it with formation retained bv the nitric acid in the U-tubes. of' antimonious acid, mixed with more or less XWhen the alloy has dissolved, dilute the con- antimonic acid, according to the strength of tents of' the flask to solme definite volume with the nitric acid. Chlorhydric acid acts upon it recently boiled water, allow the mixture to set- but slowly, though an appreciable quantity of tie and determine the tin in a measured vol- it dissolves when left in contact with the acid ume of the clear liquor. Then filter the rest'fbr several days in open vessels. Dilute acid of' the liquid, wash the precipitate with acidu- dissolves more of it than concentrated, and lated water, place it in a porcelain crucible, cold acid more than the same acid when boiladd to it the contents of the U-tubes, evapo- ing. Acid charged with stannous chloride has rate to dlryness and weigh as Antimoniate of little or no action upon it. Antinony. It' the alloy contain arsenic as Princille 11. Oxidation by chlorine in alkawell as antimony, the residlue obtained by line solutions (Method A), by aqua regia, or evaporating the contents of' the U-tubes would a mixture of' chlorate of potassium and chlorbe treated, with the metallic prec'ipitate, as is hly(lrie acid (Method B), or by hot air (Methexplained under Antimnoniate of Sodium. odl C). Mllethod E. One of the oldest of' the pro- Applications. Separation of Sb from'As cesses dlependent on the principle now in ques- (B and A); of' Sb from Cu and Fe, especially in tion, is that of Chafidet (H. Rose, Handbuch, ores containing sulphur, and from Co and Ni; 1865, 2. 301). In this process the antimony (Method A). Separation of Sb from Ag, is kept in contact with a large proportion of Au and other noble metals. (Method C). stannous chloride in order that the solvent action of the chlorhydric acid upon the antimony may be hindered. After having determined 1. To separate Sbfrom Cu and Fe in sulphuthat the alloy contains nothing but antimony retted ores. Reduce the mineral to very fine and tin, the first step is to ascertain, approx- powder, diffuse it through a solution of caustic imately, the relative proportions of the two potash free from sulphuric acid, heat the limetals. To this end melt one part of the alloy quor and pass chlorine gas through it for sev3 34 ANTIMONY COMPOUNDS. eral hours. The sulphur oxidizes rapidly, in the bulb should never be heated intensely copper and iron are deposited as oxides and a until the reduction is deemed to be well nigh solution of' sulphate and antimoniate of potas- finished. sium obtained. Antimony may be estimated Principle II. Reduction of to metallic anin the filtrate as Sulphide of Antimony. (Ri- timony by iron, zinc or tin. See Antimony, vot, Beudant & 1Daguin, Comptes Rendus, sparing solubility of in chlorhydric acid. 1853, 37. 835). Arsenic Acid. 2. To separate Sb from As. Oxidize the Prilciple I. Reduction of by sulphur. mixture with chlorine as in No. 1, and remove Applications. Estimation of arsenic, by loss, the arsenic by precipitation, as Arseniate of in many metallic arseniates..Separation of Magnesiumn and Ammonium. Finally deter- Fe, Mn, Zn, Pb and Cu from arsenic acid. mine the antimony as Sulphide. Mlethod. Mix the powdered arseniate with 3. To separate Sb-from Co and Ni, add to pure, powdered sulphur in a porcelain crucible the dilute nitric acid solution of the three met- (Rose's reduction-crucible is best) and ignite als a large excess of caustic potash, heat the the mixture in a slow stream of hydrogen gas. mixture gently and pass chlorine gas into the The arsenic acid is reduced to metallic arsenic mixture until the precipitate is black. The and sulphide of arsenic, which escape in the precipitate contains the cobalt and nickel as form of gas, while the metal to be separated sesquioxides, while the antimony remains in so- from the arsenic remains in the crucible, and lution as antimoniate of potassium as in No. 1. is weighed as a sulphide. The apparatus (Rivot, etc., loc. cit.) must be so arranged that the arsenic funles may Method B. Oxidize the mixed metal or sul- be carried either into a chimney or into the phide by boiling with aqua regia, or with chlor- open air. A simple ignition of the arseniate hydric acid to which crystals of chlorate of with sulphur in a covered crucible would be potassium are frequently added, and remove sutficient in most cases to complete the reducthe arsenic acid by precipitation as Arseniate tion of the arseniate and to expel all the arof Magnesium and Ammonium. Determine senic, but the residual sulphide would then, be the antimony in the filtrate as Sulphide. left in an impure condition. The purpose of Method C. See Antimonious Acid, (vola- the current of hydrogen is to ensure the retility of). moval of any excess of sulphur from the residAntimony Compounds. ual sulphide. Principle I. Reduction of to the metallic In case the substance to be analyzed has state by hydrogen. been thoroughly mixed with sulphur, a single Applications. Estimation of antimony in ignition will complete the transformation of the,the sulphide or in any other compound of' an- arseniate to a sulphide, but it is always well, timony. after weighing, to mix the residue with a friesh iMethod. Weigh out a small quantity of the quantity of sulphur and to ignite a second, or dry sulphide, or other compound of antimony it' need be, a third time until the results of two to be tested, in a weighed bulb-tube of hard consecutive weighings are the same. In order glass; connect the tube with a hydrogen gen- that the amount of arsenic may be determined erator and pass a slow stream of dry hydrogen by the loss, the substance to be analyzed should through the tube. Heat the antimony com- be made anhydrous by heating it nearly to pound, gently at first, until the compound is redness, before weighing, though the reaction wholly reduced and the sulphur or other subli- with sulphur would take place with an airmate has been completely expelled from the dried arseniate as well as with one which had tube. Remove the lamp and continue the cur- been ignited. The crucible employed must not rent of hydrogen until the tube is cold, then only be of' porcelain but must be provided with hold the tube nearly upright for a moment to a porcelain cover; a platinum cover will not fill it with air and weigh it together with the answer since the arsenic fumtes would quickly antimony which it contains. A minute quan- render it brittle and ftiable. (II. Rose, Zeitsch. tity of antimony is apt to be carried forward analyt. Chem., 1862, 1. 413). either as antimoniuretted hydrogen, or through Principle II. Reduction of by chloride or volatilization of sulphide of antimony, in the sulphate of ammoniuml. current of gas, but most of it may be recovered Applications. Estimation of arsenic, by loss. by heating the narrow part of the tube to red- Separation of Na, K, Ba, and other metals ness with a second lamp placed beyond the from arsenic acid. bulb. A mirror of metallic antimony will be Milethod A. fWith Chloride of Ammonium. deposited near this second lamp, on the walls Alix the finely powdered arseniate with fromt 5 of the tube. When the operation is carefully to 8 times its weight of chloride of ammonium conducted the loss of antimony through vola- and heat the mixture in a covered porcelain tilization is so small that it hardly amounts to crucible until the weight of the residue rea quarter of one per cent of the total weight mains constant. Arseniates of the alkali metals of the antimony, even if no second lamp be em- are easily reduced in this way to the condition ploved, but it is easy to drive off half a per of chlorides. So, too, is arseniate of' barium, cent or more by careless heating. The matter though far less easily than the alkaline arsen ARSENIATES. 35 iates; but arseniate of magnesium cannot be possible quantity of water, with the aid of completely reduced. The arseniates of iron, gentle heat. Pour upon the solution a large cobalt and nickel heated with chloride of am' excess of alcohol of' 0.83 sp. gr., cover the nlonium in a stream of hydrogen yield metal- dish which contains the mixture and leave it lic iron, cobalt or nickel, as the case may be, at rest for 12 hours. Insoluble double sulbut the product is mixed with so much arsenic phates of ammonium and of the metals to be that no useful information can be obtained by separated are deposited as fine crystalline powweighing it. Arseniate of copper is reduced ders, while the arsenic acid and the excess of to metallic copper free from arsenic, but dur- sulphuric acid dissolve in the alcohol. Collect ing the ignition a quantity of chloride of cop- the precipitate upon a filter, wash it with alcoper escapes in the form of gas. The process hol, dry, ignite to drive off sulphate of amruoyields really useful results with arseniates of nium and weigh the residual sulphate of.-, the alkali-metals alone. (H. Rose, Pogg. Ann., or, in case it cannot be ignited without de73. 582; 74. 562; further Zeitsch. analyt. composition, determine the metal in some apChem., 1862, 1. 422). propriate way. The arsenic acid may be estiMlethod B. With Sulphate or Acid Sulphate mated from the loss or as Arseniate of Magof Ammonium. According to Finkener, acid nesiumn and Ammonium, after diluting with sulphate of ammonium decomposes many ar- water and expelling the alcohol. seniates far more quickly and completely than The mixture of sulphate of ammonium and chloride of ammonium. Though the process, sulphuric and arsenic acids must be dissolved in its present condition, is of no value to the in water before adding the alcohol, or a hard analyst, it is nevertheless worth describing, in mass will be formed impermeable to alcohol. the hope that it may be improved. Melt in a After the alcoholic mixture has stood 12 hours, porcelain crucible 7 or 8 times as much acid ether may be added to it to ensure the precipsulphate of ammonium as there is arseniate to itation of any traces of sulphates which the be decomposed, and add the latter, little by alcohol lmay have dissolved; though as a rule little, in fine powder to the melted salt. Fi- the addition of the ether is not necessary. nally heat the mixture until the excess of Basic Arseniate of Iron (Ferric amnmonium salt has all been driven off and Arseniate). weigh the metallic sulphate which remains in Principle. Insolubility in water and fixity the crucible. It would not be well to heat the when heated. mixture of' the almmonium salt and arseniate Applications. Estimation of arsenious and directly, since the mixture would froth vio- arsenic acids in solutions free from other sublently as it became fluid and some of it would stances precipitable by ammonia-water, by sesbe thrown out of the crucible. Normal sul- quichloride of iron, on addition of ammioniaphate of ammoniumr can be used instead of the water, or by carbonate of barium. Separation of acid salt, though the arsenic is rather mnore arsenic fiom Li, Na, K; Ba, Ca, Sr; Zn, Mn, readily expelled by the latter. The process Ni and Co. would be valuable, were it not that the crucible.Method A. The substance to be analyzed conis strongly acted upon by the melted amllmo- tains no non-volatile metals besides alkali-.metals. nium salt in such manner that the metallic (Berthier's method). Aiix the solution which sulphate to be weighed is contaminated with contains the arsenic acid with a measured quanother sulphates, formed by the union of' sul- tity of a standard solution of nitrate of sesphuric acid with the ingredients of the cruci- quioxide of iron and add ammonia-water to the ble, to such an extent that the results are mixture until a decided odor of ammonia perusually much too high. (H. Rose, Zeitsch. sists. In case the substance to be examined analyt. Chem., 1862, 1. 423). contains arsenious acid, it must first be treated Principle 111. Reduction of by cyanide of with aqua regia, or with nitric acid and chlopotassium. See Arsenic, volatility of. rate of potassium, to convert the arsenious acid Principle IV. Solubility in alcohol. into arsenic acid. If the precipitate produced Applications. Separation of arsenic acid by ammonia is not of a reddish-brown color anfrom most of' the arseniates. The arseniates other measured portion of the standard iron of iron and aluminum seem to be less easily solution must be added, and afterwards enough analyzed in this way than most other arsenl- amlmonia-water to make the solution alkaline. ates. The magnesium salt, on the other hand, After the mixture has stood for some time at a has been thus analyzed with great exactitude. gentle heat, collect the precipitate upon a filMelhod. Mix the arseniate to be analyzed ter, wash it with water and allow it to dry. with concentrated sulphuric acid in a platinum Place the dry precipitate together with the fildish, and keep the mixture slightly warm until ter ash in a platinum crucible, and heat it very it forms a thick syrup. Add to the syrup a gently fbr some time in order to expel ammoquantity of solid sulphate of ammonium equal nium compounds at a temperature lower than to that of the arseniate taken and again heat the that at which they can reduce arsenic acid. mixture until most of the excess of' sulphuric Increase the heat gradually and at last ignite acid has been expelled. Allow the mixture to the crucible intensely. The substance weighed cool and dissolve the viscous mass in the least is arsenic acid plus sesquioxide of iron, but the 36 ARSENIATES. weight of the latter is known from the quantity the arsenical solution contains barium, calcium, of the standard iron solution taken. Hence we strontium or any other metal whose arseniate have only to deduct the weight of ferric oxide is iinsoluble in ammonia-water. taken from the weight of the ignited precipi- Alethod B.' The substance to be analyzed tate to obtain the amount of arsenic acid con- contains other non-volatile mnetals besides alkali tained in the substance analyzed. metals. (V. Kobell's method). Mix the solution The best way of making the standard iron of arsenic acid with an excess of a standard solution is to dissolve fine iron wire (piano wire) solution of nitrate of iron, as in Method A, in hot nitric acid, to dilute the liquid to some but instead of aimlnonia-water add an excess definite voluIme (see Alkalimetry), and then to of carbonate of barium to throw down the badetermine how much sesquioxide of iron is con- sic at seniate of iron. If' the arsenical solution tained in 10 c. c. of' the liquid, by precipitation be strongly acid it should be nearly neutralized with ammonia-water (see Hydrate of' Iron). with carbonate of sodium before adding the In this case the presence of a slmall amount of' carbonate of barium. The liquid must be kept silica or other precipitable impurity in the iron clear, however, until the noment when the badoes no harm, since it is weighed with the ox- rium carbonate is mixed with it. The mixture ide of' iron both when the'strength of the iron must not be heated but should be left to stand for solution is determined and in the final arsenic several hours in the cold after the addition of the estimation. (Berthier). carbonate of bariullm. All theiron and all the arPrecautions. The process is applicable with senic will be thrown down in the form of basic sulphuric acid solutions as well as with solutions arseninte of iron, while an equivalent proporcharged with nitric or with chlorhydlric acid, tion of the carbonate of barium dissolves. but when sulphuric acid is present it is well to Wash the precipitate, which is of course mixed Ignite the crucible and precipitate a second with the excess of the carbonate of barium, by time or even a third time after weighing, until decantation with cold water, collect it upon a the weight remains constant, in order to be filter, dry, ignite gently for some time (see sure that all the sulphuric acid has been ex- Carbonate of Barium), and weigh. Dissolve pelled. This precaution is doubly necessary the weighed precipitate in strong chlorhydric since it would here be inadmissible to employ acid and determine the amount of' barium by carbonate of' alnmonitim (as is done with Sul- precipitation as Sulphate of Barium. From phate of Potassium), to remo'e the last traces the amount of sulphate of barium found, calof sulphuric acid. In case chlorhydric acid is culate the equivalent quantity of carbonate of present, the last traces of' chloride of ammnoni- barium, add the weight of this carbonate to the umn must be washed out of the precipitate lest weight of ferric oxide taken, and deduct the some of' the iron be volatilized as sesquichlo- suni fi'om the weight of the mixed precipitates ride, on ignition. In any event the precipitate of arseniate of iron andm carbonate of barium; must be cautiously heated. If the dry precip- the difference will give the amount of' arsenic itates were strongly ignited at once without any acid containemd in the substance anallyzed. preliminary warmling, some of the arsenic acid The method cannot be applied directly in would be reduced to the condition of arsenious presence of' metals precipitable by carbonate acid or even to metallic arsenic by the action of barium in the cold. So, too, if sulphuric of' amlnonium compounds contained in the pre- acid be plresent it must be removed by mueals cipitate, and the residue would weigh less than of' chloride of' barium before the analysis can it ought. Even with the most careful heating be proceeded with. a small amount of material is usually lost. Be- Properlies of the Precipitate. The success of sides this liability to loss through reduction of' Method A depends materially onthe state of agthe arsenic acid, an objection to the process is gregation o' the precipitate. It must be a highly found in the fact that it is sometimes very hard basic compound, neither slimy fior soluble in amto wash the precipitate completely, and that the mlonia-water. The composition of the precipitate last portions of wash water are apt to dissolve obtained in Berthier's process may be taken as some arseniate of irony in which event the wash varying fiolm 2F'e03, As205 to 16Fe()03, As water acquires a faint reddish color. This dif'- 0. The more basic it is the better. The 16 ficulty may be avAided, however, by washing Fe203 salt is as insoluble in anlmmonia-water with dilute ammonia-water. and as little slimy as ferric hydrate. It is to In spite of the greater bulk of the precipi- be observed that normal arseniate of iron tate it is best to employ a large excess of the (2Fe2O3, 3H20, 3As205+9I120), as obtained by standard solution of' iron, for the highly basic mixilng a solution of ferric chloride with one arseniates of iron -are less slimy and are far of ordinary arseniate of' sodium, is a white more easily washed than those which contain slimy precipitate soluble in ammllonia-water and a larger proportion of arsenic. A good rule of no use to the analyst. Pfaf' (Ilandbu'ch anis to take one part by weight of metallic iron alyt. Chem., Altona, 1824, 1. 221 and 2. pp. 335, for every two parts of arsenious acid which the 344, 459, 476, 478, etc.), who thought highly substance to be analyzed is supposed to con- of the principle now in question, as a means of tain. separating iron fromn nickel and from mrangaThe process is of course inapplicable when nese, describes the basic arseniate of iron as a ARSENIATES. 37 white pulverulent precipitate which falls im- the precipitate upon a filter, wash and dry it, mediately, even in presence of' 25,000.parts of ignite it gently apart from the filter, in a porcewater.. According to him, it is compact rather lain crucible, weigh and finally determine the than gelatinous, and mlay be readily collected amount of lead contained in the precipitate, as and washed; it is mtuch more difficultly soluble Sulphate of Lead. Another method of procethan the benzoate or succinate of iron,-5 dure is to dissolve the substance to be analyzed times less soluble than the last named salt. in nitric acid, to mix the solution with an excess Pfaff obtained his precipitates by adding Inono- of nitrate of lead, and to carefully evaporate arseniate of potassium to solutions of ferric the mixture to dryness in order to expel the salts. - It is worth inquiring whetherthe pre- free nitric acid. The dry residue, consisting cipitate thus thrown down Illight not be weighed of arseniate of lead, nitrate of lead, and directly and then reduced wiith sulphur by H. nitrate of the metal previously combined with Rose's method (see Arsenic Acid), in order to arsenious acid, is then washed with water and obtain the proportion of iron and of arsenic the arseniate of lead collected on a filter. contained in it. The excess of lead must of course be removed Arseniate of Lead. from the filtrate before proceedin.., to determine Principle 1. Fixity when heated to low the other metal or metals contained in it. redness. Instead of evaporating the nitric acid solution Applications. Estimation of arsenious and of arsenic it may be carefully neutralized with arsenic acids in aqueous or nitric acid solu- an alkali and then mixed with acetate of lead. tions free from chlorhydric acid and non-vola- Unlike nitric acid, acetic acid dissolves scarcely tile substances, as well as ammnoniulm salts and any arseniate of lead, hence arsenic acid may other reducing agents. Valuation of arsen- be completely precipitated by adding acetate ious acid and metallic arsenic. of lead to a solution of free arsenic acid without AMethod. Weigh a quantity of the solution need of neutralizing or evaporating the liquid. to be examinedl in a tolerably large porcelain Though inconvenient and almost obsolete, the crucible, and, in case the solution contains no process may still be employed in soile cases. arsenious acid, mix with it directly a weighed It is inapplicable in presence of chlorhydric quantity of' pure, recently ignitel, oxide of acid or a chloride, for in that case insoluble or lead. Take 5 or 6 times as much oxi(le of almost insoluble double compounds of chloride lead as there is supposed to be arsenic acid in and arseniate of lead would be precipitated. the substance, and stir it into the solution with Properties. Pure arseniate of lead is a white a fine glass rodl. Evaporate the mixture to powder, yellowish when hot, which softens at dryness on a water bath, heat the residue to a low red heat. It fuses when heated strongly low redness and maintain it at that tenlpera- and is then apt to suffer slight decomposition, ture for some time. Finally, weigh the residue a small proportion of arsenic acid being lost in an(l deduct the weight of the oxide of lead the form of arsenious acid and free oxygen. taken, in order to obtain the weight of the ar- The substance actually weighed in the first of senic acid. The process affords excellent the two processes above described is not pure results provided the residue is not heated too arseniate of lead, but a mixture of that strongly. - The oxide of lead is best pre- substance with free oxide of lead. The product pared by igniting pure nitrate of' lead. obtained by the second process is a variable In determining the value of any sample of mixture of' tri- and di-arseniate of lead. metallic arsenic or arsenious acid, or in analyz- Arseniate of Magnesium and ing a solution of arsenious acid, dissolve the Ammonium. substance in nitric acid, or mix the solution Principle. Sparing solubility in ammoniated with this acid, and evaporate the liquor to a water, and fixity at 100~. small bulk before adding the oxide of lead. Applications. Estimation of arsenic acid in The dry residue must be ignited with special all solutions free from substances permanently care in this case in order to avoid loss through precipitable by ammonia or by a magnesium decrepitation of' the nitrate of lead. The cru- salt. Separation of arsenic acid from all acids cible should be placed upon a sand bath at first which form soluble magnesium salts. Separain order to ensure a gradual elevation of the tion of arsenic from arsenionmolybdate of amntemperature, and should be kept covered. A moniurn; from K, Na; Al, Zn, Cd; Mn, Ni, similar remark applies of course to all cases in Co, Fe; Cu and Sb.' Separation of arsenious which nitric acid is present. from arsenic acid and of Mg from. K and Na. Principle 11. Insolubility in water or acetic.Method A. Absence of substances precipiacid. table by ammonia or by magnesia. Add to the Applications. Separation of lead from many solution which contains arsenic acid ammoniametals-among which may be mentioned Na, water in distinct excess, and stir into the liquid K, Li; Zn, Cd and Cu. (Pftff). a mixture of sulphate of magnesium, chloride Mlethod. Mix the solution of arsenic acid, of ammonium and ammonia (see Sulphate of which must either be neutral or slightly acid- Magnesium) as long as a precipitate continues ulated with acetic acid, with an excess of a to fall. This "magnesia-mixture" consists of solution of acetate or nitrate of lead. Collect a solution of sulphate of magnesium charged 38 ARSENIATES. with so much chloride of ammonium that no of composition represented by the formula magnesia can be precipitated from it by ammo- 2MgO, (NH4)20, As205 + 12H1120. When nia-water. Leave the liquid and precipitate at heated to 105~-110~ it loses 11 equivalents of rest for 12 or 24 hours in the cold. Then water, so that the formula of the compound collect the precipitate upon a weighed filter actually weighed is 2MgO, (NH4)20, As202 which has been dried at 105~-110~. - The + H20:liquid should smell strongly of ammonia, af- 2gO. 80.... 21.05 ter the addition of the magnesia-mixture, but (NHO.... 52.... 13.68 should contain no more chloride of amnmonium H As 230 60.53 or other ammonium salt than is absolutely necessary to prevent the precipitation of hydrate 380 100.00 of magnesium. The precipitate is in fact con- The precipitate might be dried at 1000 if only siderably more soluble in solutions of ammo- time enough were allowed. But at the teinnium salts than in pure water. The liquid perature of a water bath, the precipitate remust never be heated, and time enough must tains 2 or 3 equivalents of water with considbe allowed for the precipitate to separate from erable force. it completely before filtering. Since the pre- On ignition the compound loses water and cipitate is by no means absolutely insoluble in ammonia, and changes to arseniate of magneamnmoniated water, it must be washed with sium 2MlgO, As O4. It is not impossible to extreme care. In order to avoid using any obtain good results by igniting the precipitate more water than is absolutely necessary for the and weighing the residue as Levol (Annales washing, transfer the precipitate from the Chim. et Phys., (3) 17. 501), the inventor of beaker to the filter by means of portions of the the process, originally proposed. Wittstein filtrate, and afterwards wash it upon the filter (Zeitsch. analyt. Chiem., 1863, 2. 20), in reaswiih small quantities of a mixture of 1 part setting the propriety of this course, directs strong aminonia-water and 3 parts water until that the crucible be placed at first on a sand the washings give only a slight opalescence bath and heated with a small spirit lamp until when acidulated with nitric acid and mixed the odor of ammonia is no longer perceptible. with nitrate of silver. Dry at 105~-1100 and Then remove the crucible from the bath and weigh. heat it over the free flame more and more The process yieldssatisfactory results, though strongly, almost to redness. H. Rose admits on account of the solubility of' the precipitate that by raising the temperature of the precipthey are always somewhat lower than theory itate very gradually during several hours, from riequires. According to Fresenius, this error 100 to 400%, and then as gradually fiom dull may be partially corrected, as fobllows:-Measure to bright redness, all the water and ammonia the filtrate, without the wvashings, and for may be expelled without losing any arsenic every 16 c. c. of' the liquid add 1 m. g. to the through the reducing action of the ammonia. weight of the precipitate.'Tle wash water But in case the dry precipitate is exposed must not be measured since it cannot be re- directly to a high temnperature, a very considergarded as a saturated solution of the double able portion of the arsenic is lost. Accordarseniate. ing to his experiments, if the precipitate Instead of washing with ammoniated water, be gently heated for a short time and then as above, I-I. Rose directs that the solution to brought to redness, no more than 96 per cent of be examined be concentrated to a small bulk, the arsenic contained in the magnesium salt supersaturated with ammnonia-water and mixed will ever be obtained, while results as low as with one quarter its volulne of strong alcohol 95 and 93 per cent are common. If the prebefore adding the magnesia mixture, and that cipitate be exposed at once to a red heat, only the precipitate, after standing 48 hours in its about 88 per cent of the arsenic is left to be liquor, be washed with a mixture of 4 vols. weighed. The precipitate might be ignited water, 1 vol. absolute alcohol, and a not too with bisulphate of ammnonium and reduced to small quantity of ammonia-water. the condition of sulphate of magnesium (see In case any portion of the arsenic in the Arsenic Acid) before weighing, were it not for original solution is not already in the form of the errors introduced by the action of the amarsenic acid or an arseniate, the solution must moniumr salt upon the material of the crucible. be gently heated in a flask with nitric or chlor- The double arseniate cannot be completely rehydric acid, and small portions of chlorate of duced, however, by igniting it with sulphur or potassium thrown into the liquid until the lat- with carbonate of ammonium, or in a current ter emits a strong odor of chlorous acid. TWhen of hydrogen gas. (H. Rose, Zeitsch. analyt. all the arsenic acid has thus been oxidized, Chem., 1862, 1. pp. 418, 424). heat the liquid gently to drive off' most of the Arseniate of magnesium and ammonium is chlorous acid, and proceed with the addition much more soluble in pure water than in dilute of ammnonia-water and magnesia mixture as ammonia-water or amnironiated spirit. It is before. more soluble in aqueous solutions of anmmoniumn Properties, The double arseniate is a white, salts than in water, though the solvent power sonlewhat transparent, crystalline precipitate, of these salts is diminished by the presence of ARSENIATES. 39 free ammonia. At the temperature of 15~ dish, roast the residue in a muffle to destroy according to Fresenius (Zeitsch. analyt. Chem., sulphur and organic matter, fuse with c'lbon1864, 3. 207), 1 part of the salt (reckoned as ate of sodium, dissolve in chlorhydric acld and dried at 1000) dissolves in 2656 parts of water; precipitate Hydrate of Aluminum. in 15038 parts of' ammoniated water, made by Method D. Separation of Arsenic from Anmixing I part of ammonia-water, of 0.96 sp. timony. Proceed as in Method C. But immegr., with 3 parts of water; in 1315 parts of a diately after adding the tartaric acid mix with dilute and 844 parts of a strong solution of the solution a large quantity of chloride of chloride of ammonium (containing respectively ammonium, before proceeding to saturate with 70 and 7 parts of water to 1 part of chloride ammonia-water. Any precipitate produced on of ammonium); and in 2871 parts of a solution the addition of the ammonia-water would go made by mixing 60 parts of water, 10 parts of to show that the quantity of chloride of ammoammonia-water, of 0.96 sp. gr., and 1 part of nium or of tartaric acid previously added was chloride of ammonium. insufficient, and that a further portion of one Method B. Separation of Arsenic Acidfrom or the other of these agents must be added Arsenious Acid. Mix the tolerably dilute so- before adding the magnesia mixture. - In lution of the two acids with a large quantity case the substance to be analyzed is an alloy, of chloride of anmmonium and then precipitate or a mixture of sulphides, oxidize it in the the arsenic acid with magnesia mixture, as in manner described under Antimony. Finally A. The arsenious acid may be determined determine the antimony in the filtrate as Sulin the filtrate as Sulphide of Arsenic. If the phide of Antimony. original solution be too concentrated sonle lMethod E. Determination of Arsenic Acid arsenite of magnesium will go down with the in a precipitate of Arseniomolybdate of Ammodouble arseniate. To be sure of the purity of nium. Dissolve the precipitate upon the filter the latter it is well to dissolve it in chlorhydric in ammonia-water, wash the paper thoroughly acid, after weighing. and to test the solution and add enough chlorhydric acid to the soluwith sulphuretted hydrogen. The immediate tion to neutralize a good part of the ammonia. formation of' a precipitate would indicate the Take care, however, to leave the solution clear presence of some arsenious acid, and smelling strongly of ammonia. Finally Method C. Separation of Arsenic Acid-from add the magnesia mixture and proceed as in Cd, Zn, Al, Ur, Mn, Fe, Co, Ni and Cu. Method A. Dissolve the substance to be analyzed in chlor- Method F. To separate 3Magnesium from hydric or nitric acid, and in case the arsenic is Potassium or Sodium, mix the solution with a not all in the condition of arsenic acid, bring quantity of chloride of ammonium, add ammoit to that state by means of chlorate of potassium nia-water in excess, and a solution of arseniate as in Method A. Mix the tolerably dilute of ammonium as long as any precipitate falls. solution with enough tartaric acid to prevent Allow the mixture to stand and treat the prethe formation of a precipitate by ammonia- cipitate as in A. To determine the potaswater, and then with ammonia-water in excess. sium or sodium, evaporate the filtrate from the Finally add the mixture of sulphate of magd double arseniate to dryness under a chimney nesium, chloride of ammonium and ammonia, and ignite the dry residue. The excess of and proceed as in Method A. arsenic acid goes off, together with the arlinoSince the precipitate, in this case, is liable nium salts, while the alkali metals are left as to be contaminated with a difficultly soluble chlorides, always contaminated, however, with basic tartrate of magnesiumn, it is best, after a little chloride of magnesium. Magnesia mnay washing once with the ammoniated water, to be separated more quickly from the alkalies in redissolve it in chlorhydric acid, to mix the solu- this way than by means of the double Phostion with a very small quantity of tartaric acid, phate of Magnesium and Ammonium, but the to supersaturate with ammonia and allow the latter process is more accurate, and on the whole to stand during at least 12 hours. The whole, more convenient than the one just depure precipitate thus obtained nmay then be scribed. collected, washed, dried and weighed. The Arseniate of dinoxide of Merprocess is better suited for separating large cury. than small quantities of arsenic acid from the Principle. Insolubility in water. metals in question, for if the proportion of Applications. Separation of' arsenic acid arsenic be very small the amount of arseniate from Na, K; Ba, Ca, Sr; NIg, Cd, Zn; Co, of magnesium and ammonium which is neces- Ni, Pb and Cu. sarily dissolved in the process of' washing may Mlethod. Same as that described under exert a very considerable influence on the Phosphate of dinoxide of Mercury, excepting accuracy of the result. that the arsenic acid cannot be determiniled in With the exception of aluminum, the vari- the insoluble residue in the way that phosphoous metals maly be thrown down as Sulphides ric acid is determined. from the original filtrate, by means of sulphy- Arseniate of Potassium (or of drate of ammonium. To determine aluminum, Sodi u m). evaporate the filtrate to dryness in a platinum Principle. Solubility in water, 40 ARSENIATES. Applications. (A). Separation of arsenic Applications. Estimation of tin and of aracid from Fe, Mn and Cu; less completely senic in commnercial stannate of sodium. from Zn. (B). Separation of arsenic acid MAethod. Alix a weighed quantity of the fiom many metals, including those of the stannate to be tested with a weigfhed quantity alkaline earths. of arseniate of sodium, more than sufficient to Mlethod A. Boil the finely powdered, un- precipitate the whole of the tin. Ad(d an ignited arseniate of iron, or other metal, for excess of' nitric acid to the mixture and boil some time with a solution of a caustic alkali, the liquid; collect the precipitate upon a filter, or less advantageously with a solution of an wash, dry, ignite and weigh. Determine also alkaline carbonate. Dilute the liquor with the arsenic acid in the filtrate by precipitating water and filter it in order to separate the it as Arseniate of Magnesium and Alllllnonin. soluble arseniate of potassium or of sodium The amount of tin is found from the weight from the insoluble oxide or carbonate which of the ignited arseniate of tin, and that of the remains undissolved. - Since oxide of' zinc arsenic by adding together the quantities of is soluble in caustic alkalies, arseniate of zinc arsenic found in tlhe arseniate of tin and tlie must always be treated with a carbonated arseniate of magnesium and ammloniumn, -and alkali. It is not easily decomnpose(l in any subtracting from this sum the quantity of event. (V. Kobell; H. Rose, Zeitsch. analyt. arsenic added in the form of arseniate of Chem., 1862, 1. 425). It will not answer to sodium. simply precipitate the solution of a metallic Properties. The composition of the washed arseniate with an excess of a solution of ear- precipitate may be represented by the forlmula bonate of potassilmO or of caustic potash, since 2SnO., AsO,2-+t- 10H120; and that of the ignite(d more or less arsenic would almost always be precipitate by thle formula 2SnO2, As.Ox. (E. retained by the precipitate. The method Hleffely, Phil. Mlaqt., (4.) 10. 291). is inapplicable for the analysis of native arsen- The same principle is involved in a method late of iron, or of the artificial product after it of estimating arsenic and tin in an alloy of has been ignited. Only a part of the arsenic the two metals, proposed by Levol (Ann. can be removed fiom these substances by boil- Chinm. et Phys., (3.) 16. 493). Levol has found ing alkali. (Berzelius). that when an alloy of tin and arsenic, containMlethod B. Mix the powdered substance to ing less than 5 per cent of arsenic is boiled be analyzed with 3 parts of dry carbonate of with nitric acid, the whole of the alrsenic will sodiumn, or better, with 3 parts of a mixture of remain in insoluble combination with the oxide equal equivalents of the carbonates of sodium of tin, in the form of basic arseniate of tin. and potassium, and melt the mixture at the Even when the alloy contains 8 per cent of blast lanip. Thle mixture of carbonate of arsenic, little or no arsenic will remain dissodium andi carbonate of potassium melts more solved in the excess of' nitric acid, but when easily than either carbonate taken by itself. the proportion of arsenic exceeds 8 per cent When the mixture has been thoroughly fused, some of it always goes into solution. The all the arsenic acid will be found in the condi- process of analysis is as follows:-Treat the tion of arseniate of' sodium, and the metals to finely laminated alloy with tolerably strong be separated( in the form of insoluble carbon- nitric acid, first in the cold, in order that stanates or oxides. Dissolve the fused nmass in nous oxide may be forme1d, and afterwards at water, separAte the soluble arseniate by filtra- the temperature of' boiling to convert the stantion and estimate the arsenic acid as Arseniate nous into stannic oxide. Collect the arseniato of I1agnesiunm and Ammlonium. of tin upon a filter, dry andt weigh it and The plarocess is objectionable, inasmuch as no finally heat it in a current of hydrogen to devessels can be fonbud proper to be used for the termuine the proportion of Arsenic. In case fusion. There would be danger of destroying the filtrate also contains arsenic, estimhate the a platinum crucible tlrough the combined ac- quantity by precipitating as Arsoniate of' Magtion of an alkaline arseniate and reducing nesiurn and Ammlnoniuin or in some other gases from the lanmp; if a porcelain crucible is appropriate way. used its glazing will be dissolved by the melted Level has applied this method to the estialkali, andll the solution of arseniate of sodium mation of arsenic in metallic copper. IHTe diswill thus become contaminated with aluminum solves the metal in nitric acid, mlixes the soland silicon. The risk of destroying a plati- ution with a solution of stannous nitrate, prenumn crucible is lessened, and the fusibility of pared in the cold. and boils the mixture. the flux increased, by mixing a quantity of Stannic arseniate is thrown down from the nitrate of potassium with the carbonate; but hot liquor, and the proportion of arsenic conthe process cannot be commended unless the tained in it is estimated in the manner already proportion of arsenic in the mixture to be an- described. alyzed is very small. Arseniate of Uranium. Arseniate of Tin (SnO2). Principle. Insolubilityin water and acetic Principle. Insolubility of the compound in acid. water and dilute nitric acid, and fixity when Applications. Estimation of arsenic in arignited. senic and arsenious acids and in arseniates aut ARSENIC. 41 arsenites of the alkali-metals. (Method A). water charged with about as much ammonia Estimation of arsenic as in A, and also in and acetic acid as were previously added to presence of Ba, Sr, Ca, Mg and Zn; but not the arseniate of sodium. Pour uranium soluin presence of metals, such as Cu, which are tion from the burette into this acidulated water precipitated by ferrocyanide of potassium until a drop of the solution gives the red brown (Method B). reaction with ferrocyanide of potassiumn. Alethod A. Gravimetric. Boil the solution A certain excess of the uranium solution has of arsenic acid with an excess of potash lye, always to be used in order to obtain the reacsupersaturate the mixture with acetic acid, and tion with ferrocyanide of potassium, and the puradd to the clear solution an excess of acetate pose of the second titration is to determine the of uranium. Wash the precipitate with a amount of this excess for the particular degree of very dilute solution of chloride of ammonium dilution involved in the given case. The number and finally remove the chloride of ammonium of c. c. of uranium solution employed in the by washing with a mixture of 1 volume of al- second titration must be subtracted from the cohol and 8 or 9 volumes of water. Dry the quantity first used, in order to obtain the true precipitate at a gentle heat upon a water bath value of the solution with reference to arsenic and ignite it moderately in a porcelain crucible acid. To be sure of the final reaction, spread for a long time. The crucible must not be out a drop of the liquor upon porcelain and heated to redness. place a drop of the ferrocyanide in the centre Precautions. The solution to be analyzed of the spot; if the titration be finished a dismust be free from ammonium salts; if ammo- tinct reddish brown line will form where the nium salts were present ammonia would be two liquids meet. - Instead of arseniate thrown down in combination with the precipi- of sodium pure arsenious acid may be used for tate and would reduce some of the arsenic standardizing the liquid; after having been acid when the precipitate came to be heated. weighed it must be converted into arsenic acid No metals of the alkaline earths or other by boiling with fiming nitric acid. substances precipitable by arsenic acid should In an actual analysis, the substance, after havbe present. The solution must be perfectly ing been brought to the condition of arsenic clear after the addition of acetic acid. Pre- acid, is treated with ammonia water and acetic cipitated arseniate of uranium is apt to be so acid, and the clear solution titrated with the finely divided that it would pass through the uranium solution, as above described. The pores of the filter if simply washed with water. second titration, to determine the correction This difficulty is avoided by washing with for dilution, must be made in every analysis chloride of ammonium instead of water. As precisely as when the test liquor is standarda rule the method is less convenient than that ized. In practised hands the process is said depending on the insolubility of Arseniate of to yield good results. A solution of nitrate of iMagnesium and Aummoniumn. (Werther, Journ. uranium is preferable to the acetate, since the Prakt. Chem., 43. 346). latter gradually decomposes when exposed to Properties. The precipitate first thrown light. (Bedeker, Annal. Chem. und Pharm., down, of composition 2Ur0,,, IHO0, As20O, is 117. 195). insoluble in water, acetic acid and saline solu- Arsenic. [Compare Arsenious Acid]. tions, particularly in a solution of chloride of Arsenic is weighed either as metallic arsenic, ammonium. The composition of the residue as arseniate of iron (Fe03), arseniate of' lead, left after ignition may be represented by the arseniate of uranium, arseniate of' magnesium formula 2Ur03s, As2 0. The proportion of and ammonium, or as tersulphlide of arsenic. It arsenic can be calculated from it directly. may be estimated by loss either as As, as AsCI,, MIethod B. Volumetric. Prepare a solution or as AsS23, by titration with oxidizing agents, of nitrate of sesquioxide of uranium of' such as will be explained under arsenious acid, and strength that a litre shall contain about 20 by indirect methods to be exllained below. grammes of the sesquioxi(le. This solution (See also the finding list in Appendix). should contain as little free acid as possible. Principle I. Sparing solubility of' the metal To standardize the liquor weigh out a quantity in chlorhydrie acid. of pure arseniate of sodium, dissolve it in Applications. Separation of arsenic froml water, supersaturate the solution with ammonia tin. water, and finally make the liquor distinctly Method. Heat the granulated or laminated acid with acetic acid. Slowly'pour the ura- alloy gently in a mixture of 1 equivalent of Mium solution from. a burette into the acidulated nitric acid and 9 equivalents of chlorhydric solution of arsenic acid, with constant stirring, acid. The tin alone will dissolve, while metaluntil a drop of the liquid placed upon a porce- lie arsenic is left in the form of a powder, which lain plate gives a reddish brown coloration may be collected upon a I ared filter, washed, first when tested with ferrocyanide of potassium. with cold recently boiled water, then with alcoNote the quantity of uranium solution used; hol, and dried at 100~. The acid must not be mark the height of the liquid in the beaker by used in much larger proportion than 1 equivmeans of' a strip of gummed paper; empty and alent nitric acid and 9 equivalents chlorhydric wash the beaker and fill it to the mark with acid to 8 equivalents of' the arseniated tin. 42 ARSENIC. When the acids are used in these proportions of the volatilized arsenic may thus be made to the solution of the tin is unaccompanied by combine with copper in one operation. the evolution of gas, the chlorides of tin and Since the tin always retains some arsenic, it of ammnonium being the sole products besides must be dissolved in chlorbhyvdric aciid, and the water. mixture of hydrogen and arseniuretted hv dro4Sn + HNO,3 + 9C1i = 4SnC12 + NH4C1 + 3H20. gen evolved, after having been frieed from chlor(Gay-Lussac, Annales Chimie et Phys., [3.] hydric acid by washing with soda lye, must be 23. 228). made to pass into a solution of nitrate of silver. For the separation of arsenic from an alloy The arsenic in the gas is thus converted into of tin, antimony and arsenic see under Anti- arsenious acid while metallic silver is thrown mony, Principle I., No. 3. down. In case any solid arseniuretted hydroPrinciple II. Volatility. gen (or insoluble alloy of'arsenic) is left iundisApplications. Separation of arsenic from solved by the chlorhydric acid, it must be disantimony and from tin. solved in a few drops of nitric acid. The 3Method A. To separate arsenic from anti- excess of silver is then thrown down as Chlomony weigh out some of the finely divided ride of Silver; the filtered arsenious acid is alloy in a bulb tube, mix with it 2 parts of' mixed with the nitric acid solution of the solid carbonate of sodium and 2 parts of cyanide of residue, and the arsenic precipitated as Sulphilde potassium, and connect the tube with a source of Arsenic. - As a substitute for this of dry carbonic acid. After all the air has been method of procedure Berzelius recommendls expelled, heat the tube gently for a while, that the arseniuretted hydrogen from the soluafterwards gradually increase the heat to in- tion of the tin, be decomposed by passing it tense ignition, and continue to heat until all through a weighed quantity of red-hot copper, the arsenic has been volatilized and driven and that the solid residue be neglected. from the tube. After removing the lamp, con- 3. The old method of separating arsenic tinue the current of carbonic acid until the from certain alloys by roasting the mixture in tube has become cold, then lixiviate the con- a current of air until the odor of garlic was no tents of the tube, first with a mixture of equal longer perceptible, or heating with admixture parts of strong alcohol and water and after- of charcoal, in case the arsenic were present wards with water. Finally, dry and weigh as arsenic acid, gave only approxillative rethe residual antimony. The quantity of arse- sults. For that matter, metals like nickel, nic is inferred from the loss. The method is cobalt and iron, always retain a certain porsaid to yield only approximate results. tion of the arsenic. (Pfaff, Ilandbuch analyt. In case it is desired to dispense with the car- Chem., 1825, 2. 426), bonate of sodium and cyanide of potassium and Principle III. Oxidation by chlorine in to fuse the alloy by itself' in the current of alkaline solutions (Method A), by aqua regia, carbonic acid, special care must be exercised by a mixture of Chlorate of Potassium and in heating the alloy or much antimony will be nitric or chlorhydric acid (MAethod B), or by driven off' with the arsenic. Nitrate of Potassium. 2. To separate arsenic from tin. Oxidize Applications, Separation of As from Fe, the alloy with nitric acid in a beaker, wash the Co, Ni and Cu (Method A); from Sb (Methproduct into a porcelain crucible with a solu- od B); from Ca, Ba, Sr; Mg, Zn, Cd, Mn, tion of carbonate of sodium, evaporate to dry- Fe, Co, Ni; Ag, Pb, I-I, Cu, Bi (Method C). ness on a water bath, miix the dry residue with Method A. Oxidalion bhy Chlorine. Same equal parts of carbonate of sodium and cyanide as the methods described under Antimony. of potassium, and melt the mixture. All the A solution of arseniate of potassium is proarsenic is driven off in the form of vapor while duced. the tin remains, partly in the form of metal and Mllethod B. Oxidation by A qua re/ia or by a partly as oxide, and as stannate of sodium. mixture of Chlorate of Potassium and Nitric The tin is estimated as Oxide of Tin and the or Chlorhyqdric Acid. Same as the methods arsenic by the difference. described under Antimony. In order to avoid In case the substance to be analyzed is ar- the volatilization of terchloride of arsenic, seniate of tin, weigh out some of it in a glass care must be taken never to evaporate a soluboat, introduce the boat into a wide glass tube, tion which contains arsenious acid and chlorhvpass a current of hydrogen through the tube dric acid unless free chlorine or ehlorous,or and heat the tube to dull redness. MSetallic nitric acid be also present. arsenic sublimes and is deposited as a coating MI'ethod C. Oxidation by Aitrate of Potasupon the colder part of the tube. Its weight siumn. Fuse the alloy with a mixture of'3 parts is determined by cutting off that part of' the of carbonate of sodium and 3 parts of' nitrate tube and weighing it first with the arsenic and of potassium. Boil the fused malss with water, again after the arsenic has been dissolved. In separate the soluble alkaline arseniates fromn order to retain any arsenic which might go the insoluble oxides and. carbonates, by filtraforward as arseniuretted hydrogen, it is well to tion and washing with hot water, and determine lead the escaping gases through a short column the arsenic as Arseniate of Magnesiuml and of weighed hot metallic copper. Or the whole Amnmoniumn. - In case the proportion of ARSENIOUS ACID. 43 arsenic in the alloy is not large, the fusion may acidulate with acetic acid; filter, to remove be effected in a platinum crucible, in the bot? om the sulphide of arsenic which is thrown down, of which a layer of carbonate of potassium has supersaturate the filtrate with bicarbonate of been placed before introducing the mixture. sodium, and proceed with the titration. The When a porcelain crucible is used, part of it is substance to be analyzed and the carbonate of dissolved by the melted alkali and the fused sodium must be wholly free from sulphurous mass is consequently contaminated with silicon acid, hyposulphites and other substances capaand aluminum. (Woehler, Pogg. Ann., 25. ble of acting upon iodine. (F. Mohr, Titrir302). methode, 1855, p. 295). In order to avoid loss of arsenic by volatil- To separate arsenious from arsenic acid deization, alloys rich in arsenic had better be termine the amount of arsenious acid in one oxidized with nitric acid in the first place and portion of' the substance, by titration with the dry residue subsequently fused with 3 parts iodine as above, then oxidize the arsenious acid of carbonate of sodium and 1 part of nitrate in another portion by means of nitric acid and of potassium. chlorate of potassium (Method F), or by Arsenious Acid. [Compare Arsenic chlorine in alkaline solution, and determine Acid]. the total amount of arsenic as Arseniate of Principle. Oxidation by Iodine (A), by Magnesium and Ammonium. Calculate the Chlorine (B), by Bichromate (C), Perman- amount of arsenic acid from the difference. ganate (D), Nitrate (E), or Chlorate (F), Mlethod B. Oxidation by Chlorine. of Potassium; by aqua regia or by Salts of As2o3 + 2u20 + 4Cl = As2o5 + 4HC1. Gold (G). 1. By chlorine acting in an acid solution. Applications. Methods A B C and G The old method of chlorimetry devised by may be employed for determining arsenious Gay-Lussac (Annal. der Chem. und Pharm., acid in arsenites and in the commercial acid; 18. 18), which was formerly much used, defor separating arsenious from arsenic acid and pends upon the action of chlorine upon arsenfor determining arsenic in boiled clorhydric ious acid in chlorhydric acid solution. acid solutions of sulphide of arsenic. Method A weighed quantity of pure arsenious acid A is well suited for determining the amount was dissolved in hot concentrated chlorhydric of arsenious acid in commercial realgar and acid, and the solution colored with two or three.orpiment. It may be used for estimating iodine, drops of a solution of indigo in sulphuric acid. and also for standardizing iodine solutions,- A weighed quantity of the bleaching powder as will be explained under Iodine, - by which to be tested was mixed with water to a definite to estimate Chlorine, Bromine, Ozone-; Hypo- volume, and portions of the milky liquor were chlorous, Chloric, Chromic, Sulphurous and poured from a burette into the solution of arSulphydric Acids; the higher Oxides of Man- senious acid, until the blue color of the indigo ganese, Cobalt and Nickel; in short, all oxides disappeared. - The process is distinctly which evolve chlorine when heated with chlor- inferior in several respects to that in which the hydric acid; and tin in Stannous salts. chlorinated liquor is made to act upon arsenMethod B is largely used for estimating the ious acid in alkaline solution. Notably, bevalue of bleaching salts. - Method E serves cause the oxidizing power of' chlorine is less to separate arsenic from Ca, Ba, Sr; Mg, Cd, decided in presence of an acid than in that of Zn, Mn, Fe, Co, Ni; Ag, Pb, Hg, Cu and Bi. an alkali, and because some chlorine is always Method F may be used for determining nitric set free by the action of the acid and lost, at acid, as well as for converting arsenious into the moment when the bleaching powder soluarsenic acid in the ordinary course of' analysis. tion comes in contact with the arsenical liquor. Method A. Oxidation by Iodine in Alkaline As an indicator, moreover, indigo is inferior to Solutions. the mixture of iodide of potassium and starch As.203 + 2Na20 + 41 = As20r + 4NaI. employed in the alkaline process. In practice, Weigh out as much of the substance to the color of' the indigo does not disappear all be analyzed as will contain about 0.1 grm. of at once; it is destroyed gradually by the local arsenious acid, and dissolve it by boiling with action of chlorine, wherever that agent happens 20 c. c. of a saturated aqueous solution of pure to be in excess in any part of' the liquor, and bicarbonate of sodiurm. Stir some starch paste is not reproduced by the action of' unoxidized into the solution, and afterwards pour in a arsenious acid in another part. Hence it is standard solution of Iodine from a burette, often necessary to add a fresh drop of indigo until the whole liquid just becomes blue. If towards the close of the titration in order to the substance to be analyzed is an acid solu- be sure of the point of' saturation. tion it must be neutralized with pure carbonate 2. By Chlorine acting in an alkaline solution. of sodium, and if alkaline with pure chlorhy- [Compare the description of this method under dric acid, before mixing it with the bicarbon- Antimony]. ate. Results accurate. As applied to the estimation of the value of To determine arsenious acid when mixed bleaching powder (after Penot, Bulletin de la with sulpihide of arsenic, boil the mixture with Socie'te Industrielle de de ulhouse, 1852, and carbonate of sodium, dilute with water and Dingler's polytech. Journ., 1853, 127. 134), the 44 ARSENIOUS ACID. process may be conducted as follows:-Heat a of the given strength, as will appear from the mixture of 4.4341 grms. of pure arsenious acid following proportion:and about 13 grms. of crystallized carbonate of Wt. of 4 Atos Wt.of Mlec. Wt.of litre sodiumi in 600 or 700 c. c. of' water, until the of chlorine' of As2(3 of Cl g-as x arsenic has all dissolved. Cool the solution 142 1983 3.1O002 and afterwards dilute it to 1 litre. Each cubic where x- 4.4341, or the quantity of arsenicentimetre of this solution contains 0.004434 ous acid that 1 litre of chlorine can convert grm. of' As2O, corresponding to 1 c. c. of into arsenic acid. - To obtain directly tile chlorine gas at 0~ and 76 in. in. pressure. chlorometrical degrees employed in England Weigh out 10 grammes of the bleaching and America, take 6.9718 grins. of' arsenious powder, rub it in a tolerably large mortar with acid for the stan(lard solution instead of' the a little water, to a smooth paste; gradually add quantity stated above, and dissolve to the volmore water, until the mass becomes fluid, and unie of 1 litre. 1 c. c. of thlls liquid will be transfer the liquid little by little to a litre equivalent to 1 c. c. - 0.005 grin. of' chlorine. flask, taking care to rub the residues in the Tlle number of c. c. used will conse(uently mortar with fresh quantities of' water as long indicate the per cent of clllorine, if' 0.5 grin. as any heavy lumps remain. Fill the flask (50 c. c.) of the bleaching powder be taken as with water to the litre mark, and mix the before. - The method of converting French milky liquor thoroughly by shaking. Each or " Gay-Lussac " degrees into per cents, will c. c. of this solution will contain 0.01 grnm. of appear from the following examples:-Bleachthe bleaching powder. - By means of a ing powder of' 900 (Gay-Lussac contains 90 X marked pipette, measure into a beaker 50 c. c. 3.18002 = 286.2018 grins. chlorine in 1000 of' the freshly shaken, milkv solution of bleach- grins., or 28.62 in 100. A sample containing ing powder, and pour into it the arsenical solu- 34.2 per cent chlorine would imark 107.5~, for tion from a 50 c. c. burette, until a drop of if 100 grins. contain 34.2 grins. C. andl 1000 liquid taken from the beaker fails to produce a grins. contain 342 grin. C1, then 342 -- 3.18002 blue spot on iodo-starch paper. The contents = 107.5, i. e., 1000 grins. of the powder conof the beaker must be stirred continually dur- tain 107.5 litres of chlorine. ing the addition of' the arsenical liquid, and For a complete table of' per cents corresthe latter must be poure(l in slowly,-at last ponding to (ay-Lussac delgrees, see L. Miiller drop by drop. It is easy to hit the point of in Din/ler's polytechlJo., rn., 1853, 129. 286. saturation exactly, since the successive blue To prepare the iodo-starcbl plpel, grind up spots produced on the paper gradually become 3 grins. of white starch in 2 50 c. c. of water, fainter and fainter, and warn the operator to boil the mixture, with constant stti rring,; add an proceed more and more slowly. — lf the op- aqueous solution of 1,rall. iodliLde of potassium erations were reversed, and the solution of and 1 grin. crystallizel carbonate of sodlium, bleaching powder were poured into the arseni- dilute with water to 500 c. c.; soak stritps of cal solution until a drop of the mlixture gave a printing paper in the litquor, dry thllel (uickly blue spot, this premonition would be lost. in pure air, and keep in tightly stoppered hotAnother objection to this inverse method of tles tbr use. working would be found in the tendency of The iprocess is accurate anti of easy applicableaching pow(ler solutions to froth, —whereby tion. The standard arsenical solution undelrit becomes difficult to read the indications of goes no change on keep)ing, providle(l thle the burette,-and to soil the burette. But, as arsenious acid and the carbonate of sodium Penot has suggested, it is sometimes well to used fobr preparing it are both absolutely fiee resort to the inverse method fbr the sake of from easily oxi(lizable lnatters, such as sulcontrolling the accuracy of an experiment phides or sulphitves. (Mohr,'itrirlel/hode, 2(1 macle in the ordinary way. Edition, 1. 290). Whllen prepared fiolI1 ortlinThe numlber of' half cubic centimetres used arv illlcterials tile alkaline solutionl oft arsenious of the standardl arsenious solution, indicates acid is liable to oxidlize slowly in the air. But directly the number of' French chloronmetrical even in tlis case, all difficulty inty ny e avoilded degrees; i. e., the number of' litres of' chlorine by keeping thle solution in a number of small gas, at 0~ anld 76 i1. in. pressure conltained in glass-stoppeled bottles, each completely tilled 1 kilog(rammle of' the bleaching powder. For with the liquitl, and using a fiesh Ibottle for example: In case 35 c. c. of' the arsenical every new series of experiments. (Fresenius). solution were consuined, then the quantity of Accordlin to Fresenius (Systemtl Quttlt Al. Alll., bleaching powder used would contain 35 c. c. Art. Chloriltintrly)),mluch more constant and of chloline gas. But the portion of' bleaching accurate results are obtained by opeIrating withl powder solution taken (50 c. c.) contained 0.5 the turbid solution, or rather ellulsion,, of grin. of the powder; hence 0.5 grm. of the bleachilng powder above described, than call bleaching powder contains 35 c. c. of chlorine. be got by filtering the liquor, or allowing it to and 1000 grlns. contain 70,000 c. c. = 70 settle, and operating upon the clear portion. litres. It is for the sake of these degrees that The emulsion should always be shakenl just the standard solution of arsenious acid is made before any portion of' it is taken for analysis. ARSENIOUS ACID. 45 Attempts of Mohr (Titrirmethode, 1855, p. In case the value of binoxide of manganese, 287) to do away with the iodo-starch paper, by chlorate of potassium, or bichromate of' potasmixingr a definite quantity of the standard siumn is to be estimated by this process, or any arsenical solution with starch paste and iodide analogous compound or peroxide is to be anof' potassium, and pouring bleaching powder alyzed, boil the substance with an excess of solution into the mixture, froml a burette, re- concentrated chlorhydric acid, absorb the chlosulted in failure. So much of' the starch was rine in arsenite or bicarbonate of sodiuml, and destroyed by the hypochlorite, wherever it estimate it as above. Compare the next Method happened to be in excess for a moment, that (by nascent chlorine). no useful results could be obtained. 3. By nascent chlorine. See Chromic Acid. Another modification of the process, how- (Reduction of by chlorhydric acid). If a dver, suggested by Mohr (Ibid., pp. 323, 290), weighed quantity of a chroinate, such as bigives accurate results. In this case a definite chromate of potassium, for example, is boiled quantity of the bleaching powder solution is with concentrated chlorhydric acid, chromic measured into a beaker, and rapidly titrated acid is reduced and chlorine set free in equivawith a standard solution of arsenious acid,- lent proportion, in accordance with the equaprepared by dissolving 4.9 grins. of pure ar- tion:senious acid in an aqueous solution of 20-25 K20, 2CrO3 + 14-IC1 CrzCrl - 2KC1 + 7H2O 6C1. grins. of pure crystallized carbonate of sodium, The precise amount of Chlorine set free may with the aid of heat, and subsequently diluting readily be determined in a variety of ways. to 1 litre, —until a drop of the mixture ceases ((Conmpare the last paragraph of the preceding to turn iodo-starch paper blue. The excess of Method). One method is to conduct the gas arsenious acid which has been used is then into a solution of iodide of potassium and to accurately determined by adding some starch estimate the iodine, which the chlorine liberpaste to the mixture in the beaker, and pour- ates, by means of a standard solution of hypoinrg in a standard solution of Iodine, until the sulphite of sodium, or by sulphurous acid. (See starch becomes blue. The amount of a rseni- Iodine). But if arsenious acid, or an arsenite ous acid which corresponds to the quantity of be addled to the mixture of bichromate of iodine solution used, is then subtracted fi'om potassium and chlorhvdric acid before this the amount of arsenious acid which was poured mixture is heated, a definite quantity of the into the beaker, in order to obtain the precise chlorine will be consumed in converting arseniamount consumed by the chlorine of the ons acid into arsenic acid, in accordance with bleaching powder. the equation:Otlher aplplications. Both processes are of As2o3 + 4Cl + 2H20 = As205 + 411C1, course applicable to the valuation of''" chloride and just so much less Cl will pass forward to of soda," and other hypochlorites, as well as to be absorbed by the solution of iodide of potasthat of bleaclling powder. They may be used sium. also for analyzing compounds of the other By operating with weighed quantities of biclhlor-oxygei acids; fior determining chlorine, ebhronate' of' potassium it is easy to determine and for analyzing many oxygen acids and per- in one sample how much chlorine is set free in oxides which evolve chlorine when heated with the absence of arsenious acid, and in a second chlorhydric acid. salmple how much less chlorine is given off An aqueous solution of chlorine may be after the addition of a weighed quantity of mixed immediately with a measured quantity arsenious acid. The quantity of arsenious of the standalrd solution of arsenious acid; acid must of' course always be less than suffiwhile gaseous chlorine may either be received cient to consumle all the chlorine which the directly in a measured quantity of thestandard quantity of bichromate taken can evolve. arsenic solution, or better, in an unmeasured Besidcs arsenious acid, the process may be apexcess of' bicarbonate of' sodium solution. In plied for determining fberrous oxide, either by the first case, some starch solution is added to itself or in presence of ferric oxi(le, and other the mixture after the chlorine has been ab- substances which are easily and completely sorbed, and the excess of' arsenious acid is oxidized by nascent chlorine, as will appear estimated by means of' a standard solution of' under the several headings. (Bunsen, Ann7al. Iodine. In the secon(l case, the standard solu- der C'heml. ulnd Phrrm., 1853, 86. 290). - It tion of' arsenious acid is poured into the alka- may here be remarked that the process, though line mixture, until a drop of the latter placed rapid and accurate, requires care and a sensiupon iodo-starch paper ceases to color it; some tive balance. If no arsenious acid were presdrops of starch solution are then added to the ent, 0.2 grin. of a chronmate containing 50 per liquor, and the slight excess of arsenious acid cent of' chromic acid would be enough for an which has been added is determined by means analysis. If more were taken, an inconveniof' the standard iodine. - In neithler case ently large quantity of' hyposulphite of sodium should any starch be added to the solution, would have to be used. A gramme of bichrountil after the chlorine has all been absorbed mate of potassium would require 500 c. c. of and combined by the action of' the arseniious hyposulphite of' the ordinary strength. (Htinacid. iman). The cost of iodide of potassium is an 46 ARSENIOUS ACID. objection, moreover, when any considerable the walls of the beaker. The beaker should number of analyses are to be made. be new and smooth, for it is difficult to wash AMethod C. Oxidation by Bichromnate of out the precipitated gold from a beaker which Potassium. has become roughened by use. The solution 1. Volumetric. Method and precautions de- must be free from nitric acid and other oxidizscribed under Antimonious Acid. See also ing agents, and must be protected from dust biChromate of Potassium (Kessler, loc. cit.). also. A considerable excess of chlorhydric See also the preceding paragraph,-oxidation acid, however, appears to do no -harm. In of As2O3 by nascent chlorine. case the substance to be analyzed is solid, it 2. Gravimetric. Mix the substance to be should be dissolved in chlorhydric acid. examined with a weighed quantity of pure, Though inferior to Method A, the gold prodry bichromate of potassium, place it in a cess is reputed to yield accurate results, and to suitable vessel and add strong sulphuric acid. be free from the sources of error which have A quantity of chromic acid will be reduced by led to the abandonment of the process as apthe arsenious acid, in accordance with the plied to the determination of Antimonious equation:- Acid. The inventor of the process, H. Rose, 3As203 + 4CrO3 = 3As205 + 2Cr203. remarks that its results would probably be less Determine how much chromic acid is left, by accurate in case too large a proportion of means of oxalic acid (see Chromic Acid, re- chloride of sodium, or of chloride of ammoduction of by oxalic acid), and calculate how nium, were mixed with the chloride of gold in much arsenious acid must have been present to preparing the chloraurate. reduce the remainder of the chromic acid taken. (Vohl, Andalen Chem. und Pharm., In order to be fit for use as a reagent, arseni94. 219). ous acid should volatilize without residue, and Method D. Oxidation by Permanganate of should yield no brownish coloration when 10 Potassium. The process is attended with diffi- or 12 grms. of it are dissolved in a solution of culties which have not yet been fully overcome. pure carbonate of sodium, and tested with a (Kessler, Poggendorff's Annalen, 118. 17; drop or two of a solution of acetate of lead. Lenssen, Journ. prakt. Chemie, 78. 197). The brown color thus produced is due to the Method E. Oxidation by Nitrate of Potas- presence of sulphide of arsenic; and in case a sium. Same Method as that described under residue is left on heating, which turns black Arsenic, with the exception that a smaller pro- when ignited in a current of hydrogen, the portion of nitrate of potassium is needed. A presence of antimony is indicated. mixture of 3 parts carbonate of sodium and 1 The solid cakes of arsenious acid to be obpart nitrate of potassium, is sufficient for the tained of importers of pure chemicals, are genfusion of an arsenite. The fusion may be erally quite pure. effected, in a platinum crucible. Arseniomolybdate of AmmoMethod F. Oxidation by A qua regia, or by nium. Chlorate of Potassium. Method described un- Principle. Insolubility in water, and in acid der Antimony and Arsenic. and saline solutions. According to Stein, this principle may be Applications. Separation of arsenic acid used for estimating nitric acid. To this end, from Na, K, NH,, Li; Ba, Sr, Ca, Mg; Al, mix the nitrate to be analyzed with 3 parts of Cr, Fe, Mn, Co, Ni, Zn, Cd, Pb, Bi, Ag, Hg arsenious acid, dissolve the mixture in concen- and Cu. Estimation of arsenic acid in solutrated chlorhydric acid, and evaporate to dry- tions free friom phosphoric and silicic acids, ness. Take up the residue with water, and and from substances capable of decomposing determine the arsenic acid by precipitating it molybdic acid. as Arseniate of Magnesium and AInmoniumn. Method. Prepare a solution of molybdate MIethod G. Oxidation by Salts of Gold. of ammonium by heating 10 grms. of that salt Mix the solution which contains arsenious acid with 40 c. c. of' ammonia water of' 0.96 specific with an excess of a solution of chloraurate of gravity, pour the solution into a mixture of sodium, or chloraurate of ammonium, and 120 c. c. strong nitric acid, and 40 c. c. of allow the mixture to stand in a covered beaker water, and let the whole digest for 8 or 10 for several days at the ordinary temperature, hours, at 40~. Allow the mixture to settle, Collect and weigh the precipitated Gold, and and decant the clear liquid. from its weight calculate that of the arsenic in Mix the solution which contains the arsenic the solution, in accordance with the reaction:- acid with a large proportion of' the aforesaid 3As2oa+ 2Au2 = 3AS205 + 4Au. solution of nlolybdate of ammonium, add In case the original solution is very dilute, it enough nitric or chlorhydric acid to redissolve had better be left to stand in a place slightly the precipitate of molybdic acid which forms warmer than the ordinary air. It is well to at first, and boil the solution for a long time. keep the filtrate from the metallic gold, and to If molybdic acid has been added in excess, collect any further portion of gold which may arseniomolybdate of ammonium will be thrown be deposited from it. Even from the original down in the form of a yellow precipitate. The solution the gold is deposited very slowly upon subsequent operations are similar to those de BISMUTH. 47 scribed under Phosphomolybdate of Ammo- Method B. Dissolve the alloy in nitric nium. Since it is not easy to separate molyb- acid, dilute the solution with a large quantity dic acid from the filtrate, a new portion of the of water, and place in it a strip of pure meoriginal substance had better be taken for the tallic lead. The bismuth will be precipitated determination of the metals with which the rapidly and completely, in the form of a black arsenic acid was originally combined. powder. As soon as the precipitation is finProperties. Arseniomnolybdate of ammo- ished, decant the clear acidulated liquor, wash nium is well nigh insoluble in water, saline off adhering particles of bismuth from the solutions and acids, especially nitric acid, pro- strip of lead, and wash the precipitate rapidly vided an excess of molybdate of ammonium by decantation, first with water, and then with be present, together with a moderate excess of alcohol. Collect the precipitate upon a small nitric or chlorhydric acid. The composition weighed filter, dry and weigh. (Patera, of a sample of the precipitate analyzed by Zeitsch. analyt. Chems., 1866, 5. 226). Seligsohn (.fourn. prakt. Chem., 67. 481), was Miethod C. After having brought the mixmolybdic acid 87.67 per cent; arsenic acid ture of bismuth and lead into solution, throw 6.31 per cent; ammonia 4.26 per cent, and down both the metals as carbonates, by means water 1.77 per cent. Since its composition is of carbonate of ammoniumn, dissolve the prevariable, the precipitate is never weighed di- cipitate in acetic acid, and place in the solurectly. It is dissolved in ammonia-water, and tion a weighed piece of pure sheet lead. Arseniate of Magnesium and Aminmonium is Cover the beaker, and leave it at rest for sevprecipitated from the ammoniacal solution. eral hours, taking care that no part of the Atropi n See Iodo Mercurate of Atropin. lead projects above the surface of the liquid. When all the bismuth has been precipitated, Barium is usually determined as Sulphate wash the strip of lead, and dry and weigh it. or Carbonate, but sometimes as Fluosilicate The difference between the first and last of Barium. For its alkalimetrical estimation, weight of the lead indicates how much of this see Oxide and Carbonate of Barium. See metal has been added to the solution. Collect also the finding list for Barium, in -the Ap- the precipitated bismuth upon a filter, and wash pendix. it with water which has been boiled to expel Baryta. See Hydrate of Barium. air, and afterwards cooled. Dissolve in nitric Basic Benzoate of Iron (Ferric ben- acid, and precipitate Carbonate of Bismuth; zoalte). or evaporate the nitric acid solution to dryness, Principle. Insolubility in water. and ignite the dry residue to obtain Oxide of Applications. Separation of Fe from Mn, Bismuth. Lead may be determined in the Ni and Zn. filtrate by precipitating it as Carbonate of Miethod. Same as that described under Suc- Lead. (Ullgren, Berzelius's Jahresbericht, 2L cinate of Iron. 148). When benzoic acid, or rather, when the Principle II. Fixity, when heated. alkaline benzoates can be obtained at less cost Applicatio ns. Estimation of bismuth in the than succinic acid and the succinates, it is oxide, sulphide, oxychloride and salts of this better to precipitate iron as a benzoate (Hisin- metal. ger & Berzelius). Basic benzoate of iron is MIethod. Fuse the compound to be analyzed indeed slightly less soluble than the corres- in a capacious porcelain crucible, with 5 times ponding succinate, but this advantage is bal- its weight of' ordinary cyanide of potassium. anced by the fict that the precipitated ben- Soak the fused mass in water; wash the kerzoate is more voluminous than the succinate. nels of metallic bismuth rapidly, first with Moreover, it contains much more carbon than water, then with weak alcohol and finally the latter; but this diffculty can be overcorne, with strong alcohol; collect upon a small, as with the succinate, by leaching the precipi- tared filter, dry and weigh. in case oxide tate with dilute amnmonia-water, until most of or oxychloride of bismuth be operated upon, the benzoic acid is removed. the reluction is soon completed, at a low Bismuth may be determined as metallic heat, but the sulphide requires more time Bismuth, Carbonate, Chromate, Oxide or and a higlher temperature. When, on treatSulphide. For a list of methods for sep- ing the fused mass with water, only mearatingf it from the other metals, see Ap- tallic grains remain undissolved, the reduction pendix. may be deemed complete; but if in reducing Principle I. Insolubility of the metal in the sulphide, there is left a quantity of the dilute nitric or acetic acids in presence of latter, in the fbrm of black powder, mixed metallic lead or zinc. with the metal, this powder should be collected Applicatiors. Separation of bismuth from and again fused with a fresh quantity of cyancertain other metals,-notably from lead. idle of potassium. The crucible should be Miethod A. Precipitate the bismuth by me- weihed before the experiment and after it; tallic zinc, from a dilute nitric acid solution. also in connection with the tared filter; for it (PJaff, Handbach analyt. C/lhen., 1825, 2. sometinmes happens that particles of porcelain 401). torn off' finom the crucible during the process 48 BOILING POINT. of reduction, remain mixed with the metallic of the retort downward, and connect it with a bismuth. The metho(l yields good results. Liebig's condenser. Again place the lamp (H11. Rose, Po(jqenudoift's Alnnalen, 91. 104, and beneath the retort, and continue to boil the 110. pp. 136. 425). liquid until most of' it has been distilled over Boiling Point. out of the retort. In the course of a few secTo (letermine the boiling point of any olnds after the lamp has been replaced, the substance, place a quantity of the liquid in mercury in the thermlnometer will again become a small, tubulated, long-necked glass retort; stationary. At that momlent note the time throw into the liquid two or three fragments and the height of the mercury in the thermnomlof coke, each as large as a small pea, a eters, and repeat these observations at freglobule of' mercury, a few small scraps of quent intervals, untilthe distillation is finished. platinum foil, or better, a piece of metallic If the liquid under examination be pure, the sodium, in case the liquid under examination height of' the thermometer will scarcely vary is a hyldrocarbon. As much as 100 or 200 c. c. fromn first to last. In case there are slioht dif' of the liquid should be taken, if it can be had. ferences between the earlier and later observaThe presence of the coke or metal, to facilitate tions, either the average of the several obserebullition, is essential. In case no fragments vations, or better, of' those corresponding to of solid matter are placed in the retort, the the longest intervals of' tilne, may be chosen. liquid is not only liable to "bump " when Any material differences between the several heated, but even to boil at a higher tempera- observations would of course indicate that the ture,-in the case of' some liquids, 50 or 60 liquid under examination was a mixture of two hilgher,-than its real boiling point. or more substances of' unlike boiling points. Close the tubulure of the retort with a cork, In case the boiling point of' a mixture, such to a perforation in which a thermometer has as ordinary spirit, is to be determined, only the been fitted, in such manner that when the first observation, made when the neck of' the cork is pushed tio-htly into the tubulure the retort is inclined upwards, is of value; for the bulb of the thermometer shall extend into tile strength, and consequently the boiling point of liquid, and reach almost, but not quite, to the the spirit, would change if the liquid were bottom of' the retort. (Warren, Amer. Joli'n. subjected to distillation. The process of' disSci.,'1865, 40. 222). To that part of the tillation above described, is to be omitted, stem of' the thermometer which projects above therefore, when a mixture is tested. the cork, tie a second thermohmeter, in such The purpose of the upper or side thermomemanner that it can be slipped up or down ter is merely to determine approximately the without (lifficulty, and place a broad sheet of mean temperature of' that portion of' the lnerpaper or pasteboard across the top of the cork cury colulln in the fixed thermometer, which to screen the upper therlometer from any is above the cork, in order to ascertain what heat which miight radiate from the retort. Set amount of' correction should be made to cormthe retort uplon a wire gauze support. above a pensate for the cooling action of the air. The lamnp, in such position tliht its neck shall in- upper thermometer would be useless in case no dcine slightly upwlards place a screen below portion of' the mercury columln were to prothe retort to protect its sidles from being over- ject above the cork, for in that event the whole heated, twist mloistened cloths around the neck of the metal, being surrounded with the vapor of the iretort to keeL) it cool, aml in case the of' the boiling liquid, would hlave one and the li(luidl is easily volaitile, place bits of' ice upon same temperatur'e. But when, as is usually the cloth. Finally heait the liquid until it boils the case, a part of' the mercury rises above the steadily, an(l the ilelcury in the therlolnmeter cork, and is thus expose(l to a lower temperace'ases to rise. Somle little time will often be ture than that of' the boiling liquid, the upper relquire(t in r(lcer thlat tllat porltion of the thler- extrellity of' the column will stand at a slightly molneter which projects above the cork may lower point than it would if' no portion of the acquire the highest temperatiure which the mercury had been cooled. The correction to boiling liquid can communicate to it. - In be applied( to the observed temperature T~, is case the liquid boils at a lower temperature found by means of the ftllowing formula: — than that of' the air, place the retort in a bath N (T-t) -, of ice-water, andl gradually raise the temperature of the bath bv means of a small lamp- in which t is the observed height of the upper, flame. - Arrangre the upper, moveable moveable therllometer, N the difference bethermometer so that its bulb shall be in con- tween T'1' and that degree of' the thermometer tact with the stern of' the fixed tlhermlloleter, scale which is situate(l at the mniddle of' the at a point midway between the Ilupper end of cork; or, in other words, the length of' the the mercury column in that thermomlneter and colulmn of' mercury which hits been cooled to the centre of the cork. Then note the height t~ by contact with the air, and $ the coefficient of the barometer and of both thermometers. of apparent expansion of' mercury in the glass As soon as the mercury has become stationary of which the thermlonieter is constructed. The in the thermometer, remove the lanp fbr a value of' 6 may be taken as equal to 0.0001545. moment fioom beneath the retort, turn the neck (ItI. Kopp, I'oggeelloif'"s Alnitl., 1847, 72. BORACIC ACID. 49 38). For example, —if a liquid is observed to weighed solution, evaporate the mixture to boil at 171.30 ( T) and the 25th degree of dryness at a gentle heat, and carefully heat the thermometer be at the middle of the cork, the residue until it fuses to a thin liquid. A thenNwill equal 171.30 —25 = 146.30. And quantity of carbonic acid, equivalent to the if' thie mean temperature of' the external col- quantityv of boracic acid present, will be exumn of mercury wvere 430 (=- t), as observed pelled, and there will be left a mixture con — by the upper therimometer, then T-t would taining a known quantity of sodium, and. unequal known quantities of carbonic and boracic acids. 171.3 -43 — 125.3. 7;'Weigh the residue, and determine the amlount The correction to be applied will consequently of Carbonic Acid contained in it. Froml the be diffibrence between the quantity of carbonic 1.3 x 12.3 x acid in the carbonate of sodium taken, and and the boiling point of the liquid " corrected that found in the residue, calculate the amount for external column of' mercury," will be of boracic acid (H. Rose). 171.3 + 2.9 = 174~.2. In case the proportion of boracic acid in the solution to be analyzed is known approxiSince the boiling point of a liquid depends mately, between 1 and 2 equivs. of carbonate of on the pressure to which the liquid is subjected, sodium should be taken fior two equivalents of another correction must be applied in order to boracic acid. If this be dcone, all the carbonic reduce observations made under the varying acid will be expelled on heating, and we have pressure of the atmlosphere, to the values only to deduct froln the weight of the residue which would obtain if the atmospheric pres- the -weight of oxide of sodium taken, in order sure were normal, —tlat is to say, equal to to find the weight of the boracic acid. Since 760 millim. of mercury at 00. It is customary, the tumultuous escape of carbonic aci(l might on this account, to apply a correction of' +' 0. 1~ occasion' loss, it is best not to ignite the residue C., for every 2.7 millimn. that the mercury in left by evaporation all at once, but after thorthe barometer stan(ls above or below 760. ougrh drying, to project it by small portions Strictly speaking, the correction to be applied into a red hot crucible. (Schaffgotsch, Pogy. to the boiling point of a liquid observed under Aim., 107. 427). an atmospheric pressure other than the normal Propertfies. It may be remarked, in this conpressure, varies with the nature of' the liquid; nection,that boracic acid cannot be dletermined for equal alterations of' pressure do not cause by'evaporating its aqueous or alcoholic soluprecisely equal changes in the boiling points of tion to dryness, and weighing the residue; for different liquids. The value above given, of though little volatile of' itself, considerable 0.10 for a variation of pressure of 2.7 millim., portions of the acid are carried away by the has beent deduced fronm direct determinations aqueous or alcoholic valpor. The samelt reinark of the boiling point of water under different appilies to solutions to which an excess of oxide pressures, and is absolutely accurate for that of lead, of ammlnonia-water, or of' triphosphate liquid alone. But since the greatest variations of sodium, has been added. which ever occur in the pressure of the atlnos- In the cold, no carbonic acid is expelled by phere are relatively very small, they may, boracic from carbonate of' sodiumr, and( only a without any appreciable error, be regarded as small quantity escapes during thle evap)oration affecting the boiling points of all liquids of the aqueous solution. It' is only when the equally. dry mass is ignited, that the evolution of carBoracic Acid is determined either in- bonic acid really begins. directly; as Fluoborate of Potassium; or as Principle II. Power of expelling water from Borate of Magnesiumn. [See finding list for certain refractory hydrates; i. e., fixity and Boron, in the Appendix]. power of combining with bases to forin fixed'PrinciVle I. Power of expelling carbonic products. aci(l from Carbonate of Sodium. Applications. Estimation of water in the Applications. Estimation of boracic acid in hydrates of Na, K, Ba and Sr. aqueous solutions free firoomn all other sub- Method. -Mix a weigllhed quantity of the stances, except amuniolnum. In case a heavy substance to be examined, with a weighed metal has been separated from boracic acid by quantity of powdered anhydrous boracic acid3, precipitating Wvith sulphuretted hydrogen, the more than sufficient to saturate the whole of' mnethod now in question may be employed for the alkali. Fuse the mlixture in a platinum deterlininig boracic acid in the filtrate, after crucible, until all the water has been expelled, the excess of suilphuretted hydrogen has been and wveigh the col(l product. The (liffere-ncle expelled, by 1)assillu, a cllrent of' carboZnic acid between the final weight and the sum of the through the liquom. The filtrate ilust, how- weights of' boracic aci(l aild substance talceln. ever, contain no acid besides boracic acid. will represent the weight of' the water. (Pfhfi.; Mlethoel. Wteigh oult or 2 times aIs nilch ll ftnd(1ch (clt/t. ClhemT., 1824, 1. 117). The pure, fusedl carbonate of so(liuni, as there is substance analyzed must eithlelr he fiee fronl supposed to ~be boracic acid in the solution to carbonic and otller volatile acidIs, or the probe analyzed. Dissolve the carbonate in the portion of these substances must be determilned 4 t50 BORATES. in separate portions of the material. The found from the weight of the borate of magprocess can hardly be capable of yielding abso- nesium, in or'der to obtain the weight of th lutely accurate results, since, as is well known, boracic acid. The process yields satisfactory boracic acid is somewhat volatile in an atmos- results. (Marignac, Zeitsch. anallt. Cheem., 1. phere of aqueous vapor. Compare biBorate 406). of Sodium. Precautions. The platinum dish must be P.rinciple III. Power of decomposing sili- weighed in the first place, since small portions cious minerals. of platinum are apt to appear on dissolving An old method employed by Davy, Gehlen the residual borate in chlorhydric acid. If and others, for the decomposition of refractory the weight of the dish were unknown, it would minerals in which alkalies were to be determ- be necessary to weigh this abraded platinum, ined, deserves mention, though it has long and subtract its weight from that of the borate since been superseded by the methods of fusing of magnesium. When the volume of liquid to with alkaline earths, or treating with fluorhy- be operated upon is considerable, it had better dric acid. be concentrated to a small bulk in a porcelain Davy fused the powdered mineral with twice dish, and afterwards evaporated to dryness in its weight of boracic acid glass, for half an the platinum vessel. - In case boracic acid hour, in an intense fire; decomposed the fused is to be separated from a heavy metal precipmass with dilute nitric acid; evaporated to itable by sulphuretted hydrogen, the filtrate separate silica; precipitated with carbonate from the metallic sulphide should be mixed of ammonium; supersaturated with nitric acid with hydrate and nitrate of potassium, evapand separated the boracic acid by crystalliza- orated to dryness and ignited, before adding tion from the nitrates of the alkalies. (Pfaff, the chloride of magnesium, as above described. Handbuch analyt. Chem., 1824, 1. 467). Pfatf Borate of Potassium. See Borate proposed to separate the alkalies from the of Sodium. boracic acid by converting them into sulphates, Borate of Sodium. and then washing out the last portions of bo- Principle. Solubility in water. racic acid with alcohol. Applicaticns. Separation of boracic acid Basic Borate of Magnesium. from most of the metals, other than alkali Principle. Insolubility in water, and fixity metals. when ignited. Method. Boil or fuse the borate to be anApplications. Estimation of boracic acid in alyzed with carbonate or hydrate of potassium, presence of alkalies. or of sodiumn, filter off the precipitated carbonMethod. Neutralize the solution with chlor- ate or hydrate of the metal, and determine hydric acid, add enough double chloride of boracic acid in the filtrate as Borate of Magmagnesium and ammonium, that at least.2 nesiumn, or as Fluoborate of Potassium. parts of magnesia may be present in the solu- BiBOrate of Sodium. (Borax). tion for 1 part of boracic acid, pour in some Principle. Power of expelling Carbonic, ammonia-water, and evaporate the mixture to Nitric and Silicic acids, when fused with salts dryness in a weighed platinum dish. If, on of these acids. See the respective acids and the addition of the ammonia-water, a precip- Boracic Acid. itate falls which does not dissolve readily on It is to be observed, that though "boraxwarming, a new, quantity of chloride of am- glass " may be kept fused at a red heat for monium must be added to the mixture. From quarter or half an hour without loss, through time to time during the evaporation, add a few volatilization, an appreciable quantity of the drops of ammonia-water. Ignite the dry resi- compound exhales at a white heat. A decided due,' and afterwards treat it with boiling water. loss of weight occurs, for example, when a Collect the insoluble mixture of borate and platinum crucible containing dry borax-glass oxide of magnesium upon a filter, and wash it is ignited even for a few minutes at the blast with boiling water, until the wash water ceases lamp. (Fresenius, Zeitsch. analyt. Chem., 1. to give any precipitate when mixed with ni- 65). trate of silver. Mix the filtrate and washings Borax was formerly somewhat used for dewith ammonia-water, again evaporate to dry- composing refractory minerals. Thus Berzelness, ignite and wash witlh boiling water, as ius & HIisinger (Gehlen's neues Journ. der before. Place both the insoluble residues in Chemie, 6. 304) fused finely pulverized spinel the platinum dish, and ignite them for a long with twice its weight of' borate of potassium, time as strongly as possible, in order to decom- in a platinum crucible, and dissolved the fused pose the small quantity of chloride of magne- mass in chlorhydric acid. (Compare Aluminate slum which may still be mixed with the borate. of Sodium). - Borax-glass is still used, in Weigh the cold product, dissolve it in chlorhy- conjunction with carbonate of sodium, ill the dric acid, and determine howv much magnesia excellent method of Plattner (Probirkuast mit is contained in it by precipitating as Phosphate demns Lthrolhe, 1853, p. 689), for analyzing, of Magnesium and Ammonium, or estimnate with the aid of the mouth blowpipe, those iron the magnesia at once by the process of Alkal- ores whichl cannot be decolmposed by acids. imetry. Subtract the wreight of the magnesia It is to be observed, however, that the process BROMIDES. 51 depends upon the fusibility of borate of iron, residue to powder, and again heat it in a plaand the solubility of this substance in acids tinunr crucible, until it fuses to a transparent rather than upon any superior affinity of bo- mass. Pour the semi-fluid, viscid substance racic acid for iron. The details of the method upon a piece of porcelain, and keep the cold are as follows: —Grind a considerable q(uantity solid in a well-stoppered bottle. The boraxof the ore to fine powder, best in an agate glass mlust, in most cases, be reheated just bemortar, mix the powder thoroughly, spread it fore use to ensure its absolute fieedom fiom to a thin layer, and draw a fair sarrymple of' it moisture. by taking a number of' small quantities from. The purity of commercial borax may be different parts of the latyer. Dry the sample tested by tladding carbonate of sodium to the at 100~, weigh out 0.1 grin. of the powder on aqueous solution, and by adding solutions of a delicate assay balance, transfer it to a large nitrate of barium and nitrate of silver to other test tube, and pour upon it, little by little, a portions of the solution after acidulating it quantity of strong chlorhydric acid. As soon -with nitric acid. Neither of these reagents as the acid has ceased to act in the cold, heat should occasion an)y alteration in the appearit over a spirit lamp as long as anything dis- ance of the solution. In case the borax is solves; throw the mixture upon a small filter, impure, it may be purified by recrystallizatiolln. and wash the residue with boiling water. Dry Bromates llay be converted to Bromides the residue, which will exhibit a yellowish, red, by ignition, and weighed as such; or they or gray color, over a spirit lamp. If the ore may be mixed with an excess of clllorhydric were of' such character as to be decomposed acid, the mixture evaporated to dryness, and completely by chlorhydric acid, thle residue upon the chlorine estimrated as Chloride of Silver, the filter Iwould be colorless, and free from by titration. From the weight of chlorine iron; so that the process now in question, i. e., found, the equivalent weight of bromic acid the fusion with borax, would not be called fbr. may then be calculated. (Mohr). But the residue does, in fact, contain silicates Bromides of volatile elements, such as of iron and the earths, as well as quartz, and the bromides of arsenic, antimony, phosrarely some sulphate of'barium, also. As soon phorus and sulphur, are completely decomas it is thoroughly dry, mix it in the filter with posed by water, with formation of' bromhyas nluch powdered borax-glass, and 3 times its dric acid, which may be deteriined by bulk of dry carbonate of sodlium. Roil the precipitation, as Bromide of Silver. paper into the form of' a small ball or cylinder, Bromide of Mercury. place the ball in a hole bored across the grain 1]rociple. IPower of' Oxide of Mercury to of a good piece of charcoal, and melt the mlix- absorb bromine at the ordlinary temperature, ture, with the oxid(izing blowpipe flamle, to a and fixity of the compound formed.. clear, transparent bead. After the bead has Apllication. Estimation of bromine in orbecome cold crush it in a steel mortar, place ganic substances. the powder in a light porcelain cup covered 1lethod. Heattthe substance to be analyzed with a watch glass, and treat with dilute clllor- in a stream of' hydrotgen, aid burn the h:ldrobydric acid; then evaporate the solution to gen thus charged -with the vapor or pro:lucts dryness, together with the previois solution of' distillation of' the substance, in a stream1 of obtained by acting upon the ore witlh acid, to oxygen. Plass the prodllucts of the comlbustioll separate Silicic Acid. The filtrate friom silicic over a la'yer of strong sulphuric acid, to filce acid is boiled with nitric acid to oxidize the them froml water, absorb the bromine in a tube iron; the latter is precipitated, together with filled with fragments of precipitated oxide of' alumina, as Hydrate of Iron, and the alumlina mercury, and the carbonic acid in potash lye. dissolved gut as Aluminate of Sodium, in the The oxide of mercury should be in the form of' usual way. - The process has great merit pellets, or coarse nimasses, and should be folfrom its simplicity. It may be put in practice lowed by a short column of chloride of calalmost anywhere, since it neither requires a cium, placed at the end of the tube farthest well appointed laboratory nor expensive appar- from the burning hydrogen. For the details of atus. It is evident that besides iron, silicic the process see A. Mlitscherlich's paper in acid, and many other constituents of refiactory Zeitsch. analyt. C/hem., 1867, 6. pp. 151, 153, silicates, may readily be determined in this 156, 141. Conlpare Carbon, oxidation of with way. Analyses of red ochlre, made under my oxyg en QIgs. (irection by this nmethod, anid by a nmodifica- Bromide of Silver tion of it, in which either itpure silicie acid or i'l.ci5 le I. lnsolubilitv in water and ni — silicate of sodium (water glass) was sulbstituted tric acid. for the borax, showed clearly the imlporltance A1)p'ic(ttioots. Seplaration of' bromine fronM of the borax, and the improprie ty of' tiying to nliost of, the llmtals, and tim organlic su)bdo without it. stances. Estimllati of'l briomllvdric acid andt of ti'ee )bro)ine11i. Set ratiOn of bromnIlydric To prepare borax-glais, bh.eat ordlinary crys- aci fi'molm As,()::, As1();, 0,0 Cr0n, S0.,. tahllized borax in a platinulmi ofr porcelaill dish 2,0 i 01()4, 11'l, Si(s al d C()O until it ceases to swell up. sGrind the polrous Sinlce b)rollide oft silver is precipitated before 52 BROMIDE OF SILVER. chloride of silver when nitrate of silver is in a bromide) which is precipitable by nitrate ci' added to a cold solution contcaininfg both chlo- silver can be thus determined, but on this verl rides and bromiides, the insolubility of the account the process is valuable for determining bromide may even be used for separating bro- the rational constitution of certain broioine mine from chlorine as will be described below. compounds. (Maly, Zeitsch. analyt. Chem.., The ilethods and Precautions are similar to 1866, 5. 68; Kraut, Ibid., 1865, 4. 167). those described under Chloride of Silver. The Separation oq ]rominefrom Chlorine. [Comprocess yields excellent results. pare Chloride of Silver and Iodide of Silver]. Properties. As prepared in the wet way, Several methods of separating brouinne fi'on bromide of silver is a yello.wish-white precip- chlorine depend upoi the principle now in itate, insoluble in water and nitric acid, tolera- question. bly soluble in aimmonia-water and readily sol- A. Iehlsin's method. AIix the cold solution uble in solutions of the hyposulphites and to be analyzed with a quantity of nitrate of cyani(les of alkali-metals; Though insoluble silver solution somewhat more than suflicient in very dilute solutions of alkaline chloridcles to precipitate all the bromine, but not nearly and bromides, some of' it dissolves in concen- sufficient to throw down all the chlorine. Shake trated solutions of these salts. Traces of it the mixture strongly and leave it standing for dissolve also in solutions of the alkaline ni- some time, with occasional agitation. AW\ash trates. A solution of iodide of potassium the Ilixed precipitate of bromide and chloride converts it into iodide of silver. - lVhien of silver with especial care and thorouglness, heated, it melts to a reddish liqcuid which dry, ignite, weigh, and treat a weighed porsolidifies to a yellow, horn-like mass on cooling. ti(.n of the residue with chlorine, as directed It may be weighed, however, as well after below, under Principle III, or with zinc (see havin( been dried at 100~ as -after melting. Silver). To find the quantity of chlorine, preWhen heated in chlorine gas it is converted cipitate another weighed portion of the original into cllloride of silver and when heated in solution completely with nitrate of silver and hydrogen to metallic silver. The precipitated firom the weigfht of this precipitate deduct that bromide gradually becomes gray and finally of the bromide of silver found. - The folblack when exposed to light. Both the pre- lowing rule indicates in a, general way how cipitated and the fused bromide are decom- mtch nitrate of silver should be used. If the posed by metallic zinc with formation of solution to be analyzed contains 0.1 per cent metallic silver. The composition of the bro- of bromine, add - or 1 as much of the solution mide is as follows: - of nitrate of silver as would be required to Ag = 108 - 57.44 effect complete precipitation; - if 0.01 per Ur =S0) - 4~2.; cent, L — if 0.002, r; — if 0.001, 6-. 188 100.00 (Fehling, bJourn. pralct. Chen., 45. 269). D'etermination of Bromine in bromides of B. Jlohr's rzethod. Precipitate all the broOrganic Substances soluble in water. [Conmpare mine and part of the chlorine by means of a Chloride of Silver and Iodide of' Silver]. known wei(ght of silver, added in the form of Weigh out about 1 grm. of nitrate of silver, nitrate of silver. Wash and weigh the mixed dissolve it in water and add chlorhydric acid precipitate. Calculate the amount of chloride until all the silver is precipitated as chloride. of silver equivalent to the metallic silver taken, Wash the chloride of silver with hot water, by subtract this weight from that of the mixed decantation, and pass the washings through a precipitate and finally calculate how m1uch small weighed filter to retain any suspended bromide of silver was present, by the method particles of' the chloride. Pour upon the given below, under Principle Ill. - This washed mass of chloride of silver an aqueous method has the merit of being more convenient solution of about 0.5 grin. of the substance to and expeditious than the old method with be analyzed. Warm the mixture and let it chlorine described below (Principle III), but stand for a couple of hours, then collect the is probably somewhat less accurate than the mixed bromide and chloride of silver upon latter, especially when the proportion of brothe weiglied filter, above mentioned, wash it mine in the mixture is small. In criticising the thoroughly, dry, and weigh. From the weight process, Fresenius urges that the supposition of the mixed precipitate and the known weight that a weighed quantity of silver will yield a of silver taken, calculate the rweight of thle precisely equivalent quantity of chloride of bromine in the precipitate as explained below, silver is practically incorrect, errors to the under Principle III. extent of some mnilligrammres being sc.rcely One merit ot the process, at least as applield avoid(bhle: it Inight thus happen that bromine to rare and costly substances, consists in the could be calculated firom a supposed difference fact that the substance is not destroyed. It is even in cases where no trace of this element fbund again in the filtrate from the bromlide of was present. (Compare Principle III). silver in the forim of a chloride. The process is The silver used as the precipitant may either not applicable to all organic substances contain- be weighed in the metallic state and then be ing bromine. Only that portion of'bromine (as dissolved in nitric acid, or it may.be added in BROMIDE OF SILVER. 53 the form of a standard solution of nitrate of chlorine has been replaced by air, and weigh. silver. (F. Mohr, Antn. Chein. und Phtarm., Again heat the contents of the tube in a 93. 76). current of chlorine durinn- 10 or 12 minutes C. WVittstein's method. See under Chloride and weigh as before. Rlepeat the operations of Silver. of l heatingr and weir-hincg until two consecutive D. Pisani's method. Add to the mixed solu- weighings give the samne result. The (lecrease tion of bromides and chlorides a known quan- of weight is simply the dift'lrence between the tity of a standard solution of nitrate of silver weight of the bromine originally present in the in slight excess, filter a(nd determine the silver mixed salts and that of the chlorine which has in the filtrate by titration with iodine. (See replaced it. The weight of bromine ori(rinally Iodide of Silver). The precipitate is weighed prosetnt is therefore deduced from the proand the proportion of bromine calculated as in portion. B. The principle of the method is slightly Difference between At, p t. different from that of the preceding methods, At.,ts. of aDecreaseof. Br nt. of 4. s:to o -8U Weight 13r pr-esent. inasmuch as it precludes the partial precipitation. (Pisani, Comptes Rendus,.44. 352). It results from this proportion that the Principle II. Reduction of to.metallic wei(ht of bromine may be obtained by multisilver by hot hlydrogen. plying the observed decrease by 1.797. If the Applications. Estimation of bromine in anolunt of chlorine originally present is also presence of chlorine. desired, calculate the quantity of silv-er in the Mlethod. Weigh out a portion of the mixed pure chloride of silver last weilhed, and precipitate of bromide and chloride of silver subtract this weight of silver and the veight of in a light bulb-tube: pass a slow current of bromine deduced as above described, fiolll the hydrogen through the tube, heat the substance original weight of the mixed chloride and in the bulb until it fuses, and occasionally bromide. Tlhe remainder is the required shake the fused niass so that new surfaces muay amount of chlorine. - To determine the be exposed to the action of the hydrogen. quantity of chlorine, precipitate completely When the reduction seems to be complete, with nitrate of silver a new portion of' the allow the tube to cool, hold it in an inclined substance to be analyzed and detuct from the position for a moment so that the hydrogen weight of this precipitate that of' the bromide within it inay be replaced by air, wei(h it, of' silver rtundl as above. again heat its contents in a current of hydrogen ilrecaulioos. Though the method is tedious and continue these operations until the two andt inconvenient, very accurate results can be last weighings agree. Calculate how mnuch obtained by it if the proportion of bromine in chloride of silver-is equivalent to the metallic the mixture is not too small. Care must be silver found, subtract this chloride of silver taken to expiel the last traces of bromline and from the weight of' the mixed chloride and to weigh with scrupulous accuracy in eahle bromide of silver taken, and calculate how instance. The method is less liable to error much bromine was present, by the method than Mohr's process of' precipitating with a given below, under PrinciplelII. This method known weight of silver, above describedl of reducing by hydrogen offers an excellent (under Principle I). According to Fresenius control to the method by chlorine described a silple experiment will show that pure below, under Principle III. - Compare also chloride of silver heated cautiously in a curthe details of' manipulation there described. rent of chlorine in a light bulb tube suffers'Principle II1. Conversion into chloride of no alteration of' weight. An error of 0.5 mnilsilver by hot chlorine. [Compare Chiloride of lieramline in this operation would be niolre surSilver, decomposition of by bromide of potas- prising than an error of 2 mgrs. in the consium]. version of 2 or 3 grms. of silver into chloritle Applications. Estimation of bromine in of silver, more especially if a filter &fere used presence of chlorine. in the process; and the filter can hardly be Mlethod. After the mixed precipitate of dispensed with, since a precipitate almlost bromide and Chloride of Silver has been col- always subsides less readily and comlpletely in lected andl weighed in the usual way, fuse it case of partial precipitation than when the in the crucible and pour out upon a piece of precipitation is complete. porcelain as much of the fused mass as will be The process is not directly applicable for sufficient for an analysis. Place the fragments determining small traces of bromine in 1resence in a weighed bulb tube, and again weigh the of' large quantities of chlorine, as in the waters tube with its contents. Pass a slow streaml of of saline springs, for examlple. In such cases pure, dry chlorine gas through the tube, heat the bromine must be concentratetd either by the silver salts to fusion and shake the bulb fractional precipitation with nitrate of silver, occasionally, in order'to expose friesh surfitces as has been described above (Principle I), by of the fused mass to the chlorine. After the fractional solution (see Bromide of Sodium), lapse of 20 or 30 minutes, allow the tube to or by fiactional dlistillation (see Bromine). cool, detach it front the chlorine generator, It is easy to control the results obtained by hold it in an oblique position until the this ilethod by treating the residual chloride 54 BROMINE. of silver with hydrogen, as described under large proportion of chlorides, mix the solution Ptrinciple II. The difference between the in a flask with chlorhydric acid and binoxide of weight of tile mixed bromide and chloride of manganese, connect the flask with two wide tilver,,Wnd the amount of chlori(le of silver Woulf bottles, by means of bent (lelivery equivalent to it found in the d(lirect way by the tubes. Chargle the bottles with strong anlmIo4ietho(l now in question, and by calculation in nia-water and( slowly heat the mnixture in the the methodl by hy(lrogen, should be the same. flask. The whole of the bromine will pass Bromide of Potassium. over befbre nmuch, if any, chlorine is evolved. Principle. Power of decomposing fieshly The bottles must be large enough and the disprecipitatedl chloride of silver. tillation slow enough that no vapors shall Application. Separation of Bromine, Iodine escape. When all the bromine has been and Chlorine. evolved, as may be seen by the color of the Mliethod. See Iodide of Potassium. gas in the tubes and in the flask above the Bromide of Sodium. liquid, loosen the cork of the flask to prevent JPrinciple. Solubility in strong alcohol. the return of bromide of ammonium fumes, let Applicatiorns. Separation of bromine from the bottles cool and unite their contents. The chlorine, or rather concentration of bromine liquid, which contains all the brolnine in the when Imixed with chlorides. substance analyzed, together with a relatively Mletfhod. Add an excess of carbonate of small proportion of chlorine, may then be sodium to the mix-ed solution of bromlides and analyzed by one of the methods described chlorides, filter if need be, evaporate nearly to under Bromide of Silver. drvness, and extract the residue with hot abso- Principle 1I. Power of decomposing iodide lute alcohol. The whole of the bromide of of potassium and other metallic iodides. sodium [or of potassium] will dissolve together Applications. Estimation of free bromine with a small portion of chloride of sodium. (Method A); estimation of iodine in presence Add to the solution a drop or two of a solution of bromine and chlorine (Method B). of carbonate of sodium, evaporate to dryness, llMethod A. Bring the gaseous bromine or dissolve the residue in water, acidulate with the bromine water to be analyzed into contact nitric acid, precipitate with nitrate of silver with a solution of iodide of potassium and. and analyze the mixture of bromide and determine how much iodine is set free, by chloride of silver, as described under Bromide titrating with a standard solution of hyposulof' Silver. (Compare MIarchand, Jouraz. prakt. phlite of sodium, sulphurous acid, arsenite of Chem., 47. 363). sodium or somle other reducing agent (see Bromine is commonly determined as Iodine). One equivalent of iodine is set free Bromlide of Silver, or as Bromine (by volu- by each equivalent o' bromine in the substance metric and colorinetric methods, or by loss). analyzed. [See the finding list in Appendix]. If bromine water is to be tested, the portion Princijple I, Volatility. to be analyzed may be measured in a pipette Applications. Estination of bromine in provided with a tube charged with moist metallic bromides. Separation of bromine hydrate of potassium, to protect the lungs of, from chlorine, or rather concentration of the operatpr, and the liquid may simply be bromine wvhen mixed with chlorides. stirred into a solution of 1 part iodide of _Method A. Place the dry weighed bromide potassiutm in 10 parts of water. The formain'a porcelain crucible, mix it with pure sul- tion of a black precipitate of iodine in the plihuric acid in slight excess, and evaporate liquid would indicate that an insufficient until no more fumnes are seen to,arise fiom the quantity of iodide of potassium had been dry residue. Wreigh the residual imetallic taken. - If the bromine is evolved in the sulphate, calculate tlhm amount of iletal in this form of gas, it ilay be collected in a series of sulphate and subtract it from the weight of the two or three small flasks, or miniature Woulfe bromide taken; the difference gives the weight bottles charged with the solution of' iodide of of bromline in the samiple analyzed. The potassium and tightly connected with one method is inapplicable for the analysis of the another anid with the generating flask. At bromides.of silver, lead, nmercury and tin, the mouth of' the flask in which the bromine is since these compourrds are not rea(tily decoin- generated, it is well to have a wide bulb tube, posed by sulphuric acid. -- Platinum cru- slanting back towxards the flask, in order to cibles cannot be employed; the metal would be condense aqueous vaIpor and return it to the attacked by the escaping ]bromine. flask. - The niethod yields accurate results Method B. Supersaturate the bromide to and is easily executed. be analyzed with chlorhydrie acid, e'vaporate If the solution to be analrzed contains to dryness to expel the excess of acid, and es- bromhydric acid or a metallic bromide, as well timate the chlorine in the residue as Chloride as free bronmine, determine the free bromine ir of'Silver, by titration. Fronl the weight of a xei-hed portion of it xith iodide of potassium chlorine found calculate the equivalent weight as above described. Mix another portion wvithm of' brolmine. (Mlohr). anl excess of sulphliurous acid ini aqueous solu-'To concenltrate bromine when mixed with a tion, allow the mixture to stand fbr some time, BROMINE. 55 acidulate with nitric acid and determine the rapidly. A standard solution of it cannot be whole of the bromine as Bromide of Silver. kept during 24 hours. He finds, moreover, that The difference between the two determinations the amount of iodine set free is not always gives the weight of the combined bromine. equivalent to the quantity of bromine used; If the bromine under examination contains in one experiment as much as three equivalents chlorine, the proportion of the two elements of bromine were required to liberate the may be determined as follows: — Let A repre- iodine. Before proceeding to the actual sent the weight of the impure bromine taken, analysis he therefore determines empirically i the weight of the iodine found, y the weight the value of his bromine water by titrating of the chlorine in A, and x that of the bromine with it a known weight of iodide of potassium. in A, then In case iodine is to be determined in solutions y -i-1.59e66 A; and A- = A- containing but little more than 1 milligramme 1 n991' of the element in 10 c. c., a standard solution (Bunsen, Annal. Chem. und Pharm., 86. of iodide of potassium is first prepared of such 276). strength that each c. c. of it shall contain 1 Method B. Prepare a standard solution of milligramnme of the iodide. 1 c. c. of this bromine by dissolving 1 grinm. of bromine in 4 solution is placed in a graduated tube, diluted litres of water. At the moment of use place with water to 10 c. c. andl tested with chloro40 c. c. of this solution (= 0.01 gri. of form and bromine water, according to De bromine) in a litre flask and dilute with water Luca's directions. The bromine water should to the mark (see Alkalimetry) in order to contain about 1 milligrm. of bromine to the obtain a solution containing Ad- milligramme c. c. and had better be poured from a burette of bromine in each cubic centimetre. If the marking tenths of cubic centimetres.. The iodide solution to be tested is alkaline, neutral- quantity of bromine water which represents 1 ize it with dilute nitric acid, then add to it, by milligrm. of' KI, or the 0.000763 grm. I, therein means of a graduated pipette, a definite contained, having thus been determined, the number of drops (say one c. c.) of bisulphide actual analysis of any unknown iodide solution of carbon or of chloroform and from another of the given strength may be undertaken. A pipette or burette pour upon the mixture a similar method of' procedure is applicable to stated number of drops of the weak bromine solutions containing less than 0.5 milligramme water. On shaking the mixture the bisulphide of iodine in 10 c. c.; but in that case two of carbon or the chloroform will dissolve the standard solutions of bromine water are needed, iodine which has been set free and willbecome the one containing 1 inilligrm. of bromine violet-colored. As soon as the color ceases to and the other 10 milligrnms. to the c. c. The become deeper on shaking the mixture after strength of any unknown solution must be the addition of a drop of the bromine water, determined approximately by a preliminary remove the colored bisulphide with a pipette trial. and replace it with a fresh quantity, equal to In case bromine, chlorine and iodine are all that first taken, add a further portion of the to be determined, I)e Luca precipitates one bromine water, and continue to repeat these portion of' the solution completely with a operations until the last portion of bisulphide standard solution of nitrate of silver (see or of chloroform fails to become violet-colored Chloride of Silver); determines the iodine as after the addition of the bromine. The above described in another portion, and the quantity of standard bromine water used, bromine and iodine together in a third portion minus the last portion which failed to impart by means of a standard. solution of Chlorine. any violet color to the test liquid, is equivalent Principle Ill. Power of oxidizing the to the amount of iodine in the substance lower oxides of iron, manganese, and some tested. Both bisulphide of carbon and other metals, ferrous salts, sulphurous acid, chloroform are capable of indicating the hyposulphites, etc., etc. presence of exceedingly minute traces of free Applications. Precipitation of manganese iodine. Bromine alone colors bisulphide of as binoxide. Estimation of free bromine, carbon yellow. An excess of bromine in either in aqueous solution or in the gaseous presence of iodine yields bromide of iodine form. Estimation of free bromine in presence which imparts no violet color to the bisulphide. of' chlorine. In order to judge of the intensity of the lMethods. Similar to those described under coloration, similar amounts of the bisnlphide Chlorine. For precipitating binOxide of Manshould be added throughout the experiment. ganese, in particular, from acetic acid solu(De Luca, Comptes Rendus, 37. 866). Ac- tions, and for oxidizing manganous salts before cording to Fresenius this method is neither so precipitating the metal as Hydrate of sesquiconvenient nor so practical as the analagous oxide of Manganese, bromine will be found method of Dupr6, in which Chlorine is used (after Henry) to be a much more convenient in place of bromine.' agent than chlorine. - In case free According to Casaseca (Ann. Ch. et Phys., bromine contaminated with chlorine is to be (3), 45. 482) the method above described is estimated, weigh out some of the substance in faulty, inasmuch as bromine water decomposes a small glass bulb, treat it with a cold aqueous 56' CADMIUM. solution of sulphurous acid and precipitate cadmium. For the separation of cadmium with nitrate of' silver. Digest the mixed pre- from other elements see finding list in the cipitate of bromide and chloride of silver with Appendix. nitric acitl to dissolve any sulphite of silver Prin-ciple. Insolubility in dilute acids when which may have gone down, wash, dry and in presence of metallic zinc. weigh. - Tf A e(lual the weight of sub- _Iiethod. Place a rod of pure zinc in the stance taken, B that of the AgC1l plus AgBr dilute sulphuric, chlorhydric, or even nitric obtained, x the weight of bromine in the acid solution of the cadmium compound, wash substance taken, and y the weight of the the precipitated cadmium with hot water, dry chlorine, then (best in an atmosphere of some nonoxidizing y -]2-5 -; and x A-y. gas), and weigh. (Pfolff, Ianldbuch analyyt. 16Chei., 1825, 2. 391; Mieissner, Gil/ert's An(Bunsen, Annal. Chenm. und Pharm., 86. nalen, 49. 99). According to WVollaston 2 76). (Schlweigger's Jahrb., 4. 371), it is best, after Principle IV. Decoloration of by oil of tur- any heavy metals which may be present have pentine (substitution of Br for H in the oil). been thrown down by iron and separated by Application. Estimation of free bromine. filtration, to put the chlorhydric acid solution Method. Dissolve 20 granmmes of perfectly of cadmium, etc., in a platinum dislh with a pure oil of turpentine in enough absolute alco- piece of zinc. The metallic cadmium will in hol that the mixture may be equal to 200 c. c. this case adhere firmly to the platinum and 34 c. c. of this liquid (-= 1 equivalent of oil may consequently be washed with peculiar of turpentine) correspond to 8 grins., or 1 ease. It may either be weighed as such, after equivalent, of bromine. Place the solution of drying, or dissolved in chlorhydric acid and bromine to be analyzed in a stoppered bottle, reprecipitated as' arbonate of Cadmium. add the oil of turpentine solution drop by Calci um may be determined as Carbonate, drop, shaking the bottle after each addition, Oxide, Oxalate, or Sulphate. For its estimauntil the mixture has become perfectly color- tion by alkalimetric methods see the Carbonless. One equivalent of oil of turpentine ate, Oxalate and Oxide. For the separation takes up and decolorizes 1 equivalent of bromine. of calcium fromn each of the other elements see The process yields satisfactory results, but is finding list in the Appendix. less convenient than the method with iodide of Cantharidin. potassium (see Principle II). In case very Principle. Sparing solubility in bisulphide small quantities of bromine are to be estimated, of carbon, and in alcohol. a more dilute solution of oil of turpentine Application.s. Separation of cantharidin from should be used than that given above. fats and oils. Estimation of cantharidin in Principle VI' Power of decomposing ammno- Spanish fies. nia with evolution of nitrogen. (See Nitrogen liethod. Plug the throat of a funnel or perCompounds). colation cylinder with cotton wool, pour fine Principle VI. Power of coloring ether, sand upon the cotton to the depth of 10 or 15 water, and chloroform. m. m., and place about 40 grins. of finely Applications. Estimation of brolnhydric powdered cantharides above the sLnd. Exhaust acid or combined bromine, even in presence of' the powder thoroughly and methodically with chlorides. Especially usefil for determining ether or chloroform. Evaporate the solution small quantities of bromine. to dryness and heat the residue, at a temlperaMlethods. See Chlorine, power of decona- ture no higher than 400, until it ceases to posing metallic bromides. smell of the ether or chlorofornm. Allow the Principle VII. Affinity for metals of the residue tocool and pour upon it 50 or 60 c. c. of alkalies and alkaline earths at highl temper- bisulphidle ofcarbon. ~'When the mass becomes atures. pulverulent, transfer it to a weighed filter antl Application. Estimation of bromrine in or- wash the crystals of cantharidin with bisulganic substances.. phide of carbon until the last traces of oil fiethods. Ignite the substance with quick- have been remloved. Finally dry and weigh lime, or thelike, dissolve the resulting bromide the filter with its contents. (_Mortreux, Journ. of calcium in water and precipitate Bromide Pharmn. et Chirn., 46. 33). of Silver. For the details of the igolition see DraoendorfF & B13lum (Zeitsch. analyt. Chewn., Chlorine. 1867, 6. 126) mix 25 or 30 grins. of' powdered Brucin. [Compare Iodo-mercurate of cantharides with 8 or 10 grins. of calcined Brucin.] mragnesia, moisten the mixture with water and Principle. Solubility in benzole. rub it to a paste. The, paste is then dried on Application. Separation of brucin from a water bath, the dry product rubbed to powder strychnin. and enouglh dilute sulphuric acid added to;Metahod. See Strychnin. slightly supersaturate th} magnesia. Imamie-' cdiatelv after adding the acid the mixture is Cadmium may be determined as Oxide, shaken with snmall successive quantities of Sulphide or Carbonate, or as metallic ether as long as any cantharidin continues to CARBON. 57 be dissolved. The several ethereal solutions with 1 vol. of chlorhydric acid of 1.12 sp. gr. are mixed, the mixture is shaken with water Connect the pincers with the positive pole of a and the ether recovered by distillation. The single Bunsen element, by means of a.opper residue from the distillation, — consisting of wire. Immlerse a strip of platinum foil in the crystals of cantharidin, fat and a yellox, dish of chlorhydric acid and by means of' substance, - is transferred to a tared filter another wire attach it to the negative pole of and washed first with bisulphide of carbon to the element. Regulate the strength of' the remove fat, and afterwards with alcohol to galvanic current in such wise that no sesquidissolve the yellow substance. The canthari- chloride of iron shall be formed. That is to din is then dried at 1000 and weighed. Cor- say, increase or diminish the distance between rections should be applied to comnpensate for the electrodes. To do this, move the foil away the solubility of cantharidin in bisulphide of from or towards the lump of iron. The carbon and in alcohol, as follows: - For every presence of any ferric chloride is, for that 10 c. c. of bisulphide of carbon used add 0.0085 matter, immediately made manifest by the yelgrm. to the amount of cantharidin actually lowish tinge which it imparts to the stream of weighed, and for every 10 c. c. of alcohol add concentrated ferrous chloride flowing downr).0024 grin. - Instead of magnesia, oxide ward from the piece of iron. During the of zinc may be used' and, instead of extracting process of solution the external appearance of at once with ether, the slightly acid mixture the lump of iron undergoes but little change, of sulphate of magnesium, sulphuric acid and for the carbon and other insoluble matter cantharides may be evaporated to dryness and retains the original form of the lump. the dry mass extracted with ether or with After about 12 hours, when all the iron,chloroforll. No cantharidin is lost by volatil- which was immersed in the acid has dissolved, ization during the distillation of the ethereal break off from the mass of carbon the compact solution. piece of iron which has been nipped by the Carbon. [Compare Graphite; see also Ni- pincers, wash, dry and weigh it, and subtract trogen and Oxygen]. its weight from that of the original lump of Principle I. Insolubility in dilute chlorhy- iron, in order to obtain the weight of iron dric acid,1 or in solutions of sulphate of copper, which has really dissolved. Collect the carbon chloride of copper, chloride of iron, or acid- and other insoluble matter upon a tared filter ulated chromate of potassium, of asbestos, wash with hot water, dry at 1200 Application. Separation of carbon from -130~ in a current of air, and weigh. Transfer iron; - as in the analysis of cast-iron and the dry residue to a weighed porcelain boat, steel. rinse out the filtering tube with dry oxide of Method A. Solution of the iron?n dilute mercury and pour the rinsings upon the carbon chlorhydric acid, with the aid of a weak gal- in the boat. Place the boat in a glass tube vanic current. behind a column of oxide of copper, heat the Cast-Iron. In case the material to be operated latter to redness, ignite the contents of the upon is white or gray cast-iron, weigh out a boat in a current of oxygen gas, in the manner lump (10 or 15 grins.) of the iron and suspend explained below (Principle II), and collect it in dilute chlorhydric acid by means of plat- the Carbonic Acid in a weighed quantity of inum-pointed pincers, in such manner that that potash lye or soda-lime. An unweighed chloportion of the mass which is in contact with ride of calcium tube may be employed to the platinum shall not be moistened by the catch the vapor of mercury. Finally weigh the acid. Or, in default of pincers, lay the iron incombustible residue of slag and silica in the upon a small sieve ef platinum and sink the boat. -- The process yields good results as sieve in the dilute acid. The dilute acid may compared with most other processes, and has be prepared by mixing about 12 vols. of water the very ~reat advantage of dispensing with the necessity oft reducing the iron to powder. Foran account of the liquid and gaseous hydro- Pecutios. Care must be tken to carbons which may be formed by the action of dilutes Care t be ten to acids upon white and gray cast-iron, see Hahn, Anna- maintain a weak galvanic current. The iron Zen Chem. und Pharm., 129. 57. See also Riinnman, should dissolve as protochloride and all the Zeitsch. analyt. Chem., 1865, 4.'159, who finds that hydrogen should escape from the surface of the pieces of thoroughly hardened steel leave no carbonaceous residue when treated with chlorhydric platinul foil. Little or no las should be acid of 1.12 sp. gr., and that the carbon which sepa- evolved from the surface of the lump of metal. rates from soft steel call all be destroyed byv dissolv- A strong current of galvanism would not only ing the steel in boiling chlorhydric acid of 1.12, and be apt to render the iron passive, but might continuing to boil the rmixed acid and residue for half occasion an evolution of chlorine from the an hour a'fter the metal has dissolved. On the other al houraafter the metal has dissolved. Oil the other surface of the iron, whereby some of the carbon hand, a considerable residue of carbon insoluble in hot acid is left when soft steel is slowly dissolved in would be oxidized and lost as carbonic oxide cold chlorhiydric acid. Sulphuric acid diluted with or carbonic acid. Another portion of the 5 parts of water yields results similar to those ob- carbon would unite with chlorine, and the tained owith chlorhydric acid, only the sulphuric acid must be boiled rmather more vigorously than the chllor- hydric in order that all the carbon shall be expelled the galvanic current, carbon would be st as (x hydrocarbon gas. free at the negative pole, together with hydro 58 CARBON. gen, in such manner that some of it might be Weigh out about 2 grinms. of the cast-iron, in lost in the form of a hydrocarbon gas. the form of borings if it be gray, or of coarse Thepoints of contact between thoplatinum powder if white, place it in a small beaker, pincers and the lump of metal must not be pour upon it a solution of 10 grins. of sulp)hate allowed to become moist lest the current be of copper in 50 c. c. of' water, heat the liquid impeded by the separation of a film of carbon gently and stir it frequently until the whole of between the platinum and the iron (Weyl, the iron has dissolved. Allow the mixture to Pogg. Ann., 114. 507). settle, decant the clear solution and oxidize The process as above described succeeds the moist residue with chromic acid in the well with specular iron, according to Weyl and manner explained below (Principle II, Method Fresenius (Zeitsch. analyt. Chem., 1864, 3. ~ 10). (Ullgren,'Aonal. C/hem. und Pharm., 124. 337, note). 59). Or, collect the carbon upon a filter of Steel. In the case of steel a new precaution asbestos, as already explained (A). is required, since the carbon, which separates Sulphate of copper is preferable to chloride when steel is dissolved in this way, is so finely of copper (Method C) since it may be divided that the particles do not cohere and heated without detriment to the analysis. The remain as a permanent mass at the positive solution of the iron is consequently far more pole of the battery. If the operation were rapid in this case than when chloride of copper conducted as above described most of the is employed. carbon would be transported to the negative MIethod C. Solution of the iron in chloride pole of the battery, there to be deposited in part ol copper. Weigh out about 5 grins. of the and in part to be lost through union with the finely divided metal, pour upon it a quantity nascent hydrogen and evolution as carburetted of a concentrated, neutral, or almost neutral, hydrogen gas. To prevent this waste of solution of cupric chloride, and let the mixture carbon, a porous membrane must be interposed stand at the ordinary temperature, with occabetween the fragment of steel and the negative sional stirring, until the whole of the iron has pole of the battery. The apparatus may be dissolved. The solution of chloride of copper prepared as follows: - Tie a piece of bladder must be as free from acid as possible, and over one end of a wide glass tube or broken rather more of it must be taken than would be cylinder, support the cylinder in a beaker half sufficient to convert all the iron into ferrous full of dilute chlorhydric acid, so that the chloride. The mixture must not be warmed, bladder end shall be immersed in the liquid lest subchloride of copper be formed and a near the bottom of the beaker, and pour dilute small amount of carburetted hydrogen evolved. chlorhydric acid into the cylinder until the (Karsten; Hahn, Annal. Chem. und Pharm., acid stands at sensibly the same level within 129. 76)'. By pressing the undissolved matter and without. Hang the weighed lump of with a glass rod it is easy to determine if any steel in the acid in the cylinder, immerse the hard lumps of iron are still mixed with it. platinum foil which serves as the negative pole When the last fragments of iron have dissolved of'the battery in the acid in the beaker, and and nothing is left but a crumbly mass of proceed as above described. After several metallic copper, free carbon and the insolhours a black deposit will sometimes form at uble impurities of the iron, mix the solution the negative pole of the battery, but it will be with a quantity of chlorhydric acid, together found to be readily soluble in chlorhydric acid, with some more chloride of copper, if this be and to consist of nothing but iron resulting needed, and wait until the whole of the copper from the electrolysis of chloride of iron which has dissolved to cupreous chloride. Collect has passed through the membrane. (Weyl, the carbon on a tared filter of asbestos (see A) Zeitsch. analyt. Chem., 1865, 4. 157). wash it first with water, then with chlorhydric The Asbestos Filter may be, prepared as acid to remove subchloride of copper, and follows: - Select a not too narrow glass tube, afterwards with water to remove the acid. heat a portion of it, near one end, cau- Dry at 120~-130~, weigh and 4arn to carbonic tiously in the lamp, and slowly draw out the acid, as in A. The carbonic acid should be softened and thickened glass in such manner made to pass through a sniall chloride of that this part of the tube shall be made much calcium tube on its way to the soda lime, since narrower than the rest. Push a loose plug of the carbon is always contaminated with a small asbestos down the longer portion of the original proportion of some hydrogen compound. This tube until it rests upon the beginning of the method, originally proposed by Berzelius narrowed portion. Fix the tube in an upright (Pogy. Ann., 46. 42), is still esteemed. position, and pour into it, upon the asbestos, (Compare M. Buchner, Bert. unnd Hiitteolm. the substance to be filtered. The asbestos Zeitung, 24. 84). According to Ullgren should be thoroughly boiled beforehand with (Annalen Chem. und Pharom., 124. 59) it chlorhydric acid to remove soluble impurities, yields results somewhat too high, since no and then ignited in a current of moist air to allowance is made for the nitrogen in the iron. expel any contamination of' fluorine. lethod D. Solution of the iron in chloride of MJlethod B. Solution oj' the iron in sull;hate iron. Add to a solution of ferric chloride enougrh of copper. carbonate of calcium to neutralize the free acid, CARBON. 59 and pour the filtered liquid upon the iron easily combustible, non-volatile, solid or liquid to be analyzed. The metallic iron will organic compounds. The apparatus required dissolve to ferrous chloride, and a mixture of consists of a combustion tube of' hard Bohemian carbon and other insoluble impurities, together glass, drawn up to a point at one end, as with a quantity of' muddy oxide of iron will described in works relating to chemical manipbe left. Dissolve this oxide in chblorhydric ulation; a combustion furnace; a light tube full acid, and collect and determine the carbon as of Chloride of Calcium (q. v.) for absorbing before. Both C and D succeed best when the water; a set of potash bulbs (see Hydrate of iron is finely divided. Potassium), and a soda lime tube (see Soda In order to pulverize hard cast-iron, beat Lime) for carbonic acid; an air pump or exthe metal to moderately small fragments upon hausting syringe, and a small copper dish or an anvil, crush the fragments in a steel mortar porcelain mortar for mixing the substancewith and sift the powder in a leaden sieve provided oxide of copper; besides corks, and connections with small apertures. The softer kinds of of narrow caoutchouc tubing. iron cannot be broken in this way. They must The combustion tube may be some 40 or 45 be filed to powder with a sharp file, after the c. m. long and should have an internal diameter external crust of dirt or oxide has been-filed of 12 or 14 c. m.; the glass of the tube should off. - In powdering highly graphitic iron be about 2 m. m. thick, and of the most ina very considerable loss of carbon may occur. fusible quality. Clean the tube from dust by (Booth & Morfit, Chemical Gazette, Vol. 11). wiping it out with a rag or piece of paper 3lethod E. Solution of the iron in acidulated attached to a wooden ramrod or to a blunt bichronmate of potassium. wire. The tube will be dried at a later period, Dilute a saturated aqueous solution of bichro- as will be explained. Fit to the tube three mate of potassium with an equal volume of excellent corks, and carefully perforate two of water and add as much sulphuric acid as will them, with a fine round file, in such manner be sufficient to saturate both the potash and that the narrow portion of the chloride of the chromic and ferric oxides which are to be calcium tube, described below, may fit the formed. By means of platinum pincers or hole, air tight. Each of the corks should fit wire, hang a lump of iron (10 or 15 grms.) the combustion tube so tightly that by pressing just beneath the surface of the liquid and leave strongly with the fingers no more than one it at rest. The iron will dissolve rapidly, third of the cork can be screwed into the without evolution of gas, while the carbon tube. The corks should be smooth, soft, and remains intact. The hydrogen which may be as free as possible from visible pores; they supposed to result from the action of the acid should be dried for a long time at 1000. The on the iron is immediately oxidized by the purpose of the second perforated cork is to chromic acid before it can become free or replace the first in case of accident. Instead combine with any of the carbon. The ferric of ordinary corks, perforated caoutchouc salt sinks to the bottom of the beaker as fast stoppers of good quality may be employed in as it is formed and soon renders the entire most cases. liquid opaque. The carbonaceous residue Charge the potash bulbs with a clear solution contains a large proportion of iron and appears of caustic potash of about 1.27 sp. gr.,tolerably to be a chemical compound of the two elements. free from carbonate. - Caustic soda will not That obtained from steel dissolves completely answer so well, since solutions of it are liable in chlorhydric acid with violent evolution of to froth. - Wipe the outside of the bulbs with hydrogen and carburetted hydrogen. For the a dry cloth and the insides of the ends of the method of estimating the carbon in the residue, tubes with slips of twisted filter paper. Close see A, B and C. the two ends of the apparatus with little caps Like Method A, this process dispenses with formed by plugging short pieces of rubber the trouble of pulverizing the iron. It appears tubing with bits of glass rod. Hang the bulbs to be specially adapted fobr the analysis of steel in a room not liable to wide or sudden fluctuaand white iron, since with specular iron a small tions of temperature, and leave them there quantity of hydrogen and carburettedhydrogen half an hour or more before weighing. is evolved during the process of' solution, unless Fill a bulbed chloride of calcium tiube with the solution of' chromic acid be very concen- small lumps of the porous chloride, wipe out trated. (Weyl, Zeitsch. analyt. Chem., 1865, the narrow portions of the tube, close the two 4. 158). ends of the tube with plugged caps as before, and place it in the room of constant temperaPrinciple II. Oxidation to carbonic acid, ture with the potash bulbs. by oxide of copper, chromate of lead, chromic Fill three quarters of another bulbed tube acid, oxygen or air. with granulated soda lime and the other Applications. Estimation of carbon in any quarter with small lumps of porous chloride of mixture or compound. calcilm, plug the ends of the tube and place Mi3ethod 1. Combustion with Oxide of copper. it with the others. (Liebig's method). Meanwhile put from 0.33 to 0.6 grm. of the The process is well suited for the analysis of substance to be analyzed in a sInal dry glass 60 CARBON. tube, 4 or 5 c. m. long by about 1 c. m. wide, short neck. - Pour some of the oxide of slip the tube into another somewhat larger tube copper from the combustion tube into the in such manner that it may be closed almost mortar, throw out upon this oxide of copper air tight, and weigh the tube and substance. the substance to be analyzed, fromn the tube in It is well to weighl the empty tubes roughly which it was weighed, taking care to shake the beforehand in order that a quantity of the tube so that little or none of the substance substance proper fobr an analysis may be taken shall remain adhering to it. Preserve the with certainty. The material to be analyzed empty tube carefully since it must be reweighed. should be perfectly dry and in the state of fine Pour more oxide of copper from the combustion powder; more or less of it should be taken ac- tube to cover the substance in the mortar and cording as it is supposed to be rich or poor mix the substance with the oxide by carefully in oxygen. rubbing the two together with the pestle, Weigh the potash bulbs and soda lime tube, taking care not to press upon the latter too andl finally the chloride of calcium tube. In strongly. Add to the mixture in the mortar case the balance is sensitive when heavily laden, all the oxide of copper in the tube excepting the potash bulbs and soda lime tube may be a layer of 3 or 4 c. m. at the very end and inweighed together. Take care to remove the corporate the matter thoroughly. Take out stoppers of the tubes before weighing and to the pestle from the mortar, shake it to remove replace them afterwards. adhering particles of the mixture, and lay it Fill a Hessian crucible of about 100 c. c. upon the glazed paper. Carefully tr'ansfer capacity nearly full with soft black oxide of the contents of the mortar to the combustion copper, - prepared by igniting nitrate of tube by repeatedlyl thrusting the mouth of the copper until no more nitrous fumes escape from tube into the mixture and then inverting the the mass, — cover the crucible carefilly with tube: to transfer the last remnants of the a tightly fitting cover, heat the crucible with mixture pour them upon a smooth card and its contents to dull redness in a small fire of thence into the tube. Pour a small quantity charcoal, and set it aside to cool. In case the of oxide of copper from the crucible into the substance to be analyzed is solid, a porcelain mortar, rub it about with the pestle so that mortar will be needed in which to mix the any particles of the mixture still adhering to substance with the oxide of copper. The the porcelain may be rinsed off, and transfer it mortar should be wide rather then deep, and to the tube. Repeat this operation of rinsing should have a lip. It should not be glazed until the combustion tube is full to within 3 or inside but must be free from cracks and flaws. 4 c. m. of its mouth, then push a not too tight Before use, the mortar should be washed clean, plug of asbestos or of copper turnings against dried thoroughly and kept in a warm place the oxide of copper to keep it in place and until needed. A shallow, oblong copper dish close the tube temporarily with a dry cork. or saucer, provided with a lip at one end, may The asbestos should be igfnited beforehand be employed with advantage for mixing the in a stream of moist air to remove fluorine, substance with oxide of' copper. and the copper turnings first in air and then The clean combustion tube should now be in hydrogen to free them from dirt. thoroughly dried by moving it quickly to and Rap the tube gently against the table until fro over a lamp - so that the entire length of its contents settle together to such an extent the tube may be heated, - and repeatedly that a narrow air-channel is left open above sucking out the hot air from within the tube, the oxide of copper from one end of the tube throughl a small, long glass tube which reaches to the other, for the passage of the gases which to its bottom. are to be evolved, and that the upturned posAs soon as the oxide of copper has cooled terior point of the tube is left clear. Carry to such an extent that the crucible which the tube to an air punp or simple exhaustinig contains it can just be held in the hand, pour syringe to which is attached a long tube fall a little of it into the porcelain moftar and of dry chloride of calcium, and connect the another small portion into the combustion tube, combustion tube with the latter, by means of a rinse out both mortar and tube with the warm perforated cork. Place the combustion tube -oxide, and then throw it aside. in a narrow wooden box or trough, fill the Spread a large sheet of glazed paper, such box with hot sand so that the entire length of as bookbinders use, upon a clean table, and the tube shall be covered with the sand and place the mortar upon it in order that nothing then slowly pump out the air which is contained may be lost in case of spilling. Fill nearly in the tube. The sand must not be hot enough two-thirds the length of the combustion tube to singe paper. The pumping must be careful with the warm oxide of copper, either by re- and deliberate or some of the contents of the peatedly thrusting the mouth of the tube into combustion tube will be carried out with the the oxide in the crucible held somewhat escaping air. After a moment slowly open the inclined,. and then inverting the tube, or by stop-cock of the pump so that fileshl air may dipping up the oxide with a tea spoon of enter the combustion tube. All the moisture German silver and pouring it into the tube contained in this fresh air will be stopped by the through a small, warlm copper funnel with a chloride of calcium, as well as that brought CARBON. 61 out of the tube in the exhausted air. Again from touching the substance after it has once carefully pump out air from the tube, then fallen out. As soon as the substance to be admit more air an(l continue to exhaust and to analyzed has been poured from the weighilng admit air alternately some 10 or 12 times in tube, bring the combustion tube into a horizonorder to remove the last traces of moisture tal position so that the weighing tube, still which may have been absorbed by the oxide of pressed against its upper side, shall be slightly copper during the operation of mixing. inclined, with the closed end downwards. Instead of operating as above described, a Then slowly withdraw the weighing tube, better way is to place the combustion tube taking care to turn it so that any portions of upright in a retort holder, to mixthe substance the substance which may have renairmed with oxide of copper in a small copper dish, attached to the rim of the tube may fIll back and to pour the mixture into the tube through into it. Close the empty tube and put it aside a smooth, warm copper funnel. The anterior to be weighed. - Transfer from the filling portion of the tube may then be filled with flask to the combustion tube another quantity a tightly packed laver, 20 c. m. long, of hard, of oxide of copper equal to the first, so that gray, granulated oxide of copper, which, unlike there shall be a column of oxide of copper 20 the soft oxide above described, has but little c. m. long at the end of the tube, with thle power of absorbing moisture from the air. substance in the middle of it.'o mix the (Mulder). By proceeding in this way the substance with the oxide of copper, provide a necessity of pumping may be done away long, bright, stiff iron wire, bent to a ring or with. loop at one end, for the handle, and at the other Bunsen's 3Modifcation. Another way of end pointed and twisted like a cork screw, avoiding the moisture of the air and of dispens- with a single twist, Push the screw end of the ing with the need of an air-pump has been in- wire deep into the oxide of copper and move dicated by Bunsen. This chemist directs that it about rapidly for a fiw minutes in all directhe substance to be analyzed be thrown direct- tions, so that the substance and oxide may be ly into the combustion tube and there mixed intimately mixed. Withdrawthe wire, transfer with oxide of copper by means of a twisted a new quantity of oxide of copper from the wire, instead of being rubbed with the oxide filling flask to the tuube, wipe the wire in this in a mortar or other dish. His process is par- oxide, and finally fill the tube with oxide of ticularly well adapted for the analysis of highly copper. - So little water is absorbed by hygroscopic bodies and of substances which the oxide of copper in this process that a single would be decomposed by warm oxide of charge of the filling flask may be made to copper. serve for several analyses. If the flask be proThe hot oxide of copper is transferred from vided with a tight cork the oxide of copper the crucible in which it was ignited to a warm, will remain several days fit for use, even though, dry glass flask, or wide tube closed at one end, the flask be repeatedly opened and portions of which is then corked tightly and left to cool. its contents withdrawn. (Bunsen, HanclderThe substance to be analyzed is meanwhile terbuch der Chemie, Supplement, p. 186). weighed in a long tube of thin glass provided As soon as the combustion tube has been with a cap cover, as described above. This properly filled, and freed from hygroscopic weighing tube should be about 20 c. m. long moisture, thrust the narrow end of the weighed and 6 or 7 m. m. wide. - As soon as the chloride of' calcium tube through one of the oxide of copper has become cold, uncork the dry perforated corks, twist the cork tightly flask or tube which contains it, thrust the end into the mouth of the combustion tube, and of the dry combustion tube through the neck place the latter in a "combustion furnace." of the flask into the oxid6 of copper, in such The combustion furnace may be fed with charmanner that a small quantity of the oxide inay coal, alcohol, or far better, with gas, in accordenter the tube; rinse the combustion tube with ance with almost any one of the numerous this oxide and throw the rinsings aside. Again plans described by works on chemical maniputhrust the combustion tube through the neck lation. Compare, for example, Baumhauer of the flask into the oxide of copper and take (Annul. Chem. undl Pharm., 90. 21), J. Lehup enough of the latter to form a column or mann (ibid, 10,2. 180), iHeintz (Pogg. ilna., layer about 10 c. m. deep at the posterior end 103, 142), Hofiann (Journal Chem. Soc., 11. of the tube. - The transfer of oxide from 30). the flask to the tube is readily effected by Copper foil for wrapping soft tubes. In case holding the tube in a slightly inclined position the coimbustion tube has to be made of glass and gently tapping the tube. - Open the which is not infusible enough to withstand weighing tube, thrust it as far as possible into the heat of the furnace, the tube should be the combustion tube, held slightly inclined, and wrapped in thin copper foil or galuze, and pour out the substance to be analyzed. In wound around with iron wire, before it is doing this, turn the weighing tube about so placed in the filrnace. Or the tube may be that its contents may fall out more readily, and laid in a shallow trough of sheet iron. at the sam.Pe time press its rim against the upper The combulstion tube shouli incline forwar( side of the combustion tube in order to keep it slightly, and its mlouth should project at least 62 CARBON. an inch beyond the edge of the furnace, and a the mixing mortar, or to wipe the mixing wire, screen of sheet iron should be placed at the and carbonic acid begins to be evolved, the edge of the furnace so as to protect the mouth rest of the air in the apparatus will escape in of the tube from excessive heat. Throughout large bubbles. But when the actual mixture the experiment the projecting part of' the tube is reached, the bubbles which pass into the should be kept so hot that the fingers can potash are nearly pure carbonic acid, sd hardly bear the shortest contact with it; but that only now and then a solitary air bubble no hotter than this, lest a portion of the cork will escape through the liquid. - The iheatbe burned, and the analysis thereby vitiated. ing of the tube should be so regulated that the By means of a short rubber connector, at- gas bubbles may follow one another at intervals tach the potash bulbs to the free end of the of from one-half to one second. chloride of calcium tube, taking care to place After about three quarters of an hour, when the largest bulb next to the chloride of cal- no more gas is evolved, although the tube is red cium tube, and tie the ends of the connectors hot from end to end, take avway the fire from, firmly to the glass with fine cords.'During the posterior end of' the tube, so that the upthe operation of tightening and tying the turned point may be free, and place a screen cords, the ends of the two thumbs should be between the point and the fire. The cooling pressed firmly together, so that no part of the of the end of the tube thus caused, taken in apparatus need be broken in case a cord hap- connection with the absorption of carbonic pens to give way. It is well, also, to rest the acid by the potash lye, will cause the latter to fragile bulbs upon a folded cloth, or some other be forced back into the large bulb. The liquid soft substance. To the free end of the potash will rise slowly at first, but with increased bulbs attach, with another connector, the sup- rapidity after it has once entered the large plementary soda lime tube, and support it in a bulb, but there is no danger of its flowing into horizontal position by means of a ring-stand, the chloride of calcium tube if the bulbs were or any other suitable prop. properly filled in the first place, and are now In order to determine whether the fittings set level. It may here be said, that during of the apparatus are air-tight, hold a tolerably the combustion it is well enough to place a large piece of glowing charcoal near the larg- cork, or a piece of wood as thick as a man's est potash bulb, so that the air within the bulb finger, beneath that end of the potash bulbs may be expanded, and in part driven out of (Liebig's bulbs) which is farthest from the the apparatus. After a certain amount of air large bulb, so that the liquid shall tend to has been expelled in this way, take away the flow into the large bulb. But as soon as gas coal. Note the height to which the potash bubbles cease to come forward, this prop solution rises in the large bulb to replace the must be removed, and the bulbs brought to a lost air, and observe whether the liquid re- level position. - At the moment when the mains at this height for the space of three or large bulb has become about half full of the four minutes. If the apparatus be tight, the potash lye, crush the end of the upturned liquid will remain at the highest level to which point of the combustion tube with a pair of it rose as the bulb cooled; hence, if it grad- stout pincers, and push over the stump a dry ually recedes finom the large bulb, and comes glass tube about 60 c. m. long, and open at to a common level in both limbs of the appara- both ends. Support this tube in an uprigllht tus, either one of the corks or connectors imiust position by means of a ring-stand. Attach a be leaky, or the apparatus somewhere cracked. long caoutchouc tube to the supplementary The weight of the empty weighing tube may soda-lime tube beyond the potash bulbs, bring be conveniently taken while the tightness of the potash bulbs to their original oblique posithe tube is being tested. tion, and with the mouth, or better with a Heating the tube. After the apparatus has small aspirator, suck air through the combusbeen proved to be tight, heat carefully two or tion tube until the bubbles which pass through three inches of the anterior portion of the the potash bulbs cease to diminish in size. An combustion tube until it is red hot, then slowly aspirator has an advantage in that it affords work backwards inch by inch, taking care to ocular evidence of the volume of air which is bring each section of the tube to redness be- drawn through the apparatus. fore proceeding to heat the next section. If Take the apparatus to pieces, stop the ends charcoal be used as the fuel, the unheated por- of the chloride of calciuin tubes and of tlhe tion of the tube must be protected from the potash bulbs with rubber connectors plug'ged1 radiant heat of the fire by means of a sheet- with glass, set the larger chloride of' calciull iron screen, which may be moved backwards at tube in a vertical position, with its bulb up1)will with a pair of tongs or pincers. ward, and leave the several pieces in the roomm When heat is first Applied to the tube, some of constant temperlature for half an haour be-; bubbles of air will be driven through the pot- fore weighing. The increased weight of the ash bulbs b)y virtue of simple exsIansion; atier- larger chloride of calcium tube gives the wards, Awhen the he:Lt h react s tlmes tl:)rti )on (of anllomit of, water pro.ducedl in thie commsllllltiam.a the. oxide of copper lvwhich was usedt to r'inse alnd friom this weight that ot' the yd(llrogtte ill CARBON. 63 the substance analyzed is obtained by the fol- be left uneonsumed with the mass of reduced lowing proportion:- copper. Rap the tube gently against the taMiolecular wt. Wt. of an wt of H in ble to clear a passage for the gases which are of18 sten ofH HWt. of wiundter (= substance ) to be evolved, and finally fill the anterior half The increased weight of the potash bulbs of the tube with small lumps of' hard oxide of and supplemlentary soda linme tube gives the copper, or with copper turnings which have weight of the carbonic acid, whence the weight been superficially oxidized, so that there may of carbon is derived by tihe propolrtion:-n be free passage for gases and vapors, although little or no visible channel is left open above llculwt Wghtofan C Wt of C02. eight of\ the mass. - After the chloride of calcium ofO atom of C e Sample. of ~z aomoI44 * 12in * ~ found 12 th esnmple. tube, potash bulbs, etc., have been attached to In practised hands, this comparatively old the combustion tube, place a screen at the process gives excellent results. It is, however, middle of the tube and heat the anterior colfar less convenient and trustworthy than the umn of oxide of copper to redness. Heat the process of combustion with oxide of copper in upturned, posterior point of the tube so that a current of oxygen gas (see below, Method no vapor shall condense in it, and place a hot 2), and is therefore seldom employed. - In coal, or an exceedingly small flame, near that operating with easily combustible substances part of the tube which contains one of the (and the process is really only suitable for the bulbs. The contents of the bulb should be analysis of such), it is easy to determine in driven out very slowly, and the whole operathis way the proportion of carbon with great tion conducted with extreme care. It is an accuracy, but as regards hydrogen, the results easy matter to lose an analysis by distilling the obtained are usually about 0.1 or 0.15 per cent substance rapidly, so that considerable quantihigrher than the truth. This excess of' hydro- ties of' partially burned material can escape gen comes in part from moisture absorbed by through the potash bulbs. - After the conthe oxide of copper, but mainly from the tents of the first weighed bulb have been moisture of the air, which is drawn through driven out and consumned, that part of the tube the apparatus at the close of the combustion which contains the second bulb may be heated. to remove the carbonic acid. The error can The combustion tube is finally heated from be corrected in good part by attaching, with a end to end, and the analysis finished in the perforated cork or rubber connector, a tube usual way. In the case of liquids which full of solid hydrate of potassium to the poste- are but slightly volatile, it is well to empty the rior point of the combustion tube, —in place of bulbs before the combustion begins, instead of the upright open tube above clescribed,-befbre heating them, as above described. To this beginning to suck air through the tube. end attach the filled combustion tube to an Volatile substances, and those liable to lose air pump, and give a single slow stroke with water, or to undergo other alterationz at 1000, the pump handle. The bubbles of air within may be analyzed in this way, though less read- the weighing bulbs will expand, and the liquid ily than by Method 2, by mixing them with be forced out to be absorbed by the oxide of cold oxide of copper, in the manner proposed copper. Bodies rich in carbon should never by Bunsen, see above, p. 61. be analyzed in this way; a supply of oxygen Volatile liquids, such as alcohol, ether, essen- gas is needed in order that their carbon may tial oils, and the like, had better be analyzed be completely consumed. See Methods 2 and 6. by Method 2 or 6. In case they are analyzed NAonvolatile Liquids are analyzed by Methods by Method 1, the combustion tube should 2, 3, 5 and 6. be 50 or 60 c. m. long, the oxide of copper litrogenrous Comp]ounds. When substances should be cooled in a flask (p. 61), and the containing nitrogen are ignited with oxide of liquid weighed in two or three small bulbs copper, most of the nitrogen goes forward in similar to those described under Method 2 the gaseous form, together with the carbonic only smaller. - Pour a layer of the cold acid and water, and escapes into the air as oxide of copper, 6 c. m. deep, into the corn- free nitrogen. A small quantity of the nitrobustion tube, scratch the stem of one of the gen, however, is converted into nitric oxide, bulbs with a file or steel glass-knife, break and the latter, on coming in contact with the off the point quickly with the thumb and potash lye, is partially decomposed to nitrous finger, and drop both bulb and point into acid, which combines with the potash. A the combustion tube. Pour another layer of partof the nitric oxide changes into hyponitric oxide of copper, 6 or 8 c. m. deep, into the acid also, by coming in contact with the air in tube to cover the bulb, throw in the second the apparatus, and the acid thus formed is abbulb in the same way as the first, and add an- sorbed, as well as the carbonic acid, in the other layer of oxide of copper. If the sub- potash bulbs. Though the amount of nitrous stance to be analyzed contains a large propeor- and nitric acids thus generated is never very tion of carbon, and is rather difficultly volatile, large, there is still enough formed in many the quantity (about 0.4 grin.) taken foibr analy- cases, especially in the comlbustion of sultsis, had better be weighed in three than il tvwo stances rich in oxygenl, to vitiate thie deterrimbulbs, in order that no particles of carbon may ination of carbon. Th'I'lle difllicultly t be oh 64 CARBON. viated in some cases by mixing the substance bulbs. (Liebig & Wcelhler). But according to very intimately with the oxide of copper, and Carius (Annal. Ch/em. und Pharm., 116. 28), conducting the comblustion very slowly. But all the sulphurous acid cannot be retained in as a genc1eral rule, the, oxides of nitrogven must this w'y l whei tlhe substance analyzed conita'ins be decomlposed by ibrinoin them in contact a laroe proplortion of sulphiir, and on tle with red hot metallic colpper.'he etal is other band, Bunsen has shown that bituoxide used either in the Gforiu of turnings, or of rolls of lead is capable of absorbing no incolnsideror spirals, made of vire or of strips of sheet able quantity of carbonic acid. Carius urges copper. The rolls or spirals may be 8 or 10 that sulphur compounds had better bie burned c. m. long, and just thick enough to be ad- with ehromate of lead. (See slethod 8). See mitted to the combustion tube. If turnings also Sulphur. are used, they may be compressed to a cylin- C(loi ea, B3ronline and iodine Cormpowuds. drical form, by forcing them while hot into a XWXhen organic substances containing, cllorine, short tube, a little narrower than that in which bromline or iodine are burned with oxide of the combustion is to be made. According to copper, subeliloride (bromide or iodide) of Scelroetter and Lautermann (Jour. pratll. C'heni., copper is ftrmed, some of which is liable 77. 316), the copper rolls or turfnings cannot to condense in the chloride of calcium tube be replaced by the mletallic powder obtained and vitiate the determination of' the hydrogin. by reducing oxide of' copper with hydrogen, HIence the comlpoun.tds in question are esually since the powder obstinately retains hydrogen, burned not with oxide of copper, but with cllrowhich, by reactinlg upon carbonic acid in the mate of lead (Miethod 8).. Compare MIethod 2o process of the combustion, causes an appre- In A?/olyziig Copoaaldl, which contCai Inciable quantity of carbon to be lost as carbonic oracnic C'o;stittets, othler than those allowed oxide. -- The rolls or plugs of copper are for in the preceding paragraphs, the )roportion first heated to redness in the air in a Hessian of inorganic matter must be determined in a crucible, until the surface of the mletal is oxi- special piortion of the material. The alnalysis dized, and the last trace of dust and oil has of such comlpounds presents no particular diffih been burned off'; they are then heated in a culty unless a volatile metal like mercury or a tube in a stream of hydrogen, until the oxide metal capable of retaining more or less carbonic has all been reduced. Since recently reduced acid, — such as potassiuni, sodium, caleium, copper retains hydrogen gas, and on exposure strontium or barium, be present. In the comto the air absorbs aqueous vapor, it should bustion of' substances rwhichl contain mercury, always be heated to 100~ in the air for some a layer of copper turnings (see Mitrogenous time befbore it is used, and should be as nearly substances, above) may be placed in the anteas possible at this temperature when intro- rior part of' the comblustio n tube in ollder to d(uced into the combustion tube. - The retain the metal witlin the tube. Care must combustion tube, which should be 12 or 15 be taken not to heat this copper too strongly. c. in. longer than if it were to be employetl for If the substance to be analyzed containes analyzing a body free from nitro(gen, is filled metals capable of retaining caibonic acid, a in the usual way, with this exception, that quantity of sonme substance capable of decomenough metallic copper is placed at the ante- posing the carbonates in question at hilh tenlriort end, to form a column 10 or 12 c. mI. long. perature may be addedi to the oxide of' copper As soon as the tube is laid in the furnace, the with which the substance is nmixed; either metallic copper is heated to bright redness be- teroxide of' antimony, phosphate of copper or fore proceeding to the ordinary steps of the boracic acid, will answer the purpose. See analysis. tHot copper decomposes all the oxides also Method 9, and the relmarks on same subof nitrogen, fixing the oxygen while nitrogen ject under AMethod 2. goes free; but since this action occurs only when the metal is intensely ignited, care must _Method 2. Coo~bditstion w?/ith oxide of copper, be taken to keep the metal hot throughout the in coniiluction with oxryen gas forced Jionom a entire combustion. Compare the heading, gas-h-older. Nitrogenous Compounds, under Method 2. In this process the substance to be analyzed, Sulphur CJompoundCls. III determining the or at least the volatile pirodctits given off fioam carbon of compounds which contain sulphur it by distillation, is heated in contact wvith oxas well as carbon, hydlrogen, oxygen or nitro- ide of copper in the ii(dst of a slow current of gen, it has hitherto been customary to proceed, oxygen gts which is made, to flow in c( otinuas above deseribed, as if notling but carbon, ally upon the mixtLure fiomn a gas-holdlr. Ilie hydrogen and oxygen (or nitrogen) were pres- metlhod, besitles beisig siuitable for tlhe analysis ent, but to place between the chloride of cal- of didicutll colnbustidle substances, is of?'encium tube and the potash bulbs a narrow tube, erll applicability ior the estimation of ctarbl,, 10 or 12 c. ni. long, filled with dry binoxitle of anl hydrogen in all orgainic substances. It leal, in order to absorb the sulphulrous acid will be fou)lnd particeil:rtly conxvenient whenl formed by the oxidation of the sulphul, which seveiral anlilyscs atrc to be atlde ii siicessioin, would otherwise be absoirbed in the potash and in cases wherei fi'ln our inability to pul CARBON. 65 verize the substance to be analyzed it cannot of calcium. In order that a single set of the be intimately mixed with oxide of copper or tubes may serve for both gas-holders without any other solid oxidizing agent. inconvenience, a supplementary flask may be Besides the apparatus described under Method attached to the set, as follows: F- it to a small, 1, the process now in question requires a couple wide mouthed flask a caoutchouc stopper, with of gas-holders.and a permanent set of drying three perforations. Provide three glass tubes tubes. For a simple and inexpensive form of suited to the stopper and each bent at a right gas-holder, see Eliot & Storer's Manual of In- angle. One of the tubes is a simple abduction organic Chemistry, Appendix ~ 11, Fig. xvii. tube only long enough to pass through the stopProvide a straight combustion tube open at per, while the other two must be long enough both ends, about 60 c. m. long, and of any to reach almost to the bottom of the flask. Fill width to which corks can be conveniently the flask one-third full of strong potash lye, fitted. Fit sound corks to both ends of the place it between the gas-holders and the sultube. Perforate the corks so that one of them phuric acid bulbs and attach it to the latter by may fit the weighed chloride of calcium tube, means of a rubber connector, tied to the short and the other a short, straight tube of diameter abduction tube. To the other end of each of proper to be connected with the permanent the longer tubes tie a piece of thick caoutchouc drying tubes; then dry the corks at 100~. tubing about 3 inches long, close each of' these Place a tolerable compact, plug of clean cop- rubber connectors with a spring clip, and by per turnings or a loose plug of asbestos (pre- means of glass tubes attach one of them to the viously ignited in a current of moist air in opening of the gas-holder which contains air and order to remove fluorine) in the combustion the other to the oxygen-holder. By opening one tube at a distance of 4 or 5 c. m. from its or the other of the clips, air or oxygen may be anterior end, pour enough oxide of copper made to flow into the combustion tube at will, into the tube to fill two-thirds of it, and push and by renewing from time to time the potash down upon the oxide of copper another loose lye and the sulphuric acid in the flask and plug of asbestos to keep the column in place. bulbs the efficiency of the apparatus may be A space about 20 c. m. long should be left open kept up for a long time. (Piria, Kopp' Will's at the posterior end of the tube. The oxide of Jahresbericht, 1857, p. 573). copper had better be in the form of coarse As soon as the combustion tube has been granules free ftrom dust; it need not be dried laid in the furnace, start a slowv current of air or ignited before beingf placed in the tube. through the tube and heat it throughout its enOr, instead of mere oxide of copper, the tube tire length, at first very gently but afterwards may be charged with a mixture of asbestos to low redness, in order to dry the oxide of and fine oxide of copper. When mixed with copper. During this prelilmlinary ignition leave asbestos, the oxide of copper in the tube will the anterior end of the tube open, but as soon be light as well as porous, and the tube will as the tube has been thoroughly heated close it better preserve its shape when heated. with a dry cork carrying an unweighed chloride Lay the tube in a shallow trough or gutter of calcium tube, extinguish the fire, and withof sheet iron, upon a thin laver of calcined out interrupting the slow current of air, allow magnesia or of asbestos, and place the gutter the tube to cool. and tube in the combustion furnace. Weigh out the substance to be analyzed, in Unless the glass of the combustion tube is of a small boat of platinum, copper, porcelain or the most refractory character the tube had glass, inclosed in a glass weighing turbe which better be coated with clay or with asbestos, and has been weighed together with the )oat b)elore then covered with copper foil bound round with the introduction of the substance. Push the copper or iron wire, before it is placed in the loaded boat into the posterior end of the cornfurnace. The furnace may be heated with al- bustion tube until it almost touches the asbestos cohol or with charcoal, in default of gas. plug, replace the cork at the end of the coinThe posterior end of the combustion tube is bustion tube and for the time beino shut off in the next place connected with the Permna- the current of air. It is well to lay two or nent drying (or rather, cleaning) tubes. three fibres of asbestos beneath the boat to These tubes, which serve to purify air and prevent it fron fusing to the glass. From 0.3 oxygen for the analysis, stand between the to 0.5 gin. of substance should be taken as a combustion tube and the gas-holders which reneral rule, tlhoullo less of the substalnce will supply air and oxygen; they may consist of a be needed in proportion as it (contains more set of' large potash bulbs filled with oil of vit- carbon; 0.2 of a g'lm. of material is sufficient riol, a large U-tube full of soda-lime, and an- for the anialy sis ot' man hSydrocarbons. other U-tube filled with chloride of calcium. After the boat ihas teen introduced, remove The sulphuric acid bulbs are attached to the the unwlei-hie(l ch;toridee of' calcium tube friol gas-holder, while the chloride of' calcium tube the anterior end of the combustion tube, reis connected with the posterior end of the con- place it with the weighed chloride of' calcium bustion tube. Where many analyses are to be tube and attach to the latter tlhe weighed potniade, it is well to have two or three soda —limne ash bulbs land the soIla-lime tube as described tubes and as many ilmore charged with chloride under Method 1 (see p. 62). 5 66 CARBON. In order to determine whether the apparatus the tube, as follows - The anterior portion of is tioht, open the cock of the oxygen gas- a tube 80-85 c. m. long is filled with granulated holder sliglitly so that a very slow current of oxidle of copper, as above described, the boat the gas may pass thrlouoh the tube, and after loadedl nitlI the substance is pushle(l il nearly a imoment suddenly close it again. Tlien atch to the oxide of col)per and a coul)le oi coils of the level of tlie liquid in the potash bulbs. If superficdially oxidized copper foil are tlhrust in the liquid does not sink back fi'om the outer- behindcl the boat. The tube and oxide of copmost bulb in the course of a few minutes the per are dried in a curr'ent of air in the usual apparatus is tight enough for use. In applyin"g way, but in making the colmbustion the postethis test the tube must of course be as cold as riol portion of the tube is heated to redness, the surroundin( air. - Place a sheet iron as wvell as the anterior portion, betore the subscreen across the end of the tube to protect stanice to be analy-zed is wiarnie(. Screens are the cork friom the fire and proceed to heat the employedt to protect tlhat portion of the tube oxide of copper in the tube, with the exception which cont;ains thle substance, while the rest of of a couple of inches next the substance to be the tube is being heated. analyzed, and as soon as it has become red Instead of placing the substance to be anahot start a slow currellt of oxygen through the lyzed in a boat, as above described. it nlmay be tube. Then slowly heat the rest of the oxide mIiixed directly with a part of the oxide ofi copof copper, anid firnally the substance itself; with per in thle tube. To this end, weilgh the subextreme care. The substance must neither be stance in a loni, narrowi, r irweidlilg' tube (see p. heated too quickly nor the stream of oxygen 61), anid pourl it upon the posterior end of the niadle too strong. It is to be remenlbered, how- colunlin of oxide of copper (see p. 65) after the ever, that an amply supply of oxygen will be most latter has been dried in a curreint of air in thle needed at the iiioiiient wslien the substance is usual wsay, and allowed to become cold. Mlix distilling niost rapidly. There is no harnl in the substance with the oxide of copper by means using so mutlch oxayen that an excess of it shaill of a tw-isted iron wire, such as Iias eeen deslowly bubble throue"h the potash bulbs f'roini first scrib)ed on p. G1, and thenl fill the tul)e to to last. In order that the current of oxv(en awithin about 12 c. in. of' its endil awiti coairise niay be reatily controlled and nicely adcjusted oxide of copper, wahich has previously b hen the cock of' tlie oxyv(en gas-holder should be io:nitedl, aid cooled. in a coirked ustsk (see pro itl1 vithi a longle r. s.;i ). T'ap the tufbe eunti y ao in t tli tafble W hen thle substance to be tnalazetC d has t slhake (ivw\rn tie oxie of' cOl!e' so toi:ft s a been cc:mletelyv s lx tune.l andi the cilaractir of n.:t'row prssal:e ma:y- Ie ieft above it. tieplace the bubbles in the poitias apparatus s is icates tle e tuIbe in the uIlrnce, and connect its posthat no mlore carilonic acid is comlirng forwardl? teior end a.it thle perlnlenit (ry-ing tu)es, shut off tle oxy-en, turn on air, and allow the and attach to it the avweighed chloride(l of calapparatus to ct ol in a slow streamr of air. cium tube, potash bulbs, etc. Start a very Since osygen is heaviel than air it is imnpor- slow ecurient of oxa'een thiouh fli the tubllet nd tant to expel it thoroughllly ftiom the potash prhoceedt to heat first the anterior colniiun of bulbs. Enougl air will have been passedl oxide of copper, then the mixturue, andsl finally throuoh the tube awhioen a glowin"g spliniter of' the l)osterior colunin of oxide, worokinll backwoodl ceases either to burst into fla me or to wxards always fi'om the fiont end of the tube. glow vividl whlien held in the air wN-hiech issues Take care to protect loth the coirks aw.il i sheetfi'on the vei hedoc soda-linme tsbe. - As iron screens. A mlloveable screen wjill ble foudlll soon1 as all the oxysgeni has beeni forced out of usefil, also, fo)r regulating the heat -at tll'it the apl)l)atus, sremt-iov e the ehlloride of calciuin parit of' the tuble -which contains the nsixt-lire. tube, the soda-laimle tube andt the potash bulbs Thlroughout the analysis cause a slow current to the roiom of constiint temiperaturte, and after of' oxygen. to pass thrllloulh the tube. The hIalf all hour aweiob1 themi as (iirectedl in'Meihod str'eamli shlould be so slow, hoawever, thalt Ino 1 (p. 62). VWithidriaw tlhe boat froml the combiiius- oxygen slhll escape thiiouglh the potasls bulbs tion tube and wvei'hL the ashes containet in it, wahile the substance is actually burning. After if' any there be. Unless some accident occur, the the evolution of caibonic acid has ceased, force comibustioni tubce and oxide of copper are left in a more rapid c.urrent of' oxygen into the tube perfect order -for a nicaw analysis. The operator until the reduced oxide of' copper has been has only to pushl another boat charged with a completely revivified, and finally tlllrov in a new quantity of' substance into the tube and to current of air to sweep out the excess of oxyattach another set of' weighed chloride of cal- gen. As a general rule, however, it will be cium tubes, etc., to the anterior end of the found more convenient and satisfactoi'y to tube. make use of a boat instead of mixingr thie subTo guard against the possibility of the es- stance with oxide of copper. When boats are cape of' any of thle products of distillation back- employed, the same conmbustion tube niay not wvards to the cork and drying tubes, Piria, only be used over and over again for ilany (Kopp - Wtill's Jlahresbericht, 15.7, p. 573) in- analyses, but needs absolutely no preparation terposes hot oxide of copper between the sub- after one anaJysis, to fit it for the next. stance to be analyzed and the posterior end of Liquid Substances. * In case the substance to CARBON. 67 be analyzed is liquid, but not readily volatile, the liquid will rise into the bulb and fill it more such, for example, as a fatty oil, it may be comnpletely than before. With less volatile placed in the combustion tube in a boat, as liquids, only a small quantity of the fluid will described. Wax, and other easily fusible mat- enter the bulb at first, but it is easy to fill the ters, may be melted and allowed to cool in the bulb completely by heating the liquid -which boat before weighing. The combustion tube first enters until part of it, is converted into had better be rather long, and provided with vapor, and again thrusting the stein into the a posterior column of oxide of copper (com=- liquid. To throw out any excess of liquid pare Piria, above). When the oxide of cop- which may remain in the steml, suddenly jerk per has been heated to redness at both ends of the bulb; then hol(l the point of the steim in a the tube, place a piece of red hot charcoal fine blowpipe jet until the glass fuses, and the near the boat, so that the substance may be bulb is closed. AVeih each of' the bulbs withl slowly distilled. Increase or diilnnish the heat its contents. Each bulb should contain fiom at the boat, and at the saiue tinme regulate the 0.3 to 0.4 grin.-enough for a single analysis. stream of oxygen in such manner that the cop- The duplicate bulb will replace the first in per reduced by the products of distillation ease of accident. may be oxidized as fast as it is formed. At After the combustion tube has been dried, the close of the combustion take care to burn cooled, connected with the weighed chloride of off all the carbon firom the boat. calcium tube, potash bulbs, etc., and proved In analyzing substances, such as some of the to be tight, take out the posterior cork of the heavier components of petroleum, which vola- combustion tube and make a slight scratch tize only at temperatures so high that their upon the stem of one of the bulbs full of subvapor would ignite as soon as formed, and stance, by means of a sharp file, or a knife of explode in the atmosphere of oxygen which hard steel, proper for scratching glass. This fills the tube, a cap or cover of asbestos fibres, file-mark should be near the point of the stein. roughly woven, attached to a stiff wire, may Place the stemn of the bulb within the combustion be placed over the boat after it has been tube, and press its point firmly against the side pushed into the tube. The asbestos cloth acts of the tube until it breaks at the file mark. The as a safety screen to prevent explosions, like moment the stem breaks, drop the bulb, point the wire gauze of Davy's lamp. (Peekhamr). downwards, into the tube, replace the cork, put Volatile Liquids. For the analysis of liquid(s a screen in front of the substance, 9 or 10 c. m. which volatilize at comparatively low temper- from the bend in the tube, heat the anterior atures, select a stick of combustion tubing 50 column of oxide of copper, and start a slow or 60 c. m. long, and bend it slightly, at a dis- current of oxygen through the tube. When tance of about 12 c. m. fiom one end, so that the copper has become hot remove the screen, the posterior end of the tube may point up- or set it backwards towards the substance, wards, and the lower edge of the extremity of accordingly as the latter is nmore or less volathe tube reach to a height of 8 or 9 c. m. tile, and finally heat the substance itself careabove the level of the sheet-iron trough in fully with a hot coal, or better, with a thick which the horizontal part of the tube reposes. rod of copper. The copper bar may be laid Pack the horizontal portion of the tube either across the ring of a lamp stand, in such manwith a mixture of oxide of copper and asbes- ner that while one enld of the bar can be tos, or with coarse oxi(le of copper, secured brought close to the combustion tube, above with asbestos plugs, and dry the tube in the the substance to be analyzed, the other end furnace with a current of air, in the usual way. can be heated to redness by means of a BunIn order to introduce the substance into the sen's lamp. By moving the lamp-stand to tube, blow a couple of light weighing bulbs, and fro, so that more or less of the hot copabout a centimetre in diameter (not too large per is brought near the bulb, the distillation of to slip readily into the combustion tube), with the substance may, in most instances, be easily capillary stems 5 or 6 c. m. long. Weigh the controlled. (Warren). empty bulbs one at a time, and place them Great care must always be exercised in heatz in paper trays bearing descriptive marks or ing the bulb in order that its contents may not numbers. Pour some of the liquid to be ana- distil too rapidly. Unless due attention be lyzed into a porcelain crucible or small dish- paid to this particular the combustion of the kept cool with ice, if' need be —warm each substance is liable to be incomplete, and gaseous bulb in succession at a lamp, and as soon as carbon comnpounds will pass off unabsorbed the glass is hot thrust its stein into the liquid through the potash bulbs. Sudden heating. of in the dish. As the glass cools, the liquid will the substance would, in many cases, occasion a rise up into the bulb and fill it more or less rush of gas strong enough to throw some of completely. In case the liquid is highly vola- the potash lye out of its bulbs, and to project tile, a portion of that which first enters the vapors backwards into the permanent drying partially cooled bulb will be converted into tubes. In order to avoid explosions, it is vapor, so that, for the moment, the rest of the essential that the empty, inclined portion of the liquid will be driven out; but as soon as the combustion tube shall never be heated to a vapor in the bulb condenses, a new portion of temperature high enough to ignite the vapor of 68 CA RBON. the substance, until after the last portions of calcium tube should be connected with a set of this vapor have been swept forward by the cur- weighed potash bulbs. By re-weighing the rent of oxygen. Throughout the analysis the latter after the substance has been dried, it is supply of oxygen gas must be sufficient to re- easy to determine whether any carbonic acidl oxidize the copper almost or quite as fast as it has been produced. (W. Stein, Joun. pr(/ct. is reduced. Chemi., 100. 55). To prevent any portion of the vapor of the NditroyeTnous Corpounds. In case the subsubstance from being lost at the posterior end stance to be analyzed contains nitrogen, choose of the tube, it is well to admit the oxygen a combustion tube about 80 c. m. long, pack it through a special tube of hard glass loosely at the anterior end with clean copper turnings packed with asbestos and kept hot during the to a depth of' 15 or 18 c. in. (Compare the conlbustion by means of a Bunsen's lamp. headinl Nitrogenous Compounds under Method This tube is placed between the combustion 1), fill in with oxide of' copper in the usual tube and the permanent drying apparatus and way and proceed with the analysis. Take is attached to the latter by means of a per- care to regulate the streams of air and oxygen forated cork; at the anterior end, which enters so that the anterior half' at least of the column the combustion tube, it is drawn out to a short, of copper turnings shall not be oxidized either blunt point, having an opening no larger than in the process of' drying or during the actual will admnit a small needle. The oxygen is thus combustion. The stream of oxygen must be made to enter the combustion tube in a rapid very slow. When the combustion of the substream, against which little or no vapor can stance is complete and it is seen that the coppass back. The hot oxygen, moreover, pre- per turnings are rapidly oxidizing, shut off the vents the condensation of' any vapor near or oxygen and let the tube cool in a slow current upon the cork. (WVarren). of air. Hygroscopic Substances. Compounds which According to Stein & Calberla (Journ. prakot. absorb water so rapidly from the air that they Chem., 104. 232) silver turnings may be used cannot be readily dried and weighed in the or- with advantage, instead of copper, for reducing dinary way may be dried in the combustion oxides of nitrogen, - as well as for retaining tube, as follows: - Pack the combustion tube chlorine, as described below. Red-hot silver with oxide of' copper, as above described, decomposes nitric oxide completely but has no lay the tube in the furnace upon a sheet- action upon carbonic acid. iron gutter so short that it does not Sulphur Com]pounds. See this heading, reach behind the column of oxide of copper, under Method 4. dry the tube and oxide in the usual way and Chlorine, Broumine and Iodine ConLpounds. attach to it the weighed chloride of calcium When chlorine, bromine or iodine compounds tube. Weigh out the air-dried substance in are burned with oxide of copper in conjunction a boat and push the boat into the combus- with oxygen gas, there is not only danger of tion tube as far as the oxide of copper. Heat some dichloride (bromide or iodide) of copper the empty, posterior part of the tube, at a dis- being carried forward into the chloride of caltance of 3 or 4 inches from the boat, and pass cium tube, as has been already explained a slow current of dry air through the tube. At (MAethod 1, p. 64), but some of the (lichloride the same time heat the column of oxide of cop- is always decomposed by the oxygen gas into per gently so that no water can be dleposited in oxide of copper and ftree chlorine. Part of the anterior part of the tube. Keep up the the chlorine thus evolved is retained in the stream of hot air as long as any water is seen chloride of calcium tube and part of it is abto be deposited in the neck of the chloride of sorbed by the potash lye. Though the error calcium tube, then allow the combustion tube from this source is usually small, it must always to cool, without checking the current of air, be carefhlly guarded against by placing a coland re-weigh the chloride of calcium tube. umn of metallic copper in the fiont part of the Subtract the weight of the water thus found tube (see Nitrogenous compounds, above) and from the weight of the substance taken, in order keeping the metal red hot throughout the comto obtain the weight of really dry material to bustion. At the close of the analysis the curbe analyzed. Replace the chloride of calcium rnt of oxygen should be arrested as soon as tube, attach the potash bulbs and the soda lime the copper begins to oxidize lest the chloride tube and proceed with the analysis. of copper which has formed upon it be again In a similar way, the water of crystallization deconmposed. (Staedeler, Anlcalen Chem. und of many substances may be determined: - To lhatrmn., 69. 334). this end suspend a sheet of copper-foil beneath According to Kraut (Zeitsch. acnalyt. Checm., the combustion tube, between the substance 1863, 2. 242) it is best to push back the coland the source of heat, place the bulb of a umn of metallic copper about 5 inches firom thermometer above the fobil and light the fuel the mouth of the tube, and to place a roll of beneath the foil; heat the tube to the temper- silver foil in fiont of the copper. If this be ture necessary to expel the water from the sub- done the stream of oxygen may be kept up as stance. In case the substance to be dried is long as may seem fit, at the close of' the operaliable to decomposition, the weighed chloride of tion, without any risk of chlorine being carried CARBON. 69 forward into the potash bulbs. The silver is may be decomposed at once. A tumultuous of use also, inasmuch as, unlike the copper, it current of oxygen would be lia le to throw prevents an) dichloride (bromide or iodide) some of the potash lye out of the bulbs, and of copper from passing into the chloride of cal- ruin the analysis. After all the reduced copper ciumn tube. The same roll of silver may be has been oxidized, the oxygen set free hiolm the used over and over again in many analyses. chlorate will of course sweep forward the carOnly after repeated use will it be necessary to bonic acid which was contained in the tube, ignite it in a stream of hydrogen. In the an- and will fill the potash bulbs and chloride of alysis of iodine compounds the column of cop- calcium and soda-liime tubes. To remove this per turnings may be dispensed with altogether oxygen, connect the bulbs and tubes with an and the silver foil employed by itself. aspirator, alter disconnecting them frolm the Kekuld places several pieces of fused chro- combustion tube, and draw through them a mate of lead in the front part of the combus- quantity of air free from moisture and cartion tube, to stop chlorine and bromine; and bonic acid, before placing them in the room of to the same end Vaelcker (Chemical Gazette, constant temperature to be weighed. 1849, 7. 245) recommends that the oxide of Instea(d of placing chlorate of potassium in copper be mixed with one-fifth its weight of the combustion tube, Laurent (Annales tie oxide of lead. Compare Method 4. C/him. et Phys., (3.) 19. 360; Gerhardt's Traite Substances which contain Fixed Inorganic Con- de Chim. Organ., Paris, 1853, 1. 35) proceeds stituents may usually be analyzed more readily by as follows:-After having dried the collbustion the process now in question than by Method 1 tube and thrown a smanll quantity of warm, (see p. 64), for the ash which remains in the coarse oxide of copper into its posterior end, boat after the completion of the combustion introduce the substance to be analyzed, mix can in most cases be weighed. In the analysis it roughly with a small quantity of warm oxide of compounds containing K, Na, Ca, Sr, or of copper, and fill the tube with oxide of copBa the amount of carbonic acid retained by the per, taken directly fi-om the crucible in which ashes in the boat can sometimes be ascertained it has been ignited, and still as hot as 200~ or by simple calculation and added to the quan- 250~. Place the tube in the combustion furtity found in the potash bulbs. In case the nace, and by means of a bent glass tube and composition of the ashes cannot be inferred rubber connector attach the closed upturned a priori, the amount of carbonic acid con- point of the tube with a U-tube, one armin of tained in them had better be determined by which is filled with chloride of calcium, and the fusing the residue with borax glass (see under other with firagments of caustic potash. That Carbonic Acid). arm of the U-tube which is farthest firom the combustion tube contains the potash, and is Method 3. Combustion with Oxide of Cop- provided with a cork pierced with two holes. per, in conjunction with Oxygenz gas obtained by One of the holes carries a tube bent at an heating Chlorate or Perchlorate of Potassium, angle somewhat less than a right anjle, and at or within the comibustion tube. the other carrlies a straight, upri(ht tube, The operation of filling the combustion tube drawn to a fine point and closed at its upper is similar to that described under Method 1, extremity. The outer end of the bent tube with the exception that the column of oxide of is attached, by means of a perforated cork, to copper at the posterior end of the tube is made the mouth of' an ignition tube of' hard glass, about 5 c. m. long, instead of' 3 or 4, and is 30 or 40 c. m. long, and charged with 3 or 4 mixed, by shaking, with 3 or 4 grins. of fused grammes of fused chlorate of potassium. The chlorate of potassium, in the forml of coarse ignition tube rests upon a wire grate in such powder. The fused chlorate should be still manner that the chlorate can be heated by warm when thrown into the tube. A layer of placing bits of hot charcoal around the tube. oxide of' copper about 2 c. m. thick should be Detach the rubber connector from the posterior placed above the chlorate mixture to sepa- point of the combustion tube, and proceed to rate it from that which contains the substance heat the latter in the usual way. - After to be analyzed. - After the anterior col- the combustion in the tube has been pushed to um1n of oxide of copper and the mixture of such an extent that little or no more carbonic oxide of copper and substance to be analyzed acid goes forward, suck a sumall quantity of air have been heated, as in Method 1, the mixture from the open end of the soda-limlle tube, in of chlorate of potassium and oxide of copper order to establish a partial vacuuml within the is slowly heated, so that the combustion tube combustion tube, and crush the end of the upmay be filled with oxygen gas. Any particles turned point of the combustion tube with a of carbon which the oxide of copper has failed pair of pincers. Slip on the rubber tube which to consume, will now be completely oxidized, connects the apparatus with the U-tube and the as well as the metallic copper which has been tube charged with chlorate of potassium, and reduced in the previous steps of the analysis. place live coals about the latter so that oxygen The mixture of chlorate of potassium and oxi(le may be slowly evolved finom it. The tube must of copper must be heated with extreme care in be heated very slowly, and care must be taken order that no great quantity of the chlorate that the upper part of' the tube is kept hot 70 CARBON. enough to prevent the solidification there of chlorine, bromine, iodine, or fixed inorganic the melted chlorate. W'hen the oxygen ceases materials. to be absorbed by the reduced copper, and be- In some respects the process resemlbles gins to pass rapilly throuoh the potash bulbs, Miethod 2, but differs from it inasmu(ch as a break off the point of the upright tube at- wrouhllt iron pipe is employed as the comll)olstache(l to the U-tube, and draw air througllh tion tunle, il pllace of the (lass tube alove (Iethe latter and the rest of the apparatus until scribed, and that atmospheric air is used as anI the whole of the oxygen has been expelled. oxidizino agent instead of oxv-en gas. Since Since chlorate of potassiuLlim decomposes with the iron tube is well nio(h inidestructible, the a certain degree of violence, Bunsen recoin- apparatus, once mounted, becomes a, permanent mends that it be replaced by perchlorate of fixture, and may be used for an almost indefipotassium prepared, in the ordinary way, by nite nlumber of' analyses. heating the chlorate. A few grainmes of the Select a piece of wrought iron gas pipe, -fused and still hot perchlorate are thrown about 11i c. m. long and 20 or.22 im. ml. in into the posterior end' of the colmbustion tube, dliameter. Provide a comnbustion furnace about a loose plug of recently ignited asbestos is, 75 c. in. long, so that each end of the tube pushed dlown to keep the potassiumn salt in shall, project 20 c. m. beyond the fire. lieat place, and the rest of the tube then filled the tube to rednless and pass in a current of in the ordinary way. Il case the substance steam to oxidize the inlner surface of the tube. to be analyzed is lisxed writh oxide of colper Fill the midldle part of the tube with a long by means of a twisted wire, as explained on columnn of coarse, hard oxide of copper, and p. 61, perchlorate of potassium should always to keep the oxide of copper in place, plug it be used instead of the chlorate. with spiral rolls of superficially oxidized copNon-volalile Li/lid Substaioces. Weig-h the per foil. Provide two boats of stout sheet substance (a fatty oil for example) in a small iron, oiie 20 the other 30 c. m. longl, of such glass tube, kept upright by a wire support. size that they can be readily pushed into or place a qualntity of' oide of copper and chlo- dlrawn out filmn the combustion tube' for this rate of potassium in the end of the rather lolng purpose attach a short iron wire to one elld of combustion tube, as above described, drop in each of the boats. T'e long er boat belong)s the loaded weighing tube and cause the oil to at the posterior end of the coinbustion tube run out into the combustion tube and spread the sholter at the front. If thle substance to about upon the surface of the glass, excepting be burned contains nothing but carbon, hydrothe anterior third or fourth of the tube and gen and oxyg-en, the anterior boat is to be the upper side of the tube where the open filled with coarse oxide of copper,-or the?hannel is to be left. Fill the tube with oxi(le boat nlay be left out altocether in case the of copper which has been cooled in a tight substance to be analyzed is readily conibustiflask, as described on p. 61, and take care that ble. If. on the contrary, the substance to be the weighing tube is filled with the oxide. analyzed is nitrogenous, fill the anterior boat Place the tube in hot sand, so that the oil nmay with copper tiurinings (compare p. 64-l); if it become more fluid and so be completely ab- contalin sulphur, chlorine, iodine, or bronlille, sorbed by the oxide of copper, and proceed fill the boat either with red lead or awitli chrowith the analysis as above described. _- Solid mate of lead. fats or waxes may be fused in a smiall weighed Solids. In case the substance to be burned bqat of glass, madle from a tube cdivided lengtlh- is a solid consisting only of' carbon. hydrog,-en wise, and then cooled andc weighed, The boat and oxygen, both the boats are filled with and contents may then be dropped ilto a corn- oxide of copper and placed in the combustion bustion tube, into the end of' lwhich oxide of tube, which is then heated as far as the fuircopper and chlorate of potassiunl have been mlace reaches during 10 or 15 minutes, while a previously thrown, and heat appliedl so that slow streaml of air is forced thllroull the tube. the substance may be spread about the tube Allow the posterior portion of the tube to cool and subsequently absorbed by the oxide of soiiiewlhat, tlhen take hold of' the tube with a copper as just described. pair of roughclened pincers (oas-fitters' pliers), remove the stopper, draw out the boat and Jlethod 4. Codlustion with Oxide qofcopper cork it up in a special iron tube, kept for the in conjulGcotioz wCith AtlnoIpheric Air. (Method purpose, until it hlas become well nigh cold. of Cloez). Meanwhile attach the wveighed chloride of calThis method of analyzing organic compounds cium tubes, etc., to tlle anteriorl end of the is characterized by the simplicity and cheap- tube, which has hitherto remained open. ness of the apparatus required, as well as by As soon as the oxide of copper is cold its very general applicability. It may be emr- enoudli, place the boat on a sheet of thin colpployedl not only for the analysis of comlpooun(Is per foil, andi with a polished iron hook tralsfthr of carbon, hydrogen anl oxygen, Twhether solid a poltion of the oxide to a small, shallow recor liquid, xvolatile or non-volatile, but foir the t.,ngular box or shovel of brass, open at one determinatition of' crblon anid hmyd'rogen in iull- et(. Quickly scatter the substance to be stances contaminated with nitrogen, sulphur, -analyzed over the oxide of copper left in the CARBON. 71 boat, cover it with the oxide in the shovel, the latter on a piece of platinum foil turned push back the boat into the combustion tube, up at the edges and provided with a wire for replace the stopper and pass a slow current of withdrawing it from the tube, push the boat air through the apparatus. The combustion up to the permanenat column of oxide of copis conducted in the usual way in so far that per in the midd(lle of the tube, and proceed the anterior end of the boat is first heated, with the combustion in the ordinary way. Afwhile the oxide of copper in the middle and ter the products of the dry distillation of the front part of the tube is kept red hot. By substance have been consumed, the residual noting the rate at which the air bubbles pass carbon is burnt at the expense of the oxygen through the potash lye in the permanent set in the stream of air. A somewhat lonler time of purifying tubes behind the furnace, and the is required in this case than when the combusweighed potash bulbs in front, it is easy to tion is finished in oxygen, but the results obfollow the process of the combustion, and de- tained are said to be equally accurate. terminewhen the operation is finished. - In- To dry and purify the air required for this4 stead of transferring the boat full of oxide of process, Clodz employs a set of' permanent copper to a special cooling tube, it may be left tubes and flasks, consisting: 1st, of a small botto cool in the combustion tube if the operator tle containing dilute potash lye,-the tube prefer. which brings air to this flask barelyc.dips beAfter the combustion is finished, and the neath the surface of the liquid; 2d, of' a tall, weighed absorption tubes have been removed drying cylinder, filied with bits of pumice stone to the room of constant temnperature, force a soaked in sulphuiic acid; 3d, of a long horistrong current of air through the tube in order zontal tube, with turned-up ends, filled with to reoxidize the reduced copper, and proceed porous chloride of calcium; and 4th, of' a to the next analysis. similar tube filled with firagments of caustic Liquids. Non-volatile liquids are weighed in potash. a tube drawn out to a fine point, and are then Instead of a weighed chloride of calcium transferred to the oxide of copper in the boat; tube to absorb the water produced by the the weight of the substance taken is determ- combustion, he employs a U-tube filled with ined by. weighing the empty tube. Volatile fragments of pumice stone moistened with oil liquids may be weighed in a tube provided of vitriol. (Clodz, Annlales Clhimie et Phys., with a glass stopper at one end, and drawn out (3.) 68. 394.) to a point at the other. This tube is laid on the oxide of copper in the boat, the stopper is MlIethod 5. Combustion in Atmosipheric A ir, removed, the boat immediately pushed into the in conjunction toith Oxide of Coppler. (Method combustion tube, and a slow stream of air of' Fresenius). forced through the tube. In this case the This method is applied to the estimation of oxide of copper in the posterior boat is not the chemically combined carbon in cast or heated until the stream of cold air has ceased wrought irons, particularly in those kinds of to carry forward vapors of the substance into iron which contain much graphite and but the column of hot oxide at the middle of the little coimbined carbon. tube. Mle/hod. Reduce a quantity of the iron to Nitrogenous Substcances. In analyzing nitrog- fine powder. Weigh out froml 1 to 1.5 grins. enous substances, a copper boat filled with of the powder, and place it in a flask of about copper turnings (see Nitrogenous substances 150 c. c. capacity. Fit a two-holed caoutchouc under Methods 1 and 2) is placed in the fore stopper to the flask, and to one of the holes part of the tube, and only a very slow stream fit a glass tube rather more than twice as long of air is kept up during the first part of the as the' flask is high. Bend this tube twice combustion. The current of air may be made near the middle into the form of an S, in such more rapid towards the close of the analysis, manner that the bent portion may be wholly though the anterior portion of the layer of outside the cork, while enough of the tube is metallic copper should remain unoxidized to left straight at either end to reach almost to the last. the bottom of the flask; blow a small bulb at Sulphur, Chlorine, Bromine or Iodine. In the middle of the bent portion, i. e., at the the analysis of substances containing sulphur, centre of the S. After tlie S-tube has been chlorine, bromine or iodine, the anterior boat fitted to the stopper, pour a few drops of quickis filled with dry red lead or chromate of lead, silver into the lower bend of the S. To the and the substance is mixed with fused and pow- other hole in the stopper fit a delivery tube. dered chromate of lead in the posterior boat. This delivery tube should pass straight upThe anterior boat should be heated only to wards through a distance about as great as the incipient redness, in order that its contents height of the flask, and then bend at a right may not fuse. angle to meet a horizontal combustion tube. Ash Determinations. In case the proportion Betore fixing this delivery tube to the stopper, of ashes in the substance analyzed is to be de- slip a short piece of rather wide glass tube termined as well as the carbon and hydrogen, over its upright part, and by means of a perweigl the substance in a porcelain boat,'place forated cork fasten the lower end of this 72 CARBON. outer sleeve tightly to the delivery tube. Dur- practically insignificant, though sufficient to ing the experiment, this sleeve is kept full of impart an odor to the liquid. water to cool the mixture of air and hydrogen The iron in the flask of course dissolves more passing forward from the flask. or less rapidly, according to the kind of metal, The combustion tube may be about 30 c. m. the fineness of the powder and the degree of liong, Half its length-the end next the flask,- heat, but as a rule the experiment requires 1 or is filled with loosely packed asbestos and the 2 hours for its completion. - In operating other half with coarse oxide of copper, the upon samples of iron containing but little latter being kept in place by a final plug of as- graphite it may be well to throw into the flask bestos. To the end of the combustion tube which a small quantity of platinum sponge to accelis farthest from the flask attach a large un- crate the solution. - The process is inapweighed U chloride of calcium tube, to the lat- plicable for the analysis of certain kinds of ter attach a small, weighed soda-lime tube, and iron which deposit a portion of the combined beyond the soda-lime place another unweighed carbon in the solid form (together with the U-tube, filled half with soda-lime and half with graphite) when treated with dilute sulphuric chloride of calcium, to protect the weighed acid. (Buchner, Journ. prakt. Chem., 72. 364). tube. To this last U-tube attach an aspirator. It is easy to determine whether carbon has Ignite the contents of the combustion tube been thus deposited in any given case by exin a current of air free from carbonic acid; amining the residual grphite. To this end noconnect the combustion tube with the delivery tice, in determining the Graphite, whether any tube of the flask, test the tightness of the coloration is imparted to the liquids, - boiling apparatus, and beat the oxide of copper half water, potash lye, alcohol, and ether, - with of the combustion. tube to low redness. which the graphite is washed. Observe also Place a small thistle tube in the top of the S- whether the alcohol or ether, with which the tube of the flask, fill the thistle tube with dli- graphite has been washed, after removal of the lute sulphuric acid, made by mixing 1 part of potash lye by water, leave any residue of orstrong acid with 5 parts of water, and by means ganic matter when evaporated. (Fresenins, of the aspirator draw over into the flask, past Zeitsch. analyt. Chem., 1865, 4. 73). The prothe mercury, a quantity of the acid sufficient cess yields accurate results. (Compare Tosh, to dissolve the iron. Remove the thistle tube, Chem. NTews, 1867, 16. 67). replace it with an unweighed soda-lime tube, attach the latter to the S-tube with a caout- Methed 6. Combustion with Oxygen gas. chouc connector and, by means of the aspirator, (W~arren's method). draw a slow current of air through the appa- Specially adapted for the analysis of volatile ratus while the iron is dissolving. - Heat liquids, and of gases. the flask carefully in a water bath, or upon a Bend a combustion tube in the manner demetallic plate, so that the iron may dissolve scribed under Method 2, in the paragraph rewith tolerable rapidity. latinf, to volatile liquids; pack the horizontal The mixture of air, hydrogen and carbu- part of the tube with small, fibrous pieces of retted hydrogen burns to water and carbonic asbestos, or other inert substance, so loosely acid, at the edge of the asbestos in the comrn- that gases may pass freely through all parts of bustion tube, so completely that but little of the mass, and at the samle time so closely that the oxide of copper in the combustion tube is no mixture of oxygen and hydrogen or other ever reduced. In case any of the oxide of inflammable gas can explode when heated in its copper happens to be reduced for a moment midst. In packing the tube, the asbestos should the metal is immediately reoxidized by the ex- be added little by little and each new portion cess of air. The column of asbestos prevents pressedgently against the preceding by means of the possibility of the flame's passing back into a stiff' wire. Little attention need be paid to the the flask. The carbonic acid formed during arrangement of the asbestos in the middle of the the combustion is absorbed in the weighed tube, since that portion of the column will soda-lime and its amount determined by re- come right of itself if the material is properly weighing the tube at the close of the experi- packed against the glass. A good way is to ment. hold the tube in the left hand and turn it conAs soon as the evolution of hydrogen ceases, tinually, while the wire in the other hand is beat the column of' asbestos in the combustion made to pass around against the sides of the tube in order to oxidize any traces of hydro- tube, gently tapping the asbestos and comcarbons which may have condensed on the as- pressing it so that only very small open spaces bestos, and afterwards allow the apparatus to can be seen in the finished column. It is best cool in a slow current of air. Weigh the soda- to make the horizontal tpart of the tube long lime tube and from the weight of carbonic enough to hold a column of asbestos 10 or 12 acid thus found calculate that of' the carbon inches long, and to place a short column (2 or 3 which has been evolved from the iron as a gas- inches) of coarse oxide of copper in front of eous compound. The traces of hlydrocarbons the asbestos as a safeguard against accidents. retained by the iron solution in the flask are The substance to be analyzed is introduced CARBON. 73 at the posterior part of the tube in the manner that the oxygen may be absorbed, and collect described in the paragraph just cited, and the and measure the nitrogen in a graduated cylanalysis is conducted as there directed. Spe- inder. cial care must, however, be exercised in regulat- The amounts of C1, Br and C are determined ing the stream of oxygen so that an excess of by weighing the several absorption tubes before this gas may always be present in the coinbus- and after the experiment. tion tube. To this end, the permanent drying If the substance contains sulphur, replace apparatus should contain a set of potash bulbs the solution of nitrate of lead with a concenof the same size as the weighed potash bulbs trated solution of bichromate of potassium to at the front of the tube, so that the number of absorb the sulphurous acid. In order to get bubbles, that is to say volumes, of oxygen en- rid of a small quantity of sulphuric acid which tering the tube may be readily compared with is formed during the combustion of the mixed the bubbles of carbonic acid which pass out. hydrogen and sulphur compound, place some About 2 vols. of oxygen should be made to chloride of calcium and a little sulphite of calpass through the posterior potash bulbs for cium near the hydrogen flame. The moist every bubble of mixed carbonic acid and oxy- sulphuric acid is absorbed by the sulphite of gen which appears at the anterior bulbs. Or, calcium as fast as it is formed, and at the same better, the posterior set of bulbs may be made time a quantity of sulphurous acid, equivalent of such size that each of their bubbles shall be to that of the sulphuric acid, is set free from twice as large as those of the anterior bulbs. the sulphite to be absorbed by the chromate of In case the supply of oxygen were at any time potassium in due course. - If the subdecidedly deficient the fact would be indicated stance contains iodine, the latter is allowed to by the reduction of some of the oxide of cop- deposit itself near the hydrogen flame at first per at the front of' the tube. For a descrip- and is subsequently sublimed into a clean glass tion and figure of an attachment for saving the tube, of known weight, and weighed as such. excess of oxygen, and at the same time pre- In case any portion of the substance remains venting the possibility of losing an analysis unvolatilized after having been thoroughly through the escape of unconsumned carbona- heated in the stream of hydrogen, the residue ceous gases see Warren's original memoir, as is weighed directly and estimated either as carcited below. bon or ash, as the case may be. For the deIn spite of the fact that by far the larger tails of this interesting process, see A. Mitpart of the substance is consulnmed in a very scherlich's memoir in Zeitsch.,analyt. Chem., small portion of the column of asbestos, it has 1867. 6. pp. 151-166, and 141. not been found advisable to make the combustion tube any shorter than has been recom- Method 8. Combustion with Chromate of mended above. With a short tube it is far Lead. more difficult to control the distillation of the This method was formerly much employed substance and to regulate the supply of oxy- as a substitute for Method 1, in analyzing difgen. The method of preventing any of the ficultly combustible substances, such as resins, substance from escaping backwards from the coal, fats, etc.; it is, however, less convenient combustion tube has been already described. than Methods 2, 4 and 6. See Method 2, paragraph on, Volatile liquids. Anderson (Annalen Chem. und Pharmn., 122. (Warren, Amer. Journ, Sci., 1864, 38. 387). 300) has observed but cannot explain the fact that in analyzing hydrocarbons with pure chroMethod 7. Combustion with Oxygen after vola- mate of lead, the amount of hydrogen found tilization in a stream of Hydrogen. (A. Mit- is often considerably larger than it should be. scherlich's method). The details of the process, which may be Applications. Simultaneous estimation of used for analyzing solids and liquids, whether C, C1, Br, I, S, and N in solid-, liquid, or gas- volatile or non-volatile, are similar to those of eous, substances without need of any combus- Method 1, with the exception that fused, powtion furnace. dered chromate of lead is substituted for the Method. Heat the substance to be analyzed oxide of copper. The combustion tube need in a stream of hydrogen, and burn the hydro- not be so large as in Method 1, since chromate gen, thus charged with the vapor or products of lead contains far more available oxygen of distillation of the substance, in a stream of than an equal volume of oxide of copper. (See oxygen. If the substance contains no sulphur, Chromate of Lead). The chromate is simply pass the products of' the combustion over a heated in a porcelain or platinum dish, over a sheet of strong sulphuric acid to remove the lamp, until it begins to turn brown, and then water, then through a strong solution of nitrate allowed to cool at 100~, or to a lower tenperof lead to absorb the chlorhydric acid, next ature, before it is transferred to the combusthrough a tube filled with oxide of mercury to tion tube or mixing mortar. Since chromate absorb bromine, and then through potash lye of lead is as hygroscopic as oxide of copper, to absorb the carbonic acid. Finally pass the the tube must finally be dried with an exhaustresidual nitrogen and the excess of oxygen ing syringe, as described under Method 1. through a tube containing phosphorus, in order The combustion is conducted in the same 74 CARBON. way as with oxide of copper, but towards the Method 9. Use of Bichromate of Pofassium. close that part of the tube which contains the A. Bichromate of Potassium with Chromnate substance must be heated intensely, in order to of Lead. In analyzing some very difficult ly fuse the chromate of lead so that no particles combustible substances, such as graphite, for of carbon may escape combustion. This power example, it has been found advantageous to of fusing at a moderate heat is one of the chief mix the chromate of' lead with about oue-tenth advantages of the chromate as compared with its weiglht of fused and powdered biclinromate oxide of copper. Care must be taken, how- of potassiumn. This mixture melts readily and ever, not to fuse the chromate at the anterior gives off towards the close of the process a litpart of the tube, nor to heat it so hot that tie more oxygen than would be evolved from it shall lose its porosity, lest it become power- mere chromate of lead. (Liebig; Meayer, less to act upon gaseous products which have Ainnal. Chem. und Pharn., 95. 204). The been only incompletely oxidized at the other mixture of chromate of lead and bichromate of end of thle tube. It is well, for that matter, to potassium is well fitted also for the analysis of fill the anterior part of the tube with coarse organic compounds containing potassium, sooxide of copper instead of chromnate of lead, dium, barium, calcium or strontium. No trace or with copper turnings which have been su- of carbonic acid is retained by either of these perficially oxidized by heating them in the air. metals when their compounds are ignited in }For the use of bichronmate of potassium in presence of the mnixed chromates. conjunction with cbromate of lead, see below, B. Biclhomate of Potassium with Oxide of Method 9. Copper. It has been suggested by Rochleder Sulphur Compounds may be burned with that a fused mixture of oxide of copper and chromate of lead in a tube 60 or 80 c. mn. long, bichronate of potassium might be used instead if care be taken that 10 or 20 c. in. of the fore of chromate of lead for burning (lifficultly c(oinpart of the column are never heated above low bustible substances, and, considered merely as redness. (Carius, Annalen Chem. und Pharm., an oxidizing agent, the mixture is said to yield 116. 28). For the use of chromate of lead in excellent results. But the fiusedl mass is so conjunction with oxide of copper and air, see hard to pulverize that it is practically less conabove, Mlethod 4. venient than chromate of lead. Chlorine and Iodine Compounds may be Schulze has employedl these ingredients in a analyzed with chromiate of lead without the somewhat dliierent way for deterlmining the risk of errors such as are liable to occur when proportion of' hunmus in soils. HEis process is oxide of' copper is used. The chlorine or as follows: -Rub 10 grins. of the finely powiodine is converted into chloride or iodide of dered and sifted soil together with 20 grins. of lead and so retainled in the combustion tube. a mixture of equal parts of oxide of' copper Some Bro;mine Compounds, however, are not and bichrolnate of' potassium. Place the miixreadily analyzed in this way, since the metallic ture in the closed end of a combustion tube, bromlile formned dtring tile combustion is liable put a layer of oxide of copper in front of the to fuse and enclose sonme particles of carbon so mixture, a layer of finely divided imetallic completely that they cannot be burned, To copper in front of the oxide of copper, and avoid this difficulty Gorup-Besanez, Zeitsch. leave a space of several inches empty at analyt. Chem., 1862, 1. 439) recommends the the front of' the tube. Connect the anterior following method:- Clhoose a combustion tube end of the tube with the collecting bottle of with a rather long, upturned point, place in Schulze's apparatus fbr estimating carbonic the tube a three-inch layer of oxide of copper, acid (see Carbonic Acid, estimation of by nmeasthen a plug of asbestos, then a porcelain boat uring the gas), turn down the water delivery containing the substance to be analyzed in tube of the connecting bottle and proceed to fine powder, mixed with about an equal weight heat the mixture in the combustion tube preof' dry oxide of lead; then another asbestos cisely as in an ordinary combustion; i. e., from plug. a column of granular oxide of copper, the front backwards, taking care not to heat and finally chromate of lead or copper turn- the tube so strongly as to distort it. Mleasure ings. First heat to redness the anterior and the water expelled froml the collecting jar, as posterior portions of the tube, and then warm directed in the paragraph above referred to, in the tube at the boat very carefully and grad- order to determine the volume of' carbonic ually. The combustible portions of the sub- acid. - The metallic copper at the front of stance will distil over in the form of vapor and of the tube will retain any oxygen which may be burnt by the hot oxide of copper, and noth- be given off from the bichromate. A special ing but bromide and oxide of lead will be left experiment must be made, as directed under in the boat. Complete the colnbustion in a Carbonic Acid, inorder to ascertain how much stream of oxygen, taking care that no more of of the carbonic acid obtained by the combusthe gas is passed than is necessary and that tion is derived from carbonate of calcium in thbe contents of the boat are not too strongly the soil. The difference between the two deheated. To prevent bromide of copper from terminations will give the amount of carbonic sublimiiing into the chloride of calcium tube, acid derived from the carbon burnt. In case see Method 2, p. 68. the carbonic acid is mixed with nitrogen or CARBON. 75 other foreign gas, it may be passed into baryta tube attach a Will & Varrentrap's nitrogen water and precipitated as Carbonate of Barium. bulb filled with concentrated sulphuric acid (Schulze, Zeitsch. analyt. Chem, 1863, 2. and set in a basin of cold water; to the nitro298). gen bulb attach a set of Liebig's potash bulbs, Another method of employing the two in- and to the latter attach a small tube filled with gredients, is to mix them in.the combustion fragments of solid hydrate of potassium. Since tube, as has been proposed by Gintl (Zeitsch. the purpose of the sulphuric acid is merely to analyt. Chem., 1868, 7. 302). - Into an purify the carbonic acid, it need not be ordinary combustion tube, drawn up to a point weighed, but both the potash bulbs and tube and closed at one end, pour a layer of about must be weighed before and after each expertwo inches of coarse oxide of copper, then a iment. - Prepare a quantity of the oxilayer of several inches of fused and powdered dizing solution by placing 100 grammes of bibichromate of potassium, then the organic sub- chromate of potassium and 125 grins. of oil of stance to be analyzed and then a layer of sev- vitriol in a litre flask and filling the flask with eral inches of oxide of copper. Both the pow- water to the mark. Pour about 150 c. c. of dered bichromate and the oxide of copper are this solution through the bulb-tube into the kept free from moisture in tightly closed tubes flask, close the tube with the plug, and heat or flasks, as explained on p. 61. By means the contents of the flask upon a water bath. of a twisted wire (Compare p. 61), mix the The carbonic acid set free is dried and othersubstance, the oxide and the bichromate inti- wise purified by the sulphuric acid in the nitromnately, then fill the anterior part of the tube gen bulbs, and is absorbed by the potash in the with oxide of copper and proceed with the weighed apparatus beyond. In the course of combustion in the usual way. (See Method 1). 20 minutes bubbles of carbonic acid cease to Since some free oxygen resulting fioom the par- pass through the sulphuric acid, and a quantity tial deconlposition of the bichromate is apt to of the potash lye rises into the large bulb of escape from the tube, care must be taken at the Liebig apparatus. When this occurs, rethe close of the combustion to draw air through move the plug fioml the top of the bulb-tube the apparatus until the last trace of oxygen at the flask, attach a soda-lime tube to the gas has been displaced fromn the potash bulbs. bulb-tube to purify the air, and by means of The process yields excellent results, the com- an aspirator draw air througch the flask until bustion is easily completed at a comparatively all the carbonic acid has been swept forward. low temperature and the materials employed The increase in weight of the potash bulbs and are much cheaper than chromate of lead. tube gives the amount of carbonic acid which C. Bichromate of Potassium with dilute Sul- has been evolved fiom the substance. - It phuric Acid. (Method of analysis by gentle or is important to keep the sulphuric acid in the "Limited" oxidation). Compare Brunner (be- nitrogen bulbs cool, lest it act upon some of low, under Method 10). the aldelyde or other volatile products of the Many organic substances, such, for example, decomposition, which pass forward with the as the fatty acids, undergo no change when carbonic acid, and so generate sulphurous acid. treated with a dilute solution of bichromate of Since the province of the sulp)huric acid is to potassium mixed with weak sulphuric acid; absorb aldelyde as well as water, chloride of while other substances, such as compounds of calcium cannot be used in its place. lactic acid and diethoxalic acid are readily de- Another form of apparatus employed by composed by the mixture, with evolution of a Chapman & Smith in certain cases fobr estidefinite quantity of carbonic acid. Hence it mating the carbonic acid by loss, is figured on is possible to analyze certain mixtures of or- p. 180 of their memoir. ganic compounds, — after the mode of decomposition of tlhe easily oxidizable constituents Method 10. Combustion with Chromio Acid. has once been deterumined, - by heating the This process is used for estimating carbon in mixture with the acidulated solution of bichro- cast-iron (see above, Principle 1, D), and for mate and collecting and weighing the carbonic determining carbon in soils, vegetables and acid which is formed. other substances whose ashes would be likely For decomposing one class of substances, to interfere with the ordinary methods of analsuch as the lactates, Chapman & AM. Smith ysis. Like Method 7 it differs essentially from (Journal Lon.don Chem. Soc., 1867, 20. 173) Methods 1 to 6 and 8, inasmuch as it is appliemploy the following process:-Place a weighed cable to the determination of carbon without quantity of the substance to be analyzed in a regard to the hydrogen which usually accoInwidelmouthed flask, and fit to the flask a caout- panics this element. chouc stopper with two perforations. In one Provide a two-necked flask of about 150 c. c. hole of the stopper place a short delivery tube capacity. To one neck of' the flask fit a perbent at a right angle, and in the other hole a forated cork carrying a tube bent at a right long trbe reaching almost to the bottom of the angle, and to the other opening attach a wide flask, provided with.a bulb above the stopper, tube provided with a bulb of 70 or 80 c. c. caand closed at the upper end with a bit of caout- pacity. The purpose of this bulb is to conclhouc tubing and glass plug. To the delivery dense aqueous vapor generated in the flask; it 76 CARBON. must be supported in a vertical position above In using this method for determining carbon the flask. The inner limb of the right-angled in an organic substance, about 16.6 grins. of tube above mentioned must be long enough to chromic acid and 25 c. c. of concentrated sulreach to the bottom of the flask; the other phuric acid should be taken for every gramme limb extends a few inches outwards from the of the substance. About 2 vols. of water cork and is plugged at the end with a bit of should be placed in the flask for every 3 or 4 glass rod fitted to a short piece of rubber tub- vols. of strong sulphuric acid used. If the oring. Set the flask in a basket of wire gauze ganic substance contains chlorine, bromine or on a ring of a lamp-stand. Connect the ver- iodine, a tube filled with pulverulent iron, coptical bulb-tube with a permanent drying appa- per or silver must be placed between the vertiratus consisting of a cylinder of about one- cal bulb-tube and the permanent drying cylinquarter litre capacity, filled with pumice stone, der to absorb the foreign gas. (Ullgren, Annal. which has been soaked in strong sulphuric Chem. und Pharm., 124. 59). - Ullgren acid and afterwards heated to expel any traces prefers chromic acid to the bichromate of' poof chlorhydric or fluorhydric acid which may tassium recommended by the brothers Rogers, have been contained in the stone, and a U- and by Brunner (Pogg. Ann., 95. 379), since tube about 60 c. m. long full of chloride of it is possible in this way to avoid the fbrmation calcium. To absorb the carbonic acid, attach of an annoying precipitate of anhydrous chrome to the chloride of calcium tube a small, weighed alum which interferes with the reaction, when U-tube, full of soda-lime or potash-pumice, with bichromate of potassium is employed. The a short layer of chloride of calcium at the outer chrome alum thus thrown down as a green, end. slimy powder, almost insoluble in water, acids, In case the substance to be analyzed consists or alkalies, not only delays the oxidation, but of the r6sidue from 2 grins. of cast iron, as tends to conceal its completion. - According explained on p. 58, the details of the process to Brunner, it is possible, by his process, to eswill be as follows: - Remove from the flask timate the ordinary modification of carbon in the cork which carries the right-angled tube, presence of graphite, by oxidizing first with a and draw up the inner limb of this tube mixture of bichromate of' potassium and dilute through the cork so that it shall not reach far sulphuric acid and afterwards using strong acid; into the flask. By means of a wash bottle with but the separation -did not succeed in Ullfine jet, wash the carbonaceous matter into the gren's hands. For the application of this flask, taking care to use as little water as pos- process to organic analysis, compare W. sible. If the quantity of liquid in the flask nop, Chem. Centralblatt, 1861, p. 17. does not exceed 25 c. c. add to it 40 c. c. of concentrated sulphuric acid, or a proportion- 3Method 11. Combustion with a mixture of ally larger quantity of acid if the volume of Chromate of Lead and Chlorate of Potaswater is larger, and allow the mixture to cool. silm. Attach the flask to the system of drying and Applications. Estimation of carbon in castabsorption tubes, throw into it about 8 grammes iron. of solid chromic acid, free from potassium, and AMethod. Close a combustion tube of hard glass immediately replace the cork. - Heat the at one end and place at the closed end a two-inch flask gradually until the evolution of gas be- layer of a mixture of equal parts of chromate of comes so violent that the mixture threatens to lead and chlorate of potassium. Mix about 3 boil over, and maintain the temperature at grms. of the finely powdered iron with 50 this point as long as there is a lively evolution grms. of a mixture of 40 parts chromate of of gas. When the current of gas slackens, lead and 6 parts of fused chlorate of potassium, heat the flask more strongly until white fumes and place the mixture in the combustion tube. appear in'the vertical bulb-tube, and maintain Finally, place a layer of chromate of lead in the mixture at this temperature until the evo- front of the mixture, and connect the tube with lution of gas becomes very weak. Attach an a chloride of calcium tube and a weighed sodaaspirator to the weighed soda-lime tube and lime tube or set of potash bulbs. Heat the open its cock slightly; push down the right-an- contents of the combustion tube carefully, begled tube in the flask until it dips beneath the ginning at the anterior end. When the mixsurface of the liquid, remove the plug from ture of iron and the oxidizing agents is heated the outer limb of the right-angled tube, and to dull redness the metal burns with incandesattach to the latter a tube filled with fragments cence, and the carbon contained in it is conof caustic potash. Then open the cock of the verted into carbonic acid. At the close of the aspirator somewhat wider, so that bubbles of operation the free oxygen evolved from the air may pass through the liquid in the flask at mixture of chlorate and chromate at the end the rate of about 2 a second. When 5 or 6 of the tube sweeps forward the carbonic acid litres of water have flowed from the aspirator and, if need be, completes the oxidation of the the whole of the carbonic acid will have been iron. - The process usually yields good reswept out of the apparatus and absorbed in suits, though the percentage of carbon found is the weighed soda-iinme tube. Allow the latter sometimes rather lower than the truth. The to cool before weighinig it. addition of chlorate of potassium is essential to CARBON. 77 success in determining carbon in cast-iron; with chlorate is scarcely at all hygroscopic, the mixchromate of lead alone the amount of carbon ing and transfer of the substance may be made obtained from the cast-iron is always too small. at the ordinary temperature without special (Regnault, Annal. Chem. und Pharm., 30. precautions. 352; Bromeis, Ibid., 43. 241; Tosh, Chem. Hang the combustion tube, or support it News, 1867, 16. 67). Take care to remove upon wires, in a horizontal position, attach the the oxygen from the absorption tube befb e weighed absorption apparatus (a large chloweighing. Or, instead of that, the soda-lime ride of calcium tube and a couple of soda-lime tube may be filled with oxygen in the first tubes will be best) and proceed to heat the mixplace, and always be weighed full of oxygen. ture of chlorate and substance with a singlesmall spirit lamp or Bunsen's burner. The tube is.Method 12. Combustion with Chlorate of Po- first heated at the asbestos plug and then backtassium. wards step by step, until each portion of the The original process of Gay-Lussac & The- chlorate has been melted and made to react nard was as follows: - An intimate mixture upon the organic matter. It often happens of known weights of chlorate of potassium and that the reaction is attended with evolution of of the,substance to be analyzed was made light or even deflagration, particularly when into small pellets and the latter were thrown, the substance contains a large proportion of one by one, with proper precautions, into a carbon, but the deflagration, according to vertical tube kept at a red heat. The carbon- l\kne, does no harm even when potash bulbs ic acid, oxygen and nitrogen (if present) were are used to collect the carbonic acid. At the conducted through a lateral delivery tube to a close of the combustion, the last traces of carmercury trough and there collected in a grad- bonic acid are swept forward out of the tube uated cylinder. After the total volume of gas by the oxygen set free from the pure chlorate had been measured, the amount of carbonic of potassium at the end of the tube. Care acid was determined by absorption with caustic must be taken that the absorption apparatus potash and that of the oxygen by exploding is either weighed full of oxygen at the start, the residue with hydrogen in a eudiometer. or that air is drawn into it after the comThe process was faulty, as regards nitrogen bustion. The entire operation lasts only 20 compounds, since a portion of the nitrogen was minutes. It is to be observed that the process converted into nitrous acid. It was inappli- requires no special furnace and that by means cable, moreover, to the analysis of liquids or of of it a comparatively large weight of the subvolatile substances. Berzelius improved it by stance may be taken for each analysis. heating the mixture of chlorate and substance in a horizontal tube and collecting and weigh- Another method, proposed by Schulze, is ing the water generated by the combustion. adapted to the analysis of very small quantiThere was consequently no longer any need of ties of carbon compounds. A mixture of weighing the chlorate of potassium. He mixed weighed quantities of the substance to be anthe chlorate, moreover, with a large proportion alyzed and of fused, powdered chlorate of poof chloride of sodium, in order that the corn- tassium is sealed up and ignited in a combustion bustion might be tranquil. tube of known capacity, after the air has been The use of chlorate of potassium in this way pumped out of the tube; and the mixture of was, however, soon given up, and the process su- gases resulting from the combustion is measured perseded by that in which oxide of copper is and analyzed by the methods of absorption and employed. Quite recently, suggestions have eudiometry ordinarily employed in gas analyagain been made in favor of employing the sis. - The combustion tube is made of glass chlorate in certain cases. Mine (Comptes of the quality and strength usually employed Rendus, 56. 446) recommends the following for organic analyses, but the capacity of the method. Close one end of a glass combustion tube-to be selected should be determined aptube about 1 m. m. thick, 50 c. m. long and ir proximately by reference to the supposed comc. m. in diameter, throw in enough fused and position of the substance to be analyzed. In powdered chlorate of potassium to fill 2 c. m. the case of sugar, for example, 16 milligrm. of of the length of the tube, fill the rest of the oxygen would be half as much again as is tube almost completely with an intimate mix- absolutely necessary for the combustion of 10 ture of the substance to be analyzed and of milligrm. of sugar. The gas given off from fused and powdered chlorate of potassium, and the quantity of chlorate of potassium, about secure the whole by placing a plug of asbestos 41 milligrmin., necessary to produce 16 milligrm. at the front of the column. In making the of oxygen would occupy a space of about 12 mixture proceed as follows: — Measure out in c. c., measured at the ordinary temperature the tube itself as much of the chlorate of po- and pressure. But if this amount of gas were tassium as the tube will hold, pour out all but enclosed in a tube of 25 c. c. capacity and the last 2 c. m. of' the chlorate, mix it with the heated to 5000 or 600~, only a comparatively weighed and finely powdered substance and feeble pressure could be exerted by it upon pour back the mixture into the tube through a the walls of the tube. It may be admitted funnel. Since, according to Mene, the fuhsed that 100 milligrim. of chlorate of potassium 78 CARBONIC ACID. yield 20.805 c. c. of oxygen, and that 1000 c. c. is determined by absorption with hydrate of of oxygen at 0~ and under the pressure of' 1 potassium, in the usual way. nietre of mercury, weigh 1.8819 gralmme. Since the fundamental idea of the method The combustion tube is drawn out to a point is to operate upon very small quantities of at one end and the point closed; the mixture materiall, a very accurate balance is required. of substance and clilorate is poured into the Accordill to Schulze, the balance should be tube in such manner that no portion of the delicate enough to indicate, at the least, qualmixture shall relmain adhering to the tube near tities as small as -- of the substance weibhled. the open end. The tube is then drawn out at Balances on the principle of that of' Ritchie the lamp near the open end, to a conical point (Phil. T'rans., 1830, p. 402; see also Kalrsten's fit to receive a caoutclouc connector. Be- allgemein. Encyclop. der Physik:, Lief: 16. p. hind this point the tube is narrowed to such an 606) may be employed with advantage. extent that it can be readily closed at any mo- HIygroscopic substances may be weighed, ment by touching it with a blowpipe flame. and analyzed in the 1moist condition, it being Neither the point nor the depression in the only necessary to determine the proportion of tube mlust be made too thin, lest the glass give moisture by drying a special portion of the way when the tube is exhausted of air. material. (F. Schulze, Zeitsch. analyt. Chem., To exhaust the tube, fit to ils aperture a flex- 1866, 5. 269.) ible pipe which has been rendered impermeable Carbonates (various). to air by soaking in hot linseed oil,,and con- Principle. I)eccmposition of by acids. See' nect the other end of the pipe with an air pump, Carbonic Acid (Volatility of); and Alkalinlthe precise degree of' efficiency of which has etry. been determined beforehand by experiments Carbonic Acid. Compare the'varion empty tubes and flasks. Schulze found that ous Carbonates, below, notably the carbon-; the pump eniployed in his experiments could ates of barium, calcium, and mercury. - It remove all but 0.001715 of the original vol- may be here remarked that for estimating umie of air, so that for a combustion tube of the amount of' carbonic acid in normal car50 c; c. capacity a resliduum of 0.08575 c. c. of bonates of the alkalies and alkaline earths, air had to be allowed for, in calculating the re- it is well to determine the base by means suits of an analysis. of a standard' acid (see Alkalimetry) and When the tube has been exhausted as comn- to calculate upon the amoulnt of base ae pletely as possible, close it by throwing a blow- equivalent quantity of carbonic acid. pipe flame against the narrow place behind the Principle J. Affinity fbr alkalies. rubber connector, place the tube in an iron Appliceations. Estimation of carbonic acid. gas-pipe a little larger than itself, and heat Separation of carbonic acid fiom other gases. the iron almost to redness during 20 minutes, Estimation of carbon in organic compounds. over a row of Bunsen's burners; In case sev- ]liethods. See Hydrate of' Potassium; Sodaeral analyses are to be made, a couple of' com- Lime, and Carbon. Compare also, below, Car — bustion tubes may be placed end to end in the bonic Acid (Volatility of; absorption of the gas same iron pipe, and heated together. After in alkali), and Hydrate of Calcium. the lamps have been extinguished, the appara- Princi)ple II. Volatility. tus mav be cooled by pouring water upon the Appllications. Estimation of carbonic and iron. As a general rule the glass tubes may boracic acids. Separation of carbonic acid be withdrawn from the gas-pipe half an hour from all the bases and fiom all other acids., after the lamps were lighted. Alkalimetric determination of the comlmercial To collect the gaseous products of the igni- value of the carbonates of sodiumn and potastion, provide a rather tall, tubulated bell-glass slum. Estimation of carbonate of calcium and about 3 c. m. iv diameter, to the neck of which similar carbonates. Acidinietric determinahas been cemented a fine steel stop-cock con- tion of the value of commercial acids. Indineeted with a straight projecting tube about rect separation of strontium from calcium. 3 In. m. long by 1 mu. m. in diameter. Immerse ilelthod A. By simple iynilion. This method the posterior end of the combustion tube in is applicable to the estimation of carbonic acid mercury contained in a tall cylinder, break off in all carbonates, - such as those of 3Mg, OCd the lower point of the tube in the mercury, push Zn, Pb, Cu, Ni, etc, - which give off the acid the tube down into the mercury and place the readily and completely on being heated. Even bell-glass full of' mercury over the top of the with carbonate of calcium carbonic acid can tube. Then break the upper, anterior point of be determined in this way, if only.a small quanthe combustion tube so that the contents of the tity of substance be operated upon and the tube may rise into the bell. From the bell the heat be made intense. gas may be readily transferred to a measuring If the carbonate to be analyzed is anhydrous, tube by simply sinking the bell beneath the and contain no metal liable to form a mixture tube and opening the stop-cock. - After of several oxides, when heated, it will be the total volume of gas has been measured, enough to ignite a weighed quantity of it in with the proper precautions, the carbonic acid a crucible until the weight of the crucible and CARBONIC ACID. 79 contents remains constant. The loss of weight The difference (x-W) between the weight will represent the carbonic acid. In case car- of the supposed carbonate of strontium, and bonate of lead, carbonate of cadmium, or any that of the mixed carbonates actually found, is other easily reducible carbonate is to be an- proportional to the quantity of carbonate of alyzed, the crucible must be of porcelain. calcium in the mlixture, so that the weight of If the residual oxide is prone to absorb oxygen the last named salt may be obtained by the when heated in the air, replace the crucible proportion: with a bulb-tube of hard glass, and pass a Difference between Wt. of streamimoire. weig c CoO, ot. COoC02 stream of carbonic acid through the tube dur- tSOe CaOht C.O\ Y i the ing the process of ignition. This method 47. iixedcarb's/ yields very accurate results. In short, multiply the carbonic acid found If the substance to be analyzed contains by 147.5 * 44 (- 3.3534), deduct from the water, it is soletines possible to estimate the product the weight of the carbonates, and inulwater before the carbonic acid, by first heating tiply the difference by 100 — 47.5 (- 2.10526). a weighed quantity of the material gently until The product will express the weight of the the water has been expelled, and afterwards in- carbonate of calcium. The difference between tensely to drive out the carbonic acid. In case this weight and that of the mixed carbonates the water cannot be determined in this way it will give the weight of the carbonate of stronrmay be estimated as follows: — Weigh out a tiuln. The process gives good results unless quantity of' the substance in a small boat, and the quantity of one or the other of the metals place the latter in a tolerably wide glass tube. in the mixture is too minute. By means of dry, tight corks, attach a weighed Precaluios. The mixed precipitate should Chloride of' Calcium tube to one end of the be thrown down fiom hot solutions. During wide tube, and an unweighed chloride of cal- the process of ignition the agglomerated mass cium tube to the other end. Connect the other should be turned over now and then in the end of the weighed chloride of calcium tube platinum crucible, and pressed down carefully with an aspirator, and draw a slow stream of against the hot metal until, after repeated igair through the apparatus. Heat thie boat and, nitions, its weight remains constant, If the from time to timle, the whole of the wide tube, operator prefer, the carbonic acid may be estiuntil all the carbonic acid and water have been mated by fusing with borax glass (see below), expelled firom the carbonate and carried for- but a moderate white heat such as may readily ward into the chloride of calcium tube. Allow be obtained by a blast lamp is sufficient for the the apparatus to cool and weigh tile boat and purpose. (Schaffgotsch, Pogg. Ainn., 113. the chloride of' calcium tube. The difference 615). between the first and second weights of the klethod B. By ignition with a solid, noncontents of the boat gives the total amount of volatile acid, or acid salt. By this method, carcarbonic acid and water; the increase in weight bonic acid can be separated firom all the bases of' the chloride of calcium tube gives the which form anhydrous carbonates, and its amount of water, arid the difference between amount determined with great accuracy. The the two, the carbonic acid. - Care mnust be principle is applied also in organic analysis, taken neither to leave any moisture in the wide for expelling carbonic acid from the carbonates tube nor to burn its corks. To prevent the of K, Na, Ca, Ba and Sr, in cases where possibility of any moisture passing back from either of these compounds is formed during the the aspirator into the weighed chloride of' cal- combustion of the organic substances. The cium tube, it is well to interpose an unweighed same principle is involved, moreover, in the chloride of calcium tube between the two. method of estimating boracic acid indirectly by Instead of weighing the substance in a boat, igniting a carbonate with borax glass, as has it may just as well be placed in a bulb-tube. been explained under Boracic Acid. It is apIn case the substance to be analyzed is likely plied also to the indirect separation of bariun to absorb oxygen when heated in air it should from strontium or calcium, and of strontium be ignited in a current of dry carbonic acid. front calcium, as will be explained irmneIndirect separation of Calciumz from Strontium. diately. Precipitate the two metals as carbonates, - 1. Fusion with Borax-glass. Fuse a quantity see Carbonate of Calcium, -- weigh the mixed of borax-glass (see biBorate of Sodium) in a precipitate and call its weight W. Afterwards weighed platinum crucible, place the crucible ignite the precipitate at a moderate white heat, with its contents in a dessicator to cool, and until all the carbonic acid has been driven out weigh when cold. Place in the crucible a quanfrom both the carbonates, and weigh the resid- tity of the carbonate to be analyzed, and again ual oxides. The difference between the two weigh so that both the weight of the carbonate weights will give the weight of the carbonic and that of the borax may be known. The acid. Calculate this carbonic acid as if the carbonate should be perfectly dry, and should mixed carbonates were really nothing but car- weigh about a quarter as much as the borax bonate of strontium, thus, glass. Gradually heat the mixture to redness, Molec.wt. wt. olec. wt. of Weight of / Weight of and keep it at that telnperature until the conf44 1C02 47.5 fl2 Srf SU0oe tents of the crucible are in a state of tranquil 44 147o5, found ppoo C teit 80 CARBONIC ACID. fusion and no more bubbles of carbonic acid the potash bulbs, and also to interpose an unescape from the molten liquid. No heed need weighed chloride of calcium tube between the be taken of a few persistent bubbles of gas absorption tubes and the aspirator, to guard which are liable to remain in the liquid. Again against the aqueous vapor which may arise place the crucible in the dessicator and weigh from the latter. - Place in the combustion it, with its contents, when cold. The.loss of tube from 30 to 60 grins. of bichromate of poweight represents the amount of carbonic acid tassium, which has been fused just before the in the substance analyzed. The mixture must experiment, together with from 1 to 3 grms. not be ignited over a blast lamp, lest a certain of the carbonate to be analyzed, and place a amount of borax glass be lost through volatil- loose plug of ignited asbestos in front of the ization. (Schaffgotsch). mixture. Carbonates of the alkali metals may To separate barium from strontium or from be introduced in the form of fragments, but calcium, by the indirect method, throw the two most of the other insoluble carbonates must metals down together as carbonates, see Car- be finely powdered and mixed with the bichrobonate of Barium (insolubility of), and note mate. After the mixture has been placed in the weight of the mixed precipitate. Then the combustion tube, and the latter connected expel the carbonic acid by fusing with borax- with the absorption tubes, heat the mixture of glass, and note the weight of the acid. The bichromate and substance, and allow a slow proportion of the different metals in the mixed stream of water to flow from the aspirator, so precipitate may be calculated as follows. Corn- that a current of air shall be drawn through pare the method by simple ignition, above. the apparatus. The evolution of carbonic To separate Ba from Sr: — Calculate the acid begins as soon as the bichromate melts, carbonic acid as if it belonged to strontium, and it admits of being easily regulated. The thus: — operation is finished when the whole of the Molec. w t.of t. of CO /.( Weight of mixture is seen to be in a state of tranquil 4 147. sfound, uposed f hsion. The increase in weight of the potash 44 c S1wigt o Cas and subtract from this supposititious weight bulbs or soda-lime tube. gives the weight of the weight of the mixed carbonates (bW) the carbonic acid, and that of the chloride of found. The number (x-Wc) thus obtained, is calcium tube the weight of thewater in the subroportion ml to the quantity ofu carbonate of stance analyzed, in case any water was present. bprorium in the ixture; hence the weight of The presence of sulphites or hyposulphites, or the barium salt may be obtained by th e pr- of sulphides or oxysulphides of the alkali or portion. alkaline-earthy metals, does no harm, but the Diff. between substance analyzed must of course be free from molec. wts. of Molec. wt. of Wt. of BaO, CO2 carbonaceous matters. SrO, CO2 and: BeO, C02 (x - W) (- ito the._BaO, Co2 197 mix ed cabonates) The process may be applied not only to the 49.6 estimation of carbonic acid for its own sake, In short, multiply the carbonic acid found but for determining the alkalimetrical value of by 147.5. 44 (= 3.3534), deduct from the the carbonates of potassium and sodium. (See product the weight of the mixed carbonates, below, under" Expulsion of Carbonic Acid by and multiply the difference with 197 * 49.5 Acids"). (Persoz, Comptes Rendus, 53. 239). (-4.4246). The product wilt express the 3. In the analysis of organic compounds weight of the carbonate of barium. The dif- which contain an alkali-metal or a metal of one ference between this weight and that of the of the alkaline earths, mix the substance with mixed carbonates will give the weight of the a quantity of boracic or antilllonious acid, or carbonate of strontium. with phosphate of copper, before placing it in To separate Ba fiorm Ca, proceed in a simni- the combustion tube. (Compare Carbon). lar way, calculating the carbonic acid, at first,.Method C. Expulsion by acids at the ordias if it were all carbonate of calcium. nary temperature. By this method carbonic 2. Fusion with Bichromate of Potassium. acid may be separated from all bases, without Select a combustion tube of hard glass 50 or 60 exception. The evolved gas may then be c. m. long, and bend it in such manner that it measured as such, or determined as loss, or esshall be very slightly U-shaped at the middle, timated indirectly from the weight or by the while the two ends remain horizontal. Fasten analysis of the residue, or, better, it Imay be to one end of this tube a pipe closed with a deterlninedl by absorption in an alkali in accordcopper stop-cock and connected with a perma- ance with Principle I. nent set of potash and chloride of calcium 1. By Loss. The earlier chemists were contubes, suitable for removing carbonic acid and tent to throw a weighed quantity of the carwater from the air. To the other end of the bonate to be analyzed into 3 or 4 times as much combustion tube attach a weighed chloride of chlorhydric, nitric, or sulphuric acid contained calcium tube and a set of potash bulbs, or a in a tall cylinder, and counterpoised upon a soda-lime tube, precisely as in the estimation balance. When the effervescence ceased, the of Carbon, and to the potash bulbs attach an increase of weight on the part of the cylinder aspirator. It is well to attach a small supple- was noted, and the diffirence between that muletary wveighed chlori of( calcium tube to quantity and the weight of carbonlate taken CARBONIC ACID. 81 was reckoned as carbonic acid. Care was ing or counterpoising it. Then hold the flask taken to avoid loss by spirting, and that the in an inclined position, so that the acid in the operation should proceed rather rapidly, so that bottle may run out, little by little, upon the as little acid as might be should be lost by carbonate. The carbonic acid set free is dried evaporation. The acid usually employed was more or less completely as it passes out through either nitric acid of 1.15 sp. gr., or a mixture the chloride of calcium tube. After the of strong chlorhydric acid with an equal bulk evolution of gas has ceased, remove the stopof water. (Pfaff', Handbuch analyt. Chemn., per friom the narrow glass tube, attach to the 1824, 1. 505; 2. 18). Of late years, however, latter an unweighed chloride of calcium tube, the method has been greatly perfected by the connect the permanent chloride of calcium invention of apparatus specially arranged so as tube with an aspirator, and draw a quantity of to avoid the risk of loss by evaporation or air through the flask. After all the gaseous transportation of the solvent acid. contents of the flask have been swept out by A great many different forms of the appara- the current of air, there still remains a certain tus have been devised by chemists, see, for ex- quantity of carbonic acid dissolved in the ample, MlIohr's Titrirmethode, 1855, p. 122, and liquid at the bottom of the flask. In order to Fresenius's Quantitative Analysis, 1865, p. 300. remove this dissolved gas, disconnect the flask The essential features of the apparatus are, from the temporary chloride of calcium tube 1st, a small glass flask, in which to place the and aspirator, plug the narrow glass tube, and substance to be analyzed, and in which, at the slowly heat the contents of the flask to incipproper moment, to mix the substance and the ient boiling. Then remove the plug, re-attach acid by which it is to be decomposed; 2d, a the chloride of calcium tube and the aspirator, tube or flask to hold this acid and keep it away and again draw a quantity of air through the from the carbonate until the time when the flask. When all the carbonic acid has been operator sees fit to mix the materials; 3d, a swept out, disconnect the flask from the aspichloride of calcium tube, or other apparatus, rator and temporary drying tube, plug the narfor drying the gas evolved by the action of the row glass tube, allow the flask to cool fobr half acid on the carbonate, so that nothing but ab- an hour in the room of constant temperature1 solutely dry carbonic acid can escape from the replace it upon the balance and determine how flask. much less it weighs than at first. The loss of A simple form of the apparatus may be weight represents the carbonic acid in the submade as follows: Choose a small, wide-mouthed stance analyzed. - Good results are someflask, and fit to it a soft cork or rubber stopper times obtained in this way, but it is nevertheless with two perforations. Pass the stem of a a matter of common experience that the loss chloride of calcium tube through one hole of of weight of the apparatus cannot be counted the cork, and insert in the other hole a narrow as carbonic acid with certainty. If the dilute glass tube bent at a right angle and reaching acid liquor in the flask be heated long enough nearly to the bottom of the flask. Make a and strongly enough to expel all the carbonic small bottle, like a homceopathic phial, from a acid which is dissolved by it, some aqueous vapiece of tolerably wide glass tubing, by closing por will be driven out of the apparatus also, one end of the tube at the lamp, and pressing and lost. In most cases, where good results are the softened glass flat, so that the short tube, obtained, the agreement is really due to the or bottle, may be made to stand upright. This compensation of opposite errors, as may be little bottle must be capable of passing readily seen by trying the experiment of repeatedly through the neck of the flask. To the top of heating the flask of' the apparatus and sucking the bottle tie a thread, or better, a piece of air through it. If the suction be continued fine platinum wire, a little longer than the flask just long enough, the diminished weight of the is high. apparatus. will exactly correspond to the carThe actual analysis is performed as follows: bonic acid that was contained in the substance, Place in the flask a weighed quantity of the but further exhaustion of' the air will diminish carbonate to be analyzed, and fill the little bot- the weight of the apparatus, not by complete tie two-thirds filll of acid. By means of' the removal of' the carbonic acid, but by loss of' thread or wire lower the bottle carefully into aqueous vapor, which easily escapes through the flask, leaving the upper end of the thread the dessicating material. By continued workprojecting from the flask. Press the cork into ing on a carbonate of' known composition, one the neck of the flask so that the thread or wire may soon learn how long to exhaust in order to may be held firmly between the cork and the bring about the proper loss, but where the anglass, taking care not to spill any of the acid alyst is out of' practice an error of' 1 or 2 per out of the bottle. Plug the outer end of the cent is not unlikely to happen, and the process plain glass tube with a small ball of wax, or itself' furnishes no means of' judging when it better, with a bit of rubber tubing closed with will give a correct result. (S. W. Johnson, a short piece of glass rod, and leave the appa- Almer. Jounrta. Sci., 1869, 48. 111). A far ratus at rest during 15 or 20 minutes in a room better method is to charge' the apparatus with of tolerably constant temperature before weigh- carbonic acid gas in the first place, and to weigh 6 82 CARBONIC ACID. it full of carbonic acid as soon as the diren- strong standard sulphuric, nitric, or chlorhygag'ement of gas has ceased. See below, John- dric acid. As thus modlified, the process is son's 7n1odi/icotion. peculiarly usefill for ldetermining the relative Choice of' Ithedecomnosiy acid. Usually the proportions of' carbonic acid and base in unacid cmployed for decoimposino the ('arbonate weighed j quantities of moist, recently pirecipiis either sulphuric, nitric, chloirhydric or oxalic. tated carbonates, and in carbonates' which canW~hen the substance analyzed contains a fluo- not be dried without stfferini' deconiposition. ride, however, some weak, non-volatile acid, (Stolba, Joorn. ]i;ra/t. Cheo., 97. 312 ). such as tartaric or citric acid must be employed Aplicotioo to Ai/,alinetri. The li method to set firee the carbonic acid, for if' either of now in question is som etimes employed as ain the mineral acids were used, some fiuorhydric alka limletric process for determnining tie value of acid would be evolved. Sulphuric acid is to be coommercial carbonates of sodiumni or potassiun preferred for the treatment of the carbonates in cases iwhere the carbonates are striongly colof' all those metals wvhich formn soluble sul- ored. For this alkalinetric determination a phates, but is unfit for decompnosing the carbon- fbrnil of' apparatus devised by Fresenius & ates of nmetals which fbrm insoluble compoundls W1ill is usually employed. Thiouoh similari in with sulphuric acid, for the insoluble layer of principle to the apparatus above described, tlhe sulphate formed by the action of the first por- aikalimneter of' these clieoiists is peculiar in tions of' the acid would cover over a part of soine of' its ldetails. It may be readily mnde t4mc carbonate, and prevent the acid from corn- as follows:-Select two smiall, liht Berlin ing in contact with it. Nitric, or in soene in- flasks. Fit to each flask a cork or caouttchouc stances chlorlhydric, acid must therefore often stopper, and bore tvwo holes in each of' the be substituted fbr the sulphuric acid, corks.. Place thile flasks uiipon a table, side by When chlorhyldric acid is used to decompose side, so that they shall almost, but not (quite, a carbionate, or in case the latter is contami- touch one another. Call the flask at the left nated with a cliloride, the escaping carbonic baud L, aiid the other R. Bend a olass tube acid should be made to pass through a tube at two right anigles, in such manner that one filled with some substance, like anhlydrous sul- leo1 of' the tube may pass into the flask L, and phliate of copper, which has power to retain the other into the flask R. Push one lee of both water and chlilorlydric acid. To prepare the bent tube through one of'the corks and the the sulphate of' copper, boil fragmients of purm- other through the other. Cut off' one leo of ice stone in a concentrated aqueous solution of the tube just below the cork of the flask L, but blue-vitriol, and dry and heat the stone until leave the other leg' long enouogh to reaclh almost the copper salt is completely dehydrated and to the bottomni of' the flask 1,. Through the has become white. A U-tube about 8 c. ni. second hole of the cork in L pass a straiilht high and 1 c. in. bore filled with the sulphate tube, open at both ends, lonug enonugh to reach will usually be found sufficiently lar e; it umay ahlnost to the bottom. of the flask, and tlihrouhi be used as lonim as a third of its conitents re- the corresponding hole of' the cork in IL push main uncolotlred. (Stolba, Diangler's polfytech. a similar, but shorter, tube long enough to )proJoton., 164. 128). In case a carbonate fit to ject a few in i. b. elowv the cork. - he be treated witlh suiilp huri acid happens to be size of the flasks minust be determined by the contamiinatei with a chloride, the risk of evolv- capacity anid dtelicacy of thie balance at thel dising chllori) dnric acid iiay be avoided by iixing posal of tlihe operator. If' the appar:itus is to the weighbed carbonaite with a quIantity.of a be weighlied upon a delicate chenical balance, it solution of' sulphate of silver before addting the imiay be iaile so light that when fully cliargeed a(cid. So too if thie carbonate contains a sul- with acid it need not wveidih more tihan 70 or 60 phite or a sulphide, these salts may be oxidized giramimes but as a general rule it will beli fuiiid by treatinmg the wveiohed cirbonate with a solu- morie convenient'to use soimemihat larger flasks tion of ycllow chromate of potassium before andi to olperiate upon a coarser balance. addinu the acid. To use the apparatus, plug the upright tube In some cases it mwill he found advantageous in the flask L, as directed in a previous h;parato tdetermine the metallic base of the carbon- graph; pour tihe w eigohed carbonatet into I antid ate, by Alkalinrrety, in the solution left in the addc to it enouoh water to fill about a thirdh of flask. In this event, mix the weighed carbon- the flask. Iour enough strong suilphuriii acitd ate with a wmeig hed quantity of crystallized into the other flask, RL, to half fill it; re-place oxalic acid moire than suffcient to deconqpose the corks mand push theii tighlitly into the the vwhole of the carbonate, charge thle tube mouths of the flasks. Let the apparmatus stand withi water, and at the proper timge pour tfle 15 oir 20 minutes in a roomi of tolierably conwater upon the mixture of' acid anti carbonate. stant tenicleraciture, and then couniterpoise it After all tihe carbonic acid has been expelledi upon a i balce. Attach a lpiect of' ctuoutchotic firom the fiaskl, detterimine how mnuch of the tubirio -to the upright tube in it, and lirotecd oxalic acid has been left fice by titrating with to test tihe tfinitmc ss of the apparatus. l' t t o an alkaline solution of 1kinowni strengtlh (see this mntl, iid.l oit i la, small quantity of air fi'rom Al-kaliniety ). Instead oft usino solii oxalic the flask I, so thimt, au ft bubbles ofi imIy acid, the tube miight be charged with tolterably escep)e froumi L o into throuol the sulphmuic CARBONIC ACID. 83 acid, to supply the partial vacuum which has loosened. The quantity of nitric acid taken been created in R. Then remove the lips must be more than sufficient to decompose the firom the caoutchouc tube, and suffer the ex- whole of the carbonate. ternal air to enter R. If the apparatus is tight, In case the metallic base of the carbonate is some sulphuric acid will be pressed up tolwards to be determined as well as the carbonic acid L, in the bent glass tube, and will remain sta- (see above, p. 82), a measured quaantity of tionary in the tube. Watch the column of' sul- standard acid must be introduced into the phuric acid for a few minutes to see that it bulb-tube. To this end, hold the tube point does not sink back into IR, and( then suck a upwards, warm the point over a lamp, and quantity of air from R, somewhat larger than touch it with a bit of' tallow in such nlanner before. On removing the lips froom the caout- that a little of' the tallow may solidify ill the chouc tube, a portion of the sulphuric acid in tube, and close it water titght. Then invert IR is forced over into L, and decomposes a cor- the tube, fill it through the upper opening with responding quantity of' the carbonate therein the acid, measured friom a Molhr's burette Nwith contained. The carbonic acid set fiee passes fine point, plug the upper opening in tlhe usual through the sulphuric acid in R, and is thereby way, and heat the point of tile tube gently undried before escaping into the air through the til the tallow is melted. open, upright tube. As soon as the efferves- After the apparatus has been counterpoised cence in L slackens, suck out more air fioom R, carefully push clown the bulb-tube until it so that a new quantity of sulphuric acid may touches the water, and at intervals loosen the be forced over into L, and repeat the opera- plug so that small quantities of' the nitric acid tion at intervals until the'whole of the carbon- may flow out upon the carbonate. As soon as ate is decomposed. When the effervescence has the carbonate has been completely decomiposel, entirely ceased, force over a comparatively suck air throughl the apparatus is before, andl large quantity of' the sulphuric acid into L, so finally hleat the contents of' the flask 1 to inthat the contents of that flask mlay be consid- cipient boiling, in order to set fiee thle last erably heated. After a few moments, remove traces of' the gas. the plug firol the upright tube in I,, attach to o A?)licclaion to Acidimei?/y. The v-olatility the tube a chloride of' calciunl tube, and by of carbonic acid has been mnade the basis, not means of the caoutchouc tube at the other only of' a process of alkalimetry, as just (leflask, suck air through the apparatustuntil this scribed, but of m Iethod of' acidmllmnety as weill. air no longer tastes of carbonic acid. Let the It is in fict easy to estimate the strengthll ot' ay apparatus stand at rest in the room of constant samnple of acid, by wreighing the carbonic,acid temiperature for 2 or 3 hours, replace it upon set fiice from bicalrbonate of sodlitnnl )y1 tole the balance, and bring the latter into equilib- acid in qluestion.'he operatiol is as follo)-s: — rium by means of' weights. T'he sumn of' the In tile flasl L of the apparaltus just described, weights added indicates the ainouint of'carbonic weigh out a quantity of' the acid to be exacid which has been expelled fiom the sub- auidned, and if' it be colcentralted, dilute it stance analyzed. wvith xwater. In either c-'se, tile fluid slhoull. Tolec. wt. of olc. w. of. of CO2 Wt. ofXaCO0 fill about a third of th flask, IFill ia sml CO2 NaCO3 found in sallle oglass tube compactly with bicarl)onlat of' oTolerably accurate results may be obtained dlirni or of' lotassium. Tie a th-lread to the by this method, unless the proportion of' car- tube and ihain, it ill the flask L hIy pressing tile bonic acid in the substance analyzed is very thread between the cork and tile neck ot thle small. flask. The iquanltity of bicaribonate talen 11lust To fit the apparatus just described for the be mlore thlil sufticient to saturate tlle acid in analysis of lime-stone and the carbonates of the flask; the salt mlust be'ee iioln f mi inoocatother metals fborining insoluble sulphates, re- bonatc, but the presenlce of cllloride or slliphate, place the strlaight, upright tube in L by a tube etc., of soliml, (loes iino harml In other reslccts which has been blown to a somewhat capacious tle appalratus is charged in tile nmanner allready bulb near the top, and cldrawn to a fine point describele in the se wliere thle uproilt tulbe at the lowver end. The apparatus is charged in I, is straigiht. After thle apparatus ihas beeii as before witli the exception that the bulb-tube counterpoisedl, loosen the cork of' the filsla L, is filled with dilute nitric acid, and that at the so that the thread may slacken an( let the tuie start the lower part of the tube is not pushed of bicarbonate tall to the bottoml of the flask, so deep into the flask as in the other case. aind at the samle instant replace the cor k as Care must be taken that the point of the bulb- tightly as possible. Carbonic acid is given off' tube does not touch the water in L until after violently at first, thien fro some time at a unithe apparatus has been counterpoised on the form rate, afterwarcs slowly until the evolution balance. ceases. When no more gas is evolved, put the Like the straight tube of the apparatus pre- flask L in water of from 50~ to 55~ C, so hot viously described, the bulb-tube must be closed that the fin(er cannot long be heldl in it, and at tlhe top with a moveable plug so that none when the reinewed evolution of gas thus occaof the nitric acid can flow out until the plu.g is sioned has ceased, suck air through the appa 84 CARBONIC ACID. ratus, as before. When practicable, enough gas. Then plug the top of the chloride of calacid should be taken to set free a gramme or cium tube, disconnect the apparatus from the two of carbonic acid. source of carbonic acid, plug the upright tube and immediately weigh. Take care to handle In Johnson's Modification of the foregoing the apparatus carefully so that its temperature method of estimating carbonic acid, the a ppa- shall not be changed by the warmth of the ratus is weighed full of carbonic acid, both be- hands. After weighing, loosen the plug of the fore and after the experiment, so that there is chloride of calcium tube, and, holding the no need of sucking out any gas from the flask. flask by a wooden clamp, incline it so that the The dessicating material has consequently to acid may flow over upon the carbonate. The dry only as much gas as is yielded by the sub- decomposition should proceed slowly, so that stance subjected to analysis. The process thus the escaping gas may be thoroughly dried. As modified is much better than befbre, and is soon as the whole of the carbonate has disdecidedly to be preferred to the old method in solved, replace the plug in the chloride of calall cases where the substance to be examined cium tube and weigh the apparatus. - All dissolves freely and completely in cold acid. the joints of the apparatus must be gas-tight; The apparatus may consist of a light, wide- should there be any leak it will be made evimouthed flask or bottle, from 3 to 3.5 c. m. wide dent at the final weighing, by a slow but steady by 6 c. m. high, closed with a caoutchouc stop- loss of' weight as the apparatus stands upon the per, to perforations in which are fitted an up- balance. If all the joints are sufficiently tight, right chloride of calcium tube and the bent the weight will remain the same for at least 15 end of a tolerably capacious bulb-tube, which minutes. Since the temperature of the flask serves as a reservoir of acid. A good chloride usually rises a little during the solution of the of calcium tube may be made by blowing two carbonate, it is best, after the decomposition oblong bulbs, each 2.25 c. m. broad, on a glass of the latter is completed, to plug the chloride tube. When finished, the tube may be about of calcium tube and leave the apparatus at 10 c. in. long. The lower bulbis filled with cot- rest for 15 minutes; then connect with the carton, the upper with small fragments of porous bonic acid generator as before, and pass dried chloride of' calcium, and the top of the tube is carbonic acid for a minute before weighing. closed with a rubber connector, plugged with When properly executed, the process gives a bit of glass rod. The acid reservoir may extremel~y accurate results. It is essential, be made by blowing an oblong bulb about however, that the operation and the weighings 3 c. m. wide by 5 c. m. or more long, on a tube be conducted in an apartment not liable to sudof about 7 m. m. internal diameter, and bending den changes of temperature. A slight change the tube in such manner thalt while the bottom of temperature or of' atmospheric pressure beof the bulb, or rather the bent tube imme- tween the two weighings greatly impairs the rediately adjacent to the bottom of the bulb, sults, or renders them worthless. shall rest upon the table, close beside the flask, In the case of alkali-metals which absorb there shall be a short, bent delivery tube carbonic acid gas, a small bottle of thick glass to connect the upper, narrower end of the and wider mouth should be used in place of bulb with the rubber stopper, and at the other the flask above described. The stopper of this end of the bulb, a tube pointing upwards and bottle should have three holes, the third to reaching to the level of the top of the flask; carry a narrow tube 3 or 4 inches long enlarged this longer tube serves for the introduction of below to a small bulb, to hold the carbonate. carbonic acid at the beginning of the experi- This bulb must be so thin that on pushing down nient. The extremity of the upper or delivery the tube within the bottle, it shall be easily:tube reaches fairly through the rubber stopper; crushed to pieces against the bottom of the latit is ground off obliquely, so that no drop of ter. The carbonate is weighed into the bulbliquid can be held in it. At the top of the tube, the latter is wiped clean, corked and fixed tube for introducing carbonic acid there is a in the rubber stopper. The apparatus is filled;short rubber connector with a glass-rod plug. with carbonic acid and weighed. The bulb is The actual analysis of carbonate of calcium, then broken and the process proceeded with for example, is made as follows; —Put from precisely as above described. (S. W. Johnson, half a grin. to a grin. of the substance, best in Amer. Journ. Sci., 1869, 48. 111, and the the form of small fragments, into the flask. American edition of Fresenius's Quant. Anal., Fill the bulbed acid reservoir nearly full of New York, 1870, p. 202. The apparatus is chlorhydric acid of' 1.1 sp. gr. Fit the rubber figured in both places). stopper, with its appurtenances, tightly into the mouth of the flask; remove the glass-rod 2. By measuring the carbonic acid gas. The plugs, connect the upright tube with a self- process is applied to the determination of carregulating carbonic acid generator, and pass a bonic acid in soils, manures, mortars, marls, rather rapid stream of washed carbonic acid bone-black and the like. Also in the analysis through the apparatus during 15 minutes, or of mineral waters and blood. Like the foregountil the acid in the bulb is saturated and all ing method it may be used for estimating the the air in the flask has been displaced by the alkalimletric value of the carbonates of' potas CARBONIC ACID. 8.5 slum and sodium. For the determination of lecting bottle and the zinc cylinder, the latter small quantities of carbonic acid, the method is made tight; it is then filled with water. The by measuring is thought by some chemists to collecting bottle is also filled with water, tobe preferable to either of the other methods. gether with enough fatty oil to form a thin As described by Pfaff (Handbuch analyt. layer upon the surface of the water. Chem., 1824, 1. 505; 2. pp. 18, 77), the pro- In an actual analysis, a weighed quantity of cess consisted in putting small fragments of' the the substance, such as marl or lime stone, to carbonate into a graduated tube charged with be examined, is placed in the decomposing botchlorhydric acid, and placed, full of mercury, tle. The retort is three-fourths filled with diin a mercury trough. In case the substance lute chlorhydric acid of 1.05 or 1.07 sp. gr., to be analyzed was in the state of powder, it and the stopper to which the retort is cemented was done up to little pellets in paper which is carefully greased and inserted in the neck of had been previously leached with chlorhydric the decomposing bottle. The apparatus is left acid. Due allowance was made for tempera- in a room of tolerably constant temperature ture and barometric pressure. - The more until the retort and decomposing jar, as well modern methods are as follows:- as the water in the zinc cylinder, have acquired A. Method of Schulze. This method may the temperature of the air of the apartment. be used for estimating the proportion of car- The stopper of the collecting jar is then bonate of calcium, or any other carbonate, in smeared with tallow and inserted in its place, rocks, soils and manures, and in general for all and the glass tube in the side orifice of'the colcases where the substance to be analyzed is lecting jar is turned perpendicularly downbulky, the volume of gas to be evolved is large, wards. A beaker is placed beneath this tube or the evolution of gas attended with frothing. to catch the water which flows from the colThe apparatus required consists of two glass lecting bottle. If the apparatus is tight, only bottles, one for decomposing the carbonate and a small quantity of water will flow from the the other for collecting the gas set free, a tu- bottle when the tube is turned down. Incline bulated retort to hold the acid by which the the decomposing bottle to such an extent that decomposition of the carbonate is to be effected acid may slowly flow from the retort upon the and a small metallic water-tank to cool the carbonate in the decomposing bottle. The collecting bottle. - Heat the upper part of carbonic acid evolved will pass over into the the neck of a small tubulated retort in the collecting jar, while water will flow out of the flame of a blast lamp, and bend the softened latter into the beaker to make room for the glass in such manner that the neck of the retort gas. As soon as the decomposition is finished, shall point almost perpendicularly downwards. prop up the beaker beneath the tube of the Obtain a stout, two-necked bottle of about 350 collecting jar so that the mouth of the tube c. c. capacity, for the decomposing jar, and an shall be immersed in the water, and set the aspirator-flask of 1 or 1.5 litres capacity, for decomposing bottle in a jar of water of the the collecting bottle. One of the orifices of same temperature as that in the zinc cylinder. the decomposing bottle must be tolerably wide, As soon as all parts of the apparatus have and thick and strong in glass, while the other acquired a common temperature, remove the opening is made in the form of a plain project- beaker of water, turn the water delivery tube ing tube. To the upper orifice of the collect- of the collecting jar perpendicularly upwards, ing bottle, and to the wider orifice of the de- take out the stopper of the retort for a moment, composing bottle, fit perforated ground glass again turn the water tube downwards, and colstoppers. Cement the neck of the bent retort lect by itself the small quantity of water which into the perforation of the stopper of the de- flows from the collecting jar. Measure this composing bottle, and a short, straight glass water and note the quantity. Measure also tube into the perforation of the stopper of the the water which was previously collected in the collecting bottle. Connect the two bottles by beaker. The difference between the two quanmeans of a caoutchouc tube, one end of which tities will give the volume of the carbonic acid is tied to the projecting neck of the decompos- under the existing conditions of temperature ing bottle and the other to the straight glass and barometric pressure,-subject also to a tube in the stopper of the collecting bottle. correction for the tension of aqueous vapor at Place the collecting bottle in a zinc cylinder as the temperature in question. tall as the bottle and provided with a lateral The weight of the carbonic acid obtained may opening near the bottom corresponding to the readily be calculated from the volume, by referorifice in the side of the bottle. Close the side ring to the known specific gravities of carbonic opening of the bottle with a cork carrying a acid and air, or it may be determined still more glass tube bent at a right angle, the longer simply by decomposing a known quantity of limb of which projects upwards a little higher pure carbonate of calcium in the apparatus. than the top of the bottle. The bore of this The weight of the volume of carbonic acid obtube should be about 4 or 5 m. In. in diameter tained from the pure carbonate being known, excepting the point, which is narrowed to 2 a priori, this volume may be directly compared m. m. By means of a short piece of caoutchouc with any other volume of the gas. By operattubing tied to the lateral tubulures of the col- ing in this way, moreover, several slight sources 86 CARO3NIC ACID. of error incidental to the method of experi- the liquor. The volume ofhydrogen equivalent mentinog may be voicd. It is not even nee- to the zinc employ ed is subtracted fi'om the essary to use pure Cxrbonate of' calcinmn for the ineasured volume of carbonic acid and hydrocoinmparative experiment;, nlmost any samnple gen. This method of dlisplacement by of' narble wlios{e pecrentag'e of carboniC acid las ha hydrog en becomes somnewhati more commplicated been carefuilly determined will answer as Ae!l. in certain cases, particularly in presence of Altcr thie vahle of' a inmirble has once been de- nitric and oxalic acids, ferric oxide and other terilleli tbo' this. purpose a consieraiible store substances capable of prieventing the evolution of' the material had bettel be kept on ihand. of hydrogen. Soils, fbor example, not only conTihe process is simple and is said to myield tain substances which combine, with and retain exeeedling!y accurate results. nascent hydrogen, but the zinc powdIer becomes n oeohfetioi.. IThe oil employcd to cover the so completely enveloped by tihe earthy particles wat1er in the collectini- bottle mnut be ireieh andl that a long time is required in order that tihe inilsposed to raniciditY. In practice it is ibund whole of' the metal miav dissolve. In order to tlmat the oil absorbs carbonic acid so slowlay that displac carbonic acid by hydrogen therefore, tha loss of' as foiiiol this cause dfurini time time in analy zinmo soils, nmanures and the like, it is 7rel,,irei for an expeiriment is scarcely aplpre- necessary to treat the zinc with acid in a speci able. - Care iiust be talken not to waiirm ciil vessel and to lcad the free hydrogen the collectino bottle with thle hand wlien the thriouol the solution of carbonic acid. stooper is placedl in tie bottle. The clloi A convienient way of arranging tie apparahyvh'ici acid emiiployed had be, tter be of 1.05 or tus is to interpose a second two-necked bottle i.07 sp..r., since a stroinger acid wouldl afect between the decoimposing and collecting botthe tension of( thie aqueous vaporl in tihe appair- tles The orifices of this second bottle are atius. - i Tile control explerime nt it malir- closed with perforated caoutchouc stoppers, ble or piure carbcma te of cailci'ui is of' special tlhrouoh one of which a glass tube passes to value in cases, — sucl as the analysis of arti- the bottom of the bottle. Thie upper end of fit ial iniuireseois, lacit aslihe, iiild thie lie,- c this glass tube is connected, by means of a wheire tile inopoertiion oe carbonic acid iil the caoutcliouc tube, with the outlet of the decomsubstance is so smallthiat a coinpara'tivcly large posingl bottle. A short, straight glass tube quantity of' lilquii hIas to be mixed with the pl ctel in the pecrfbiration of the other stopper substance in orde trit the carbonate contained is conncted, by mceans of another flexible tube, in it mao be awholliy cicon mposed. The liquitd with the top of the collecting bottle. The subof course rietains a quantti ty of' carbonic acid stance to lbe analyzed is placed in thle noewv twoin solution, b1ut by repeating the experiment neckled bottle toogether Aith a test tube ft:ll of with inarblle which has been mixed with a eclorhydric acid of 1.05 sp. gr., wvile the quantity of' inert sand aand as minuchi water as weighed zinc powder is placed in t!he old dewvas usedin anailyziiag tie sibstance, thiis source composing bottle. After the apparatus has of error may be so much duiminishedl that accu- been proved to be tighlit, the bottle whiici coinrate ritislts may still be obtatinled wiithi mate- tainis the carbonate is inclined so that the acid rials cont:iiiml no more than 0.5 per cent of in the test tube iay flow out into the bottle, carbonatet ofi cciu im. In operating with these and, finally, acidt is miade to flow fi'oii tle reearthy materi:ls, tlhe decomposing jar must be tort upon the zinc powder. Wrheni no molre fiee!h s!makein in oirder that carboni, acid may hydrogen is evolved, lift the long tube in tile escape, anl the control experimeni t mwit th te new twvo-necked bottle, out of the liquid, bring miarbleh must e siubjected to the same amount the apmaratus to a comamon teiiperatuire and,of ag'itation. The quantity of carbonic acid mneasure the wvater in tihe beaker as befiore: (F. retainued by the water can, for thaxt rmatter, be Schulze, Zeitsch. caalyf. Chem.., 1.863, 2. determineiel fbr ainy special series of experi- 289j. nients and allowed for, or the carbonic acid may be displaced friom the water by meancs of B. 3lfethod qf L.,lleyer, for determining' hyidrogen. To this enid mix with tile carbonate carbonic acid in mineral waters and in blood. to be amanayhzed a wAeighed quiantity of zinc In order to remiove carbonic acid (antd other powder, eacx granmie of vhich has been fbund gases) from a liquid, Meyer employs a miocificapable, by prievious cxperimentss of' evolving cation of tihe apparatus of Ludwcig based a certain nuimber of c. c. of hIdrogen, when upon tihe principle of' the Torricellian vacuum.n. treated aith chloriyhtric acid On pouring This apparatus may be roughly described as chlorivdric acid fiomi the retort into the de- follows: —A stout glass vessel of about 700 c. c. composing flask the carbonate will first be de- capacity, filled with mercury, is attached to a coimposed before minuch of' the zinic is acted long veirtical tube, also full of mercury, in such upon, so that hydrogen will continue to be set manner that on allowing mercury to flow friomn free in the liquid long after the carbonate has the bottom of the tube a vacuum can be formed been completel y decomposed. If enough zinc be used, the hydrogenm will sweep forward into the collecting jar almost all the carbonic acid i See Setchemow, tJVien. Akad. Bericht., 36. 293 otherwis aebe reScminhoefi, ibid., 41. 589, and Heidehlain, Zeitsc/m. whichm would otherwise have been retained by analyt. Cmen., 1863, 2. 120. CARBONIC ACID. 87 in the vessel. The flask whliich contains the receive the water which is expelled from the mineral water is connected with the glass ves- flask through the expansion of the liquid by sel by means of a flexible tube closed -with a heat, and also fbr the reception of the tartaric screw compressor, so that on opening the latter acid which is added to expel the combined the gases contained in the water will be given carbonic acid. After the water flask has been. off to supply the vacuum. As soon as any connected with the glass vessel, a vacuum es-,considerable quantity of gas has escaped from tablished in the latter, and the compression the water the compression cock is again closed cock opened, the greater part of the carbonic and the gas forced over into a collecting tube, acid escapes from the water immediately with standing in a pneumatic trough beside the vac- considerable violence. As soon as ille filst uumn jar, byr pouring mercury into the latter. portions of the escaped gas have been forced The vacuum is then re-established as before, over into the collecting tube the flaslk is heated and the compression cock again opened so that on a water bath, gently at first, but afterwarclds a new quantity of carbonic acid may exhale more strongly, until no more gas is evolved from the water; the glass vessel is thus alter- from the water. The collecting tube is then nately filled and emptied of mercury as long as removed'and a solution of tartaric acid, which any gas continues to escape from the water. has previously been freed from air by exposure The flask which contains the water is heated in the vacuum apparatus, is drawn into the after a while to falcilitate the escape of carbonic large glass vessel tllough the delivery tube acid, and at a certain stage of the process tar- which connects this vessel with the collecting taric acid is added to the water, in order to tube and pneumatic trough. By opening the expel any carbonic acid which mnay have been comlpression cock of the water flask the tartaric previously held in combination by a base. acid is then adclllitted to the water, and the last The proportion of carbonic acid in the gas portions of the carbonic acid are thereby exthus set free is then determi-nied by the usual pelled. (Lothar Meyer, Zeitsch. aznlyt. C'hel,., gasoiletric method described under Hydrate of 1863, 2. 237). Potassium. For details of the method employed for col- C. Method of E. Dietrich. Applicable to lecting and( analyzing the blood of animals the the determination of carbonic acid in cements, reader is referred to the article of' Heidenhain bone-black, precipitates and mIinerls. (Zeitsch. azlyt. Clhem., 1863, 2. 122). With The apparatus required conlsists of a slmall, mineral waters Meyer proceeds as f-bllows:- wie-niouthed glass bottle, in which to generate The water is collected at the spring in ordi- the carbonic acid, and two narrow glass tubes, nary bolt-heads of about 1 litre capacity, whose by means of which to measure the gas. The throats have been drawn out to the width of two tubes are of' the same length and caliber, about 1 c. in. The flasks may be closed se- and are held in a vertical position upon a table curely with thick caoutchouc tubing which has by means of appropriate rods and clamps. been freed from adhering sulphur by boiling Each of the tubes is capable of holding a little with so(da lye or sulphydrate of anlmonilum, more than 100 c. c. The tube nearest the leand afterwards soaked in fat upon a water composing bottle (called the measuring trube) bath. The walls of this tubing should be at is graduated to fifths of cubic celntimetres, but least 5 m. mi. thick; after the treatlnent with the other tube has no graduations, it is a fat the tubing should be washed first -with al- mere pressure tube. Both tubes are ceentented cohol, then with water, and dried. - Before at the bottom into iron caps, p rovided with fbrcing the tubing over the neck of the flask short, projecting, verticalpipes, to whlich caoutthe latter should be smeared with a hot mlix- chouc tubiniig may be tied. The top of the ture of fat and unvulcanized caoutchouc. The graduated tube is in like manner cclentcdc rubber tube is then tied tightly to the glass with shellac into an iron cap which has a with fine, soft iron wire, and the flask sunk lateral as well as a vertical prqjection for in the water of the spring. When a sufficient the attachment of caoutchouc tubes. But the quantity of water has run into the flask, the top of the pressure tulbe is left open, or only caoutchouc tube is closed under water with a partially closed with a perfoiatedl cork. The screw compressor, a glass rod smeared with measuring tube is fastened to its supports in a the mixture of fat and rubber is pushed into fixed and imlunovable position, but the pressure the outer end of the tube and the tube is tied tube is so arranged that it may be readily to the rod with wire, as before. In- flasks thus pushed up or down in a vertical plane. closed, milneral water can be kept for days or The two glass tubes are connected at the weeks without loss of gas. In order to bottom by mreails of a caoutchouc tube which attach one of these flasks to the vacuum appar- must be as longo as either of the glass tubes. atus, take out the glass rod and put in its place To free the vulcanized rubber firom sulphur, a bulb-tube about 10 c. m. long, of 20 or 30 c. c. boil it for some time in moderately dilute potcapacity, attach a second caoutchouc connector ash lye. A perforated caoutchouc stopper, to the other end of the bulb-tube, and tie it carryling a straight glass tube, is fitted to the to the orifice of the glass vessel in which th!e decomlposing bottle, and the bottle is put into vacuum is produced. This bulb-tube serves to connection with the measuring tube by means 88 CARBONIC ACID. of a caoutchouc tube, one end of which is tied 4. 145) has drawn up tables of corrections to to the pipe in the stopper of the bottle, and the be applied in compensation for this source of other end to the lateral projection in the iron error. - As soon as the evolution of carcap of the measuring tube. A short piece of bonic acid ceases, the decomposing bottle should caoutchouc tubing, carrying a screw compressor, be placed in water of the same temperature as is attached to the vertical pipe at the top of that of the air of the apartment, in order to the measuring tube, so that the tube may be remove the heat developed by the chemical opened or-closed at will by turning the screw. action. Or, better, the decomposing bottle Enough qpicksilver is poured into the ver- may be kept in water during the course of the tical tubes to fill one of them completely, to- experiment, and, if need be, the gas may be gether with the caoutchouc pipe which con- made to flow through a leaden worm sunk in nects the two tubes. To prove the tightness water with the decomposing bottle. - In of the apparatus, place the stopper in the dle- case more than 100 c. c. of carbonic acid are composing bottle, open the screw compressor to be given off from the sample of carbonate at the top of the measuring tube, push up the under examination, the gas must be measured pressure tube until the mercury has risen tothe by portions. To this end, pour the chlorhytop or 0~ mark of' the graduated scale, and dric acid, little by little, upon the carbonate, clamp the pressure tube in that position. Then in such manner that the evolution of gas may close the screw compressor on the graduated cease before the measuring tube is completely tube and lower the pressure tube as far as pos- filled with it. Then slip a screw compressor sible. The column of mercury in the measur- over the rubber tube which connects the deing tube will instantly fall a little when the composing bottle with the measuring tube, pressure is thus removed from it. but if the close the tube tightly, and measure the gas apparatus be tight the level of the mercury which has been evolved; discharge the measwill afterwards remain unchanged as long as ured gas, refill the measuring tube with merthe temperature and the pressure of the air cury, loosen the compressor attached to the remain constant. tube of the decomnposing flask, and pour another In an actual analysis, place a weighed quan- portion of chlorhydric acid upon the carbonate tity of the carbonate to be examined in the which still remains undecomposed. When a decomposing bottle, together with a small glass large quantity of' carbonic acid is developed tube or bottle two-thirds filled with dilute in this way, the error depending upon the abchlorhydric acid. Cork the bottle tightly, fill sorption of gas by the liquid in the decomposthe measuring tube with mercury to the zero ing bottle may be readily allowed for. It will mark, close the screw compressor, lower the be sufficient to measure the chlorhydric acid pressure tube and tip the decomposing bhot- used, to estimate how much carbonic acid tle so that the acid in the tube within it may would be absorbed by a similar volume of water flow upon the carbonate. When the evolution at the temperature in question, and add this of gas has ceased, and all parts of the appara- volume to the mneasuredvolume of the evolved tus have again acquired a common tempera- gas. Up to 300 or 400 c. c. the errors inciture, lift the pressure tube until the mercury dental to measuring do not materially affect stands at the same level in it and in the meas- the accuracy of the results. (E. Dietrich, uring tube, and note the volume of gas in the Zeztsch. analyt. Chem., 1864, 3. 162 and figure). latter. Correct the observed volume for temperature, barometric pressure, and the tension D. Mlethod qf Rumpf. Seeking to simplify of aqueous vapor, and calculate the weight of the method of Dietrich, Rumpf (Zeitsch. analyt. the corrected volume from the known sp. grs. Chem., 1867, 6. 398) has constructed an appaof carbonic acid and air, For Dietrich's table, ratus which may readily be made from mategiving the weights of cubic centimetres of CO2 rials to be fbund in every laboratory. This under barometric pressures ranging from 720 apparatus consists simply of an ordinary Mohr's to 770 m. m., at temperatures from 10~ to 25~, burette of from 30 to 50 c. c. capacity, a hysee Zeitsch. analyt. Cheom., 1865, 4. 142. dromneter jar, test tube, and small, wideThe chief source of error to be taken into mouthed bottle, together with a cork and conaccount depends upon the fact that a consid- nectors of glass and rubber tubing. The carerable quantity of carbonic acid remains dis- bonate to be analvyzed is decomposed in the solved in the liquid in the decomposing bottle. bottle and the evolved gas measured in the The quantity of carbonic acid thus dissolved is burette which is inverted for the purpose in found to be greater in proportion as the quan- mercury contained in the hydrometer jar. tity of gas evolved is greater. Thus in a case To construct the apparatus, fit a caoutchouc where 92.8 c. c. of carbonic acid gas were de- stopper, having three holes, to the decomposing veloped, 4.6 c. c, of carbonic acid remained bottle; fix a therniometer in the middle hole of dissolved in the liquid in the decomposing bot- the stopper, and a short straight glass tube in tie, while in another case where 0.9 c. c. of gas each of the other holes. To one of' the prowere set free only 0.3 c. c. remained dissolved jecting glass tubes tie a short rubber connector, in the same quantity of liquid. Dietrich (see and close it with a spring clip or screw comZeitsch, analyt. Chem., 1864, 3, 166 and 1865, pressor. To the other projecting tube tie one CARBONIC ACID. 89 end of a thick rubber tube, the other end of its centre there is a well in which the eudiomwhich has been previously tied to the point of eter and pressure tube may be sunk at will. the burette. - Put a weighed quantity of The broader part of the trough is made circuthe carbonate to be analyzed into the decom- lar so that there may be placed in it a tall glass posing bottle together with a short test tube sleeve large enough to envelope both the euditwo-thirds filled with a measured quantity of ometer and the pressure tube. During an exchlorhydric acid. Replace the stopper, open periment this outer sleeve is kept full of water, the spring clip, and sink the burette in the in order that the contents of the eudiometer mercury in the hydrometer jar until the last may be maintained at a constant temperature. division mark upon the burette is level with The opening of the well is 2.5 inches long by the surface of the mercury. Close the spring 1-1 inches broad. One part of the well, devoted clip and tip the bottle so that acid may flow to the pressure tube, is 14 inches deep, measout of the test tube upon the carbonate. When ured from the bottom of the trough, while the the evolution of gas has ceased, take hold of part reserved for the eudiometer has a depth the rubber covered point of the burette, and of 19 inches. The narrower part of the trough, push the latter into the mercury until the sur- not occupied by the water-sleeve has a depresface of the metal is at the same level inside and sion or channel in the middle. This channel without the tube. Read off the number of c. c. is 5 of an inch wide and its depth gradually inof gas in the burette; take the height of the creases from the edge of the trough to 1.75 inch thermometer and barometer and proceed to at the side of the well. (See figure in Journ. calculate the weight of the gas, taking care to London Chem. Soc., 1868, 21. 129). The euallow for the tension of the aqueous vapor con- diometer is similar to that of Bunsen (see his tained in the gas, and for the volume of gas Gasometry), viz., a straight glass tube closed which remains dissolved in the liquid in the at the top, some 500 or 600 millim. long by 20 decomposing bottle. (Compare the description millim. in diameter. It is provided with platof Dietrich's method, above). inum wires at the top and graduated and calibrated according to Bunsen's plan. The "presE. Method of Scheibler. Employed exten- sure tube" is simply a straight glass tube of sively in Germany by sugar manufacturers, for about the same diameter as the eudiometer and estimating the proportion of carbonate of cal- closed at the top. Its purpose is to hold a concium in bone-black. The process is applicable stant quantity of air to be used as a standard to the analysis of any carbonate which can be of comparison in measuring any gas in the eudecomposed by cold chlorhydric acid, is easy diometer. To prepare the pressure tube for of' execution and yields very accurate results. use, a very small drop of water is placed at The rather elaborate apparatus required may the closed end, and mercury then poured into be obtained of the dealers in German chemi- the tribe until most of the air has been discal wares. For a figure and detailed descrip- placed. The tube is then inverted in the mertion of it see Fresenius's Quantitative Analysis, cury trough and the height of the mercury in London, 1865, p. 712, or either of the later the tube marked off once for all. After this editions. The method here alluded to must has been done, any effect which the rise or fall not be confounded with another process devised of either barometer or thermometer would proby Scheibler for estimating carbonic acid in a duce on the bulk of the air in the tube may be mixture of gases by absorption in potash lye. exactly counteracted by raising or lowering (See Hydrate of Potassium). the tube in the mercury-trough until the mercury again comes to the mark. Before filling F. Method of Russell. Applicable to the the eudiometer with mercury a drop of water determination of carbonic acid in carbonates, is placed in it so that the gas to be measured and to the valuation of oxides, such as bin- may always be saturated with aqueous vapor. oxid e of manganese, which give off carbonic Any alteration of temperature in the water of acid when mixed with oxalic and sulphuric the sleeve that surrounds the tubes which may acids. - The apparatus required differs occur during an analysis will not affect the but little from that devised by Williamson & accuracy of the measurements, provided both Russell for the analysis of gases (see Proceed- tubes have undergone the same change of temings of London Royal Soc., 9. 218; further, perature. To ensure an even temperature, the Journ. London Chem. Soc., 1868, 21. 128). water in the sleeve is agitated from time to The latter consists simply of a tubular pneu- time with a wooden stirrer. Before proceedmatic trough, a eudiometer tube and a pres- ing to measure a gas in the eudiometer the sure tube with clamp-rods to hold the tubes in gas is brought to exactly the same tension as place. that of the standard volume of air in the presAccording to Russell, the pneumatic trough sure tube. To do this the two tubes are may be made of sheet gutta percha half an placed side by side and the eudiometer is inch thick. Seen from above this trough is a raised or lowered until the column of mercury pear-shaped box, 6- inches long, in the clear, within it is of the same height as that which by 35 inches wide at the broadest part. The is required to bring the air in the pressure tube sides of the trough are 3.5 inches high, and at to the original volume. For details relating to 90 CARBONIC ACID. the management of the apparatus, see William- this position by means of a rubber ring slipped son & Russell's paper in Jotrn. London Crenz. over the claump-rod which holds the mleasuring Soc., [2.] 2. 238. tube in place. As soon as the flask and its For estimating carbonic acid or any other contents have acquired the temperature of the gas by measurement, the eudiolneter above surrounding water, proceed to measure the described is replaced by a somevhat larger volume of air in the flask and tube, as follows:gracuated tube. This "measuring tube" may Lower the measuring tube into the well until be 29 inches lonlg and rather more than 0.75 the column of mercury in the tube is of the inch in internal diameter. At the top it is same height as that in the pressure tube, and drawn out to a comparatively narrow tube, note the volume of gas in the measuring tube. which is bent at a riglht angle and left open. This reading gives the amount of air in the The bent part is about half an inch long. A apparatus before any of the gas to be estimated piece of caoutchouc tubing 3.5 inches long is has been evolved. Again elevate the Ineasurpushdd over the projecting bent tube as far as ing tube so that the flask may be brought outit will go, then bound tightly to the glass and side the sleeve, and tip the flask so that the incemented all around with marine glue. The greclients within it may be ilixed and macde to glue is applied as hot as possible so that it may react upon one another. The flask may be adhere firmly to the glass and make a perfect heated at this stage if needc be. A second joint. The rubber tubing' should be very thick, measurement after the reaction in the flask is the outside diamleter being as much as half an completed gives the volume of gas produced. inch, while the bore of the tube is only 1 or 6 To prevent the substances in the flask fiom of an inch. The inside of the tube should be coming in contact out of season, one of tlhem well vulcanized, but the rest of the tube only is placecd in a small tube, which is lowered into slightly so. tile flask in the usual way, and care is taken The carbonate of calcium and acid, or other not to tip the flask prematurely. materials from which the gas is to be generated, Precautions. To avoid leakag'e the rubber may be placed in a small generating flask macde tube whicll connects the flask with the measby blowing a bulb at the end of a glass tube. uring tube must be slightly wetted. So long The diaimeter of tlhe (lass tube should be such as this joint is kept wet it reniains perfeetly that the rubber tube above described will just tight, but if it become dry and there is a hlieh fit into it. The rubber tube thus forms a sort column of mercury in the tube it will probably of stopper to the flask and connects it in the leak. In order to ensure the presence of moissimplest way with the uneasuring tube. The ture, a piece of wickyarn is wvound round the manipulations are very simple. A drop of joining of' the flask tand rubber tube and the water is placed in the measuring tube and the ends of the yarn allowved to dip into the water latter, xith the flexible tube attached to it, is of the sleve. It has been proved, by direct put in its position within the water sleeve and experiment, that the varying amount of' bending clamped, just as a eudio_!'eter would be. To which rubber tubing of the prescribed thickfill the tube with mercury, attach a piece of ness will undergo wh0len the flask is sunk in the strong glass tubing, about 2 feet long and sleeve does not appreciably alter the volume slightly tapering at one end, to the flexible of air in the leasuliiiin tube. tube and sink the measuring tube as far as it It is important t that the caoutchouc tube will go into the well of the trough. It is not be as short as possible lest, in determiningi carnecessary that the well be deep enough to re- bonic acid, a considerable error arise fi-omn the ceive the wilhole of the tube, for by attaching absorption of' the gas by the caoutchouc. In temllporarily a thick rubber tube to the end of one experiment in which the carbonic acid the glass tube which reaches above the top of from 0.124 rin. of marble was collected in a the sleeve and applying the mouth to the rub- glass tube, to the topt of which was attached ber tube, it is easy to suck up the mercury to a a piece of the thick rubber tubingl some 8 or 9 height of several inches. When the mercury inches long, it was found that although there has thus been drawn up to within 2 or 3 ihclies was some air in the tube, as well as the carof the top of the mercury tube, pinch the rub- bonic acid which occupied 201.71 divisions, ber tube for a moment with thumb and finger, the gas at tile end of.one hour had diminishedl and plug it at the end with a bit of glass rod. 7. 7 divisions, at the end of 2 hours, 9.9 divisElevate the measuring tube so that the flexible ions, 3 hours, 11.5 divs., 4 hours, 13.3 divs., tube attached to it shall project above the top and by the next day, 30.3 divisions. With a of' the sleeve, and close this flexible tube with short piece of' the rubber tubing. such as that a screw compressor. Withdraw the thick glass above described, the amount of gas which distube filom the flexible tube, insert the end of appears is about 0.1 of a division of the tube the latter into the neck of the generatinlg flask, every five ndnutes. - In an ordinary gas and loosen the screw compressor so that the analysis it is sufficient if we know the relative flask and the measuring tube may communi- volumes of gas at the different stages of the cate freely one with the other. Bend the flex- analysis; but for the present purpose the necible tube so that the flask shall be immersed in essary data for converting these. relative volthe water of the sleeve, and fksten the flask in unmes into absolute volumes, and for ascertain CARBONIC ACID. 91 ing their weight, must be determined. The (letermined as Chloride of Silver, by titration, measuring tube is calibrated in the usual way, and firom the weight of chlorine found, the and a table of volumes drawn up similar to one equivalent quantity of metal in the residue, for an ordinary eudiometer. I'le volunme of and of carbonic acid in the substance analyzed, mercury which has been used in the calibra- may be calculated. According to AMlohr (Tition is weighed and the temperature noted. trit'methode, 1855, 2. 58) the last named proThe value of one volume in the table, expressed cess may be usefully applied in analyzing alkain cubic centimetres, is then determined by the line carbonates which contain chlorides, and formula:- mixtures of carbonates of sodium and chloride w x (1 + 0.0001a15 r) of sodium in mineral waters. The chlorine 13.o16i V proper to the solution is first determined by in which qw is the weight and t the temperature titration with nitrate of silver, the mixture is of the constant quantity of merculry which oc- then supersaturated with chlorhydric acid, cupies the volume V, used as thfe standard in evaporated to dryness, and again titrated to the calibration. 0.0001815 is taLen as the co- estimate the chlorine which has taken the place efficient of expansion of mercur:-, and 13.596 of the carbonic acid. as the specific gravity of that mc -il at 0~ C. It is necessary, moreover, to knov, the tempera- 4. By absorbing the gas in an alkali. [Comture and pressure at which thin measurement pare Principle Ij. This method is convenient has been inade, in order to find the weight of of execution, and yields exceedingly accurate the gas. When the measuremeats are made results. It is, perhaps, better suited than either by Ineans of a pressure tube, it, is only neces- of the others for the ordinary requirements of sary to ascertain once for all wnes-t' is the tern- the laboratory. The process may be conducted perature and pressure, at the same moment, of as follows:-Place a flask of about 300 c. c. the air in the upper part of the pressure tube; capacity, on a piece of wire gauze laid upon a the mercury standing exactly at the mark triilod or rino-stand above a lamp, and fit to which indicates the constant volume. W7hen the flask a caoutclhouc stopper provided with the weight of' dry gas occupying: one tabular two perforations. To one of the holes in the volume of the measuring tube has once been stopper fit a glass tube something inmore than calculated from these data, it is only necessary twice as long as the flask is high; bend the to multiply any volume of that enls, which may tube twice, near the middle, into the form of be measured in the tube, by this constant, in an S, in such manner that the bent portion ordler to obtain the weight of' the gas. may' be wholly outside the cork, while enough It has been found in practice'1iat the error of the tube is left straight, at either end, to which might arise from the rete ntion of car- reach allllost to the bottom of the flask; blow bonic acid, dissolved in the liq:..i of the flask, a smalll bulb upon the tube at the middle of mnav be avoided alnost entirel by employing the bent portion, i. e., at the centre of' the S. only a slight excess of the di'iJtte acil. The To the other hole in the stopper fit a short process is liable to another souurce of error, in- glass tube, bent at a right angle, to serve as a asmuch as the tension of the gns in the incas- gas-deli very tube. It is well to blow a bulb uring tube may be slightly a.ltered when on the upright part of the -delivery tube, outa little of the acid is carried:;y-er into the side the cork, and to grind off the lower extube. But it is found, whet operating with tremnity obliquely so that drops of water may a flask of about 120 c. c. (capacity, that fall frion it. Bring the outer end of the delivthe alteration of tension is ve,,: slilht unless err tube into line with a series of absorption the reaction in the flask has been unusually tubes arranoged as follows: —lst, a bulbed Uviolent. It is well, for that matter, to place a tube full of' chloride of calciumn; 2d, a very loose plug of cotton-wool in the neck of the small U-tube filled with fratgmlents of glass flask. moistened with 8 or 10 drops of concentrated The process yields accurate results, is rapidly sulphuric acid and loosely pluggued with asbesexecuted, and requires only small quantities of tos at either end; 3(d, a U-tube cllaroed with material. (Russell, Jomrr. Londoa Chem. Sec., soda-lime and a little chloride of calciumn in 1868, 21. 310). the ordinary way, tand 4th, a U-tube, the inner limb of which is chalred with chloride of cal3. By lnoting th7e weight of the residue, or by cium, and the outer liinb with soda-line or analyzing the residue. Dissolve the carbonate hydrate of potassium. The purpose of thislast in a slight excess of chlorhydric acid, or other tube is merely to protect the 3d tube from the suitable acid, evaporate the solution to dryness, moisture and carblonic acid of the air; to the weigh the residue, and calculate the weight of outer end of it attach a piece of rubber tubing carbonic acid which is equivalent to it. The 5 or 6 inches long. The Ist tube, which should method is applicable only to the analysis of be comparatively large, is a mere drying tube carbonates fiee from impurities, and capable of and is never weighed. The 2d and 3d tubes formling fixed and definite chlorides, or other serve to absorb the carbonic acid, and are salts. Instead of weighing the dry chloride, weighed together. The purpose of the sulphuthe amount of chlorine contained in it may be ric acid in the second tube is merely to show 92 CARBON IC ACID. the rate of flow of the carbonic acid, but since rated with anhydrous Sulphate of Copper, and sulphuric acid absorbs a certain amount of car- proceed as before. bonic acid, this tube has to be weighed with The 2d tube, charged with sulphuric acid, the others. may be used over and over again for many After the tubes 2 and 3 have been weighed analyses. So, too, the soda-lime tube may be and tightly connected with the other tubes, used repeatedly, subject to the usual rules place a weighed quantity of the substance to which apply to this substance. When large be analyzed in the flask, moisten it with water, quantities of carbonic acid are to be absorbed cork the flask, and connect its delivery tube the soda-lime tube may be replaced by Geisswith the 1st tube of the series above described. ler's potash bulbs, or even by Liebig's bulbs, By means of a caoutchouc connector attach a if the evolution of' gas be carefully regulated. small funnel to the top of the S-tube in the (Kolbe, A nnal. Chem. und Pharm., 119. 130, flask, and pour through it a small quantity of and Fresenius, Quantitative Analysis, p. 300). mercury to fill the lowermost part of the bend, beneath the bulb, in the S-tube. Then fill 5. By absorbing the gas with an alkaline earth. the funnel and tube with a mixture of equal The carbonic acid generated in the apparatus volumes of strong nitric acid and water, and described above, paragraph 4, might, of course, suck gently through the caoutchouc tube at be collected in the form of Carbonate of Bathe end of the series of absorption tubes, until rium or Carbonate of Calcium. As a general a little of the acid is drawn past the mercury rule, however, the absorption by soda-lime is into the flask. The bulb in the S-tube pre- greatly to be preferred. vents the mercury from passing over into the flask with the acid. Principle III. Power of changing the color The carbonic acid set free by the nitric acid of blue litmus to violet. is dried by the chloride of calcium in the 1st Application. Rough estimation of the free U-tube, and its rate of flow is made manifest carbonic acid in mineral waters. by the bubbles which pass through the sulphu- Method. Prepare a standard solution of diric acid at the bottom of the second U-tube. lute sulphuric acid (see Acidimetry) of such As soon as the evolution of gas slackens, suck strength that 1 c. c. of it shall contain 10 milover new portions of the nitric acid into the ligrammes of SO8; also a solution of litmus, flask until the carbonate has been completely by digesting a quantity of the solid in an equal decomposed. If need be, the flask may be weight of cold water. There is required also, heated gently throughout the process. When a concentrated solution of caustic soda containno more gas is evolved wash out the S-tube by ing some carbonic acid, such as may be found filling it two or three times with hot water and upon the shelves of any laboratory. sucking the water into the flask. Remove the Measure out about 450 c. c. of distilled funnel from the top of the S-tube and replace water, add to it 1.5 c. c. of the litmus solution it with a tube filled with soda-lime or hydrate and 5 c. c. of the caustic soda. Dilute the of potassium; then heat the contents of the mixture with water to the volume of 500 c. c., flask to gentle boiling until the projecting por- take out with a pipette 3 several portions of tion of the 1st chloride of calcium tube be- 100 c. c. each, of the liquid, and pour them into comes hot on the side nearest the flask. Ex- three beakers. Place the beakers on a white tinguish the lamp and, by means of an aspira- ground in strong daylight, and pour the stantor fastened to the end of the 4th tube, draw dard acid from a burette into each beaker in as much air through the apparatus as will succession, until its contents appear distinctly amount to at least six times the volume of violet colored. Towards the close of each opthe flask. After the apparatus has become eration it is necessary to wait one or two mincold, weigh the 2d and 3d U-tubes. The dif- utes after each addition of acid, in order that ference between this second weight of the the change of color, when it does occur, may tubes and the weight before the operation, become distinctly visible. The experiment in gives the amount of carbonic acid in the sub- the 1st beaker will give an approximately corstance analyzed. - The other constituents rect result, so that in the second and third of the substance may be determined in the trials the operator will be able to hit the point nitric acid solution which is left in the flask. of coloration with tolerable accuracy. Select By'using a definite quantity of standard acid the most accurate of the three experiments, to and titrating the excess with a standard alkali, the exclusion of the other two, multiply by 5 as explained above, in paragraph 1, after the the number of c. c. of acid consumed in that carbonic acid has been expelled, it is easy, in case, and record the product of this multiplimany cases, to determine the quantity of' the cation as the quantity of acid corresponding base with which the carbonic acid was com- to 5 c. c. of the soda solution. bined. In cases where chlorhydric acid is to be It is to be observed that the color of blue preferred to nitric acid for dissolving the sub- litmus is not changed to violet by bicarbonate stance, fill one limb of the 1st chloride of cal- of sodium, but only by free carbonic acid; cium tube,-that which is farthest from the hence, when dilute sulphuric acid is cautiously flask, —with fragments of pumice stone satu- added to a solution containing carbonate of CARBONATES. 93 sodium, no violet coloration will appear until a large number of experiments are to be made. the sodium compound has all been converted (Zeitsch. analyt. Chem., 1868, 7. 1.51. For a into sulphate and bicarbonate, and some car- description of' the apparatus employed, see bonic acid has actuallv been set free from the Tyndall's Heat a 1M~ode of MlIotion). latter by the addition of a drop of sulphuric Carbonate of Ammonium. acid in excess. It will be noticed, also, that Principle I. Power of neutralizing acids. since all the carbonic acid is in the state of a Application. Estimation of carbonate of ambicarbonate at the close of the neutralization, monium in commercial samples. two molecules of this acid must be reckoned as Method. See Alkalilnetry. Mohr (Titrirequivalent to, or as replacing, one molecule of methode, 1855, 1. 63) found that the results obSO3. Hence, if 1 c. c.. of the standard sul- tained by supersaturating carbonate of ammophuric acid contains 10 milligrinrms. of SO3, the nium with oxalic acid and titrating the excess c. c. will correspond to 11 milligrms. of CO2. of the latter with caustic soda, were liable to To perform an analysis, add 5 c. c. of the wider variations than those of most other alkasoda solution, or 10 c. c. if need be, to 450 or limetric processes. After the expulsion of the 500 c. c. of the mineral water under exam- carbonic acid the hot acid liquor must be ination, and mix the two liquids. Without cooled completely before adding any of the heeding any turbidity which may appear standard caustic soda, lest some ammonia be in the liquor, measure out as before three set free by the latter. separate portions of 100 c. c. each, add Principle II. Volatility. to each portion 4 drops of the litmus so- Application. Estimation of carbonates in lution, and pour in the standard sulphuric natural waters. acid until the liquid exhibits a violet tint. Method. Add to 200 c. c. of the filtered More care and attention should be given water about 0.5 grin. of chloride of ammonium, to the experiment upon the second portion of distill off half the solution and receive the disliquor than to the first, and still more to the tillate in 10 c. c. of very dilute standard sulphuthird than to. the second. Choose the best of ric acid. Boil the mixture of distillate and the three experiments, as before; subtract the acid to expel carbonic acid gas, then allow it number of c. c. of acid required to produce to cool, and determine how much of the stanthe violet coloration in the mixture of mineral dard acid still remains free, by titrating with water and soda, from the amount of acid which weak standard soda (see Alkalimetry, and was required to produce the coloration with above). The process is said to yield good rethe soda alone, and multiply the difference by sults. (Chevalet, Bull. Chem. Soc. Parigs 0.011 (the value of the standard acid in terms 1868, p. 90). of CO2) in order to obtain the weight of the Carbonate of ammonium is often used as a carbonic acid in grammes. precipitant, solvent and decomposer of sundry In most cases the quantity of mineral water metallic carbonates. It is used also to convert taken had better be measured after the ad- bisulphates of the alkalies to neutral salts. To mixture of the soda, in order to avoid losing be fit for use as a reagent it should leave no much carbonic acid. If the sample of water residue when heated in a platinum dish. to be examined is contained in a bottle, cool Carbonate of Ammonium and it to about 40, remove the stopper quickly, of Magnesium., pour out a little of the water, and add the See Carbonate of Magnesium nl'WtfA*jb soda-to the rest. - The process is of value nium. fbr some purposes, but requires a practised eye. Carbonate of Bari urt (Kersting, Annal. Chem. und Pharm., 94. Principle I. Fixity when noktm,~ ngby 112). heated. Application. Estimation of barium in salts Principle IV. Power of absorbing the heat with organic acids. which radiates from ignited carbonic acid Method. Heat the salt carefully in a covered gas. platinum crucible until no more fumes are Tyndall has observed that though carbonic evolved. Then take off the lid, lay it fiat upon acid gas is one of the weakest absorbents of one side of the triangle which supports the the heat which radiates from a glowing solid, crucible, and lay the crucible fiat, or obliquely it has, on the contrary, a remarkable power'of upon its side with the open end resting on one absorbing the heat radiated from a flame of edge of the cover. Ignite the crucible in this burning carbonic oxide. - The fact. not position until the carbon is all consumed and only furnishes a delicate qualitative test of the the residue has become perfectly white. Since presence of carbonic acid in a mixture of a portion of the carbonate of barium is apt to gases, but has been successfully applied to the be reduced to the condition of oxide by the estimation of carbonic acid in air expired from, ignition in contact with carbon, the cold resithe lungs. It is not improbable that the pro- dumcmust be moistened with a concentrated socess may be found more accurate and conve- lution of carbonate of ammonium, in order to nient than any other for determining the pro- reconvert the oxide into carbonate. After addportion of carbonic acid in air, in cases where ing the carbonate of ammonium evaporate the 94 CARBONATE OF BARIUM. mixture to dryness on a water bath, heat the But if only one of the alkalies were present, dry residue moderately, cool, and weigh. Corn- the barium would always be thrown down as pare Carbonate of Calcium. - A certain Sulphate of Barium, and the alkali weighed as quantity of the substance is almost always a sulphate. -- The process finds applicalost during the ignition, from fine particles of tion, also, in cases where a mixture of BIa, Sr matter being carried away mechanically by and Ca is to be separated fioml K and iNa, or the gaseous products of the distillation. This from K, Na and Mg. The precipitation of the source of error, however, is the less considera- carbonates of tlhe three metals of the alkalile ble in proportionas the crucible is heated more earths is effiectacd in precisely the samne way as slowly. With proper care the process yields if only barium were present. Chloride of A1satisfactory results. monium is added to keep up magnesiunm in Properties. Carbonate of barium is unalter- case any of that metal is contained in the subble in the air, even wvhen heated to redness. stance to be ainalyzed. But since this chloride In the intense heat of a forge, however, or blast of ammonium prevents the precipitation of furnace, it slowly gives up the whole of its car- some barium and calcium, the filtrate from the bonic acid (Abich, Pogygendorl's Annalen, 1831, precipitated ceibonates must be subjected to 23. pp. 308, 314). The presence of aqueous fiurther treatment as follows:-Add to the filvapor favors the escape of the carbonic acid. trate a smlall qutantity of dilute sulphuric acid, The composition of the salt is as follows: — no more than 3 or 4 drops, together with a few Ba... 137... 77.69 drops of a so;i:,tion of' oxalate of ammonium CO3.. 0... 22.31 and let the mixture stand 12 hours in a warm 19i 100.00 place. A mixed precipitate of sulphate of hbaPrinciple II. Sparing solubility in water. rium (and strontium) and oxalate of calcium Applicatiorns. The process may be employed will fall. Collect this precipitate on a small for estimating barium in all barium salts which filter and treat it with dilute chlorhydric acid. are soluble in water, but is rarely used for this The oxalate of calciun will dsole, tooether purpose excepting in those cases where the es- with a little oxalate of magnesiui which is timation of the metal as Sulphate of Barium sometimes tlru-rn down with it, while the sulwould be inadmissible. It is el.lployed also for phate of bariuml (and strontium) is left as an separating IBa from Ii, Na, Mg, Mn, etc., and iinsoluble residue, upon the paper. To recover for estimating carbonic acid. the magnesimo- just mentioned, saturate the bchlorhydric acit filtrate with ammnonia-water, liIethods. allow the re-! i: cipitated oxalate of calcium to Estimation of Barium in solutions of its settle, filter,;Inrd add the filtrate to the salts. Mix the moderately dilute solution mixture of' ma-gnesium and alkalies. Solnewith ammonia-water in slight excess, add the times a little il oluble carbonate of imagnesium carbonate of ammonium as long as a precipi- goes down wit;. thle carbonate of barium, etc.; tate falls, and leave the mixture at rest for 12 it may be reco- ered during the process of sephours in a warm place. Collect the precipitate arating these c-. ments. upon a filter, wvash it with water, to which a T7o separcate?-'otassiumfromn a mixture of Ba, little ammonia lhas been added, then dry, ig- Ca and Mfg, in a solution free fiom ammoniuml nite, and weigh. See Principle I. Since salts, heat the liquid to strong boilimio and add carbonate of barium is not absolutely insoluble to it a solutioli of' carbonate of sodiuml, drop in ordinary water, and is soluble to no incon- by drop, as loinm1 as any precipita te falls. Considerable extent in aqueous solutions of' anlmo- tinue to boil until tlhe voluminous precipitate nium salts, the results obtained by this mIethod has become coiipmact and granular, it is easy are usually a little lower than the truth. Care to wvash out all the potassium fio, the preceipimust always be taken to keep the proportion of tate if the boiling has been continued long. chloride, nitrate or other salt of amnmoninmll in enough. But the method will be found, in the solution as small as possible. mlost cases, to be infbrior to that of precipitatIt is to be observed that carbonate of bariumr ing the potalssit1t directly as Chloroplatinate of cannot be precipitated fiom solutions which Potassium. (Stohmann, Zeitschl. atnalyt. C/l ei., contain a citrate or mietaphosphate of either of 1866, 5. 307). the alkali metals. Selparation o/; Bca fom Jz iz. See Carbonate Separation of Ba from K, NVa and 3Iyg. The of Manganese. process is employed in certain cases fIor sepa- Ilndirect.epao'ation of Ba firom Ca Cld Sr'. rating barium fironi potassium, sodium and See, Carl:onic i cid (Volatility of, — methods mnagnesium, though it is, on the whole, less ac- by simple ignlition, and by ignition with an curate anii convenient than the method de- acid salt). scribed under Sullphate of Barium. It is em- Estimatioa oj Carbonic Aicid. ployed, for example, whlen barliurl is to be sep- 1. Absorptioon in bacryta-water. arated from a mixture of' both potassiumlland Many chemi:-e - have estimated carbonic acid sodium, since the inixture of' alkalies in the by absorbinrg tIhe gas in baryta-water and filtrate from carbonate of' barium can easily be weigliing the p:ecipitated carbonate, in the manconverted into chlorides, and analyzed as such. ner above described. De Saussure in particu CARBONATE OF BARIUM. 95 lar, sought to perfect the process by washing lows:-By means of a perforated cork, fit to a the carbonate of barium with a saturated solu- sufficiently wide-mouthed bottle a large funnel tion of this substance, in place of water, and with wide throat. The rim of the funnel did unquestionably obtain accurate and valu- should be ground so that it can be covered able results in that way,-as Boussingault and tightly with a glass plate. Fit a cork to the others have done after him. - The modern upper part of the throat of this funnel, perfomethods are as follows:- rate the cork and cut a groove in its side. A. Method of lohlr v. Gilm (TiViea. Akad. Through the hole in the cork thrust the tube.Bericht, 24. 279), employed for estimating the of a second funnel considerably smaller than proportion of carbonic acid in atmospheric air. the first, and place the filter in this inner funBy means of an aspirator of at least 30 litres nel. During the operation of filteringi the capacity, some 60 litres of the air to be anal- large funnel is kept closed as much as possible yzed are slowly drawn through an absorption with a glass plate. Air can of course pass tube containing a solution of hydrate of barium; freely from the bottle into the large funnel the precipitate of carbonate of' barium which through the slit or groove in the inner cork. forms is collected upon a filter out of contact According to observations of A. Mueller with the air, the tube and precipitate are (Zeitsch. analyt. Chem., 1862, 1. pp. 84, 149), washed first with distilled water saturated with this process is open to the objection that filter carbonate of barium, and afterwards with pure paper has the power to absorb colsiderable water which has been recently boiled. The quantities of baryta out of baryta-water, and carbonate- of barium upon the filter and in the to retain it so forcibly that it cannot be washed tube is then dissolved in dilute chlorhydric out. acid, the solution evaporated to dryness, tlfe The precipitated carbonate of barium might residue ignited gently and the amount of chlo- of course be decomposed with an acid in an rine contained in it determined as Chloride of appropriate apparatus, and the Carbonic Acid Silver. Or the amount of barium may be de- weighed'or measured as such, instead of being termined as Sulphate of Barium. Every atom treated as above described, or in addition to of Ba, or every two atoms of C1, fill represent this treatment. a molecule of CO2... lethods of Hcladfeld, of Pettenkofer, and To prepare the absorbent liquid, dissolve of A. M]lueller. See below, under Principle crystallized hydrate of barium in a warm dilute III (Power of neutralizing acids). solution of caustic potash, and filter the mix- 2. Absorption in an ammnoniated solution of ture. Since some carbonate of barium is al- chloride of barium. This method may be eraways precipitated on the addition of the potash ployed in the analysis of mineral waters, air, lye, the clear solution obtained necessarily con- and other gaseous mixtures. It was formerly taiils all the carbonate of barium it is capable sometimes used for estimating carbonic acid of dissolving. - For the absorption tube, set free from carbonates by the action of acids, choose a tube a metre lonllg, and about 15 mi. m. but is now known to be inferior to the methods wide. Draw out the upper end of the tube, described in the preceding paragraphs, and to and at some distance from its lower end bend several of' the methods described under Carthe tube at an angle of 140~-150~. Fix the bonic Acid. tube in such a position that its longer limb Prepare a quantity of an ammnoniated solushall incline at an angle of 8~ or 100 to the tion of chloride of ba-lrium, as follows: —Mix horizontal and fill the tube half' full of the ain aqueous solution of chloride of bariumn with clear baryta-water. By mIleans of a perforated an excess of ammlllonia-water, boil the mixture cork, fit a narrow glass tube into the wider end for a ftiev inutes and filter the hot liquid of the absorption tube, for the admission of air, quickly, in order to remove the carbonate of and connect the other end of the absorption barium formed by carbonic acid contained in tube with the aspirator. It is well to interpose the ammonia-water. After the mixture hlis a couple of little flasks, charged with the once been boiled, take care to protect the baryta-water, between the absorption tube and liquid as much as possible froim contact nwith the aspirator, in order tobe sure that the whole carbonic acid of the air. Pour 50 or 80 c. c. of the carbonic acid has been absorbed from of the clear liquid into a liollt flask of about the air. 300 c. c. capacity, and close the flask tiglltly Since, in passing through the absorption tube, with a caoutchouc stopper. Without removinlg the air is compelled to force its way against a the stopper, weih the -flask tooether with the column of liquid, it is essential that the aspi- barium solution, and pour into the flask enough rater employed should be provided with a small of the mineral water, or other solution of carmanomieter, in order that the volume of air bonic acid to be tested, to nelarly fill it, then may be accurately measured. The height of replace tlhe cork immlediately, shake thle flask, the column of' mercury in the manometer ilust and agaiin weigh it with its contents. The difbe deducted fiorm that observed in the baroin- ferenee between the first and second weighings eter at the time of the experiment. will give the weight of the mineral water For filtering the carbonate of barium, v. taken. Instead of weilghing the mineral water Gill uses a double funnel, arranged as fobl- it may be measured as Ifollows:-MIeasure out 96 CARBONATE OF BARIUM. the 50 or 80 c. c. of ammonio-barium solution the like, the proportion of Carbonic Acid conto be placed in the flask, by means of a pipette tained in it must be specially determined. provided with a rubber ball or soda-lime tube, This method, as well as the analogous method so that no carbonic acid can enter it from the mentioned under Carbonate of Calcium, was lungs; then pour the mineral water into the formerly often employed, but is now held in flask, cork the flask, and scratch the -glass with comparatively slight esteem. The chief oba diamond, or paste upon it a bit of paper, jections to it are fobund in the solubility of carwith shellac, to mark the height of the liquid. bonate of barium in water, the difficulty of obAfter the carbonate of barium has been pre- taining an ammoniated barium solution, in the cipitated and the experiment finished, fill the first place, absolutely free from carbonic acid; flask with water up to the mark, measure the in the liability of this solution to absorb carwater in a graduated cylinder, and subtract bonic acid from the air; in the risk of driving from it the quantity of barium solution in order off some carbonic acid in the form of' carbonto obtain the true volume of the mineral water. ate of ammonium; and in the very decided For another method of measuring the mineral tendency of carbonate of barium to remain water, see Carbonate of Calcium. dissolved in a solution of chloride of ammoPlace the flask in a pan of water, loosen its nium. It may readily happen that appreciable cork, heat the water to boiling, and keep the quantities of carbonate of' barium (or of ca,lflask in the boiling water for an hour or two. cium) may remain dissolved throughout the Then re-cork the flask, allow its contents to analysis in case the proportion of chloride of settle out of contact with the air, and proceed ammonium in the liquid be excessively large to collect the carbonate of' barium on a filter, or the liquid itself be largely diluted with in the manner to be described directly. water. - To guard against the various It is to be observed that although the liquid sources of error, it was customary to operate in the flask usually becomes turbid as soon as at one and the same time upon several different the mineral water is introduced, the mixture portions of the mineral water. - It may must, nevertheless, be heated a long time in here be said that the idea advanced by Kolbe order that all the carbonic acid may be thrown (Handwcerterbuch der Chem., 1. Supplem., p. down, for at temperatures much below boiling 157 ) and recently defended by Fresenius carbonate of barium is soluble to no inconsid- (Zeitsch. analyt. C/hem., 1863, 2. 49 and 1866, erable extent in a solution of chloride of am- 5. 321) that the retention of carbonate of bamonium. The contents of the flask must never rium in solution before boiling, is due to the be heated to actual boiling, however, for in change of carbonic into carbamic acid, is unthat case some of the carbonic acid would supported by any experimental evidence. The escape in the form of carbonate of ammonium. erroneous character of the conception has been Instead of heating the mixture almost to shown by Carius (Annal. Chem. und Pharm., boiling for an hour or two, it may be left dur- 1866, 137. 108) and by old observations of my ing half a day in a place heated to 800 or 90~. own (Amer. Journ. Sci., 1858, 25. 41; and For filtering, provide a funnel with glass Dictionary of Solubilities). cover, quickly decant the clear liquid from the Instead of drying and weighing the precipiflask into the filter, and cover the funnel. tated carbonate of barium, it may be decomNearly fill the flask with warm water, replace posed with an acid and the resulting gas measthe cork, shake the contents of the flask, let ured (see below), or absorbed in soda-lime and the precipitate subside in the flask until the weighed (see below). Or the proportion of filter has become empty, and again decant the carbonic acid may be determined by the Alkatolerably clear liquor from the flask into the limetric method (see also below, Principle III). filter. Wash once more by decantation, then But for determining carbonic acid in that way, transfer the precipitate to the filter, and wash it had better be precipitated in the form of with warm water until the washings no longer Carbonate of Calcium. give any precipitate when tested with nitrate of silver. In case the last portions of the pre- Properties. Precipitated carbonate of bacipitate cannot be rubbed off the flask, dissolve rium is a soft, white powder, soluble in about them in a little dilute chlorhydric acid, mix 48,000 parts of cold water absolutely free from the solution with pure carbonate of sodium, carbonic acid (Bineau), and in 12 or 14,000 and collect the precipitate which forms, upon a of cold water which has been recently boiled small separate filter. Dry, ignite and weigh to expel most of its carbonic acid. It apthe precipitate as in Principle I. pears to be but little if any more soluble in If the substance analyzed contained no other hot than in cold water. The aqueous solution substance besides carbonic acid capable of pre- has a faint alkaline reaction. The solution in cipitating barium or of being precipitated by carbonic acid water is also alkaline. - The ammonia, the weight of the carbonic acid may precipitate is far more readily soluble in neube calculated directly firom that of the carbon- tral solutions of ammonium salts, such as the ate of barium. But if, on the other hand, the chloride or nitrate of ammonium, than in water; precipitate is contaminated with phosphate of but is almost completely insoluble in cold barium, carbonate of calcium, ferric oxide, or water which contains free ammonia and car CARBONATE OF BARIUM. 97 bonate of ammonium; one part of the precipi- to the litre, is to be preferred. Of the stronger tate requiring in that case more than 140,000 baryta-water 1 c. c. will correspond to about of the liquid for its solution. When boiled 3 milligrins. of carbonic acid and 1 c. c. of the with a solution of chloride of ammonium, car- weaker liquid will be equivalent to about 1 bonate of barium is rapidly dissolved with for- milligram. mation of chloride of barium and evolution of To standardize the baryta-water transfer 30 carbonate of ammonium. Carbonate of ba- c. c. of it to a small flask and pour in the stanrium dissolves also to a slight extent in aqueous dard oxalic acid from a burette, little by little, solutions of most of the salts of potassium and until the liquid is just neutralized. After each sodium. In cold water saturated with carbonic addition of the acid, close the flask with the acid, carbonate of barium dissolves in the pro- thumb, and shake the liquid. To determine portion of 1 part to about 600 parts of the the point of neutralization take up a drop of liquid. (Compare Principle I). the liquid upon a glass rod and touch it to a The comparatively large molecular weight piece of delicate turmeric paper. When a as well as the more sparing solubility of car- drop of the liquid ceases to produce a brown bonate of barium are reasons for preferring it ring upon the paper the neutralization is known to carbonate of calcium, but the precipitate is to be complete. In case too many drops of'the apt to be more bulky and less easily filtered oxalic acid happen to be added in this first than that from the calcium salt. trial, the experiment may be repeated as folPrinciple 111. Power of neutralizing acids, lows: -Measure off a second 30 c. c. portion of Applications. Estimation of barium and of the baryta-water, add to it at once as much of carbonic acid. the standard oxalic acid, to within a c. c. or Methods. half a c. c., as was used before; then add the A. Estimation of barium. Similar to the acid drop by drop, and test the liquid on turestimation of calcium described under Carbon- meric paper after each drop, until the neutralate of Calcium. ization is complete. A third experiment should B. Estimation of carbonic acid. agree with the second to 0. 1 c. c. 1. Mlethod of Pettenkofer (Annalen Chemie The details of the actual analysis of a minund Pharm., 2d Supplement volume, page 23). eral water will be found in the description of In this process a definite volume of the air or the lime-water process under Carbonate of Calmineral water to be analyzed is mixed with a cium. measured quantity of baryta-water of known In order to determine the proportion of carstrength; the carbonate of barium which forms bonic acid in air, select a bottle of about 6 is allowed to settle, and a measured portion of litres capacity, having a tightly ground glass the clear supernatant liquid is finally titrated stopper, and accurately determine its capacity. with standard oxalic acid, in order to deter- Dry the bottle thoroughly and by means of a mine how much of the hydrate of barium in pair of bellows fill it with the air to be analthe liquid has remained uncombined with car- yzed. Pour into the bottle 45 c. c. of the dibonic acid. The difference between the amount lute standard baryta-water, and spread the of oxalic acid required to neutralize the un- liquid repeatedly over the inner surface of the combined hydrate of barium and that required glass without shaking the bottle any more than to saturate the baryta-water originally emn- is necessary. In the course of about half an ployed, will be equivalent to the amount of hour the whole of the carbonic acid will be abcarbonic acid in the sample of air or water sorbed. Then pour the turbid liquid from the taken. bottle into a glass cylinder, close the latter seTo prepare the standard oxalic acid, dissolve curely from the air, and leave the liquid at rest 2.8636 grins. of crystallized oxalic acid in until it has become clear. By means of' a piwater, and dilute to the volume of a litre. 1 pette take up 30 c. c. of the clear liquor, transc. c. of tire liquid willcorrespond to 1 milligrm. fer it to a flask, and neutralize with the stanof carbonic acid. dard oxalic acid. Since only 30 c. c. out of The baryta-water employed must be free the original 45 c. c. of baryta-water have been from any trace of caustic potash or caustic employed, the number of' c. c. of oxalic acid soda, for it is impossible to titrate baryta-water required to effect neutralization must be mulwith oxalic acid in presence of an alkaline ox- tiplied by 1.5. Deduct the product from the alate (see Hydrate of Barium). number of c. c. required for 45 c. c. of the The baryta-water should be strong or weak standard baryta-water. The difference will accordingly as there is more.or less carbonic show how much of the hydrate of barium has acid in the air or water to be examined. If been converted into carbonate, and thereby the proportion of carbonic acid is compara- indicate the amount of the carbonic acid. tively large, it is well to use strong baryta- Instead of measuring the air in a bottle as water prepared by dissolving 21 grms. of' crys- above described, it may of course be drawn tallized hydrate of barium to the litre, but through tubes charged with a measured quanin case the quantity of carbonic acid to be de- tity of standard baryta-water, by means of an termined is small, a liquid which contains no aspirator, as described under Principle II, on more than 7 grrms. of the crystallized hydrate p. 95, For Pettenkofer's arrangements for ef7 98 CARBONATE OF BARIUM. fecting the absorption, see his original memoir, liquid as possible into a tared flask which conas cited above. tains a weighed quantity of the standard nitric 2. 3Method of A. Alueller (Zeitschl. an alyt. acid, and again weigh the flask after the addiChlen., 1862, 1. 147, and figure). This method tion of the baryta solution. Finally titrate the is said to be peculiarly well suited for the de- nitric acid still left free in the flask, in order termination of carbonic acid in soils, and, in to estimate the amount of baryta which was general, for the determination of small quan- added to it. The calculation is as follows: — tities of the acid in presence of other volatile If w =the weight of carbonic acid absorbed, substances. It may be employed also for esti- a = the weight of the baryta before the absorption, mating carbonic acid in air, and for experi- c = the weight of that portion of the baryta solution taken for titration after the absorption, ments on fermentation. b the weight of baryta in c, Grind a plate of' glass to fit the top of a d = the sum of the weights of the baryta solution broad glass cylinder or jar about 100 millim. and the carbonate of barium precipitated high and wide. Set a tripod of glass or plati- BaO num in the cylinder, and suspend fiom the tri- G 2c = 3.477, then pod a shallow, conical glass vessel of about 40 c. c. - ac -b d ac - b5d capacity. This smaller or "absorption" vessel must be light, and its mouth, though much nar- It is not practicable to operate with a deterrower than the bottom, must be tolerably wide. mined volume, instead of' a definite weight of The top of this vessel also should be ground the baryta solution, for the weight of the soluand fitted with a glass plate. Some forms of' tion varies constantly during the experiment, ink-stands answer very well for the absorption both from changes of temperature and from vessel. There will be needed also a small the absorption of' more or less aqueous vapor porcelain crucible of about 15 c. c. capacity. by the acid in the jar. Neither can the baryta Prepare standard solutions of nitric acid and solution be filtered after the absorption, fbr of caustic baryta (see Alkalimetry). The ba- filter paper has the power to absorb considerryta solution may be made by mixing a solu- able quantities of baryta, and to abstract it tion of chloride of barium with soda lye. Its from the solution. - A correction may be strength should be reckoned not in terms of applied for the carbonic acid naturally present centimetres, but in terms of grammes. in the atmospheric air originally contained in For the analysis weigh out a quantity of -the the apparatus, or, better, the apparatus nllay soil, or other substance containing a carbonate, be filled beforehand with air free from carplace it in the bottom of the larger glass ves- bonic acid. sel, and pour upon it 15 or 20 c. c. qf water. In case the soil, or other substance analyzed, Place in the porcelain crucible a quantity of evolves chlorhydric acid or other volatile acid some strong non-volatile acid, such as sul- on being treated with strong acids, the process phuric, phosphoric, tartaric or lactic acid, more is modified to the extent that the amount of than sufficient to decompose the whole of the baryta in the solution is determined before and. carbonate, and set the crucible upon the soil. after the absorption, by precipitating it in the Weigh the absorption vessel with its cover, form of Sulphate of Barium. pour into it a quantity of the standard baryta 3. Old method of absorption in amrnioniated water and again weigh. Remove the glass baryta-water. See above (Principle 11) and plate from the absorption vessel, place the lat- under Carbonate of Calcium. ter on the tripod, smear the top of the larger Principle IV. Decomposition of by soluvessel with tallow, close it tightly with its glass tions of the salts of iron, alumninum, mangaplate, and incline the vessel carefully so that nese and chromium; by phosphoric and arsenic some of the acid may flow out of the crucible acids; and by many other saline solutions and upon the soil. Repeat the dose of acid from acids; the metals or acids in question being at time to time, and then leave the apparatus at the same time precipitated in the form of byrest for a day or two, until the whole of the drates, or of basic salts. carbonic acid has been absorbed by the baryta- Applications. Separation of Al from Mg, water. - The rate of evolution of the car- Ca, Zn, Mln, Ni, Co and Fe (see Hydrate of bonic acid can be judged of by the appearance Aluminum). Separation of Fe from Ba, Sr, of the baryta solution. So long as carbonic Ca, Mg, Zn, Mn, Co, Ni and Fe (see Hydrate acid is generated rapidly, crusts of carbonate of Iron). Separation of Cr from Zn, MiIn, Ni, of barium will form upon the' surface of the Co and Fe (see Hydrate of Chromium). Sepliquor as often as the old crust is made to sink aration of P205 fronm Fe, Al, Ba, Sr, Ca, and by shaking the apparatus. When a crust no all other oxides not precipitable by carbonlonger forms, it is evident that no more car- ate of barium (see Phosphate of Iron). Sepbonic acid is being set free. Wait until the aration of As from Ba, Ca, Sr; Zn, Mn, Ni whole of the carbonic acid has been absorbed and Co (see Arseniate of Iron). - For lists by the baryta-water, then cover the absorption of the compounds precipitable by carbonate of vessel with its glass plate, and again weigh it barium, see that substance in Dictionary of with its'contents. By means of a syphon and Solubilities. aspirating flask, suck over as much of the clear For use as a reagent, carbonate of barium CARBONATE OF BISMUTH. 99 may be prepared as follows: — Dissolve a at any one time, since the chloride of barium quantity of crystallized chloride of barium in formed is only sparingly soluble in acid, and is hot water, filter the solution and heat it to liable to form an encrustation upon the mass boiling, Prepare a quantity of normal car- which would impede its solution. (Abich, Pogbonate of ammonium by saturating a solution gendorj's Annalen, 1831, 23. pp. 319, 338). of the commercial sesquicarbonate with am- The action of fused carbonate of' barium, or monia-water and filtering the mixture after it rather of the oxide of barium, into which the has been allowed to stand fbr some time. Add carbonate is converted at a hitgh heat, is ex — the carbonate of ammoniumn solution, little by ceedingly energetic. Even the most refiractory little, to the boiling solution of chloride of minerals may be readily and completely drbarium as long as any precipitate continues to composed by means of it. According to Abicil itll. After the mixture has been allowed to (loc. cit., pp. 339, 341), even chrome iron oreu settle decant the clear liquor and wash the may be completely decomposed by fusing it precipitate 5 or 6 times by decantation with once or twice during three quarters of an hour hot water, then throw it upon a filter and wash with 4 parts of carbonate of barium. until the wash water acidulated with nitric Method B. For decomposing silicates, less acid no longer gives any precipitate when carbonate of barium and a lower degree of heat tested with nitrate of silver. Wash the pre- will be required than are necessary for success, cipitate out of the filter into a beaker and keep in the applications of Method A. According! it for use, either in the moist state or air-dried. to Deville (Annules Chimr. et Phys., [3.] 38, Principle V. Power of decomposing refrac- 5), 0.8 part of carbonate of barium is sufficient tory silicates, aluminates and chromites, when at a moderate red heat, to reduce I part of intensely heated. potash feldspar to the condition of a vitreous Applications, Conversion of insoluble silicic transparent mass, decomposable by acids. acid into the soluble modification, in the analy- The use of a larger proportion of carbonate sis of some refiactory siliceous minerals. De- of barium may even be injurious, since a polcomposition of spinel and other native alumin- tion of' the potash set fiee by the caustic ba: ates, and of' chrome iron ore, as a preliminary ryta formed, might be lost through volatilizato their solution in acids. Decomposition of tion. In other respects the details of thll silicates as a preliminary to the estimation of process are similar to those described in A. It alkali-metals, has been superseded in great measure, by the Method A. For decomposing aluminlates and process of decomposing with fluorhydric acid. chromites. Mix the finely powdered mineral and by L. Smith's process with Carbonate of with fi'om 4 to 6 times its weight of pure, Calcium and chloride of ammoniunli (See furprecipitated carbonate of barium, in a plati- thoer under Silicates, and Oxide of Barium). num crucible. Place the platinum crucible L. Smith's (American Journ. Sci.. 1853, 16. inside a somewhat larger crucible of refi'actory 53) old method of' fusing silicates with a mixfire-clay; fill the space between the two cruci- ture of carbonate and chloride of barium will bles with magnesia, cover the clay crucible be described under the head of Silicates. and heat it intensely in a Sefstrdm furnace Principle VI. Insolubility in an aqueous during half or three-quartelrs of' an hour, solution of cyanide of potassium. Instead of the Sefstr6nm furnace, a, powerful Applications. Separation of Ba from Co, gas furnace, such as that of Griffin or of INi and Zn. Grove, may be used to heat the naked plati.- llethod. See Carbonate of (Cobalt. numrn crucible. Or Deville's (Annales Chim. et Basic Carbonate of Bismuth. Phys., 1856, 46. 182) oil of turpentine furnace Principle 1. Insolubility in water and ist may be used. But in any event an intense solutions of alkaline carbonates. heat is required to effect the fusion of' the Applications, Estimation of bismuth in commixed aluminate and carbonate of barium. pounds soluble in nitric acid and free from anyThe heat of an ordinary wind furnace is in- admixture of other acids. Separation of Ii sufficient for the purpose, - After the cru- from Mn. Separation of' Bi fiom Cu. cibles have been taken from the fire and M4lethod A. Add a very slight excess of carallowed to cool, clean the outside of the plati- bonate of anmmonium to the bismuth solution. num crucible and press it gently between the heat the mixture nearly to boiling for a shortl fingers to loosen the solid lump within it. Put time, filter, and ignite with the precautions the lump in a beaker, together with the cruci- prescribed under Carbonate of Lead. Weigh ble, if' any portion of the fused mass still ad- as Oxide of Bismuth. -- The bismuth soluheres to it, cover the mass with 10 or 15 times tion must not be too concentrated. If on diits bulk of water, and add strong chlorhydric luting it with water, some basic nitrate of or nitric acid, little by little, until solution is bismuth falls, no notice need be taken of it. complete. Since all the carbonic acid of the The process is inapplicable, however, in prescarbonate of' barium has been expelled by the sence of sulphuric or chlorhydric acids, sinc.u intense heat, the fused mass will dissolve with- the precipitated carbonate and the ignited oxidi; out effervescence'; but care must be taken not would then contain an admixture of basic sulto add too large a quantity of chlorhydric acid phate or basic chloride of bisnmuth. The lix 100 CARBONATE OF CADMIUM, ture of bismuth solution and carbonate of am- Carbonate of Cadmium. monium nmust always be heated in order to Principle I. Insolubility in water and in ensure complete precipitation. The results are carbonate of ammonium. in any event a trifle too low, for carbonate of Applications. Estimation of cadmium in bismuth is not absolutely insoluble in a solution general. Separation of Cd from Mn and Cu. of carbonate of ammonium. Mlethod A. Same as that described under.Method B. To separate bismuth from cop- Carbonate of Zinc. The precipitate should be per, mix the nitric acid solution with an excess collected upon a thin filter to avoid loss through of carbonate of ammonium. Most of the cop- reduction and volatilization, when the precipiper remains dissolved in the excess of the am- tate comes to be converted into Oxide of monium salt, but a little of it is retained by Cadmium. the precipitated carbonate of bismuth. The Method B. In case cadmium is to be sepaprecipitate must therefore be re-dissolved once rated from copper, add carbonate of ammoor twice in nitric acid, and re-precipitated with nium in excess, instead of the carbonate of carbonate of ammonium, in order to remove the sodium employed in Method A. Some cadlast traces of copper. It is well to add some mium will remain dissolved with the copper for carbonate of ammonium to the water used for a while, but on leavino the mixture exposed to washing the precipitate. If these precautions the air all the carbonate of cadmium will gradbe attended to, it is easy to remove all the cop- ually be deposited as carbonate of ammonium per from the precipitate (R. Schneider, Journ. evaporates. (Strorneyer). The method is said prakt. Chem., 60. 311), but a little bismuth to be more convenient but less accurate than always remains dissolved in the carbonate of those which depend upon the insolubility of ammonium and passes into the filtrate (H. Sulphide of Cadmium in cyanide of potassium, Rose, Poggq. Ann., 110. 430), hence the pro- and its solubility in dilute sulphuric acid. It cess is less accurate than that which depends is distinctly inferior also to the method by Sulon the insolubility of basic Chloride of Bismuth. phocyanide of Copper. To estimate the copper, heat the ammonia- For the method of separating Cd from Mn, cal filtrate, first by itself and afterwards with see Carbonate of Manganese. caustic lye, and collect the Oxide of Copper Properties. Carbonate of cadmium is a white which is thrown down. precipitate, insoluble in water and the fixed alFor the method of separating Bi from Mn, kaline carbonates; exceedingly sparingly solsee Carbonate of Manganese. uble in a solution of carbonate of ammonium, Properties. When an excess of carbonate but readily soluble in solutions of the sulphate, of ammonium is added to a nitric acid solution nitrate, etc., of ammonium. The water which of bismuth, in the cold, a white precipitate of the precipitate contains is completely expelled the mon6carbonate (Bi203, CO2) is immediately by drying, and the carbonic acid by ignition. thrown down, but the precipitation is incom- Principle JI. Solubility in an aqueous soluplete, since a portion of this monocarbonate tion of cyanide of potassium. remains dissolved in the ammonium salt. But Applications. Separation of Cd from Bi and on heating the mixture a more difficultly sol- Pb. uble basic salt is formed. Carbonate of potas- Method. See Carbonate of Bismuth and sium also precipitates bismuth completely, but Sulphide of Cadmium. the precipitate in that case retains traces of Carbonate of Calcium. potash which are hard to wash out. The pre- Principle I. Fixity when gently heated. cipitate obtained by carbonate of ammonium Applications. Estimation of calcium in oxis easily washed. It is as good. as insoluble in alate of calcium and other compounds of calwater, but dissolves readily in acids. When cium with organic acids. ignited it gives off carbonic acid and is con- Method. In case the substance to be operverted into teroxide of bismuth. ated upon is oxalate of calcium, heat it carePrinciple II. Insolubility in an aqueous so- fully and gradually in a platinum crucible until lution of cyanide of potassium. the bottom of the crucible has become almost, Applications. Separation of Bi from Cu, but not quite, dull red. The crucible should Cd, Hg, Ag and Au. be covered at first, but may be open afterwards. Method. Add to the dilute solution a very Keep the crucible at this temperature, decidslight excess of carbonate of sodium, then edly below incipient redness, during 8 or 10 add an excess of a solution of cyanide of potas- minutes, then allow it to become cold, and slum, heat the mixture for some time, and col- weigh. - The carbonate of calcium obtained lect the carbonate of bismuth upon a filter. should be white, or only faintly tinged with Since the carbonate thus thrown down always gray. It should give no alkaline reaction when retains some alkali, it must be dissolved in moistened and subsequently tested with a small acid and re-precipitated. The cyanide of po- slip of turmeric paper. If the turmeric turn tassium used must be free from any trace of brown it will be evident that the precipitate sulphide. (Fresenius & Haidlen, Annal. Chem. has been overheated and that a portion of it und Pharm., 43. 129). has been changed to caustic lime through es CARBONATE OF CALCIUM. 101 cape of carbonic acid. In that event pour as hours. Collect the precipitate on a filter, wash much of a strong aqueous solution of carbon- it with water containing some ammonia, dry ate of ammonium into the crucible as will and ignite, or rather heat, the precipitate, as barely cover the precipitate, evaporate to ab- directed above (Principle I). The process solute dryness upon a water bath, heat the dry yields accurate results when the liquid in precipitate gently over a lamp, but not nearly which the precipitate is formed contains no to redness, and again weigh. It is to be ob- great quantity of ammoniumn salts. It is essenserved that a very moderate heat will be suffi- tial that the precipitate be washed with ammocient to volatilize the excess of carbonate of am- niated water, as will be seen below, under monium. There is no need of actually igniting " properties." the precipitate before weighing it the second B. Separation of Ca firom K, Na antd Mg. time, and consequently no risk of expelling See the similar heading under Carbonate of any carbonic acid from the revivified carbon- Barium. Much that is said in that place of ate. The process gives good results when the preference to be given to Sulphate of properly conducted, but the operator should Barium might be said here of Oxalate of Calon no account fail to apply the test with tur- cium. meric paper. - Before proceeding to ig- C. Separation of Ca friom Mn. See Carnite oxalate of calcium, or carbonate of cal- bonate of Manganese. There is nothing pecucium which has been thrown down as such, liar in the process as applied to the separation take care to remove the precipitate'from the of Ca from Mn, excepting that the ignited filter as completely as possible, and burn the precipitate must be treated with carbonate of filter thoroughly upon the lid of the crucible ammonium to revivify the reduced carbonate out of contact with the precipitate. It is even of calcium, as has been explained above. See best not to add the siliceous filter ash to the Carbonate of Calcium (fixity of). Unless the carbonate in the crucible until after the latter proportion of calcium in the mixture is large, has been heated. it will usually be best not to weigh as CaO, If any other salt than the oxalate is to be MnO3- + CaO, C09,-but to ignite strongly converted to the state of carbonate by ignition, over a blast lamp and weigh as CaO, Mn203 tproceed as directed under Carbonate of Ba- CaO. See Oxide of Calcium. rium (fixity of), and take special pains in D. Indirect separation of Ca from Ba and treating the residue with carbonate of ammo- Sr. See Carbonic Acid (volatility of, —methods nium as above described. by simple ignition and ignition with an acid Properties. Carbonate of calcium undergoes salt). no change in the air at temperatures below E. Estimation of Carbonic Acid. faint redness, but at an intense red heat it 1. Fresenius's method. Prepare a quantity gradually loses carbonic acid, especially when of dry pulverulent hydrate of calcium by slakexposed to a current of air or steam. When ing a quantity of recently burnt lime with mixed with carbon the decomposition by heat water. Put a smnall portion of the hydrate is far more rapid, carbonic acid being reduced into dilute chlorhydric acid to test whether it and given off in the form of carbonic oxide, is free from carbonic acid. If no effervescence Quantities of carbonate of calcium as large as is seen, seal up a number of portions, each of half a gramme may easily be completely con- 2 or 3 grms., of the hydrate in small glass tubes verted to quicklime by heating them in an for future use. But in case the hydrate is open platinum crucible over an ordinary gas found to contain any carbonic acid place it in blast lamp; but Fresenius has found that the a tube of hard glass and ignite it upon a coinheat of a Berzelius spirit lamp is insufficient bustion furnace, in a current of air fiee from to effect this reduction. The composition of carbonic acid; and afterwards seal up several the salt is as follows, both in terms of mole- small portions of it as before, cules and per cents. Put 2 or 3 grmis. of the pure lime into a light CaO = 56 flask of about 300 c. c. capacity, close the CO2 = 44 flask with a caoutchouc stopper and weigh it 100 together with the stopper and the lime. Pour Principle 11. Sparing solubility in water. i enough of the mineral water, or other soluApplications. Estimation of calcium in aque- tion of carbonic acid, to nearly fill the flask, ous solutions of calcium salts. Separation of replace the cork, shake the mixture and again Ca from Na, K, Mg, Mn. Estiniationof' car- weigh. The difference between the two weigllbonic acid in rocks, soils. waters, air, etc. In- ings gives the weight of the mineral water. direct separation of Ca from Ba and Sr. Loosen the stopper and heat the contents of Methods. the flask for some time upon a water bath, in order that the amorphous carbonate of calcium A. Estimation of Calcium in solutions of its at first formed may become crystalline. WVithsalts. Saturate the moderately dilute solution out disturbing the sediment at the bottom of with ammonia-water, add a solution of carbon- the flask, pour, the clear liquid upon a small ate of ammonium in slight excess and let the plaited filter and allow the filter to i.rain; mixture stand in a warm place for several then, without washing either filter or precipi 102 CARBONATE OF CALCIUM. tate, throw back the filter with its contents the acid solution, heat the latter carefully until into the flask and determine the carbonic acid it boils, then add a few drops of litmus, and by decomposing the carbonate with an acid determine the amount of free acid by titrating and collecting the Carbonic Acid in soda-lime, with a standard solution of soda. Or, better, in the manner described on p. 91. - In case omit the boiling and use Cochineal instead of the mineral water contains an alkaline bicar- litmus to indicate the point of saturition. By bonate, it is well, after filling the flask, to add subtrLacting the amount of acidl neutralized by to the liquid enough chloride of calcium to the soda from the quantity of acid taken to decompose the bicarbonate. It is unnecessary dissolve the carbonate, the amount of acid neuto make any correction or allowance in this tralized by the latter will be obtained. The case, for the trifling solubility of carbonate of proportion of calcium in the precipitate, that calcium in water. - The method is accu- is to say, the amount of calcium equivalent to rate, simple and expeditious, and is very much the acid thus neutralized, Inay readily be calto be preferred to the old method of treating culated from these data. the mineral water with a mixture of chloride B. The estimation of Carbonic Acid may of calcium, or chloride of barium and amino- evidently be effected in the same way as that nia-water, and afterwards weighing or titrating of calcium, by the method just described, it the precipitate. (Presenius, Zeitsch. analyt. being merely necessa.ry to calculate how much Chem., 1863, 2. 56). carbonic acid is equivalent to the amount of In case the mineral water to be examined is standard acid neutralized by the carbonate. contained in a bottle, it may be transferred to The manner of applying the process will apthe lime flask by means of a syphon, after the pear more fully in the following paragraphs. bottle and contents have been cooled to about, C. Pettenkofe r's method of estimating car40. If the water were poured directly from bonic aid by lime wasc!er. Pi-epare a standard the bottle into the flask, some free carbonic solution of' oxalic acid of the strength indicated acid might flow into the latter with the water. in the description of the analogous process Sometimes the process above given of weigh- with baryta-water (see Carbonate of Barium), ing the mineral water, had better be dispensed Standardize a quantity of lime-water with this with, and only the volumne of the water de- oxalic acid in the same way the baryta-water termined. is standardized, and proceed with the analysis Thus when water is collected at a spring by as follows: Measure off l10 c. c. of the spring opening a large pipette, or a flask provided 5oater or other dilute solution of carbonic acid with two orifices (Mohr, Annalen der Pharm., to be analyzed, into a dry flask; add to it 3 1834, 11. 231 or Titrirmethode, 1855, 1. 115), c. c. of a highly concentrated solution of chlobenealth the surface of the water and then ride of calcium, 2 c. c. of a saturated aqueous closing and withdrawing the vessel with its solution of chloride of ammonium, and 45 c. c. contents, it is easy to determine the capacity of the standard lime-water. Close the flask of' the pipette or flask beforehand, and to with. a caoutchouc stopper, shake its contents, transfer its contents directly to the lime flask and leave it at rest for 12 hours in order that without need of further measurement. the amorphous carbonate of calcium, at first 2. By precipitating with a mixture of chloride thrown down, may become crystalline. The of calcium andl ammonia. See the similar total volume of liquid in the flask amounts to heading under Carbonate of Barium, and be- 150 c. c. Take out two portions, each of' low under Principle II1. 50 c. e. of the clear liquid, and by means of the 3. Peutenkofer's mlnethod. See below, and standard oxalic acid an d turmeric paper, deterpnder Carbonate of Barium, also. mine in each portion how much hydrate of calcium still remains free and uncombined with Principle IlL. Power of neutralizing acids. carbonic acid. Precisely as in the operation Applications. Estimation of calcium, of ecar- of standardizing, the experiment upon the first bonic acid, and of most free acids (see Acid- portion of liquid will give an approximation to imetry). the truth, and that with the second portion an Methods. accurate result. Multiply by 3 the number of A. Estimation of Calcium (Compare Alka- c. c. of oxalic acid used in the last experiment limetry). and subtract the product from the riumber of Pour upon the powder or the moist precipi- c. c. required to neutralize 45 c, c. of the stantate which is to be examined, a me sured quan- dard lime-water. The difference will show tity of riitric or chlorhydric acid of kfiown how much lime has been precipitated by carstrength, taking care to use a little more acid bonic acid, and, as has been said, each c. c. of than would be sufficient to dissolve the carbon- the acid corresponds to 1 millig. of CO. ate. To do this, place the carbonate in a flask The chloride of calcium is added in the case And pour the acid slowly upolr it frorn a bu- of a mineral or spring water, as supposed above,.rette in such manner that 1ro portion of the to decompose any traces of carbonate or other liquid slall be thrown out of the flask by the alkaline salt whose acid might be precipitated escaping carbonic acid. In order to drive out by lime-water. The purpose of the chloride of the ca'b1onio acid which reimaiuns dissQlved il ammonium, on the other hand, is to prevent the CARBONATE OF CALCIUM. 103 precipitation of magnesium in case any corn- Pour into the flask a measured quantity of pound of that metal be present. The addition standard nitric or chlorhydric acid, more than of chloride of calcium is beneficial, moreover, sufficient to dissolve the whole of the precipiin case the lime-water happens to contain tate, heat the liquid to expel the carbonic acid traces of free caustic alkali, or the carbonic and titrate the excess of acid with a standard acid water any carbonate of magnesium, for, alkali, as described under Alkalimetry. The in the absence of chloride of calcium, an oxa- point of saturation may be indicatod either by late of either of the alkali metals or of mag- Litmus solution added to the liquor, or by Turnesium would react upon the carbonate of cal- meric paper as in Pettenkofer's process aibove cium, which is almost always contained in car- *described. bonic acid waters, to form oxalate of calcium According to Mohr, the alkalimetric process and a carbonate of an alkali or of magnesium, with carbonate of calcium is to be preferred to and the latter would immediately combine again the corresponding process with carbonate of with oxalic acid. barium, in spite of the fact that carbonate of If the water under examination contains barium is more nearly insoluble in water than nothing but carbonic acid, it is merely neces- the calcium salt, for precipitated carbonate of sary to add lime-water (or better, dilute baryta- calcium is far less bulky than carbonate of bawater) to it, and heat the mixture for some riumn, and is more readily filtered than the time to 700 or 800 to facilitate the change of latter, since it is less liable to clog the pores of the amorphous carbonate to the crystalline con- filter paper. The comparatively high atomic dition, but in case any chloride of ammonium weight of carbonate of barium has no signifihas been added to the mixture no heat should cance in a process where the precipitate is not be applied lest some ammonia be expelled. to be weighed. Like the carbonate of barium This process was formerly recommended by process, however, the method of precipitating its author fobr the analysis of waters containing carbonate of calcium from an ammoniacal sobut little carbonic acid, while the analogous lution is exposed to several sources of error, method with baryta-water was preferred for and is no longer held in much esteem. analyzing waters highly charged with carbonic In case of need, the process may be applied acid. In his later papers, however, Pettenkofer to the estimation of gaseous carbonic acid. In urges that the process with baryta-water be that event, the details of the method remain always used, to the exclusion of lime-water, for unchanged, with the exception that the gas is the amorphous carbonate of calcium which made to flow into a mixture of chloride of forms when limle-water and carbonic acid are calcium and ammonia-water, or better, into first mixed is somewhat soluble in water, and ammonia-water to which chloride of calcium exhibits an alkaline reaction which may easily is afterwards added. vitiate the titration. In presence of an excess Properties of Carbonate of Calcium. The of lime-water the amorphous carbonate of cal- precipitate as ordinarily obtained, is a soft, cium changes to the insoluble crystalline state white powder, scarcely at all soluble in absocomparatively slowly. Baryta, moreover, ex- lutely pure, cold water, but appreciably soluble hibits a stronger alkaline reaction than an in ordinary distilled or other water which conequivalent quantity of lime. tains traces of carbonic acid gas, and the soluD. Old method of collecting carbonic acid in tion thus obtained exhibits a faint alkaline rea mixture of chloride of calcium and ammonia. action. It is somewhat more readily soluble in All that has been said under Carbonate of Ba- boiling than in cold water. It is far from being rium of the preparation of the absorbent solu- insoluble in cold aqueous solutions of ammnotion and the precipitation of the carbonic acid, nium salts, such as the nitrate and chloride, applies here as well, with the exception that and dissolves readily in hot solutions. The chloride of calcium must be substituted for the presence of free ammonia and carbonate of chloride of barium. There is, however, in ammonium, however, hinders the solvent acthis case no need of bringing the whole of the tion of the ordinary ammonium salts. Soluprecipitate upon the filter, nor of rubbing off tions of the normal salts of potassium and those portions of it which remain sticking to sodium have a tendency to dissolve it, but their the flask. After the precipitate has been action is more feeble than that of ammonium thoroughly washed, put the funnel which holds salts. Carbonic acid water dissolves it easily. the filter into the neck of the flask in which It cannot be precipitated from solutions which the precipitate was formed, push a glass rod contain citrates or metaphosphates of the alkathrough the point of the filter and wash as lies. (See, further, Dictionary of Solubilities). much of the precipitate as possible from the For use as a reagent, pure carbonate of calfilter into the flask, then spread out the filter cium may be prepared as follows: —Dissolve a upon a plate of' glass, wash off the last parti- quantity of white marble or of ignited stalaccles of the precipitate into the funnel and tite, in chlorhydric acid, neutralize the soluflask, and boil the wash water gently for half tion with ammonia-water, heat the mixture to an hour. The purpose of the boiling is to ex- boiling and filter to separate the small quantity pel ammonia, somle of which is retained by the of iron and alumina which is thrown down. precipitate even after long continued washing. Heat the filtrate to boiling in a large beaker, 104 CARBONATE OF CALCIUM. and throw into it, one by one, small bits of cium and caustic lime. The mixture is filtered solid carbonate of ammonium until they cease and the powder well washed; a quantity (1 or 2 to dissolve. Wash the heavy crystalline pre- grins.) of carbonate of ammonium in solution is (ipitate by decantation with hot water. (Mat- then added to the filtrate and the latter is evapthiessen). orated to a bulk of about 30 c. c. A little more Principle IV. Power of precipitating iron, carbonate of ammonium together with a few aluminum, manganese, chromium, etc. See drops of ammonia-water is added to ensure a the Hydrates of' those metals. For lists of the complete separation of the calcium, and the mixsubstances precipitable by carbonate of calcium ture is again filtered. Collect the filtrate and see that substance in Dictionary of Solubili- washings in a weighed platinum capsule and ties. evaporate to dryness on a water bath. Place Principle V. Insolubilityin an aqueous solu- the capsule in a capacious iron cup and heat tion of cyanide of potassium. the latter so that the contents of' the platinum Applications. Separation of Ca from Co, capsule within it may be thoroughly dried. Ni and Zn. Finally, heat the capsule carefully almost to Method. See Carbonate of Cobalt, redness to drive out the ammoniumn salts, cool Principle VI? For the use of carbonate of and weigh. The alkali chlorides thus obtained calcium, or rather, of oxide of calcium, in de- are nearly pure, though a trifling amount of conmposing silicious minerals, see Silicates. black residue will usually be seen on dissolving The following account of Lawrence Smith's them in a few drops of' water. This residue method of separating alk/alies from refractory may be removed, if need be, by filtering through silicates by decomposing the mineral with car- a very small filter. -- Prof. Smith's process bonate of calcium and chloride of ammonium, is by far the most convenient and accurate for is taken from Prof: Johnson's edition of Fre- separating the alkalies from silicates, and is senius's Qua nt. Analysis, New York, 1870, p. universally applicable except perhaps in pres303. Though out of place in this connection, ence of boracic acid. (Johnson, loc. cit,). the importance of the process is such that early BiCarbonate of Calcium. mention should be made of it. _ Mix 1 Principle. Power of neutralizing acids. part of the pulverized silicate with 1 part of Application. Estimation of bicarbonate of dry crystallized chloride of ammoniurn by gen- calcium in natural waters. tie trituration in a smooth mortar, then add 8 Method. The method is merely one of parts of pure, precipitated carbonate of' calcium, Acidiimetry, in which a solution of phosphate and mix the whole intimately. Transfer the of copper in chblorhydric acid is made to serve mixture to a platinum c(rucible, taking care to both as the standard acid and as the indicator rinse the mortar with a little carbonate of cal" of the point of saturation. - To prepare ciumn. Warm the crucible gradually over a the copper solution, mix a solution of cuprie small Bunsen burner until fimles of aimmonium chloride with one of ordinary phosphate of salts no longer appear; then heat to full red- sodium, wash the phosphate of copper which ness, but not too intensely, during 30 or 40 is precipitated, mix the washed precipitate minutes. An ordinary portable furnace or with water, and add to the mixture moderately chafing dish provided with a conical sheet-iron strong chlorhydric acid, drop by drop, until, cap or chlimney 2 or 3 feet high will give heat the chlorhydric acid being slightly in excess, a enough for the purpose, in default of' a large clear solution is obtained. WVhen such a soluBunsen lamp. - The mass in the crucible tion is dropped into a solution of bicarbonate should sinter together but not fuse. When of calcium-or of any carbonate or bicarbon, cold, it may usually be detached with ease from ate of either of the alkali-or alkaline-earthy the platinum, Heat the sintered lump to boil- metals -a quantity of' the phosphate of coping in a capsule with 100 c. c. of water for per is precipitated, at first, as the calcium, several hours, or until it is entirely disinteg- or other alkaline metal, neutralizes the free rated and faillen to powder. In case the lump, chlorhydric acid; but the liquid soon becomes from having been overheated, remain partially clear again when a further portion of the cucoherent after long boiling, it may be trans- pric solution is added, for the precipitate referred to a porcelain mortar, ground to fine dissolves in the free acid which this solution powder and then boiled as before. Some sili- contains. —, The moment at which the turcates, notably those containing much protox- bid solution becomes clear, is taken as the point ide of iron, fuse easily with the proportions of of saturation, for the quantity of cupric soluflux above given. It is best when this hap- tion required to effect the precipitation and pens to repeat the ignition on a new quantity re solution is proportional to the amount of base of the mineral, using as much as 10 or 12 parts in the substance tested, and consequently to of carbonate of calcium and taking care to the amount of carbonic acid which was combring only the lower three-fourths of' the crL- bined with the base to form a bicarbonate. cible to a red heat. - When completely The presence of free carbonic acid, that is to disintegrated by boiling with water, the sintered say, of an excess of the acid over and above mass gives up to the water all the alkalies as what is necessary to form a bicarbonate, has Chlorides, together with some chloride of cal- no influence whatever upon the indications of CARBONATES. 105 the process. - The cupric solution is stand- collect the precipitate upon. a filter and wash ardized against pure, dry carbonate of sodium. with a solution of carbonate of ammonium. To this end dissolve 0.265 grm. (equal one two- To estimate the cobalt, dissolve the mixed hundredth of an equivalent) of the dry salt in precipitate in chlorhydric acid and proceed in distilled water, dilute the solution to the vol- the usual way. The nickel may be determined ume of a litre (see Alkalimetry), and saturate in the filtrate. (L. Thompson, Zeitsch. analyt. the solution with carbonic acid gas. The Chem., 1864, 3. 375). iExperiments by Winkcopper solution may be made of such strength ler, ibid., p. 376), go to show that the process that 4.4 c. c. of it will saturate, in the manner as presented by Thompson, is wholly unfit for explained above, 100 c. c. of the standard soda quantitative use. Not only is some carbonate solution. With a liquid of this strength, it will of nickel always found in the precipitate, but only be necessary to multiply by 22 - 44 (= a quantity of cobalt invariably remains in so0.5) the number of c. c. of the liquid consumed lution and passes into the filtrate. in titrating any 100 c. c. sample of natural Carbonate of Copper. water, in order to obtain the amount of car- Principle 1. Solubility in an aqueous solu-, bonic acid in that water expressed in terms of tion of carbonate of ammonium. centigrammes. It is well also to employ a Applications. Separation of Cu from Bi and, burette graduated to fifths of cubic centime- Cd. tres. - The process is said to be superior HMethod. See the Carblnates of Bismuth and. to that of Barth6lemy (see Carbonate of Mer- of Cadmium. cury), inasmuch as it is applicable to waters Principle II. Solubility in an aqueous solucontaminated with chlorides and sulphates. It tion of cyanide of potassium. succeeds better with bicarbonates than with Applications. Separation of Cu from Bi the normal carbonates, and may be applied to and Pb. either of the bicarbonates as well as to bi- JMethod. See Carbonate of Bismuth andt carbonate of calcium. (Lory, Chemical Newvs, Sulphide of Copper. 1L8. 169). Principle III. Insolubility of the basic carCarbonate of Cobalt. bonate. Principle I. Solubility in an aqueous solu- Applications. Estimation of copper in acid tion of cyanide of potassium. solutions. Separation of Cu from Mn. Applications. Separation' of Co from Ba, Method. Some years since, H. Rose (Hand-:Sr, Ca and Al. buch analyt. Chem., 1851, 2. 188) stated that Method. Mix the solution with a slight ex- copper cannot be completely precipitated by cess of carbonate of sodium. Add a quantity means of carbonate of potassium. According of cyanide of potassium solution to the mixture to this chemist a certain proportion of the copof liquid and precipitate, and heat the whole per remains obstinately in solution, and can gently until the whole of the carbonate of only be obtained by evaporating the liquid to, cobalt has redissolved. Collect the undissolved dryness and gently igniting the residue. But carbonate of the alkaline earths upon a filter, Gibbs has found that Rose's statement is too and precipitate the cobalt in the filtrate as strong; the whole of the copper may be preCobalticyanide of' Mercury. cipitated by alkaline carbonates from solutions, Principle If. Insolubility in water. of sulphate, nitrate or chloride of copper when Carbonate of cobalt mnay be precipitated.by the latter are sufficiently dilute and are boiled adding an alkaline carbonate to the solution of for a long time with the carbonated alkali. a cobalt salt. But the precipitation can with The best method of effecting the precipitadifficulty be made complete even by long con- tion is as follows:-Dilute the copper solution tinued boiling. The principle is not to be until it contains no more than one gramme of recommended as a means of determining co- copper to the litre. Add a solution of carbonbalt. (Gibbs & Taylor, American Journ. Sci., ate of potassium or of sodium, in slight excess, 1867, 44. 214). and boil the mixture for half an hour. The Carbonate of Cobalt and of boiling proceeds quietlywithout bumping; the; Calci u m. blue-green carbonate soon becomes dark brown Principle. Insolubility. and the oxide or basic carbonate finally ohApplication. Separation of Co from Ni. tained has a fine granular character which renMlethod? Dissolve the mixture of cobalt and ders it extremely easy to wash. The small nickel in a slight excess of chlorhydric acid portion of the precipitate which usually adand add to the solution 10 parts of chloride of heres to the sides of the vessel in which the calcium and 10 parts of chloride of ammonium boiling takes place, must be redissolved in for every 3 parts of the mixed oxides which acid and again precipitated; but great care are contained in it. Mix the solution with must be taken not to add too large an excess 150 parts of cold water and 20 parts of ses- of the alkaline carbonate, lest a solution be quicarbonate of' ammonium, previously dis- formed from which the copper cannot be presolved in 100 parts of cold water, and grad- cipitated by boiling. If the process be well uall~y heat the mixture to boiling. After the conducted, the original filtrate will be persolution has been allowed to cool and settle, fectly free from copper. The washed precip 4106 CARBONATES. itate may be ignited in a current of hydrogen, no trace of carbonic acid, but dissolves in carand the Copper weighed as such; it will be bonic acid water. According to Fresenius, 1 found to be free from alkali. The ignition part of it dissolves at the ordinary temperature must be carefully conducted, since the ignited in about 50,000 parts of water which has been precipitate is so finely divided that particles of boiled. It is more soluble in water charged it are liable to be carried off in the current of with ammoniacal salts than in pure water. On gas. (Gibbs & Taylor, American Journ. Sci., ignition it loses its carbonic acid readily. 1868, 44. 213). When thrown down by an excess of bicarbonFor the method of separating Cu firom M-n, ate of sodium the precipitate retains traces of see Carbonate of Manganese; as well as the the sodium salt. description above given. Test the filtrate Principle II. Insolubility in an aqueous from the mixed carbonate'with sulphydrate of solution of cyanide of potassium. ammonium, to be sure that all the copper has Applications. Separation of Pb from Cu, gone down. Cd, Hg, Ag and Au. Carbonate of Lead. ~ Method. See Carbonate of Bismuth. The Principle I. Insolubility in cold water. carbonate of lead thus precipitated always Applications. Estimation of lead in all salts contains alkali. It may be dissolved in nitric of that metal which are soluble in water, or acid and reprecipitated by carbonate of amnfrom which the lead can be dissolved by nitric monium, as in Principle I, or as Sulphate of acid. Separation of Pb from Mn. Lead. Or it may be reduced to metallic Lead M'ethod. Add a slight excess of carbonate by fusion with cyanide of potassium. of ammonium, together with a small quantity Basic Carbonate of, Magnesium. of amnonia-water, to the moderately dilute Principle I. Insolubility in water. solution of the lead salt. Heat the mixture Applications. Estimation of Mg in presence for some time, and allow it to settle until the of K, and in a solution of Mg in carbonic acid liquid has become clear, then collect the pre- water. (Method A). - Separation of K cipitate upon a small, thin filter and wash it from a mixture of Mg, Ba and Ca. (Method with cold water which has been recently boiled B). - Separation of Mg from Mn. to expel carbonic acid. Ignite the dried pre- Method A. To estimate magnesium in prescipitate in a porcelain crucible and weigh as ence of alkalies, when the quantity of' the Oxide of Lead. The filter should be burned latter is not to betletermined, boil the solution by itself upon the cover of the crucible, after strongly for a long time with an excess of carthe precipitate has been removed from it as bonate of potassium, and wash the precipitate completely as possible. It is well also to with boiling water. The washing must be moisten the cold filter-ash with a drop or two proceeded with without interruption until a of nitric acid, and to evaporate and ignite few drops of the filtrate leave only a small before weighing. - The process is a toler- residue when evaporated on platinum foil. ably satisfactory one, though the results ob- Though the compound is somewhat soluble in tained are usually somewhat too low, on ac- water, it is less so in hot than in cold, and count of the solubility of the precipitate. It comparatively little of it is taken up by water is easy to incur loss also in burning the filter, which is boiling hot and free from carbonic through reduction of some of the precipitate acid. The dried precipitate is ignited strongly left upon the paper. The method, however, and the residue weighed as Oxide of Magneis better than that which depends on the insol- sium. - This method was formerly much ubility of Oxalate of Lead. (Mohr and Fre- employed, but is no longer held in esteem. It senius). is inconvenient and liable to several sources of Lead may be precipitated as completely by error. Hence it has been superseded by the means of the bicarbonate of potassium or so- method which depends on the insolubility of dium as by carbonate of ammonium; normal Phosphate of Magnesium and Amnmonium. carbonate of lead being thrown down in both The normal carbonate of magnesium, which instances. But the precipitation is not com- may be supposed to be precipitated at the moplete with the normal alkaline carbonates, and ment when carbonate of potassium is added, a not insignificant portion of the precipitate is decomposed, by boiling, into an insoluble may be dissolved in case it is heated with an basic and a soluble acid carbonate, and in excess of the normal carbonate of either of the order to decompose the latter completely the fixed alkalies. (H. Rose). liquor has to be boiled for a long time. A For the separation of Pb from Mn see Car- similar remark applies to the case where magbonate of Manganese. Add carbonate of nesium is to be determined in a carbonic acid ammonium or bicarbonate of sodium to the water solution. - The mixture must be boiled filtrate from the mixed carbonates of Pb and strongly from first to last, in order to avoid a Mn, to ensure the complete precipitation of difficultly soluble compound of carbonate of the lead. magnesium and carbonate of potassium, which Properties. Precipitated carbonate of lead forms at moderate heats. Carbonate of sois heavy, white and pulverulent. It is alinmost dium is somewhat inferior to carbonate of absolutely insoluble in water which contains potassium as the precipitant, since an insoluble CARBONATE OF MAGNESIUM. 107 double carbonate forms more readily with of water dissolves 0.106 grm. of normal (?) sodium than potassium. Both these double carbonate of magnesium. (Zeitsch. analyt. compounds are decomposed by ignition, or Chem., 1869, 8. 91). rather, after ignition it is easy to wash out the Principle II. Solubility in carbonic acid alkaline carbonate from the oxide of magne- water. slum. Since it is not easy to determine Applications. Separation of Al from Mg and when all the masgnesium has been precipitated, from both Mg and Ca, if the proportion of the and since some of it would inevitably remain latter be very small. dissolved if the boiling were stopped too soon, Meth jd. Place the cold, moderately acid, it is well to evaporate the liquid to dryness in rather dilute solution in a beaker provided with order to be sure that the separation is com- a suitable cover. Add a solution of'bicarbonate plete. To this end let the boiled mixture of potassium or sodiumn prepared in the cold, settle, decant the clear liquor into an evapo- as long as any effervescence occurs, or any prerating dish, best of platinum, throw the pre- cipitate falls. Violent effervescence occurs. cipitate upon a filter and add the filtrate and during' the precipitation, all the alumina is first portions of wash water to the liquid in thrown down in the form of a hydrate, while the dish. Boil down the liquid rapidly to the magnesium remains dissolved in the liquid absolute dryness, heat the residue strongly, and charged with carbonic acid. After the lixafter the dish has become cold treat the resi- ture has been allowed to stand'for 12 hours, due with hot water. Collect the small portion decant the clear liquid into a filter and wash of the mass that remains undissolved, upon a the precipitate, first with cold carbonic acid small filter, and wash'it by itself. To avoid water bydecantation, and afterwards with pure. loss in the process of drying, place the dish, at water upon the filter. Carbonic acid water last, within a capacious iron cup and stir its for the washing may be prepared by slowly contents continually, at a gentle heat, until adding to a highly dilute solution of bicarbonthe wlass is completely dry. The liquid must ate of potassium or sodium a small quantity of' be boiled strongly during the process of evap- chlorhydric acid, insufficient to combine with oration in order to hinder the saline matter the whole of the metal. -- Magnesium may from creeping over the edg(e of the dish. The be determined directly in the filtrate, as Phosoriginal method of evaporating the entire phate of Magnesium and Ammonium. The mixture of precipitate and liquid to dryness is alumina precipitate is often free or almost firee not to be commended. (v. Bonsdorf, Pogg. from any trace of niagnesium (H. Rose) but Annal., 18. 128). - In ease the magnesium since it is liable to retain some alkali, it had solution contains ammonium salts, carbonate of better be dissolved in chlorhydric acid and the potassium must be added to destroy them. A solution treated with ammonia-water to throw large excess of carbonate of potassium is down Hydrate of Aluminum. - The proadded to the liquid, the mixture is warmed cess was formerly much employed and would until the odor of' ammonia ceases to be per- still appear to be valuable. ceptible, more carbonate of potassium is added, In case the method is employed for separatand the mixture again warmed to make sure ing both lime and magnesium from aluminum, that the whole of the ammonia has been ex- the solution should be very dilute and a stoppelled, and the liquid is finally boiled as above pered fla.sk should be employed, instead of a. described. In case the boiled liquid fails to beaker, to effect the precipitation. Satisfactory give a strong alkaline reaction with red litmus results can be obtained only when the quantity paper, a new quantity of carbonate of potas- of lime is very small, since it is liable to be resium must be added, and the mixture again tained by the alumina. boiled. (H. Rose, Handbuch, 1851, 2. pp. 33- Principle II1. Power of neutralizing acids, 37, 52). Application. Valuation of the commercial Mlethod B. Heat the chlorhydric acid solu- carbonate. tion of magnesium, calcium, barium and the M~Iethod. Dissolve about a gramme of the subalkalies to actual boiling, add a solution of stance to be tested in 60 or-70 c. c. of normal carbonate of sodium, drop by drop, as long as nitric acid, taking care to measure the acid and any precipitate continues to fall, and boil to use an excess of it. Determine the excess of strongly until the volumninous precipitate be- acid by titration with a standard solution of amcomes compact and granular. If the precipi- monio-sulphate of copper (see Acidimetry), and tate is boiled long enough it can be washed subtract this excess from the amount of acid free from potassium. Acidulate the filtrate taken. The difference will be equivalent to the with chlorhydric acid, and determine the po- amount of niagnesium in the substance. The tassiumn as Chloroplatinate of Potassium. (Stoh- results obtained are usually somewhat too low. mann, Zeitsch. analyt. Chenm., 1866, 5. 307). The process is of technical application only; For the method of separating Mg from Miln, it has no claim to scientific accuracy. Insee Carbonate of Manganese. stead of the ammonio-sulphate of' copper, stanAccording to Bineau, I litre of water dis- dard ammonia-water may be employed to desolves 0.06 grin. of three-fourths carbonate of termine the excess of acid, but, according to inmanesium. According to -Chevalet, a litre Mohr, the copper solution is to be preferred. 108 CARBONATES. In any event magnesium is less conveniently but it is always safer to dissolve it by means of determined by alkalimetric methods than either an excess of the precipitant and by agitat;on. of the metals of the alkaline earths. When The final precipitate is granular and may be normal nitric acid and litmus solution are added washed readily. It does not adhere firmly to either to carbonate of magnesium or to calcined the sides of the beaker. But the chief merit magnesia, the red color of the litmus very soon of the process consists in its applicability even changes to blue and remains so as long as any in presence of large quantities of salts of amtrace of the magnesium compound is left un- monium or of the fixed alkalies. It is only dissolved. On adding more of the acid, until necessary in that case to let the mixture stand the color appears bright red, and then titrating for 24 hours and to stir it frequently. The backwards with caustic soda until the liquid process is inapplicable in presence of phosphobecomes blue, results are obtained which indcli- ric or arsenic acids. ( Schaffgotsch, Pogg. cate too little magnesium. (Mohr, Titrirmeth- Annal., 104. 482; H. Weber, Kopp's Jahresode, 1855, 1. pp. 80, 357). bericht, fur 1858, p. 606). Principle IV. Decomposition of by solutions The behavior of the double salt towards solof ferric salts, while hydrate of iron is precip- vents has been studied in some detail by Divers, itated. (Compare the Carbonates of Barium (Journ. London Chem. Soc., 15. 196; Zeitsch. and Calcium): analyt. Chem., 1. 474), who appears, however, Application. Separation of Fe2%O from FeO to have been ignorant of' the labors of' Schaffin sulphuric acid solutions. gotsch and Weber. According to Divers, the Method. See Hydrate of Iron. In this pro- solution of normal carbonate of ammonium cess the normal carbonate (magnesite) must be may be made to contain 1 part of salt to 6 employed. The basic carbonate (magnesia- parts of water. About 4 equivalents of the alba) will not answer. carbonate of ammonium should be taken for BiCarbonate of Magnesium. each equivalent of magnesium to be precipi(Compare biCarbonate of Calcium). tated; and one equivalent or more of chljoride Carbonate of Magnesium and of ammonium should be mixed with the magof Am mon ur m. nesium solution before adding the precipitant, Principle. Sparing solubility in ammoniated in order to prevent the precipitation of any water. normal carbonate of magnesium. - The Application. Separatian of magnesium from composition of the double salt is MgO, CO; the alkalies. (NH4)2 0, O2 + 4H20. According to SchaA-: Method. Prepare an exceedingly concen- gotsch, 1 part of it requires 60,000 parts of a trated solution of the substance to be analyzed, solution of normal or Slightly alkaline carbonand in case it be acid, neutralize, or slightly ate of ammonium for its solution. It is somesupersaturate it with ammonia-water. Add to what soluble in a solution of chloride of amtie liquid a large excess of a solution of normal monium, when no carbonate of ammonium is carbonate of ammonium which contains rather present. Divers found 1 part magnesia in 4660 more than one equivalent of oxide of ammo- parts of a mother liquor which contained an nium for each equivalent of carbonic acid. To excess of carbonate of ammonium, some chloprepare this solution dissolve 230 grms. of corn- ride of ammonium and a large quantity of sulmercial, solid, sesquicarbonate of ammonium in phate of ammonium. 180 c. c. of ammonia-water of 0.92 sp. gr., and Carbonate of Manganese. enough water to bring the solution to the vol- Principle. Insolubility in water. ume of a litre. Stir the mixture strongly un- Applications. Estimation of manganese in til the voluminous precipitate which falls at all salts of that metal which dissolve in water, first, on the addition of' the carbonate of am- excepting the salts of some fixed organic acids; monium has completely re-dissolved. Then and in all compounds from which the mangaleave the mixture at rest for 12 or 24 hours. nese can be dissolved out by chlorhydric acid. Collect the crystalline precipitate upon a filter, Separation of Mn from Ca, Ba, Sr, Mg, Al, wash it with the solution of normal carbonate Fe, Zn, Cd, Pb, Cu, Bi and P205. of ammonium, dry, ignite, and weigh the Oxide Method. Place the moderately dilute soluof Magnesium. - In separating magnesium tion in a tolerably large beaker, cover the from sodium, the precipitate can readily be beaker with a watch-glass-shaped cover, at the washed free from fixed alkali; but if potassium centre of which a hole has been bored, and be present, some carbonate of potassium is re- heat the liquid. Pour a solution of carbonate tained by the precipitate so strongly that it of sodium, drop by drop, through the cover can only be washed out after the precipitate of the beaker until it is slightly in excess, has been ignited. The ignited magnesia must heat the mixture to boiling for a moment and consequently be washed with hot water in case afterwards allow it to settle until the liquid is potassium is present. clear. The original manganese solution should It is not absolutely necessary that the pre- be slightly acid, but not too acid lest some of,cipitate first formed should be completely re- the liquid be lost through the violent evolution dissolved, since when left to itself in the liquid of carbonic acid gas. - In case the manit gradually contracts and becomes crystalline; ganese solution contains any salt of ammo CARBONATES. 109 nium, a large excess of the alkaline carbonate But for every two atoms of chlorine evolved must be employed, and the mixture be boiled there must have been present one molecule of down nearly to dryness, until no more fumes sesquioxide of manganese:of ammonia escape, in order to ensure complete precipitation. The formation of dark Mn203 + 61C1= 2MnCl2 ~ 3H20 ~ 2C1. colored oxide of manganese during the evapo- To find the weight of the other metal deduct ration does no harm. During the evaporation the weight of the sesquioxide of manganese the cover of the beaker must be takein off: from the total weight of the mixed precipitate, Wash the precipitate by decantation with and, if need be, add to the difference the boiling water, dry the precipitate and ignite weight of the carbonic acid which was exand weigh as Manganite of Manganese (MnO, pelled by the manganese during the ignition. Mn2O,). In case the filtrate or wash water That is to say, for the metals Ba, Ca and Sr, from the carbonate of manganese is not abso- which retain carbonic acid on ignition, allow lutely clear, let it stand 18 or 24 hours in a one molecule of CO2 for every molecule of warm place and collect and wash the dirty Mn2O3. - As thus far described, excepting brown precipitate upon a special filter. When the case of iron or aluminum, the method carefully executed the process yields accurate presupposes that more than one molecule of results. MO is present for every molecule of Mn203, Properties. Recently precipitated manga- for if the proportion of MO were less than nous carbonate is a white flocculent substance, this the ignited precipitate would contain some scarcely at all soluble in pure water, but MnO, Mna03, as well as MO, Mn20O. The somewhat soluble in water which contains car- process may be made available. however, in bonic acid. It is no more soluble in salts of all cases by the following modification: Weigh the fixed alkalies than in water, but dissolves out half as much oxide of zinc at there is rather easily in ammonium salts. It cannot be supposed to be MO and MnO in the mixture, completely precipitated in presence of arnmo- dissolve it in chlorhydric acid, mix the solution nium salts, nor is it precipitable in presence of with the substance to be analyzed and precipcitric and other fixed organic acids. When itate the whole with carbonate of sodium. left moist in the air, or when washed with wa- The ignited precipitate will contain the whole ter which contains air, the precipitate slowly of the manganese in the form of Mn20s. takes on oxygen and becomes rusty through (Krieger, Annal. Chem. und Pharmn., 87. 261). formation of hydrated sesquioxide of manga- T9 separate manganese from phosphoric acid. nese. - When dried, out of contact with Fuse the weighed substance with carbonate of the air, the precipitate yields a white powder sodium for some time, boil the fused mass with of the composition MnO, CO2 -- +} Aq; but water, add a little sulphuretted hydrogen water when dried in the air the powder is always to reduce any manganic acid which may have more or less colored. When heated to redness formed, collect the insoluble carbonate of manin the air, the powder becomes black and ganese upon a filter and wash, dry, and weigh, afterward brown. By long continued ignition as above. it is completely converted into MnO, Mn2O3. Carbonate of Mercury. (MercuTo separate either of the metals above enu- rous carbonate)..nerated from manganese, precipitate the latter Principle. Insolubility in water and solutogether with the other metal by means of bility in nitric acid. carbonate of sodium, as above described. Applications. Estimation of carbonic acid Wash the mixed precipitate thoroughly, dry, in bicarbonates, especially as they occur in ignite and weigh. The ignited precipitate natural waters. Separation of bicarbonates of consists of a mixture of MO, Mn2O3 + x MO, the alkalies from those of the alkaline earths. or of MO, Mn203 + x (MO, C02), accordingly Use as an indicator in Acidimetry. as the carbonate of M is or is not decomposed Method. Prepare a solution of acid mercuby ignition. In case the metal precipitated, rous nitrate by digesting an excess of quicktogether with the manganese, is iron or alumi- silver with dilute nitric acid, pouring off the num, all the manganese will be in the form of mother liquor from the crystals of the basic Mn3O4. - Place a weighed portion of the salt, and diluting it with 4 or 5 parts of water. ignited precipitate in a small flask, together By leaving the solution in contact with metalwith some pure concentrated chlorhydric acid. lie mercury it may be preserved for a long Heat the mixture, conduct the chlorine, which time. When this solution is added to dilute is evolved, into a solution of iodide of potas- solutions of bicarbonates of the alkalies or slum and estimate the iodine, which is set free, alkaline earths, at temperatures lower than by means of hyposulphite of sodium. Or 300, a precipitate falls which is white at first, estimate the Chlorine in any appropriate way. but soon changes to yellowish-orange, or some(Compare Manganites, and Manganite of Man- times to yellowish-green. This precipitate ganese.) In case the method with iodide of dissolves in an excess of the acid mercurous potassium be used, the amount of iodine found nitrate, as well as in sulphuric and nitric acids will correspond, atom for atom, to that of the and in organic liquids, such as urine. Precipchlorine set free from the chlorhydric acid. itates obtained, under analogous conditions, 110 CARBONATES. from the normal carbonates are brown and Method. Same as that described under Carinsoluble in an excess of the mercurous nitrate. bonate of Cobalt. Prepare a standard solution of' bicarbonate Princip e J1. Insolubilitv in water.,of potassium by dissolving 0.5 grin. of the bi- Method. Salmne as that described un(er Carcarbonate in water to the volume of a litre. bonate of Copper. TLiM?T'uen baIsic ci(rbonate'This quantity of' the bicarbonate is equivalent of nickel, obtained by boiling the dilute soluto 0.241 grin. of carbonic acid. Standardize tion of a nickel salt with an alkaline carbonate,:a quantity of the mercurous nitrate by pouring may be'ashed much more readily than the:it, drop by drop, fi-om a Gay-Lussac burette precipitate obtained by means of a caustic aliinto measured portions of the standard solu- kali. According to Gerith, the process yields tion of bicarbonate of potassium, until the highly satisfactory results. (Gibbs & Taylor, precipitate which forms at first has completely American Journ. Sci., 1867, 44. 214). redissolved. Repeat the titration two or three Carbonate of Potassium. [Comtimes with different quantities of the bicarbon- pare Carbonate of Sodium]. ate solution until the results agree. Then Principle I. Fixity of the salt at moder — titrate the bicarbonate, or the water, to be ately high temperatures. -tested, in the usual way. (See Acidiinetry). Applications. Estimation of potassium in In order to separate alkaline bicarbonates many potassium salts of organic acids. Valufrom bicarbonates of the alkaline earths, pro- ation of argol and cream of tartar..ceed as above, with one portion of water to be Mlethod. Heat the salt gently for a long tested. Then boil another portion of 100 c. c. time in a covered platinum crucible, until abuntil the carbonates of the alkaline earths solutely no more visible futmes escape. Wash have all been thrown down, filter, add water out the black porous residue from the crucible to the filtrate to replace what has evaporated, into a beaker, cover the latter with a watch saturate the filtrate with carbonic acid and glass, and add dilute chlorhydric acid to titrate with the mercurous solution to deter- the solution as long as there is any effervesmine the proportion of alkaline bicarbonate. cehice. Filter the acsidulated liquor, to sepOr, add to a measured quantity of the water, arate the particles of carbon, evaporate the a measured volume of standard caustic potash filtrate in a platinum cup and weigh the Chlo(0.5 grm. to the litre) sufficient to change the ride of Potassium. Or, instead of chlorhydric bicarbonates of the alkaline earths into neutral acid, use dilute sulphuric acid, and weigh as salts, let the mixture stand for several days, Sulphate of' Potassium. In sonle cases, as in decant the clear liquid, saturate it with cai'- the examination of' tartar, it will be most conbonic acid and titrate as before. Subtract, of venient to estimate the potassium in the car-,course, the bicarbonate of potassium which has bonate by the method of alkalimetry (see below, resulted froln the caustic alkali employed. Principle II). The presence of sulphates or chlorides in The carbonate of potassium in the crucible the water inter'feres materially with the success must never be heated to the point of fusion, of the process, but when the proportion of and the crucible should be kept covered chlorine is not too large the bicarbonates can throughout the operation, If the crucible were still be determined approximately, as follows: — left open and the residue roasted until it beMIeasure out several portions of 100 c. c. each, came white, a considerable quantity of carbonof the water, acidulate them with nitric acid, ate of potassium would be lost through volaand observe about how many drops of the stan-. tilization. A small proportion of the potassium dard mercurous nitrate are required in order is usually lost in this way during the process of to precipitate the chloride and impart a defi- carbonization, but the process nevertheless nite gray coloration to the liquid. By trying yields perfectly satisfactory results when propseveral experiments it is easy to hit this point erly conducted. If' the process of heating be with sufficient accuracy. Then add the stan- continued long enough a colorless solution will dard mtercurous nitrate to a fresh, non-acidu- be obtained when the residue is treated with lated 100 c. c. portion of the water, until. the water. (Braun, Zeitsch. analyt. Chem., 1868; yellowish-orange precipitate has disappeared 7. pp. 149, 150). See also Aug, Vogel (ibid. and the liquid has acquired the gray coloration p. 1-49) for quantitative experimlents, showing aforesaid. - Since the nmercurous nitrate the large amount of carbonate of potassium acts upon caoutchouc, it cannot be used with which may be lost by volatilization. - It Molhr's burette unless the latter be provided is not well to burn the coaly residue white by with a glass cock or regulated by a clip at the throwing in fragments of nitrate of' ammonium top. (Barthdlemy, Zeitsch. analyt. Chem., (as directed by H. Rose), because of the great 1869, 8. 91). heat which would be produced by the combusCarbonate of Nickel. tion. Nor is it advisable to use nitric acid Prinlcple I. Solubility in an aqueous solu- instead of chlorhydric, as the solvent of the tion of cyanide of potassium. carbonate. Applications. Separation of Ni from Ba, Sr, In some rare cases it may be best to weigh Ca and Al. carbonate of potassium as such, though, on ac CARBONATE OF POTASSIUM. 111 count of its tendency to deliquesce, the salt is Since both silicate and phosphate of potasnot well adapted for weighing. In that event, sium have an alkaline reaction and behave to evaporate the solution to dryness in a platinum wards acids like the carbonate, the, method o crucible and ignite the residue at a moderate alkalimetry by neutralization is incompetent to heat. A few small fragments of solid carbon- distinguish them from the carbonate; but they ate of ammonium may be placed in the crucible do not interfere in any way with those methods before the final ignition, in order to convert of analysis which depend upon the volatilizainto carbonate of potassium any traces of caus- tion and quantitative estimation of the Cartic potash which may be present. It is to be bonic Acid in the sample. - According to observed that in igniting carbonate of potas- Persoz (Comptes Rendus, 53. 239), the influsium in contact with carbon, some of the car- ence of sulphites, sulphides, and hyposulphites bonic acid is decomposed, carbonic oxide being may be avoided, so long as the sample is free set free and caustic potash produced. This from carbon or organic matters, by using his decomposition occurs particularly when the method of fusion with bichromate of potassium carbonate of potassium is heated to fusion in (see p. 80). Fresenius destroys the sulphur contact with charcoal. The crucible in which compounds by igniting the weighed sample of carbonate of potassium is weighed should have carbonate with chlorate of potassium, before a tight cover, to hinder the salt from absorbing proceeding to the treatment with acid. The water from the air during the operation of sulphur compounds are thus changed to inert weighing. All trouble fiom deliquescence may'sulphate of potassium. But if any hyposulbe avoided, however, by igniting the carbonate phite be present, an equivalent quantity of the with chloride or with sulphate of ammonium carbonate will be destroyed by its oxidation. and weighing as Chloride or Sulphate of Potas- (See Carbonate of Sodium). sium, as the case may be. For methods of determining the proportion Principle II. Power of neutralizing acids. of caustic and carbonate of potassium, in a Applications. Estimation of potassium in mixture of the two, like many samples of the commercial carbonate; in other words, American potash, see under Alkalimetry. valuation of pearlash, saleratus, potashes and In case the carbonate of potassium to be wood ashes. Valuation of argol and cream of examined is contaminated with carbonate or tartar. hydrate of sodium, the proportion of potasAMethods. The proportion of pure carbonate sium in the mixture may be estimated by one of potassium in any given sample of the comr- cf the methods referred to at the close of the mercial article may be estimated, either by de- article Alkalimetry. According to Fresenius, termining how much of a standard acid can the following process yields accurate results, be neutralized by a weighed quantity of the and is tolerably expeditious: - Dissolve in sample (see Alkalimetry), or by determining water 6.25 grin. of the ignited pearlash, filter how much carbonic acid is set free when a the solution into a quarter-litre flask, add weighed quantity of the sample is mixed with acetic acid to slight excess, and warm the a weighed quantity of acid or fused with an liquid to expel carbonic acid. After the caracid salt (see Carbonic Acid, volatility of, bonic acid has been driven off, add a solution.lethods C and B; also p. 22). of acetate of lead, drop by drop, to the hot The commercial carbonates of potassium are liquor until the formation of a precipitate of liable tocontain substances insoluble in water,- sulphate of lead just ceases. Allow the mixsuch as carbonate, silicate, and phosphate of ture to cool, fill the flask with water to the calcium, sand, and dirt, which may be removed mark, shake the mixture and tlhen let it stand by filtration; and neutral salts, such as the al- to settle; filter through a dry filter, and transkaline chlorides and sulphates, which lhave no fer 200 c. c. of the filtrate, corresponding to 5 influence whatsoever in the process of titration. grms. of the pearlash, to a quarter-litre flask. But, besides these harmless ingredients, there Fill the flask to the mark with strong sulphurmay be present certain other compounds,- etted hydrogen water and shake its contents. such as the hydrate, silicate, phosphate, sul- If the acetate of lead was carefully added the phite, sulphide and hyposulphite of potassium,- fluid will now smell of sulphuretted hydrogen which must be guarded against in certain cases. and be free from lead. In case the liquid does [Compare Carbonate of Sodium]. -- In many not smell of sulphuretted hydrogen a stream cases it will be sufficient to determine the of that gas must be passed through it. After amount of"available alkali" in the sample, with- the sulphide of lead has subsided, filter the out reference to its precise chemical composi- liquid through a dry filter; place 50 c. c. of tion. For example, if the commercial article the filtrate, corresponding to 1 grm. of the under examination is to be used for making pearlash, together with 10 c. c. of chlorhydric caustic potash by boiling the aqueous solution acid, of 1.1 sp. gr., in a weighed platinum dih, with lime, the presence of a small quantity of and evaporate the mixture to dryness. Corer silicate or of phosphate of potassium will do the dish, heat the mixed chlorides moderately, no harm, any more than that of caustic potash, and weigh them (see Chloride of Potassium). since both of these compounds will be made The weight obtained expresses the amount of caustic by the lime, like the carbonate itself. chloride of potassium plus chloride of sodium 112 CARBON ATE OF SILVER. given by 1 grm. of the pearlash. Determine what, dry it by heat in a silver or porcelain the chlorine by titration (see Chloride of' Sil- dish, and preserve the powder in well stoppered ver) and calculate the amounts of potassium bottles. The product should be white, and and of sodiuini as described under Chloride of should give no reaction for silicic, sulphuric, Potassium. For a similar calculation see Car- chlorhydric or phosphoric acids when evapobonic Acid, indirect separation of calcium from rated with chlorhydric acid, or tested with strontium. acidulated chloride of barium, nitrate of silver In case it is desired to know how much of or molybdate of ammonium. It should give no any sample of pearlash consists of foreign salts, reaction for iron when tested with sulphocydetermine the Water contained in it, by gently anide of potassium. heating a weighed quantity (8 or 10 grms.) in A mixture of 13 parts of carbonate of potas-a covered platinum dish fbr a long time, until sium and IO parts carbonate of sodium is prefdew ceases to be deposited upon a piece of cold erable to either of its components for decomwindow glass held over the dish. The loss of posing silicious minerals, by way of fusion, weight will give the proportion of water. The since the mixed carbonates melt at a lower difference between the percentage of water temperature than either of the carbonates plus the percentage of carbonate of potassium, taken separately. Most refractory silicates as above determined, and 100, will give the may be decomposed by fusing them with the percentage of fix.ed impurity in the substance mixed carbonates over an ordinary Berzelius analyzed. lamp or simple Bunsen's burner. (See SiliIn the examination of ashes, or of liquors cates). Instead of mixing the pure carobtained by leaching ashes, it is w, to weigh bonates directly, the mixture may be prepared out or to measure 10 or 12 times as much ma- either by igniting pure Rochelle salt and lixivterial as has been directed under Alkalimetry, iating and evaporating the residue, or by desincethe proportion of alkali in ashes is com- flagrating. a mixture of' 20 parts pure bitartrate paratively small. of potassium, prepared as above, and 9 parts For use as a reagent, pure carbonate of po- of pure nitrate of sodium, and proceeding as tassium may be prepared as follows:-Heat a above described. mixture of 10 parts of pulified powdered cream BiCarbonate of Potassium. See of tartar, 10 parts of water, and 1 part of pure biCarbonate of Sodium. Compare biCarstrong chlorhydric acid for several hours upon bonate of Calcium..a water bath, stirring the mixture frequently. Carbonate of Silver. Place a small filter in the throat of a capacious PrYi-nciple 1. Power.of neutralizing acids. funnel, pour the mixture into the funnel, and Application. Precise neutralization of nitric let the liquid portion drain away. Level off acid liquors for the purpose of precipitating the top of the solid matter in the funnel, and phosphate of silver, as a means of separating press down upon it a disk of compact filter phosphoric acid from alkalies, alkaline earths, paper turned upwards at its edges. Pour re- etc. peated small portions of cold water (iced water Mlethod. See Phosphate of Silver. -- If is best) upon the filter paper,-in order that a phosphate insoluble in water is dissolved in all the chloride and phosphate of calcium and a slight excess of' nitric acid and the solution any chloride of' potassium which has been mixed with nitrate of silver, no precipitate will formed may be removed by percolation,- until fall. But, by agitating the solution for a few a drop of the filtrate ceases to become cloudy moments with a slight excess of carbonate when acidulated with nitric, acid and tested of silver, it is easy to neutralize the acid and with nitrate of silver. Then dry the purified so cause the complete precipitation of the phostartrate. phoric acid (as phosphate of silver) without Prepare on the other hand, a quantity of introducing any new or hurtful reagent. (Chanpure Nitrate of Potassium, and dry it. Mix 2 cel, Conmptes Rendus, 1859, 49. 997). parts of the pure tartrate of potassium with 1 For the use of carbonate of silver for decompart of the pure saltpetre; see to it that the posing various chlorides, as one step in Grfagmixture is completely dry; and project the' er's method of' estimating combined sulphuric mixture by small portions into a clean, bright, acid, see Chloride of Silver, insolubility of' wrought iron pot heated to low redness. As Principle II. Solubility in ammonia-water, soon as the last portion has deflagrated, heat and insolubility in water. the contents of the pot strongly until a sample Applications. Separation of CO2 from S20. of the carbonate taken from the edge of the and H2SO4, in the analysis of gunpowder mass yields a perfdctly colorless solution with residues. water. Then rub up the coaly mass with wa- Method. After all the sulphur which was ter, filter, wash the residue slightly and evap- in the form of an alkaline sulphide has been orite the filtrate in a porcelain, or better, a removed as Sulphide of Cadmium, by digestsilver dish, until it is covered with a permanent ing the solution with carbonate of cadmium crust. Stir the liquor constantly while it cools, and filtering, heat the filtrate from the suland throw the crystalline meal into a funnel as phide of cadmium, mix it with a neutral befbre; allow the meal to drain, wash it sonme- solution of nitrate of silver and collect the CARBONATE OF SODIUM. 113 precipitate upon a filter. The precipitate con- covered crucible; the residue is digested in sists of a mixture of carbonate and sulphide of water and the solution filtered and evaposilver, for rated, with addition of a small quantity of K20, 502 + Ag2O, 5N205 -= K20, SO3 -~ A~g+ N2Or carbonate of almmonium to revivify any caustic soda which llay have been formed during while the whole of the sulphuric acid will the process of carbonization. remain in solution, and may be determined in Chlorid and nitate of soium may be conthe filtrate as Sulphate of Barium, after the verteil into time carbonate by mixing their excess of silver has been removed by means aqueous solution witll a moderate exees of of chlorhydric acid. - After washing the oxalic acid, and evaporating the solution to precipitate, digest it in amnmonia water to (is- dryness. Water must be added to the dry solve the carbonate of silver; then acidif)' the residue and the process of evaporation se elm;l solution with nitric acid and estimate the sil- times repeated. All of the sichlorhydric acid ver as Chloride of Silver. Each equivalent of is driven out, an(l the nitric acid as well, while chloride of silver obtained will correspond to a portion of the latter undergoes decomposian equivalent of carbonic acid,tbut from this an euvalent of carbonic acidut om tion. The residue is finally ignited to destroy amount must be subtracted the carbonic acil the excess of oxalic acid, and the carbonate of' derived from the carbonate of cadmium pre- soclium is weighed. viously employed fbr decomposing the sul-'The dry carbonate is white phide of' potassium, since and tolerably permanent; when left in the K 2S + cdO, CO2= CdS + x20, CO2- air for any length of time, however? it slowly (W\erther, Journ. prakt. Chem., 55. 22). absorbs a certain quantity of' water. It fuses Accordin(g to Fedorow (Zeitsch. analyt. at a strong red heat, and if kept in the flui(l Chenm., 1870, 9. 127). the foregoing process state for any length of time, an appreciable is not based upon correct principles, since on quantity of it is lost by volatilization. It precipitating a hyposulphite with a solution of scarcely loses weight, however, when ignited silver, a certain quantity of acid is set tiee, moderately, or even when heated to incipient and a proportional quantity of carbonate of' fusiol. Carbonate of sodium is much less silver dissolved. soluble in dilute ammonia water than in pure For use as a reagent, carbonate of silver water, andlll is scarcely at all soluble in strong may be readily prepared by adding a sorution alcohol. The composition of' the lnhydrous of carbonate of ammonium to one of nitrate salt is: of' silver. The precipitate may be washed 2Na = 40 = 4.40 with water by decantation. It is neither necw- c = 12 = II-.2 essary to filter nor to dry it, since it acts best l4.52 when moist. Carbonate of Sodium. IPrilciple II. Power of neutralizing acids. Princi)le I. Fixity of' the salt when heated. ilpplications. Estimnation of' sodium in thl Applications. Estimation of' sodium in the commercial carbonate and bicarbonate. Valhydrate, bicarbonate, nitrate and chloride of' uation of soda-ash, black-ball, sal-soda, salsodium, and in organic salts of' that metal. eratus, etc. Assay of' sulphur in iron- and The process is one of' far more general appli- copper-pyrites (sulphur ore). cability than the corresponding method, which Mlethods. See Carbonate of Potassium. depends on the fixity of carbonate of' potas- Soda-ash generally contains, besides carsiu71. bonate of' sodium, a certain proportion of Method. In the case of a simple solution of hydrate, sulphate and chloride of' sodium; carbonate of sodium, evaporate to dryness in some traces of' silicate, aluminate and cyanide a platinum dish, ignite moderately and weigh. of sodium; and not infi'equently, appreciable Since the ignited carbonate is not deliquescent quantities of sulphide, sulphite and hyposulit is easy to obtain accurate results in this phite of' sodium. - The three substances way, but care must be taken, nevertheless, last named are specially objectionable, inasnot to heat the carbonate too strongly, lest much as they neutralize the stcndard acid anil some of it be lost by volatilization (compare pass for carbonate of' sodium, while so far fromn Carbonate of Potassium); carbonaceous imat- having any value, considered as alkalies, they ter and reducing gases, moreover, must be are really hurtful..To detect their presence kept out of the crucible. - Bicarbonate of proceed as follows: - Mix a portion of the sodium is treated like the carbonate. But the ash with dilute sulphuric acidl, and observe, crucible must be kept covered and the heat whether any odor of' sulphuretted hydrogen carefully regulated while the excess of car- can be perceived. Color a quantity of dilute. bonic acid is being driven off. - Caustic sulphuric acid with a drop or two of a solution soda is treated with an excess of carbonate of of' permanganate of potassium, and add to the ammonium, the mixed solution is evaporated liquor a quantity of' soda-ash, insufficient to at a gentle heat and the residue ignited. neutralize the acid. If the liquor becomes Compounds of sodium with organic acids green, or if its purple color is destroyed, are ignited like Carbonate of Potassium, in a either sulphite or hyposulphite of sodium is 8 114 CARBONATE OF SODIUM. present; but if the permanganate retains its sulphur. The process requires only 30 or 40 color, both of these salts must be absent. The minutes for its completion, and yields results presence of hyposulphite of sodium may be which differ only about 1 to 1.5 per cent from made still more manifest by saturating a clear the truth. - The whole of the sulphur is solution of the soda-ash with chlorhydric acid, converted into sulphate of sodium or potasand noting the odor of sulphurous acid, which sium, and no sulphurous acid escapes during is given off, as well as the turbidity due the process of oxidation. In order to be sure, to the precipitation of' sulphur. These im- however, that the washed insoluble residue is purities can be destroyed by igniting the ash free fiom sulphur, it is well to test it with with chlorate of potassium, and so converting chlorhydric acid. It is to be observed that all the sulphur into the condition of sulphuric any loss of carbonate of sodium through volaacid before proceeding with the titration; tilization, projection, or insufficient washing, though the method is not wholly satisfactory will tend to make the amount of sulphur when hyposulphite of sodium is present, inas- appear larger than it really is. The purpose much as some carbonate of sodium will then of the chloride of sodium is to moderate the be decomposed, in accordance with the reac- action of the chlorate; the proportion of the tion: — chloride may be varied for the rest, according Na2O, CO2 + NaO, S202 + 40 = 2(Na,0, SOs) + CO2. to the quality of the pyrites, and increased so The presence of silicate or aluminate of that the oxidation may occur without deflagrasodium will usually be indicated by the forma- tion, or any appearance of incandescence. In tion of a precipitate when the carbonate is case pyrites-residues are to be analyzed, the neutralized withl acid. As a general rule, chloride of sodium had better be omitted altohowever, the quantity of these impurities is gether; the mixture may then be made of 5 so small that they need not be noticed in tech- grmins. roasted pyrites, 5 grms. carbonate of nical estimations; the hydrate of sodium. also, sodium, and 5 grins. chlorate of potassium. is often estimated as if it were carbonate, The presence of quartz, heavy spar or limethough all of these contaminations have to be stone in the pyrites, does no harm. - Inestimated and allowed for whenever the pro- stea(l of using absolutely pure carbonate of portion of pure carbonate of sodium in the sodium it will be sufficient to use that obtained sample is to be determined. - In case it is by igniting the commercial bicarbonate, and to desired to know the proportion of inert solid determine once for all, by titration, the promatter in the sample, as distinguished fiom portion of pure carbonate contained in it. the water which is contained in it, the water Principle III. Power of decomposing or must be estimated and allowed for, as directed of combining with many silicates, sulphates, under Carbonate of Potassium. chlorides and oxides, when fused therewith. To estimate Sullhur in Pyrites, and in the In decomposing silicates it is usual to mix residues left by roasted pyrites, Pelouze the finely powdered mineral with 4 times its (Comnptes Rendus, 53. 685) proceeds as fol- weight of carbonate of sodium, and to fuse lows: - Weigh out about 1 grin. of very finely the mixture over a blast lamp or in a furnace. powdered pyrites, add to it an accurately Basic silicate of sodium is formed while the weighed quantity of pure anhydrous carbon- silicates in the mineral are rendered basic and ate of sodium (about 5 grins.), and carefully decomposable by acids. (See Silicates). mix the materials with a mixture of 7 grins. of For the method of decomposing chlorides, chlorate of potassium and 5 grins. of dry see Chloride of Silver; of sulphates, see Sulchloride of sodliuml, whllich have been weighed phate of Barium. roughly upon a coarse balance and rubbed Alumina may.be separated from small quantogether in a mortar. Heat the mixture in a tities of the alkaline earths and of manganese, wrought iron spoon during 8 or 10 minutes, so such as often contaminate the Hydrate of that it shall gradually be brought to dull red- Aluminum drawvn down by ammonia, by fusness. Allow the melted mass to cool, treat it ing the dry precipitate with 10 or more times 5 or 6 times with hot water, throw the solution its weight of' dry carbonate of sodium over a upon a filter, boil the residue with water, and powerfhl blast lamp, until no more bubbles of wash it upon the filter with boiling water. carbonic acid are seen to escape from the Bring the filtrate and wash-water to some melted mixture. The alumina precipitate definite volume (see Alkalimetry), and by need not be powdered, but the fision should means of a standard acid titrate the carbonate last from three-quarters of an hour to an hour. of sodium in a measured portion of the liquor. Add a little caustic soda to the cold, fused The difference between the weight of carbon- mass, and boil it with water, best in a silver ate of sodium taken and that found in the dish, until the soluble matter has all dissolved. matter resulting from the process of oxidation, In case the solution has a green color, from gives the amount of carbonate of sodium which the presence of manganate of sodium, it has been decomposed by the sulphuric acid should be boiled with a little alcohol to reformed from the sulphur in the pyrites. Each duce the manganate. Filter off the soluble equivalent of carbonate of sodium thus de- aluminate of sodium, and wash the precipitate, stroyed corresponds with one equivalent of first with water charged with caustic potash, BICARBONATE OF SO1)IUM. ll) and then with pure water. (R. Richter, well to turn over the cake in the crucible, in Journ. prakot. Chem., 64. 378). Compare order that all of its surfaces may be thorAluminate of Sodium. oughly heated. (Schaffgotsch, Poqgg..1 irnallen, For use as a reagent. pure carbonate of 113. 615.) The composition of carbonate of sodium may be prepared from the comnllercial strontium is:bicarbonate, by washing the latter by percolation with ice-water upon a funnel, as (le- CO3 = 00.0 = 40.08 scribed under Carbonate of Potassium, and 147. 0 igniting the dried residue. The process of percolation must be continued until a portion Principle II. Insolubility in water. of the filtrate, after having been acidulated Applications. Estimation of strontium in with nitric acid, yields no turbidity when soluble strontium salts. Separation of Sr tested with the nitrates of silver and of barium. fronm K, Na, Mg and Mn. The precipitation The washed and dried bicarbonate must be of strontium as carbonate is to be preferred to ignited gently, best in a dish or crucible of the estimation of that metal as a sulphate, silver or platinum, though in default of these whenever the addition of alcohol to the solua clear, bright, iron dish, or dish of Berlin tion is inadmissible, and the strontium to be porcelain may be employed. When solutions determined is combined with a non-volatile of the salt are needed, or the crystallized salt acid. itself, it is sufficient to recrystallize commercial Method. Same as that described under sal-soda, repeatedly. The solution should yield Carbonate of Barium. The results are acno insoluble residue of silica when evaporated curate, since carbonate of strontium is alto dryness after saturation with chlorhydric most absolutely insoluble in water charged acid; nor should it give any reaction fbr iron with ammonia and carbonate of ammonium. or fr phosplloric, sulphuric or clhlorhydric The presence of ammonium salts, moreover, acid, when tested with sulplhocyanide of' po- is less hurtful in the precipitation of carbonate tassiuml, mnolybdate of amnlnonium, chloride of of strontium than in that of carbonate of babariuml or nitrate of silver. rium. By direct experiment, Fresenius fobund BiCar!bonate of Sodiurm. [Coml- 99.82 instead of 100 parts of strontia. As pare biCarbonate of Calcium]. with carbonate of barium, care must be taken For the use of bicarbonated alkalies for that the solution is free from substances likely decomposinllg and partially dissolving certain to prevent the precipitation of the carbonate. sulphates and chlorides insoluble in water, see For the separation of mang:lncse and stronSulphate of Lead and Chloride of Lead. tium see Carbonate of Manganese. Carbonate of Strontium. Properties. Dry, precipitated carbonate of Principle 1. Fixity when not too strongly strontium is a white powder soluble in about heated. 18,000 parts of water at the ordinary temperaApplijcations. Estimation of' strontium in ture, and in about 57,000 parts of water, whlich organic salts of that metal, and all compounds contains ammonia and carbonate of ammonium. of strontium which are soluble in water. (Fresenius.) It is sensibly less soluble in wa(Compare below, Principle II). ter than sulphate of strontium. (Dulong; H. letlhod. Same as that described under Rose.) It is rather easily soluble in solutions Carbonate of Barium. - Carbonate of of chloride or nitrate of ammonium, but is reStrontium may be heated to low iredness with- precipitated on addingl anmmonia and carbonout losing any of its carbonic acid. When ate of ammonium. Carbonic acid water disheated to intense redness, or lmoderate white- t sol es it, and the solution has a feeble alkaline ness, -— as when ignited over a good gas blast reaction. It is not precipitated in presence of lamp, even when not enclosed in a clay cylin- an alkaline citrate or metaphosphate. der, -it gradually gives off the whole of its Principle 111. Insolubility in a solution of carbonic acid. (Compare Carbonic Acid, in- cyanide of' potassium. direct separation of' strontium and calcium). Applications. Separation of Sr from Co, Ni When heated to redness in contact with car- and Zn. bonaceous matter, some carbonic oxide is set Miethod. See Carbonate of Cobalt. free and caustic strontia forlned. The latter Principle 1 V. Power of neutralizing acids. may be revivified by adding, a solution of' Application. Estimation of strontium in carbonate of' lamlonium and evaporating as the carbonate. directed under Carbonate of Calciumr. In 1Mle/hods. Similar to those described under case the quantity of Carbonate of' Strontium Carbonate of Barium. in the crucible is small, it may be ignited in- Carbonate of Zinc. tensely at the blast lamp and weighed as Oxide Principle I. Insolubility in water. of Strontium. In that event the carbonate Applications. Estimation of zinc in all zinc should be made as compact as possible; it salts which are soluble in water; in those should be precipitated ftom a hot solution which dissolve in chblorhydric acid, with sepand pressed tightly into the crucible. After aration of their acid; and in all those with the mass has been ignited for somle time it is volatile organic acids. Separation of Znl from 11B CARBONATE OF ZINC. Na, K, AMn and Va. Estimation of CO2 in ing with hot water. In case any other submineral waters. stance is to be determined in the filtrate, it Mlethod A. Similar to that described under will be best to mix the latter with sulphydrate Carbonate of -Manganese. The precipitation of animoniumn, to collect and weigh the Sulshould be made in a tolerably.capacious beak- phide of Zinc, and add the weight of zinc thus er, not more'than one-third full of' the zinc found to that obtained as carbonate. solution. The liquid should be heated nearly Precautions. The original solution of zinc to boiling before adding any of the carbonate should be firee from any great excess of acid, of sodium, and be kept at that temperature, in order that no unnecessary effervescence or at actual boiling, throughout the experi- need occur on the addition of carbonate of ment. At a certain moment, however, dur- sodium. The liquor must be heated during ing the addition of the carbonate of sodium, the precipitation, since a portion of the zinc the mixture is liable to suddenly fioth vio- would fail to be precipitated at the ordinary lently, fromr the escape of a torrent of carbonic temperature, at least from a solution of the acid, while a quantity of basic carbonate of sulphate or chloride, and the mixture must zinc is thrown down. The lamp must of finally be boiled to expel the free carbonic course be removed at this instant. It is to acid ftrom the solution, and so prevent it from prevent the liquid from boiling over when dissolving some of the carbonate of zinc. thisl momentary violent reaction occurs, that But on the other hand, the boiling must not the beaker must be large and the source of be too long continued lest some of the preheat carefllly watched and regulated. Boil cipitate be decomposed by the sulphate or the mixture freely for a few minutes after all chloride of sodiumn, with f'ormation of carbonthe zinc has been precipitated; then decant ate of sodium, and an insoluble basic sulphate the liquid into a filter and wash the precipi- or chloride of zinc. These basic salts would tate thoroughly with boiling water; at first by not be wholly decomposed on ignition, except decanting two or three times from the beaker, at a very high temperature. Even when the and afterwards upon the filter itself: Dry, carbonate is precipitated from a nitric acid ignite in a platinum crucible and weigh as solution, it may retain some nitric acid, but it Oxide of Zinc. The carbonate of zinc must loses it readily when ignited. (H. Rose). be rubbed off' from the filter as completely as Instead of operating in the wet way, as possible befobre the latter is burned, and care above, the dry zinc salt may be heated caumust be taken to burn the filter in such man- tiously to near redness with an excess of earner that it cannot reduce any of the oxide of bonate of sodium in a platinum dish, and the zinc. - In case the zinc solution contains residue treated with water, with the precauany salt of ammlllonium the boiling mlust be tions above enjoined. This modification of continued after the addition of' the carbonate the process is specially to be commended when of sodium, until all the ammonia is expelled, the compound to be analyzed contains an amand the steamn no longer turns turmeric paper monium salt. (Johnson). brown. The precipitation will never be corn- 1Method B. As a modification of the usual plete until the last trace of ammonia has been method, E. Jacob (Zeitsch. analyt. Chlem., driven off. Hence, if the proportion of' an- 1865, 4. 212) has proposed the following: — monium salt be large it will be best to boil Heat the somewhat acid zinc solution to 600 down the mixture to dryness. (Compare Car- or 80~ C.; carefully pour into it a solution of bonate of' Magnesium). Even when this has carbonate of sodium until, after the lapse of a to be done the process is much to be preferred few seconds, the cloudiness which forms after to the one depending upon the insolubility of,each addition of the alkali ceases to disapSulphide of Zinc. Care nmust be taken to pear, and the carbonic acid escapes tranquilly. treat the dry residue with boiling water, since Then pour in an excess of the carbonate of cold water would dissolve a part of the zinc in sodium and boil the mixture. the formn of' a double carbonate of zinc and By proceeding in this way the carbonate of sodium. - The process yields excellent zinc is precipitated completely as a conipararesults in spite of the fact that a decided trace tively comln)act powder, f:ar more easily washed of' zinc always escapes precipitation. On test- and dried than the light flocculent precipitate ing the filtrate fiomn the carbonate of' zinc obtained by the ordinary process. According with sulphydrate of ammoniuim a slight pre- to Jacob, no basic salt is formed in his process. cipitate of' sulphllide of zinc will invariably be It is to be remarked in this connection, that obtained, especially when the mixture is left to H. Rose has always directed that the zinc stand for an hour or two. It is to be inierred, solution be mixed with an excess of carbonate therefore, either that these flocks of sulphide of' sodium and then heated to boiling. In are well-nigh imponderable, or that the pre- sonme of the earlier editions of his Handbuch, cipitated carbonate retains enough sodium, or lie suggests that the zinc solution had better other foreign substance, to compensate for the be poured into a warm solution of' the alkaline lost zinc. It is admitted, however, that the carbonate, since in that case we may be sure carbonate thrown down, as above described, that no basic salt would be precipitated. may be completely freed from alkali by wash- To separate zinc from vanadic acid, Czud CASEIN. 117 nowicz (Zeitsch. analyt. Chem., 1864, 3. 379) good as insoluble in water. According to directs that the acid solution should be heated Fresenius, one part of the precipitate d(issolves with oxalic acid, or some other reducing in about 45,000 parts of water. It is soluble, agent, to bring the vanadic acid to the con- however, in carbonic acid water, and readily dition of protoxide, and the solution then soluble in solutions of the fixed caustic alkadigested for a long time with carbonate of lies, and of carbonate of' ammoniumn, ammllonia sodium. In case all the vanamdium is in the water an(l acids. A concentrarted solution of state of protoxide, the zinc will be precipitated zincate of potassium or of' sodium is not alfiee from any trace of that metal, but in case tered by boiling, but by boiling a dilute soluthe reduction were incomplete the carbonate tion nearly all the oxide of zinc can be thrown of zinc would be dark-colored. In that event down. In the solutions in ammonia or carthe moist, washed precipitate must again be bonate of ammonium a precipitate is likewise dissolved in chlorhydric acid, the solution formed on boiling, especially if the solution be again re(luce(l and the zinc afterwards repre- dilute; such a solution would of' course be cipitated with carbonate of sodium. decomposed with evolution of carbonate of For the method of separating zinc from ammonium, when boiled with carbonate of manganese see Carbonate of Manganese. sodium. With regard to the estimation of carbonic As has been already stated, the precipitate acid in mnineral waters, Bj6rklund (Zeitsch. obtained by Method A is not normal carbonanalyt. Clhem., 1865, 4. 229) finds that free ate of' zinc, since mbre or less carbonic acid is carbonic acid can be completely absorbed from given off during the precipitation, even after an aqueous solution by digesting( the latter all the free acid in the original solution has with oxide of' zinc. To apply the method been neutralized. The proportion of hydrated quantitatively, Bj6rklund adds from 4 to 10 oxide of zinc in the precipitate varies, howgrins. of oxide of zinc to a litre of' the mimn- ever, considerably, according to the degree of eral water, accordingly as there is more or concentration of the solutions employed. and less carbonic acid to be absorbed, and lets the the details of the manipulations. - When mixture digest during at least 24 hours. The dried, the precipitate fornms a loose white bottle which contains the water should be com- powder, from which all the carbonic acid is pletely filled with liquid, since the oxide of readily expelled at a red heat. zinc has little or no power to absorb any Principle II. Solubility in an aqueous socarbonic acid which might escape into the air lution of cyanide of' potassiumn. of the space above the liquid in a bottle in- Applications. Separation of Zn from Ba, completely filled. Since the oxide of' zinc is Sr. Ca, Mg and Al. apt to acquire a crystalline. consistency after Method. Same as that described under all the carbonic acid has been absorbed, it is Carbonate of' Cobalt and Cyanide of Cobalt. well to wait for this appearance. The mixed Boil the filtrate with chlorhydric acid, to oxide and carbonate may then be collected which a little nitric acid has been added. in with peculiar ease. order to expel the cyanhydric acid, and throw Carbonic acid cannot be absorbed, however, down the zinc as Carbonate, with the precauin this way by oxide of zinc, when it exists as tions enjoined for the case where ammonium a neutral salt in combination with either of salts are present. the alkali-metals, or with calcium, magnesium Carmine. See Cochineal. or iron; or as a bicarbonate of an alkali. Carthamin and Carthamic From a solution of' carbonate of calcium in Acid. See Safflower. carbonic acid water, oxide of zinc absorbs the Casei n. [Compare MIilk.] excess of carbonic acid so that neutral car- Plrinciple I. Coagulability by acids. bonate of' calcium is precipitated; a similar Application. Separation of casein from milk remark would apply to the solution of ferrous and fiom alkaline solutions. carbonate in carbonic acid water, were it not Method. On adding a few drops of acetic that the oxygen which is present in most car- acid to milk, casein is precipitated, together bonated waters acts upon a p)art of the neutral with fatty matter. To purify the casein, colcarbonate of' iron and converts it into ferric lect the coagulum upon a filter, wash it and oxide. The acid carbonates of magnesiumn redissolve it in a solution of carbonate of and manganese behave like those of' calcium sodium; leave the solution at rest for 12 and iron. In each case the amount of neutral hours, in order that the fatty matter may carbonate of' calcium, etc., which can be held separate from the alkaline solution of casein. dissolved by pure water, will remain in solu- Take off the layer of fat and reprecipitate the tion. In case the water to be examined casein by adding a few drops of chlorhydric contains a large proportion of' carbonate of acid to the solution; collect the casein upon a ammonium. errors may arise from the solubil- filter and wash, dry and weigh it. (Robin & ity of oxide of zinc in that substance. Verdeil). Properties. As obtained by Method A, According to Lehmann, acetic acid, though recently precipitated basic carbonate of' zinc formerly almost the only reagent employed occurs'in the forml of light, white flocks, as for the quantitative determination of casein, 118 CELLTULOSE. by no means effects a thorough precipitation nitrogen. for which corrections must be made. of' it, and inay even dissolve a very conside-ra- The ash is readlily determined by incinerating ble amount of' it when added in excess. a weighed peoltio'l of' the crude cellulose, while Princip/le If. Coagulability when heated the nitrog-en is assumed( to belong to some with sull)lrate of calcium. albuiminold, tile amnount of which is calculable. Aplpblictiion. Estimation of casein in milk. Sitnce all the albuniinoids contain, on the lfetdhod. Stir into the milk about one-fifth average, about 16 per cent of' nitrogen, it will its weight of' finely powdered gypsum, and be sufficient to determine the percentage of heat the mixture to 100~. Perfect coagula- nitrogen in the crude cellulose, and to multition ensues, an(l there is obtained, on evaporat- ply this quantity by 100' 16- 6. 59 in ing, a brittle residue, which may be readily o(d'ler to obtain the amount of albuminoiloi to pulverized, and from which ether and alcohol be slibtracted. - Even with these correceasily relmove fat, milk, sugar, and most of tions the estimation of' cellulose in this way is the salts. (Haidlen, Annc.len Chem. u.nti not absolutely accUrate, as may usually be seen Pharmn., 45. 273.) fiom the appearance of' the product. AccordCatechu. See Tannin, ing to v. Hofineister, crude cellulose prepared Cellulose. in this way f'rom pease was perfectly white, Principle I. Insolubility in dilute acids, while that froln wheat-bran was brown, and alkalies, alcohol and ether. that frorn rape-cake almost black. In order Alethod. Weigh out 3 grais. of tile tlhor- to obtain comparable results, care must be ouglily driecl and finely powdered substance taken to operate under the precise conditions (hay or straw) to be analyzed, and place it in prescribed. If the solvents are too concena porcelain dish, together with 200 c. e. of trated, or the temperaturle at which they act is dilute sulp'iuric acid, containing 1.25 per cent too hirgh, somne of the cellulose will be dissolved, of oil of' *itriol. Boil the liquid for half an while, if the reagents are too much diluted, a hour, anti continually addtl small quantities of qualntity of other matter will escape solution. water to replace that which evaporates Then Princi).e II, Power of' resisting oxidizing allow the mixture to settle, and draw off the agents. clear acid liquor with a syphon anid a pipette ilie/hod. Place one part (from 2 to 4 grins.) into a beaker. Pour 200 c. c. of water upon of the dry pulverized substance, which has the residue and boil for half an hour, taking been previously extracted with water, alcohol care to replace, as before, the water which and ether, in a glass-stoppered bottle, together evalporates. Allow the mlixture to settle, draw with 0.8 part of' chlorate of potassiumn and 12 off the clear liquor into the same beaker as parts of nitric acid of' 1.10 sp. grl., and digest before, add anotllel quantity of 200 c. c. of the mixture at a temperature not exceeding. water to the residue and again boil, settle anld 180 for 14 days. At the end of this tine add tlecant. -- The residue is next boiled for a quantity of water to the contents of the half an hour with a mixture of' 50 c. c. of bottle, filter the mixture and wash the residue five per cenlt potash lye (80 grins. of' fused first with cold, arnd afterwards with hot, wah[ydrate of' potassium to the litre), and 150 ter. - As soon as all the acid and soluble e. c. of water; and afterwards with two suc- matters have been washed out, throw the concessive portions of water, each of 200 e. c., fbi' tents of the filter into a beaker and heat thenrl half' an hour id each case. Tie decanted to 74~ for three quarters of' an hour, with liquors are collected in a second betaker, weak anrinonia water, made by mixing 1 part The solid matter which reinlins in the dish of commercleial aimmnonia with 50 prllts of' vaafter the several boilings, is thllown upon a ter. Finally collect the insoluble matter upon weighed filter; to it is addl.ed arx slediment a weihllel filter alnd wa.sh it, first witll lilute which may have been deposited ill the beaker ammonia, as long as tie filtrate passes oif' colwhiich has received tile alkaline liquids, anrld ore(l, then with (old anld ihot water, theln withl the contents of the filter are thenl washed with alcohol, and at last with ether. T're cellulose water, until the washings no longel exhibit an obtainel in this wxay, thouigh friee fr'om chloalkaline reaction. The sediment ini the beaker rine, still contains a sma-ll quantity of' ash and which received the acid liqluors decanted fronl nitrogen, for which corrections must be inade, the cellulose, is then thrown upon the saIe as in Methodl 1; it is purer, however, than filter, andi the contents of' the latter washed that obtained by Method 1, and the quantity successively withl water, alcohol a1(nd ether, as obtained is largmer -usually fi'oml 0.5 to 1.50 long as these solvents continue to dissolve p13r cent larger -- than that obtained by anything. Befobre throwing the sedirlents MIe tlhod 1. Method 2 yields nlore correct froln the alkaline and acid liquors upon the results thlan Method 1; they appear to v-ary filter, the clear supernatant liquids above only about one per cent froml tile truthll. (F. these sediments Ilmust be carefully decanted S.chlulze, 1857; Kiihn & others, 1866, see anmd thrown away. (lienneberg, Die llnnlwir'th- Henoebery's journal fiur Lacondl irthschtqfi, 186;, schalftliche Versuchs-Stalionen, 1864, 6. 49 ). ip. 289-297, rind,Johnson'.s "Low Crojps Grow," The final residue left after washing with ether, pp. 60i, tl). is cellulose, contaminated with ash:and with CIILORATES. 119 Chloric Acid. (Compare Chlorates). for the oxidation of organic matter, sulphur, I~iin ciple. Power ot neutralizing alkalies. arsenious acid, etc., as a preliminary step in Application. Separation of chloric acid fiom various processes of analysis. To this end any other free acid. small crystals of a chlorate, usually chlorate of Method. Measure out two portions of the potassium, are from time to time thrown into liquid. In one portion determine the total the hot, strong chlorhydric acid solution of amount of acid by titration with a standard the substance, until the oxi(lation is complete. alkali (see Acidimetry), and in the other por- A mixture of chlorhydric acid and a chlorate tion estimate the other acid in any appropriate is however a ttr less powerful oxidizilng agent way. The difference will give the amount of than a mixture of nitric acid and the chlorate. chloric acid. (See below). Chlorates. Method 2. Action of a chlorate upon ( ferPrinciple. Oxidizing power of. rous salt. Applications. Estimation of chloric acid, A. By estimating the iron of the residual free or combined. Separation of chloric acid ferrous salt. Mix a weighed quantity of the from other acids and from metals. Estimation chlorate with an excess of a standard solution of chlorine and chlorides. Oxidation of or- of protoSulphlate of Iron, or of' Sulphate of ganic matters, S, H, As, Sb, Cr, etc., as a Iron and Alnmonia in a glass-stoppered bottle. preliminary to the estimation of these sub- Acidulate the nlixture with sulphuric acidl and stances and various others, as explained under let it stand fbr some time in a warm place. Carbon, and the other elements enumerated. Finally heat the nlixture almnost to boiling and Method 1. Depending upon the action of proceed to determine by means of perinangana chlorate upon chlorhydric acid. ate of potassium, how much of' the Ferrous A. A weighed quantity of the chlorate to Salt remains unoxidized. One equivalent of be analyzed is placed in a flask, provided with a chlorate will oxidize 12 equivalents of the a suitable delivery tube (compare Chromic ferrous salt. The results obtained by this Acid, reduction of by HC1), together with an method are apt to be somewhat too high, since excess of strong chlorhydric acid. The mix- a portion of thle ferrous salt may be oxidized ture is heated gently at first, but afterwards to by the air in the bottle when the mlixture comes boiling, and the Chlorine set fiee is absorbed to be heated. (Mohr, Titrirmethode, 1855, and estimated in some appropriate way. One 1. 23' and 2. 128). way, for example, is to conduct the gas into a B. By estiatinag the ferric salt formed. solution of iodide of potassium, and to esti- Place a roughly weighed quantity of fine mate the iodine which the chlorine liberates, iron wire in a quarter-litre flask, together with by means of a standard solution of hyposul- a weighed quantity (0.1 to 0).15 grin.) of the phite of sodium, or by sulphurous acid. (See chlorate to be examined. Polur upon thLe mixIodine). Anotlher way is to estimate the chlo- ture fi'rom 30 to 50 c.c. of chlorhvlldric acid,of rine by nmeans of arsenite of sodium as des- 1.12 sp. gr., connlect the flask with a carbonic cribed under Arsenious Acid, p. 4,5. - The acid generator, and warnm it gently. The reaction between chlorhydric acid and a chlo- quantity of iron taken should be at least ten rate maS occur in accordance with either or all tiles greater than the weight of the chlorate. of' the following equations:- After the lapse of' about twenty minutes, gradCl05 ~ 2HC1 = C120 +- Clo00 +1 H20. nallvy raise the temperature of' the flask until cl20o + 4CI = l2CI2o + 2H,.I. the liquid begins to boil. Then allow thle flask C1205 + 6mCi = 2Cioo + 4Cf +.3sI20. C1205 + 8I-IC = cli2o sc + s1 2o. to cool, and estimate the Ferric Salt formed Ci2O5 + 10iCi == iC2CI + 5i20. by titration with hIyposulphite of sodium. But no matter what products of decoinposi- The process is said to be mIlore accurate than tion are formed, they all agree in this, that that described in ~ A. (Braun, Zeitsch. analyt. when brought in contact with iodide of potas- Chemz., 1867,1,, 43, 47). - To siulm, they will set fiee 6 equivs. of' iodine for estimate (cloric acid in presence of nitric or each equivalent of chloric acid in the original nitrous acid, determine the amount of efficient chlorate.. The process yields accurate results. oxygen, as above, (compare Nitric Acid), and (Bunsen, Annalen Chem. und Pharm., 86. calculate therefiolll the amounts of chloric and 282). of nitric acid, biy the method of indirect analyIn case an aqueous solution of chloric acid sis. (See Carbonic Acid, p. 80). (Braun, is to be examined, mix a weighed or measured loc. cit., p. 62). portion of it with a slight excess of' soda lye, Instead of hyposulphite of sodium, Braun, evaporate to dryness upon a water bath, and (.Journ. pcrakt. Cheem., 81. 421) formerly used proceetl with the residue as above described. protoChloride of Tin to e^stimate the ferric When metals have to be separated fiom salt. chloric acid they may be estiImated in the res- In case a mixture of' a chlorate and some idue of the decomposition above described, or other salt is to be examined, estimate the a special portion of' the substance may be chlorate as above in one portion of the mixboiled with strong chlolvhydric acid on purpose. ture, and the other acid in another portion of.,. B. The same principle is often employed the material. - In case free chloric acid is 120 CHLORATES. to be estimated in an aqueous solution, satu- ble to the estimation of free chloric acid in an rate a measured quantity of the solution with aqueous solution. soda lyle, evaporate on a water bath and oper- 3Method 5. Action of a chlorate upon nitrous ate as above described upon the residue. acid, or a nitrite. All the oxides of chlorine, C. By estimati ng the chlorine in the residual excepting perchloric acid, are immediately rechlorisde. When an alkaline solution of chloric duced with formation of chlorhydric and nitric acid is heated with freshly precipitated ferrous acids, when nitrous acid is added to their oxide, decomposition occurs in accordance dilute aqueous solutions. A solution of nitrite with the following equation: of lead, prepared by leading carbonic acid into K20, Ci20o + 12FeO = 21KC1 ~ GFe203. water in whlich basic nitrite of lead (4PbO, rI-1O, N,90) i s uspended, may be employed to Hence chloric acid may be estimated by effect tlie t"eduction. Such a solution may be combining it with potassium or sod(ium, mixing kept for a long time iji glass stoppered bottles, the solution with a quantity of pure ferrous which are colupletely full of it. sulphate, supersaturating with potash lye free The analysis nmay be made either in the fiom chlorine, and lheatin(r the mixture to boil- gravimetric or the volumetric way. In the ing. The reaction occurs imme(liately, so that first case, the substance to be analyzed is it is only necessary to filter and acidulate the treated with a slight excess of the cold dilute liquid befbre proceedinc to determine the chlo- solution of' the nitrite of' lead, then acidulated rine as Chloride of Silver. In presence of with nitriic acid, and warmed. The chlorhynitric acid, this method yields better resrlts 4iric, acid is then precipitated as Chloride of than that depending upon the reduction of Silver, and the amount of chleric acid (or chloric acid )by nascent hydrogen (see below other oxide of' chlorine) calculated from the No. 3). (Stelling, Zeitsch. analyt. Chemnz., weight of the precipitate. 1867, 6..32). Chloric and nitric acids may In the second case, there will be needed a evidently be estimated in presence of' one an- norinal solution (see Alkalinietry) of chlorate other in this way by thle niethod of' indirect of potassium, containing I0.01227 grin., (analysis (Compare Carbonlic Acid, p. 80). 0.0()01 eqijiv.) of the chlorate in each cubic Method 3. Reduction of the chlorate b7 n.- ccntiluetre, and a solution of nitrate of' silver scent hydroq/ern. Dissolve a weighed quantity of appi-)oxiriately known value, say 17 grins. of' the chlorate in a small quantity of w/ater, of tile nitrate in 100 c.c. The solution of place a piece of zinc in, the solutiorn, and after- pitrite of lead, moreover, should be prepared wards add somile pure dilute sulphuric acid, by weighing out roughly a quantity of basic and allow the Inixture to stand for some tilne. nitrite of' lead, rubbing it up with water, and It' no imore than 0.l grim. of cllorate of' potas- passing a continuous stream %f carbonic acid sium be taken, half an hour will be sufficient t!lrough tlhe mixture, until thebasic salt.has to complete the reduction of the chlomic to almost entirely disappearedt and a yellow soluchlohvydric acid. Take out the zinc, wash it tion of the normal salt has been obtained which carefully, andl pioceed to determine the c'hlor- is no longer rendered cloudy by carbonic acid. hydll'ic acid in the solution by precipitation as During the passage of' the carbonic acid the Chloride of Silver. From the amount of the liquid should be gently warmed. - The latteri, calculate the corresponding weight of value of' the solution of' nitrite of' lead is dechloric acidl. teriinined by means of the normal solution of An aqueous solution of free chloric acid may cilorate of' potassiuml, and is then used for be treated as if it were the soalutiomn of' a chl0- estilnating the amount of' chloric or chlorous rate. - In case the clhlorate to be examined acid in sample of unknown composition. is contaminated with ain alkaline chloride, Thle details of the process are as follows: weighl out two portions of it. IiI one portion Place the highly dilute solution of chlorate of (letermine the chlorine directly as Chlloide of potassium in a glass stoppered bottle, together Silver, but treat the other with zinc and sul- with an excess of the nitrate of silver solution plii'ic acid, as above described, beftre adding to serve as an indicator, and acidulate strongly the silver solution. The chloric acid may final- with nitric acid. Heat the closed bottle in a 1v be calculated fi'oiii the diit'erence'in thie water bath, anid add the solution of nitrite of weights of the two precipitates of chloride of lead fi'oim a bilrette, until the last drop fails to -ilver. (Sestini, Zeitsch, analyt. C(hem,, 1, 500.) precipitate alny chlorate of silver. The bottle Method 4. Reductionl of the chlo'rate by sul- m)ust be shaken fi'equently to facilitate the?)huretted hydrogen, Pass sulphluretted hydro- deposition of the chl6ride of silver. There is gen gas into the warm solution until its' odor no special difficulty in obtaining good results, persists. Add drop by drop a solution of f'er- provided the solution of nitrite of lead is suf'rous sulphate to destroy the excess of sulphur- ficiently dilute, and the solution under examinetted hydro(gen, acitdulate the mjixture with ri- ation is so dilute that no appreciable quantity tric acid, filter if' need( be, and estilnate the of chlorous acid gas can escape from it. It is chlohlydric aci(l as Chloride of Silver, andl well to dilute the 8 or 16 c.c. of normal solufl'?om the amount of this substance calculate tion of chlorate taken, to the volume of 230 f:llat of e:hloric acid. The. process is applica- C.e, Since the solution of nitrite of lead is CHLORATES, 121 slowly decomposed by the action of atmos- Estimation of chloric acid in chlorates, in pheric oxygen, it must be standardized afresh presence of water or the chloride of' an alkali for each new series of determinations. It may metal. be kept, however, for a week without much Method A. Ignite a weighed quantity of change. The presence of perchlorates has no the chlorate until the whole of' its oxygen is influence upon the results. (Toussaint, Anna- expelled and weigh the residual chloride. If len Chemn. und Pharm., 137. 114). it be desirable the oxygen may be collected Method 6. Action of a chlorate upon proto- and measured. The process is applicachloride of tin. ble only to those chlorates which are completeMix a weighed quantity of the chlorate with ly decomposed by ignition into oxygen and a strong chlorhydric acid, and a measured quan- metalic chloride. There is an objection to it, tity of a standard solution of stannous chloride, even in the case of chlorate of potassium, the latter, of course, to be in excess, and that a portion of the chlorate is carried off as estimate by means of a standard solution of dust in the escaping oxygen. Traces of chlobichromate of potassium how much of the rine also escape with the oxygen. stannous salt has been left undecomposed. Method B. In case the chlorate to be ana(Streng). According to Mohr the method is lvzed is contaminated with a chloride, weigh less commendable than those depending upon out 2 portions of' it. In one, estimate chlorhythe action of' chlorhydric acid and of' a ferrous dric acid directly by precipitation as Chloride salt upon chlorates. of Silver. Ignite the other portion cautiousMIethod 7. Action of a chlorate upon nitric ly, to decompose the chlorate, dissolve the acid. When a chlorate, chlorate of potassium residue in water and estimate the total chlorfor example, is heated with moderately strong. hydric acid as Chloride of Silver. From the nitric acid, a mixture of great oxidizing power difference between the weights of the two is obtained, well fitted for the oxidation of precipitates calculate the amount of chlorio compounds of sulphur, arsenic, chromium, acid. -- When a metal is to be separated carbon, and the like, as a preliminary to the from chloric acid the latter may be destroyed estimation of these and other substances by in a special portion of' the substance, by the ordinary methods of' analysis. The reac- careful ignition before proceeding with the tion between nitric acid and chlorate of potas- analysis. sium may be roughly formulated as follows:- Method C. To separate chloric from nitric 8KC103 + G61N03 = 6KN03 + 2HIC104 + 6C1 + 130 + 3H20. or nitrous acids ignite a weighed quantity of The oxidizing power of such a mrixture is the mixture with repeated doses of chloride of much greater than that of mixtures of sulphuric ammonium, estimate the amount of chlorine or chlorhydric acid and a chlorate (compare in the residue as Chlorite of Silver, and calenthie equations above, under Method 1). 2 In late the amount of chbloic acid by the method most cases it will be sufficient to cover the of indirect analysis. (Braun, Zeitsch. analyt. substance to be oxidized with nitric acid of Chem., 1867, 6. 62). 390 B, to heat the mixture and to throw in Chlorate of Potassium. See one by one crystals of chlorate of potassium Chlorates, above. during 15 or 20 minutes, or until the oxidation For use as a reagent, the commercial salt is is complete. When a metallic sulphide is to usually sufficiently pure. It ma.y readily be be treated, however, it is best to mix it first of purified, if need be, by recrystallization fromn a all in the condition of fine powder, with as hot solution. For the analysis of' Carbon much or rather more chlorate of potassium, compounds the fused chlorate is often required. befbre adding any nitric acid. On heating It is prepared by heating the commercial such a mixture much of the sulphur will be crystals in a porcelain dish until the mass is oxidized before it has time to cohere into fairly fused, but no longer, and pouring the lumps. The last portions of sulphur will, liquid into a platinum dish or upon pIorcelain. however, have to be destroyed in almost every Break the hot sheet into small fragments and instance, by throwing fresh crystals of the keep them in a tight bottle for use. chlorate into the nitric acid after the original Chlorhydric Acid. [See finding list, mixture has ceased to act, The operation may fobr Chlorine, in the Appendix]. be conveniently effected in a porcelain dish Principle I. Volatility. covere(l with an inverted glass funnel with Applications. Estimation of HC1 in certain bent stem. It is safer to heat the mixture cases, separation of Cl from K, Na, Ba, Sr, upon a water bath, though in that event the Ca, Mg, Pt and other metals which form nonoxidation proceedls lmore slowly than when the volatile chlorides. acid umixture is actually boiled. (Storer, Pear- Method A. Place a weighed quantity of son, and others, American Journ. Sci., 1869, the powdered chloride to be examined, in a. 48. 190 et seq). platinum or light porcelain capsule, cover it Principle II. Decomposition of by heat. with pure sulphuric acid somewhat diluted [Compare Carbon]. with water, and heat the mixture until all the Applicctions. Separation of chloric acid chlorhlldric acid and the excess of the sulphuric from metals, and fiom nitric and nitrous acids. acid has been expelled. Ignite and weigh the 122 CHLORHYDRIC ACID. residual sulphate. Calculate the chlorine the abduction tube begins to get hot change from the loss of weight. Care must be taken the receiving bottle, since the aqueous vapor to heat the mixture gently at first, in order to charged with gas which is now going forward avoid frothing, but a strong heat will subse- would weaken the strong acid already obquently be needed to expel the free sulphuric tained. The action of fuming chlorhydric acid. - This Inethod will not serve for the acid, is, in general, far more energetic than analysis of the chlorides of silver, lead, mer- that of the diluted acid. In order to obtain an cury and tin, since these substances are either acid absolutely free fiom arsenic and chlorine, undecomposable by sulphuric acid or only iln- care must be taken to use purified Sulphuric perfectly decomposed by that agent. Acid. liethod B. To separate chlorine from pla- The pure acid should neither color a mixture tinum, heat the compound in stream of hy- of starch paste and iodide of potassium (chlodrogen gas, lead the chlorhydric acid, which is rine), nor discolor a liquid made slightly blue formed, into a solution of nitrate of silver and with starch and iodine (sulphurous acid), nor weigh the Chloride of Silver. (v. Bonsdorff). should it when highly diluted give any cloudPrinciple II. Power of neutralizing alka- iness or coloration with chloride of barium, lies. sulphuretted hydrogen, or suiphocyanide of Application. Valuation of the aqueous acid. potassium. ilethod. See Acidimetry, method by neu- Chlorides. tralization. Most of the highly volatile chlorides, such Principle IIL. Comparative weight of a as the compounds of Cl, with P, S, Se, Te, given volume of the aqueous solution in pro- As, Sb, Cr, Ti, Sn, etc., have to be dissolved portion as it contains more acid. in water, as a step preliminary to their analyApplication. Valuation of the commercial sis. It is to be remembered that their solution, acid. or rather decomposition by water, is usually of _Method. See Acidimetry, method by taking such nature that the hydrogen of the water the specific gravity. goes to the chlorine, while the oxygen unites Principle IV. Power of expelling boracic with the other element to form an oxygen acid from its compounds with metals. acid. But if we can determine the amount of Application. Indirect analysis of alkaline oxygen in the aci(l formed, the composition of borates. Separation of boracic acid from sev- the original chloride can be easily calculated; eral of the metals. for example Mlethod. Dissolve a weighed quantity of the PC13 + 311O = 3HC1 + H3P03 borate in water, add an excess of chlorhydric SiCi4 22O = 4HC1+ SiO2. acid, and evaporate the mixture to dryness Or instead of estimating the oxygen acid, the upon a water bath. Take care to add a few chlorhydric acid may be estimated as Chloride drops of chlorhl#dric acid to the residue before of Silver. Only a few of the volatile chloit is quite dry, and continue to heat the resi- rides enumerated deposit anything on being due until no more chlorhydric acid vapors mixed with water, though some sulphur and escape. Determine the chlorine in the residue selenium is set free fiom the chlorides of those as Chloride -of.'Silver, calculate therefrom the elements, and a little phosphorus, previously amount of metal, and the boracic acid by held in solution is dropped by terchloride of the difference. L or the analysis of borax phosphorus. Chloride of tellurium leaves methis process yields very satisfactory results. tailic tellurium as well as tellurous acid. (11. (Schweizer). Rose). When liquid, these volatile chlorides Principle V. Power of reducing high may be weighed out for analysis in little glass oxides. See the various high oxides and bulbs such as have been described under Caroxygenated compounds, notably Chromic Acid, bon, analysis of volatile liquids, p. 67.'Thlle biChromate of Potassium, binOxide of Man- weighing bulbs should have long stems and the ganese, Chlorates, etc., etc. Compare also points should be drawn out very fine so that a Arsenious Acid. liquid may be weighed even in an unsealed For use as a reagent, pure chlorhydric acid bulb without losing anything through evaporamay be prepared, after Fresenius, as follows: tion. The filled and weighed bulb is finally Pour a cooled mixture of 7 parts of concen- dropped into a glass-stoppered bottle, containtrated sulphuric acid, and 2 parts of water, ing some cold water; the stopper is inserted over 4 parts of' chloride of sodium in a retort. and held in tightly, and the bottle shaken, first Set the retort upon a sand bath with its neck to break the bulb, and again sometime afterslightly raised, and by means of a tube bent wards to absorb the last traces of chlorhydric at an obtuse angle connect the neck of the gas. These precautions are necessary because retort with a bottle containing 3 or 4 parts of of the heat developed by the action of water water. Keep the receiving bottle cool and upon the chloride. - Solid volatile chloheat the retort as long as much gas continues rides like that of phosphorus may be weighed to be evolved from it. The abduction tube in a small glass-stoppered flask or tube, and should touch, but scarcely more than touch, the the latter subsequently opened and carefully surface of the water in the bottle. As soon as thrown into a bottle of water. CHLORIDES. 123 Principle II. Decomposition of by the pro- an acid reaction, as Emmet (American Journ. toxides of various metals. See the Chlorides Sci., (1.) 18. 255) and Fittig (Annalen Chem. of these metals. The value of the principle und] Pharm., 128. 189) have shown the prodepends upon the fixity of the chlorides. portion of material thus lost by volatilization is This principle comes into play also when Am- very trifling in a properly conducted analysis. monia is volatilized by means of lime or Method B. To estimate free chlorine, see either of the fixed alkalies, and when Hydrate under Chlorine, power of decomposing amof Aluminum or Hydrate of Chromium is pre- monia. cipitated by adding chloride of ammonium to terChloride of Antimony. au alkaline solution of these metals. Principle. Volatility of the chloride. Principle III. Power of reducing certain Applications. Separation of Sb from Na, high oxides. See Arsenic Acid, Chromic K, Ba, Sr, Ca. Estimation of Sb, by loss. Acid and Chloride of Antimony. The.MIethod is described under Arsenic Principle IV. Power of' converting salts Acid (reduction of by chloride of amrnmonium). of other acids into Chlorides. Compare Sul- It is well after the first ignition with the chlorphate of' Potassium. ide of ammonium to stir a fresh portion of Principle V. Power of retaining various this salt into the crucible and again ignite, and metals in solution, or rather of forming soluble to repeat the process, if need be, until the double salts with the compounds of these met- weight of the residual chloride remains conals. stant. In separating antimony from the alkali Applications. The most important perhaps metals a double ignition will usually be found of the applications of this principle may be to be sufficient, and as a general rule the anseen under Arseniate of Magnesium and Am- timnoniates of the true alkaline earths are so monium, and under Phosphate of Magnesium completely decomposed by a single ignition and Ammonium. It is applied almost always with the chloride that no trace of antimony is in the analysis of compounds which contain left in the residue. From magnesium on the magnesium; and frequently serves also to other hand it is difficult to expel all the antiprevent the precipitation of small quantities mony, even by repeated ignitions with the of' manganese and nickel (See Hydrate of chloride. It is impossible, moreover, to sepIron), of: tartrate of calcium, etc. arate antimony from aluminum in this way For use as a reagent, a solution of the pure since a large portion of the latter volatilizes crystallized commercial salt in 8 parts of water with the chloride of ammonium. As regards is ordinarily employed. It should be neutral the alkali metals and those of the alkaline to test papers, should give no coloration of earths, the process yields very accurate results iron when tested with sulphide of ammonium (II. Rose). and should leave no residue when heated upon quinquiChloride of Antimony. )latinum foil. For methods employed by Stas Principle. Volatility of the chloride. for preparing chloride of ammonium of an ex- Applications. Separation of Sb from Co, ceptional degree of purity, see Zeitsch. analyt. Ni, Pb, Cu, Ag, Au and Pt. Chem., 1867, 6. 423. Method. Heat the mixed sulphides in an Chloride of Ammonium. atmosphere of chlorine gas, in a bulb tube of Principle I. Fixity of the salt at 100~. hard glass, in a manner analagous to that desApplications. Estimation of ammonium in cribed under Antimony Compounds. If it be ammlllmonia gas, amnionia water, and the com- desired to estimate the antimony directly it pounds of ammonium with weak volatile acids, may be caught for further examnination in a such as carbonic and sulphydric acids. Esti- couple of flasks or U-tubes attached to the mation of free chlorine. bulb tube and charged with a mixture of tarMethod A. To estimate ammonia collect taric and chlorhydric acids. - Instead of the gas in an excess of' chlorhydric acid of the mixed sulphides, alloys of antimony and 1.13 sp. gr.; or in case ammonia water or an the metals above enumerated may be heated in almlnonium salt be under examination, super- the atmosphere of chlorine. The alloy should saturate cautiously with the chlorhydric acid. be in the form of powder if that be possible, Evaporate the liquid to dryness upon a water or as finely divided as may be. It should be lbath, and dry the residue at 100~ in an air but gently heated when the chlorine first acts bathl until the weight remains constant. upon it. In case any portion of the alloy ill case carbonate or sulphide of amnmonium begins to glow from the action of the chlorine is to be examined, it may be placed in an in- the lamp should be instantly removed. In cliled flask before adding the acid. In the case lead be present the bulb must not be c:tsc of' sulphide of amrmonium, the liquid too strongly heated lest some chloride of lead should be filtered to remove sulphur after the be volatilized. As applied to the analysis trecatment with acid. The process yields accu- of alloys the process is not specially accurate, rate results; for though solutions of chloride since the alloys are decomposed with diffiof ammronium suffer a certain amount of de- culty, and small portions of the alloy are composition when boiled, so that alkaline liable to be protected from decomposition by vapor' is exhaled and the residual liquid has the residual metallic chloride, especially when 124 CHIORIDTES. this is fisible, or when the alloy cannot be bonate of Barium, Chromate of Barium and finely powdered. When applied to the mixed Sulphate of Barium. sulphides, however, the process yields excel- Pure chloride of' barium, fbr use as a lent results. Compare Chloride of' Sulphur. reagent, may be prepared by passing a stream The process somewhat modified, may be of clllorhlivdric acid gas through an aqueous applied to the analysis of antinmoniates or solution of commercial chloride of bariumn as a.ntimonites.- such as those of copper, for long as a precipitate continues to form. example, — which are insoluble in acids and Almost the whole of' the chloride of' barium which cannot be conveniently decomposed by in the solution may be separated in this way fusion with carbonate of sodium and sulphur as a crystalline powder free firom calcium and (see Sulphide of Antimony). In that event strontium. Throw the precipitate upon a the substance is placed in a bulb-tube and filter, and wash it with repeated small porheated in the first place in an atmosphere tions of' pure chlorhydric acid until a sample of hydrogen so as to reduce it to the condi- of the washings, diluted with water and pretion of' a metallic alloy or mixture, and sub- cipitated with sulphuric acid, gives a filtr.te sequently in ahi atmosphere of chlorine in the that leaves no residue when evaporated on same tube. - It is possible to analyze in' platinum foil. (Fresenius). The aqueous this way the product known as Kupfer.qlinmmer solution (1 part Ba C12 to 10 parts of water) (Copper mica), consisting of teroxide of anti- should be neutral to test papers, and should mony combined with copper and nickel, neither be colored nor rendered cloudy on the which occurs as an impurity in some varieties addition of sulphuretted hydrogen or sulphide of copper, notably in that of Goslar. This of ammoniumn. substance is not acted upon by acids or the Chloride of Bismuth. (normal most powerful reagents; and it cannot well Bi Cls). be treated with carbonate of sodium and sul- Principle. Volatility of. phur on account of the presence of nickel'and Applications. Estimation of 13i, by loss. copper; but it is easily decomposed by hydro- Separation of'Bi from Pb, Cu and Ag. gen at a not very high heat, and the porous Mllethod. Heat the finely divided alloy in alloy formed is readily acted upon by chlo- a current of chlorine gas in a bulb-tube of rine. For the analysis of this alloy the hard glass (Compare. Antimony Compounds) method now in question is to be preferred to and weigh the residual metallic chloride. the process of dissolving in aqua regia and Care must be taken to heat the mixture until precipitation by sulphide of ammonium. (H. the whole of the bismuth has been expelled, Cose). but if lead be present the heat must be reguChloride of Arsenic. lated so that no chloride of lead shall be volPri ciple. Volatility of: (Compare Ar- atilized. If it be desirable to estimate the bissenic Acid, reduction of by chloride of aminio- muth directly, it may be caught for further nium). treatment, in a couple of little flasks or U A1gplications. Estimation of arsenic by loss. tubes attached to the bulb tube, and charged Separation of As fiom Na, K, (Method A), with chlorh]lydric acid. From this solution Co, Ni, Pb, Cu, Agr, Au and Pt, (Method B), the bismuth may be precipitated as basic less perfectly fiom the metals of the alkaline Chloride of Bismnuth. earths. (Method A). Chloride of Bismuth. (basic - lletlhod A. By heating with chloride of BiCl3; 2Bi203 + H20). amumoniumn. See Arsenic Acid. To separate Princiljle. Insolubility in water and dilute arsenic fiom barium, strontium and calinum in acids.this way, the Inixture in the crucible has gen- Applications. Separation of bismuth froln erally to be treated with five successive por- other metals, such as Na, K, Ba, Ca, Sr, Mn, tions of chloride of' ammonium. Arseniate of Cd, Zn, Co, Ni, Cu, Hg, but not from Fe or maglnesium cannot be thoroughly decomn- Al. posed even by repeated mixture and ignition 3Method. Mix the nitric acid solution of withl the ammonium salt. (II. Rose). bismuth with chlorhydric acid, or better with Mlethod B. I-Ieat the mixed sulphides in chloride of' ammonium and dilute the mixture a current of chlorine gas in a bulb tube of with a very large quantity of water. Since hard glass and weigh the residual metallic a larger qutantity of water will be needed in chlorite or the metallic gold or platinum. proportion as the solution contains more free (Compare Antimony Compounds and Chlo- acid it is impossible to determine beforehand ride of Sulphur). Arsenical alloys, even just how much water should be added. The when very finely divided can only be decom- precipitate at first formed must consequently posed with extreme slowness when heated in be allowed to settle and portions of' the clear an atmosphere of chlorine. liquor above it must be poured off and tested Chloride of Barium. with new quantities of water. So long as any Principle. Power of precipitating carbon- cloudiness is thus produced, fresh portions of ates, sulphates and chromlates. Compare Car- -water must be ad led to the main mixture of' CHLORIDE OF CALCIUM. 125 liquid and precipitate. - Ill. order to of Ca, from Mg, As, Sb, Bi, H., and Sn. avoid the necessity of' adding a large volume (Method B). of water care must be taken in the.first place Mlethod A. Choose a combustion tube not to employ a large exeess of acid in dis- about 40 c. m. long, and close it at one end as solving the bismuth compound. If the solu- if it were a test tube. Place a layer 6 c. m. tion be already strongly acid it may be long of Oxide of Calcium, free friom chlorine, nearly neutralized with ainmonia before add- at the end of the tube, then the weighed subing the water. In case the solution to be stance to be analyzed (in small glass bulbs if analyzed is very dilhte it should be concen- it be volatile), and another 6 c. m. layer of trated by evaporation so as to expel much of the lime. Mix these materials with a wire, as its free acid. There is no danger in thus described under Carbon, p. 61, and afterwards evaporating if only nitric acid be present, but fill the tube almost completely with lime. Hold if the solution contains chlorhlvdric acid or the tube in a horizontal position, and rap it aqua regia some, chloride of bismuth may be gently against the table until its contents have lost by volatilization unless care be taken to settled so as to leave a fiee passage fbr the prevent this result. It is to be remarked in escape of the gases which are to be evolved, that connection that the chloride of bismuth then place it in a combustion furnace and heat does not begin to volatilize until the larger the mixture as in an ordlinary combustion (see part of the free chlorhydric acid in the solu- Carbon). When all the organic matter has tion has been expelled. Instead of evapor- been decomposed, dissolve the contents of the ating the liquor, the free chlorhydric acid may tube in dilute nitric acid, and estimate the be neutralized by ammonia; - to this end add chlorine as Chloride of, Silver. According to amlnonia water until the solution has only a Kolbe, the products of' the combustion niay be! faint acid reaction, before adding the excess removed from the tube as follows:- As soon of water. - Collect the precipitated basic as the decomposition is complete, remove the chloride of bismuth upon a weighed filter, and fire from the tube, cork the latter, and in case wash it at the ordinary temperature with charcoal has been used as the filel, rIewater very slightly acidulated with chlorhy- move every particle of' ash from the tube. dric acid until the filtrate yields no residue Immerse the hot tube, sealed end downwarls, when evaporated on platinuln.' Acidulated into a beaker two-thirds full of distilled water, water is used instead of' pure water for wash- so that it may break into numberless pieces ing because the latter would dissolve out some and its contents fall out to be readily acted chlorine firom the precipitate. From the upon by the aci(l. \When compounds weight of the precipitate, dried at 100~, calun- rich in nitrogen are treated in this way, some late the weight of the bismuth. cyanide of calcium is liable to be formed. In case the orifinal bismuth solution con- For the method of freeing chloride of silver tains sulphuric acid, the precipitated chloride from cyanide, see Cyanide of Silver. will retain a slight trace of it in the form of a lethod B. See the Chlorides of' the several basic sulphate, but the quantity is so small metals above enumerated (volatility of). tha~t it can hardly have any influence upon Prirnciple II. Power of absorbing water. the accuracy of' the result, especially as the [Compare Sulphuric Acid, Sulphate of' Copequivalent weight of' the basic chloride of' bis- per, Hydrate of Calcium, and Phosphoric nluth does not differ very much fro.m that of Acid]. the basic sulphate. Somle phosphoric acid is Applications. Estimation of water and of dragged down in like manner by the basic hydrogen, Separation of' hydrogen from carchloride of' bismuth, in case there is any of it bon, etc. in the original solution. But it is easy in 3lMethod. Tubes of light, but strong glass, either event to determine the amount of' bis- either U-shaped, or horizontal with a bulb inuth in the precipitate by lmelting it with near one, end, are filled with small lumps of cyanide of' potassium. (See Bismluth, fixity the dry porous chloride, and their large ends of). - It is not possible to estimate bis- closed with perforated corks, provided with ninuth in the basic chloride by the method of short abduction tubes. The corks should be reduction with hydrogen, since a large quan- covered withl a thin, smooth coatingt of' sealtity of' chloride of' bismuth would be lost by ing wax, to prevent them fioni absorbing moisvolatilization. (II. Rose). ture fioll the air, or giving up moisture to the Properties. The precipitate is as good as air according to the state of' hydration of' the absolutely insoluble in water and dilute acids. latter. Bismuth mnay be so comlnletely precipitated In billing the tubes, small, loose tufts of in this way that no trace of' the metal can be cotton should be placed so as to prevent pardetected in the filtrate from the basic chlo- ticles of' the chloride fromn falling into the ride. namrrow abduction tubes, by ineans of' which Chloride of Calcium. the tube is to be connected with other pieces Prinrcilple I. Fixity when heated. of apparatus. The abduction tubes should be A.lplicaions. Estimation of' chlorine in or- wiped clean and dry by means of' little rolls of ganic compounds. (Method A). Separation filter paper, and when not in use their ends 126 CHLORIDEIS. should be kept covered with little caps, formed part of ordinary commercial chllorhydric acid by plugging short pieces of rubber tubing with 6 parts of water, and place the liquid in with bits of' glass rod. a tall stone jar; add chalk or powdered marble Sometimes the tube is filled with fused chlo- to the acid by smal quantities, until the last ride of calciumn, instead of the porous chloride. portion refuses to dissolve. Then add a little But in either event the filled tube is weighed, slaked lime, and( sulphuretted hydrogen water, after it has been wiped clean, and left at rest until a filtered sample of' the liquid gives no for some time in a place of' tolerably constant reaction with sulphide of amlnonium. Put temperature, - then attached to the apparatus the solution in a stoppered bottle and let it from which moisture is to be derived and stand for 12 hours in a warm place; then filter, finally weighed again, together with the water exactly neutralize the filtrate, concentrate by which has been absorbed by the chloride. evaporation, and crystallize. Let the crystals (See Carbon, p. 62, and Carbonic Acid, p. 79). drain and dissolve 1 part of them in about 5 Chloride of' calcium has the great merit of parts of water for use. - A solution of not absorbing any carbonic acid when a mix- chloride of calcium should be perfectly neutral, ture of that substance and aqueous vapor is and should neither be colored nor precipitated passed through -it; but it is to be remarked by sulphide of ammonium. It should not that as a mere dessicating agent, it is distinct- evolve ammonia when heated with slaked ly less efficient than Sulphuric Acid. Petten- lime. kofer observed, some years since, that air To obtain por'ous chloride of calcim9, fit for which had been dried by chloride of calcium, absorbing water in the analysis of Carbon still gave up moisture to strong sulphuric compounds, evaporate a neutral solution to acid; and Fresenius (Zeitsch. analyt. Cheam., dryness in a clean iron dish or paln, and ex1865, 4. 177 et seq.) has determined by care- pose the residue for several hours to a heat of ful experiments that neither fused chloride of about 200~ upon a sand bath. The white pocalcium, nor the ordinary dry porous variety, rous mass thus obtained consists of CaCl2 - - which in his experiments contained as much 21120. as 21 per cent. of water, — is capable of lThe fused chloride, such as is used for drythoroughly drying moist air. Air which has ing air and other gases needed for quantitative been dried as completely as possible by chlo- operations, may be obtained by evaporating ride of calcium, always gives up moisture to any solution of' the chloride to dryness, and strong sulphuric acid. The fused chloride fiusing the residue in a Hessian crucible. Pour does not dry air any more completely than the out the ftised mass upon stone or metal, break porous chloride, but acts rather more quickly the sheet into pieces and preserve the fi'agthan the latter; a shorter column of it will ments in well-stoppered bottles. suffice to remove all the moisture that can be Chloride of Chromium. removed by chloride of calcium. The exper- Principle. Colorific power. inents of Fresenius show, moreover, that Applications. Estimation of Cr and of Co. dry air, - that which has been dried by means i3ethods. As regards the estimation of chroof sulphuric acid, - on being. passed over or- mium, see the general subject of Colorimetry. dinary porous chloride of calcium, or fused Since the color of chloride of chromium is chloride which has been made to absorb a complementary to that of sulphate of cobalt, little water, is capable of removing a very the quantity of the latter nmay be estimated by small quantity of moisture from the chloride. titrating with a standard solution of' chloride The inability of chloride of calcium to re- of chromium, until the colors have precisely move all the moisture fi'om air, is no objection neutralized one another. (Hinly & I)ehms). to the use of' this agent in those cases where According to Delhms (Zeitsch. analyt. Chenm., the substance *to be analyzed for water is 1864, 3. 222) the process yields useful results, heated in a current of air. For if the incoml- though it is inferior to the corresponding one ing as well as the outgoing air be dried by in which sulphate of nickel is employed. With chloride of calcium, it will be brought to a the chrome salt a difficulty.is encountered in normal condition of' dryness in both instances, the fact that the point where the colors neuand the whole of' the water of the substance tralize one another is concealed by a yellowish to be analyzed will be retained in the chloride tint, which then appears in the liquid. of calcium tube. Errors would evidently be Chloride of Cobalt. introduced, hlowver, in case the incoming air Principle I. Fixity when heated. were dried by sulphuric acid, and the outgoing Applications. Separation of' Co fiom As, by chloride of calcium, or if' this arrange- Sb, Bi, IIt and Sn. ment were precisely reversed. 3Method. See the Chlorides of the several It is in the estimation of Carbonic Acid, by metals. loss, that the inefficiency of' chloride of' cal- Principle II. Colorific powers. ciuin is specially conspicuous. Application. Estimation of cobalt. For use as a reagent pure chloridle of cal- -Method. See Colorimetry, A. Mueller's prociumn may be prepared as fobllows: —Mix 1 cess, and Zeitsch. arnalyt. Chenm., 1866, 5. 426. DICHLORIDE OF COPPER. 127 Instead of a glass plate of a color complemen- DiChloride of Copper. tary to that of the cobalt solution, Winkler Principle. Power of reducing ferric chlouses a solution of nickel. ride Principle III. Change of color from blue to red by means of water. CuCI + FeC3 = FeC12 + CUC12Application. Volumetric estimation of water Application. Volumetric estimation of iron. in solutions of organic compounds. Method. There are needed three solutions: Method. Ignite a quantity of the blue an- -one of dichloride of' copper, one of sesquihydrous chloride gently, grind it in a warm chloride of iron and one of sulphocyanide of mortar, and treat it with absolute alcohol in a potassium (1 palt of the salt in about 9 perfeotly dry flask. Allow the mixture to parts of' water). To prepare the dichloride stand 24 hours, then separate the blue solution of copper, dissolve sheet copper in aqua regia, from the undissolved chloride by filtering it evaporate to destroy the excess of nitric acid, under a tubulated bell glass, sealed with con- dissolve the residue in water acidulated with centrated sulphuric acid below and carrying chlorhydric acid, transfer the solution to a a chloride of calcium tube at the tubulure. flask and mix with it a quantity of' chloride This saturated solution, containing 23.67 per of sodium about equal to the weight of the dicent of chloride of Cobalt, is next diluted with chloride of copper to be obtained. Place also absolute alcohol until the solution contains no in the flask some strips of sheet copper and more than 5 or 10 per cent of the chloride. heat the mixture to boiling until the liquid To standardize the dilute solution, weigh out has become almost colorless; then cork the abort 5 grms. of water in a beaker, place the flask, allow its contents to cool and dilute latter upon a white ground, and pour the with water acidulated with chlorhydric acid cobalt solution into it ftom a burette until the to such an extent that one c. c. of the liquid is violet colored, or even shows a sus- liquid can reduce about 6 milligrams of iron picnion of blue. Some experience is required from the state of sesqui- to protochloride. in order to be sure of' the precise tint at which The purpose of the chloride of sodium is to to stop. It is well, therefore, to retain the prevent the deposition of any solid dichloride liquid which has been used in the operation of of copper when the liquid is boiled with the standardizing as a point of comparison for copper strips. - The solution of dichlofuture experiments. - In an actual experi- ride may be kept for use with but little ment, the estimation of waler in glycerin, for change, by placing it in a tightly stoppered examnple, it is simply necessary to weigh out bottle in which has been placed a spiral of 5 or 10 grins. of the material, and pour upon stout copper wire reaching from the bottom it the standard cobalt solution until the pre- of the bottle almost to its top. Or the liquid determined violet tint is reached. Though may be kept in the same way as protoChlothe results obtained by this process are not ride of Tin. But it is best in either event to absolutely accurate, they still furnish tolerably standardize it anew before each new series of close approximations to the truth. The pro- experiments. cess will be found useful in many cases, though The solution of fJrric chloride needed for of course, it can be applied only to substances standardizing the copper solution is prepared soluble in alcohol, and to those which have no by dissolving 10.03 grms. of fine iron piano chemical action upon chloride of cobalt. Op- wire (equivalent to 10 grins. of' pure iron) erating with a solution of chloride of cobalt, in chlorhydric acid, with addition of' a little each c. c. of which represented 0.220 grm. of chlorate of potassium. After heating the water, Winkler found in glycerin 13.6 and 52.8 liquid to expel chlorine it is diluted to the per cent of water instead of' 12 and 52 per volume of a litre. cent; in aldehyde 73.9 per cent water instead In an actual analysis, the iron solution to 75 per cent, and in a solution of' cyanhydric be tested should be strongly acid and highly acidl 91.9 per cent instead of 90.8. - The dilute. Only 4 or 5 drops of the solution of process was not fobund to be fully applicable in sulphocyanide of potassium, which is to serve the case of alcohol. Good results were ob- as an indicator, should be added to the liquid tainel with spirit, which contained more than in order that the difficultly soluble sulphocy25 pver cent of water, but when less than 25 anide of copper may not be formed too soon. peL cent of water was present the blue color When once formed this precipitate only disappe;lred too soon, and the results were worse solves with difficulty. If the indicator be ad-.and worse in proportion as there was less water led in correct proportion, as above, the decolin the alcohol examined. (XWinkler, Journ. oration of the red sulphocyanide of iron will pra/l!. C(hem., 91. 209). be sharply defined, and only after all the ferric Principle 1 1. Reducibility by hydrogen. chloride has been reduced to a ferrous salt Applications. Separation of' Co from Ba, will the next drop of diehloride of copper proSr. Ca, andt Mn. duce a soft permanent cloudiness due to prelethod. See Cobalt, fixit} when heated. cipitation of disulphocyanide of copper. 128 CHLORIDE OF COPPtER. is well to dilute a solution of ferric chloride C and H. (Method A). Sepa.ration of Cu which contains firom 0.1 to 0.2 grinms. of' iron from As, Sb, Bi. Hg and Sn..(Method B.) to the volume of 500 c. c. or more, not that illethod A. Bend a comlbustion tube and the dilution is absolutely essential to the suc- pack a portion of it with asbestos, as tlecess of' the experiment, but that the indicator scribed under Carbon, p. 72. About 10 acts nmore plainly and satisfactorily in solu- inches of the posterior horizontal part of the tions thus diluted. The presence of metals tube should be thus packed with purified such as cobalt, nickel and copper, the salts of asbestos; a space of about 2 inches being left which give colored solutions, do not interfere vacant in fiont of the column. Place a short with the process when the liquor is sufficiently plug of asbestos in fiont of the two-inch dilute. Arsenic acil moreover does not inter- vacant space, then a column 4 or 5 inches fere with the process. Attempts to use other long of an intimate mixture of asbestos and substances as indicators, such as molybdate brown oxide of copper,-prepared by preof anmmoniuml, iodide of' potassium and starch, cipitating a copper salt with potash lye and( diniodide of copper, etc., gave less satisfactory igniting the washed precipitate over the results than those obtained with the sulpho- flame of a Bunsen burner,-and last of all, cyanide; and without an indicator the another plug of asbestos to keep the oxide in method is not exact. place. Place the tub! upon a gas coinThe merit of dichloride of copper as com- bustion furnace and push an air bath over pared with that of' protoclhloride of tin is that portion of' the anterior part of the tube fobund in the fact that it acts readily in the which contains the mixture of asbestos and cold. (Winkler,.Journ. prakit. Chem., 95. oxide of copper. This air bath is a simple 417). Hoch & Clemin (Zeitsch. analyt. Cheln., box or chamber of sheet iron provided with 1866, 5. 328), object to this process that the three holes. One hole, at the top of the decolorationl of the sulphocyanide of iron and box, serves for the insertion of a thermollthe precipitation of sulphocyanide of copper etero The other two holes which are oppodo not occur simultaleously. According to ite one another in the sides of the box admlit circumstances, either one or the other of these of the tube being thrust completely through phenomena will first appear. If the appear- the box so that a given portion of its length ance of the cloudiness due to sulphocyanide of (that which contains the oxide of' copper) copper be regarded as indicative of the point may be enclosed in a confined volume ol air of complete reduction it is essential to success and so subjected to a definite temperature. that the conditions of' each and every experi- The bulb of' the thermometer is placed in a ment should be similar. For a given quan- central position, in the interior of the bath, tity of iron the consumption of dichloride of close by the side of the combustion tube copper will increase accordingly as the liquid The bath is heated by a Bunsen burner placed is mlore' highly diluted. It will decrease on under its front end. It should be kept at a the other hand if' the proportion of sulphocy- temperature of friom 250~ to 350~ throughout anide of' potassium be increased. The quani- the analysis, - To the fi'ont of' the comtit)y of fiee acid alone does not appear to bustion tube attach weighed chloride of calexert an influence upon the indicator, pro- cium tubes and potash bulbs as prescribed vided only that the requisite quantity of acid under Carbon. be present. The substance to be analyzed is introduced On the other hand, if' the destruction of the at the posterior end of the tube and is burned coloration due to sulpliocyamiide of' iron be by means of a current of oxygen gas, in the made to serve as the indicator, it is no easier 10 inch column of asbestos, precisely as has to obtain good results, since under some been described under carbon. (See Warren's circumstances the decoloration is complete method, pi 72). All the chlorine is absorbed some little timlie before the appearance of' any and retained by the hot oxide of copper in the cloudiness in the liquor, while at other timnes a anterior end of' the tube while the water and decided cloudiness will appear before the carbonic acid go forward to be absorbed by liquid is completely decolorized. The pre- chloride of' calcium and caustic potash in the mature decoloration of' the liquid appears to usual way. After the combustion is finished depend upon the ficts that the blood red color and the tube has become cold the chloride of obtained by adding sulphocyanlide of potas- copper, together with the excess of' oxide, is siuni to a solution of' firric chlloride is in the dissolved ini dilute nitric acid and the ehlofirst place weakened or diluted by the addi- rine is estimated as Chloride of' Silver. The tion of chloride of copper, and finally changed solution of' the chloride and oxide of' coIl)er to green by a great excess of' the latter; and is readily aind completely effected by inlillerthat this tendency to obscurationl is incrleased sing the fromit part of the combustion tube, in by the presence of ferrous chloride. a vertical position. in a cylinder char(led with pro'oChloride of Copper [basic]. thbe dilute acid. Since the quantity of' oxide Principle. Fixity when heated. of' coplper reuired to absorb the chlllorinie is Applications. Estilmation of' chlorine in very small, there is no difficulty in dissolvirlg organic compounds. Separation of Cl froom it, or in the subsequent stages of the chlorinle CHLORIDE OF IRON. 129 solution of the chloride and oxide of copper is this operation the tubulure of the receiver is readily and completely effected by immersing pointed downwards into a beaker, and the the front part of the combustion tube, in a tube is slightly inclined. (I)eville, Annales vertical position, in a cylinder charged with Chim. et Phys., 38). the dilute acid. Since the qulantity of oxide The foregoing T;rocess has been modified by of copper required to absorb the chlorine is J. P. Cooke (Anaerican Journ. Sci., 1866, 42. very sinall, there is no difficulty in dlissolving 78) as follows: — Instead of the porcelain tube, it, or in the subsequent stages of the chlorinle take a platinum tube about 6 inches by 0.4 inch determination. Four or five grammes of in diameter, the neck of a small platinum still, oxide of copper are amply sufficient for a for example, will answer perfectly; and insingle analysis, but it is to be remlarked that stead of the porcelain boat. take one of' platithe oxide must be mixed with enough asbestos num as large as the tube Awill adlllit, and about to fill 4 or 5 inches of the combustion tube. 1.5 inch long. Mount the tube horizontally A shorter column than this sometilmes fails upon any convenient stand, and close one end to retain all the chlorine. The temperature with a two-holed rubber stopper. Through of the air bath had better be nmaintained be- one hole of the stopper thrust the delivery tween 250~ and 350~. Telnlperatures of' 150~ tube of a self-regulating hydrogen generator, or 160~ have beer found to be too low, and through the other the deiivery tube of' a though the soft brown oxi(le of' copper above small flask fitted to generate chlorlldric acid prescribed will absorb chlorine at lower gas. 1'o the other end of the tube attach by temperatures than a harder oxide. Oxide of means of' a caoutchouc connector, a small copper is found onl the wvhole to serve better glass adapter, so cui-ved that the endl Illy (tip than oxi(de of' lead or oxide of zinc as an into a beaker of' water. WTeigh out in the absorber of chlorine, though in the case of boat a quantity of' the finely powdlered oxides soIme difficultly comblustible chlorine conm- to be analyzed; place the boat in the tube, pounds, which cannot be bin'ned completely pass a slow current of hy(lrdrooen, andl heat by oxygen gas, oxi(le of' zinc is to be pre- the tube at the point where the boat is, by ferred (See Chloride of' Zinc). It is probable means of a single Bunsen burner. In the that bromine and iodine comnpolunds can be course of half all hour the whole of' the oxide analyzed in this way as well a's chlorine coi — of iron will be reduced to the metallic state. pounds. (Waarren, Proc. Anericcrn A cad., Then replace the streal otf lydrogen by a 1866, 7.84; Zeiltsc/h. aoalyt. Chei,,, 5. 174). much more rapid current of' chllorlhcdric acid Mlethod B. See Chloride of' Anltimony, gas, and instead of the Bunsen burner, heat Chloride of Sulphur, an'd the Chlorides of the the tube with a blast lallp. The reduced other metals enuimerated above. The chlo- iron is rap)idly changed to chloride, ~which is ride of' copper left in the bulb tube cannot be carried forward in the current of' gas and diswei hed directly since it is a mixture of' nono- solves in the water of the beaker. After a and basic-chloride. The residue nmust be dis- few minutes the action ceases, and the chlorsol:ed in chlorhydric aci(l and the copper hydric acid is to be replaced 1)y liydrooen. estimated in some appropriate way. The lamp is then withdrawn, and thle al)l)aratpr)toChlorlde of Iron. [Compare tus allowed to cool. Ini case the aIlumnina or Ferrous Salts]. other earth in the boat is not perfectly w lite; Principle. Volatility of: it should be replaced in tlhe tube ar(ld the proAppllicacti:,js. Sepationl of Fe fiom' A1, cess repecated(. - or genil ratiig the chlorCr, GI, and mlost of' the rare earths. hydric acid, the flask should be chllarged with 1Method. A quantity of the mixed preecipi- coarse salt alnd sulphmUric cidl, xwhich hll-s b)een tate of' sesq(uiOxide of Irion, alunina and diluted with about one-tlhirl its volunie of chllrome is weighed out in a small porcelain wvater antd alloiwed to cool. Th'llis illixtulre boat; the boat is placed in a poraeltin tube, when gently heated, gives a cciistaiit flow of' and there 1heated to redness in a currient of' gas which stops almost ininme(liatelyxv'when the dry hyd(rooen gas, as long as any water is lamp is withdrawn. Both the chlorhydrlic formed. Dry chlorhydric acid gas is then acid antd the hydr-ogen should be mllade to pass passed througll the hot tube, ~nd afterwarids throughll a bottle chargled with oil of' vitriol, hydrogen again. The whole of' flheo iron vol- befbre being cadmitted to the platiminun tube. atilizes as protochloride, while the alhmnina It is not well to try to use a sllall porcelain (or the chrome) is left iln a state of' pulitY to tube in place of the platinum tube, since the be weighed. The iron is either estimated fiom lamps employed could not heat it sufficientl'y, the loss, or collected and deternlined. In the and there would be risk of breaking the porcelatter case a tubulated receiver is attached to lain tube if' it were heated by a lamp. Acthe porcelain tube, and at the close of the cording to Cooke, Deville's process affords experiment moist chlorhydric acid gas is con- exceedingly accurate results. dlucted into the tube and the receiver. To. Johnson (see his N. Y. edition of Fresenius) this end a flask of' dilute chlorhydric acid is proceeds as fbllcws:-Weigh oult a quantity attached to the end of the porcelain tube, and of the powdered mixed oxides in a platinurnl its contents are heated to bolling., During crucible. Ignite over a Bunsen burner in a 9 130 CHLORIDE OF LEAD. stream of hydrogen gas for about an hour, or while in excess. Filter the liquid into another as long as water fbrms. Then ignite over a flask and pass chlorine gas through it with blast lamp in a current of imixed hydrogen frequent shakin(, until a drop of' the liquid no and chlorhydric acid gases. The whole of the longer gives a blue l)recipitate when tested iron volatilizes as protochloride, and is deter- withi ftilricyanide of potassium. Heat the mined by the loss, while the alumina and liquid to expel the excess of chlorine, and chrome are left in a state of purity. dilute wvith as imuch water as may be necesSesquiChloride of Iron. [Compare sary. A solution of iferric chloride should conFerric Salts]. tain no excess of aci(l. A small sample of it Principle 1. Volatility. stirredl with a rod which has just been dipped Application. Estimation of carbon in cast in ammonia water will give a precipitate at iron. once if' the acid be not in excess. It should llethod. Weigh out a quantity of the iron not give a blue precipitate with ferricyanide in a porcelain boat, place the boat in a harld of' otassiuim. glass tube and heat it to (lull redness in a, To prepare a standard solution of ferric stream of' chlorine, until no more chloride of chloride, Fl'esenius (Zeitsch. analyt. Chem., iron is formed. Care must be taken to dry' 1862, 1. 27) proceeds as follows: — Weigh out the chlorine completely by passirng it throudlh 10.03 grils. of fine iron wire (piano wire), pulnice stone wet with sulphuric acid; other- that is to say, as much as will contain 10 grins. wise some carbon will be lost through the ior- of' absolutely pure iron, dissolve it in chlorhymation of a volatile hydrocarbon. When dry dric acid in a long necked flask set slanting, chlorine is use(l, the whole of the carbon will ad(l enough chlorate of potassium to oxidize remain in the boat. It is to be burned in the iron. and expel colmpletely the excess of oxygen, and the carbonic acid collected and chlorine by long continued gentle boiling. weighed, see Carbon. An estilmation of car- Finally dilute the solution with water to the bon in iron imay be made in this way in 2 volumlle of 1 litre. hours. The process is excellent, and yields Chloride of Lead. remarkably concordant results. (Berzelius; 1-'inciple I. Fixity when heated. Wwhler; Tosh, Chelical News, 1867. 16. Applicacions. Separation of Pb from As, 91). Accocrding to M. Buclhner, this process Sb, Bi, Hg and Sn. afftords results as accuratte as those obtained Method. See tlhe Chlorides of the several by Berzelius's method which (dependls on the metals enumerated, and Chloride of Sulphur. insolubility of' Carbon in clhloriie of copper. Care must be taken not to ignite the mixed It is colmmended also by B. Kerl. - H. sulphllides and chlorides too strongly, lest some Hose (edition of 1851, p. 753) has objected of' the chloride be lost through volatilization. that the process is inconvenient since it is In case it is desired to remove the chloride of difficult to obtsain chlorine absolutely free fioln lead froln the bulb tube in ordler to weigh the oxygen oP air, and it oxygen be allowed to go latter, heat the chloride in a stream of hydroforward in the chlorine, some of' the carbon gen and dissolve the metallic lead in nitric will be oxidized by it and so lost. There is a acid. - For Warren's experiments on the tendency, moreover, oni the part of the chlo- use of this principle for estimating chlorine in ride of' iron to stop the tube. organic compounds, see Proc. Anmer. Acad., Properties. Fe'ars are sometimes expressed 1866, 7. pp. 88, 89; compare protoChloridce of lest small quantities of ferric chloride may be Copper (basic). lost on evaporatingr its solution to dryness, as Principle 11. Insolubility in a mixture of in the analysis of' silicates, or on boiling a alcohol a;nd ether. chlorhyvdric acid solution of it. But Freseriius Applications. Separation of Pb from Cr, (Zeilsch. analyt. Chein., 1867, 6. 92) has Hg, Cu and Bi. Estilmation of Pb in the shown by experiments that no appreciable nitrate, cilroniate, iodide, and bromide of' that loss occurs, either on long continued boiling of metal. the concentrated ch!orhydric acid solution, or.M1ethod. MIix the solution with an excess of on evaporating solutions to dryness, eitler chlorhydric acid, evaporate to dryness upon a upon the waterl bath or at a somewhat higher water baith, and adcd to the residue a large temperature, such as is employed in the analy- quantity of absolute alcohol, mixed with some sis of silicates. ether. Let the precipitate settle, then collect Principle II. Colorific power. it upon a filter, and wash with the mixture of Application. Estimiation of' iron. alcohol and ether. Dry the precipitate at a Method. See Colorimetry, Dehllm's later moderate heit in a porcelain crucible, after process. having burned the filter upon the lid. The For use as a reagent ferric chloride may be precipitate must not be heated to redness, lest prepared as follows: -- Mix 1 part of pure some of' the chlloride of lead be lost through chlorhydric acid with 10 parts of water; place volatilization. In case the precipitate be smlall the mixture in a flask together with a quantity it had better be collected on a weighed filter. of smalll iron tacks, and heat it until no more The alcoholic solution should be tested wvith hydrogen is given off; the iron being all the sulphuric acid, and in case a precipitate of CHLORIDE OF LITHIUM. 131 sulphate of lead falls it should be collected on Lead. (Eliot & Storer, Proc. American Acad., a filter and weighed. No free chlorhydric 1860, 5. 55). acid should be permitted to remain in the Principle V. Decomposition of' by solutions liquid before adding the alcohol and ether, for of bicarbonates of the alkali metals. chloride of lead is not insoluble in alcohol Application. Estimation of chlorine in chloacidulated with chlorhydric acid. In the case ride of lead. where chromate of lead has been reduced by MAethod. [Compare Sulphate of Lead]. Dichlorhydric acid and alcohol, there will neces- gest the precipitate at the ordinary tenipervsarily be some free chlorhydric acid in the ture in an aqueous solution of pure bicarbonliquid; the filtrate must, therefore, be treated ate of sodium fobr a couple of tdays. Collect with sulphuric acid, as a matter of course. the carbonate of lead upon a filter, wash thli: But on the other hand, according to H. Rose, carbonate thoroughly, and estimate chlorlile it is not a(lvisable to add sulphuric acid imrme- in the filtrate as Chloride of' Silver. Since diately after the reduction of' the chromate, the Carbonate of Lead contains sollme alkali, it with the view of determining the whole of the cannot be weighed directly. It must be dislead as sulphate, all at once. The method is solved in acid, and the lead reprecipitated in not often emploved, though there are some some appropriate way. - According to WMarcases in which it may be resorted to. (Coin- ren (Proc. American Acad., 1866, 7. 88) it is pare Zeitsch. andlyt. Chem., 1866, 5. 227). a very difficult matter to decompose chloride Principle III. Insolubility in ammonia of lead, which has been over heated or conwater. verted to the state of' oxychloriide. with a soluApplication. Separation of' Pb from Ag. tion of bicarbonato of' sodiull. Even after Method. See Chloride of Silver. Melt the treatment for more than two weeks, using fresh residual insoluble basic chloride of' lead with portions of the bicarbonate, a.n(l occasionally cyanide of' potassium, in order to obtain the agitating the mixture, a part of the chloride of' amount of' metallic Leadl. lead still remained und(comlposed. Principle I V. Solubility in an aqueous Properties. The precipitate occurs either in solution of nitrate of ammlnonium. the form of small glisteninlg needles, or as a Application. Separation of small quantities white powder unalterable in the air. One of lead from a large excess of' silver, as in the part of' it is soluble in 135 parts of water at analysis of coin. the ordinary tellperature, and in much le,:, Method. Convert the mixture of lead and hot water. It dissolves somlewhat less readily silver to the condition of nitrates, acidulate in water acidulated with chlorhydric or nitric the solution with nitric acid, heat it upon a acid, but is easily soluble in strong chlorhydric water bath and pour into it a solution of' chlo- acid from which it is partially reprecipitatedl ride of ammonium until no more chloride of on addition of water. It is exceedingly sparsilver falls, taking care that no unnecessary ingly soluble in alcohol of 70 or 80 per cent. excess of the chloride of' ammonium is added. and is insoluble in absolute alcohol. It flushs The chloride of silver is thus precipitated in at a temperature below redcliies without (lepresence of a large excess of' nitrate of amino- composition, but at higher temperatures volnium, in which the lead remains dissolved, atilizes slowly. In contact with air it suffers since chloride of' lead is readily soluble in such partial decomposition at high temperatur e a solution. The chloride of silver is collected some chlorine escaping and a mixture of oxiuc upon a filter, and washed with hot water, the and chloride of' lead being left. Its compocilumps of' chloride of silver being broken down tion is as much as possible with a glass rod. The Pb 207... 74.4(; ci2 71... 2.5.4 filtrate and wash water is evaporated in a porcelain d(ish to the consistence of a thin syrup, 28 100.00 and then transferred to a flask of hard Ger- Chloride of Lithiuma man glass, in which tile evaporation is con- Principle. Solubility in a mixture of alc'ttinled until the nitrate of' qtinmonium is hloland ether. entirely destroyed. This operation requires Applicalions. Separation of Li from Na care in the application of the heat, lest violent and Ki. decomposition of the nitrate of' amnloniuln iM olethod. Weigh out a quantity of tlhe ensue, and portions of the substance be thrown powdered nixed chlorides, dilied at 120~ out of' the flask. Wash the residue out of' the into a flask provided with a cork or stopper; flask into a porcelain dish, using at last a little pour into the flask a quantity of' a mixture (of nitric acid to remove the particles which ad- equal volumes of absolute alcohol and ether, here to the glass. Add a slight excess of' pure close the flask and let the mixture stand for sulphuric acid, and estimate the lead as Sul- a number of hours (24 at least) shaking it phate of Lead. The process gives satisfactory occasionallv. The chloride of lithium disresults. The presence of a small amount of solves whiie the chlorides of' potassium and copper, and of traces of silver dissolved by sodiumn remain insoluble. Decant the mixthe nitrate of amnmonium does no harm. Gold ture into a filter, wash the residue with the is got rid of as explained under Sulphate of mixture of alcohol and ether, and weigh it. 132 CHLORIDE OF MAGNESIUM. Evaporate the filtrate to dryness in a tared The combustion tube is then placed in posidish, convert the residue into Sulphate of tion, in an oil bath, as if' it were a U-tube, Lithium and weigh, or estimate the lithium and an aspirator and tell-tale bottle are atfrom the loas. Pure alcohol cannot be used tached to its'anterior end. Before the attachinstead of the mixture of alcohol and ether ment of the aspirator, a chlorhydlric acid soltsince chloride of potassium is not insoluble tion of the substance to be analyzed is poured in alcohol as it is in the mixture. As re- into the combustion tube, care being taken gards the separation of lithium fiino potas- that a free channel is left above the liquid fbr sium, the process is less accurate than that the passage of air. - A slow stream of air depending upon the insolubility of Chloroplat- is drawn through the tube by means of the inate of' Potassium. It is apt to give too aspirator, and the oil bath is heated to 1000 much lithium, since neither of the alkaline at first and afterwards to 200~. At first the chlorides are absolutely insoluble in the mixed air takes up aqueous vapor and chlorhydric alcohol and ether. A higher degree of' accu- acid but afterwards free chlorine. After the racy may be obtained if the chloride of' lith- lapse of' several hours the oil bath should be ium, left on evaporating the filtrate, be treated removed and a gas flame substituted for it. a second time with a mixture of alcohol and After long continued ignition, all but a faint ether to which a drop of chlorhydric acid trace of the chloride of' magnesium will be has been added. The residue thus obtained is decomposed while the chloride of calcium of course added to the first residue. - The suffers no chang(e. As soon as the decomoriginal mixture of chlorides to be analyzed'position of the magnesium salt is thus comshould not be ignited, since in that event a plete, the contents of the tube are repeatedly small quantity of caustic lithia is fbrmled, leac(hed with hot water, and the filtrate after which, by absorption of carbonic acid, would evaporation is mixed with chloride of ammoform an insoluble carbonate. In case this niuml and carbonate of ammonium, for the prehappens a drop of chlorllydric acid must be cipitation of' Carbonate of' Calcium. In order added to destroy the carbonate. (Ranminels- to remove the last traces of' magnesium the berg, Poggendorffs An nal., 66. 79). In case washed carbonate of calcium should be redisthe process is to be applied to the analysis of solved in chlorhydric acid and again precipsulphates, these may be converted into clilo- itated as before. The oxide of magnesium rides by mixing the solution with a slight which remains sticking to the tube is to be excess of chloride of calcium, adding a double d(issolved in chlorhllydric acid and thrown down volume of alcohol to the mixture, and wash- with the rest as Phosphate of Magnesium and ing the precipitated sulphate of calcium with Aunmionium. In the opinion of' its author the diluted alcohol The excess of calciumn em- process is preferable f'or separating small ployed is then removed froni tJle filtrate by quantities of' calciumi froim a large quantity of means of oxalie. acid and the second filtrate imagnesiumn to those which depend upon the is evaporated to dryness and carefully heated. insolubility of Stllphate of Calcium and OxaIt is well to redissolve the precipitated sul- lathe of' Calcium. (Oeffinger, Zeitsch, analyt. phate of calcium in hot dilute chlorhydric Cheim., 1869, 8. 457). acid, to evaporate the solution almost to dry- Principple II. Deconposition of by oxalic ness, and exhaust the residlue with diluted acid. alcohol. The traces of alkaline chlorides thus rlppiicotion. Separation of Mg friom K and obtained are added, to the rest. It is to be Na. remarked that sulphate of lithium cannot be fMethoid. Add to the solution of the mixed completely changed to the chloride by igni- chlorides enough oxalic acid to convert all the tion with chloride of almmuonium like the other metals present, viewed as potassium, into alkaline sulphates. (H. Rose). qua(droxalate. Add more water if need be to,Properties. Chloride of lithium deliquesces ensure complete solution, evaporate to dryness so easily in the air that it is very difficult to in a platinum capsule and ignite. ])uring the weigh it accurately. It cannot be ignited ow- evaporation the alkaline chlorides are paring to its volatility and to its tendency to de- tially, and the chloride of lagnesium colnconmpose when moisture is present. pletely converted into oxalates, and by the Chloride of Magnesium. final ignition the oxalate of n magnesiurn is Principle I. Decolmposition of by hot oxy- chlange(d to magnesia, and the snlall quantity gen or air. of oxalates of the alkali metals to carbonates. Application. Sep)ration of Mg from Ca, Treat the residue with repeated snlall porltions especially when the bormler is largely in excess of boiling water, collect the Oxide of MLaoneof the latter. siusn on a filter, and in case the filtrate is at liethod. A combustion tube is bent up- all turbid, evaporate it to dlryness and again wards at both ends, and at one end (the pos- filter to separate any magnesia which Iiay terior) is again bent outwards and drawni out have been deposited. Finally add chllorhyso that it can be attachled to a chloride of' cal- dric acid to the filtrate aind estimnate the alkacium tube and a set of' Liebig's potash bulbs. -lies as chlorides. See Chloride of Potassium. CHLORIDE OF MANGANESE. 133 Chloride of Manganese. amount used, it will be seen how much was Principte. Fixity when heated in an atmos- consumed in precipitating the mlercurous salt, phere of hydrogen. and the amount of the latter may then. be Applications. Separation of Mn from Co readily calculated. - The process yields and Ni. accurate results, though fi'oim the need of filterMlfethod. See Cobalt, and Chloride of Co- ing and washing it has no great advantage balt. The turbid solution of chloride of man- over the gravimetric method. It is well, someganese, decanted from the reduced cobalt (or times, to weigh the precipitated dichloride, nickel) is acidulated with chlorhydric acid, and to titrate the excess of chloride of sodium and concentrated somnewhat by evaporation, also, for the sake of control. after which the manganese is precipitated as Mlet7hod C. Precipitate dichiori(le of merCalrbonate of' Manganese. cury in a glass stoppered bottle. (Conmpare diChloride of Mercury. (Caloinel). Method A., gravimetric, above). Let the pre[Compare Mercuric Compounds]. cipitate settle; collect it on a filter without Principle I. Insolubility in water, anti fixity heeding the particles which adhere to the sides at 100.0 of the bottle, and wash it as well as the bottle. Applications. Estimation of mercury in Then push a glass rod through the apex of the mercurous salts. Separation of Hg from Pb, filter, and rinse the precipitate back into the Cd, Cu. Estimation of fi-ee chlorine. (Method bottle. Pour into the bottle a sufficient quanD). tity of a solution of iodide of' potassium, toMethods: - Gradinzetric. gether with a measured quantity of a stan(lard Mliethod A. Mix the cold, highly dilute so- Iodine solution, put in the stopper and shake lution with chlorhydric acid or with a solution the bottle until the precilpitate has all d(is-: of chloride of sodium as long as any precipi- solved. tate forms. Let the mrixture settle; collect the For every gramme of (liecloli(de of mercury precipitated dichloride of' mercury upon a about 2.5 grms. of' iodide of' potassiull and weighed filter, dry at 1000 and weiohli. The 100 c. c. of one-tenth normnal iodine solution results are accurate. In case the substance to may be taken. Since an excess of io(ilne is be analyzed is a solid, insoluble in water, it used, the solution will be colored brown. Esmay either be treated directly with dilute timate the excess of looine ly, means of' hypochlorhydric acid in the cold, or it may be dis- sulphite of sodium. (Heimpel, Annalen C'hem. solved in highly dilute nitric acid, and the und Pharm., 110. 176). solution mixed with a large quantity of water, Method D. To estimate free chlorine in after most of' the acid has been neutralized chlorine water, put a'i wioelld quantity of lewith carbonate of sodium, before proceeding tallie mercury il the liqui;lnd leave the ilixwith the precipitation. Care must be taken ture for a lonlg time. until the odor of' the chlonot to change any of the mercurous salt to the rine has wholly (liappearetd. The mercury condition of' a mercuric salt. If lead be pres- must be in excess fionl first to last. Collect ent, the precipitate must be washed with spe- upon a weighed filter the dichloride of mnercury cial care with water of 60~ or 700 until the whllicl is foimel, together with the excess of washings are no longer colored on addition of metallic mnlecury, dry at a temperature below sulphuretted hydrogen. 1000 and wveigh. The increase in weight of Volzunetric. the mercury gives the weight of chlorine in Mlethod US. [Compare Principle III, below], the liquid. A sinall proportion of the mercury Pour firon a burette a standard solution (one- is liable to be lost by volatilization, even when tenth normal) of chloride of sodium into the the temperature is kept below 100, so that coldl solution of the mercurous salt acidulatel the process is rather less acculate than the with nitric acid, until a precipitate is no longer corresponding method, depending on the insolproduced, and a slight excess of' the chloride uility of' Chloride of Silver. (H. Rose) of' sodiuml has been added. It is easy to de- For Schulze's method of estimating chlotermine when an excess of' the chloride of so- rine in organic compounds, see protOxide of dium is present, though from the fact that, Mercury. unlike chloride of silver, the precipitate does Principle 11. Volatility when strongly not ball or become granular, it would be well- heated. nigh impossible to stop at the precise monment Applications. Separation of mercury from when precipitation ceases. Collect the precip- several of the liohter metals, and fiom the itated dichloride upon a filter; wash the precip- metals of the alkalies, alkaline earths and itate thoroughly, taking care not to use any earths. more water' than is absolutely necessary, and 1Method. The substance to be analyzed is determine how much chloride of sodium has either ignited in a crucible and the mercury gone into the filtrate by precipitating the chlo- estimated from the loss, or it is heated in a rine as Chloride of Silver. with a stan(lard combustion tube drawn out and curved in front silver solution. By subtracting the excess of so as to dip into a beaker of water, by which chloride of sodium thus found, fromI the total the chloride is retained. 134 DICHLORIDE OF MERCURY. Principle Ill. Conversion of to mercuric means of a pipette, 100 volumes of the soluchloride by chlorine: - HgC1 + C1 - HgCI]. tion of the mercurous nitrate, corresponding Applicationr. Estirnation of chlorine in chlo- to 0.5 grin. of chlorinle. Place the liquid in a rine water. Valuation of bleaching powder, beaker, dilute with water, and add an excess and of binoxide of Imanganese. of a solution of chloride of sodium, together Method A. Put a weighed quantity of di- with a slnmall quantity of chlorhvdric acid free chloride of mercury in the liquid which con- fiomn chlorine or sulphurous acid. Cautiously tains ifree chlorine. Shake the mixture fre- pour the bleaching powder liquor from a burquently, until the odor of the chlorine has coni- ette into the mixture ip the beaker, until the pletely disappeared. Then collect upon a liquid just becomes clear. The mixture must weighed filter the dichloride, which still re- be stirred incessantly, and must be kept acid mains undissolved, and dry and weighl it. The fr-on first to last. Rlead off the number of c. c. difference between this last weigh]t and the of blebaching powder liquor used, and proceed weight of dichloride originally taken, gives to calculate the amoklu of chlorine contained the amount which has been dissolved, and in thlem. froom tlhe known value of' the niercueach equivalent of' the dichloride thus lost cor rous solution used. responds to an atoml of chlorine in the liquid, iIMehod C. To determine the value of binConsiderable time is required folr the comnplete oxide of malnganese, and of other hiqth oxygenL removal by the dichloride of' chlorine from its coinpounds, place a weighed quantity of the solution. oxidt, together with some strong chlorhydric MIethod B. One of the earliest mrethods of acid in a flask, fitted with a perforated cork Chlorinmetry depends upon the principle now carrying a delivery tube bent at two right anin question. As applied by Balland (Jour)n, gles. Let the outer long limb of the delivery de Pharm,., 1838, 24. 105), a solution of iner- tube reach into another flask containing water, curie nitrate is poured into the solution of in which a weighed quantity of very finely bleaching powder, until a precipitate persists powdered dichloride of' mercury has been suseven on agitation. But the process is not pen(led. Warnm the mixture of oxide and accurate. larezeau (Pogcy, Ann., 22. 273), acid, as occasion may require, so that an exon the other hand, pouLed a mixture of water cee(-ingly slow (levelopment of chlorine shall and a weighed quantity of the bleaching pow- occur, talking care, meanwhile, to shake the der to be tested, into a liquid holding in sus- absorption flask frequently, to prevent the pension a known quantity of' dichloride of dicbloride of' nercury from becoming impacted llercury, until the latter was all dissolved and at the bottom of the flask. For each atom of the liquid had become perfectly clear. The chlorine absorbed, one equivalent of the dinecessary solutions wereI prepared as fbllows: — chloride goes into solution. At the end, boil Weigh out 5 grins. of pure, dry chloride of the liquid in the flask which contained the sodium, dissolve in water and dilute to the mianganlese, in order to sweep forward the last volume of 400 c. c. Measure off' in a pipette traces of chlorine. Then collect upon a 50 c. c. of' a solatjon of' mercurous nitrate, or weigrhed filter the dichloride of mercury which more or less, according to the degree of concen- remains undissolved, and wash, dry and weigh traition of the liquor, place thle solution in an it. Subtract the weight thus found from the eight ounice glass-stoppered bottle, and dilute weight of diclhloride taken, and from the difto the volumle of about 5 ounces. Slowly ference reckon the corresponding quantity of pour the chloride of' sodium solution fromn a binoxide. It is to be observed that the abburette into the bottle, until the last drop sorptionI of chlorine by the suspended dichloceases to produce a precipitate. DIuring this ride is slow, much slower than in the correoperation keep the bottle in hot water, and spondingr process, where the Chlorine is made shake it after each addition of the chloride of to act on sulphurous acid, hence care must be sodium, to promiote the settling of the precipi- exercised to prevent the escape of any of the tate. in case too nmuch chloride of sodi um chlorine. happens to be added at first, add a few more Properties. The precipitated dichloride is a c. c. of the mercurous solution, and again add heavy wllite powder almost absolutely insoluchloride of sodilnn). Iead off how much chblo- ble in cold water. It is slowly decomlposed by ride of sodium has been used, and calculate boiling water. It does not dissolve at the ortherefriom how much mercury is contained in dinary temperature in water acidulated with each c. c. of the mercurous solution. Then chlorhydric acid; at a higher temperature dilute a quantity of' the latter to such an ex- some of it dissolves, and on boiling with access tent that each c. c, of the diluted liquid shall of air the whole of the dichloride is gradually correspond eithler to 0.01 grin, of chllorine, or converted into soluble protochloride. Boiling to 0.00.5 grin. concentrated chlorhlvdric acid decomposes it For the actual analysis, grind up 5 grins. of rather rapidly into metallic mercury and protobleaching powder with water, to a definite chloride, Boiling nitric acid decomposes and volume of milky solution, in the usual way dissolves it. Chlorine water and aqua regia (see under Arsenious Acid), Measure out, by convert it into soluble protochloride even in PROTOCHLORIDE OF MERCURY. 135 the cold. Solutions of thle alkaline chlor;des. with the mercury, the apparatus may be simdecompose it slightly in the cold, and to a con- plified as follows - Place a weighed quantity sitlerable extent wlen heated. of the mlixed sulpthides caretllly (dried at 100~, The diehloride is permanent in the air and in a porcelain boat, place the boat in a wide may be (fried at 100~ without loss. It volatil- glass tube and heat it in a current of chlorine izes without previous fusion at a temperature until all the sulphur and mercury have been below redness. Its composition is: expelled. From the weight of' the residual Hg 200... 84.93 chloride, calculate how inuch of the corresC 3.5. 15.07 ponding' sulphide was contained in the matter 235.5 100.00 analyzed, and in the entile precipitate. The difference between the latter quantity and the protoChloride of Mercury. (Corro- weight of the precipitate is sulphlll(ie of' nlersive sublimate). [Compare Mercuric Corn- cury. pounds. ] lIet/od B. To analyze the double comPrincip)le I. Volatility. pomln(ts fbrmned by the union of mlcrc'uric chloApplications. Separation of Hg from Pb, ride with other mnetallic chlorbi(es the so Cu, Ag, and, in general, from all metals which called chloromerculates - v. Bonsdorff (Pog — form non-volatile chlorides (Mlethod A). geado:f's Annalen, 17. 115) proceeds as folAnalysis of chloro-miercurates (Method B). lows: - Select a glass t4be about. 0.5 inch in Separation of Mg fiomn alkali mletals andt froml diameter, close it at one endl and blow out that chlorine (Method C). end into the firm of a little flask; at a point Method A. Precipitate the mixed solution several inclies above this flask blow a,smnall with sulphuretted hydrogen (see Sulphide of bulb, or rather an enlargellent of the tube; Mercury, etc.), collect the precipit.:te upon a above this protuberance dIraw out the tube so weighed filter, dry at 100~ and weigh. Intro- that its diameter may be about 0.25 inch; duce a weighed portion of the precipitate into there cut it off', a(d slmooth thel edges. The a weighed bulb tube of' hard glass, or into a length of' the finished apparatus should be porcelain boat, which is afterwards placed in about 6 inches. Weigh the dried apparatus, a piece of hard combustion tubing; pass a put a quantity of the substance to be analyzed slow current of (Iry chlorine through the tube, in the bottoml of the flask, again weigh, auld and heat the mixed sulphides in the boat or close the endl of the tube partially by ineanls of bulb, at first gently, but afterwards to faint a loosely fitting cork. Clamp the apparatus redness. A couple of small flasks charged in a nearly horizontal position, and warm the with water should be attached to the bulb tube flask gently with a lamp. The water of' crysto receive the volatile matters which are ex- tallization in the compounll will be first driven pelled from it, and the tube shoultl be bent so off; and will collect ill the protubermlance on the as to project into the first flask. The chloride neck of the tla;sk.. It ma;y be relllm\e(d with of' sulphur which is formed distils over corn- slips of' filter paper or expelletl by heating it pletely into the flasks, but a part of' the eblo- very gently, iln which event no residue, or ride of' mercury is apt to condense in the a scarcely percep!tible residue of lmercuric chlocolder part of the tube. In that event, cut ride will be. left upon the undlel side of' the off the soiled portion of the bulb tube, and bulb. Aft:er the fitst instalment of' water has wash out the chloride fiom it into the flask. been thus remlove(l replace the cork and again Or, if' a porcelain boat has been used, with- leat the contents of the flasl;k gently, to be draw the boat from the combustion tube and- sure that all the water is expelledl, then allow wash out the latter. The piece of bulb tube the apparatus to cool, anl weigh it. The loss which has been cut off' is dried and weighed of weight represents the water of' crystallizatogether with the rest of' the bulb tube anrd its tion in the substance. A\auin heat the flask, contents. It the residue contains only a single loosely corked as before, until the whole of' the metal, the weight of the latter can be calcu- mercuric chloride is driven into the neck of lated at once tromn the weilght of its chloride, the flask near tl;e bulb, then cut the apparatus but if there are several mnetals present the in two at a point below the sublimate, and chlordlles mnust be relucel in a stream of y- weigh each I)ortion, first witil its contents, an l drogen, antd the metallic residue thus obtainetd afterwa.rds withoutt them. Since the mnercuric dissolved in nitric acid as a preliminary to chloride mlight be contamin-ated with a few their separation by appropriate processes. milligramnles of water, it Lid better be left to The soiution of chloride of' mercury is mixed drlly over sulphuric acid belfrle weighing it. with some chloride of ammoniumn, heated to In case the chloride l]et in thle flask, is of expel chlorine, then filtered to separate the such character that it call be heated in the air sulphur and subjected to analysis. See di- without change, the flask htad better be ignited Chloride of Mercury or Sulphid'e of Mercury. after the fir t weighing, and again weighed to Compare Chloride of Sulphur. The process make sure that all the mercuric chloride las yields accurate results. i- f it be deelned been expelled. When carefully conducted the sufficient to estimate the mercury by the loss, process yieldls good results. Tlhere is scarcely as may be done in case only one nletal is mixed any risk of losing chloride of mercury during 136 CHLORIDE OF NICKEL. the evaporation of the water, or its expqlsion rower. Ben(l the narrowed portion downmward from the flask. and then a(,al:n horizontal, in a plane parallel ii-e;ho,'l C. To separate magnesium from to that occup}ied by thle rest of the tube. alkalies andl lio:n chlorine, place the solution Fi -allvr (liaw out to a point and( turn upwards of' the mnixed chloridles in a crucible, evaporate tlle i terior endl of the tube, leaving 10 c. m. the solution to llryness, and in case any chlo- or so, of the tube horizontal andi of the origiride of' anllnilonin be present igrnite thle resi- nal dicamieter. Tlis anterior horizontal space due. The substance to be analyzed mlust serves as a reservoir for a fibw c. c. of water, as contain no aci(d other than chlorlvdtric. Mlix will be (lirectly explained. - Into the long, the residue with a little warm water, and stir posterior wi(le portion of the tube push an into the nlixture a tquantity of pure elutriated asbestos pluh, tIhen a layer of' 12 or 15 c. in. of oxide(l of' mIterculry - about three timies as much eicoarstly powdered chloride of potassium, then as there is of the mixed chlorides. Agrain a secon(tl sInall loose plug of' asbestos, and evaporate to thorough dlryness upon a water place the tube upon a wire gauze support. bath, with firequent stirring; then cover the Behind tle secondl asbestos plug place a porcecrucible and lleat it to redness until all the lain boat charged w'vith lumps of the phosphide chloride of'tlelrcury, which has been formeed by of' iron to be analyzed, then a third plug of the decoinpolsition of' the chloride of magne- asbestos, and close'the tube wT ith a perforated siuln, is expelle(l. 5In the case of separating cork carlrying a slhort delivery tube. Charge nimanesiuln f'oin chlorine the ionition mitst be tile anlterior horizont.al part of' the tube with continuel until tthe excess of' oxilde of mercury water, as above indicatte(l, and by mneans of a employed hls all been expelled; but in separat- caoitclhouc connector at ach to that end of the ing nimanesitlln from the alkalies it is enough to tube another tube charged with moistened bits drive off the chloride of' mlercury b heat, and of porcelain. The purpose of the water and to separate the oxi(le of imer(urly, together imoist polceleain is to retain chloride of phoswitl1 the oxide of' nlagnesium, b) filtration phorts, thiat of the chloride of' potassiun is to fiioln the ult(ecoimposed( alkalline h oli ides. In retain ret in lo(ide of irol, and to destroy a comnthat case it will finally be exlpelledl when the pondl of thle ehloriides of iron and phosphorus. Oxi(le of' Magnesiunii comes to be rgniteitl. IHeat the chloride( of' potassium with a laimp The Iethod iP convenient and vields satis.- and pass a currlent of dry air throuoh the tube factory results. C(are llust be taken to add to iemlove all traces of'moisture. Then pass only a little more than enouglh oxilde of rner- in'a stream of chlorine gas, and as soon as all cury to tlecomipose tile chloride of nimagnesium the air has be.en expelled fromt the tube, heat and to avoid iiltalilln tlte futies of corrosive the plorcelai0- boat with a second lamp. Lnsublimlate which 1are, givenl off dnriMlg the igni, mlediatelx a red liquidl will begin to condlense tion.'l'he alkaliine chlorides obtainled should in the tube, antd to lifftuse itself emong the tbe tested fbi, iiagnesiuin; a trace of it will lump's of ebloxoride of' potassium. The latter usually be fobundtl in tlhem.,(Berzelius, in his must ol ly be heated in the neighborhood of JahreDtbericht dler Cheltie, 1842, 1. 142.) the boat, and no more strongly than will sufPt'inciple II. Oxidizilg power. See.Mer- fice to mlelt the double salt of chloride of poc('ur Collpounds. tassililn andl chloridec of iron -which is f ormled, Chloride Qof Nickel. ad1( tlltuS prevent the tube hioom beconming Princitle 1. Fixit) when hleatet(, stopped(. Towardls the close of the.operation Applications.'. Separation of' Nli friom As, Sb, the heat max be iclr.ease,t, but never to dull Bi, HI(g andi Sn. retIness,'ince tat that temIlperature chloride of',Met7Io(. See the Chlorides f' the mletals phjosp)lhorus would be decomposed by the oxyabove enumellated. gen ill the silicic acid of' the glass with fbormaPrinciple II. Color;fic power, tion of' plosphoric acid. All the chloride of ApplicarIon. Estinlation of' nickel, phosphmluis is diriven forward by tleanl of a lletlhod. See Colorilietry, A. Mueller's gentle heat into the anterior reservoir of' water, process, and Zeitsch. analyt, Chem,, 18,6, 5. and(l the opi,,ratiop is considleretl to bhe fiIlished 426. Instead of a glass plate of a color com- wvhnl no mIore sublimiate can be seen. The plemnentary to that of the nickel solution, reservoilr-tubg is finallv de;taclhet by cutting'Winkler uses a solutionl of cobalt. the narrowvetl hpart of'the tube, then eitptied into Principle III. Ieducibility by hydrogen. a porcelain d(ish and washed out with waxiter. Applications. Separation of' Ni from JBa, The tube clT earrge with bits of' porcelain is also Sr, Ca auld Mn. washed out iilto the samle porcelain diah. NiMetthod. See Nickel, fixitv of. tric acid is addedt to the liquidt, and tme nimxChloride Qf P.hogsphorus. ture is evaporated. The chlorhydric acid'srinciple. Volbatility. decormposes without effervescence, as the liquor Application. Estimation of phosporlus in becomes concentrated, and',:dthe phosphoric phosphide of iron. acid is finally determined as Phlosplhate of Method. Heat a glass tube at about 30. c.. Silver. from its anterior end in such imanner that It is best to maintain a constant stream of about 15 c. in. of the tube shall be made nar- chlorine, so that this gas may always be pres CHLORIDE OF PLATINUM. 137 ent in slight excess. To this end a self-regu- Principle. Fixity at moderately high temlating apparatus provided with a stop-cock peratures. sllhould be employed. A telltale bottle chargoe(l ll)I)lications. Estimation of potassium in with water, and placed beftbre the tube whicl tile hydrate, sulphate. chromate, chlorate contains the bits of' porcelain will indicate the (which see), silicate and sulphide oft that rate of flow of the chlorine. (Schloesing, metal. as well as in the potassium salts of weak Zeitsch. anc/lyt. Clern., 1868, 7. 474). volatile acids, - such as carbonic acid and BiChloride of Platinum. various organic acids. Separation of K fionom Prio-ip!e I. Colorific power. See Color- Na, both dilect and indlirect. Estimlation of in-letry, A. Atiller's process, and Zeitsch. analyt. chlorine in organic compountls. Cl/er?., 1864, 3. 407. Mlethod. Evaporate tile clear solution in a l'i'tc cple I. Power of precipitating potas- platinum dish almost to dryness, then transfer simillm andI annllloniuln. See the Chloroplati- the liquor to a platinum crucible, taking care nates of these mletals. to use as little water as possible in washing the'ro prepare bichloride of platinum for use as dish, and evaporate to (dryness upon a water a reag ent. cut up a quantity of worn out foil bath.: Transfer the crucible froml the water or wire into very smlall pieces, boil them for bath to the niddlle of a small iron pot, fit to sonme time in a porcelain dish with nitric acid serve as an air bath, and heat the pot to such alone, to remove inmpurities, then decant the an extent that the chloride of potassium 1may nitric acid and boil the metal with repeated be exposed to a temperature somlewlat higher small portions of aqua regia until it has all, or than that of boiling water. After some time nearly all, dissolved. Decant each portion of transfer the crucible to a ring-stand and heat the acqua regia, after it has acted upon the it almost, but not quite, to (lull redness, by platiinutmu for sonle little time, into another means of a lamp, and weigh. The crucible porcelain dish and evap)orate the mixed solu- should be kept covered during the ignition, tions almost to dlrxyness upon a water bath, then and the temperature carefully regulated, so adld some cllorhydrie aci(l and agaill evaporate that none of the chloride shall be lost through until no odlor of chlorine or of chlorhvdric volatilization. By heating the salt in an air acidl can be perceived. On allowing the dish bath, as above described, before the finral ignito cool the chlorid(e will solidify to a crystal- tion, the last traces of' wvater are expelled, and line 1mass, which should be dissolved in a inot all chance of loss through dlecrepitation avoided. too large quantity of water, and the solution When carefully executed the process yiel(ls kept for use. It is well to know approximately very accurate results. Instead of weighhow strong the solution is, and to label in that ing the chloride, the chlorine contained in it sense the bottle which contains it. A good may be determined by titration as Chloride of streiith is 0.5 grirnl. of' platinum to each c. c. of Silver. This method saves tinle where many solution. It is important that the evaporation estimations have to be mlade, but is of' no adbe ina(le upon a water bath lest some of the vantage in the case of a single determination. salt suffer decomposition and protocllloride of The presence of free acid ill the original pllatinum be formed. The solution when evap- solution does no harm. It is, in fact, often ora-ted to dryness upon a water bath should necessary to evaporate the conlpound to be leave a residlue completely soluble in ordinary analyzed with an excess of chlorhlydria acid, al( oliol. According to Rose, it is best to oper- in order to expel some other acid. In the ease ate ill porcelain vessels and to avoid glass, in of nitrate of potassiull tile evaporation nmust order that as little alkali as possible may be be repeated wltlh 5 or 6 new portions of chlordissolvedl olt to contaminate the platinum so- hydric acid till the weighllt of the ig nitetl chlolution. ride remains constant. In order to avoid A still better way is to bring the platinumn frothing when carbonate of potassiuml is to be ill the fir.;t place into thle condlition of powder, converted into chlori(le-as in the analysis of so fine that it can be readilv dissolved by aqua residues obtained by ionliting the potassium re i;a.'To this end fuse -5 parts of' imetallic salts of nonvolatile organic acils-it is Iest to z';ni in a clay crucible. and little by little treat the carbonate with a solution of elhloride tlhrow.v into the ielted metal 1 part of Illati- of' ammonium instead of chlorhydric acid, and a1uo scraps. Stir the alloy with a pipe stein to evaporate the mixture to dryness antl ignite pliuletl with.ry clay, and pour it into water. the residue. A sli(ght excess of' chloride of'Jrelt tile drops of' alloy with chlorhydlric aminonium should be used, and the nixture acitl solnewhlat diluted, until there is no longer hadl better be evaporated and ignited in a tolanv effervescence, then boil for a time with erably large disli to expel the chloridle of amfire'sh chlorhydriic acid to remove the last traces monium before transferring the cllorilde of of' zilic, wash with water, boil with nitric acid, potassium to the crucible. By heating tie ag,'ail wash, and finally dissolve in aqua regia, dish moderately at first, andl afterwards almost addced all at once, and evaporate the solution to redness, the chloride of' ammonium can all as abolve. be expelled without loss of' any of the potasChloride of Potassium. [Corn- siuI salt, for the amlnmonium salt changes pare Chloride of Sodium]. at once. from the solid to the gaseous state 138 CHLORIDE OF POTASSIUM. without becoming liquid, and so long,as there filtration, and proceed as above. A. Ailitscheris ally chloride of amlllOlliuI leIft to evap)orate, lieh (.Joum'I. proAtlt. Chein., 83. 459) has shown none of' the chloride of potassium ckan volatil- that no loss of the alkaline chloride is occaize. Whenever chloride of' ammollnoium has to sioned by the escape of chlloride oft' ammnonium,, be expelle(d in tlhis way, the residue should be not evev whllen 20 parts of' the latter are igtaken tip in the least iossiblec (uantity of wa- nited with one of the tbrmer. ter and filtered, in order to sepIarate particles Wlhen a imixture of' chloride of potassium of dirt and carbon, which almost always pre- and oxalate of anmmoniuml is ignited to expel sent themselves. - In no event should any the latter, an apI)reciable quantity of' the chlochloride of aimmonium be allowed to get into ride of pota.ssiumn is (lecomposed with evoluthe platinuim crucible with the solution of' tion of' chlorlhydric acid, and mnore or less chloride of potassiuml for it would inevitably carbonate of potassium is left mixed with the cause loss of the latter by creeping over the residual chloride. If fiee oxalic acid be igrim. Even when the quantity of chloride, of nited with chloride of' potassiullo, a still more almmlonium in the solution is very smnall it must considerable quantity of' the carbonate will be be expelled by ignition in a dish before the fbrmed. It is even ipossible to change the potassium salt can be safely transferred to the whole of the chloride of potassiumn into car-' crucible. It is to be observed that chloride bonate by igniting with oxalic acid. But the of ammonium can be more easily driven off carbonate of potassiuml thus formed can readily from chloride of potassiuml than sulphate of be destroyed, aiter ithas been iformled, by means ammnonium froim sulphate of potassiumrn. For of chloride of' ammloniumi, as above described; the conversion of sulphate of potassium to the and if chloride of ammlonium be added to the state of chloride by mneans of (chloride of am- original solution of oxale acid and chloride of monium, see Sulphate of' Potassium; for its potassium, before evaporating it, the deconmpoconversion by means of baryta water see Sul- sition of the latter nlay be prevented. phate of' Bariuim, and fobr its conversion by Principle If. Insolubility in absolute almneans of chloride of strontium see Sulphate cohol. of Strontium. In the preliminary steps to the separation of Application. Separation of from Li. potassium and sodium, both by the direct Method. See Chloride of Lithium. method (see Chloroplatinate of Potassium) and Principle IIl. Power of absorbing heat thee indirect method (see Chloride of Silver), while dissolving in water. the process is conducted precisely as above Application. Estimation of chloride of sodescribed, i. e., as if nothing but chloride of' dium in impure chloride of potassium. Rough potassium were present. It is important, how- valuation of potashes and pearlash. ever, to remember that the mixed chlorides lIethod. It is a matter of experience that ought never to be weighed until their purity has chloride of potassium'in the act of dissolving in been proved by dissolving them in water, and water cools the liquid far more than a similar testing the solution with carbonate of ammo- quantity of chloride of sodium can. Thus while nium and ammonia. No precipitate should be 50 grins. of chloride of potassiunl in dissolving produced by these reagents, and the solution in 200 grins. of water contained in a glass, should moreover be clear before they are added. weighing 185 grins., an(l capable of holding 320 Filter, if need be, and again evaporate. As grnis, of water, will lower the temperature obtained by L. Smith's process (see Carbonate 11.40, the same anioulit of' chloride of sodium, of Calcium) from a silicate, the chlorides are under similar circumstanc es, will reduce the peculiarly liable to leave a black residue on temperature only 1.9~. Froml these data, being treated with water. according to Gay-Lussac (Alnnales Chim. et Estimation of chlorine in organic compounds. Phys., [2.1 12. 14 and 39.'356), the reduction In acid organic compounds, such as chloro- of temperature produced by any mixture of spiroylic acid, for example, chlorine may be chloride of' potassium and chloride of sodium, determined by dissolving the compound in an dissolved in a similar quantity of water, may excess of dilute potash lye. evaporating to be reckoned; and conversely fiom the observadryness, and igniting the residue, by which tion of the temperature in any given case, the means the whole of' the chlorine is obtained proportion of chloride of' potassium in the as chloride of potassium. Dissolve the resi- mixture can be estimated with tolerable accudue in water, and estimate the chlorine as racy. Let the quantity of chloride of' potasChloride of' Silver. (Loewig). sium in 50 grins. of the mixture be called x, To separate potassium (or sodium) from and that of the chloride of sodium 50 -x. chromnic acid, mix the compound with about Then the reduction of' temperature effected by twice its weight of dry powdered chloride of x parts of chloride of potassium will be ammonium, ignite the mixture carefully until 11.4 X, ad that protuced by 50 - x parts of the whole of the ammonium salt is expelled, 50 o dissolve the chloride- of' potassium in water, chloride of sodliuIn ill be lsiZ-). The obseparate it from the oxide of chromiunm by served reduction of temperature which may CHLORIDE OF ROSEO COBALT. 139 h)e called t, is the sum of these two quotients; determination of sodium in carbonate of poconsequently tassilln, contaminated with that substance. ii4t = x10 X + 1.9 (.90-x) It will be necessary only to convert the mixed carbonates to chlorides, and then proceed as an(l the quanltity x of chloride of potassium in above. 50 parts of tile mixture may be obtained by Similar methods are evidently applicable to reduction as follows: the analysis of' other mixtures of' salts, which t t- 1.9 50t- 05 absorb or evolve heat on being dissolved in x _ 10.,. 5 -,0.5 611.4-1.o - ( 9.a ~water. The chief objection to the process in To avoid the trouble of calculating each any case is the listurbing influence which the single result, Gay-Lussac has constructed a presence of other salts may exert upon tile fall table by means of' the above formula, which or rise of the thermometer. gives the per cent of' chloride of' potassium in Properties. Chlorile of'potassium is readily all possible mixtures for each tenth of' a degree soluble in water. but nluch less soluble in dilute of temperature between 1.9~ and 11.40. (See. chlorhydric acid. It is alhnost completely inthe original mnleloir of' Gay-Lussac, or Hand- soluble in absolute alcohol, and but slightly werlerlbuch derl Cenemie, 1. 893). soluble in spirit. It is permanent ill the air at It is essential that the mixture of the chlo- the ordinary temperature, fuses at a, moderate ri;les should be finely powdered, in order that red heat without change, aiid volatilizes in the salts mnay dissolve as rapidly as possible, white fumes at a higher temperature. The and that the observations of temperature be volatilization proceeds mlore slowly the more made with a highly sensitive thermometer, effectually access of air is prevented (Fresemarking tenths of degrees. - The details nius). When the aqueous solution is evapoof the process are as tollows: -Weigh out 200 rated, a small quantity of water is obstinately grins. of' water in a French glass flask of 185 held mechanIcally enclosed in the seemingly grins. weight and 320 c c. capacity, place the dry residue. Great care mlust be exercised to therllmometer in the water and bring the ap- expel this moisture before the salt is ignited, plaratus to the temperature of 20.40. Take as has been already explained. VWhen evapoholl of' the flask by its neck, so that the rated with an excess of nitric acidit is readily warnmth of' the hand shall not influence the and completely converted into the nitrate.' telllperatulre of the water, pour in the 50 grins. When evaporated( repeatedly with an excess of' tle dIry, powdered chlorides, and twist the of oxalic acid it is converted into oxalate of flask about rapidly while observing the ther- potassium. The composition of' chloride of ioioneteri. The observation is finished when potassium is, the chlorides have dissolved, and the thermom- K... 3.1.... 5241 eter has sunk to the lowest point. The differ- C1.... 5.5 47.59 ellce between 20.4~ (the original temperature) 74.6 100.00 anl(l the degree to which the mercury has Chloride of Roseo Cobalt. fallen, will be equal to t, as above stated. Principle. Spairing solubility in cold dilute Since, a single experiment occupies only about chlorhyrdric acid, chloride of ammnoniumn:xand 10 minutes, the process has a certain value for alcohol. technical purposes, such as the valuation of, The proposition of Terreil (Co7nptes Reblndus, the chloride of potassium usedt in the manufac- 62. 139) to separate Co from Ni and Mn, by ture of' potash- fromn so(la-saltpetre, and for precipitatinf the former as chloride of' roseo making alum. cobalt, by the action qf' permanganate of poIt is to be observed that Gay-Lussac's table tassium upon a boiling amnimoniacal solution of is triue only fbr the case where th,~ 50 grins. of the three me,als, has been shown to be valuemixturle and 200 grins. of water are placed in less by Braun and Fresenius (Zeitsch. analyt. a glass flask of' the given weight and capacity. Chem., 1866, 5. pp. 114-116). Some of the Vith a ditfierent sized flask a different rate of cobalt escapes the oxidizing action of' the perthermometric reduction would obtain. Instead manganate, and the chloride formed is not ot' triying to fulfill all these conditions, it would wholly insoluble in dilute chlorhy dric acid. )proi blth)i' be easier for each experimenter to Chloride of Silver. chlloose a flask for himself at randoml, and to Principle I. Fixity when heated in the air. determine once for all the reductions of tem- Application. Weighing of' chloride of silver perature prod(uced in it by 50 grins. of' each of as obtained by the gravinletric method under the pure chlorides when dissolved separately in Principle II. Retention of chlorine in the 200 grilns. of' water. A formula could then be analysis of some organic compounds. See Carlmadle out at once (with the.new values in bon, p. 68. place of 11.4 and 1.9), and a new table calcu- Met hod. See under Principle II, and Propiat(;id to be used in place of the table of Gay- erties, below. Lussac. The temperature of 20.4~ chosen by Principle II. Insolubility in water and Gay-Lussac as the normal, may as well be dilute nitric acid. retained. Applications. Estimation of silver, of comnThe process may be applied, of course, to the bined chlorine, and of chlorhydric acid. Sep. 140 CHLORIDE OF SILVER. aration of Ag from K, Na, NH,4 Ca, Sr, Ba, cant as soon as the mlixture has settled, and 1Mg, A1, Cr. Fe. P, S. Se,'le s, Sb, Sn, Co, repeat the process until a small portion of the Ni. 15:u, Zn, Cdt, Cn, PI), Bi, HI-I: Ur, Au, water tested: with chtlorhydric acid, or with and Pt. Separation of' chlorhyd(ric acid fiomn nitrate of silver, as the case may be, does not sullphuric, phoiphoric, bol) lcir', silicic, fluor- beconme cloudy. It is well to acidulate with hvdlri(, chloric, nitric, oxalic, arselious, arsenic, nitric acid the water used for wash'ing the chloandt chromicr acids. Direct and indirect sepla- ride of silver, since the settling of the latter is ration of K fi-onl Na. Ass ay of coins and thereby slightly promoted(l. other alloys of silver. Transfer the washed precipitate from the Gravicmetric Ie/lhod.l. flask to a weighed porcelain crucible as follows: 3et ho(l. Thte no(lerately lilute solution of Set a tolerably large evaporatin dish, filll of a silver salt, of' chlorhydric acid, or of' a chlo- water upon the table; fill the flask which conride, is slightly acidulatesd with nitric acid, tains the chloritle of silver comnpletely full of either inl the cold or at templeratures no hiehler water and invert the p)orcelain crucible over than 6;0~ C., antd then mixed with dilute, chllor- the mouth of' the uprighllt flask, so that the lathydric acid, or with a solution of nitrate of ter shall be in a measure closed )by the crucisilver, as the case nmay requhire, as long as any ble. Hold the crucible as tightly as possible. precipitate continues to be formed. Care lmust against the mouth of tilte flask and suddenly be taken not to add any considlerable excess of invert the latter, so that the crucible and the chlorhydric acil, or of' chloride of so(ium, mouth of' the flask shall be comlpletely sunk in when these substances are eml)loye(l as I)re- the water of' the evaporatinll (lish. Lift tle cipitants. for chloride of' silver is somewhat flask a little, so that its rill sihall bh just within soluble in them. The presence of all other the (crucible, and rap the flask so that the last substances capable of' dissolving chloride of particles of' the chloride of' silver shall fall silver must of course be carefilly avoided. down into the crucible. Finally slip the mouth (See proplerties, below, and Dictionalry of Sol- of' the flask over the riml of the crucible, still ubilities). - Precipitated chloride of' silver keeping the lotll ul.ller water, and lift the may be washed either by decantation, or upon crucible out of' tie dish. Decant the clear a filter. The imethod by decantation is best water fi'om the crucible, dryr the chloride thorwhen the amount of' precipitate is large, and ougllly upon a water bath, and lheat it over a when nothing but silver (or chlorine) is to be lamp until it begins to fuse at the edges. determined in the solution; but when the pre- Wlhen the crucible has become cold, weigh it cipitate is small, and when other substances witl its contents. - To fkciiitate the setbesidles silver or chlorine are to be determined, tling of the plecipitate in the crucible it is well a filter should be emlployed, lest too large a to heat it upon the water bath before attemptproportion of the precipitate be lost, or too ing to decant the last portions of' liquid. The great a bulk of' liquid be obtained. last drops of water may be removed by holding ln, case it is proposed to wash by decantation, tle crucible in an inclined position and touchplace the acidulated solution to be airalyzed in ing the water with little rolls of' filter paper. a tatll conical flask, with long neck and narrow In case any particles of' chloride of' silver are mouth, immerse the flask in water, and main- seen in the beaker into which the liquid from tain tile latter at a temperature of about 60~ C. the flask is decante(l, leave the mixture at riest The flask should be provided with a smIooth in a warn, dark place, Itb a number of' hours, and sufficiently large cork, orm with a finely- decant the clear lhqiql, collect the residlual ground gla~ss storpper. Add the precipitant chloride of silver upon a snmall filter, as below, little by little, while occasionally twisting the andl add its wveight to that of' the main preflask ultil the last drops produce no further cipitate. cloudiness, then cork the flask and shake it The precipitate obtained by adding nitrate vigorously until the chloride of silver has united of silver to a solution of' ehlorhydric acid, setinto large coherent luimps, and the supernatant tles mnuch more lquickly than that obtained by liquid has becoiime tolerably clear. Remove adding chlorhydric acid to a solution of nitrate the cork ami(1 wash. fi'oln it and fi-om the neck of silver. of the flask any particles of' chloride which Since chloride of silver is decomposed by may have adhered there, then leave the flask light, it should( be kept in thle (lark as much as at rest in the warmin water diring several hours, possible during the processes of precipitation until the precipitate has separated completely, andl dlecantation. A sleeve of cloth to cover andi the liquid above it is absolutely clear and the flask will be sufficient for the purpose, and transparent. Wihere a high degree of' accu- the operator need not be afrtaid to uncover the racy is required the imixture niay be left to flask as often as he may please, to observe the settle for 12 hours in a moderately warm, dark progress of the precipitation. Direct sunlight place. miiust of' course be carefully avoided. - In Decant the clear liquid. froml the flask into oi'ler to relimove the fuse(l chloride of silver a beaker, as colnpletely as nmay be ipracticable, fi'otl the crucible, put a bit of zinc upon the taking carle not to pour out any of the chloride; chloride and fill the crucible with highly dilute then fill the flask withl hot water and argain (de- chlorhvdric acid. Some of the chloride will CHLORIDE OF SILVER. 141 quickly be reduced to the condition of metallic It would be difficult to transform the mcrcusilver, and its adhesion to the flask destroyed. rous to a mercuric salt by heating the original In case the precipitate is collected upon a fil- solution with nitric acid, in case the solution ter, the latter should be as small as possible, were very dilute. - According to Levol, and the precipitate should be left to settle for no thorough separation of the precipitate fiom some hours in a warmn, dark place, before pro- the liquid can be obtained unless an alkaline ceeding with the filtration. The precipitate acetate be added to the original solution. In is washed with hot water, thorouglly dried, the absence of an acetate some chloride of and ignited in a porcelain crucible, as above. silver would, moreover, remain dissolved in Before igniting, the chloride of silver must be the mercuric nitrate (Wackenroder). - In removed as completely as possible fiom the separating silver fromn lead, also, acetate of paper, and the latter burned upon the lid of sodium should be added to the original soluthe crucible. Since some of the chloride is tion. The mixture is then heated and precipalways reduced in this operation, the filter ash itated by the addition of rather dilute ehlorshould be moistened with two or three drops hydric acid, taking care to add no more of the of dilute nitric acid and gently warmed, then acid than is absolutely necessary. In this treated with a drop or two of chlorhydric case, the purpose of the acetate of sodium is acid and thoroughly dried, in order to recon- to retain chloride of lead in solution (Anthon). vert the metal into chloride. Or the reduced In separating silver fiom bismuth, care shoull silver may be weighed by itself, as such. Or be taken to have enough free nitric acid presthe crucible may be discarded altogether, and ent to prevent the precipitation of any basic the chloride collected and weighed, on a tared chloride of bismuth. For the sake of' cerfilter dried at 100~. - It will often be tainty, it is best to heat the precipitated found convenient to combine the method of chloride of silver with dilute nitric acid, after washing by decantation with that of filtration. the clear supernatant liquor has been deThe great bulk of the precipitate may be canted, in order to dissolvd any chloride of washed by decantation and dried in a porce- bismuth nhich may have gone down'. In both lain crucible, as above, while the (lecanted cases the precipitate must be washed thorliquor is passed through a filter. and the chlo- oughly with water acidulated with nitric acid, ride thus collected incinerated by itself: befbre any pure water is added to it. Instead Exceptions cland special precautions. In sep- of proceeding in this way, some tartaric acid arating silver ftiom mer'curqy, care must be may be added to the original solution, then taken to keep the chlo-idle of silver from being ammlinonia, or sonle other alkali in excess, aind contamllinated with difficultly soluble salts of finally chlorhydric acid in slight excess. mercury. In case the precipitation be effected Nothing but chloride of' silver will go down in presence of a nitric acid solution of mer- from the mixture, even if water be also added. curie oxide, some basic nitrate of mercury is To separate silver from gold or platinutm, in liable to go down with the chloride of' silver, alloys, treat the alloy with cold dilute aqua and the proporticn is larger, accordingly las regia, and after this agent has ceased to act the amount of free nitric acid in the solution dilute the liquid largely, and collect the undisis less. On the other hand, if'there be present solved chloride of' silver upon a filter. This a nitric acid solution of mercurous oxide, some method is apl)licable only to alloys which conmercurous chloride will go down with the sil- tain less than 15 per cent of silver. Ifa larger ver precipitate. See also, below. proportion of silver be present, the chloride To avoid these contaminations, the original of' silver formed by the action of' the first porsolution may be mixed with acetate of' sodium, tions of' aqua regia will envelop the m;est of' the or acetate of' ainmmonium, and the silver pre- alloy so completely as to protect some of' it cipitated with a solution of chloride of sodium. fiom the actionvof the acids. - To estiOr chlorhydric acid, in not too great excess, mate free chlorine, put a weighed quantity of mnay be added to the diluted original solution, finely divided silver iinto the liquid X:hich and the precipitate heated with a mixture of contains the chlorine, and leave it there, taknitric anid chl-rhydric acid, after the clear ing care to shake the mnixture occasionally, supernatant liquor has been decanted. Or, until the odor of the chlorine has comlpletely instead of treating the precipitate with the disappeared. Collect, wash, dry, igiite and mnixedl acids, the basic mercuric nitrate may be weigh the mixed precipitate of silver andl decomposed and removed froln it by means of chloride of silver. The ilncrease oft' weight of a solution of acetate of' sodium or acetate of the silver gives the amount of chlorine in the alnimoniumn, to which a very simall quantity of liquid. To prepare the finely divided silver nitric acid has been added. prccipit:te somlle nitrate of silver with ferrous Inl case of' having to deal with a solution sulphate, or rctduce solie chloride of Filver which contains rnercurous oxide, the inipure with zilic. precipitated chloride of' silver may be heated For the separation of chlorinte from the metwith aqua regia to convert the insoluble nler- als, in chl()rides soluble in water, or Ilitric curous chloride into soluble mercuric chloride. acid, no special precautions are necessary, ex 142 CHLORIDE OF SILVER. cepting in the cases of the chlorides of anti- the chlorine can be proceeded with. (Peligot). mony and platinum, mercuric chloride, stannic. In estimating chlorine in presence of a fluochloride, and green protochloride ofclhromium. ride it is best to throw down the fluorine, When a solution of either of the chlorides of as Fluoride of Calcium, by adding nitrate of antimony or of mercuric chloride is mixed with calcium before proceeding to precipitate the nitrate of silver, the chloride of silver thrown chloride of silver; though when the substance down will carry with it a certain quantity of is soluble in water it is perfectly possible to the other metal. To avoidl this contamination estimate the chlorine first by adding nitric the mercury or the antimony mnay be first acid and nitrate of silver in the usual way. thrown down by means of' sulphuretted hydro- An insoluble chloro-fluoride would have to be gen, the excess of' the latter destroyed by add- fused with carbonate of sodium and silicic ing a few drops of a solution of ferric sul- acid. - To estimate chlorine in a silicate phate, and the chlorine subsequently determ- dissolve in dilute nitric acid, if that can be ine(l in the filtrate. It will not do to drive off done, anti if no gelatinization occurs add nithe excess of sulphuretted hydrogen by heat, trate of silver to the highly dilute solution, for a part of the chlorhydric acid would es- without warming it at any time. Before procape with it. In the case of antimony it will ceeding to estimate Silicic Acid in the filtrate, be necessary to add some tartaric acid to the add dilute ehlorhydric acid to it in the cold, solution to prevent the separation of' a basic and so remove the excess of silver. salt (see Sulphide of Antimony). - When In case the silicate gelatinizes with the nitric nitrate of silver is added to a solution of chlo- acid, dilute the jelly and allow the mixture to ride of platinum, insoluble chloroplatinate of sil- settle; filter, wash the precipitated silicic acid ver (2AgCl, PtC14) is thrown down, together and add nitrate of silver to the filtrate. If'the with the chloride of silver. Various methods silicate to be examined cannot be decomposed have been proposed to avoid this difficulty. by nitric acid, fuse it with a mixture of carv. Bonsdorff, for example, heated chloride bonate of sodium andl carbonate of potassium of platinum and its compounds in a current of in a platinum crucible, boil the fused mass with hydrogen, and led the chlorhydric acid gas water, remove the dissolved Silicic Acid by into a solution of nitrate of silver. Other means of carbonate of' ammnonium, and precipanalysts have melted the platinum chlorides itate the filtrate with nitrate of silver after with carbonate of sodium, and estimated chlo- acidulating with nitric acid. (H. Rose). rine in the solution obtained by treating the To separate chlorine fiomn nitric and chloric fused mass with water. acids, in case the metal with which the chloInstead of these methods Topstie (Zeitsch. rine, etc., is combined, is capable of uniting analyt. Chem., 1870, 9. 32), directs that an with phosphoric acid to form an insoluble conlexcess of zinc filings be added to the tolerably pound, boil the solution with recently precipdilute solution of the Platinum compound, in itate(l, thoroughly washed tribasic phosphate order to precipitate the platinum in the met- of' silver. Chloride of silver and phosphate of allic state. The chlorine (or bromine or iodine the metal with which the chlorine was prein case these elements be present) may then viously combined, will separate as insoluble be determined in the filtrate in the usual wa~y. powders, together with the excess of the phosAfter the development of hydrogn has ceased phate of' silver, while the nitrates and chlorates in the aqueous solution, the liquid is saturated remain in solution (Chenevix; Lassaigne, with ammonia and heated upon a water bath Journ. de Pharm., 16. 289). before filtering off the platinumln. This method Estimation of Chlorine in organic complounds. is said to yield excellent results. To estimate chlorine (or bromine or iodine) Or the platinum compound may be con- in organic compounds, or to separate chlorine verted into Sulphite of' protoxide of Platinum, (or bromine or iodine) from cyanogen, seal up a compound which does not interfebre with the the substance in a glass tube, together with precipitation of' chloride of silver (see Iodide some nitric acid of 1.2 sp. gr., and a slight of Silver). From a solution of stannic excess of' nitrate of' silver, as below. In chloride nitrate of silver would precipitate, most cases the oxidation of the organic matbesides chloride of silver, a (quantity of' bin- ter is easy and rapid, while the chloride (iooxide of tin and oxide of silver. To avoid dide or bromide) of silver separates out. this result, precipitate HyI-Idrate of' Tin ilt the As regairds cyanogerti the separatio, n defirst place by adding sulphate of sodiumn or pends on the rapid (lecomlrosition of cvyanide nitrate of amimoniumn to the liquid, and esti- of silver un(ler the conditions above described. mete the chlorinie in the fliltrate. (Lcewinthal, Organic substances, such as the ilembers of.Journ. prakt. Chem., 56. 371). Frolom a the aromnatic series, which (lo not otxiize solution of the green pro'ochloride of chlromiztm easily, may be destroye(l by putting s(lnoe initrate of silver cannot throw dowvn all the cllromuate of potassium in the tube with the chlorine. The chrolniulnm llust consequently acid and the silver salt. But in tlhat event the first be preciiitatedl as IHydrate of' Chromium, highly diluted acid liqulid must be heated to by means of ammtnonia, amIlt the precipitate (lestroy the chromate of silver which is formed, removed by filtrationl before the estimation of' before proceeding to collect the. chloride of CHLORIDE OF SILVER. 143 silver. The free nitric acid is then neutra- pressing it against the side of the cylinder, lized, almost, but not quite, completely, by after a light scratch has been made upon it adding pure carbonate of sodium, and the in- with a glass-knife of hardened steel. The gases soluble chloride of sodium is collected and within the tube will then escape in so fine a weighed, together with the fragments of the stream that all the Chlorine will be readily glass bulb, the weight of the latter being sub- changed to chlorhydric acid. Before opening tracted from the total weight of the precipi- the tube completely, let some of the sulphite tate in order to obtain the true weight of the solution enter it to destroy the chlorine there. chloride of silver. Since there is always an Heat the mixture until the whole of the sulexcess of nitrate of silver present in the liquid phurous acid has been expelled, add enough above mentioned, the solvent action of' the pure carbonate of sodium to nearly neutralize nitrate of' sodium upon the chloride of silver the acid, and precipitate the chlorhydric acid has but little significance. - The details of with nitrate of silver. - The amount of the operation are as follows: —Prepare some nitric acid to be sealed up with the organic little weighing bulbs, somewhat similar to those substance in the tube ranges from 20 to 60 described under Carbon, on p. 67. Each of times the weight of'the substance; it varies acthese bulbs should have two capillary stems, cording to the quantity of oxygen which the one upon either side of the bulb. These stems substance is capable of' consuming. Nitric should be about 1 inm. m. wide at their ends, acid of 1.2 specific gravity is best suited for very thin in glass, an(d bent or curled to one the requirements of' the case; when a stronger side at the ends. In one of these bulbs seal acid is used the tubes are more liable to exup from 0.15 to 0.4 grm. of the liquid to be plode, and with a weaker acid a higher temanalyzed, taking care to leave as little air as perature and longer continued heating will be possible in the bulb. Put the loaded bulb in required. With acid of 1.4 specific gravity, a tube of difficultly fusible glass front 10 to 12 the conversion of the organic matter into carm. m1. wide and closed at one end to a round bonic acid and( water, is rapid at a temperature end. Fill the tube about half full of nitric not much superior to 1u00; with acid of fromn acid of 1.2 specific gravity, with addition of ni- 1.12 to 1.2 specific gravity, the mixture must be trate of silver, as above, then draw out the heated from 1 to 3 hours to form 120~ to upper end of the tube at the blast lamp to a 1500. Some substances, such as naphthalin and thick, capillary tube, heat the nitric acid to phenylalcohol, are completely decomposed only boiling, and when all the air has been expelled after 6 or 8 hour's heating, to 1500 or 1800, in sealthe capillary tube at the lamp. As soon case no biehromnate of potassium has been as the nitric acid has beconme cold, shake the added. The process is applicable also for the tube until the points of the weighing bulb are estimation of Sulphur and Phosphorus, as will broken off so as to leave openings of about 1 be explained hereafter. (Carius, Lieigq and m. m. through which the nitric aci(l can gain Kopp's, Jahresbericht der C'hermie, 1860, 13. easy access to the contents of' the bulb. Then 668, and 1861, 14. 833; Kraut, Zeitsch. place the glass tube in an iron tube closed at analyt. Chenm., 1863, 2. 243). The process one end, and set the latter in an oblique posi- would be an excellent one were the sealed tion in a sheet iron box or air bath, and heat tubes less liable then they are to be broken by the latter with a gas flame to 120~ or 140~. explosions. In order to open the tube at the close of the B. For the steps preliminary to the addioperation, let the glass become perfectly cold, tion of' the silver solution in other methods of warm the capillary point gently, in order to estimating chlorine in organic compounds, expel any liquid which may have collected see Chloride of' Copper, Chloride of' Calcium, there, and finally heat the extreme point of Chloride of' Potassium, Chloride of Sodium the tube to redness, so that the gases within and Chloride of' Zinc. the tube may escape through the softened For separating vlagnesium front the alkaliglass without violence. Then cut the tube in metals, Sonnenschein (Pogyendorffs Aal*o/lez, two below the capillary portion, and wash out 74. 313) evaporates the solution of the mllixed its liquid and solid contents. The object in chlorides to lryness, ignites mnoderately to explacing nitrate of' silver in the tube is to pre- pel chloride of' anmlonium, treats the cooled vent the formation of any chlorine gas. In residue with water, and boils the solution case there was no nitrate of' silver in the tube, with an excess of' carbonate of' silver, until the some gaseous chlorine would be fbrmed as liquid exhibits a strong alkaline reaction. It well as chlorhydric acid, but in that event, the is well to continue to boil for 10 minutes, with point of the tube may be broken off beneath constant stirring.'The mixture is filtered as the surfkce of a dilute solution of sulphite of hot as possible, and the mixed precipitate of sodium contained in a glass cylinder. For chloride of silver, carbonate of' lumanesiulm each part of the organic substance, fiomn 8 to and the excess of' the carbonate of' silver, is 10 parts of the sulphite would be needed, and washed with hot water. A little chlorhydric as imuch water as would amount to 40 times acid is ad(1ed to the filtrate to throw down a the volume of the nitric acid. The point of' trace of' silver which goes into solution, the the glass tube must be broken off carefully, by mixture is again filtered, and the alkaline 144 CHLORIDE OF SILVER. chlorides determined as explained under Chlo- c. e. of perfectly pure nitric acid of 1.2 speride of Potassiuln. The nmatter upon the fil- cific gravity, and set the bottle in an inclined ter is dliested in chlorhydric acid, an(l froin position upon a water or sand bath, anti heat thle solution thus obtainedl magnesium is pre- it gently until the whole of' the silver has (liscipitated as Phosphate of' MagInesiuSm and Am- solved. By means of a bent glass tube, monliuni. It is to be observed that a small blow the red fumes out of the upper part of portion of the chloride of magnesium is the bottle, and after the bottle has been alchanged to oxide by the first ignition. Oxide lowed to cool somewhat, set it in a stream of Silver might be used instead of' the carbon- of' water, the temperature of' which is not ate. far fromn 16~. As soon as the bottle has According, to Fresenius, this process is not been reduced to the temperature of' the to be commnended, since the filtrate invariably water, wipe it dry and place it in a box or contains something more than mere traces of case made of' pasteboard blackened internally, magnesium. and reaching to the neck of' the bottle. Next B. Volumetric 3Method. measure out 100 c. c. of' the strong solution of Instea(1 of weighing the precipitated chlor- chloride of' sodium in a pipette and let it flow ide of Silver, as in A, its amount miay be de- in upon the silver solution in the test bottle. termine(l with great accuracy by employing a In order to measure the salt solution with due standard solution of chloride of sodium or of' ni- accuracy, the pipette should be fixed firmly in trate of silver, as the case may be, and noting a vertical position, in a support after it has how much of this solution is required to pre- been filled above the mark, before the excess cisely precipitate a weighed quantity of the is allowed to flow out. Moisten the stopper of silver compound, or of the chloride under ex- the test bottle with water, press it firmlly into alllination. the bottle and shake the latter violently until For the estimnation of silver, three standard the chloride of' silver coheres in lumps and the solutions may be prepared as follows: — 1st. A liquid is left perfectly clear. 1)uring this prostrong solution of' chloride of' sodium, by dis- cess of' shaking, the bottle should be kept in solving 5.4145 grins. of' pure chloride of' so- its pasteboard case and( its neck covered with dium in (listilled water, to the volume of 1 a cap of' black cloth, in order that the chloride litre at 16~. of silver may be protected fionm the action of If the salt be absolutely pure, 100 c. c. of lighbt. When the chloride of' silver has cointhis solution will contain a quantity of' chloride pletely settled, turn and incline the bottle so as of sodium equivalent to 1 grin. of' netallic sil- to wash down any of the chloride which has ver, and 1 c.T c. to 0.01 grin. Clean, well remained adhering to its upper part, then recrystallized, native rock salt is pure enough for niove the stopper and add the decimal chloride this purpose. It should be coarsely powdered of' sodium solution, little by little, as Icrg as and dried by a moderate ignition, but should any precipitate continues to be form(ed. The not be fused. decimal solution should be pouire( fiom a bu2d. A decimal solution of the chloride, by rette graduated to tenths of cubic centimlet'es, diluting 50 c. c. of the af'oresaid strong solu- and the bottle had better be held in an intion to the oluine of half a litre, at 16~. clined position so that the drops mall idll (Compare Alkalimetry, p. 18.) Each c. c. of against the lower part of' its neck. The porthis weak solution will correspond to 0.001 tions of the dlecinmal solution first (added mlay grin. of silver. be as large as 0.5 c. c., but afterwards sllallerl 3d. A decimal silver solution, by dissolving quantities should be addedl, in proportion a.s 0.5 grin. of' chemlically pure silver, in 2 or 3 the precipitate produced( is smnaller, an(l c. c. of' pure nitric acidl of' 1.2 specific gravity, towar(ds the close, no riiore than two drops of anil diluting the acid liquor to the volume of thle solution should be added at once. Thlie half a litre, measured at 160. Each c. c. of operation is finished when the last two drops, this solution will contain 0.001 grin. of' silver. fail to produce a precipitate. After each addlliEach of the three solutions should be kept tion of' the decimal solution, the bottle should in a glass-stoppered bottle, and each solution be lifted out of' its case so that the alollult of' should always be shaken before any portion of precipitate prodluced by that alddition illm I)e it is pourerd out for use. The bottle which observedt. Thle bottle should then be shllkell contains the silver solution should be kept in until the liquid beconmes clear, befobre any the dark, by enclosing it in a sleeve of' cloth, more of the (lecimal solution is ral!eld. for examiple. Towards the close of' the operation thle hleig(lht To fix precisely the value of the cloride of of' liquid in the burette shllould be iea(l ofl' m(-,l sodiumn solutions, wei(h out exactly a little noted before each addition. The re-;alln 1bemore than one grammlle of' chemlically pure sil- fbre the last addition (whichl fails to irot duce ver (from 1.001 to 1.003 grin.) and put it in a any precipitate) is taken as the correct ire(,d — white glass bottle of a little nmore than 200 in. Suppose 3 c. c. of the decilll. clilo'i(le c. c. capacity.'This test bottle should be pro- of' silver solution have been used besi(les the vided with a well grounl gIlass stopper, run- 1(00 c. c. of' the stiong solution, and that the ning to a point below. Pour iiito tile bottle 5 amount of' pure silver weighed out was equal CHLORIDE OF SILVER. 145 to 1.002 grins., then 100.1 c. c. of our chloride comparatively large quantity of nitric acid will of sodium will be equal to 1 grm. of silver, be needed, say 10 c. c. for:- It need hardly be added that the results ob1.002:1 = 100.3: (= 100,0998). tained by this preliminary trial are already If by any chance, too much of the decimal tolerably close approximations to the truth. If chloride of sodium solution has been added so the experiment be carefully conducted, the that the exact point of the cessation of pre- quantity of silver present in the alloy can be cipitation cannot be made out, add 2 or 3 c c. determined in this way, to within - or 5. of the decimal silver solution, above de- It is only where the highest possible degree of scribed, and proceed again with the decimal accuracy is required that the second titration salt solution until the point of saturation is ex- with the decimal solutions need be resorted to. actly hit. The amount of silver thus added It is to be remarked that alloys of silver and in the decimal solution must of course be ad- copper are never of absolutely homogeneous ded to the weight of silver originally taken. composition throughout their mass, excepting The value of the standard solution should the alloy of 7-09- silver. The sheets of be marked upon the label of the bottle which rolled metal from which coins are stamped, contains it. It is the fundamental number have often been found to show 1.5 to 1.7 in a upon which all the actual assays or analyses thousand more silver in the middle than at the of silver made by means of that solution will edges. depend. If at any time there is reason to ap- following exaple wil serve to illusprehend that the strength of the solution may trate the manner in which the results of an have altered, its value should be determined assay are calculated. Suppose that 1.116 anew, against a new quantity of pure silver. gris. of American coin have been taken, and For the actual assay of a silver alloy, weigh that 5 c. c. of the decimal solution — 0.5 c. c. out as much of the alloy as will contain about of the strong solution) of chloride of sodium one gramme of silver, or a few milligrammes have been consumed in addition to the 100 more than one gramme, dissolve it in 5 or 6 c. c- of strong solution first added Suppose c. c. of nitric acid in a test bottle as above de- moreover, that the strength of the salt soluscribed, and proceed precisely as in the forego- tion is as above stated, i. e., 100.1 c. c. 1 ing paragraphs. Ir ordler to obtain absolutely gri. silver, then accurate results, it is necessary to know approxi- 100.1 100N::1: 1 mately beforehand, what proportion of silver where x will equal 1.004, the amount of silver is contained in the alloys. In the case of in the alloy. The same result may be arrived coins such as those of the United States and at in the following way: — France, which contain 10 per cent of copper to There was required for precipitating 90 per cent of silver, it will be sufficient to the silver in the alloy...... 100.5 c.c. weigh out a quantity equal to about 1.115 or For 1 grm. of pure silver... 100.1 c.c. of the chloride of sodium solution. 1.12 grm., and an analogous remark would Difference (0.4 c.c apply to English coins, in which the propor- There was consequently 0.004 grm of silver tion of copper is only 7.5 per cent. But with alloys of unknown composition, an approxi-present in the alloy, on approxe-umption that on c. c. of the strong, or mate estimation of the silver value should be. of the trong made before proceeding to the final assay. To 1 c, c. of' the weak, chloride of' sodium solution this end weigh out 0.5 grm. of the alloy,s -or 1 corresponds to 0.001 glm of silver g., in the case of alloys poor in ileldis To dissolve alloys which contain sulphur, solve it in from 3 to 6 c. c. of' nitric acid, and il those a lhilr cons of gol and siler add the strong solution of chloride of sodium, with a slall proportion of tin, Levol (Anales until the last drops produce no precipitate. Cliin. et P1yls., (3.) 44. 347) employs about The operation is conducted in the usual way, 25 grins. of strong sulphuric acid; the mixture as above described, taking care to add smaller is boiled until the alloy has issolved, and th and smaller portions of the salt solution lquidl then treated in the usual was. But towards the close. The reading of the burette since concentrated sulphuiic acid does not disprevious to the last addition is of course taken solve te whole of the silver hen there is as the true reading. much copper present, Mlascazzini (Chenl. CenSuppose 0.5 grlm. of alloy ivas taen, and tralblatt, 1857, p. 300) prefimrs to treat the that 25 c. c. of the chloride of sodium solutioi weighed alloy, which may contain small quanof the above mentioned strength have been titles o lead, tin and antimony, besides gold consumed, the amount of silver in the alloty with tihe least possible quantity of nlitric acid, will appear from the following proportin, as long as red vapors are f'rmled before add ing the sulphuric acid. After the addition of 100.1:2::1 1: x=(0.2497), the latter, the liquid is boiled until the gold and the quantity of alloy to be weighed out has settled well together; the mixture is then will be found by the proportion cooled, diluted with water, and titrated with 0.2497:1.003:- 5: y - (2.008). chloride of sodium, as above. To dissolve this 2 grins. and more of alloy, a It the substance to be analyzed containe 10 146 CHLORIDE OF SILVER. any mercury, some acetate of sodium should be the same number of each is used. Let us added to the nitric acid solution before pro- suppose that, like Mulder, we have a dropping ceeding with the titration (see the description apparaitus, of such size that 20 of its drops are of the gravilnetric method above). equal to 1 c. c.; that to a silver solution there The reason why the value of the standard has been added a decimal chloride of sodium solution of chloride of sodium cannot be ob- solution, until precipitation has ceased, and tained directly from the weight of salt taken, that 20 drops of decimal silver solution have is that chloride of silver is not absolutely in- been used in reaching the point at which that soluble in a solution of nitrate of' sodium. liquid ceased to produce turbidity; it will then And such a solution is of course fbrlned by the be fbund that 20 drops of' decimal solution of reaction of chloride of sodium upon nitrate of chloride of sodium- must again be added in silver. The presence of' nitric acid does not order to arrive at the point at which this liqhinder, or prevent, this solution. Mulder has uid ceases to react. If only 10 drops were shown, for example, that if a solution of 4'- added, instead of the 20 which are required, milligrm. of silver be treated with 50 c. c. of we would be involved in the neutral point. nitric acid of 1.2 sp. gr., and the solution thus Instead of' stopping at the point enjoined in formed be mixed with enough chloride of these pages, at which chloride of sodium has sodium to precisely neutralize the nitrate of just ceased to precipitate the silver, the operasilver, the precipitate which forms at first will tor lnight stop either at the neutral point, or disappear. But the further addition of a trace at the point at which silver solution has just either of chloride of' sodium or of nitrate of ceased to precipitate chloride of sodium. But silver, to the clear liquid thus obtained, will whichever point be chosen, that point must occasion the formation of a persistent precipi- always be adhered to. It would be wrong, for tate. The existence of the clear solution example, to stop at one point when fixing the seems to depend upon that of a certain equi- value of' the chloride of' sodium solution, and librium between the affinities of nitric acid at another in performing an analysis. Accordand chlorine in presence of water, for sodium ing to Mulder, the difference obtained by using and silver. But this equilibrium is at once first the first point, and then the second is destroyed on the addition of an excess of about 0.0005 grin. of silver for 1 grin. of silver either chloride of sodium or nitrate of silver. at 16~. By employing first the first point, It follows from the foregoing that one equiva- and then the third, as was permitted in the lent of chloride of silver dissolved in water is original process of Gay-Lussac, the difference not quite sufficient to precipitate one equiva- is increased to 0.001 grin. - For the ordilnlent of silver dissolved in nitric acid. Unless ary purposes of the laboratory it is usual to a little more than one equivalent of' chloride consider only the first point. If by any of sodium'be used, we encounter the so-called chance that point is overstepped by the addi"neutral point," at which both nitrate of' silver tion of too much of the decimal solution of and chloride of sodium can produce precipi- chloride of sodium, 2 or 3 c. c. of the decimal tates. Hence, if we wish to stop at the point silver solution should be added all at once, of permanent precipitation, the value of' the and the end point again sought for by adding standard solution must be deterlnined by ex- the decimal solution of' chloride of sodium, periment, as above explained.' until precipitation ceases. The silver thus The bearings of' the neutral point upon the added must of course be subtracted fiom the accuracy of' the silver assay, have been care- amount finally obtained, as has been already fully studied by Mulder (in his Silber-Probir- stated. The fobregoing process was (levised methode, Leipzig, 1859). From what has been by Gay-Lussac, Instruction sur l'essai des masaid already, it follows that it' to a silver solu- tieres d'argent par la voie heuaide, Paris, 1832. tion there be added first a strong solution of It has been studied with great care by Mulder, chloride of sodium, and then a decimal solu- Die Silber-Probirmethode, Leipzig, 18&59, whose tion, drop by drop, until no nmore precipitate book should be consulted by all persons specappears, a small precipitate will be again pro- ially interested in the subject.'The account duced on adding a decimal silver solution to of' the method here given has been copied from the mixture; but if the dtecimal silver solution Fresenius's work on Quantitative Analysis. be now added, drop by drop, until the last drop For a modification of the method, proposed produces no turbidity, the atddition of' some of by NMolir,,see below. the decimal solution of chloride of sodium will For the estimation of Chlorhydric Acid, or of again produce a small precipitate. By taking Chlorine, in combination with a metal, a standnote of the number of drops of' the two (leci- ard solution of nitrate of silver may be added mat solutions which are consumed in passing to the liquid under examination, until a prefrom one limit to the other, it will be seen that cipitate is no longer seen to form (compare the description of the silver assay above), or 1 It is to be remarked that Stas, in a preliminary note dictor ay (Comptes Rendus, 67. 1107; Zeitsch. analyt. Chem., an indicator (see Acidimetry) may be em1869, 8. 466), has called attention to the fact, that by ployed to show the point at which the precipusing bromide of sodium as the precipitant, in place of itation ceases. Thus Levol (Journ. prakt. chloride of sodium, silver may be completely precipitated without encountering any neutral point. Chem., 60. 384) has proposed to add to the CHLORIDE OF SILVER. 147 perfectly neutral solution of the chloride to be would be taken as the true result, and it is tested 0.1 volume of a saturated solution of only necessary to measure out that number of phosphate of sodium, and to stop adding ni- c. c. of the silver solution and to dilute it to trate of silver at the moment when a persistent the volume of a litre in order to obtain the yellow precipitate of phosphate of silver ap- standard solution which is desired. Or a dry pears. Since no permanent precipitate of the litre flask may be filled to its mark with the phosphate can torm until the whole of the solution, and 6.14 c. c. of water then added; chlorine has been removed fiom the solut.on, for if' 993.9 c. c. of the solution require 6.1 the formation of a yellow precipitate will indi- c. c. of water to make a litre, then 1000 c. c. cate the fact that all the chlorine has been will need to be diluted with 6.14 c.c. No thrown down. But according to Mohr (Titrir- matter how the mixture is made, take care to methode, 1856, 2. 13) the color of' the phos- close the litre flask with a caoutchouc stopper, phate of silver is too feeble to serve as a really and shake it thoroughly before transferring useful indicator. Long practice with solutions the solution to the bottle in which it is to be of known value would be required to enable kept. It is well to control these operations by the operator to stop at precisely the right mlo- testing the value of the finished solution. To ment. There would always be a tendency to this end empty the burette and rinse it with overstep the mark. In consequence of' this the new solution. Then fill it, and proceed to defect, Mohr (loc. cit.) has proposed to sub- determine how much chlorine is contained in stitute normal chromate of' potassium for the the portion of salt which was weighed out into phosphate of sodium of' Levol, and the idea beaker No. 4. If the standard solution be has been found to be one of' much merit. correct, the number of c. c. of it used multiFor the ordinary work of' a laboratory, a plied by 0.005846 will exactly equal the weight perfectly neutral decimal solution of nitrate of salt taken. of silver (1 litre = 0.1 equiv. HC1) will be The analysis of any sample of chlorhy(lric well suited. To prepare this solution, dissolve acid or of any inetallic chloride is conlducted from 18.75 to 18.80 grins. of' pure fised nitrate precisely like the experiment in beaker No. 4, of silver in 1100 c. c. of water, and filter the care being taken in all cases to hit that identiliquid, if it is not already clear. Weigh out cal shade of' red which the operator had detercarefully into four separate beakers four por- mined upon fbr hinlself. On this account, it tions of pure dry chloride of sodium, each of is best to employ f'or an analysis a solution of from 0.1 to 0.18 grin., dissolve them in 20 or the same bulk and about as strong as that used 30 c. c. of water, and add 3 drops of' a cold, for standardizing the silver solution. It is saturated solution of pure, yellow chromate of best never to operate with excessively dilute potassium to the contents of each beaker. The solutions or with warm solutions, since chrosilver solution, which is a little too concen- mate of silver is soluble to an appreciable extrated, is now allowed to drop slowly fiom a tent, especially in hot water. - The quanburette into one of' the beakers, while the liq- titv of' silver solution consumed in producing uid in the latter is constantly stirred. Each the coloration is extremely small, varying in drop of the silver solution produces a red spot amount between 0.05 and 0.1 c. c..; no very of chromate of silver where it touches the considerable inaccuracy will be introduced by yellow liquid in the beaker; but the red color means of it even in cases where it stands in a disappears instantly on stirring, owing to,the widely different proportion to the quantity of decomiposition of the chroniate of silver by the chlorine from that which obtained in the soluchloride of sodium. At last, however, a slight tions used for standardizing. If the amount red coloration will persist, at the moment after of' silver used for producing a visible coloration all the chlorine in the solution has combined were always the same, it would simply be with silver. Note down the readings of' the necessary to subtract this amount from each burette, and without throwing away the con- and every observation, in order to obtain an tents of this first beaker repeat the experiment absolutely correct result; but since in point of with the salt solutions in beakers Nos. 2 and 3, fac(t more chromate of' silver is required to taking care to stop as nearly as possible at produce coloration in presence of a large mass the moment when the same shade of' red as of chloride of silver, than when less of the chloin No. 1, is manifested. Note the readings of' ride is present, no such deduction can be safely the burette as before, and proceed to calculate made. In spite of this hindrance, the process in each case how much of' the silver solution gives very satisfactory results. - It is to be would have been required for 0.1 equivalent of' observed that'the solution containing the NaCl (i.e., fbr 5.846 grin.). Thus, if 0.11 chloride to be analyzed must be ileutral, for grm. of chloride of' sodium was weighed out, chronmate of silver is soluble in firee acids. If and 18.7 c. c. of the silver solution consumed, need be it must be neutralized by adding nitric then acid or carbonate of sodliumi, before proceed0.11:.846:: 18.7: X:2 =i(993.8). inr with the titration. It had better be a triSuppose the second and third trials give the fle alkaline than at all acid. In case the red value of x as 995 and 993 respectively; then coloration at the close is so strongly marked as the mean of the three numbers (- 99;3.9) to give reason to fear that too much of the 148 CHLORIDE OF SILVER. silver solution has been added, it will be well der by 58.5' 16.1(= 3:.6336). The product to add 1 c. c. of a decimal solution of chloride will express the quantity of chloride of sodium of sodium and afterwards the silver solution in the mixed chloride. Or better, calculate again, drop by drop. The amount of chlorine from the formlul'e of Collier, in which the in the c. c. of salt solution thus added must atomic weight of chlorine is taken as 35.46, of course be allowed for and deducted in the and that of potassium as 39.11 (instead of calculation. 35.5 and 39.1):Attempts to use arseniate of sodium as the W XV — weight of the mixed chlorides; C indicator in chlorine determinations gave weight of' the total chlorine. Mohr (Titrirmethode, 1856, 2. pp. 13, 14) far NaCl= C x 7.611 - w x 3.6288 less satisfactory results than those obtained KC1 W x 4.6288 - C 7.6311. with the chromate. Since arseniate of silver The following formulae by Bosse (Otto's has a dark brownish red color it is much more Lehrtbuch der Chemie, 3 Aufl, 2. 928) may be readily seen than the yellow phosphate, but employed to find directly the amounts of' poits color is always tfar less conspicuous than tassium and sodium in the mixed chlorides: that of the blood red chromate of silver. W = the weight of the mixed chlorides; Indirect Separation of K from Na. See C- weight of the chlorine; x = weight of to it that the mixed Chloride of Potassium and the potassium; and y - weight of the sodium. Chloride of Sodium to be treated is as pure as [(w - c) 1.54 ] - c possible. To this end, redissolve the mixed 0.63 chlorides after they have been once ignited, C - [ (W - C) 0.91 add a few drops of carbonate of ammonium 0.63 and ammlonia, and filter before again evaporat- 1.54= C1 ~ Na; 0.91 = C - K; ing and igniting. Weigh the mixed chlorides, 0.6 = (Cl + Na) - (Cl - K). dissolve them in water and proceed to deter- This method has been recommended by Anmine the amount of chlorine, by means of a thou (Dingler's polytech. Journ., 71. 286) for decimal solution of nitrate of silver, using estimating the amount of chloride of sodium chromate of potassium as the indicator, as in commercial chloride of potassium. Anthon above described. Calculate the amounts of (loc. cit.) has, moreover, constructed a table potassium and sodium, as explained below. from which the percentage amount of chloride The process is easily and rapidly executed of potassium in any mixture may be obtained and yields perfectly satisfactory results when at a glance from the number of c. c. of silver the mixed chlorides are free from impurities. solution used. But Fresenius (Zeitscbh. analyt. It answers best for the analysis of mixtures Chem., 1862, 1, 110) urges that a process so which contain tolerably large quantites of dependent upon the purity of the mixed chlorboth the metals. As in all similar indirect ides can hardly be employed with safety, for methods, the errors of observation are mul- the analysis of' commercial products. It adtiplied in calculating the results. (F. Mohr, mits of calculation that a commercial chloride Zeitsch. analyt. Chem., 1868, 7. 173). of potassium containing 88 per cent of KC1, According to experiments of Collier (Am er- 10 per cent NaCl and 2 per cent of foreign ican Jour. Sci., 1864, 37. 344), the process salts, such as sulphates or nitrates, would reis equal in accuracy to the method of direct quire as many c. c. of' decimal silver solution analysis by means of Chloroplatinate of Po- as correspond to only 3 per cent NaC1 instead tassium. of the 10 per cent actually present; the presThe calculation is as follows (Compare Car- ence of only 2 per cent of foreign impurity bonic Acid, indirect separation of Ca from being sufficient to introduce an error of 7 per Sr):-Suppose the mixed chlorides weighed 3 cent in the process. For the application of grms. and there was found 1.6888 grin. of the method to the estimation of Carbonic chlorine. Calculate how much KC1 this chlor- Acid, see p. 91. ine would indicate if there were no sodium Ilohr's method of estimating Silver, is a mere present: - thus application of the foregoing process of determining chlorine. A measured quantity of Atomifc Moleciar Wt.offound; 3.5497). standard chloride of sodium solution, more C1 35.f5' 17t4. 1.6888 than sufficient to precipitate the whole of the The difference between x- 3.5497 and the silver, is added to the substance to be anaweight (3 grtns.) of the mixed chlorides ac- lyzed, and the excess of chlorine thus employed tually found is proportional to the weight of is then estimated by means of standard nitrate chloride of sodium in the mixture. Thus, of silver, using chromnate of' potassium as the indicator. Since chromate of silver is someDifference between Molec. wt. Difference Wt. of the molec. weights of aC1:; as above:NaClin y (=1.9974). what soluble in water, care must be taken not KCI and NaC1 16.1'58. 0.5497 mixture to operate with dilute or with warm solutions. Whence the short rule, multiply the quan- Though probably somewhat less accurate than tity of chlorine in the mixture by 74.6' the ordinary method of estimating silver, this 35.5( = 2.1014), deduct from the product the process may nevertheless be sometimes found sum of the chlorides, and multiply the renmain- useful in the laboratory, especially in cases CHLORIDE OF SILVER. 149 where the proportion of silver in the substance down any chlorine admixed or in combination. to be examined is wholly unknown. - The Before transferring the mixture to the measurdetails of the process, as applied to the assay ing cylinder, it should be cooled by immersing of silver coin are as fbllows: —Weigh out a the flask in cold water. Instead of taking the sample of the alloy (say 1.08 grui.) and dis- red color of chromate of silver as the final solve it in a flask in the least possible quantity point, the appearance of that color may be reof warm nitric acid. Pour. from a burette garded only as a first approximation to the into the solution of the coin, a decided excess truth. After enough of the decimal solution of of a decimal solution of chloride of sodium. nitrate of silver has been added to produce the This salt solution may be a(lded by portions of persistent red coloration, a decimal solution of 10 c. c. each until there is manifestly an excess chloride of sodium may be made to fall drop by of it in the mixture. The free acid and the drop upon the mixed precipitate of chloride copper in the solution must be got rid of' before and chromate of silver as long as any lighter proceeding to determine the excess of chlorine shade of color can be distinguished at the which has been used. To this end heat the place where the drop first touches the cloudy contents of the flask to boiling, throw in liquid. In this way the excess of silver recrystals of' carbonate of sodium, free from quired to produce the red coloration may be chlorine as long as any effervescence occurs, annulled and eliminated. The chloride of and continue to boil until the oxide of copper sodium thus added must of course be considhas turned black. Then pour the mixture of ered, and allowed for in calculating the results liquid and precipitate into a narrow, graduated of the experiment. If the operator prefers to cylinder of 150 c. c. capacity, rinse the flask work backwards with chloride of sodium, as with water and fill the cylinder to the 0 mark just indicated, the preliminary experiments with water, taking care to measure at about made to familiarize him with the proper color 160. Close the mouth of the cylinder with a of chromate of silver may be omitted. It sheet of greased vulcanized rubber, held in will only be necessary to Irepare the decimal place by the palm of the hand, and shake the solutions, by dissolving 5.846 grm. of pure, mixture thoroughly. Let the solid matter set- dried chloride of sodium in water, and diluting tie; by means of a pipette transfer 50 c. c. of to the volume of' a litre, and by dissolving the clear supernatant liquid to a beaker; add 1.08 grm. of' pure silver (or an equivalent 2 or 3 drops of a solution of yellow chromate amount of pure, fused nitrate of silver) in of potassium and estimate the amount of' chlor- nitric acid, evaporating to absolute dryness to mne by means of standard nitrate of silver as ensure neutrality, and dissolving in water to explained above. Multiply the number thus the volume of a litre. (Mohr, Titrirmethode, obtained by three, and subtract the chloride of 1856, 2. 54). sodium thus found from the amount of that Volumetric estimation qf combined sulphuric substance first added to the solution of the al- acid. A process devised by Grmeger (Zeitsch. loy; the difference will be equivalent to the analyt. Chem., 1867, 6. 443), for determining silver in the alloy. - The rule just given, sulphuric acid in sulphates, depends essentially to multiply by three, is not absolutely correct, upon the principle now under consideration. since it is not a clear solution of' chloride of It is as follows.- Dissolve the sulphate (of an sodium, but a mixture of liquid and solid mat- alkali metal) in water, add a solution of chloter, which is diluted to 150 c. c. The 50 c. c. ride of barium in slight excess, and then, withtaken out do not represent absolutely a third'out filtering, digest the mixture for a short of the solution; but the error is triflin;g in any time with an excess of carbonate of silver. event, and is wholly insignificant when only a By the action of this agent, the metallic chloslight excess of chloride of sodium is added to ride which was formed by the action of the the solution of the alloy. chloride of barium upon the sulphate is deInstead of the mixing cylinder, a marked composed, together with the excess of chloride flask of 150 c. c. capacity may be used. of barium employed, and converted into chloIt is necessary to boil thoroughly after adding ride of silver and a carbonate of the alkali the carbonate of sodium, for carbonate of cop- metal. The chloride of silver, admixed with per is somewhat soluble in water and if any of the excess of carbonate of silver and the it be left undecomposed, a coloration will be carbonate of barium resulting from the decomproduced by it on the addition of the chro- position of the excess of chloride of barium, are mate of potassium. When the operation is separated by filtration, and the amount of properly conducted, however, the liquid is left carbonated alkali in the filtrate is determined so free from copper that not the slightest pre- by means of standard nitric acid (see Akalimcipitate or coloration will be perceived on add- etry or Carbonate of Potassium). From the ing to it sulphide of ammonium. The precipi- amount of alkali found, calculate an equivatate produced by the carbonate of' sodium lent quantity of sulphuric acid. A trace of consists of chloride of silver as well as of oxide carbonate of barium always remains dissolved of copper, but the chloride of silver is not in in the solution, and goes to increase the the least acted upon by the boiling carbonate amount of alkali. - In case the sulphate of sodium, nor does the oxide of' copper carry to be analyzed is mixed with a carbonate and I50 CHLORIDE OF SILVER. a chloride of an alkali, three separate nmeas- iodine in presence of chlorine. Separation of ured portions of the solution must be treatedl; Ag fromn Sb, As, Bi and Hg. The first portion is titrated at once with Alethod(s. See Bromide of Silver, Chloride standard nitric acid; in the second portion, of Sulphur, and the Chlorides of the metals acidulated with nitric acid, the chloride is de- above enumerated (volatility of). In case it is termine(l as Chloride of Silver, by means of desired. to remove the chloride of silver from standard nitrate of silver and chromate of the bulb tube, in order to weigh the latter, repotassium, while the third portion is neutralized duce the chloride by heating it in a stream of with nitric acid, and treated with chloride of hydrogen, and dissolve the metal in nitric barium anal carbonate of' silver, as above de- acid. - According to Stas, chloride of silscribed. The amounts of alkali found in the ver fused in chlorine gas absorbs traces of first portion, an(l that equivalent to the chlo- chlorine, and does not give up the whoJe of the rine f'ound in the second portion. must of' course gas on cooling. In very delicate experiments, be substracted from that found in the third therefore, the chloride nmust at the last be portion, beft're proceeding to calculate the heated in a stream of carbonic acid to expel sulphuric acid. this adherent chlorine. Stas found that about According to Gruager the process is applica- 100 grins. of chloride of silver lost 7.13 millible to all sulphates whose bases can be coni- grammes on expelling the absorbed chlorine. pletely precipitated by means of alkaline car- Prircip/e VII. Solubility in anlnonia-water. bonates, and particularly for the analysis of Applications. Separation of silver from mineral waterl's. It is onlly necessary to de- lead. Separation of chloride of silver from compose the sulphate by means of a measured sulphide of' silver in estimating chlorhydric quantity of standard carbonate of sodium, and acid. to proceed as above. - In order to gain an JMethod. To separate silver from lead, add idea of'how nmuch carbonate of silver should chlorhydric acid to the mixed solution, and be used in any given instance, it is well to esti- immediately afterwards a large excess of ammate the chlorine by titration, in a small ineas- monia-water. Basic Chloride of Lead will ured portion of' the liquid, after the action of remain undissolved. Filter and acidulate the the chloride of barium, and to calculate from filtrate with nitric acid to throw down the this result how much of' the silver salt will be chloride of silver, which collect and weigh, as needed.. A slight excess of it should always above. In order that the chloride of silver be enmployed. In using this process it should may dissolve freely, it is important that the be remembered that carbonate of silver is amnmonia-water be added immediately after slightly soluble in aqueous solutions of the al- the precipitation. Themixture should be kept kaline carbonates. from the light. The process does not yield For Carius's method of estimating chlorine very accurate results, since more or less of the in organic compounds, see Nitric Acid, oxidiz- chloride of silver remains dissolved in the ing power of, and Iodate of Silver. nitrate of ammonium, and is lost in the filPrinciple II. Reduction of to metallic trate. - In separating chlorine from metsilver by hot hydrogen. als, it often happens that the latter must be Application. Estimation of silver in chlor- thrown down by sulphuretted hydrogen before ide of' silver and of chlorine in presence of the estimation of the chlorine can be probromine. ceeded with. It is possible in that event, Method., Se,' Bromide of Silver. though not as a rule advisable, to add nitrate Principle IT. Reduction of by metallic of silver directly to the filtrate from the metzinc. allic sulphide, and to dissolve out, by means of Method. See Silver and Silver Compounds. ammonia-water, the chloride, of silver from Principle V. Reduction of, by hot alkaline the mixed precipitate of chloride and sulphide carbonates. of silver. The process is involved, however, Applications. Separation of chlorine from and the determination of chlorine less trustsilver. Estimation of chlorhydric acid in cer- worthy than it would be if the sulphuretted tain cases. hydrogen were removed in the usual way, by ~Method. Mlix the chloride of silver with 3 means of ferric sulphate, before adding the times its weight of a mixture of carbonate of nitrate of' silver, sodium and carbonate of potassiunl, and ignite Principle VIII. Conversion into bromide the mixture in a porcelain crucible until the of silver by Bromide of Potassium (Wittstein's materials begin to agglutinate. On treating Method). See Iodide of Silver. the cold mass with water, the metallic silver Properties of Chloride of Silver.. When will be left undissolved, while the alkaline recently precipitated, chloride of silver is chloride goes into solution. The chlorine may white; but on exposure to light it changes to then be determined in the manner described violet, and finally to black. A small amount above under Principle II. of' chlorine is lost during this transformation, Principle VI. Fixity when heated in chlo- and some dichloride of silver formed. Though rine. the change is superficial, it is attended with an Ap/plieationr Estimation of bromine and appreciable loss of weight. When the chloride CHLORIDE OF SODIUM. 151 which has been darkened by light is treated separating chlorine from platinum, mix the with ammonia-water, there is left undissolved solution of the platinum compound with a soa small quantity of' metallic silver, resulting lution of carbonate of sodium, evaporate the from the decomposition of the dichloride. mixture to dryness upon a water bath and fuse On (lrving, the chloride becomes pulverulent, the residue in a platinum capsule. Dissolve and yellow-colored if strongly heated. It out the chloride of sodium with water and esfuses at 2600 to a transparent yellow liquid, timate the chlorine as Chloride of Silver which solidifies to a white or yellowish horn- (Zeitsch. analyt. Chem., 1870, 9. pp. 30, 31). like mass on cooling. At high heats it vola- Estimation of chlorine in organic comnpounds. tilizes unchanged. It can be easily reduced to [Compare Chloride of Potassium]. In many the metallic state by means of zinc and iron, easily decomposable organic conlpounds, such and by hot hydrogen, coal gas and carbonic for example as the substitution products of oxide, but not by ignition with charcoal. acids, chlorine (bromine or iodine) may be deThe fresh precipitate has a peculiar curdy termined by leaving the substance fobr several consistency, and its particles tend to cohere to hours in contact with water and sodium amallarge lumps when the liquid in which they are gamn, until decomposition is complete, then suspended is agitated. In order to obtain per- acidulating with nitric acid and estimating the fect coherence of the particles, and, as a con- chlorine as Chloride of Silver (Kekuld). sequence, a clear supernatant liquor, it is best Principle II. Sparing solubility in alcohol. to have a solution of silver slightly in excess Applications. Separation of C1 from Br in the liquid,. and from I. The precipitate is exceedingly sparingly sol- 1lMethod. See Bromide of Sodium, solubility uble in water, and in dilute nitric and sulphu- of. ric acids, but dissolves rather easily in chlorhy- Principle HIL. Solubility in water. dric acid, especially when the latter is hot and Applications. Estimation of water in orconcentrated. From the solution in strong ganic solutions, particularly in beer and in chlorhydric acid, it is precipitated almost coin- milk. Valuation of beer and of milk. pletely on the addition of water. On being kept in contact with water for some hours, even in the dark, chloride of silver decomposes A. Fuchs's hallymetric beer test. Since 100 very slightly, and becomes gray, more chlorine parts of water at temperatures between 150 than silver being dissolved; in hot water this and 40~ dissolve almost precisely 36 parts of change is more rapid, but it is slight in any pure chloride of sodium, it is possible to estievent. - Chloride of silver is soluble in solu- mate the amount of water in solutions of many tions of all the metallic chlorides which are solu- organic bodies by adding a weighed quantity ble in water; also, to a certain extent, in solu- of salt in excess to the aqueous liquid and tions of various nitrates, especially when the afterwards determining the amount of salt solutions are hot and concentrated. It is readily which remains undissolved, time enough being soluble in various cyanides and lhposulphites. allowed of course for the water to become Concentrated solutions of caustic potash and saturated with the salt. Suppose, for examsoda decompose it, especially when they are ple, it be found that 315 grains of salt have hot. When recently precipitated, ammonia- been dissolved by a given sample of beer then water. dissolves it easily, but after having 56:100:1 316: x(= 75 = been kept fLr a long time and boiled with wa- the amount of water in the sample). - The ter, it dissolves with difficulty (see also above). chief difficulty in the process is to estimate Solutions of the carbonates of potassium and quickly and accurately the salt which remains sodium only decompose traces of it even on undissolved. For this purpose Fuchs (Dingboiling. Chloride of silver is perceptibly soluble ler's polytech. Jour., 1836, 62, 309) employs a in warm tartaric acid, but is less soluble in the measuring tube about 20 c. In. long. At the cold. Both bromide and iodide of potassium top this tube is 4 c m. wide, but Just below transform it completely to Bromide or Iodide the middle it is contracted to such an extent of Silver, as the case may be. Its composi- that the lower half of the tube is no wider tion is thai 1 c. in. To make such a tube, two tubes f108.. 75.2 of the different sizes must be fused together, C35.6, * 24-74 the larger tube being drawn down sufficiently 143.i 100.00' to correspond with the narrower one. The Chloride of Sodium. lower, narrow part of the apparatus is gradP'rinciple 1. Fixity at moderately high uated so that each fine mark shall repretemperatures. sent one grain and each heavy mark five Applications. Estimation of sodium in the grains of moist chloride of sodium of the dehydrate, chromnate, chlorate, silicate, sulphide gree of fineness and compactness to be deand carbonate of that metal, and in its salts scribed directly. The first tube of this kind with various organic acids. Separation of Cl must be graduated by means of powdered salt from Pt. wet with a saturated solution of salt, but afMethod. See Chloride of Potassium. In ter one tube has been made copies of it may 162 CHLORIDE OF SODIUM. be multiplied to any extent, by means of quick- the beer be expelled. It is well to set the silver. - For calibrating this hallymeter as flask in a dish of water, which is kept at 370 well as for the subsequent beer tests, Fuchs or 38~, and to shake it or rather twirl it about employs chemically pure salt of such a degree from time to time. Only 5 or 6 minutes are of fineness that it will pass through a sieve really needed to complete the solution. At the holes in which are 0.0673 Paris lines the expiration of that time, cool the flask by broad and 0.0757 Paris lines long, the thick- illmmersing it in cold water, blow a little air ness of the brass wire being 0,0458 Paris lines. into the upper part of the flask to expel carTo graduate the tube weigh out 600 grains of bonic acidl, wipe it dry and weigh it, the loss water, which would be enough to dissolve 216 of weight represents approximately the cargrains of' salt, add to it 221 grains of salt or 5 bonic acid; in good Bavarian beer it will grains more than it can dissolve, and as soon amount to about 1.5 grains. Then pour the as solution is c mplete bring the mnixture of contents of' the flask into the measuringg tube, salt and liquor into the tube, taking special taking care as before to lose no particle of the care that no particle of the solid salt is lost. salt. If any of' the salt clings to the side of The solution lmay be effected in a small flask, the flask it may be washed out by pouring back and the salt transferred to the Ineasuring tube some of the liquor from the upper part of the by closing the flask with the thumb, inverting measuring tube or by means of' a saturated soit and( shaking the liquid until all the salt has lution of' chloride of' sodium. - Special care fallen upon the thumb. On now holding the mlust be taken both in graduating the tube and flask over the measuring tube and loosening in measuring the undissolved salt, in an actual the thumb the whole of the salt will be washed experiment, to make the salt settle down into from the thumb into the tube, It will be ob- the smallest possible space in the measuring served that the upper part of the measuring tube. To effect this, clasp the tube at the midtube which serves as a mere reservoir fobr liqp (Ile with the thumb and curved forefinger of uids is made large enough to hold a consider- the left hand so that it mnay be supported in a able quantity. As soon as the salt is in the vertical position and be fi'ee to move up and tube rap the- latter repeatedly against the ta- down, then with the thumb and finger of the ble in the manner described below, in order to right hand take hold of the very bottom of the bring the particles of' alt to the proper degree graduated tube, lift the apparatus to a disof compactness; make a fine mark upon the tance of about 0.25 inch above the table and tube and number it'"5." Then emnpt the let it drop back so that the bottom of the tube tube, wash it with water, dry it with blotting may strike the table with a shock. Repeat paper and repeat the operation so as to make this operation many times, working with such other marks correspondling to 10, 15, 20, etc. rapidity that the tube shall receive about 100 grains, of salt. In each case the necessary ex- blows per minute. Take care to hold the tube cess of salt, over and above what 600 grains upright and to have the blows follow one of water caln dissolve must be weighed out. another with precision and regularity. After It will not answer to add fresh portions of about two minutes thrust a wire into the tube powdered salt to the liquid in the measuring and without actually stirring up the salt move tube, for the powder is not of uniform fineness, it about gently to expel any little bubbles of and since in actual practice the finer particles air which it may have entangled. Then reof the powder dissolve first while the coarser move the wire and continue to tap the tube particles are left to be measured, these condi- against the table as before as long as the salt tions must be insisted on in the operation of continues to sink upon itself. This operation calibration. For the beer test, it will not be of settling usually consumes about 15 minutes. necessary to make more than 7 or 8 of these When the salt lias ceased to settle note the coarse divisions. The subsidiary divisions, mark and fraction of a mark upon the tube to each representing 1 grain of salt mnay be filled which its surface corresponds and proceed to in by means of a dividing machine; care calculate how much water the dissolved salt having cf course been taken in the first place represents, in the manner indicated above. to choose a tube of uniform bore for that part For the second experiment, which is to deof the apparatus which is to be graduated, termine the extractive matter in the beer, In testing beer two experiments are made; weigh out 1000 grains of the liquid in a flask the 1st, to determine the amount of water and and evaporate it in the flask to about one-half carbonic acid, and the 2d to (determine the in order to be sure that the whole of the alcoamount of" extractive matters" in the beer. hol has been expelled. It is well to heat the For the first experiment, weigh out (but do not flask upon a sheet iron plate by means of a measure) 1000 grains of the beer in a small lamp,, but the heat must be very gentle at first, flask, add to it 330 grains of the powdered and lest the liquid boil over through the too rapid sifted salt, cover the flask with a glass plate escape of carbonic acid. If this catastrophe and counterpoise it upon a tolerably delicate threaten the flask should be immediately rebalance. Iii order to facilitate solution and to moved fi'oln the fire and gently agitated or expel carbonic acid, heat the flask carefully, twirled around. A rather larger flask should but not above 38~ lest some of the alcohol i. be taken for this experiment than for the first. CHLORIDE OF SODIUM. 163 After the first tempestuous oscape of carbonic Application. Indirect separation of K from acid is over the liquid will boil gently and may Na. be left to itself:'. When half the original li(l- Mlethod. The chlorides of the alkali metals uid has evaporated remove the flask from the are easily changed to nitrates by means of nifire, immerse it in cold water in order to cool tric acid. If enough nitric acid be taken a its contents, wipe it dry and by means of filter single evaporation to dryness will expel the paper remove any drops of water which may last trace of chlorine. The converse process have condensed in its neck. Then weigh it of changing nitrates to chlorides by means with its contents. Next pour into it 180 of chlorhydric acid, is far more difficult. grains of tile powdered salt and proceed to The process consequently consists in simply determine how mluch of this salt is dissolved treating a weighed quantity of the mixed by the li(luid, precisely as in the first experi- chlorides with nitric acid in an evaporating ment By subtracting the weight of water dish loosely covered with a watch glass, evapthus found fromn the weight of the concentra- orating to dryness and weighing the residue. ted liquid weighed, the weight of the so called The calculation is as follows:extractive matters is obtained. By subtract- Call the weight of the mixed chlorides S, inc water, extractive matters and carbonic and that of the mixed nitrates, obtained thereacid from the original 1000 grains of beer the from, R; the weight of the KCI in the mixweight of' the alcohol is obtained. Ac- ture a and that of the NaC1 b, then cordling to Fuchs, the results obtained by this S a - b; a S - b; and b = S - a, but process are satisfactory and useful fbr the com- a grms. of KCI will yield 1.355 X a grms of parison of different kinds of beer. The sub- KNOs and b grins. of NaC1 will yield 1.453 X b stances here classed as extractive, exert little.grms. of NaNO3, for or no influence upon the solubility of the salt Molec. wt. Molec wt. in water. The chief merit of the method of of KNC: of KNO8:3 Gr 1 Gr(=1. K5), course consists in its rapidity; the complete and examination of a sample of beer requiring Arolee. wt. Molec. wt. Grm. NaCl Grm. NaNO8 only about two hours time. Tables giving the NaC168.8 NaNO 85 1 1.453 amount of alcohol and of extractive matter in hence 1000 grains of beer for each grain of undis- X a 1.453 X b= R. solve(l salt will be found in Fuchs's memoir. By substituting for b, in this equation, its value B. Reichelt's milk test. Weigh out 1000 (S - a), we have grains (=. 62.5 grmns.) of the milk to be tested, 1.365 X a + 1,453 X (S -a) = R, add to it 324 grains ( 20.25 grins.) of chlor- 1.43 S - R = 0.098 a, ide of sodium Ad 240 grains of a solution of and litmus saturated with common salt. The chief a = 1.4&3 - R purpose of the litmus solution is to color the or milk so that the undissolved salt can be seen Chloride of Potassium = a = 14.88 S - 10.2 R. and measured, but it is found also that the ad- Chloride of Sodium = S - (14.83 S - 10.2 R); or dition of this salt solution improves the con- Chloride of Sodium = b = 10.2 R - 14.83 S. sistency of the milk and facilitates the deposi- Reckoning backwards, tion of the undissolved salt. After time The Nitrate of Potassium X 0.7375 = the enough has been allowed for the salt to dis- Chloride of Potassium; and the Nitrate of solve in the milk, the mixture is transferred to Sodioum X 0.6877 =the Chloride of Sodium. the mieasuring tube precisely as in Method A, (Mohr, Zeitsch. anal yt. Chem., 1868, 7. 175.) see above, and the experimnent finished as Properties. Chloride df sodium is much there (lescribed. Illn one experiment, 4 grains less readily soluble in chlorhydric acid than in of salt were found to have remained undis- water. It is nearly insoluble in absolute alsolved. 1000 grains of the milk had conse- cohol and only sparingly soluble in spirit. It quently dissolved'24 - 4 - 320 grains which fuses at a red heat without decomposition but are equivalent to 888.89 grains of water, for volatilizes in white fumes at a white heat; or 36: 100 = 320: 888.89. at a bright red heat, when heated in an open The percentage of solid matter in the milk was vessel. It is less volatile, however, than chlorconsequently 100 — 88.90 — 11.10. An ex- ide of potassium. In fusing salt, care must be perirnent made for the sake of control by the taken to prevent the flame from touching it, method of evaporation gave 11.03 solid matter for in that case some chlorhydric acid would and 88.97 per cent water. The method seems escape and a little carbonate of sodium be to be as accurate as that in which the milk is formed through the action of carbonic acid mixed with a known weight of quartz sand and water resulting from the fire. When exand evaporated at 1050-110~, and is of posed to moist air even pure salt will slowly course far more expeditious (Reichelt, Wag- absorb a little water. Crystals of salt decrepiner's.Jalresbericht Chem. Tech., 1859, 5. tate on being heated owing to the escape of a 443). little moisture which they retain. To avoid Principle IV. Decomposition of by nitric loss firom this cause, carefill (Irying is essential acid. (See Chloride of Potassiumn). On being evap 154 CHLORIDE OF SULPHUR. oratedl with oxalic or nitric acids, or ignited senic, antimony, mercury, etc., go forward with oxalate of' amnmonium, chloride of sodium with the chloride of sulphur. The chloride of' behaves like chloride of potassium. It compo- sulphur on cominog in contact with the water in sition is the flasks is decomposed to chlorhydric and cN = 23 39.31 hyposulpliurous acids, with separation of some Ci = 35.5 60.69 s58. i0- fiee sulphur. The hyposulphurous acid decomlposes again to sulphur and sulphurous acid Foer use as a reagent, perfectly pure native and the latter is converted into sulphuric acid, roek salt is well suited. Or, pure salt may be by means of' the chlorine with which the water prepared, after Margueritte, as follows: —Pass and the flasks is filled, so that the final prodchlorhydric acid gas into a concentrated solu- ucts are sulphuric acid and more or less fiee tion of common salt as long as any of it con- sulphur. The current of chlorine should be tinues to be absorbed. Throw the small crys- slow from first to last, and the flasks as well as tals of salt, which are deposited, into a funnel, the rest of' the apparatus should be fuill of let them dirain thoroughly. wash with chlorhy- chlorine before the contents of the bulb tube dric acid and finally dry them in a porcelain are heated. dish to drive off the last traces of free acid. At the end of the operation the sulphur is In drying salt before weighing it for the prep- collected upon a tared filter, washed, dried aration of standard liquors, it slould not be and weighed, and the sulphuric acid is estifused, but ignited nloderately, powdered mated in the filtrate as Sulphate of Barium. roughly while still warmn and placedl in a The metals of any volatile chlorides which weighing tube which admits of being closed. have gone forward, may be estimated in the Pure salt will dissolve in water to a clear liq- filtrate fiotm the Sulphate of Barium. The ui(l and the solution will not become cloudly chloride which remains in the bulb tube is when tested with oxalate of' anmmonium, phos- weighed as such if it be chloride of silvelr phate of sodium and chloride of' barium. chpolride of lead or any other fixed chloride, or, Chloride of Sulphur. it' need be, it is dissolved in chlorhllydric acid, Principie. Volatility of: aqua regia or other suitable solvent and subApplication. Separation and estimation of jected to analysis. - Ill heating the bulb sulphur in metallic sulphides, especially those tube it is not necessary to wait until the whole of complex composition. of the fer'ic chloride is expelled, in case any llIeth4Sd. Weigh the powdered sulphide in a be present; but care should be taken to drive tolerably long, narrow, glass tube, closed at all the chloride of sulphur and other volatile one entl, so that the powder may be poured chlorides as far forward towards the water in therefiom into a bulb tube without soiling the the flask as may be practicable. When the stems of the latter. Attach to one end of the bulb has become cold cut off its bent stem, and bulb tube an apparatus for generating dry in case the latter contains a portion of the chlorine and to the other a couple of large IJ volatile metallic chlorides, close it by inverttubes or small flasks to serve as receivers of the ing upon it a moistened glass tube closed at chloride of sulphur. Fill each of the flasks one end and leave it at rest for 24 homlrs. about one quarter full with water, or if anti- When left in this way the chlorides will slowly mony be present, with a solution of tartaric absorb moisture and dissolve without evoluacid in dilute chlorhvldric acid. [Compare tion of' heat. Finally rinse out the bent part the description of Lin(lt's arrangement for ab- of' the bulb tube with dilute chlorhydric acid, sorption in soda lye, below]. One end of the and gently heat the contents of the flasks or U bulb tube should be bent so as to reach nearly tubes to expel the chlorine, before proceeding to the surface of' the water in the first flask or to collect the sulphur. The sulphur is apt to U tube. Beyond the last flask there should be separate in liquid drops. If need be, time an abduction tube reaching to the chimney or should be allowed for these (Irops to become into a large bottle loosely filled with pellets of solid before filtering. - Compounds of the paper wet with alcohol, so that the excess of sulphides of arsenic, antimiony or tin, with bachlorine may not incommode the operator. sic sulphides, may be decomlposed in this way Before attaching the bull) tube to the chlorine in the course of a few hours, but simple sulgenerator wait until the latter and the wash- phides such as those of lead, silver, copper, coIng bottles connected with it are completely bait, manganese, etc., require a much longer full of' chlorline. Pass a slow current of' chlor- time and need to be heated far more strongly. ine through the bulb tube in the cold, until no Several days would be required to completely further alteration of the sulphides is observed. decompose a few. grains of sulphide of' lead. Their heat the bulb very gently, taking care (Berzelius and Rose). also to keep the outlet of the bulb tube warm Instead of absorbing the chloride of sulso that no volatile metallic chloride shall con- phur in water as above, Lindt (Zeitsch. analyt. dense in it and stop it. By the action of the Chem., 1865, 4. 370) employs soda lye. He chlorine the sulphides are cornpletely changed heats the sulphide, moreover, in a porcelain to chlorides, most of which remain in the bulb, boat instead of a bulb tube. The apparatus is though volatile chlorides, such as those of ar- arranged as follows:- Blow two bulbs upon a PROTOCHLORIDE (IF TIN. 155 tolerably long glass tube, the diameter of chloride is added to the solution to be reduced which is sufficient for the admission of a small and analyzed, and the portion of the tin salt p rcelain boat. One of the bulbs may be which has escaped oxidation determined. The close to one end of the tube, but the other oxidizing solution may be biChronlate of Pobillb should be six or eight inches from the tassium (after Streng and Penny), Permnanend. Bendl the tube' close to the last men- ganate of Potassium (after Schlagdenhauff'en), tione(t hulb at a right angle, taking care to Iodline in alkaline solution (after Lenssen), or le tve the outer six or severn inches of the tube Io(line, in iodide of potassium solution (after horizont:dl, for in that part of' the tube the boat Fresenius). is subseeluently placed. At a point 2 or 3 1. Chloride of tin (gainst biChroiate of inclhes below the bulb in question, bend the Potassiulm tube again to a slightly acute angle. At this As will be seen under biChromate of Potasstuage of' olerations there will be the outer six sium, the oxygen dissolved in the water in or seven inches of horizontal tube, say at the which the analyses are made has much influleft of the bulb, then a short vertical tube, ence upon the'correctness of' the result. The near the top of which the bulb is situated, action of' this (lissolvedl oxygen is peculiar. and to the right of' the bulb a length of 10 or It differs totally according to circumstances. 12 inches of' tube sloping upwards somewhat Thus while ferrous salts can be titrated with towar(ls the right hand, and bearing a bulb at p'rlnlanganate of potassium without a particle its outer end. Bend the tube once more close of' the,xygenl in the water taking part in the to this outer bulb so that the bulb shall point oxidation. it is wholly dlifferent when stannous upwards and be in the slame plane with the salts (or s'ulphurous acid) are treated with the other bulb or rather a little higher than the perlmananate. In the latter case alnmost the la.ter. Fix the tube in a wooden clamp so whole of the dissolved oxygen suddenly unites tilht the outer six or seven inches shall be hori- witli the stanlous oxide the moment tile stanzontil, pour enough soda lye into the outer nous salt and permianganate are nlixed. The bulb to fill the lower sloping part of' the tube, dissolved oxygen seemls, in fact, to be thrown push the loaded porcelain boat into the hori- into an active state at the moment when the zontal lpart of the tube and connect that ex- pel1)anganate acts upon a stannous salt, or tremnity of' the tube with a chlorine generator. upol stliph'urous acid, while it remains wholly Attach also a caoutlchou tube to the outer passive when other reducing agents are treated bulb to lead awa.y the excess of chlorine. in its presence with the permlanganate. What The chlloride of sulplhur on coining in con- is true of' the pernianganate is true of chrotact with the soda lye is immnediately decoll- mic acit, and of several other reagents. posed with formation of sulphide, hyposul- As regards the stannous salts, experiments phite, chloride aned hypochllorite of sodium. have shown that the oxygen d(issolve(l in waThe decomposition of' the lnetallic sulphide is ter is renlelel active, an(l that it unites with soon completed, but it is well to continue to the tin in the case of the following oxidizing pass chlorine through the apparatus for a agents: - Clhriomic acid and chlromates, percouple of hours, in oriler that some chlorate of manganate of potassiuml, chlorous and hyposollitumn m-iay be formedl. After the porcelain cllloric acids, pelroxide of hydrogen and ozone. boat has been removed, wash out the liquid 3But that it remains inactive, and has no influfrom the tube into a p)orcelain dish, evaporate ence upon the reaction when the tin salt is to dryness and ignite strongly to decompose oxi(lized with brolmine, chlorine, hlypochlorous the cllloiate of sodliuim. No violent action oc- acid, iodlic acid. terl'ic or cIIptic chloride, orl a curs (duiing this ignition and at its close all solution of peloxi(le of lead (Lenssen and Lethe sulphur will be fbund to be in the condi- wentlhal, Jour,. piakt. Che7n.,'1862, 86. pp. tion of Sulphate of' Sodium. Determine it as 193, 205, 214). - It has been repeatedly Sulphate of Barium. shllown that the influence of the (lissolved oxy-.pro'oChloride of Tin. gen in the titration of' chlioride of' tin may be Pri'iciple. Reducing power of. annulled or' avoided by adding a certain quan-,Applications. Volumetric estimation of Sn, tity of' ferric chloride to tlhe solution. Lenssen Fe, Hg, Cu, Pb, Mn, CGo, Ni, C1, Br, I, and an;d lewenthal have corioborated this observachrolmlic, chloric, sulphurous and ferricyanhy- tion, an(l explain thle fact by supposing that drie acids. Indirect gravimetric estimation of SnC12 and 2FeCI3 (tecompose one another to protoxi(le of tin in presence of the binoxide. form SnClI and 2FeC12, and that the last Mlethods. See biChromate of Potassium, named compound is really the substance that Chromic Acid, and the other acids above is titrated. By resorting to this artifice it enilmerated; also Permanganate of Potassium, becomes possible, therefore, to titrate stannous Ferric Salts and Iodine. oxide with any reagent with which ferrous I'he essential points of the process are either oxide can be titrated. that a solution of' stannous chloride is con- The affinity of chloride of tin for active ve'ted( into stannic chloride, by means of dissolved oxygen is so strong that, in the case oxildizing solutions of known strength, or that of a mixture of iodine, chromic acid and disan excess of a standard solution of stannous solved oxygen, the tin salt will unite with the 156 PROTOCHLORIDE OF TIN. latter before proceeding to reduce the chromic reduce the washed oxide with a standard soluacid and iodine. The dissolved oxygen be- tion of chloride of tin and titrate the excess of comes active only in presence of the stannous the latter with a standard solution of bichrosalt and chromic acid. When the tin salt is mate. (Streng.) replaced by hyposulphite of sodium, the oxy- 2. Chloride of Tin aygainst llMercury Salts. gen remains inactive. In case the stannous Compare C, above. To estimate stannonms oxsalt to be oxidized by chromic acid is mixed i(le when mixed with stannic oxide, determine with so much iodhvdric acid that the chromic the total amount of' tin in one portion of' the acid is completely decomposed, there will be mixture; then dissolve another portion in a direct titration of the stannous salt with chlorhydric acid, taking care to exclude the iodine, and the dissolved oxygen will have no air, and drop the solution into a large excess active action. But if the proportion of iodhy- of mercuric chloride kept constantly stirred dric acid is so small that a certain quantity of and somewhat warm. Allow the precipitated chromic acid can exist in its presence, some diChloride of Mercury to stand for a long time, of the dissolved oxygen will become active, then collect and weigh it in the usual way. since this activity is induced by the contact of One molecule of HgC12 corresponds to one of chromic acid and the stannous salt. It ap- SnC12 (H. Rose). pears, however, that the presence even of 3. For the use of stannous chloride as an small quantities of iodhydric acid tends to absorbent of free chlorine in Mitscherlich's diminish the quantity of oxygen which be- method of organic analysis, see Chloroplaticomnes active, while the amount of the latter nate of Potassium, power of decomposing orincreases as the proportion of chromic acid or ganic substances. of the tin salt is increased, or as the water For use as a reagent, stannous chloride may contains more oxygen in solution. Similar be prepared as follows:- -Fuse a quantity of remarks apply to the oxidation of stannous metallic tin in a small porcelain dish, Iremove chloride by permanganate of potassium in the dish from the fire and rub the melted presence of chlorhydric acid. When chlorous metal with a pestle until it becomes solid. or hypochloric acid is treated with the tin salt Transfer the metal thus powdered to a flask, the dissolved oxygen becomes active, no mat- throw upon it a strip of platinul foil or the ter whether iodhydric acid be present or not. cover of a platinum crucible, pour in a quanBut as regards peroxide of hydrogen it ap- tity of strong chlorhydric acid and boil the pears that the presence of iodhydric acid pre- mixture under a hood until the evolution of vents the activity of the dissolved oxygen. hydrogen from the surface of the platinum is (Lenssen and Lemwenthal, loc. cit., pp. 193- observed to have become feeble. Take care 215). always to have the tin in excess. The presA. For the estimation of Chromic Acid see ence of the platinum greatly facilitatesthe sounder that head. lution of the tin. Since chloride of tin must B. For the estimation of Tin see biChro- always contain some free acid to be fit for use, mate of Potassium. it is best not to push the boiling until the evoC. To estimate 3Iercury, dissolve the sub- lution of hydrogen has entirely ceased. stance to be analyzed in chlorhydric acid, pour In order to prevent the solution from absorbinto it from a burette a sl;ght excess of a ing oxygen from the air, it should be kept in a standard solution of protoChloride of Tin, well stoppered bottle containing a nunlber of heat the mixture unitil the mercury is reduced small pieces of' metallic tin. This remark apto the metallic state, and the metal has col- plies however, only to:olutions which have lected into a ball. Decant the clear liquid not been standardized. To keep a standard into a flask, wash the metallic mercury by solution Fresenius recommenids the following decantation with water which has been boiled arrangement:- Place the bottle which is to to expel air, and estimate the excess of proto- contain the tin solution at the very corner of a chloride of tin by means of one-tenth normal table and fit to it a caoutchouc stopper with solution of the bichromate, as explained under two holes. To one hole of the stopper fit a Chromic Acid. The presence of nitric acid is syphon, made by bending a glass tube at two inadmissible. To analyze mercurous nitrate in right angles. The shorter arm of this syphon this way it must be first precipitated as Chlo- is straight and reaches almnost to the bottom of ride by means of chlorhydric acid, and washed the bottle while the outer arm reaches below before adding the solution of tin. Mercuric the table to a point considerably lower than nitrate can be decomposed by boiling with the bottom of the bottle, it is curved upwards chlorhydric acid (Mohr, Titrirmethode, 1855, at the end and closed with a piece of rubber 1. 274). tubing compressed by a spring clip. By means D. To estimate Iron see Ferric Salts. of another tube bent at two right angles and E. To estimate Copper see under Copper fitted to the second hole in the stopper the Salts, reduction of by iodide of potassium. bottle is connected with another smaller F. To estimate Lead, 3Iisnganese, Cobalt or though still tolerably large bottle, and this in Nickel, precipitate the metal as a peroxide turn with a couple of U tubes. The U tubes by means of a solution of bleaching powder, as well as the bottom of the bottle are filled BICHLORIDE OF TIN. 157 with fragments of pumice stone saturated with the non-volatile chlorides in the bulb tube, proa strongly alkaline solution of pyrogallic acid. vided the heat to which the sulphide is subWhen everything is ready, put a piece of glass jected has not been too strong. But if the tubing in the rubber connector at the outer heat has been too high, a very small quantity end of the syphon, open the clip and suck at of chloride of zinc will go forward with the the tube until the syphon is full of the stan- volatile chlorides. (H. Rose). nous chloride. Then close the clip and re- MIethod B. Compare protoChloride of Copmove the sucking tube. At the outer extrem- per (fixity of). In the analysis of' difficultly ity of the last U tube there is a cork carrying combustible organic substances, such as chloroa tube of rather fine bore so that the outer air form, which cannot be completely burnt in can communicate freely with the interior of oxygen gas, by Warren's method, oxide of the apparatus; but as the pyrogallic solution zinc is a good material to complete the coinabsorbs oxygen greedily, the vessels soon come bustion and absorb the chlorine. Oxide of to contain nothing but nitrogen. - To fill copper cannot be used in this case, since at a pipette or Mohr's burette with the solution, the high temperatures employed some dichloopen the clip so that a few drops of the solu- ride of copper would be fiormed, which being tion may run to waste, then insert the point of insoluble in dilute acids would interfere with the pipette in the rubber tube and open the the determination of the chlorine. - The clip. Since the outer leg of the syphon apparatus required is described under Chloride reaches far below the bottom of the bottle the of Copper, and the details of the method are liquid will flow into the pipette without ally similar to those there indicated except that difficulty. In case any of' the liquid is to be there is no oxide of copper used, and that the transferred to a beaker, a n-shaped tube may be whole of the asbestos in the tube-both the inserted in the rubber connector. In a bottle anterior and posterior columns, is mixed with thus protected the tin solution may be pre- oxide of zinc. The asbestos and oxide of served unchanged, for any reasonable length zinc are simply rubbed together in a mortar, of time. It is well to prepare the pyrogallate and then packed into the tube. About 3 of potassium in the vessels themselves some grms. of the oxide will be enough for the artine befobre the apparatus is put together, by bestos of the posterior column and 1 grm. for mixing concentrated potash lye with a solution that of the anterior column. At the close of of pyrogallic acid. the combustion all but a trace of the chlorine As a substitute for the foregoing arrange- will be found combined with the zinc of the ment, Mohr (Zeitsch. analyt. Chen., 1869, 8. posterior column. The air bath may be kept 113) simply pours a quantity of petroleum at 1600, or it may be dispensed with altogether. into the bottle which contains the chloride of The process yields excellent results (Warren, tilln, so that a layer of petroleum about 1 c. m. Proc. American Acad., 1866, 7. pp. 87, 89). thick shall float upon the surface of the liquid. Chlorimetry. The bottle stands at the corner of the table as A term applied to the valuation of bleaching before and is in like imanner provided with an powder and analogous compounds -the soupturned syphon tube for filling the burette, called " chlorides of' lime, potash and soda, but at the top of the bottle there is now etc.," which are mixtures of the hypochlorites, needed nothing more than a perforated cork chlorides and hydrates of the respective metals. carrying a small tube for the admission of air The bleaching or disinfecting- value of these when the outlet tube is put in action. substances depends upon the amount of chlorine For the methods of' standardizing a solution of set free when they are treated with an acid, stannous chloride see biChromate of Potassium, thus:Iodine, and the other substances against which CaO, C120; CaCd2 + 2H2SO4 = 2CaS04 + 2H20 + 4C1, it is used. and this chlorine may be readily estimated by biChloride of Tin, a variety of methods. See, for example, ArP1rinciple. Volatility. senious Acid (oxidation by chlorine); Chlorine Applications. Separation of Sn from Co, (oxidizing power of) and power of expelling Ni, Pb, Cu, IpI Au, Pt. iodine from iodide of potassium, and Ferro1Methods. b-e ler- and quinquiChloride of cyanide of Potassium; older methods of chlorAntimony. imetry are described under diChloride of MerChloride of Zinc. cury and Indigo. TPrinciple. Fixity when not too strongly Chlorine is commonly determined as Chloheated. ride of Silver, or as Chlorine, by some one Applications. Separation of Zn from S, As, of the processes depending upon its oxidizing Sb, Sn and Hg (Method A). Estimation of power to be described immediately. [See Chlorine in organic compounds (Method B). the finding list in Appendix.] Method A. When a mixture containing sul- Principle. Oxidizing power of. phide of zinc is decomposed by chlorine, in IApplications. Valuation of bleaching powthe mlannler described under Chloride of Sul- der. Estimation of chlorine, hypoehlorous phur or Chloride of Antimony, the whole of acid, sulphurous acid and hyposulphurous acid. the chloride of zinc will remain behind with Separation of Mn from K, Na, Ba, Sr, Ca, 168 CHLORINE. Mg, Al, Zn, Fe and Ni (see No. 7); of Pb 0.7831 grm. of the sulphate corresponds to from K, Na, Ba, Sr, Ca, Mg, Ni, Zn and Cu 0.1 grm. of chlorine, for (see No. 7); of Co firom Ni, etc. Analysis of 2Fe, So4 + 1HSO1 + 2C1= Fe203, 3SO 2+-HC1, many high oxides, acids and oxygenated corn- and pounds, w'hich evolve chlorine when heated Wt. of 2 Atoms Wt. of 2molecs. with strong chlorhydric acid (see No. 4). of C1 71 (FeSO4+7Aq)556:: 0.1: (= 0.7831). Valuation of' binoxide of manganese and other To avoid calculations, the operator may weigh high oxygen compounds. out 3.1324 grms. (- 0.7831 X 4) of the sulphate M3ethods. and dissolve it, with addition ot a few drops of 1. For methods (lepelndilngr upon the action dilute sulphuric acid, to the volume of 200 c. c. of chlorine upon Antirlon, Arselic, (liChlo- 50 c. c. of this solution (corresponding to 0.1 ride of Mercury, sesquiOxide of lChiromlliulm, grin. of chlorine) may then be taken out with and Indligo, see these several substances.' a pipette and diluted with 150 to 200 c. c. of 2. Action of chlorine upen ferrous salts. water, and a sufficient quantity of' chlorhydric This principle, first suggested by Dalton, was aci( for the titration gere it not for the reduced to practice by G;raRham11, and intro- inconvenience of weighing out a definite quanduced into Germany by Otto. It is often tity of iron wire, it would be well to start with called Otto's process by German writers, in 0.6308 grin. of pure metallic iron, —or, on the spite of repeated explanations by this chemist, assumption that fine lire contains 99.7 per that the process was not invented by himnself. cent of pure iron, take 0.6327 grin, of piano A. Provide a small, tolerably long-necked wire,-and to dissolve it with tile precautions flask, to which has been fitted a two holed above enjoined. The solution diluted to 200 caoutchouc stopper, carrying a couple of short c. c. would correspond to 0.4 grm. of chlorine, glass tubes, each bent at a right angle; weigh like the solution of the sulphate. - This out about 0.15 grin. of clean, fine iron vi'e nmethod gives very satisfactory results. Since (piano wire), and place it in the flask, to- it requires no standard solutions, it is particgether with a quantity of pure chlorhlydric ularly well adapted for occasional examinations aci. Insert the stopper, clap the flask ill of bleaching lpowder, and to serve as a control an inclined position, and pass a slow currenlt for other processes of chlorirnetry. As a proof washed carbonic acid through the flask. cess for every (ay use, however, it has far less Heat the acid until all the iron has dissolved, significlnce than was forrlllly the case, keep tip the current of carbonic acid until te Instead of the foregoing process, the flask has become cold, then dilute tilhe iron following mo(lifimcation may be used. \Weigh solution to the volume of' 200 cc., and pour out about 0.3 grm. of piano wire, c lissolve in upon it, from a 50 c. c. burette, the fi1ehly chlorhydric acid, with the precautions above shaken solution of bleaching powder until the given, dilute the highly acid solution to 200 or whole of the ferrous salt ihas been convertenl 300 c. c., and slowly add to the liqui-d, firom a into a ferric salt. To determinie tile point burette, 50 c.c. of the turbid solution of bleachwhen the oxidation is comptlleted, place a, nun- llg powder, while constantly stirring the iron ber of drops of a solution of' ferricyanide of solution. Lastly, determine how much iron potassium upon a white porcelain plate, and, remains unoxidized by means of a standard as the operation draws to its close, take up solution of biCllromat.e of Potassium, or of upon a thin glass rod a little of the liquid Pellnanganate of Potassiuln By slbtratillg under exalllinatlon, add it to one of the drops the eight of iror thus found frori the weight of the tbrricyanide, and observe whether a of iron taken the weight of iron equivalent to blue precipitate is produced. Repeat this tile chlorine in the bleaching powder used will test after each fresh addition of two drops of be obtained. The prcess yielos accurate the bleaching powder solution until the last resUlts, particularly wahen applied to the valuaadd(ition of liquid fails to yield any blue pre- tron of' chlorine water. Hypochlolites must cipitate. Then note how many c. c. of the be added very slowly to the iron solution, since bleaching powder solution have been expended, they give off' chlorine vely easily on coluilg iii and calculate the chlorine by the proportion contalct with the acid liquor, A that there is Wt. of 2 atoms At.wt.of Wt ofFe danger of losing some of the gas. Accordingr of Fes6 C1 3:.5: taken: to Mohr (Titririellhode, 1856, 2. 132), an acid The turbid solution of bleaching powder solution of a ferrous salt can never absorb required should be prepared in the manner instantly all the chlorine which is brougllt n described un(ler Arsenious Acid. - In- contact with it. The odor of' chlorinre (all be stead of ferrous chloiide the inventor of the perceived, moreover, in liquors which} s"till Cunprocess enmployetd pure crystallize(d ferrous sul- tain ferrous oxide. A certain anlount of time phate, obtained by dropping a hot, fiesh solu- seems to be required for the ferlrolus salt to thbtion of clean iron in dilute sulphuric acid into sor5b the oxygen or chlorine necessary to contwice its volume of' alcohol. The crystalline vert it to a ferric salt. - In examinining precipitate thus obtained was washed with chlorine water, the latter should be left in alcohol, dried between sheets of' filter paper, contact with the ferrous salt in a stoptpered and kept for use in tightly corked bottles. bottle fbr a short time, before proceeding with CHLORINE. 159 the titration. In measuring out chlorine wa- As applied to the valuation of bleaching ter for analysis attach a tube, fitted with frag- powder this process has already been described inents of moist, caustic potash to the top of under arsenious acid. it may be employed the pipette. also for the valuation of binOxide of' MlangaC. The bleaching powder solution is mixed nese, Chromate of Potassium, Chlorate of with an excess of a solution of ferrous chlo- Potassium and many other oxygen conipounds ride of known strength and the amount of fer- capable of evolving chlorine when heated with ric chloride formed is determined by means of chlorhvdric acid. But in these cases special protochloride of tin (see Ferric Salts), or by precautions must be taken in generating and hyposulphite of sodium (see Ferric Salts). collecting the chlorine, [Compare Principle IT, Each equivalent of FeCl3 corresponds to one below]. - A simple form of apparatus for equivalent of Cl, for absorbing chlorine in arsenite of' sodium has Feel, + cl= Fecl3. been described by Mohr (litrirmnethode. 1855, D. The bleaching powder solution isheated 1. 313). It may be prepared as follows:with a mixture of alkali and freshly lprecipita- Fit a two holed cork or caoutchouc stopper to ted ferrous oxide and the chlorine estimated an ordinary flask of about one litre capacity. as Chloride of Silver, precisely as in the anal- In one hole of' the stopper place a small narysis of Chlorates (by estimating the chlorine in row funnel full of rather small fragments of the residual chloride). The process of' course glass or porcelain and in the other hole insert a gives only the total chlorine in the substance tolerably wide glass tube, which shall reach alanalyzed (Stelling, Zeitsch. analyt. Chem., most to the bottom of the flask and also pro1867, 6. 33). ject three or four inches above the stopper. E. The bleaching powder solution is made This tube though straight in the main should to act upon a solution of' ferrous chloride and be bent slightly at a point above the stopper, the amount of' ferric salt formed is estimated so as to incline somewhat to one side and not by determining how much metallic copper the interfere with the funnel. Slip the ring of a solution will dissolve off from a weighed sheet spring clip over the projecting part of this or bar of that metal. See Ferric Salts (Runge). tube so that the clip may hang there ready for F. To estimate the value of binoxide of use. This large flask is to contain the solumanganese, Otto heated a weighed quantity of tion of arsenite of sodium and serve as the rethe powdered mineral with strong chlorhydric ceiver of the gaseous chlorine. To connect it acid in a flask provided with a proper delivery with the decomposing flask, bend another glass tube, led the chlorine evolved into the solution tube, of similar bore to the first, twice-at of a weighed quantity of ferrous sulphate and one acute and one obtuse angle. The little determined how much of the latter had been flask which is to serve to generate the chlorine converted to ferric sulphate by the chlorine. is closed with a perforated cork of the best Another old way of valuing the binoxide quality. Through the hole of this cork, push was to heat it with chlorhydric acid as above, that portion of' the bent tube which is below and absorb the chlorine in milk of lime. The the obtuse angle; and by means of a rubber amount of chlorine in the product was then connector attach the other end of the bent determined by some one of the ordinary meth- tube,- that under the acute angle - to the ods of chlorilnetry. straight tube whichl projects fiom the absorp3. Action of chlorine uponz ferrocyanide of tion flask. Take care to arrange the rubber potassium. Mix the solution of bleaching pow- connector so that it can be closed by means of der or chlorine water with an excess of a the spring clip when necessary. It is well to stan(lar(l solution of Ferrocyanide of Potas- grind off obliquely the lower end of the bent siuim, acidulate the mixture strongly with tube, which falls within the decomposing flask, chlorhydric acid and determine the excess of to facilitate the dropping of liquid fiom it. the telrrocyanide by means of a standard solu- When everything is ready a measured quantion of biChromate of Potassium. The opera- tity of a standard solution of' arsenite of' sotion is finished when a drop of liquid touched dium (see below) is placed in the large absorpto a (dro)p of' highly dilute ferric chloride, upon tion flask together with a considerable excess a white plate, no longer occasions any blue or of pure carbonate of sodium. The latter is green coloration (E. Davy. Phil. May., (4), poured through the chips of' glass in the fun21. 214). According to Davy, bielroinate of nel so that they may be left moistened with it. pot;,ssiumn is to be preferred( to permanganate The oxide to be examined is place(l in the of potassium for estimating the excess of ft.rro- small flask together with a quantity of' concencyanide, but Fresenius (Zeitsch. anal/yt. Chlem., trated chlorhydric acid, and the mixture is 1863, 2. 93) urges that the titration may be boiled until the whole of the chlorine has made more conveniently Nwith the permlanga- been set free and driven over into the absorpnate. - For Gav-Lussac's method of' using tionflask. 1i is safe to conclude that all the ferrocyanide of' potassium in chlorilmetry see chlorine has gone over when the tube which Annales Chim. et Phys., 60. 225. projects from the absorption flask feels dis4. Action of chlorine upon arsenious acid tinctly hot to the hand, and the peculiar noise and arsenites. Compare Arsenious Acid. of steam condensing in the liquid of the ab 160 CHLORINE. sorption flask is heard. During the earlier quantity of iodine which has been set free by part of the decomposition most of' the acid va- the chlorine, while in the process now under por generated in the decomposing flask will consideration it is not the amount of arsenious condense in the sloping tube which connects it acid which has been oxidized that is deterwith the absorption flask and the liquid thus mined, but the portion which has been left unformed will flow back into the decomposing acted upon. This point has special signififlask. But as soon as the sloping tube has be- cance according to Fresenius, in cases where come hot some chlorhydric acid will pass over the amount of' chlorine turns out to be less into the large flask, and by acting upon the than was expected and where there is consecarbonate of sodium will occasion a strong quently an undue excess of undecomposed areffervescence. rTo stop the process, remove the senite to be estimated. The errors of' observalamp from the decomposing flask and at the tion and those due to slight changes in the same instant close the rubber connector with composition of the standard arsenite solution the spring clip. Without opening the clip, go to impair the accuracy of' the determination disconnect the bent tube from the absorption of the chlorine. flask, shake the latter and allow it to cool. 5. Action of chlorine upon stannous chloride. Wash the glass chips with water as well as the Mix the chlorine water, or less conveniently lower part of tile tube through which the the solution of bleaching powder, with an exchlorine was admitted to the flask. Pour a cess of a standard solution of protochloride of little starch paste into the flask and with a tin, and determine the excess of' the latter by standard solution of Iodine determine how means of a standard solution of biChromlate much arsenious acid remains undecomposed. of' Potassium. For the objections to the use of' No odor of chlorine should be perceived when protochloride of tin, see biChromate of Potasthe flask is opened. It is to be observed that sium. According to Mohr it is hardly possithe straight tube in the absorption flask should ble to avoid the loss of some chlorine when a dip slightly beneath the surface of the solution solution of bleaching powder is added to the of' arsenite of sodium. With regard to the acid solution of' chloride of tin. quantities of materials to be used, it may be 6. Action of chlorine upon sulphites and hysaid that for 0.2 to 0.5 grin. of bichromzate of posullphites. potassium Mohr places fiom 40 to 100 c. c. of A. To estimra!e sulphurous or hy7losulphutrarsenite of sodium solution in the absorption ous acids. Saturate the solution of' the subflask. For the preparation of the arsenical so- stance to be examined with chlorine gas and lution see Arsenious Acid. - See Arseni- warm the mixture. Precipitate and weigh the ous Acid also for the application of the pro- sulphuric acid, as Sulphate of' Barium. The cess to the estimation of' low oxides such as process is specially applicable for the analysis As20 and FeO which are capable of being oxi- of sulphites which are wholly free fi'oln any dized by nascent chlorine. contamination of sulphuric acid. At first sight it would seem to be easy to ap- B. T'o estimate chlorine in aqueous solutions. ply the process to the estimation of chlorine in Mix the liquid under examination, which ordinary chlorides by heating the latter in the must be free from sulphuric acid, with a decomposing flask with a high oxide (like slight excess of hyposulphite of sodium in a MnO1 or K20, 2CrO.) and sulphuric acid, but stoppered bottle, and leave the bottle ibr a the experiments of Mohr (Titriarmethode, 1855, short time in a warml place until the odlor of 1. 317) go to show that the whole of the chlo- chlorine can no longer be detected. Then rine cannot be expelled from the chlorides in heat the liquid to boiling with an excess of' this way by a single distillation. Possibly pure chlorhydric acid in order to destroy the last permianganate of' potassium might do better portions of hyposulphite of so(lium, filter ofi' than the oxydizing agents above mentioned. the sulphur and determine sulphuric acil in A still less satisfactory result was obtained on the filtrate as Sulphate of' Barium. Each distilling in the dry way a mixture of chloride equivalent of sulphuric acid found will correof sodium, binoxide of' manganese and bisul- spond to 2 equivalents of chlorine. About 0.5 phate of potassium. grm. of hyposulphite of' sodium will be enough The method now in question has suffered to take for 30 grins. of' chlorine water (Wicke, somewhat froln a prejudice in fkvor of' the Annalern Chem. untd Pharm., 99. 99). somewhat analogous method of' Bunsen (see C. To estimate the total chllorine in a mixture below, Principle II) in which iodide of potas- of free chlorine and chlorhgydric acid ori a chlosiumn is used to absorb the chlorine. It has, ride, mnix a weighed quantity of' the liquid however, the distinct merit of requiring no with an excess of sulphurous acid, acidity the large quantity of expensive materials and is to mixture with nitric acid and throw down the be colmmended in cases where the amount of whole of the chlorine as Chloride of Silver. chlorine to be estimated is comparatively In another portion of' tile original liquid estilarge. Fresenius has urged also that the in- mate the fi'ee chlorine by means of iodide of direct character of' the process must not be potassium or ill some other appropriate way. lost sight of. In Bunsen's process, with the D. For estimatirng the value of bleaching iodide of potassium, we determine directly the powder, Fordos & Gelis proposed to substi CHLORINE. 161 tute a standard solution of hyposulphite of is evolved into a mixture of sulphurous acid sodium for the Arsenious Acid enlployed by and chloride of barium, collect and weigh the Gay-Lussac. The standard solution was pre- Sulphate of Barium formed, and from its pared by dissolving 2.77 grms. of the hypo- amount'calculate that of the binoxide. The sulphite in water and diluting to the volume of details of the process are as follows: —Prepare 1 litre. Such a solution neutralizes its own a not too concentrated aqueous solution of volume of chlorine and is equivalent to the chloride of barium, acidulate it with chlorhyarsenical solution of Gay-Lussac. For an dric acid which has been so much diluted that analysis, 10 c. c. of the standard solution of it will not throw down any of ihe chloride of hyposulphite were placed in a beaker, diluted barium, and lead sulphurous acid into the liqwith 100 c. c, of water, acidulated, and uid until the latter smells strongly of' the gas. colored blue with a few drops of a solution of Put the liquid aside in a tightly stoppered botindigo. The solution of bleaching powder tie until it has deposited any precipitate due was then poured into the beaker from a bu- to the presence of a little sulphuric acid. (On rette, in the manner described under Arseni- the other hand fit to a flask, by means of a ous Acid. The blue color is but slowlyv de- perforated cork, a delivery tube bent at two stroved so that the operator has plenty of time right angles. Place in the flask a weighed to observe the change. The process has the, quantity of the binoxide of' manganese, cover great disadvantage that a fresh supply of the it with strong chlorhydric acid, cork the flask standard solution must be prepared for each and support it in such position that the long, set of experiments. The reason for diluting outer limb of the delivery tube shall reach the standard solution of hyposulphite before into another flask charged with the mixture of adding the bleaching powder is to avoid the chloride of barium and sulphurous acid. This precipitation of sulphur. It was urged as an second flask should be partially closed by advantage of the process that the hyposulplhite means of a loosely fitting cork. Heat the mixwould be acted upon by any chlorite in the ture of manganese and aci(l moderatelIy, until powder while arsenious acid would not be oxi- no more chlorine is given off, or until the oxdized thereby. ide of manganese has all dissolved, and the D. A gravimetric method of estimating the brown color of' the liquid in the flask has disvalue of' bleaching powder based upon the oxi- appeared, then boil the liquid for a short time dation of hyposulphite of sodiumn by the clllo- to drive the last traces of' chlorine out of the rine of the powder has been proposed by flask, taking care that it does not boil over. Duflos, and afterwards by Ncellner (Annalen Finally tip the flask so that the outer limb of Chem. und Pharmn., 95. 113). The oxidation the delivery tube shall be lifted out of the was supposed to be effected in accordance chloride of barium solution, remove the lanmp, with the following equation:- wash the end of the delivery tube and cork Na2O, S202 51120 + sC1 = 2H2S04 + 2haCl + 6HC1. the absorption flask. The liquid in the bottle According to Nellner, 1 grm. of the bleach- must still smell strongly of sulphurous acid at ing powder is ground up with 2 grins. of hypo- the close of' the experiment. - To collect sulphite of' sodium in a mortar, the mixture is the sulphate of' barium the mixture may either washed into a flask and the solution warmed be left to settle and then be filtered, out of upon a steam bath. The excess of' the hypo- contact with the air, or the contents of the sulphite is decomposed with chlorhy-dric acid absorption flask may be boiled to expel the and the liquid warmed until it has become excess of' sulplhurous acid, as soon as the cllloclear, and the sulphur has collected in drops. rine has all been absorbed. It is a defect of The liquid is then filtered, and the sulphuric this method that access of air can easily conacid determined as Sulphate of Barium in the vert some of' the sulphurous acid into sulusual way. Manifest objections to the pro- phuric, but on the other hand it is applicable cess will be found in the liability of' hyposul- In cases where the manganese is contaminated phite of' sodium to contain solme sulphuric with oxide of iron, carbonates of the alkaacid, and of chlorhlydric acid to contain a little. line earths, etc. An error in weighing the chlorine. The operations of washing and sulphate of' barium, moreover, is diminished as weighing the sulphate of barium are, mnore- regards the binoxide. When careftlly conover, tedious, and not wholly free from difli- ducted, the process yields tolerable results. culty. The accuracy of' the method has, (Duflos; Ebelmnen.) moreover, been called in question by Knop 7. Action of' chlorine tupon salts of man(Pharim. Centralblaltt, 1855, p. 656), and dis- ganese, cobalt and lead. [Compare Bromine.] proved by Fresenius. The latter found that A. To separate manga.nese firom the alkali the results of the process differed considerably, metals, saturate the chlorhydric acid solution accordingly as more or less hyposulphite of of the substance with chlorine gas, and presodium was used. cipitate Hydrate of Manganese by means of E. To estimate the value of binoxide of carbonate of' barium, or less completely by manzzanese and the lice, treat a weighed quan- ammonia water. The process may be emtity of the finely powdered dry mineral with ployed also, in certain cases, for separating chlorhydric acid, lead the chlorine gas which manganese fiom the alkaline earths, though it 11 162 CHLORINE. is inferior to the method in which manganese the solution almost to boiling in a beaker, and is thrown down as binoxiclde, see below, be- stir into it stron~g chlorine waiter [or better, cause portions of the alkaline earths are liable Broinine] until the nmixture smnells strongly of to fall in combination with the hydrate of man- chlorine after thoronobh sti1rring. In case the ganese.. - For separating mianganese an(l chlorine water contains much hlIorhydric acid cobalt from nickel, place the elhlorhydrlic acid neutralize the latter with a little carbonate of solution in a capacious flask and (dilute with sodium. The operation is known to be comwater, in such proportion that there shall be plete when the liquid, after the deposition of about 1 litre of solution for 2 grums. of the the black or (lark brown precipitate, remains mixed oxides. Saturate the liquid with chlo- colored red, fiom the presence of permanganic rine gas, and see to it that the upper part of acid. But this coloration cannot he obtained the flask above the liquid is full of chlorine. unless the liquid has been nmade almost neutral Add an excess of elutriated carbonate of cal- with carbonate of' sodium before add(in, the cium, leave the mixture in the cold for 18 or acetate. To destroy the permnanganate add a 24 hours, shaking it as often as may be con- very sm all quantity of' alcohol to the still venient, andl finally filter the mixture. The warm solution after the precipitate has been whole of the nickel will pass into the filter, allowed to settle for the most part. -Wash the together with some traces of cobalt, while the precipitated oxide thoroughly with hot water. hydrates of manganese and cobalt, together It is of varyig' composition as regards the with the excess of carbonate of calcium, will proportion of oxygen, and is liable to retain a be left, upon the filter (H. Rose, Pogy. An- certain quintity oi soda, so that after having nalenl, 71. 545, and 110. 412). Instead of once been ifnited and reduced to manganite chlorine, D. Sinith uses a dilute solution of' of manganese it may, on further ignition, inbleaching powder, which has been so com- creas.; in weigllt througli absorption of' oxygeni pletely decomposed with suliphuric acid that to' form ianc-anate of sodium. - In case no particle of hypochlorite remains in it. If the solution to be analyzed contains any large there were any hypochlorite present, some proportion of salts of ammonium. these comnickel would go down with the oxides of man- pounds lmust be destroyed( by boiling witlh ganese and cobalt. Bromine is a still better carbonate of sodium before proceeding with oxi(lizin0g aoent, as Henry 1has shown. the oxidation, for the manganese cannot all To separate manganese fiom iron and nickel, be tlirown down by clilorine in presence of and fronl the metals of the alkaline earths, ammnonium salts. For this reason, amnnioni;a Pass a current of chlorine through a dilute water cannot be used instead of carbonate of acetic aci(l solution of the substance,, or better, sodium for neutralizing the original acid so-, through a mi.ixture of the chlorides of the lution. metals and acetate of sodiulm. If the sub- B. To separate lead fiom alkalies, alkaline stance is in, the form of a chlorhydric acid earths, magnesium, zinc and nickel, dissolve solution mix. this solution with enough acetate the mixture in acetic acid, heat the liquid to of sodium to decompose the chlorides and bind 50~ or 60~, and lead chlorine gas,into the the free chlorbydric acid. The presence of liquidcl as long as any binOxide of Lead conacetic acid does not prevent the precipitation tinues to fall. The precip tation is soon finof the binOxide of Manlganese. Since cobalt ished. In case the original solution contains would be partially precipitated in this, way as free chlorhydric acld, nearly neutralize it witlh well as manganese, it must be excluded firom carbonate of sodium and add acetate of sothe solution (Schiel, Ameerican Journ. Sci.,. dium to decomnpose the chlorides. The pro1853, 15. 275; Compare Rivot, Beudant & cess is not applicable to the separation of leadt Daguin. Comeptes Renduss, 1853, p. 835). fiom iron, cobalt and manganese. (Rivot, According to Firesenius the solution should Benudant & Daguin, Jonurn. pratkt. Chelr., 61. be heated to 50~ or 600 duri.ng the passage of 136.) Accor(ling to I-I. Rose, though chlorine, the chlorine. Instead of chlorine gas, a solui- when made to act upon chloride of lead and tion of hypochloroiis acid or of hypochlorite of sulphate of lead suspend(e(l in water, can eonsodium may be used, but in case the latter is vert them into the binoxide, there' will always employed take special caire to: keep the liquid be traces of' chloride of' lead, and in presence acid, with acetic acid. The process is held in of sulphuric acid, a comparatively large progood esteem, but Fresenius finds that the bin- portion of sulphate of lead in tlie binoxide oxide of manganese precipitated in this way obtained as above. The binoxide, therefore, retains a certain anmount of alkali.. l-le ree- cannot be weighed as such, but must be conoinmends that it be redissolved in chlorhlvdric- vertedl into su.lirhide of lead. - The binacid and thrown down, as Carbonate of Man- oxide of lead, moreover, always carlies down ganese. larger or slnaller quantities of the other oxides H. Rose directs that the solution to be oxi- fi'oll which it is to be separated, notably oxide dized should be concentrated, or at all events of zinc, and must consequently be redlissolved not too dilute. In case it is strongly acid neutra- alnd again treated, to eflect a complete seplize it almost completely with carbonate of' so- aration. dlintml before adding the acetate of' sodium. teat C. Cobalt can be precipitated in the same CHLORINE. 163 way as mancanese from hot solutions slightly expense of the copper; unless, indeed, the acidulated with acetic acid. It is well to add amount of' ferric oxide be determined in a fioln timle to tilne a few drops of carbonate of separate portion of the mineral, and subtracted sodiuill and chlorine water, until the solution friom the first result. To this end weigh out smells of chlorine. For the treatment of the as much of' the sample as was taken for the precipitate see Hydrate of Cobalt. first trial, boil it in an open flask with an ex8. Action of chlorbie wupon coppjer. Chlo- cess of ehlorlhydric aci(l until no more chlorine rine can be estimated indirectly in aqueous is evolved, then place a weighed strip of copsolutions by placing in the latter a weighed per in the flask, close the latter with a quantity of some mletal like copper, which perforated cork, and proceed as in the first unites with chlorine to torrn a soluble chlorile, experiment. This process has the merit that notingr the loss of weight of the metal, and it mnay be applied without trouble to the valucalculating therefrom the amount of' chlorine. ation of manganese which is contaminated This principle has been applied1 to the valua- with carbonates of the alkaline earths. tion of bleaching powder (Runge) and of 9. Action of chlorine up~on organic coloring binoxide of manganese (Fickentscher,.Journ. matters. See the various coloring matters. prakc. Chenm., 17. 173). The process, as re- The old mIethod of chlorilnetry depending,ards binoxide of' manganese, is as follows: — upon the decoloration of Indigo will be deWeioh out 3 or 4 grins. of finely powdered, scribed under that head. A method of testinog dry binoxide of manganese, and place it in a the value of indigo, (levised by Schlumberger, flask to which has been fitted a perforated is as follows: - Powder the several sanmples of cork carrying a narrow glass tube. Pour some indigo which are to be compared, as described water upon the powder, and place in the flask under Indigo, weigrh out precisely 1 grm. of a strip of brightly polished, not too thin, sheet each sample and 1 grin. of pure, indigotine, copper., which has been accurately weighed. obtained by collecting the sublimate of indigo It should weigh about 30 grins. Then pour vats, andl washing it first with acidulated wainto the flask as much strong chlorhydrie acid ter and then with pure water; dissolve the as may be necessary to dissolve the manganese, samples in fuming sulphluricf acid, as (lescribed and put the cork into the neck of the flask. un(ler biChromate of Potassium (action upon Let the mixture standl for some time in the coloring matters), and. dilute the solution to cold, then heat it until the manganese has the volumle of 1 litre. By means of a marked (lissolved, and finally [boil the liquid fbr some pipette transfhr 50 c. c. of the solution to a time. At the moment of removing the lamp glass cylinder, and pour into the blue liquid, close the tube in the cork with a pellet of wax. fromn a graduated p-ipette, successive 2.5 c. c. Durine this process of (lissolving the manga- portions of a soluti(n of bleaching powder nese no trace of' (hlorine should be evolved. Iarking 1~ B, until the blue color is totally deThis accildent lna oclcur -in case the mixture stroved. To determine the excess of chlorine is heated too quickly, or when very strong thus added, pour a quantity of' the indirgo chlorhydric acid is employed.cl After the flask solution in question into a burette, and pour it has become cold take out the strip of copper, thence into the liquid in the cylinder until a wash it thirwoughly with water, dry it and greenish tint pervades the liquid. It is well to weigh it. From the loss of weight which the verify the resuilts of the first trial by mneans of copper has undertgone, calculate the amount of a secoind experiment. The calcuelation is as real binoxide in the man-ganese examined. follows:- Suppose that 5 c. c. of the clilorine The dlichlorie oft coppeIt foriled dissolves in solution have decolorized 59 c. ('. of the soluI)art in the excess of chlorhydric acild, and is, tion of' indigo, viz.. the 50 c. c. first taken and in part, (lep)osited as a white poN(ler. In case 9 c. c. subsequently added from the burette. any of' it should adhlere filrnml to thie metallic On the other hand, let it be admitted that of coppier, it mlla be dissolved oil with (lilute the solution of pure indigotine, 46 c. c. corchlolhydriic acid, to be followred inmlediately responded to 5 c. c. of' the chlorine solution. by water. Or. better, the separation of the Then dicliloride maly be enltirely prevented when, Since 46 c. c. of indigotine solution - 59 c. c. of the instea(i of watel, a concentlratedil solutio(n of sample, these 59 c. c. will contain 0.046 grin. of indigocormnmon salt- is pliced in the flask with the thue whence the proportion 59: 0.046 = 1000: x (= the pure indigotine in 1 grm. of mlanganese, fbr ticlllorilec of' copper is soluble the sample). in chloride of sodiuhii. n - The nlethod gives The process was formerly esteermed, but is intolerably accurate results, and is use-ul some- convenient because of the instability of the times fobr technical purposes, though it suffiers solution of' bleaching powder. It is of' course firom the fact that a little inetallic copper will necessary to determine. the value of this soludissolve in chlorhvdric acid, even lwhen air is tion against pure indigotine in each series of' m(arefully excluded. It is not applicable for experiments. It is impossible, moreover, to the analysis of binoxide of manganese which avoid losing some chlorine at the'moment contains any considerable amount of ferric when the bleaching powder solution comes in oxide, since the ferric chloride at first fornmed contact witl the acid liquid. A better method would be reduced t.o ferrous chloride at the is described underl biChromate of' Potassium. 164 CHLORINE. (Schiitzcnberger's llcatie'res Colorantes, 1867, chlorhydric acid, the flask is then connected 2. 558.) with the remainder of the apparatus and its I' inciple II. Power of decomposing iodide contents heated - at last to boiling —until of potassiurn and other metallic iodides. the whole of the chlorine has been driven over Applicativons. Estimation of chlorine and into the iodide of potassiumll. Take care to of hypochlorous acid; of iodine and iodhydric shake the flask which contains the latter ocacid. Valuation of' bleaching powder. Sep- casionally. The empty chloride of calcium tube aration of chlorine, bromine and iodine from serves to condense a good part of the acid one another. Analysis of many oxides, acids vapors, and to return themn to the decomposand oxygenated compounds which evolve ing flask. Finally pour the iodide of potaschlorine when heated with strong chlorliydric slum solution into a beaker, together with the acid [Compare Arsenious Acid, Iodine, bi- rinsings of the vessels which contained it, and Chromate of Potassium, Permanganate of estimate the free Iodine by means of a standPotassium, binOxide of Manganese, and the ard solution of hyposulphite of sodium. - The various high Oxides]. process is exceedingly accurate, and is to be Mlethod A. Bring the chlorine, either in recommended in all cases where the quantity the gaseous form or in solution, into contact of chlorine to be estimated is but small. It is with an excess of a solution of one part of less convenient, however, when any consideraiodide of potassium in ten parts of water, and ble quantity of chlorine has to be set free. determine how much iodine has been set firee To estimate the value of bleaching powder by the chlorine, by means of a standard solu- by this process, pour 10 c. c. of the turbid tion of hyposulphite of sodium or sulphurous solution of bleaching powder, prepared as acid (see Iodine). Each atom of iodine found described under Arsenious Acid, p. 44, into a corresponds to one atom of chlorine. Chlorine beaker, add about 6 c. c. of a solution of Iodide water may be silmply allowed to flow from the of Potassiuln (1 part of the salt to 10 parts of pipette into an excess of' the iodide of potas- water), dilute the mixture with about 100 c. c. sium solution. If the latter be not present in of water, acidulate with chlorhydric acid and sufficient excess, a persistent black precipitate estimate the Iodine, which is set free, by means of iodine will be formed. Chlorine gas, on of hyposulphite of sodiunm or sulphurous acid. the other hand, as obtained by the action of Each equivalent of' iodine found represents an concentrated cblorhydric acid upon any high equivalent of chlorine. This method yields oxide (compare Arsenious Acid, oxidation of excellent results, but is less employed than the by nascent chlorine), must be set free in a processes for which only cheap materials are flask or retort, and carefully led into the solu- required (see Arsenious Acid and Chlorine, tion of' iodide of potassium in such manner above). (Bunsen.) that none of it shall be lost~ To this end Mlethod B. When chlorine water, or a soprovide a small flask, free froln any projecting lution of hypochlorite of sodium, is added to irl or lip, and by means of' a sufficiently wide the solution of a metallic iodide, the iodine caoutchouc tube connect it with an empty, expelled from combination with the metal, bulbed chloride of calcium tube of the same unites with chlorine to form pentachloride of diameter as the neck of' the flask. The caout- iodine. Hence, by employing a standard soluchouc connecter should be thoroughly boiled tion of chlorine and a proper indicator, to in dilute potash lye, and afterwards well show when the last particle of iodine has been washed with water to fiee it firom adhering combined with chlorine, the amount of' iodine sulphur. When everything is ready, clamp in any compound can readily be determined. the flask in an inclined position, so that any Golfier-Besseyre employed starch paste as the liquid condensing in the bulb of the empty indicator, but A. and F. D)upr6 (A nnalec chloride of calcium tube could run back into Chlem. und Pharmn., 94. 365) have improved the flask, and by means of narrow glass tubes upon that suggestion, and employ as the indiand short rubber connecters freed fiom sul- eator chloroftlorm, or bisulphide of' carbon, both phur, connect the outer end of the chloride of of' which substances are colored intensely viocalcium tube with a small flask containing let by free iodine, as well as by all compounds iodide of potassium, to which is attached a of iodine and chlorine which contain less than U-tube likewise charged with the iodide. Both 5 atoms of the latter to one of the former the vessels which contain iodide of potassiumi element. - There are two ways of proshould be placed in a dish of' cold water, and ceeding: -Thefirst way is as follows: Prepare the tube which delivers the chlorine gas should some highly dilute chlori-ne water and denot be allowed to reach qvuite to the surface of termine its strength by mnlcas of a solution of the solution of iodide in the receiving flask. iodide of potassium, as explained above, under A weighed quantity of the substance to be Method A.. Weigh or measure out a (luantity examined (such as binOxide of Manganese, of the liquid to be examined; pour it into a Cliromate of Potassium, or other oxygen coIn- glass stoppered bottle, and add to the mixture pound capable of generating chlorine with a lew grins. of pure chloroformnl, or of recently,chlorhydric acid) is placed in the decomposing distilled bisulphide of carbon, firee from'sulflask, together with a quantity of concentrated phur and sulphuretted hydrogen. The quan CHLORINE. 165 tity of material taken for analysis ought not of bromide of potassium to 13000 parts of to contain much more than 10 milligrms. of water, pentabrornide of iodine will alone be iodine. Pour the standard chlorine solution formed. In presence of' bisulphide of carbon from a burette, drop by drop, into the bottle, the combination of iodine with bromine to shaking the latter sharply after each addition, form IBr is marked by a change of the violet until the violet color of' the chloroform or the color of the liquid to yellowish brown, while bisulphide just disappears; 6 atoms of chlorine the formation of IBr5 is marked by the change consumed correspond to 1 of iodine. Or, still from violet to white. - In presence of a more simply, determine the value of the dilute bromide, consequently, proceed as follows:chlorine water, in the first place by making it Try, in the first place, whether the color will act upon a known quantity of iodide of po- change from violet to white by adding some tassium,- say 10 c. c. of a standard solution bisulphide of carbon, and then gradually chlocontaining 0.001 grin. iodine in each cubic rine water, to a portion of' the liquid to be centimetre. It may then be employed at once analyzed. In case the color does not thus upon the liquid to be examined; the amount of change dilute the liquid to the necessary dechlorine consumed upon the known weight of gree, and to make quite sure add half as much iodide of potassium being to the iodine therein again water as would be strictly required. contained, as the quantity used in the analysis Then proceed, as above described, as if no of the substance under examination is to x. bromine were present. The process yields The point of (lisappearance of the violet satisfactory results, and is particularly useful color can be hit with great precision. In for determining small quantities of' iodine in cases where so much iodine is present that it liquids highly charged with chlorides; and can itself color the aqueous liquid perceptibly, containing not too small quantities of broit is best not to add any chloroform or bisul- mides. [Comnpare the analogous principle phide until the brown iodine coloration first below, in which chlorine is made to decompose pro(luced in the liquid has been nearly de- bromide of potassiumn.] stroyed by the further addition of' chlorine. The foregoing process may be applied to the Since this way of proceeding is inadmnissable separation of chlorine, bromine and iodine, in presence of substances liable to be acted from one another as follows: - In one portion upon by free chlorine or iodine, —such, for ex- of the liquid throw down Bromide, Chloride ample, as the organic matters with which the and Iodide of Silver all together, collect and mother liquors which contain iodine are usu- wei(-h the mixed precipitate, and by ineans of ally contaminated; - the second way has often hot hydrogen (see Bromide of Silver) determto be employed. It is as follows: Add chloro- ine how much silver is contained in it. In form or bisulphide of carbon to the liquid another portion of' the solution determine the under examination, and then dilute chlorine amount of iodine by the method now in queswater of unknown strength until the liquid is tion, and calculate the amounts of' iodide of iust decolorized, and all the iodine has been silver and of silver corresponding to the converted into IC15. Then add a moderate quantity of iodine found. Deduct this calcuexcess of a solution of iodide of potassium. lated iodide of silver from the weight of the By the reaction of this iodide of potassium mixei precipitate of bromide, chloride and upon the chloride of iodine, 6 atoms of iodine iodide of silver, and the calculated amount of will be liberated and go into solution, silver from the amount of' that metal in the sKI + ICls = 5KC1 + 61. mixed precipitate. The remainders are reDetermine this Iodine by means of hyposul- spectively the joint amount of chloride and phite of sodium or sulphurous acid, and divide bromide of silver, and the quantity of silver the amount obtained by six. The quotient contained therein. For the method of calcuwill express the amount of iodine in the liquid lating the results see Bromide of Silver. The analyzed. - The process in both its rnod- quantity of bromine in the mixture must not ifications yields excellent results. It is partic- be too small, lest inexact results be obtained ularly well adapted fbr the determination of from the indirect method on which its estimavery small quantities of' iodine. tion depends. Still a third nloddfication of the process must To estimate a small quantity of an iodide in be resmrted to for estimating iodine in presence the presence of a large quantity of a chloride, of bromides. The Duprd's find that when the add dilute chlorine water of unknown strength solution of an. iodide contains 1 part or more to the liquid, drop by drop, with constant of bromide of' potassium in 1300 parts of shaking, till the violet coloration of the bisulwater, protobromide of iodine (IBr) will be phide has just vanished, and all the iodine formed on the addition of chlorine water. If, has been converted into IC15.:eparate tlhe on the other hand, the solution contains less aqueous solution firom the bisulphide, add than 1 part of bromide of' potassium in 1500 iodide of potassium in sufficient excess, and parts of water there will be formed in ad- determine the lodifte, which is set firee, by dition to the protobronmide of iodine, vary- means of hyposulphite of sodium, or in some ing proportions of the higher bromides of that'other appropriate way. Every six parts of element. If the solution contains only 1 part iodine found correspond to one part of' iodine 166 CHLORINE. in the original substance. The process gives rine water. The purpose of' the carbonate of good results. To avoid the trouble of pour sodium added before the evaporation, is to ing off the aqueous liquid fiom the bisulphide prevent the loss of bromine from decomposiand of washing the latter, the mixture may be tion of bromide or chloride of magnesium by poured into a rather narrow measuring cylin- heat. (Figuier, Ann, Chiim. et PAys., 33. 303). der after the chlorine has been made to act to Al[elhod B. The bromine liberated by means dedoloration, and the volume of the aqueous of chlorine is dissolved in ether, and the color solution noted. A definite portion of it may of this ethereal solution is compared with that then be measured out in a pipette for the ex- of other ethereal solutions containing known periment. ~ quantities of bromine. The plocess is applicPrinciple III. Power of decomposing met- able for the valuation of mother liquors, the allic bromides. amllount of bromine in which is known approxApp'icalions. Estimation of bromine anm imately beforehand. (Heille, Journ. pra!t. brolnhydric acid. Separation of bromine, Chenr., 36. 184.) Satisfactory results obchlorine and iodine from one another. tained by this method have been reported by Method A. This mlethod depends upon the Feldling (Journ. piak/t. Chem., 45. 269). The volatility of bromine as well as upon the prin- brine examined by this chemist could at thle ciple now in question. It was proposed for most contain no more than 0.02 grin. bromine estimating bromine for technical purposes in in;0 grims. of liquid. Hence he prepared ten mother liquors. When chlorine is mlade to ditoerent standard liquids by adding to as act upon the aqueous solution of a metallic many 60 grin. portions of a saturated solution bromide, each atom of it liberates an atom of of common salt, definite quantities of bromide bromine, and the latter imparts a yellow color of potassium, increasing regularly from 0.002 to the solution. But on boiling the liquid to 0.02 grin. of bromine. Equal volumes of the bromine escapes and the yellow tint disap- ether were added to each solution, and then pears. Hence by using a standard solution of chlorine water until there was no further chlorine, aind noting the point of' disappear- change observed in the color of the ether. It ance of the yellow coloration, the amount of is of' the highest irmportance to hit this point bromide in a liquid can be estimated volunmet- exactly, since too little as well as too much rically. The chlorine water employed must chlorine makes the liquid appear lighter than be highly dilute. It should be standardized it shouldl. To avoid all chance of error Fehljust before use, either by making it act upon ing prepared three samples of each of his stanla solution of bromide of sodium of known ard liquors, and chose the darkest colored in strength, acidulated with a few drops of chlor- each case for the comparison. Several samhydric acid in the manner described below; or ples each of 60 grins. of the brine to be exby means of iodide of potassium and hyposul- iamined are now weighed or measured out, the phite of sodium as explained above, undter same volulme of ether as before is added, then Principle IL. The liquil to be examined the chlorine water, and the color of the etheis placed in a flask and heatedl nearly to boil- real solution obtained is compared with that of ing; some of thile stan(lardized chlorine water the several ethereal solutions which were obis then added to it froln a burette covered tained from tie standard liquors. The mean with black paper, and the mixture heated fbr of' several good experiments is taken as the about three minutes, or until the yellow tint correct result. I)irect sunlight must be which' appeared on the addition of' the chlo- avoided, and the operations conducted with rine has disappeare(l, Then let the mixture expedition. According to Fresenius it is well cool for 2 minutes, drop into it another portion to use chloroform or bisulphide of carbon inof the chlorine water and again heat it. LPro- stead of the other. ceed in this way, until the last addition of clloe Method C. The chlbrine is' added in such rine fails to impart a yellow color to the liquid. quantity that it shall combine with the liberIn case the experiment should not be finislled ated bromine. Since chloride of' bromine under several hours, the strength of the chlo- merely communicates a yellowish tinge to chlorine water oulght to be redetermined at the elnd roform, while fiee brolline colors it yellow or of the operation, and the calculation of' the re- orange, the point at which the latter color dissult based upon the mean of the two trials,' appears, on the continued addition of a ~tandThe process is inapplicable in presence of ard solution of chlorine can be made to mark lodinie, the protoxides of iron and lnanganese the amount of bromine in a solution. The and organic matters. Mother liquors colored process is applicable for the analysis of bromyellow by organic matter may be evaporated ides of the' alkali-Iletals in neutral soluto dryness, after adding some carbonate of tions -and especially for the determination sodium and the residue gently ignited. The of small quantities of bromine in the mother residue may then be treated with water, and liquors from brine and kelp. It is as folthe solution filtered to fit it for analysis. In lows: —Place the solution to be examined this case as in others, where the liquid is alka- in a glass-stoppered bottle, together with as line, the solution must be slightly acidulated much pure chloroform as would fill a hazel-nut with chlorhydric acid before adding the ghlo- and pour dilute standard chlorine water upon CHLORINE. 167 the mixture, from a burette covered with black JMethod A. To estimate.chlorine gas lead paper. On shaking the bottle the chlorofolrm it carefully into dilute ammlonia water. A part becom;es yellow, then, on ftirther addition of of the ammonia is decomposed, and nitrogen chlorine, orange, then Sellow again, and evolved, while chloride of ammonia is formed. lastly yellowish white, at the moment when 2 - NH -+ 3C1 = 8NIHC1 + N. atoms of chlorine have been expended for each Care must be taken to bring in the chlorine as atomI of' bronine in the liquid. slowly as possible in order that time' may be KBr + 2C1 = KCl + BrC1. allowved for the decomposition, and that no The chlorine water is standardized with iodide chlorine shall go to waste with the nitrogen. ofp plotassiumn and hVposulpllite of soliun as ex- It is well to place the ammonia water in two or three Woulfiz bottles or connected flasks, plained above, under Principle II; its strength ree Woulfe bottles or connecte flasks, shoul be made to confor somewhat with the and still better to have nothing but water in amount of bromine to boe determinedt andw ad- the last flask to catch the vapors of chloride of ammonium whfich are formed. The ammn-onia jasted so that about 100 c.c. of it Ilmay ble used anrlnoniuml wiich are formed. The ammonia in an experiment. Considerable practice is in an experimnent. Considerable practice is lr~water must be in excess everywhere, not only that all the chlorine may be retained, but that require(l before the operator can be sure of the thall but that end reaction. It is well on that account to no chloride of nitrogen shall be formed. place the bottle on a slleet of' white paper, and When the development of chlorine has ceased, to have at hand a dilute solution of yellowv drive out those portions of' it which remain in chromate of potassium of the re(miretd tint the deconmposing vessel by means of a current 1of carbonic acid. Thie solution of' Chloride of with which to compare the color of the clloro- Ammonium may then be evaporated and form. The process yields good results; for example, 0.018 insteal of' 0.0185- 0.0585 in- weighled as described under that head; or the stead of 0.059, and 0.0112 instead of 0.01. If residue of the evaporation may be dissolved in the liquid to be examn-ined contains organic water, the solution acidulated with nitric acid, thze liquid to be examnined.l contains organic ttand the amount of' chlorine in the chloride dematter, add caustic soda to alkaline reaction, ant the ant ofc lore in the btloride deevaporate to dryness, igntlite the residue best ternfined as Chlorid e of Silver, by titration, in a silverate to dryness, dissolvite the residue in aterst From this result the weight of' the chloride of in a silver dish, dissolve the residue in water is then calculated. filter, neutralize exactly with chlorhydric acid aimoniun s then calculated. and test as above. (Reiinann, Annalen/ Chemn. In case chlorine water is to be estimated it und Phlrnm., 115. 140). may be carefully mixed with an excess of' dilute Bromine may be determined by tohis process amlonia water, and the mixture then evapoin presence of iodine by adding in the first rated. This process was formerly espllace, standard chlorine water until the violet teemed, but since SclLoenbein (Jouirm. prokt. color of the chloroform due to iodine is just Cteoa., 84. 386) has shown that a little chlodestroed, and Il (see Priniple II s rate of ammoniulll is fbrmed by the action of' or &IBr has been formed; aundI after warIlS chlorine on ammonia water, it can no longer adding more of thme clhlofine water until the be regarded as irreproachable. Fresenius rewhole of the brortine is converwted to BrCI. gards it as inferior to the process depending In the first step 6 atomls of' chlorine are ex- upon the action of Chlorine upon sulphurous pended for each atom of iodine, while of the acid. Experiments by Haarhaus (Zeitsch. second quantity of chlorine, every 2 atoms rep- analyt. Cliemt., 1863, 2. 59) indicated that of resent; one atomln of bromine. Suppose tlhere 100 parts of' free chlorine decomposed by amwere 5 molecules of KBr and. 1 oif KiI in the Imonia, 98.6 parts were converted into chloride miixture to be exramined; then, of anmmoniuml and 1.4 parts to chlorate of am-' oniumn. The proportion of' chlorate fbrmed. KI + SKIBr + 6c = 6IKC1 + IBrL. would be likely to vary however with the and degree of concentration of the ammonia water. IBr + 10+c(1 = ICO5 + iBrdC. But it could doubtless be got rid of by the use Method. To separate bromine from chlo- of an appropriate reducing agent. rine, precipitate from one portion of the solu- Method B. In liquids which contain free tion both these elements together as Bromide chlorine plus chlorhydric acid, or a metallic of Silver and Chloride of Silver, either by the chloride, the amount of' combined chlorine volumetric or gravimetric process. In another mnay be determuined as follows: — Mix a portion estimate the bromine by one of the weighed quantity of the liquid with an excess processes above described, and. calculate the of dilute ammonia water, and estimate the chlorine from the difference. According to total chlorine as Chloride of Silver. In Fresenius, this method affords an expeditious another weighed portion of the original liquid, means of examining the mother liquors of estimate the free Chlorine by means of iodide brine. of potassium, or in some other appropriate way Principle IV. Power of decomposing amn- and subtract this amount from the weight of monia. the total chlorine; the difference will repreA pplications. Estimnation of free chlorine. sent the combined chlorine. - It would be Sepalration of' fiee chlorine fiomn combined -wholly inadmnissable to mix the original soluchlorine. Valuation of'bleaching powler. tion with nitrate of silver, since only five 168 CHLOROPLATINATE OF AMMONIUM. sixths of the free chlorine would go down as phate of potassium as may be required to rechloride of silver, act upon the whole of the chlorhydric acid, fbr 6Ag20 + 12C1 = 10AgC1 + Ag20, C1205. the formation of chloride of potassium, and bi(Weltzien, Annalen Chem. und Pharm., 91. sulphate of potassium. Evaporate the mixture 45.) carefully in the dark to expel the free chlorine, Method C. To estimate the total chlorine and estimate the chlorine of the chloride of in bleaching powder mix the latter with anm- potassium by precipitation as Chloride of monia water, acidulate the liquor with nitric Silver. (Koene.) acid, and by means of a standard solution of For use as a reagent, chlorine gas may be silver estimate the chlorine of the chloride of prepared as follows: — Fit up a flask with a calcium which is formed. See Chloride of delivery tube, and connect it with a washincg Silver. The reaction which occurs between bottle charged with concentrated sulphuric the ammonia and the hypochlorite inay be acid, and a cylinder fill of chloride of calcium. formulated as follows: — Place in the flask a mixture of 18 parts by 4NI3 + 3 (CaO, C120 + CaCl2) - 6CaC12 + 62o0 + 4N. weight, of coarsely powdered chloride of soBy estimating the total chlorine in this way diuln, and 15 parts of finely powdered binoxide in one portion of the powder, and subjecting of' manganese, of good quality, and pour in a another portion to one of the processes of perfectly cold mixture of 45 parts of oil of vitChlorimetry, the amount of inactive chlorine riol, and 21 parts of water. On shaking the in the sample will be found from the difference flask a steady evolution of chlorine will set it between the two results. (Kolb, Comptes at once. When the flow of' chlorine shows Rendus, 65. pp. 530 —534). To destroy signs of slackening, heat the flask very gently any chlorate of calcium which the bleaching (Wiggers). - Hager (Zeitsch. anatlyt-. Chem powder may contain, treat the dilute mixture 1867, 6. 421) puts chlorate of potassium and of bleaching powder and ammonia water, after clhlorhydric acid of 25 per cent in a small the reaction between the two has ceased, with flask, in the proportion of' 2. 5 grins., of the zinc and sulphuric acid. The nascent hydro- chlorate to 25 grins. of the acid. The mix-gen evolved will reduce the chlorate to the ture must not be heated, nor shaken, but condition of chloride. (Fordos & Gelis). simply left to itself. - For the arrangeCompare Chlorates, reduction of by hydrogen. ments for developing chlorine devised by Method D. Instead of' weighing the chllo- Mitscherlich and Brugnatelli, see Zeitsch. ride of ammonium, as in Method A, the gase- analyt. Chem., 1867, 6. pp. 137, 393. ous nitrogen may be collected and measured, To prepare chlorine water, simply conduct as has been proposed by Henry & Plisson. the gas into a bottle of cold water until the The apparatus required consists of a flask of latter is saturated, taking care to lead off the the capacity of 300 or 400 c. c., to the cork of excess of chlorine into a chimlney, or into a which is fitted a funnel with glass stop-cock large bottle filled with pellets of' paper which and a delivery tube. The bent tube leadls to have been moistened with alcohol. Since a pneumatic trough, and there delivers gas chlorine water is rapidly decomposed by light, from the flask into a gra(luated tube of the it should be kept in a dark place, or in bottles capacity of 80 c. c. 10 grins. of the bleach- covered with black paper. ing powder and 250 c. c. of water are placed Chloroplatinate of Ammoniin the flask, and 100 c. c. of ammonia water Umn. diluted with an equal bulk of water, are gra d- Principle. Insolubility in alcohol. ually added through the funnel. Tile con- Applications. Separation of NH4 from Na, tents of' the flask are gradually heated and the Li, Ba, Sr, Ca, Mgr. Estimation of IN i4 in salts nitrogen is collected in the graduated tube, of alnmoniuml. Estimation of platinum. Sepwhich is clamped in a vertical position. Both aratioml of Pt from Mn, Fe, Ni, Co, Zn, Cd, the graduated tube and the pneumatic trough Ur, Hg, Cu, Bi. are filled with an alkaline liquid. When no Milethods. Same as those described under more nitrogen is givenl off, the flask is filled Chloroplatinate of Potassium. In estilnatilng with water through the funnel in order to ainmoniunm it is well to control the results of drive forward all the nitrcgen. T!4e Oxygen the first weighing as fobllows: —Ignite the from the air originally contained in the flask precipitate weigheld at 1000, in a platinum cruis then determined by absorption with pyro- cible, weigh the metallic platinum which is gallic acid, or in a;y other appropriate ivay, left and calculate the ammonium which correand the volumne of air to which it corresponds sponds to it. If the precipitate is pure, the is subtracted from the contents of the gradu- results obtained from the two weighings will ated tube. The process yields accurate re- agree. To ignite the precipitate roll it up in suits when carefully conducted, bVt is less con- the filter, place the ball in the crucible, cover venient than the methods in ordinary use. the latter and heat it moderately fbr a conmPrinciple V. Volatility. paratively long timle, then remove tihe cover, Application. Separation 9Q flree chlorine place the crucible upon its side, lay the lid in from free cllorhydric acid. firont of' the crucible anti bur1 the carbon o1ketoaod. Add to the solu.ti0q as ~puch sul- the filter at g gradually increased heat. CHLOROPLATINATE OF POTASSIUM. 169 Unless care be taken to heat the precipitate far more readily soluble (Fresenius). It unlvery gradually, particles of the precipitate will (lergoes no change in the air, or when heated be carried off by the escaping chloride of am- to 1000. WVhen ignited it gives off chlorine monia and some of the platinum be lost. In and chloride of amnllonium, and metallic platicase the amount of' precipitate is very small it num is left in the form of a porous sponge. is best to collect it at once upon an unweighed Its composition is. filter, and to ignite the dried mass and weigh 2NH4Ci 107 2.97 rtCl4 339.4 76.03 as platinum. So too in estimating platinum, or separating it firom other metals (see below). N9.. 28. 6.27 A little platinum will almost always adhere to l 21 47.72 the platinum crucible in which the ignition is Pt 17.4. 44.22 made, so that the crucible is heavier after the 446.4 100.00 experiment than before, but a platinum cruci- Chloroplatinate of Potassium. ble is nevertheless to be preferred to one of Principle. Insolubility in alcohol, antd ether. porcelain for effecting the decomposition of Also insolubility in a solution of chloride of the chloroplatinate. The process yields satis- ammonium. factory results, though owing to the sparing Applications. Estimation of K and Pt. Sepsolubility of the chloroplatinate and the liabil- aration of K fr)m Na, Li, Ba, Mg, (compare ity of losing a little platinum while igniting, Method D,) Sr, Ca, As, P, B, and S, and firol they are usually a little too low. other elements enumerated under Method B. In case both potassium and ammonium are Separation of Pt firolm Mg, Zn, Cd, Mn, Fe, to be separated from the other metals, ignite Co, Ni, Ur, Hg, Cu, Bi, and Au. the weighed precipitate of mixed chloroplati- Iethod A. To separate potassium fronm soI natos of' potassium and ammonium with the dium and lithium, weigh the mixed chlorides prescribed precautions, until the chloroplati- after they have been ignited to expel acid and nates are fully decomposed, treat the residue ammoniacal salts as explained under Chloride with water and in the filtrate determine the of Potassium, dissolve them in a small quanChloride of Potassium. Collect also and tity of water, add a decided excess of a pure, weigh the platinum for the sake of control. concentrated, neutral solution of biChloride of Calculate the chloride of potassium found into Platinum, prepared as described under that chloroplatinate of potassium, and subtract the head. Evaporate the mixture almost, but not latter from the weight of the mixed precipitate completely, to dryness on a water bath, add a in order to obtain the weight of the chloroplat- quantity of alcohol of 0.86 or 0.87 specific inate of ammonium. The method is seldom gravity, cover the dish with a glass plate ani employed. In case the precipitate is large, it let the mixture stand for several hours with will be well to finish the reduction in a stream occasional stirring. After the precipitate has of hydrogen, or to ignite the precipitate with settled, the supernatant liquid should exhibit a oxalic acid. In case the latter is employed deep yellow color, due to the presence of distake care to acidulate the filtrate with chlor- solved chloroplatinate of sodium. If it is not hydric acid. decidedly yellow, there is reason to apprehend In estimating platinum by adding chloride that too little of the bichloride of platinumn was of ammonium to its solution, it is not safe to used. Pour the clear supernatant liquid upon weigh the precipitated chloroplatinate of am- a weighed filter, but before transferring, the monium, since it is impossible to wash out with precipitate to the filter examine it carefully as alcohol a certain excess of chloride of ammo- to its purity. If the precipitate is a heavy nium (1 or 2 per cent of the weight of the yellow powder, exhibiting nothing but small precipitate) which goes down with the chloro- octahedral crystals when sufficiently mangniplatinate. It is essential in that case to ignite fled, it is pure chloroplatinate of' potassiumn, the precipitate, and weigh the metallic plati- but if tesseral crystals of a dark orange color, num (Fresenius). - Iln separating plati- transparent by transmitted lighllt, and of relnum from other metals, wash the precipitate atively large size, are visible, then the prefirst with a saturated solution of chloride of cipitate is contaminated with chloroplatinate amnmonium in order to remove the other of lithium (Jensch). If on the other hand metals, an(l finish the washing with alcohol. white particles of chloride of sodium are to Properties. The precipitated compound is be seen mixed with the yellow powder, then either in the form of a heavy lemon-yellow the quantity of bichloride of platinum used powder, or in smrall, bright yellow octahedral was insufficient, since some of the clhloride crystals. It is difficultly soluble in cold water,.of sodium has escaped being converted into but more readily soluble in hot water; very clloroplatinate of sodium. In this event sparingly soluble in absolute alcohol, but more add some water to the precipitate in the dish readily in spirit. At 15~ or 20~, 1 part of it to dissolve the chloride of sodium, then a dissolves in 265.00 parts of alcohol of 97.5 per new quantity of bichloride of platinum, evapocent; in 1400 parts of alcohol of 76 per cent, rate nearly to dryness and proceed as before. and in 670 parts of alcohol of 55 per cent. In The risk of adding too little of the platinum alcohol acidulated with chlorohydric acid it is solution nay bp avoided by employing a so 170 CHLOROPLATINATE OF POTASSIUM. lution of approximately known strength, and trate and wash water upon a water bath, discalculating how much of it will be necessary solves the residue in a very small quantity of to transform the whole of the weighed quantity water, adds alcohol, collects the new prec(ipiof chlorides taken into chloroplatinates. tate of chloroplatinate of potassium upon a When the yellow precipitate is of proper second unweighed filter and washes it with appearance, transfer it from the dish to the alcohol. After having been dried, the precipfilter, by means of the filtrate rather than with itates are carefully removed from the filters, alcohol, wash it with alcohol. of 0.86 specific dried at 100~ and weighed, while the two filgravity, and dry at 100~ until it ceases to lose ters are burned, the ashes leaclhed with water weig(ht; or, better, wash with a mixture of 4 and the chloride of potassium thus obtained parts of such alcohol and 1 part ether. Such determined by itself. a mixture of alcohol and one-fifth or one-sixth The quantity of' sodium in the substance ether - in which the chloroplatinate of potas- analyzed is usually estimated "by the liffersium is as good as insoluble - is used by many ence," i.e., by subtracting firom the weight of chemists. It was first proposed by H. Rose. the mixed chlorides taken that of the chloride (Berzelius's Lelrbuch der Chemie, 4 AuJf., 10. of potassium, which corresponds to the chloro73). In order to be certain that no potassium platinate obtained. Some chemists, however, is left in the solution, add some water to the prefer to add oxalic acid to the filtrate firom filtrate, and some bichloride of platinum, to- the chloroplatinate of potassium, to evaporate gether with some chloride of sodium, in case to dryness, to ignite, to take up with water the the proportion already present is supposed to Chloride of' Sodium, and to weigh it as such. be small. Evaporate the mixture nearly to If this is to be done, it is still essential to dryness upon a water bath no hotter than 750~ make the special secondary trial for potassium and treat the concentrated liquor in the man- as above described, else any potassium left in ner already described. In case any precipi- the filtrate will be weiglhed as chloride of sotate of chloroplatinate of potassium is formed, dium. Instead of estillat.ng the sodium as collect it upon a special filter and add its chloride, sulphuric acid may be added to the weight to that of the principal precipitate. filtrate from chbloplatinate of potassium, the The object in adding chloride of sodium is to mixture evaporated to dryness and ignited, prevent the decomposition to which bichloride the residue extracted with water and evapoof platinum is subject when its alcoholic solu- rated, and weighed as Sulphate of' Sodiullu. tion is evaporated. The temperature is kept (A. Mitscherlich, loc. cit.) The best wayx is to at 75~ during the evaporation of the alcoholic spare no pains in determining the potassium, liquor fbr a similar reason. (Compare A. Mits- and to take the sodium firoin the difference. cherlich's precautions, below). - In evaporat- By good rights, the compound of' potassium ing the original mixture of bichloride of' plati- and sodium to be exaufinec should be a chlonum and potassium solution upon the water ride, though it is possible to separate sodium bath, care must always be taken not to push from potassium in this way, even in presence the process to dryness, or so far as to expel any of boracic, phosphoric, sulphuric andl other water of crystallization from the chloroplati- acids soluble in alcohol, as vill be explained nate of sodium which is to remain dissolved. below, under Methodl C. For the methods of When properly executed the process yields converting other salts to the state of chlorides, good results, though there is usually a small see Chloride of Potassium, and the methods of' loss of potassium due to the sparing solubility separating acids from metals, as given in the of the precipitate in alcohol. On the other finding lists of the appendix. hand, it must be remembered that the air of a When the amount of' chloplatinate of' potlislaboratory often contains ammonium salts siunl to be collected and weihlled is very small, which may go to form chloroplatinate of am- it is better not to atteinpt to collect it upon a monium, and so increase the weight of the po- weighed filter. Instead of that it should be tassium compound. According to Fresenius, re- collected upon a very small unweighed filter, peated experiments have shown that in this and ignited in a crucible after it has been method of separating potassium from sodium, washed and dried. The ignition, which mnay the amount of'potassium found is always a little be made in a platinum crucible, must be conless than it should be. When the process is ducted with special care, in the manner deproperly conducted, however, the loss of potash scribed under Chloroplatinate of' Amnimonium. ought not to exceed 1 per cent. - In order The residue left after the ignition is carefully to avoid the possibility of decomposing any of' treated with hot water, the solution of chloride the bichloride of platinum by evaporating the of potassium thus obtained is decanted off' alcoholic solution, A. Mitscherlich (Journ. from the heavy powder of metallic platinum, pralt. Chem., 1861, 83. 460) prefers to add and the latter is washed, dried, ignited and bichloride of platinum to a concentrated aque- weighed in the crucible. Each atom of platious solution of the mixed chlorides of potassium num found corresponds to two atonis of poand sodium and without adding any alcohol, to tassium. A small quantity of platinuml will collect and wash the precipitate upon an un- remain adhering to the crucible, so that the weighed filter. le then evaporates the fil- weight of the latter will be greater after the CHLOROPLATINATIE OF POT'ASSIUM. 171 experiment than before, but the accuracy of bulk of a mixture of 2 volumes alcohol of the results is not impaired, and no serious 0.8 specific gravity, and 1 volumne of ether; harm is done to the crucible. The decanted collect the mixed precipitate of clllorol)latincate liquid will be colorless if the decomposition of of potassium and sulphate of' sodium uipon a the chloplatinate is complete; no tinge of filter and wash it with a mixtiure of alcolol yellow is perlissible. The metallic platinum and ether, such as was poured upon the residtue should be washed until the washings cease to in the dish, until the washings are colorless. give a reaction for chlorine when tested with Then wash the matter in the filter with a cold, nitrate of silver. - Quantities of the chloro- saturated, aqueous solution of' chloride of' anplatinate wlhich weigh less than 0.03 grin. can be monium, until the washings no lonoer give any safely decomposed by ignition in this way, but reaction when tested for sullphuric acid. If with larger quantities it is not easy to obtain the filter be filled completely full once or good results. The melted chloride of potas- twice with the solution of chloride of alnmoslum so envelops the carbon of the filter that niuml, so as to thoroughlv saturate the paper, the latter cannot be thoroughly burned, not and the i)recipitate, it will be easy to -wash even after it has been washed with water. It out the whole of the sulphate of' sodiuim. is, moreover, difficult to complete the decom- The chloroplatinate of' ammiioniuii fortmed by position of the chloroplatinate; to facilitate the action of the chloride of ammllloniurlm upon the decomposition a small quantity of oxalic any portions of bichloride of platinum wllichl acid may be made to act upon the sub- the precipitate may have retainied does no stance in the crucible. If this be done, let harm. - To dletermine the potassium in the crucible become cold after the process has the precipitate, dry the filter, with its contents, been pushed so far that the filter has been in a large porcelain crucible, at a temperature burned to ashes, throw in a minute fragment sonmewhat above 100~, and heat the crucible of pure oxalic acid, cover the crucible and until the filter has charred, but has not yet ignite gently at first, but afterwards at a strong beguIn to glimmer, then lead a current of' hv — red heat. By the aid of oxalic acid it is drogen into the crucible, and continue to heat possible to decompose the chloplatinate in a it as long as the escapiing gas yields a white porcelain crucible. A still better way is to cloud when tested with ammonia. The reducignite the precipitate in a current of hydro- tion by hy(lrogen is tolerably rapidl at tempergen at a temperature so low that the chloride attures as low as 24(~. Treat the residue with of potassium cannot fuse. This reduction may hot water, separate the chloride of potassimlim be effected in a crucible of platinum, into fi'om the Inetallic platinumi and charred paper which hydrogen is admitted through a hole in by filtration, wash thoroughly, evaporate to the cover. But in order to avoid losing any dryness and ignite, to expel any trace of' ehloparticles of the compound in the current of ridle of amm(nonilum; then weigh the Chloride gas, the chloroplatinate should be partially of' Potassium d(iiectly, or estimate the chlo:)rine decomposed by carefully heating it by itself' in it by titration with a standard solution of before hydrogen is admitted to the crucible. nitrate of silver (see Chloride of Silver). After the hydrogen has acted, wash out the In case the precipitate of' chloroplatinate of chloride of potassium and ignite the residue in potassium is small it may be dissolved off the the air to destroy the last particles of carbon filter with boiling water, the solution evapofrom the filter. rated to dryness in a porcelain crucible, the Method B. A modification of the foregoing residue ignited to expel cliloride of ainmoniun, method has been proposed by Finkener (Pogrlq- and then reduced by means of hy(trogen. endor['s Annalen, 1866, 129. 637). It de- The chlori'ne in tile residue may then be estipen(ls in part upon the insolubility of the mnated volunmetrically, as Chloride of Sil-er, chloroplatinate in a strong solution of chloride without filrther trouble. The sodliul, of amlmonium, and( is applicable to the separa- which will be fobund fo the most part in the, tion of' potassium from sodium when this metal chloride of aminonium wxaslhings, tay be reis present in th? form of a sulphate. - The covered by evapolating these, together with details are as follows: -Dissolve the mixed the alcoholic filtrate, hut the operation is very sulphates in a small quantity of water, add troublesome. The process gives tolerably some chlorhydric acid, and enough bichlori(le satistactory results in spite of the fact that the of platinum to color the liquid intensely yel- chloride of ammloniumn decomposes and dislow; dilute the inixture with so much water, solves a little of tile potassium precipitate, for that the whole of the chloroplatinate of potas- a -trace of' sodiuml is always retained by the siuin will dissolve on boiling, and evaporate potassiumn precipitate. For a quantitative the solution upon a water bath to a small vol- discussion of the several sources of error see unie, so that a pasty, but not solid residue will Finkener's memoir. - The processo can be be left when the dish is allowed to cool. Care applied for separating potassiuim from lithium, must be taken not to leave the dish upon the as well as fiom sodium. In case lithium and water bath after the liquid has once been suf' sodiuin are both present, the first filtrate, i. e., ficiently evaporated. Stir into the cold residue, the one obtained before washing with chloride at first by small portions, 15 or 20 times its of amnmonium, nmay be treated to remove the 172 CHLOROPLATINATE OF POTASSIUM. excess of platinum, and the lithium may then as has been already remarked. H. Rose dibe precipitated as Phosphate of Lithium. rects that about 1 grin. of chloride of potas-Potassium may still be estimated by this slum be taken, that it be dissolved in 15 c. c. method in presence of arseniate, borate, and of water, and that after the addition of the phosphate of sodium, or the sulphates of Mg, requisite quantity of bichloride of platinum a Zn, Mn, Fe, Ni, Co, Cu and Al. It is only mixture of 75 c. c. absolute alcohol and 15 c. c. necessary to mix a little chlorhydric acid with of ether be added to the liquid. In order to the first portions of chloride of ammonium prevent the evaporation of the ether place the used for washing the mixed precipitate of mixture under a bell glass set upon a plate of chloroplatinate and sulphate. When the mix- ground glass which has been smneared with ture to be analyzed contains no sulphate, but glycerine, and leave it at rest for 12 hours, only nitrates, beorates, phosphates, arseniates, then filter, wash with a mixture of alcohol and etc., enough sulphuric acid must be added to ether and weigh. convert the whole of the metals present into A modification of this process has been desulphates. The presence of a moderate ex- vised by Teschemacher and D. Slnith (Zeitsch. cess of sulphuric acid does no harm. - It analyt. Chem., 1869, 8. 90) for the rapid islot safe to attempt to reckon the potassium commercial analysis of saltpetre and other from the quantity of platinum left after the potassium salts:- Weigh out 500 grains of ignition and reduction of the precipitate. The the salt, dissolve in water and dilute the soluresult might readily come out too high, espe- tion to the volume of 5000 fluid grains; neascially if much sulphate of sodium were pres- ure out 500 fluid grains of the liquid, and ent, or a large excess of bichloride of plati- dilute again to 5000 grains. Take 1000 fluid num were used, or the evaporation so grains of the diluted liquid, add to it 50 fluid conducted that comparatively large crystals of grains of chblorhydric acid, if the salt be not sulphate of sodium should form and enclose already a chloride, and wash the mixture into some of the platinic mother liquor. The best a dish. Heat the liquid, which should amount way in case the potassium is to be calculated to about 1500 grains in all, almost to boiling, from the weight of the platinum is to omit al- add to it a large excess of a solution of bitogether the washing with chloride of ammo- chloride of platinum, so that as nmuch as 20 nium, and to proceed as in Method C. grains of platinum may be present, and evapAccording to Stohmann (Zeitsch. analyt. orate so far upon a water bath that the liquitl Chem., 1866, 5. 307) there is no difficulty in would stiffen to a pasty mass if the dish were applying Method A for the separation of po- removed from the bath and allowed to cool. tassium from barium, calcium and magnesium, Without allowing it thus to stiffen, quickly since the chloroplatinates of all these metals pour upon the concentrated liquid 500 or 600 are soluble in alcohol. In case a mixture of fluid grains of rectified methyl alcohol of 85 sulphates and chlorides of potassium, calcium per cent, mix the materials by givilig a rotary an(l magnesium is to be analyzed, add chloride motion to the dish, cover the dish, and let the of barium, drop by drop, to the boiling solu- mixture stand for 5 minutes. Tile (hlorotion, until all the sulphuric acid is precipitated, platinate of potassium will separate in the obrmn filter, and treat the filtrate, or a measured of large crystalline scales, from which the portion of it, with bichloride of platinum in supernatant liquid can be readily and conmthe usual way. A good deal of bichloride of pletely decanted. Pour the liquid into a coniplatinum will be required in order to convert paratively large filter — large enough to hold the whole of the foreign metals into chloro- 400 or 500 fluid grains, and wash the crystals platinates, but it is readily recovered from the in the dish twice by decantation with methyl filtrate. alcohol; then by means of a wash bottle, alnd lfethod C. To estimate potassium in any of without touching them witll a rod lest they be its compounds proceed as follows: - If the broken, wash the crystals out of the (lish into potassium salt contain only a volatile acid, the filter, and wash them there thoroughly like acetic, nitric or cvanhydric acid, the solu- with methyl alcohol. After the filter and contion may simply be mixed with an excess of tents have been dried, the precipitate can be chlorhydric acid, evaporated to dryness to removed fiom the filter so colmpletely that the convert the salt to Chloride of Potassium, and latter can be burned to ashes by itself; and the treated with bichloride of platinum, as in ashes and dried precipitate weighed together Method A. - If the substance to be ana- in a crucible. The process yields excellyzed is a bromide or iodide of potassium, lent results. In describing it, Tesclemacher treat it with chlorine water, evaporate to dry- and Sinith take occasion to deny the alleganess, redissolve the residue in chlorine water, tions of Chalmers and Tatlock (loc. cit., rp. and again evaporate to expel the last traces of 88) that on account of the frequent impurity bromine or iodine. - Instead of proceed- of the bichloride of platinum employed in ing with the analysis precisely as in Method laboratories the processes depending upon the A, some chemists prefer to omit the evapora- principle now in question are unreliable, and tion after the addition of the bichloride, and apt to yield results by which the potassium is to wash with a mixture of alcohol and ether, estimated 1 or 2 per cent higher than the truth. CHLOROPLATINATE OF POTASSIUMI. 173 In case the potassium be combined with a precipitate has been dried and weighed at non-volatile acid, such as phosphoric, arsenic, 100~, reduce it to metallic platinum by means boracic or sulphuric acid, which is soluble in of hot hydrogen gas. See Platinum Coinalcohol, or in mixed alcohol and ether, make a pounds. - The weight of platinum in the strong aqueous solution of the salt, add some precipitate cannot be calculated from the chlorhydric acid, then an excess of bichloride weight of the latter, since it is impossible to of platinum, and a quantity of the strongest wash out all the chloride of potassium by alcohol, or of mixed alcohol and ether, let the means of spirit without dissolving a portion of mixture stand for a number of hours and the chloroplatinate as well. The process is filter, etc., as in Method A. According to preferable to that which depends upon the Finkener, for 1 grin. of the potassium salt insolubility of Chloroplatinate of Ammoniui.m, 30 c. c. of chlorhydric acid of 1.05 specific since the latter is rather more soluble in alcogravity, 150 c. c. of anhydrous alcohol, and hol than chloroplatinate of potassium, and 25 c. c. of other may be taken. After the because with the potassium salt there is less mixture has stood under a bell glass for several risk of losing material in the subsequent prohours, it may be collected on a weighed filter cess of reducing to metallic platinum. and washed with a mixture of chlorhydric Properties. The precipitate occurs either as acid, alcohol and ether, in the above given a lemon colored powder, or as small reddishproportions, until the filtrate is colorless, and yellow octahedrons. It is difficultly soluble in. afterwards with alcohol and ether. The cold water, hut more readily in hot water. It method can be applied for separating potas- is almost completely insoluble in absolute alcosiumn from sodium and lithium, as well as for hol, and still less soluble in a mixture of estimating potassium. Compare Method B. alcohol and ether; in ordinary alcohol it is 1Method D. To separate potassium from mag- somewhat, though still sparingly, soluble. Acnesium and, sodium, Scheerer (Annalen Chemn. cording to Fresenius, 1 part of it dissolves in und Phazrm., 112. 117) weighs the mixture in 12,000 parts of absolute alcohol, 3,800 parts of the forma of anhydrous sulphates, divides the alcohol of 76 per cent, and 1,000 parts of aqueous solution into two measured portions, alcohol of 55 per cent. In alcohol acidulated and precipitates chloroplatinate of potassium with chlorhydric acid it i4 considerably more in one portion of the liquid, and Phosphate of soluble. It dissolves readily in caustic potash, Magnesium and Ammonium in the other. By According to Andrews it retains a little water calculating both the potassium and the mag- (0.0055 of its weight) even when heated to nesionm found as sulphates, and subtracting the temperatures considerably above 1000. When sunm fiom the weight of' the original mixed left in the air, or heated to 1000 it undergoes sulphates, the weight of the sulphate of so- no change, but at an intense red heat it suffers dium will be obtained. - Instead of divid- decomposition, some chlorine being expelled, mng the liquid, Rube (Journ. prakt. Chem., 94. and a mixture of metallic platinum and chlo — 117) precipitates ehloroplatinate of potassium ride of potassium being left. This decompofromi the whole of' the dissolved sulphates, and sition is never complete, however, if any evaporates the filtrate a second time to make considerable quantity of the compound is igsure of the whole of the potassium.'He then nited. Even after long continued fusion of adds to the filtrate a solution of chloride of the mass, a little of the chloroplatinate will nmmnlonium to remove the excess of platinum, always remain undecomposed. To reduce this filters off the clloroplatinate of anlmonium, last trace, the substance must be ignited in an alndl throws down Phosphate of Magnesium atmosphere of hydrogen, or with oxalic acid,. and Amlmoniuml in the filtrate, as has been described above. (See also Plati — fet(hold E. T1 estimate pla;inum in platinum num Compounds.) compovtnCds, and to separate platinum firom the The composition of the chloroplatinate is: — metals above enumerated: — Add caustic pot- K_- s8.2 - G0.01 ash to the solution until the free acid, if any Pt - 197.4 - 40.40 2KC1 - 149.2 - 30.54 there be, is nearly neutralized, then add a Ci6 213.0 - 43 PtC4 - t9.4- 4.60 slight excess of a strong solution of chloride of 488.6 100.00 488.6 0000 potassium, and a comparatively large quantity Principle I]. Power of decomposing or-' of absolute alcohol. In case the solution be ganic substances. very dcilute, it should be concentrated by evap- Application. Estimation of carbon, hydrooration before adding the alcohol. After the gen and nitrogen directly, in one and the same~ nmixture has been allowed to stand for 24 quantity of material. hours, collect the precipitate upon a weighed 3Method. A weighed, quantity of the sub-, filter, as directed in Method A. - Ift no stance to be analyzed is shaken into a metal other than platinum be present, wash at porcelain tube which is filled with a mixture once with alcohol of 70 per cent, but if' other (containing about 8 grilns. of platinum) of' metals aie contained in the mixture wash the pumice stone and chloroplatinate of' potassium, precipitate first with a saturated solution of and the air is expelled from the apparatus by chloride of potassium to remove these metals, a stream of tolerably pure niitrogen.. To the and afterwards with the alcohol. After the front of the tube there is attached first a tube 174 CHOLESTERIN. chiargedl with anhydrous phosphoric acid, then Application. Separation of cholesterin from three sets of bulb tubes charged with solutions fats, and estimation of' cholesterin in a.nlimal of' nitrate of lead, stannous chloride, and caus- and vegetable substances. tic potash respectively. The lead and tin IIet hod. Treat the substance to be exanmsolutions are as concentrate(d as possible, while ined with ethel, as long as anything dissolves; the potash lye is such as is ordinarily eml- remove any water which may settle fronm the iloyed in estimating Carbon. In case there is ethereal solution, and decant or filter the latno lihydrogren in the substance to be analyzed, ter so that it may be perfectly clear. Distil the phosphoric acid tube is omitted. - Af- and evaporate the ethereal solution to dryness ter the apparatus has been proved to be tight upon a water bath, and weigh the residue. the porcelain tube is heated to redness in the Boil the residue, or a weighed portion of it, places where none of' the organic substance with an excess of a clear concentrated alcohas been placed; afterwards the mixture of holic solution of caustic potash upon a water substance and chloropllatinate is gradually bath for several hours, then distil off the alcoheated, so that the substance may be slowly hol and dissolve the residue in water to a thin decomposed. The chloroplatinate of potas- solution, shake this solution with ether, allow sium is employed as a substitute for free chlo- the mixture to settle, and decant the ether, fine, on the ground of' its beinlg an easily de- taking care to repeat the process several times. composable chlorine compoutnd. It has the The ethereal solution thus obtained contains merit of' beingj free from water, and inalterable the cholesterin in a condition of' almost absoin the air. When heated by itself' it suffers lute purity. The weight of' the cholesterin is but little decomposition at a low red heat; but found by evaporating the solution to dryness. when heated to redness in contact with or- In case the cholesterin solution were not pure ganic substances it is completely decomposed. the residue obtained by saponification might Carbonic acid, chlorhydric acid, carbon, as be shaken, while still warim, with dilute potash well as water and hydro-carbons in some lye, and again treated with ether after the cases, are the prodtucts of' the reaction. The mixture. had become cold. None of the soap water, chlor-hydric acid and carbonic acid are will go into solution in the ether unless there collected and w-eighed in the reagents above is a lack of water or alkali in the mixture. described. And in case hydrocarbons or By treating the soap solution with chlorhydrie chloride of carbon. are generated they are acid after the removal of the cliolesterin, and burned (compare Carbon, Method 7), and washing the acid liquor with ether, the fatty their carbon weighed as carbonic acid. acids may be dissolved out and weighed after WhTlen the porcelain tube has'been heated the ether has been evaporated, or after their throughout to redness, anrd no more bubbles of conversion into sodium salts. (Ifoppe-Seyler, gas are seen in the nitrate of' lead bulbs, the Zeitsch. analyt. Chem., 1866, 5. 422.) tube is swept clean by a slow current of nitlro-method of gen arndl the fire is extinrgtished. The object m of, the so. lutio of staingr iris ch.l i ist n N those metallic chrornates which are (leof thte solation of' stannous chloride is to ab- conpsle by eat see uner Chroic sorb the excess of chlorine restulting firom the Ac heat, n Acid decomposition of by heat. decomposition of the chloroplatina,te. After d c the absorption bulbs have been weighed, Chromk Acid. [Compare biChromate those which contain potash are reattachedl to of Psotassiumla.] tile porcelain tube, the latter is reheated, and Cliromic acid may be estimated as Chroomate a stlenlll of o~xygren is passed through it to of Barium, Chromate of Lead, and Clhrolmate consullle the free carbon left in the tube at the of ierllry, or better, by deterlining the 1co~e oi the previous reaction. In case any aiimount of eflicient oxygen contained in it. nonvolatrle chloride of carbon condense in the It mav also he re(luce(i to thc conditioi of sestube some oxide of' copper should be placed in quioxide and tllron dow IIas rate of the tube before the latter is reheated. At the Chromium. end of the experiment pass a current of chlo- To separate chromic acid from ses(lniositle rine into the hot tube to revivify the chloro- of chrouiinm, deterline in one portion of tle platinate of' potassium, so that the tube shall material tlre chromnic acid, accordlir to one of be left in readiness for the reception of matter the methods described belov, tlen reduce fbr a new analysis. (A. Mitscherlich, Zeitsch. another portion as below, and estilate the anecl;yt+. Chemw., 1868, 7. 272.) xlwhole of the chroniuln as Hydrate of ChroChloroeus Acid; npo.ull mium, or oxidize this second portion, as dePC'ii:lpc!. Oxidizing power. scribed under Chlrolnate of Sodium, and Applications. Estimation of chlorous acid estimnate the whole of the chroniuiim as Chroanid chlorites. mic Acid. JfIethodl. See Chlorine and Chlorates, — Prciple I. Osidizin pow er. notably the paragraphs on action of a chlorate Applicatioois. Reduction of CrO3 as a preupon a ferrous salt, and upon nitrous acid. lilninarv in the estimation of Cr or to the sePCholesterin. llaration of H,2SO4 tfrom CrOs (Methods 1 and Prirnciple. Solubility in ether and inertness 9). Valuation of chromates, such as bicbroas regards potash. mate of potassium and chrome yellow, separa CHROMIC ACID. 175 tion of Cr from Na, K, NH4, Ba, Sr, Ca, Mg, In case permanganate of potassium is to be Co, Ni, Mn, Zn (Method 1, B), Cd, Pb, Ag, employed, take care to dissolve the standard H?, Cu, Bi, Sb, As, Sn, Au, and Pt. Separa- iron in diluted sulphuric acid, and to dilute tion of Pb from CrO3. Estimation of Fe in largely the solution into which the perlmangacompounds and ores of iron. Estimation of nate is to be poured. Instead of dissolving a Arsenious Acid, ferrous salts, and other com- fresh piece of metallic iron for each experipounds oxidizable by nascent chlorine (Method ment, a weighed quantity of pure sulphallte of 1, B). Estimation of nitrous acid in presence iron, prepared as described under Chlorine, of nitric acid. Valuation of nitrite of sodium may be taken; or, in case a considerable num(Method 5). Valuation of crude ferrocyanide ber of determinations are to be made all at of potassium (Method 6). once, measured portions of a standard solution lMlethlods. of ferrous chloride may be used. The method yields excellent results (Schwarz). To del. Reduction of Chromic Acid by Chlorhy-. termine the chromic acid in dry chromate oft dric Acid. lead, place a weighed quantity of this subA. Gravimetric. Chromic acid or a chro- stance in a mortar, pour upon it the standard mate may be readily reduced to the condition solution of iron and a quantity of chlorhydric of sesquichloride of chromium by boiling the acid, and grind the mixture thoroughly. Add dry substance with an excess of concentrated water, and proceed to estimate the residual chlorhydric acid. The process is preferable to ferrous salt (Mohr, Titrirmethodle, 1855, 1. 240). those in Wvhich alcohol, sulphuretted hydrogen, See further Chromate of Lead. or sulphurous acid are employed to effect the B. Another way of estimating chromic acid, reduction. The solution of sesquichloride of depends upon the titration of the ferric salt chromium obtained should be largely diluted formed. For the details of this process see. with water before any reagent is added to it. Chlorates, action of' upon ferrous salts. To To separate chromium1 from the alkali-metals avoid the effects of any interference with the in such a solution, add ammonia water at final reaction which migl be occasioned by once to throw down Hydrate of Chromnium; the presence of chloride of chromium in the but to separate chromium from sulphuric acid, solution to be titrated, put a corresponding. or from barium, precipitate these substances quantity of chloride of chromium into the as Sulphate of Barium befole attemnpting to normal iron solution before standardizing it, throw down the chromium. - To separate so that similar conditions may obtain in all Cr fiorn Co, Ni, Mn and Zn, add Carbonate of cases. (Braun, Zeitsch. analyt. Chem., 1867, 6. Barium to throw down Hydrate of Chromium pp. 63, 54). (or better, adopt the volumetric method de- C. For the method of estimating iron see scribed in ~ B).. biChromate of Potassium. B. fVolumetric. See Arsenious Acid, oxi- 3. Reduction of chromic acid by Oxalic A cid. dation of by nascent chlorine; and Chlorine, A. Gravimetric. Treat a mixture of the action of on Asg03 and on KI, for descriptions chromate to be analyzed and oxalate of soof' apparatus proper for effeecting the decompo- diuln with sulphuric acid, and collect and sition and absorbing the chlorine which is set weigh the Carbonic Acid formed, or estimate free. See also biChromate of' Potassium. the Carbonic Acid by the loss. 2. Reduction of Chromic Acid by a Ferrous 2CrO3 -+ 3C2Na204 +.6-32SO4 = 6C02 +-Cr2o3, 3SO3 + Salt. 33(Na20, SO3) + 61-20.. A. To estimate chromic acid, acidify with For each grIn. of chromic acid present it sulphuric acid the not too dilute solution of the substance 2.25 grins. of oxalate of sodiumn the chromate to be examined, and add to it will be required. Oxalate of ammoniuml or the solution of' a definite quantity of iron, pre- oxalate of barium may be used instead of pared as explained under Chlorine (action of oxalate of sodium in case either of' the fixed on ferrous salts). The mixed solution should alkalies are to be estimated in the residue. be strongly acid, and should of course contain For the details of' the process see binOxide of an excess of the ferrous salt. The reduction Manganese (Vohl, A nmalen Chem. ulld Pharm., of' the chromic acid by the iron solution is in- 63. 398). stantaneous. By means of a standard" solu- The process may be employed in connection. tion of' Permlanganate of Potassium, or of with the so-called methodl of" Limited OxidabiChromate of Potassium, proceed to estimate tion" (see Carbop, p. 75), in which certail~ how much of the iron in the mixed solution organic substances are oxidized by chromiic has been left in the state of' a ferrous salt. acid, while others are unacted upon. It is The diffelrence tetween the amount of iron claimed for the method of limited oxidation, thus found and that originally taken, will as thus applied, that it will be found useful in show how much iron has been changed from a studying the true composition of niany organic ferrous salt to a ferric salt by the clhromic acid products,. such as quinine, thein, morphine, in the substance; - the reaction may be sup- the essential oils, etc., and that by means of posed to be as follows:- it the nature an(l quantity of impurity in an GFeO + 2CrO3 = 3Fe2C03 + Cr2Os, organic substance may be determined. - As 176 CHROMIC ACID. has been already stated under Carbon, the when charged only weighs about 190 grammes. acids of the acetic or fatty series, when once To use the apparatus, the absorption apparaproduced by the action of dilute chromic acid tus is detached and weighed, after it has been on organic substances, withstand all further allowed to stand for some time in cold water, oxidation by that reagent. But the oxidation and to hang fbr half an hour in the balance of any organic substance to the state of fatty case; or better, in a room of constant temperacid takes place with almnost mathematical ature. It is then reconnected with the apparaprecision, as is readily proved by the close tus, and the cold chronic solution is poured agfreement between the amount of oxygen into the generating flask. Before charging actually consumed in experiments fobr effecting the flask some fiagments of tobacco pipe the oxidation, and the amount required by should be placed in it in order. to prevent the theory. The amount of oxygen consumed liquid firom bumping when it subsequently might be determined by estimating the sesqui- comies to be heated. After the introduction oxide of chromium which has resulted from of the chromic solution pour in the oxalic the reduction of the chromic acid, but there solution, together with some dilute acid, both are objections to that. method, inasmuch as cold, by means of' an ordinary funnel. No ammonia cannot be used for precipitating the loss of carbonic acid need be apprehended at sesquioxide and the washing out of the soda this stage, since some minutes elapse after the salts or potassium salts, resulting from the use mixture is made before any of that gas is of' fixed alkalies, is difficult. Moreover, the evolved. Thrust the cork into the flask and atomic weigoht of chromium is still so uncertain close the stop-cock which it carries. In the that the calculation ought not to be based upon course of a few minutes the evolution of carit in cases where great accuracy is required. bonic acid commences, and large bubbles of A better Way is to determine the chromic acid air are forced out through the drying and abwhich has escaped reduction, and subtract sorption vessels. After the comparatively this amount from the known quantity of large amount of air which the apparatus con — chromic acid taken. - The estimation of tains has been expelled, the absorption of the chromic acid may be effected by means of carbonic acid is confined almost entirely to the oxalic acid, as described above. Determine Woulfe bottle. After a short time air will in the first place the strength of the chro- begin to be sucked back into the apparatus mic solution by treating a weighed quantity of through the Liebig bulbs. When this happens it with an excess of oxalic and sulphuric acids, heat the generating flask gently, but not and absorbing and weighing the carbonic acid enough to force gas beyond the Woulfe bottle. formed. Then digest a weighed quantity of When no more carbonic acid goes forward the organic substance to be analyzed with a heat the contents of the generating flask to weighed excess of the chromic solution, and boiling, so that the steam may drive out the after the reaction is comnplete treat the mix- carbonic acid. After the steam has fairly ture with oxalic and sulphuric acids as before, passed into the sulphuric acid for a few secin order to determine how much chromic acid onds remove the lamp, and the moment the remained unreduced. The difference between sulphuric acid begins to rise in the pipette the two amounts of carbonic acid indicates open the stop cock above the generating flask, how much oxygen has been consumed. so that air may enter and prevent any regurThe following apparatus may be employed:- gitation. During the process of boiling out For the generating vessel provide a flask with some air will have begun to enter the potashan outlet tube fused into its neck. Close the apparatus. Suck now a little air out of the flask with a periforated cork carrying a stop- potash-apparatus, plug its outer end and cock tube, the lower extremity of' which does leave it for a short time to absorb the carnot project far into the flask. To the end of bonic acid out of the rest of the apparatus. the tube which projects firom the flask, connect To remove the last traces of' carbonic acid the top of a bulb pipette, the other end of suck a little air through the apparatus. Then which passes to the bottom of a small two- detach the absorption apparatus, place it in necked Woulfe's bottle, containing not quite cold water, and allow it to stand in the balenough sulnphuric acid to fill the bulb of the ance case, as before, before weighing. The pipette. This Voulife bottle serves to dry the increase of' weight represents the carbonic gas, which is, however, tfirther dried by pass- acidt. instead of absorbing and weighing the iig' it through a U-tube containing purmice carbonic acid, it might be estimated fiomll the stone imoistened wkith sulphuric acid. To this loss, though less conveniently. (Chapman, U-tube is attached the absorption apparatus, Journal London C'lem. S'oc., 1867, 20. 227.) which consists of a pipette and WVoulfi bottle, As regards the quantity of material to be as before, but containing a solution of caustic taken, it may be said that Chapman operated potash; the second neck of the WToulfe bottle upon 0.5 to 0.8 grin. of matters like alcohol is connected with a set of Liebig's potash and butyric ether. The chromic solution conbulbs, followed by a small drying tube charged tained about 7 per cent of its weight of with lumps of caustic potash. The absorption bichromate of potassium. The ilixture of apparatus is of such size that the whole of' it organic matter and chromic solution was al CHROMIC ACID. 177 lowed to digest for severalihours] at the ordi- little more of the chloride of tin, and again naryjtemperature, in a sealed tube if need decant. RepeatS these operations until the were, and was afterwards heated for a few residue in the mortar is perfectly white. minutes to%100~'0before being transferred to Rinse the mortar with chlorbydric acid, add the generating flask. In the case of sub- some iodide of potassium and starch paste to stances heated ill sealed tubes, air must be the solution in the flask, and titrate with onedrawn through the liquid after it has been tenth normal bichroilate of potassium as placed inithe flask, in order to remove dis- above. On the addition of the iodide of posolved carbonic acid. tassium somne yellow iodide of lead will be B. Volumetric. Hempel has proposed to precipitated at first, but it will soon dissolve titrate chromates by means of a standard solu- again. Instead of a standard solution of stantion of oxalic acid. But according to Mohr nous chloride, 1.5 to 2 grins. of the double salt (Titrirmethode, 1855, 1. 240), the reaction be- of chloride of tin and chloride of ammoniurn tween the two substances is slow and incomn- may be weighed out and rubbed in the mortar plete, unless the solutions employed are with the chrome yellow and some chlllorhydric concentrated, and made strongly acid with acid (Mohr, loc. cit., p. 270). sulphuric acid. The value of the solution of To standardize the chloride of tin, in the oxalic acid employed has to be determined by first place, proceed as follows:- Fill a couple means of permanganate of potassium. of Mohr's burettes, one with the chloride of 4. Reduction of chro}mic acid by Stannous tin solution, and the other with a one-tentl Chloride. Weigh out a small quantity of the normal solution of bichlroniate of' potassium. chromate to be analyzed (0.3 to 0.5 grin. of Let 1 c.c. of' tin solution flow into a flask, add bichromate of potassium, for example), place to it some iodide of potassium and starch it in a flask, pour up)on it a measured quantity paste, and pour in the bichromate of' potasof a standard solution of protochloride of tin, siumn solution until the liquid is blue. The and add a Idrop or two of a solution of iodide object of this first trial is to enable the operaof potassium and a little starch paste. The tor to dilute the tin solution understandingly. chloride of tin solution is standardized as ex- It is well to dilute it to such an extent that plained below, and enoughb is taken that it each c. c. of it shall be of approxiimately the mnay be in slight excess as regards the chromic same value as a c. c. of the solution of the biacid. Shake the flask vigorously, and pour chromate. After this dilutionhas been effected into it from a burette a one-tenth normal the true standardizing begins. To this end solution of' biChroinate of Potassium until a run out 10 or 20 c. c. of' tlihe tin solution, add persistent tint of blue is visible throughout the the iodide of' potassium and starch, and then green liquid. - According to Mohr (Tit- the bichromate to blue coloration. Repeat the rirmelthode, 1855, 1. 268) no good results can operation a second time, with a quantity of be obtained by attempting to work directly the tin solution different fioom theft taken for upon the substance with the standard solution the first trial, or as many times as may be of stannous chloride. When such a solution necessary in order to obtain results which is poured fionl a burette into the solution of a agree closely. It is to be remembered that chroinate which has been acidulated with chlor- the standard of a tin solution is destroyed by hydric acid and treated with iodide of potas- diluting with water which contains air. (Mohr, sium and starch, the blue color of the iodide Titrirmethocle, 1855, 1. 257). of starch will disappear, it is true, but the 5. Reduction of chromic acid by NRitrous reaction proceeds so slowly that it is hard Acid. To estimate a nitrite in presence of a to determine the precise moment at which it is nitrate Tiebhborne (Chemical Nevws, 1865, 12. complete. The results of analyses made in 147) proceeds as follows: - In case the subthis way not only differ from those obtained stance to be examined is commnercial nitrite of by the process above recommlended, but they sodiull, which is usually contaminated with fill below the truth. For the influence of the carbonate and nitrate of' sodium, dissolve a oxygen dissolved in the water of the solutions weighed quantity of the substance in a tolerasee protoChloride of Tin. bly large quantity of water, and estimate the The method may be applied to the valuation carbonate of sodium with standard sulphurie of chromlie yellow (chromlate of' lead) as fol- acid (see Alkalimetry), taking care not to add lows: - Weigh out one or two grins. of the an excess of' the acid. To hit the precise chromle yellow, place it in a mortar together point of' neutrality drops of the liquid lmay be with some strong clorhydric acid, rub the imix- placed upon litmus paper, and the latter alture with tlhe pestle, aind allow a standard solu- lowed to become d(ry before each new addition tion of stannous chloride to flow upon it firom a of' the acid; or a mixture of iodide of' potasburette, until the yellow color of' the chromate siumn and starch paste may be employed as the has been completely changed to the green of indicator, since a drop of the nitrite will chloride of chromium. As soon as most of not color the mixture blue until all thle carthe chloride of' lead has settled, decant the bonate of sodiumi has been neutralized. In supernatant liquid into a flask or beaker, rub tile next place weigh out 3 ginsl of' pure bithe residue again with chlorhydric acid and a chrolmate of potassium for every 2 grins. of' 12 178 CHROMIC ACID, the nitrite taken, dissolve it in some water in a dish into a flask of 250 c. c. capacity, and well stopperell bottle, ad(d ain excess of sul- heat the liquid for half' an hour, or an hour, phuric acid to tie mixture. and cool the flask upon a sand bath. Then add as much carin a freezing mixture of Glauber's salt and bonate of' lead to the solution as may be muriatic acid. Cool the nitrite solution in a needed to fr'ee it froom sulphur, cool the consimilar way, and pour it carefully into the tents of the flask by placing it in water, fill it chromic acid bottle in such a way that it shall with water to the mark, and shake it vigorfloat above the chronmic acid without mixing ously. Throw the mixture into a filter and with it to any great extent. Then close the collect the filtrate in a dry glass. There will bottle, remove it froin the. freezing mixture, be obtained 230 or 240 c. c. of' a liquid, every twirl it around, and let it stand so as to ac- 50 c. c. of which correspond nearly enough to quire the temperature of the room. In the 2 grnms. of the dry substance taken. To 50 course of froml half an hour to an hour the c. c. of this filtrate add 300 c. c. of cold wareaction will be conmplete. The nitrous acid ter decidedly acidulated with sulphuric acid, will have reduced its equivalent of chromic but not with chlllorhydric acid, and proceed to acid, and by collecting and weighing the ses- estimate the ferrocyanide of' potassium by quioxide of chromium which has been formed, means of a standard solution of ehromic acid, the amount of nitrite of' sodium in the sample the value of which has been previously decan be estimated. See Hydrate of Chromiunm termnined against pure ferrocyanide of' pofor the precautions to be observed in presence tassium. - The chronic acid solution should of' chromlic acid. be of' such strength that 100 c. c. of it repro6, Red-ction of chromic acid by Ferrocy- sent 2 grins. of' ferrocyanide of potassium. ani(le of Potassiuns. The oxildation of the ferrocyanide proceeds A. To estimate chromic acid, dissolve froim rapidly, and is known to be complete when a 0.3 to 0.7 gr'in. of the chromate to be anal- drop of' the liquid touched to a drop of ferric!yzed( in water, acidulate with ehlorhydric chloride on a white plate no longer gives a acid, d(ilute with water to about 150 c. c., and green or blue, but a reddish-brown coloration. pour into the solution fronm a burette a stand- It is essential to success that oxidizable matald solution of ferrocyanide of potassiumn, until ters, such as sulphide of potassium, etc., be the whole of the chronic acid has been re- removed from the solution before adding the duced, and the ferrocyanide just shows itself chromic acid. But by operating in very dilute to be ii excess. The standard solution may solutions and at a low temperature, the action be prepared by dissolving 40 grins. of ferro- of' cyanides andl sulphocyanides upon the cyanide of' potassium in water to the volume chromlic solution lay be avoided. In concenlof' a litre; and, the completion of the reactionl trated and strongly acid solutions the sulphois indicated when a drop of' the chrlome solu- cyanides present in the crude ferrocyanide of tion touched to a drop of' a decidedly acid potassium would reduce some of the chromnic solution of' f'rrie eichloride upon a white porce- acid. In alkaline solutions the oxidation is lain plate, colors it greenisll. A green point is found to be irregular. The process is rapid, fi'rst seen at the edge of' the drop, and quickly and yields sufficiently accurate results (E. increases. Since somne experience is required Meyer, Zeitsch. analyt. Ch/em., 1869, 8. 50t). in order to appreciate readily this final react- 7. Reduction of chromic acid by Iodide of tion, it is well to weighl out two equal quanti- Potassium. A description of the atteiiipts of' ties of rmaterial for each analysis, and to Zulkowskyto estimate chromic acid by adding employ one of' the quantities for obtaining iodide of' potassium, to the acid solution, letan approxiumative result. Almost enough of' ting the mixture stand during half' an hour or the ferrocyanide solution to reduce the whole an hour, and then titrating the io(line wthicl of the chromllic acid mnay then be added at has been' set fiee with a standard solution of once to the second sample, and the test then hyposulphite of' sodium, will be found in Jozon. applied methodically after the alddition of each ]yratct. UChel., 103. 351, and Zeitsch. analyt. c. c. of' the standard liquor until the p:oper Chemr., 1869, 8. 74. The process is not yet green tinge appears in the ferric chloride. perfected. The reaction between chromic acid and ferro- 8. Reduction of chromic acid by Chloride of cyanide of' potassiulll may be represented by Atnmoaiiun. See Chromate of Ammlonium, the following equation: — instability of. CrO3 + 3K4FeCys + GC1 = 3I(3FeCy. + CrC13 + 3KC1 + 3H20. 9. Reduction of chromic acidl by Sulphurous (Rube, Jou1n. prakt. Choem., 95. 53). Acid, Sulplhureted IHydrogen aCld A lcohol. InB. For estimactilg the alue of crude,erro- stead of employing chlorhydrlic acid alone, as cyanide of potassium, and the fused imass firom in Method 1, for reducing chliromlic aciOd as a which it is made, gind up a samlple of' the preliminary to the precipitation of hydrclte of' fused cake, weigh out ten grins. of the fine, chromrium, the reduction lmay be effeetel cithller sifted powder, place it in a dish and boil it in by heating the solution of' the chromnite with a about, but no less than, 150 c c. of water, mixture of' chlorhydriic acid and alcohol, or by together with solne recently precipitated fer- acidulating the solution of' the chroimate with rous carbonate. Wash the contents of the chlorhydric, acid, and passing sulphuretted CHROMIC ACID. 179 hydrogen through the mixture, or by adding a solved in water and acidulated with sulphuric strong solution of sulphurous ac'id and heat- acid. The completion of the pro1(ocess is in. ing the mixture gently..Accord(ing to Genth dicated eithller by the chlanme ot col)lr, or by (Chemnical News, 1862, p. 32), it is best to erm- the appearance a.ltdl disappearihcie eof the blue ploy the sulphurous acid in alkaline solution. reaction on the adrlition of a uIlixtre of iodide Instead, therefore, of acidulating with chlor- of' potassium and starchi paste. BIt tthe rehydric acid before addinlg the sulphurous acid, sults obtained in this wax br O'Neill have an excess of sulphulrous acid should first be been shown to be erroneous by G enth (Clemiadded to the solution of the chromuate. The cal News, 1862, p. 32) an(d hby Oudlesluys mixture should then be carefhlly heated to (Ibid, p. 254); the amount of (hrimolullm found boiling, a slight excess of ammonia added to being mnuch belowv the trutll. F'Iesenius it, and, the boiling continued for several irin- (Zeitsch. anal?/t. Cheim., 1862, 1. 5)0) his reutes. The reduction will be far more rapid mlarked that the process of' )'Neill is mnaniand complete than if tlme solution hadl been fiestly bad in view of' tlle obselvations of left acid. For a dry chromlate, or for the Lenssen: & Lmwienthal. These cheiiiists liave highly concentrated solutiotn of' a chromatej shown that it is true of siltlhurous acivd as it clhlorhydric acid is the best reducing agent, as is of protoChloride of'in, that when mixed in Method 1. For tolera.bly strong solutions with even a smI-all quantity of' chromic acid a mixture of chlorhdllric acid and alcohol (or with permanganate of potassiunl) in priesmay be used, or, perhaps better, the solution eice of water, the oxygen dlissolved in the may be evaporated somewhiat, and then treated latter suddenly becomes active, ailtl converts with chlorhllydric acid alone. To decomlpose an equivalent (luantitS of tlfe lsulllurous acid chromate of' lead, a mixture of strong alcohol into sullphuric acid; and( this. in spite of tlhe and concentrated clhlorlhvdric acid may be fact that chromic acid can only liy conipletelv emnployed. and the Chloridle of' Lead collected decomposed by sulphurous acil wxhein-the litand weighed ill case the substance to be ter is largely in ei. -ess. Even when there is analyzed contain no other insoluble matter. much iodhydric acid'n the mlixture of chroinic Native clhromliate of' lead must be very finely and sulpl;unrous acid:, the dissolved oxygen powdered or elutriated in order that it may be still becomes active, lot chliomnic acid is,not completely reduced, For dilute solutions, the deconlposed by iodhydlric acid when sulphu — use of' sulphuretted hydrogen or sulphurous rous acid is present, except after long stan d acid is to be reconmmlended. The method by ing. But by comnpletely decomposing the sulphuretted hydrogen often comes into play chromic acid solutionl with strong iodhydric in the separation of chrolnium friom the heavy acid in the first place, it canl be afterwalrds metals iwhich form insoluble sulphides; sul- correctly titrated with sulplhuous acid. (Lensphuretted hydrogen is passed into the acidlu- sen & Lmwenthal, Joarn. pr'(at. C'hem., 1862, lated mixed solution, either at once or after 86. pp. 194, 209). the chromnic acid has been reduced with sul- 10. Reduction of chlro10 iC acidl hy orgalnic phurous acid. Wherl sulphuretted hydrogen Coloring Miatters. See biChromiate of' Potasalone is employed as the reducing' agent, the sum. acid liquid suiersaturated with the sulphu- Principle II. Decomposition of by hieat. rettedl hydrogen Imust be allowed to stan(l in a Ap)plication. Analysis of' conmpoi(nds of moderately warnm place umltil the sulphur which chromuic acid and sesquioxide of chromium, is set free has colmpletely subsided. Accord- and of' other hydrated nietallic chrolll'tes. ing to H. Rose, the reduction by means of Mlethod. Place a weighed (uanlltity ofi the sulphuretted hydrogen, though less rapid than hvlrated chromlate to be analyzedll in a vweighed that by sulphurous acid, is to be preferred on bulb tube of hard gliss, coeillcet a i\vilhed the whole, since in presence of' sulphurous chloride of calcium tube wvith the bulb tube, acid hydl'ate of chromliumr is somlewvlat diffi- pass a current of' dry air tlhrlough the apparacultly 1)recipitable by anmmonia. lWhen alco- tus, heat the bulb tube caUtiousli till all the hol is usedl, the excess of' it, and the products water has been expelled f'oml the chromrate of' its dlecomllposition, must be expelled fromll and absolrbed by the wveirhed lchloritde of cfilthe liquid bebre the liydrate of' chronmiumii can ciumn tube, anid finally hleat the brulb tube to be precipitated with ammonia.'l'he use of (lull redlless to deco(lpose tilhe last triaces of sulphlurous af(id, as above, is common in the chromic acid. The loss of wexiglt of tlhe builb analdsis of chromiie-iron ore. It is noteworthy tube represents the sum of the weights of wathat chromic acid is not reduced by hyposul- ter aiid oxyge whichli have been expelled; phite of' sodium. the gain in weight of the chloridie of calcium A volulietric process of estimating chromic tube gives the water, and thel (iiffcrence beacid by mieans of' a standard solution of sul- tween the weight of water and oxygen andt phite of sodium has been described by O'Neill the weight of the' water will give tbe o(xygen. (Chemlical IVews, 1862, p. 199). The value Every three equivalents of' oxySgen oundc corof the sulphite solution is detelrmined before respond to two equivalents of chronic acid. each series of' analyses by titrating a weighed The sesquioxide of chromliunl left in the bulb quantity of pure bichromate of potassium dis- tube ilay be collected and weiglled in case of 180 CHROMATE OF AMMONIUM. need. The process is well adapted for According to Richards (American Journ. the analysis of hydrated precipitates and basic Sci., 1869, 48. 200), chromate of barium, salts, which from being partially soluble in though soluble to an appreciable extent in water cannot be washed, but have to be pre- pure water, is insoluble in tolerably strong pared for analysis by pressure between folds saline solutions, even in presence of acetic acid. of filter paper. The saline matters which re- On the other hand chromate of barium, like sult from mother liquor left adhering to the the sulphate, is liable to drag down chloride of precipitate, are finally washed away from the barium and nitrate of bariumn, and conseresidue left in the bulb tube after ignition, and quently requires to be thoroughly washed. their weight is thus determined and allowed The washing should be effected by means of for. (Vogel, Journ. prakt. Chrem., 1859. 77. some saline solution competent to dissolve out 484; Storer & Eliot, Proceedings American the contaminating salts without acting upon Academy, 1861, 5. 197.) the chromate. Chromate of Ammonium. According to A. H. Pearson (American~ Princzple. Instability of the salt when Journ. Sci., 1869, 48. 198), a solution of heated. acetate of aminonium may be employed with Applications. Separation of Na, K, Ba, Sr, advantage in the sense indicated by Richards.'Ca, Mg and Cr, ftom chromic acid; analysis Pearson proceeds as follows: - The mixed soof chromate of ammonium. lution of chromic acid and magnesium, for M3ethod. Mix. the finely powdered, dry example, which may contain much saline matchromate with 4 or 5 times its weight of dry, ter resulting from chlorate of potassium and powdered chloride of ammlonium in a porcelain nitric acid used for oxidizing the chromiulm, is crucible, and heat the mixture cautiously un- diluted with water, a little over neutralized with til the whole of the chloride of ammonium is ammnnonia, and then treated with enough acetic expelled. The residue will contain insoluble acid to make it slightly acid. After the sesquioxide of chromium and soluble chlorides acidulated solution has become cold, a soluof the metals enumerated (Bahr, Journ. prakt. tion of chloride of barium is added to it in Chem., 60. 60). A single ignition with the slight excess, and the mixture left at rest for chloride of ammonium is usually sufficient to 10 or 12 hours. The clear supernatant liquor decompose the chromate completely, but it is is then decanted into a filter, the precipitate is well, after having weighed the residue, to re- washed by decantation with a cold solution of ignite it with a fresh quantity of chloride of acetate of ammonium, — prepared just preammoniuml, and observe whether the second vious to use, if need be, by addiig acetic acid residue has the same weight as the first..~, to diluted ammonia water, - and finally transFor the analysis of chromate of' ammonium ferred to the filter, rinsed with water, dried, it will be sufficient to ignite a weighed quan- and heated in a crucible to expel the last tity of' the salt, and weigh the residual ses- traces of water and of the ammonium salt. quioxide of chromium. To separate sesqui- The mixture of precipitate and liquid lust be oxide of chromium from chromic acid, ignite allowed to stand several hours before filtering, one portion of the substance with chloride of lest some of the chromate pass through the ammoniuml, and determine the total chroliullm, pores of the filter and render the filtrate and in another portion estimate the Chromic -cloudy. Acid by some one of the methods given under B. Gibbs'(American Journal of Science, that head. 1861, 39. 58) directs that the alkaline solution, Chromate of Barlurm. in which chronic acid is to be estimated, be Principle 1. Insolubility in water and in neutralized with acetic acid and then mixed saline solutions. with a slight excess of acetate of barium. In Applicationls. Separation of Cr from Mg, case sulphate and chromate of barium be Al, Fe, Co, Ni, Mn and Zn (,Methods A and thrown down together, the chromic acid may B). Separation of Ca, Ba and Sr (Milethod be reduced by boiling with chlorhydric acid C). Volumetric estimation of S03 (Method and alcohol, and the sulphuric acid and oxide D). of chromium subsequently separated in the Mliethocls. In case the chromiuml is not al- usual way. ready in the form of' chromic acid, convert it C. For separating Ba, Ca and Sr', Fleischer to that state by some one of the methods of (Chemical News, 1869, 19. 290) precipitates oxidation described under Oxide of Chromium. the three metals together as carbonates (see Then proceed as filiows: — Carbonate of' Calcium), anld weighs the dry A. Neutralize the solution exactly, add a mixed precipitate. He then dissolves the piesolution of nitrate of barium and let the precipi- cipitate in an excess of standard chlorhydric tate settle, then collect, wash, dry and weigh it acid, dilutes with water, heats to expel carafter gentle ignition. The common impression bonic acid, as explained under Acidimnetry, that it is better to throw down chronmic acid in and titrates the excess of acid with onle-half the form of cllhromate of lead rather than in normal ammonia water to determine how much that of chromate of barium is incorrect (H. of the acid has been neutralized by the mixed Rose). carbonates. The neutralized solution is then CHROMATE OF BARIUM. 181 mixed with bichromate of potassium solution ride of barium. The process is easy and and an excess of ammonia water, the precipitate rapid and yields satisfactory results for technicollected and cashed and the amount of chro- cal purposes. mate of barium contained in it is determined Principle II. Decomposition of by alkalihe volumetrically by means of ferrous sulphate, carbonates. as described under Chromic Ac'id. The Applications. Separation of Ba from CrO3. amounts of calcium and Strontium in the mix- 3etlhod. Boil the finely divided chromate ture may then be calculated fiom the weight with the solution of an alkaline carbonate, of the mixed carbonates and the amount of pour off the liquid and boil the residue a secstandard acid expended, after subtracting that ond time with a fresh quantity of the alkaline which was neutralized by the carbonate of solution. Filter off the insoluble Carbonate of barium. Barium, neutralize the filtrate with nitric acid D. For estinmating Sulphuric Acid, Wilden- and throw down the chromic acid as Chromate stein (Zeitsch. analyt. Chemn., 1862, 1. 323) of -Mercury. Two consecutive boilings are proceeds as follows:-Put the substance to be sufficient to completely decompose chromate of analyzed in a ishort-necked flask of about 200 barium, and change it to Carbonate of Barium c. c. capacitv, dissolve it in from 45 to 55 c. c. and chromate of the alkali. But with a single of water, heat the liquid to boiling and allow boiling the dlecomposition is incomplete, for a standlard solution of chloride of barium (1 when mixed with any considerable quantity of c. c. equal about 0.015 grin. SO3) to flow into a chromnate of an alkali the solution of the the flask fiom a burette, until all the sulphuric alkaline carbonate ceases to act upon chroacid Fhas been ~precipitated; then boil for a mate of barium. - The decomposition of minute or a minute anl'a half. Take care al- the chromate of barium might be effected at ways not to add any great excess of the chlo- the ordinary temperature, but the operation ride of barium over and above what is actually would require a long time and repeated pourneeded to precipitate the sulphuric acid. ing away and renewal of the alkaline liquid. Next add, in case the solution is acid, enough It is to be observed that carbonate of barium dilute ammonia water to a little more than nlay be completely changed to chromate of baneutralize the liquid, and to the still boiling rium, even at the ordinary temperature, by mixture, no matter whether it be clear or means of a solution of normal chromate of pocloudy, pour in from a burette a standard solu- tassium. By fusion with an alkaline tion of neutral chromate of potassium until carbonate (see Chronmate of Sodium)- the dethe excess of chloride of barium is all thrown composition of chromate of barium is far less down. _-. The solution of chromate of po- complete than by the wet method above tassium should be of such strength that 1 c. c. described. of it is equal to about 0.01 grm. of sulphuric Properties. Precipitated chromate of baacid; it should be added by half c. c. to the riuin is of a light lemon-yellow color, slightly solution under examination until the superna- soluble in water, but as good as insoluble in tant liquid in the flask shows a distinct yellow various saline solutions, as has been stated color. No special indicator is needed to show above. It dissolves readily in the mineral when the titration is finished, since the preva- acids, but not in acetic acid. It is not preciplence of the yellow color of the neutral chro- itated from solutions containing citrate of iate of potassium is of itself sufficient to sodium. It is somewhat more readily (lecommark the completion of the process. Even posed than sulphate of' barium by boiling after the addition of the first half c. c. of the solutions of the alkaline carbonates. The chromate of potassium the liquid will become composition of chromate of barium is:clear enough, after a little shaking, to show Ba. 153.. 3.5oi Croa.. i00.s. a.c5 whether it is colorless, provided no great ex- C cess of chloride of barium is present, and as 253.5 100.0() successive portions of the chromate of' potas- Chromate of Bismuth. sium are added the liquid clears itself more Principle. Insolubility in water. and more readily, so that there is no difficulty Applications. Estimation of Bi in all comin determining when the process is finished, pounds of that metal which dissolve in nitric and but a few minutes are needed for the ti- acid to form nitrate of bismuth, provided no tration. - To make assurance doubly sure substance which, like citric acid, prevents the single drops of the standard solution of chlo- precipitation, be present. Separation of Bi ride of barium may be dropped into the now from Cd. clear liquid, which has been made yellow by Method. The solution to be analyzed addition of chromate of potassium, until it be- must be as nearly neutral as possible. Hence comes colorless. Usually a very few drops in case it contains much free nitric acid will accomplish this result, and at the most no evaporate it upon a water bath until the excess more than 0.3 c. c. will be required. Begin- of acid is expelled. Then pour it into a warm ners not yet acquainted with the process may solution of bichromate of potassium contained' filter the yellow liquid before proceeding to in a p 1rcelain dish, taking care to stir the mixmake it colorless by adding the drops of chlo- ture and to have the chromate of potassium 182 CHROM ATES. slightli) in exc.ess, Use water acidulated with Chromate of Copper. liitriic acid to w ash out the dish that contained -'iintcpie. Oxidizimg power of. tie bismluth solution. Boil thle contents of Application. IEstimnation of sulphur in orthle dish ifor tetl llminutes with stirring; then ganic compounds. decant the superiilaait liquid into a weighed Melheod. T'he substance to lbe analyzed filter and wash thle i lre ipitate in the dish by and thlle chroinate of' copper are mixed in boiling it repeatedly with fi esh portions of the orclinar v way th a combustion tube of water, and decantiin the liquid ito the filter. hard glass, and the ignition is conducted in After awvlile tranlsler tle precipitat.e to the fil- the usual uianner, a, described under Carbon. ter, wash it thoreoligly with boiling water, dry The precautions to be observed are that an at about 112' atld weigh. In the case of abuddlnnce of the cllhromate of copper is mixed separating bismutht from cadmium tile filtrate with the sulbstance to be analyzed; that the filoml the chrouiate of' bisllth is concentrated combustion is etlected in a large and capacious by evapora!ii, n auind thle cadmiumi precipitate d tube, so thllt a wide channel ilay be left above as Carbonate of' Cadmium. i - The p reipi- tLe mixture; that the combustion be proceeded tate which forins when the bismuth solution is witl very — slowly, and that the anterior part of added to the bichroniate should be orag(e- the tube is kept at a temperature lower than yellow colored arnd dense throughout. If' it is that at which sulphuric acid can be expelled fiocculent and hias the color of yolk of egg fiomn sulphllate of' copper. The reaction bethat is a sin- thiat tpo little clhromate of p.otaS- twe(en the cli cmroaite and the organic substance siulm has belcn usedt. In that event add SOmle nmay easily be violent enoughl to project matter more of' the bichllcnate. and boil the mixture fioml the tube, unless care be taken to rmoderuntil the uprecipitate h as the proper appear- ate it. - Wlhen tlie combustion has ceased ance. Cale lt1l'st, Lalways be taken, however, treat the contenlts of the tube, which consist of to avoid adding too nlnch of the bichromnate.. a mlixture of the oxides of copper, and of The process yiells very satisfhctory results. clroniunl, and chrollate and sulphate of cop(Lcewe, Jonttr.,l' p/ITkt.,C/;eu., 7. 46'4) per, with stlronll cllorhydrie acid, add some Accordiilg to Fresenius the volumetric alcohol and hleat the m-nixture in order to remethod of' Peatrson (PIhil. lla.q. (4.), duce thle chliolnic acid to oxide of chromium. 204), depending on th'e principle iny question, When the liquid exhibits a pure green color, is not to b'e comiimiendedl since it is bas'ed t pon filter it, and ja tie hot filtrate throv doiwn the the mnistaken assumlption that chrolIla te of' bis- sulphuric acid as Sulplhate of' Barium (Otto, mnuth is insoluble in dilute niitric acid, while, Zeitsch. analyt. Chem., 1868, 7. 117). in f:act, it is only i nsolub.e inl that liquid whel According' to Otto, the inerits of the promnixedl with a esufnll-elt excess of clirolll.ate of cess consist in tle large proportion of' active potasiuim. oxygen contained in the chromate, whence a Properties. Tie precipitate pro4ucewd by coilparatively small quantity of it will effect a adding bichrlolnate of potassium in slight. ex-` quicker. and more coinplete oxidation than cess to a nleutral solution of' nitrate of' bisnmuth can be obtained with a mlixture of saltpetre is a dense uranoge-yeliow powder which settles and carbonate of sodium; that the glass tube readily. It is insoluble in water, even ixn pres- is lot acted up.on; that the contents of the ence 6f some fir e chinroimic acid; but is soluble tube can consequeintly be easily discharged, in chlorlvldricl and nlitric acids. It ilay be and that there is no nit'ate of barium, or, at tried at 1I0~-1130 without alteration (I,cwe). the lmost, a faint trace, to go (own with the It is not prlecipitatedl fiom solutions which sulphate. The enltire proces can be finished contain citrate of sodiuml (Spiller). Contrary in a or 4 hours. - To prepare the chroto the statement of pearson, thle forulal of' tle nate of' copler precipitate pure nitrate of precipitate is Bl 2, 2 CiO0 [-Not Bi9,O, copper with pure chromate of' potassiuni, and Cr0)3]. (Lcewe anld IFrresenius). ['Li c'I- wa'sh the pinccipitate 3 or 4 times with water, position of thre lry precipitate is:= to remllove 110ost of the nitrate of potassium. io,03, 4658 Q. 5. Loger washinig would remove some of' the ^. 0. 201 8.05.,chlronii,c acid, andc make the salt more and 9 i.00. mel'e basic. ~ChromateiS~%e of Ca8c~umn ~ Chromate of Lead. Pirolmate D.of Co a. i., f b I cli/Re e I. Insolubili/ty in water aciduPrinciple. Deiomposition of by alkaline lated witfh acetic acid, and'fixity at 100, Applications. Estimation of JPb in those Appication,. Separationl of 4C3a fiom CrO3. compounds of that mnetal which are soluble in 1Method. See Chromate of Barium. One nit ide ptil such ascontain single boiling witlh the alkaline carbonate will * I n ngrle boiling withi the alitlin carbonat. will substanes like citric acid, which prevent the be sufficient to completely ecomnpose, ch ro prmp i'itation. Estimation of chromic acid. mate of' calcium (UH. Rose). Separation of chlromic acid frojn Ca, Sr, Mg Chromatle of Chromiu. andt SO3. E0 stimation of' sulphuric acid in Principle. Decomposition of' by heat. ee slulphates, and of' plosphoric acid in phlosChromrlic Acid, decomposition of b),y Jwt. phates,-l!so in;anlurese urine1 etc. CHROMATE OF LEAD. 183 Mlethodl 1. To estimate Leadl proceed as fol- A distinct red coloration, due to chromate of lows:- silver, will appear as soon as a small excess of A. Grravimetric. If the solution to be ex- the bichronmate has been added to the lead soamined is not already distinctly acid make it lution. Any particles of chromate of' lead so with acetic acil; then add bichromate of which may be brought into the drop of nitrate potassium in excess, and if' free nitric acid has of silver remain suspended there without re-been present add enough acetate of' sodium to acting upon the silver. 0.1 c. c. of the biclroremove the fiee nitric acid, and replace it with imate solution used should be deducted as an free acetic acid. Let the mixture stand in a allowvance for the excess. Unless a sufficient warmi place to settle; c ollect the precipitate quantity of acetate of sodium be present the liqon a weighed filtel'; wash with cold water, uid willbecomele ellow colored, througll excess dry at 1000. and weigh. Or the precipitate of' bichromate, before the reaction with silver may be collected on an unweighed filter, and is obtained. In that event add some more aceignited at a low heat in a porcelain crucible, if' tate of sodium and 1 c. c. of a standard solution care be taken to remove the powder corn- of lead containing 0.0207 grin. of lead in 1 c. pletely from the paper, and to burnr the latter c. Complete tie plrocess in tile usual way, and by itself'I'he proctess yields accurate results, deduct another c. c. from tlhe amount of bibut, according to HI. Rose, in view of better chromate used, as an allowance t'fo the lead processes, there are comparatively few cases added. All metals whose chroliltes are' insolin whicth it can be used with advantage. uble must be remlove(l before the method can Instead of' drying and weillhinrg thle washed be employed. If' iron be present it mnust be in precipitate as above, S'chwarz (Aalnle C('hem,. the form of a ferric salt (Schwarz, Dingler's ud P/haran., 84. 92) treats it with chlorhydric polytech. Journ., 169. 284). acid and a measured quantity (an excess) of' a C.'To estidmte Sulplhuric Aciel. Besides solution of ferrous chloride of' known strength. the one-tenth normal solution of' bichromate of Sesquichloride of' chromium, chloride of' lead potassium described in B, prepare a twoand ferric chloride are fornmed. The mixture tenths normal solution of nitrate of lead (33.1 is filtered( to remove the chloride of lead, and grin. to the litre). Mix the solution of the the excess of ferrous chloride is determined in sulphate to be tested with a measured quantity the filtrate by means of' pernmanganate of' po- of' the stan(lalrd lead solution, taking care that tassiurl, as explained under Chrolnic Acid (re- a small excess of lead shall remlain unprecipiduction of' by a feirrous salt), or in some other tated. Collect the sulphate of lead upon a appropriate way. - The difference between filter and wash it. Mix the filtrate with acethe amount of' iron taken and that ibolnd in tate of' sodiuln, and titrate the lead with the the filtrate gives the quantity which has been standard solution of' bichroniate, as in B. oxidized by the chromate of lead, and every Each c. c. of the lead solution lvhich was exthree equivalents of' iron thus oxidized corres- pended in precipitating sulp)huric acid reprepond to one equivalent of' lead. Tle process, sents 0.008 grins. of sulphuric acid. The though complicated and ra'rely applicable, process yields satisfactory iresults, thoufgh they yields tolerably accutate results. Mohr (Tit- are naturally a trifle too low in view of' the rirmethode, 1855, 1. 199 and 2. 107) has solubility of' sulphate of' lead. The presence mlade some slight, and, as it seems, ill-founded of' salts like acetate and nitrate of' ammoniiumn, objections to the process, but later experi- which increase the solubility of sulphate of mnlets of Fresenius ha8ve shown it to be exact. lead, must of course be avoided as f:ir as mnay Compare Chromic Acid, reductior of' by fer- be possible. - Instead of filtering the sulrous salts. phate of' lead, the mnixture of' liquid and precipB. Volumetric.' Add ammonia or carbonate lte e may be allowed to settle in a graduated of sodiumn to thle nitlmic acid solution of' the cylinder, and a porition of the clear liquid lead as long as the precipitate re(lissolves on taken out with a pipette for analysis, without shaking. Add a solution of acetate of' sodium any great sacrifice of accuracy. Calcium and in not too small quantity, and pour into the several other metals which would interfere with solution firom a burette a one-tenth normal so- the process may be separated'wvith carbonate lution of bicbromate of potassium (containing of' anmmonium. Chlolrhydric acid must be got 14.73 grins. to the litre) till the precipitate be- rid of by evaporating with an excess of' nitric gins to settle rapidly. Tlen place a number acid on a water bath, for in a concentrate(d soof drops of a neutral solution of' nitrate of' sil- lution some chloride of' lead would go down ver on a porcelain pllate, and proceed more with the sulphate. - If phosphoric or arcautiously with the addition of' the bicllroinate, senic acids are present the process becomes adding onlly 2 or 3 drops at a time, and stir- less siimple, but it is still possible to enmploy it rinlg thoroughly after each addition. A few by first precipitaiting the sulphuric acid with the seconds after each new addition of' the bichro- lead solution,firom a nitric acid solution; then, mate, as soon as the precipitate has settled, so after filtration and addition of' acetate of soas to leave a tolerablyl clear li luid, take up a diuln, the phosphoric or arsenic acids as phosdlop of' the liquid a.nd touch it to one of the phate or arseniate of lead. The excess of drops of nitrate of' silver on the white plate. lead is then determined in the last filtrate;.the 184 CHROMATE OF LEAD. phosphate or arseniate of lead is dissolved in ation, since a small proportion of the prenitric acidl; the solution is mixed with a great cipitate remains dissolved in the excess of excess of bichromate of potassium, and the carbonate of sodiuln, and the proportion thus precipitated chrolnate of' lead collected and ti- dissolved increases with the amount of the cartrated with ferrous chloride, as in A. bonate of sodium. 1For estimating phosphoric To separate sulphuric from chromic acid the acid in urine the titration should be prelatter may either be reduced with sulphuretted ceded with a precipitation by chloride of calhydrogen, at the risk of converting a little of cium and carbonate of sodium. The process the latter into sulphuric acid, or the two acids is said to Aield very satisfactory results may be precipitated together with the lead so- (Schwarz, Dinglier's 1polytech. Joursn., 169. lution, and the chroimic acid estimated in the 294). precipitate, or in another portion of the or- Instead of the two-tenths normal solution of iginal substance (Schwarz, Dingler's polytech. lead employed by Schwarz, IMohr (Zeitsch. Journ., 169. 289). analyt. Chem., 1863, 2. 253) recommends a D. To estimate Phosphoric Acid. The three-tenths normal solution (49.671 grins. to same standard solutions are needed as in C, the litre), and enjoins that care be taken not and the operations are similar in principle to to add any too great excess of' it to the soluthose (lescribed in C. An aqueous solution of tion of the phosphates. - According to the phosphate of' an alkali imetal, or a nitric Miohr, the process is almost absolutely correct acid solution of the phosphate of an alkaline when neutral solutions are operated upon, but earth is mixed with an excess of the lead solu- is less exact, thoughi still exceedingly valuable tion, and then with an excess of acetate of so- for technical purposes, when the liquid is acid, (liuni. Triphosplhate of lead (3 PbO, P20O) as when the phosphate of an alkaline earth is goes down as a flocculent precipitate, which, dissolved in acetic acid. The trouble lies in after havinl been allowed to settle, is col- the fact that the indicator (see Chromate of lected upon porous filter paper and washed. Silver) is less delicate in the presence of acetic The excess of lead is then determined in the acid than it is in aqueous solutions. It is of filtrate, as in C. For each c. c. of the two- the first importance, therefore, to have as littenths normal lead solution 0.004733 grms. of tle free acetic acid as possible in the liquid to phosphoric acid may be allowed (i. e., two- be titrated, and to keep the volume of the liqthirds of' 0.0071). The processes of filtering uid as small as possible. - For the estimaand washing are not so easy as they are with tion of phosphoric acid in urine Mohr adds the sulphate of lead of' Method C. But by magnesia mixture to the liquid, collects and warming the mixture it is possible to make the washes the Phosphate of Magnesium and Amprecipitated phosphate somewhatmiore oompact, molniunm and dissolves it in acetic acid before after which op)eration it is well to bring the proceeding with the titration. mixture to a (efinite volumse, and to take out MIethod 2. To estimate Chromic Aci(d mix a portion of it with a pipette for analysis, the solution with acetate of sodium in excess, either before or after filteringr through a dry add acetic acid to strong acid reaction and filter..Accordiing to Mohr, the liquid must finally a solution of acetate of' lead as long as always be absolutely fiee,firom suspended par- any precipitate falls. Collect and weigh ticles of phlosphate of leald, for this salt would the prlecipitate as in Method 1. The restlts be decomposed by the solution of bichromate. are accurate. The presence of' calcium dloes no harmn. If Prqapcrlies. Chromate of lead is a bright iron or aluminum c: be preslent they will be yellow pr ecipitate, insoluble in water and thrown downl as pilhospIhates when acetate of acetic acid, an(l but little soluble in other disodium is akdded to the solution, and must lute acids. It is as good as insoluble in a be separatesld by filtration. It the precipitate dilute solution of acetate and nitrate of aminocontains no other metal than iron the amount nium, slightly acidulated with acetic acid. For of the latter llay be determined, in most cases Brown's experinents on its solubility in niand 1 equivalenlt of P2 0s allowed for each tric acid see Dictionary of' Solubilities. It equivalent of Fe203 fbound. Phosphate of iron is readily decomposed by hot chlorhydric acid, cannot be d.composed( by nitrate of lead, but and dissolves easily in hot oil of' vitriol and in the phosphoric acid can easily be separated1 caustic alkalies. - According to Mohr firom it by means of rnagnesia. - In case (Titrirmetlhode 855, 5, 1. 199). chroImate of sulphate of calcium, or imagnesium, or a large lead may be completely precipitated friom a proportion of' chlorides are present in tile solution of nitrate of lead, even vlen the latmixture to be analyzed, the solution may ter is rather strongly acidulated with nitric or be treated at the temperature of boiling wvith chlorhydric acid, provided a distinct excess of carbonate of' sodium, and the mixed precipi- bichromate of potassium be added to the acid tate of carbonate and phosphate of magnesium liquid. It appears that, altllough chromate of and calcium may be dissolved in nitric or lead by itself is decomlposed( and dissolved to acetic acid for the analysis, after the sulphate a certain extent by strongr nitric and chlorhyand chloride of sodium have been washed out of dric acids, this action cannot occur in presence it. home phosphoric acid is lost in theoper- of an excess of chroamate of potassiulm. It CHROMATE OF MERCURY. 185 would seem as if the excess of acid went to Principle. Insolubility in water. combine with the potassium of the bichromate, Applications. Estimation of chromic acid. and as if chromate of lead were insoluble in Separation of chromic acid from Na, K, Ca, chromic acid. Chromate of lead dries thor- Sr, Mg and Cr. oughly at 100~; it is permanent in the air, Method. Make the cold solution very and suffers no change when heated to temper- slightly acid with nitric acid, so that it may atures lower than its melting point, excepting redden litmus paper only very feebly, and add that when hot it exhibits a reddish brown a solution of mercurous nitrate as long as any color. It fuses at a red heat, and at higher precipitate falls. Then carefully add a few temperatures it gives off oxygen and is re- drops of ammonia water until the precipitate duinced to a basic chromate of lead, mixed turns slightly brown. The precipitate is somewith sesquioxide of chromium. When heated what voluminous at first, but on standing it in contact with organic matters it readily becomes heavy and settles well. After the gives up oxygen to the carbon and hydrogen mixture has been allowed to settle, collect the which they contain. Its composition is:- precipitate upon a filter and wash it with cold PbO.. 22.. 8.93 water which has been'mixed with a. small CrO3 100.5.931.0}7 cr03s 100.6~_ quantity of mercurous nitrate. If pure water 323.5 100.00 were used, cloudy washings would run through Principle II. Oxidizing power of, and fact the filter. Ignite the dry precipitate in a plaof its fusinu at a red beat. of its ting at a reI heat. tinum crucible, and weigh the sesquioxide of Applications. Estimation of carbon in or- chromium that is left. Even when the preganic substeances. cipitate is contaminated with small quantities M]~ethods. See Carbon, pp. 73, 74, 76. of insoluble chloride or sulphate of mercury, For use in organic analysis,'chromate of nothing but oxide of chromium will be left load may be prepared as follows: —Add a after strong ignition. But the method should solution of bichromate of potassium in slight nevertheless be avoided when the solution to excess to a clear filtered solution of acetate of be analyzed contains any very large quantity lead, slightly acidulated with acetic acid. of a sulphate or chloride.- The process Wash the precipitate repeatedly by decanta- is specially commended by H. Rose, who finds tion with water, then collect it upon a piece of it decidedly preferable to the processes dependcotton or linen cloth, and again wash it thor- ing on the insolubility of chromate of lead oughly. Dry the powder, put it in a Hessian and chromate of barium. It is somewhat less crucible anld heat the latter to bright redness, exact when applied to the separation of until its contents are fatirly fused. Then pour chromic acid from oxide of chromium, since a the melted chromate upon a slab of stone or small quantity of the latter is liable to.go iron, pulverize] the sheet of solid chromate, down with the chromate of mercury. sift the powder through a tolerably fine me- Properties. The chromate formed by pretallic sieve, and keep the powdler in stoppered cipitating mercurous nitrate with bichromate bottles. When properly prepared the chro- of potassium is a basic compound (4Hg20, mate of lead will appear as a heavy, dirty, 3CrO1). It is a bright red powder, which yellowish-brown powder, It should be free turns black on exposure to light. Ammonia frlomn substances soluble in water, and from water converts it to a black powder, about any contaminatlon with organic matter, such half the chromium in which is in the state of atsdust. To test whether it be free from or- sesquioxide. It dissolves very sparingly in ganie matter, heat some of it to redness in'a cold water, but more freely in boiling water, tube of hard glass, and conduct into lime wa- partly in the form of mercuric s5lt. It is ter any gas which may be evolved. The for- slightly soluble in ammonium salts. Chlorhymation of any precipitate of carbonate of dric acid decomposes it with formation of calcium would indicate impurity.- Chro- mercurous chloride and chromic acid. Nitrous mate of lead may be used over and over again acid or a nitrite reduces it. At a red heat it indefinitely, if it be powdered, moistened with is resolved into oxygen gas, mercury vapor nitric acid, dried, and fhsed after each corn- anil sesquioxide of chromium. bustion. For the second time of using the onoC a of otassi. zn MonoChromate of Potassium. nitric acid may be omitted; it will then be See Chrote of Sodium. For the use of sufficient to roast, fuse and powder the chro- Chromte of oium ti o monochromate of potassium as an indicator 106. 127.) When used forithe combustion off silver and sulphur compounds in long tubes, the chro- clorine, see Chromate of Silver. mate of lead may be used three or four times BChroma te of Potassium. without'refusion, and may afterwards be Principle. Oxidizing power. treated by Vohl's process, above described, Its Applications are numerous in volumetric just as if no sulphur were present. (Carius, analysis. As a material for preparing standAn.nalenz Chem. und Pharm., 116. 28). ard solutions it has the merits of being cheap, Chromate of Mercury. (Mer- easily kept, easily weighed and readily obcurous chromate), tained in a state of purity. Valuation of 186 BICHROMATE OF POTASSIUM. bichromate of potassium (Methods 1, 4). 2. Reduction of the bichromate by Ferrous Preparation of a standard solution of iodine Salts. See the corresponding head(ing under (Method 1). Estimation of iron (MIethod 2); Chromic Acid. Sec also Ferrous Salts. To of oxalic acid (MAethod 3); of tin (MIethod prepare a normal solution of' bichromalte of 4); of antimonious and arsenious acids (MIethod potassium, dissolve 14.759 grin. (1 equivalent) 6); and of coloring matters (Method 7). of the pure salt in water, and dilute the soluilethodls. tion to the volume of 1 litre. 50 c. c. of sutch 1. Reduction by Chlorhydric Acid. See a solution correspond to 0.84 grm. of metallic Arsenious Acid and Chromic Acid. To de- iron, or the whole litre to 0.6 equivalent (_ termine the value of a sample of bichromlate 16.8 grins.) of' iron, which may be converted of potassium weigh out 0.3 or 0.4 grinl. of it, fiom the state of' protoxide to that of sesquiplace it in the flask of' an apparatus such as is oxide. Care must be taken to use perfectly described under Chlorine (action of upon KI, pure and dry bichromate. To dry it, healt it and upon As203), pour upon it a considerable in a porcelainr; crucible until it begins to fuse, excess of pure furning chlorhydric acid, free allow it to cool in a dessicat.r, an(d weigh out fiom any contamination of' chlorine or sulphu- the required quantity when thle salt is cold. rous acid, and heat the flask. After 2 or 3 Besides the ordinary normal solution another minutes boiling the whole of the chlorine will solution should be prepared( ten tiles more have passed out of the flask, and have liber- dilute (see Alkalinietry, p. 18), containin, atemd a corresponding amount of iodine in the only 0.01 equivalent of the bichromnate in thle absorbing vessel in case iodide of potassium litre. It is well to test the correctness of' tlhe were placed in it, or have oxidized an equiva- standard solution thus prepared, by using it to lent amount of arsenious acid in case arsenite oxidize a known weight of' pure iron - The of sodium is used as the absorbent. No loss details of' an actual estimation of' iron are as of chlorine need be apprehended at the mo- follows: — Mix the rather (lilute solution of ment of adding the clhlorhydric acid to the the Ferrous Salt with enough chlorhydric acidl, bichromate, for the evolutiomn of' that gas does or dilute sulphuric acid, to make it decidedly not begin until the mixture is heated. When acid, and ad(d a standard solution of biChrothe absorption liquor has become quite cold, mate of Potassium, until a drop of the liquid transfer it to a beaker and estimate the Iodine ceases to yield a blue color when tested with or the Arsenious Acid. Three atoms of chlo- ferricyanide of potassium. The bichromate rine are liberated for every molecule of solution must be poured slowly fi-om a burette chromic acid. The decomposition of' the bi- into the iron solution, and the latter should be chromate by the chlorhydric acid is rapid and constantly stiirred with a thin glass rod. The complete, and although it lay sometimes liquid, which is at first almost colorless, soon happen that a little of' the volatile compound acquires a pale green tint, which gradually chlorochromlic acid (CrCI3, CrO3) goes forward chang(res to a darker chromne green. From no harm is done, inasmuch as this colmpound time to time a small drop of' tile liquid should liberates just as much iodine as would have be allowed to fall fiom the stirring rod upon a been liberated by its components. (Bunsen, drop of' a solution of ferricyanide of potassiun Annalen Chem. und Pharm., 86. 279). on a white plate. - To save time, a numLlTo prepare a solution of iodine of known ber of drops of'tllthe ferricyvanide solution should strength, Bunsen conducts a known quantity of be put ulpon the plate beforehand, and the chlorine into an excess of' iodide of potassium, iron liquor should be added to these drops in in aqueous solution. The known quantity of' regular order. As soon as the test e&ases to chlorine is obtained by heating pure bichro- show a strong blue reaction, the bichromlate mate of potassiumn with chlorhydric acid, as must be added slowly and carefully, and above described. To this end weigh out towards the close the test should be applied about 0.35 grin. of the pure bichromate, which after each new addition of two drops, or even has been dried by heating it just to fusion, one drop of the biehromate solution. Towards and proceed as above. Enough of the solu- the very last *a couple of' drops of' the iron tion of' iodide of potassium mrust be taken to solution should be taken for the ferricyanide hold dissolved all the iodine which is set free. test, and an appreciable time should be alThe cold, perfectly clear brown liquid is rinsed lowed for the appearance of' the reaction. into a beaker and is known to contain a defi- The oxidation is complete when no further nite quantity of iodine, for each molecule of blue coloration of the ferricyanide is manithe bichromlate taken corresponds to 6 atoms fested. The reaction being exceedinlg sensiof' iodine. With proper care this method an- tive it is easy to hit the exact moment when swers very well, but it requires skilfil ma- the oxidation is complete. In order to imake nipulation, and is less convenient than the the results as accurate as possible, it is best to ordinary miethod of' weighing out pure Iodine employ two solutions of' the bichromnate, the and dissolvirng it in iocdi(le of potassium. It one comparatively strong and the othcr weak. has the disadvantage, moreover, of depenling A nominal solution mlnay be used at firlst, but on the atomic iweight of chromium, which is just at the end of' the proceses a omme-tenth I-lolstill somewhat in doubt. mal solution should be employed. The iron BICHROMATE OF POTASSIUM. 187 solution must be kept decidedly acid in order this empirical calculation is to be sougllt in the to prevent the deposition of any brown chro- incomplete decomposition of the bichrolnate by nmate of chromiull, upon which the ferrous the tin solution rather than in any error in the salt would exert scarcely any deoxidizing ac- accepted atomnic weight of tin. _ In case the tion (Penny. Schabus). - The process has tin solution to be examined contains stannic special merit in that the standard solution chloride as well as stannous chloride, deterof' the hichromate cali be easily made and( mine the amount of the latter in one portion of ke)pt. For the methods of' changing a ferric the solution, andill another portion throw down salt to the condition of' flerrous salt, to prepare the whole of the Tin by mneans of zinc, disit for analysis see Ferric Salts. solve in chlorhydric acid and by means of' the An indirect grayviuetlic method of estimat- bichromate solution dletermine the whole of ing iron, )1roposed by Voll (Aall/enz. Chlew. the tin (Strengr, Pogqenrloift's Annaleia, 92. tned Pht/urm., 94. 218), depends in parlt upon 57; Mohr, Titrirmethode, 1855, 1. 264). The t!iis prilcil)le. The solution of ferrous salt, process is but little esteenie(l. - Acwhich must be highly concentrated, is mixed cording to Mohr (loc. cit., pp. 260, 262, 267), with a slight excess of bichrolnate of potas- the results are liable to vary slighltly froml one sium, and the excess of the bichromate is de- another in a muanner not readily explicable. terllined by heating it with an oxalate and The results always come out a little too low collectinr andl weighling the carbonlic acid when the iodidle of' potassium and starch are which is evolved (see under Chromic Acid). added directly to the tin solution, as above deThe qu;antity of' iron is calculated from the sciibed. - Better results are obtained in -weight of' the bichromate that was consumed operating as follows:- Take a measured quanill oxidizingy it. The process is complicated tity of' the bichromate solution, acidulate it and difficult. with chlorhydric acidl, and pour the tin solu3. Reluc'ion of the bichromate by Oxalic tion into it froin a burette until the pure green Acid. Mix the oxalate to be analyzed with color of' chloride:of' chromium appears. Add an excess of' bichromate of potassium, add vet another c. c. of the tin solution, then imix sulphuric acid to the mixture, and collect and'with the liquid the iodide of' potassium and weigh the carbonic acidl that is evolved. 2 starch an(l po'umr in the bichromlate of potasequivalents of carbonic acid will be obtained sium tiom the same burette whence the imeasfor each equivalent of' oxalic acid in the sub- uie.d quantity was taken, until the nappearance stance. in case free oxalic acid is to be exam- of the blue color. Compare the similr.- headincld, supeirsaturate it slightly with ammonia in(r undler Chromlic Acid. water after weihling bet'ore proceedingr wit 5. eledutction of the bichromate by/ Ferr)othe analysis. For orlms of' apparatu.ts proper cyanide of Potassivum. See Chromlic Acid. for effecting the lecomlposition see Carbonic The reaction between bichroinate of potassium Acid, volatility of' (Vohl). Compare Chromnic and feirocyanide of' potassium is as follows:Acid. The samle principle is involved ii one fIK4rFeCY + K20, 2CrO3 + 14ICI = GK3FeCy0 + 8K(CI + of' the Imethiods of estitmation of iron, described 2CrCls + 71-120. under the head reduction of the bichromuate by Hence 21.122 grmls. of crystallized ferlocyana ferrous salt. ide of' potassiuiim are equivalent to 14.759 grnis. 4. Reduction of the bichrornate by/ Sltanous of bichroillate of' potassium (E. Davy, Phil. Chloride. MAe#l., (4), 21. 214). A. For the method of estimlating chrlonic 6. Red(uction io' the bichroalc;'e by Arsenious acidl iln this way see the analogous helad.incn and bi Alntilniorous Acids. The details of the un(ler Clhroic Acid. m.ethod ftr cstim'ntil Antinmonious Acidi (see il. To estimate tim br:ine' t,.le mretal into so- p. 31) and Arsenious Acid (p. 46) are as follution in clhlorhydric cii, in a flask, or' ifit be lows:- Prepare a st.ii(larl solution of bialbealyx in solution acidlulate the liquor strongly chroinate of potassium which shall contain wvithll chlorhydri c acidl add a small quantity of about 2.5 grms. to the litre. Weigh out exa solution of icdilde of potassium and some actly 5 arms. of pure arsenious acid, dlissolve thin starch paste, shake the flask continuall)y it in a solution of' carbonate of' sodiuli, slightly alil pour into it from a burette the stan(lard acidulate the solution with chlorhydric acid, solution (on0e-terith normal) of' bichroilmate of thlen add 100 c. c. Inore of' chlorhydrIic acid of potasslillm, prepared( as above described, until 1.12 sp. gr., and dilute to a litre. Each c. c. the entire liqui(t suddenly becomes blue. of this solution will contain 0.005 grin. of F'rom the anmount of bichromate of potassium arsenious acid, and will correspond to 0.007374 consumned reckon the quantity of' tin in the grin. of antimonious acid. Dissolve about 1.1 solution. In order to do this correctly several grm. of iron wire in 2 c. c. of dilute sulphulric chemlists have attempted to detelrmnine once for acid, prepared by mixing 1 volume of' concenall how iluch bichrornate of potassium is trated acid with 4 volumes of water, and dilute ne(ledl to oxidize 100 parts of pure tin dis- the solution to the volulme of' a litre. To -solved iii chlorhytlric acid. Penny and Streng, establish the relation between the bic'hromate for example, found that 83.2 pts. of the bichro- solution and the iron solution pour 10 c. c. of mbate were neelded. The reason of the need of the bichronmate solution into a beaker from a lss88 BICHROMATE OF POTASSIUM. burette, a(ld 5 c. c. of chlorhydric acid, and f6r 24 hours, at a temperature of 20~ to 22~. 50 c. c. of water, and pour in the iron solution By the action of the fuming acid the indigorapi(lly from a burette, until the liquid is tine is dissolved, while the foreign matters are green. Continue to add the iron solution by carbonized or destroyed. Dilute the sulphuric portions, of I c. c. each, and test the liquid solution with water, filter and bring the filtrate after each such addition, by touching a drop to the volume of 1 litre. Measure out 100 cc. of it to a drop of a tolerably dilute, freshly of the solution into a porcelain dish by means prepared solution of ferricyanide of potassium of a pipette, boil it gently4 add 10 c. c. of upon a white porcelain plate, until a distinct chlorhydric acid, and pour the standard solublue reaction of the ferrous salt is obtained. tion of bichromnate into the boiling liquid from Then add 0.5 c. c. of the solution of bichro- a burette, until the instant when the greenish niate, and afterwards the iron solution, two tint of the liquid disappears, an(l is replaced drops at a tine, till the blue reaction, with the by a yellowish orange. A little practice is ferricyanide, just occurs. Read off both the necessary in order that' the completion of the burettes and calculate how rimuch of bichro- reaction may be hit with c6rtainty. - The nate solution corresponds to 10 c. c. of the result of the first trial should be regarded as a iron solution. Since the iron solution cannot mere approximation, and should always be be kept for afiy length of tinme without oxidiz- controlled by a second experiment upon anin,, this experiment. must be repeated before other 100 c. c. of the solution. The number each new series of analyses - To dbtterm- of tenths of A. c. of the lichromate solution ine the relatiini between the bichroinate so- consumed gives the percentage of' irndigotine lutioh' and the solution' of arsenious acid, in the sample. The amount of bichromate transfer 10 c. c. of the latter to a beaker, add require(l t6 decolorize a given weight of' pure 20 c. c. of chlorhydric acid of 1.12 sp. gr., and indigotine, taken in the forIn of sulphindigotic from 80 to 100 c. c. of water, and pour in the acid, has been found in practice to agree exsolution of' bichrornate from a burette till the actly with the quantity reqluired by theory to yellow color of the liquid shows that the bi- change the indigotine to isatine, or rather to chromate is present in excess. Then wait a sulphisatic acid. As long as there is any inIbv miniiutes and pour in from the other bu- digotine present to be oxidized, the bichronmate rette the iron solution to slight excess, as acts upon it alone. 3 molecules, or 393 parts above, then again 0.5 c. c. of the bichromate, of indigotine require 1 molecule, or 297.2 parts anld finally the iron solution, two drops at a of the bichroinate. In other wor(ds, 100 parts time, until the blue reaction with the ferricy- of indigotine require 75.6 parts of the bichroanlide appears. Deduct firoIm the total amount mate. In case the indigo contained any ferric of' bichromate solution employed, the quantity oxide, this would be reduced in the process of which corresponds to the iron used, and pro- solution, and the'ferrous salt formed would ce(1 to calculate how much antiinonious acid consume an equivalent quantity of the bichrocorresponds to 100 c. c. of the chromate solu- mate. Such indigo should be leached with ti0n, that is to say, how much Sb20, will be dilute boiling chlorhydric acid to remove tlle converted into Sb205 by this quantity of the iron before it is subjected to analysis. The bichroinate. See further under Antiinonious same treatment is advisable in case the indigo Acidl. The water used to dilute the solution contains much carbonate of calcium. (Penny's of arsenious acid, above, must be mecasured, process, as used by Et-nest Schluniberger, ai.nd since the action of bichromate of potassium reported by Schiitzenberger in his MIatires upon arsenious and antinlonious acids is nor- Colorantes, 1867, 2. 560). The process is aprnal only when the liquild contains at least one- plicable for the valuation of' other'coloring sixth of its volume of chlorhydric acid of 1.12 matters besides indigo. sp. gr. (Kessler). Fresenius (Zeitsch. analyt. Principle II. Power of precipitating lead Chem., 1869, 8. pp. 154, 155, 159) found the from its solutions. See Chromate of Lead. process to yield excellent results when applied For use as a reagent, bichromate of potasto the estimation of exceedingly small quanti- sium may often be found pure in commerce. ties of antimony. The commercial salt, however, is liable to be 7. Reduction of the bichromnate by organic contaminated with sulphate of potassium. To Coloring Mlatters. As applied to the valuation free it from this impurity dissolve some of the of indi(o the process is as follows: — Prepare salt incompletely in warm water, and let it a standard solution of bichromnate of potas- crystallize. Repeat this process of crystallizasiurn containing 7.66 grins. to the litre. 1 c.c. tion until sulphuric acid can no longer be deof this solution corresponds to 0.01 grm. of tected in the product. In order to test for pure indigrotine, or to 10 c. c. of a solution sulphuric acid, reduce some of the bichromate which contains 1 grin. of' indigotine to the by boiling it with pure, strong, chlorhydric litre. Reduce to fine powder a quantity of acid under a hood, dilute the product with the Indigo to be tested, dry it at 1000, weigh water, add a drop of chloride of barium, and out precisely 1 grin. and imix it in a capsule let the mixture stand for some timle. The biwith 12 grins, of' f'uming sullhuric acid. Cover chromlate must be perfectly free from sulphur, the dish with a glass plate and leave it at rest in case it is to be used fobr estimating sulphur CHROMATE OF IIVER. 189 in organic compounds, and it should be as hinder for a long time the separation of chropure as possible when used for making stand- mate of silver. With the acetate of so(lIun ard solutions. But in case it is to serve for a reaction was obtained after the third drop of estimating carbon or a carbon compound by bichromate, but in its absence there was no heating it with the substance and sulphuric reaction until the fifth drop. As a rule, in esacid, no special degree of purity is necessary. timating phosphoric acid, when the liquids are Chromate of Silver. not too strongly acid a correction of 0.4 c. c. P)rinciple. Deep red color and insolubility may be applied to compensate for this solubilin water. ity of the indicator (Mohr, Zeitsch. ancllyt, Application. Use as an indication in the Chen., 1863, 2. 254). volumetric estimation of chlorine, silver and Ch romate of Sodium. lead. Principle. Fixity when heated and solubilMethod. See Chloride of Silver and Chro- ity in water. mate of Lead. When-a solution of nitrate of Applicationis. Separation of chron-mic acid silver is added to a solution of neutral chro- from Ba, Sr, Ca, MAg, Zn, Mn, Co, Ni, Fe. mate of potassium chromate of silver is imme- Mlethod. VWeigh out sonle of the chromiate diately precipitated as a bright, blood-red to be analyzed, mix it in a platinum crucible' powder, but sparingly soluble in water. Ac- with four parts of carbonate of sodium andl cording to Mohr (Titrirmethode, 1856, 2. 25), fuse the mixture thoroughly. Treat the flsed 1 part of it dissolves in 6700 parts of water at mass with hot water, and filter the solution irn 17.5~, and in 3700 parts of boiling water. Its order to separate the insoluble carbonates or, color is so deep that it can be readily seen, oxides firom the soluble chromate of sodium. In; even when largely diluted by a white precipi- case manganese be present the fusion must be tate or a yellow liquid. It is immediately de- mnade in a bulb tube, in a stireaml of carbonic' composed by soluble metallic chlorides, with acid. Since the insoluble carbonates or oxformation of insoluble chloride of silver and ides thus obtained are liable to be contaimiia soluble chromate of' the metal. It is decorm- nated with alkali they cannot be weighed dipose(l also by solutions of the alkaline carbon- rectly. - Instead of fusing. with carbonate ates, and is readily soluble in free acids. of so(dium alone a mixture of that substance When used as an indicator in the volumiet- and carbonate of potassium may be used, ric process of' estimating phosphoric acid by The mixture has the merit of melting at a Chromate of Lead some annoyance is occa- comparatively low temperature. The Chrosioned by the easy decomposition of the chro- mates of Barium, Calcium and Strontium may nmate of' silver by the acid in the liquid. As be more readily and completely decomposed the volunme of the liquid increases, moreover, by boiling with an excess of a solution of an the indications of' the chromate of silver be- alkaline carbonate than by the method of' fuscome less sharp. It may be said, in short, ion just described (H. Rose, Journ. prlaktt that silver as an indicator of chromic acid is Chem., 66. 166, and Handbuch 6tM Aufl., 2, very delicate in neutral solutions, cannot be 384). used at all with the mineral acids, and is so For the various metlhods of converting oxmuch the less delicate in presence of' acetic ide of' chromium into chromate of sodium see acid in proportion as there is more of the acid sesquiOxide of' Chromium, action of oxidizing in the solution. Acetic acid does not prevent agents upoiin the formation of the red color completely, as Chromate of Strontium. the smallest vuaIntitv of' nitric acid would, but lPrincipJle. Decomposition of by alkaline it delays its appearance rearkably. It carbonates. should be used, therefore, only illthe smallest Apllication. Separttion of chromic acid possible quantity,, aid the'volume of' the liquid from strontium. should'be kept as small as may be'practicable. 1lelhod. See Chromate of Barium and To test the limit of action of' the indicator Chronlate of Sodium. A single boiling with a single drops of a one-tenth normal solution of solution of' carbonate of' sodium is sufficient to bichromate of' potassium weere added to b0 c. decompose chromate of' strontium completely c. of water, and after each such addition a lit- (H. Rose). tie of the water was touched to a drop of ni- Chromium is determined either as sestrate of' silver upon a white plate. The first quiOxide or as a Chromate of' Barium,( and second drops gave no reaction, but the'Lead or Mercury, or indirectly by the reducthird gave a visible red color. A small quan- tion of' Chronlic Acid. It is noteworthy tity of' acetic acid being then added to the that although chromium cannot be precipiwater, its power of' reacting with nitrate of tated by itself as a basic acetate, some of' it silver disappeared, and was not recovered un- will go down with iron and aluminum when til 0.4 c. c. of' the solution of bichroniate had these metals are thus precipitated (Gibbs, been added. Even then a little acetate of' so- Ailerican Joulrn. Sci., 1865. 39. 61). diumn had to be added to the water, for in its Cinchona Bark. [Compare Quinine absence tile bichromlate in reacting upon the and Cilichonin]. nitrate of silver set free enough nitric acid to Principle. Insolubility of the cinchona al 190 CINCHONA BARK. kaloids in aqueous alkaline solutions, as well down the alkaloids. while it holds in solution as their solubility in acids anid in ether, chlo- the taunic acid, cinchonic red and( other colorrofiorin and alcohol. in r matters. and the resin with which the acid,Aet/~hoe'.s, solution of tle alkaloids was contalminated. To purif t tle precipitate it may le treated Method of Rabourdin (A). A quantity of with a quantity of chliorhydric aci(l insuffiicient the bark having been reducc'l to powder and to dissolve thie whole of it, and. the solution sifted through a fine hair sieve, the powder mixed with amminonia, whereby the quinine is (40 granmmes of the gray bark or 20 grammes thrown down white and pure. Or the precipof the yellow, Calisaya, bark) is packed in a itate lmay be dissolved in a shligt excess of percolation cylinder and exhausted with water chlorhydric acid, the solution filtered if need aci(lulated wifh chlorhvdric acidl. To prepare be, an'd then treated with dilute ammonia unthe acidulated water mix 20 grmins. of' strong til a brown prle(ipitate appears, and a colorless chlorhydric acid with 1 kilog. of water. As liquor can be obtaii.e d by filtration. Oni addsoon as the percolate passes off colorless and inig anlmonia to this colorless filtr ate quinine is tasteless add( to it 5 or 6 grins. of caustic pot- precipitateil together with lirght trlaces of' (inash together with 15 grins. of' chloroforml. chonine. This precipitate is wvashed, dried in Shake the mnixture during several minutes and the air and weighed. In case too much ainthen let it stand. In the course of half an mnonia is addedI in the first rplace, so that white hour a dense whitish deposit consisting of flocks are;iircxed,-itdl the brown precipitate, a chloroform charged with the cinchona alka- little of the acidtulhited iv;:ter mnuit be adide(l to loids will separate fiom the water. The water rediissolve them (1Rtebordin, Joure. PIChar;). et is then decanted, and the chloroformic solution Chimr.,1861, p. 408, citetd by Van der Bur(g, washed repeatedly with water by decantation. Zeitsch. analylt. Che,?., 1865, 4. 288). Sometimes the separation of the chloroform With reoacrd to the f'oregoing process Van friomn the water is instantaneous and complete, del Burg (/oc. cit., pp. 292, 289) reports that so that the red transparent liquid left floating it is exceedinglily dilhicult, if not imlpossible, to above the chloroformn may be immediately extract all tie alkaloids fiom cimnImhona bark poured off: The washed chloroforlmic solution by lleans of' toiur per cent. ehlorlShydric acid at of the alkaloids is tiansferred to a porcelain the ordinary tetIperature. Even wvith the mutcapsule, anli evaporated to dryness upon a most care a relatively large proportion of' the water bath. In the case of red bark or Calisaya alkaloids remains in' the residue of the percobark the residue, consisting of' alkaloids in a lation, As a mIeans of extracting the alkaloids condition of tolerable purity, is simply weighed, firom bark the dilute chlorliydric acid is dlisBut for the pale or cinclionine barks the pro- tinctlv iifeirior to tihe liime and alcohol enIn cess must be carried further. The resi- ployed by de Vrij. The process was folrmerlly due left on evaporating the chlloroform contains held in considerable esteem on account of its cinchonic red as well as cinchonine. To re- cheapness and supposed accuracy. move this imlpurtity treat the residute with According to Van der Burg, the largest water acidulated with chlorhydric acid, which alnoulnt of alkalolds is obtained when the soiuiwill dissolve the whole of the alkaloids andl a tion is concentrated( to a small bulk before tihe portion of the cinchonict red. Filter the liquid precipitation, and finally treated with a large. and add to it, drop by ldrop, with constant stir- excess of' ailmnonia. No absolutely colorlelss rinuy aminonia water diluted with 15 or 20 sclutio::s can be obtained by the method of parts of water, as iong as the cinchonic redl piartill precipitation with ammonia, eveii continues to be precipitated in reddish brown whenl so muclh ammonia, is used that a part tf' flakes, and until white curdled flakes of cin- the alkaloids is precileitated toogether with tl e chonine, not remlioved by agitation, begin to coloringr matters; at the best the solution will appear. In this way the cinclionic redl is first still be of a liht yellow color. It is none the precipitated before any of' the alkaloid goes less true, Iowever, that a consiterable cquandown. Filter, wash the precipitate with a tity of colorilng niltter fiee frion alkaloids cln small quantity of water and( precipitate the al- be thius thrown down by ammonia befbre the kaloids in the filtrate by adding an excess of' alkaloids themiselves are precipitated. This allmlonia. The p)recipitate is collected upon method of fi-actional precipitation is on the a filter, washetl, dried and weighed (Rabourdin, whole to be preferred to the other precess of tU. S. Dispens., 1867, p. 295, note; IHla(tdw., 1. purification by partial solution. It is to be 470). observed thlat the cinchona alkaloids are less 2. 3Afethod qf Rabou'rdin (B). Exhattst 40 soluble in strong thaIn in dilute amniinolma ivagrins. of gray bark or 10 grins. of red or' Cal- ter. - The alkaloids finally obtained alisz; aya baik, at the oldinaly telmperature, with wways contain traces of alkaline earths and of water acidulated with 3 or 4 per cent of coloriing mlatters, They should be d(Mieel over cholrhydric acid, until the filtrate tastes only sulphuric acid before weighing, since the airsligltly bitter. Add to tile acid liquor a quan- dried alkaloids alway-s retain considerable and tity of soda lye. collect the precipitate andi vary-ing quantities of water. The statemenllt wash it with a little water. The soda throws of Itabourdin that an assay of cinichona can CINCHONA BARK. 191 be finished in an hour is erroneous. More tion of boiling the bark with lime and alcohol than an hour is required for the process of be several times repeated, so that the final percolation alone, and' the process is incom- residue shall retain only an insignificant quanplete even then, as has been already stated. A tity of the alkaloi(ls Moreover, after the much larger quantity of the acidulated water evaporation of' the alcoholic solution acidushould be used than is directed bv R. More lated with acetic acid, and the subsequent than twice as much as would appear from his treatment with water and filtration, he prefers statement that fronm 100 to 120 grins. of filtrate to precipitate the alkaloids with caustic soda, are obtained from 10 grms. of' bark. Not only and to separate the coloring nmatter by redisquinine but all the other cinchona bases are solving the precipitate in dilute chlorhydric precipitated(, so that the method gives only the acid and partial precipitation with ammonia, total amount of alkaloids. as directed above, in the second description of 3. 3Iethod of (le V'ij'. Mix a weighed Rabourdin's process. The purified alkaloids are quantity of the powvdered bark, dried at 100~ finally to be dissolved in alcohol, evaporated with 0.25 of its weight of hydrate of calcium, in a tared platinum dish, dried and weighed. a(nd boil the mixture for 5 minutes with ten Since quinidin is somewhat soluble in pure tines its weight of alcohol of' 0.852 sp. gr. water, and quinine still more so, it is well to Throw the mixture upon a warm filter and collect by themselves the washings of' the soda wash with small portions of boiling alcohol, precipitate, as soon *as they cease to exhibit a until the filtrate is equalto 20 timesIthe weight strong alkaline reaction, and begin to taste of the bark taken. Add dilute acetic acid to slightly bitter; to shake the liquor with ether, the alcoholic filtrate until a slight acid reac- to collect and evaporate the ethereal solution, tion persists, then evaporate tihe liquid to dry- and add the residue to the precipitate, before ness upon a water bath, treat the residue with proceeding to treat the latter with alcohol. water, throw the aqueous mixture upon a filter 4. Process of TiVinckler. Digest 1000 grains and wash with water, until a portion of the of the finely powdered bark with 6 ounces of clear filtrate ceases to become cloudy on the alcohol of' 80 per cent upon a water bath, until addition of an alkali. The aqueous solution it is completely exhausted. When cold, strain thus obtained contains all the alkaloids of the the tincture through thin, close linen. Digest bark, while the Kinic Acid and fatty and the residue anew with 3 ouncesof alcohol, and resinous matters remain upon the filter. strain the mixture as before. Yet again treat Evaporate the aqueous solution of' the alka- the residue in like manner with alcohol. Unite loids to a small bulk upon a water bath, and the several alcoholic solutions, filter and treat imix the concentrated liquor with a slight ex- the filtrate at the ordinary temperature with a cess of' strong milk of' limne to precipitate the mixture of equal parts of freshly slaked limne alkaloids. Throw the precipitate upon a small and crude well burnt animal charcoal, of' which filter, and wash it with the smnallest possible about 500 grains will be required. Shake the quantity of' cold water. If' the operation be mixture frequently, and let it macerate until prtoperly conducted, the quantity of' water the supernatant liquid is observed to be colornecessary to remove the coloring matter will less. In most of'the genuine barks the liquid is be so small that the trace of alkaloids dissolved soon decolorized, but in those conltaining kinonic by it may be safely neglected. _ After acid the process is imperfect. Decant and filwashing with water, dry the filter with its ter the decolorized liquid; shake the residue contents, and boil the whole repeatedly with repeatedly with small quantities of alcohol, and alcohol of 0.819 sp). (gr. to dissolve the alkaloids. afterwards throw it upon a filter and wash it Filter the alcoholic solution, collect the filtrate with alcohol. By distilling off the alcohol in a weighed platinum capsule, dry upon a friom the filtrate there is obtained a mixture of' water bath and weigh. The total amount of alkaloids, fatty matter, cinchonic red, and any alkaloids is thus obtained; f'or the methods of' kinonic acid which may have existed in the separatingr them1: See Quinine; Iodhydrate of bark. To remove the impurities transfer Quinidin; Cinchonin. (l)e Vrij, Zeitsch. an- the matter to a small evaporating dish, and alyt. Cheim., 1865, 4. pp. 202, 274.) wash out the distilling vessel with water acidAccording to Van der Burg (Zeitsch. analyt. ulated with sulphuric acid, Add somlle more Chemn., 1865, 4. pp. 287, 292) the method of sulphliric acid to the dish, until it is in slighlt de Vrij is faulty, inasmuch as it is very diffi- excess, heat the mixture, then allow it to cool, cult to extract the whole of' the alkaloids from anud filter off the kinonic acid and other ilicinchona bark by means of limne and alcohol, purities which have been precipitated. Addl a and that a certain quantity of' the lime goes slight excess of' ammonia to the filtrate, and into solution to be afterwards reckoned as cin- evaporate to drylless at a gentle heat the mixchonin. But the lime and alcohol are never- ture of precipitate and liquid. Remove the theless mnore efficient agents than dilute sulphatr of' anmmnonium from the residue by chlorhydric acid (see Rabourdin's method, mear. of a snmall qulantity of very cold water, above) for extracting the alkaloids. Van der and dry and weigh the residual alkaloids. Burg consequently recommends de Vrij's Though the alkaloids thus obtained are not abmethod with this modification, that the opera- solutely pure, their amount affords a tolerably 192 cMtICHONIN, good indication of the value of a bark. Method. Evaporate the solution upon a WVinckler states that the' barks yield to the water bath to expel alcohol, if' any be present, manufacturer quite as much as is obtained in dissolve the residue in water acidulated with this way, and generally from 0.12 to 0.25 per acetic acid and addl soda lye to the solution. cent more, in consequence of the loss in work- Collect the precipitate upon a filter, wash it ing being less on the large scale (WVinckler, with water and dry and weigh it. The pre-.American Journ. Pharm., 26. 343, through cipitate consists, according to circumstances, of U. S. Dispens., 1867, p. 295). - The best cinchonin or of' a mixture of cinchoninand yellow Calisaya bark, the finest red bark, and cinchonidin. In case Cinchona Bark is exthe finest fibrous Carthagena bark (soft Pit- tracted with lime and alcohol the cinchlonin aya), each yield about 3 or 4 per cent of al- precipitated as above is apt to be contaminated kaloids; while between these and the barks of with lime (van der Burg). It may conselowest value there is every grade of product- quently be well to treat the dry precipitate iveness, down to a mere trace of alkaloid with alcohol, to collect the alcoholic filtrate in matter (U. S. Dispens.). a tared platinum dish, and evaporate it to 5. Process of Hager. See Picrate of Cin- dryness for a second weighing (De Vrij, chonin, etc. Zeitsch. analyt. Chem., 1865, 4. 203; van der 6. The British Pharmacopceia gives the fol- Burg, ibid, pp. 275, 287). According to De lowing methods of testing the various colored Vrij, small quantities of cinchonin can only barks. be determined with certainty by means of a A. Test of Yellow Cinchona. Boil 100 polarization appparatus. grains of the bark reduced to very fine pow- Citri Acid. der, for quarter of' an hour, in a fluid ounce of Priuciwmle J. _Power of neutralizing alka'distilled water acidulated with tep minimrs of lies. chlorhydric acid, and allow it to macerate for Application, Valuation of solutions of the 24 hours. Transfer the whole to a small dis- acid. placement tube, and after the fluid has ceased Miethod. Color the solution with solution of to percolate add at intervals about an ounce logwoo'l andl titrate with standard caustic'soda and a half of similarly acidulated water, or (see Acidimetry) (MAlohr). add until the fluid which passes through is free For estiimatingo the value of lemon juice the from color. Add to the percolated fluid a so- English practice is to neutralize a lneasured lution of subacetate of lead, until the whole sample of' the juice either with chalk or with a of the coloring matter has been removed, tak- standard solution of' carbonate of sodiunl, and ing care that the fluid remains acid in reac- to calculate lirom the amount of alkali extion. Filter and wash with a little distilled pended an equivalent quantity of citric acid. water. To the filtrate add about 35 grains of According to Ogston, these methods inlvariacaustic potash, or so much as will cause the bly give too high an estimate of the value of precipitate which is at first formed to be nearly the juice. Any foreign acids which may be redissolved, and afterwards 6 fluid drachms of present, as well as any aluminum salt which pure ether. Then shake briskly, and having may be precipitated, go to increase the amount removed the ether repeat the process twice of' alkali used and the weight of citric acid with three fluid drachms of ether, or until a calculated. drop of the ether employed leaves on evapora- Principle II. Inability of the acid to inflution scarcely any perceptible residue. Lastly~ ence the plane of vibration of a ray of' poevaporate the mixed ethereal solution in a larized light. capsule. The residue, which consists of nearly App,)licaticn. According to Buignet, it is pure quinine, when dry, should weigh not les easy to detect on this principle any adulterathan 2 grains, and should be readily soluble in tion of the acidl with Tartaric Acid, by means dilute sulphulric acid. of a polalrization apparatus (Journ. 1'harm. et B. Test for Pale Cinchona, 200 grains of Chiam., 40. 252, and Zeitsch. analyt. ('heml., the bark, treated in the manner directed in 1862, 1. 234). the test fbr yellow'cinchlona, with the substi- Cobalt is usually weighed as metallic Cotution of' chloroform fOr ether, should yield balt, protosesqui Oxide of' Cobalt, Sulphate of not less than two grains of alkaloids. Cobalt, or Nitrite of' Cobalt and Potassium. C. Test fiar PRed Cinchotac. 100 grains of It is pften thrown down as Sulphide and the bark, treated in the manner directed in sometimes as Hydrate of Cobalt. the test for yellow cincllona, with the substitu- Principle. Fixity when heated. tion of chlorolbrin for ether, should yield not A1pplications. Estimation of' cobalt in the less than 2 grains of alkaloids. (From the precipitated oxide and in the chloride, nitrate, Di.speisatory of the U. S., 1867, p. 253.) carbonate and other salts of' cobalt, when they Ci nchonin. contain no fixed impurities (Method A). Principle. Insolubility in aqueous alkaline Separation of Co from Ba, Sr, Ca and AMn solutions. (Method B). Appl)lication. Estimation of cinchonin in MIethod A. Place the dry substance in a extractsof cinchona bark fiom which quinine weighed porcelain crucible provided with a and quinidin have been separated. perforated platinum cover. Or, in case the COBALTLCYAMSIDE OF COPPER. 193 substance to be analyzedl is a liquid, evaporate form of chlorides it is well to precipitate the it to dryness in the crucible. By Illeans of a whole as I-ltdrates, by means of so(la lye; to bent tube fitted to the hole in the cover pass a place the dried precipitate, or a portion of it, stream of hydrogen gas into the crucible. in a bulb tube; to heat the bulb to mloderate The crucible must be lheated strongly, since redness and to pass in a current of dry chlormetallic cobalt obtailed by redLucing the oxide hyldric acid gas until the metals are whllolly with hydrogen at a low heat is so finelx dixvided converted to chlorides, and no more water is that it takes fire on cominil, in contact with the given off. A long time is required to colnplete air. This tendency to take fire is specially this operation. As soon as it is finished heat marked in cases where the oxi(le of cobalt be- the bulb strongly and pass in dry hydrogen ing impure the reduced mletal is lnixed with gas until only a slight cloud of chloride of aminfusible substances. - After the crucible nmoniuml is formed, when a glass rod moistened has been allowed to cool in the atmnosphere of with amminonia water is hleld at the eild of' the lydlrogen, and has been weighed, it is well to tube. The chlorides of cobalt and of nickel ignite it again in thle sael way, or ag'ain anld are reduced to the metallic state, while the again, until the weight becomles constant. Fi- chloride of manganese remains unaltered. nally, in case it is the precipitated oxidle which After the bulb tube has been allowed to is under examinatioll, a (ucantity of water should cool in the current of' hydrogen, it is placed in be poured into the ciucible to dissolve any al- a cylinder with cold water-which has been' kali which Ilay have been retained by the boiled to expel air-so that the undlecomposed precipitate. Decant tlhis water after a while, clhlolride may dlissolve and leave thle Cobalt and treat the metallic cobalt with fresh closes (and Nickel) free. A portion of the chloride of water as long as the liquid conitinues to of manganese usually refuses to dissolve, and turn red litmus pIpeir blue and to leave a res- remains suspended in the liquor in tle fbrln of idue on evaporation. After the washiing lhas brown flakes; it may, however, be readily sepbeen completed dry the nmetal and -lagain ignite arated by decantation fiomn the far heavier it in a stream of hlydrogen. The amlount of metallic cobalt. The latter llust finally be matter dissolved out by the water is usually dried, again ignited in an atlmosphere of ll hyless than 0.2 per ceit of the weight of' the drogen and weighed. Care Iutist be taken not imipure cobalt (HE. Rose). Unless the ox- to heat strongly enough to volatilize chloride ide of cobalt has been Iprecipitate(l in pllati- of manganese. The pIocess yields accurate num vessels by Imeans of' alkali absolutely free results (H. Rose). firom silica, the metallic cobalt should be dis- Propertzes. As obtained by reducing the solved in acid after it has been weighed and chloride or nitrate in a streaiii of hydrogen, the solution evaporatedl to drynless on a xvater imetallic cobalt is a grayish black powder, bath, in order that the silica whichi containi- which is attracted by the nlagnet and is imore inates it nmay be separacted (Johnson). Ac- difficultly fusible than gold. In case the recording to Freseinius, the process yields strictly duction is made at a low heat the finely diaccurate results only wheni tlle comnpound to be vided metal will take fire ini the air and burn analyzed is free fioinl suiphuric acid andt al- to protosesquioxide, but nothing of the kind kali. He finds it inllpracticable to obtain an occurs wheni the reduction is effct ted at an inabsolutely pure product by boiliiig the iii)pure tense red heat. The powder does not decoimmletallic residue witli w;ttcr. Thlie impure iiie- pose water, even at the temperature of tallic powder, after hL;viiig been repeatedly boiling, unless an acid be present. It disboiled with water, still (coiitinues to give an al- solves readily in nitric acid( and in hot concenkaline reaction with tulrileric paper when the trateod sulphuric acid. Whben obtained by latter is left in conltact with it 1or soIne tiiiie. reducino oxide of cobalt which has been l)re3Method B. In case cobalt is to be separ- cipitated by caustic alkalies, the metal exhibits ated firom another lietal the process remlains an alkaline reaction due to alkali retained by essentially the samle as in A, only that the the oxide. The aniount of this ilmpurity is mixed chlorides of cobalt and the othier iinetal rarely more than 0.2 or 0.3 per cent, and it are operated upon, and thalit a chloride of the mlay be removedt by means of hlot water. other metal is left in the crucible, and inlust be Cobalticyanide of Copper. dissolved out with water belore the ietallic IPrincipze. Imisolubility in wvter. cobalt can be weiglled. It' thle meutal to be Applicatiorn. Estimation of Co in a solution tseparlated( be an ilkal i mlctali, care llnust be of cobalticyanide of potassiumn. Separation of taken lnot to hleat the crucible above low red- Co from Ni. liess, so as to avoid volatilizinl any of the al- Mlethod. Supersaturate the solution of cok aline chloride. It is perhaps best in this case balticyanlide of potassium with acetic acid, to effect the retluctionl in a bulb tube instead boil the acid liquor and pour into it a solution of a crucible. In the case of mlanganll se of sulphate of copper as long as any precipithe reduction niay be effected in a crucible pro- tate fitlls. Boil the mixture fobr soiie timne vided the substance to be aallyzed is a chlo- longer, themn collect the precipitate of' cobaltiride. But in case the mixture of' cobalt (or of cyanide of copper upon a filter. Finally decobalt anld nickel) anid mlanrganese is not in the colmpose the precipitate by boiling it with a 13 194 COBALTICYANIDE OF POTASSIUM. solution of caustic potash and weigrh the Oxide perOxide of Nickel. Neither the chlorine nor of Copper obtained. Calculate the amount of the mercuric oxide has any action upon tile cocobalt froim that of the oxide of copper found. balticyanide of potassium. The cobalt may (Liebig, Annalen Chern. und Phatrm., 65. then be precipitated from the filtrate as Co244.) The process is less simple and conven- balticyanide of Mercury (Liebig, Annalen ient than that lwhich depends upon the insolu- C/hemn. und Pharrm., 65. 244; 87. 128). See bility of cobalticyanide of mercury. Cyanide of Manganese, for the separation of Cobalticyanide of Mercury. mangalese from cobalt. Principle. Insolubility in water. This )rocess has been subjected to a critical Applicao. Estin. iation of Co in a solution exlamination by G auhe (Zeitsch. acnalyt. Chemn., of cobalticyanide of'potassium. Separation of 18(6i, 5. pp. 75-83), who finds that though Co fronm Ni. cobalt may be well nigh completely separatetd MlIethqd. Neutralize the solution of cobalti- froml nickel by means of' oxide of mercury in cyanide of potassium allmost, but not quite, a mixture of the double cyalnide of nickel and completely with nitric acid. There is no harml potassium and cobalticyanide of potassium, the in leaving the liquid slightly alkaline. Add a process is nevertheless ill suited for the analysolution of' mlercurous nitrate, made as nearly sis of' mixtures which contain cobalt in any neutral as possible7 as long as any precipitate other foirm. But since the conversion of the falls. C'ollect the precipitate upon a filter, double cyanide of cobalt and potassium into cowash it with water, ignite it intensely in the balticyanidle of potassium can never be made air, then redcle it to metallic Cobalt in a absolutely complete, even by long continued streanl of hydrogen and weijgh. Or, less ac- boiling with an excess of cyanide of potascurately, instead of' reducing the precipitate, sium, there will occur only comparatively few ignite it iin a. crucible in firee air and weigh as cases in which the use of' oxide of mercury as protosesquiOxide of' Cobalt. The precipitated above will be found advantageous. But cobalticevanide is white, or gray fi'ro admix- on the other lhand it is easy to convert the ture of Ilercurous oxiile, and heavy; it set- douible cyanide of cobalt and potassium comtles readily and is easily washed. The pro- pletely into cobalticyanide of potassilum by cess is prefierabll e to, that whllich depends on leading chlorine gas into the alkaline liquid. the insolubility of cobalticyanide ot' copper Henev that modification of Liebig's method (Weehler, Annlclen Chetn. und Pharm., 70, in which chlorine is employed to precipitate 256). According to Gaulle (Zeitsc/. analyt. the nickel is to be recommendedl. Excellent Cliene., 1866, 5. pp. 79, 83), this process is ap- results were, in f:act, obtained by means of it. plicable only in tie absence of chlorine com- It is to be observed, however, that the perox.pound(s. In case chlorides be present some ide of' nickel thrown down by the chlorine dichloride of inlereury will gpo down with the co- must not be ignited and weighed directl.y, balticyanide, and on igniting the Illxture sonlle since it retailns very persistently no inconsiderof the cobalt will be lost tlhrough volatilization able quantity of' alkali. - It is possible inof chloride of cobtalt.'deed, as Gaulie shows, to change the double Cobalticyanide of Potassium. cyanide of' cobalt and nickel into eobalticyaPrin cip/le. Solubility hin water and powver of nide of potassium by ileans of chlorine alone, resisting decomposition. in the same way that fBrrocyanide of potassiunmApplication. Sep aration of Co from Ni is changed to terricyanide by the use of chloand Mn. rine, but it is nevertheless better in practice eleI;hod. Add cyanlhydric acid to the mixed to change the larger part of the double cyansolution of cobalt and nickel, which mlust be ide into cobalticyanide by boiling with cyanide free from other nmetals excepting manganese, of potassiinn, as Liebig has dir( cted, and to etthen a solution of' caustic Iotash and heat the fect the completion of' the process by the chlomixture until every thing has dissolved. Or, rine employed to precipitate the nickel. instead of' cyanhSdric acid and potash, use a With regard to the use of oxide of mercury as solution of cyanide of' potassium tree tirom cy- a precipitant of the nickel, (Gauhe shows that anate. Heat tile re(ldish yellow solution to though a satisftcltory separatioli of cobalt firom boiling in order to expel tlhe free cyanhydric nickel can be thus made when the conditions acid. By this process the double cyanide of are favorable, a little cobalt does invariably go cobalt and potassium in the solution is changed down with the nickel. This source of error to cobalticyanide of potassiumn, while hydllo- would be hardly worth mentioni'ng, however, gen is evolved. But the original double cya- if thlere were no other objections to the process nide of nickel and potassium reImains unaltered. in which oxide of nmercury is used. As Rose The solution of' cobalticyanide of potassium is has previously rellmarked, the filtrate friom the neither decomiposed by chlorhydric, sulphuric precipitate produced by oxide of mercury is nor nitric acids, nor by potash lye, either at apt to become turbid immlledlately after it has the ordinary temllperature or on boiling. From passed through tle al)er, and to deposit a the mlnixed solution the nickel may be precipi- yellowish whllite ite epitat on cooling. This tated by means of oxide of mercury as sesqui- precipitate also contains a minute quantity of Oxide of Nickel, or by chlorilne as black cobalt, whence it would appear as it' the small COCHINEAL. 195 amount of cobalt which goes down with the how nuch of a solution of bleaching powder nickel when oxide of me'lcury is used is in the was required to decolorize the decoction of a form of a dlifficultly soluble compound of' co- known weigiht of cochineal; thie value of' the balt and cyanog)en, probably in part cobalticy- bleaching pow(ler solution beino (ldeterinlel at anide of nerc(ury, some of' which remains the moment of use by testing it against a spedissolved at firs-, but afterwards separates in cial sample of cochineal kept as a type or the filtrate and makes it turbid. The concep- standard. According to Scliitzenberoer (loc tion of H. Rose, who ascribed the turbidity to cit, p. 359), the process was faulty, since the the presence of a (1fficultlv soluble basic cyan- chlorine acted upon other organic matterls benide of mercury, is nanitestly incorrect, sides the coloring substance (elarmnitlic acid). Cobalticyanide of 2Zinc~N. P l-'rinci)le II. Pow ir of the colorin(r matter PrirIC'iple. D)ecomposability by acids to form insoluble compounds with aluminumi Application. Separatioii of( Co fi'rom Zn, and with lead. Mlethod. ecidulate the solution of the two AIjplications. Valuation of cochllineal, etc. metals witIh chlolrlhvdrie a(cidl add as mnuch of a Method A. Determnine how manly volumes solution of goood commllercial cyanide of' potas- of a standard solution of alunm are required to sium as is required to completely redissolve the precipitate completely the coloring matter in precipitate wllich forms at first, taking care to anly given samlple of' cochineal, and compare use a distinct excess of the cyani(le. Boil the the result with that obtained by operating solution for somle time with occasional addition upon a standard sample (Anthon). of a drop or two of chlorhydric acil, but inot Mlo ethod B, Instead of' aluln, as in A, Bloch in sufficient quantitvto imake the solution acid. employs a standard solution of' neutral acetate Finally Iix the solution with an excess of' of' lead, which precipitates carmliinic acid readchlorhydric acid, set the flask in an oblique ily. An objection to the process is fbund in position and boil unitil the coballtic anidle of' the fact that the lead salt is liable to precipitate zinc which is precipitated at first has all redis- other organic substances besides the coloring solved, arinl the whole of the eClanhydrllic acid matter. not comlbined( with tle cobalt is expelled. Prinociple III Solubility in ammonia waAdd an excess of soda or potash lye. and boil ter. until the liquid is clear. The whole of' the co-. lpplication. Assay of carmine lake. balt is now in the fblrm of Cobalticyanide of Po- l/let hod. ]Heat the lake with ammonia watassiumT~, while the zinc is in the form of zin- ter until the coloring matter has dissolved. colcate of'sodiuln. Precipitate the zinc as sulplhide, lect, wash and dry at 1000 the insoluble and the cobalt. as Cobaltieyanide of' Mercury. residue and weigh it. The separation of' the two miettals is said to be Princifile IV. Colorific power. complete, andl the process simple. Applications. Valuation of cochineal, etc. Cobaltite of Cobalt. See protoses- (1\Metheods A and B). Use as an "itldicator" in quiOxide of Cobalt. processes of' akalimetry (Method C). Cobaltous Salts. Mlethod A. The method of' testing cochiP ici pe. Oxidability of;, with precipitation neal or(inarily employed in lye houses and of the sesquioxide. See sesquiOxide of' Co- print works consists either in dyeing a dlefinite balt. See also Chlorine. quantity of morldante( cloth with 1 gaLlnnle of Cochi neal. cochineal, as in testing Maddler, or in printing'irc'le 1. Power of tIhe coloring matteri upon woollen a known weighltof the cochineal, (carininic acid) to redluce oxygen compoutlns. groumnd ald mixed as it wotuld be for applicaApplicatiors. Valuation of cochineal and tion in iactual practice. In either case a silianalagous substances, such as lac-dyl, lac-lake lar sample of' cloth is dyedl or printed with an and kelrmles. equal -weight of' good cochllilneal kept as a ieAthodlTs. stsandalrd samlple. This Illethod is simple A. Oxidlatiol by Fericyanride of Potlassium in and easily executedl, and is esteemed. It does alkaline soltuio,. Dissolve one (rin. of the pow- not give accurate iresults, however, in case the dere(l cochineal in 36 gri's. of a weak solution cochineal has been mixed with the coloring of caustic potash, mlix tle solution with 24 rlrins. inatter of Brazil wood. To detect the presof water and pour in a standardl solutioll of' fbr- ence of' the latter pour solme linme water imlto a ricyanide of potassliuln, drop by dlrop, fioml a bu- dilute decoction of the cochineall. If' the cochrett;e until the reddish p)urple color of the liquid ineal is pure the liquid will beconme comllaLs lchalnel to briownish yellow. To piepaire pletely colorless, but it will retainl a tolerably the stumlard solLition d(issolve 5 grins. of the fer- intense violet tint in case any brazilin is ricya nide in water, and dilute to the volume of present. (Persoz.) 1 litre. The p)rocess has merit. (Penny, citel 3lethod B. Weigh out 1 griln. of the cochbv Sehiitzenlbelrger in his Matibres Colorantes, ineal to be tested, and 1 grin. of' a good 1867, 2. 359). sample of cochineal kept as a stanldard, and B. Oxidation by Chlorine (applied in the'boil each sample by itself' in a litre of' water forill of bleaching powder). An old method, (luring the same space of' tine. Filter into devised by Robiquet, consisted in determlining litre jars and dilute each filtrate to the volume 19G COLOQPJM ~T.Yof I ]iti e; shake the solutions, pour an equal of the color permits the operator to compare (quantity of each into the tubes of a Colorime- the products of several titrations one with the ter, an(d determine how much water munt beT other. (Johnson, American Jom'rn. Sci., 1863, added to thle (leeper solution to bring it to the 35. 282.) Cochineal cannot be used in the sme hue as the other. presence, even of minute quantities, of salts Method C. The use of eochineal as an in- of' iron. dicator has already been sufliciently explained Cotorrilet:ry. under Alkalimetry, p. 19. Besides the merit A terln applited to processes f analysis, in of distinctness and extreme delicacy which which the aniount of a colored substance in a sopermits the use of much more dilute solutions lution is d!tcriin ned by observing the intensity than can be employed with litmrs the eindift of the color. An instrmnent kniowi as a Colorferenee of cocliineal to carbonic acid is a great imeter is employed for m easuring the depth of advantage. loreover the solution, wheni pre- clor, and the process consists either in compared as described under Alkalinetrry, may be parhing the solution to be tested with a standkept for any length of time in closed vessels arl solution of thle substance, and diluting the without decolorization or alteration. Accord- stron er colored liquid until the two solutions ing to Luckow, cochineal is quite indifferent. a.re alike; or in comparing the solution to be to carbonic or sulphydrie acids, since carminic tested with a nmnber of disfierent standards aciid is stironer than either of them. I his is until one is found witih which it agrees; or in practically tine fbr solutions of considerable varyingm the de' pth of the solution of the liqstreng1th. Hence a starldard alkali for tcchni- uid to be tested until it exhibits the same ineal ainalisis nnav be made by simply dissolving tensity of color as the norrinal liquid, and then a known weiglht of pure carbonate of sodiumm imeasuring the 1depth of the stratunm; or in in a definite volune- of water, and from the neutralizngr the color of' the solutiom to be standard solmtion thus obtained a standard acid tested by mneans of a plate of glass or a shtn-c miay easily be prepareld. - In effectin;g the of' 11uidf of comiplemenntary color. In this last eieutralizitionr it is not necessarv to expel car- ease the instrument einployed is called a Coimboiic acid by boilin,, as it is when litmus is plementary Colorimeter, andl the depth of' the,seil.,'Still the presence of carbo-nie ackid does stratum of liquid needed to obliterate the comtend to obscure the sharilmess of the final re- plementary color is measured, in ordler to deaetion, and it is best to eimploy caustic alkali terminc tie ainmoust of the substalmee sought for tlhe stadlard liquor, as is explained under for. Alkaliumet.'y, espleciallyl in aics nivvestigations. Coloriiaetrie metlhods are employed for the The influence of carbonic acid is seen at once v'aluati on of coloeihne nmattem's such as Indigo when a caustic and carbonated alkalil are oper- anl Coclhineal; for the estimation of' Brominne erated upon silde by side. With the caustic and Iodine, cobalt, nickel, chromiumn, ir n alkali thie point of' neutralization, or, rather of' (see Acetate, Chloride and Nitrate of' Iron), supersat.uration, is shown by a prompt and and the'Iarbon in cast iron, and particularly dee'ssive chaimre fiom a tint in whisch orangre fbr the estimation of Copper. Since the depYredoiinmates to one in which the orange dlis- scri'ptiois of the processes have been made appears andl violet is most marked. But in with ref~rein ce to the estimiation of copper or presence of' carbonic acid the change is some- soime other special substance, it will be best to wh.at gradtual, and though a red color is pro- state them here in the saie narrow sense. duced it is nmodl.fied by ai orange tint.even in The niethods evidently admit of apI)licatioi presence of a large excess of alkali, so that in the analysis of v-ery many substances which there is s >metines a disagreea ble uncertainty foel' eoloried solutions. as to the point of' neutralization. When,. caus- A. J[c(cqeeltmt's copcer test. To preplare tie alkals is used a trifle less of' it will be fboiid the standard solution of' copper dissolve 0.5 needful to neutralize a given volune of' actd grin. of pure imetallic cop)per in nitric acid, than is required of' a carbonated solution,. and spersaturate the liquid vith aminnonia water no doubt will exist as to the point of satura.tion. and dilute to the voluise of' I litre. Measure - The indifference of' cochlineal to carbonic off 5 c. c. of' thle liquid into a glass tube, andl acid is a glreat advantage in nmee analyses, in seal the latter at the lamp. Dissolve in nitric that the tine consumted for effectinlg neutrali- acid a quuantity of' the substA;nce to be an,-lt zation is without influence on the result. lyzed, supers;aturate with amumionia as before When litnmus is used and the point of' uietral- arnd dlilute with water in a graduated cylinder ization is reached, a short exiosure to the air to the volrine of 200 c. c., or to 150, 100 or 5G suffices to redden the licpmid again. If the e. c., if' need be. Measure oft' 5 c. c. of' tilhe operator is obliged to proceedl slowly, hlie will dlilutedl liquid into a long tube, whimch has been. require somewhat more alkali than when he graduated to tenths of' centinmetres anid iwhicll operates rapidly, for a portion of it is neutral- has the samie diameter as the tube th:t cmsized by carbonic acid, from the atmiosphere. tains the staldard soluti:on. Set botl tiheWith coehineal tihe result is independen; of tubes in front of' a sheet of white paper, amntu the small amount of carbonic acid that can dilute the contents of' the graduatedl tube withl come from the air. Moreover, the permanence water until the same color is exhibited by the COLORIMETRY. 197 lijquids in both the tubes. - Since the It is not easy, for example, to arrive at a satquantity of copper, 0.0025 grin., in the stand- isfactory result when liquids containing 0.1 or arcd solution is known, and siice the liquid 0.8 rini. of copper are compared with Jacqueunder examination has been dilutc l to a (dec- lain's standard liquid, which contains 0.5 grm. terinined volume, the amount of coppeC in the If quantities of 0.1, 0.2, 0.3, 0.4, 0.5, 0.6, 0.7, weighed sample can readily be calh.ulteied fi-aii 0.8, 0.9 and I grinm. of pure copper are disthe amount of water used in the process of di- solved in nitric acid, supersaturated with amlution. If, for example, 50 c. e. of wa ter ihad monia and diluted with distilled water to 200, to be added to the 5 c. c. of liquid in the 4900 600, 800, 1000, 1200, 1400, 1600, 1800 graduated tube, every 5 e. c. of' the diluted iand 2000 c. c., it will b ue /u nd that 5 c. c. of liquid will contain 0.0025 grin. of colper, like the solution prepared firom 1 grin. of copper the 5 c. c. of' standard liquid in the sealed when compared with 5 c. c. of' tile solution tube. So that the 50 c. c. will contain 0.025 prepared with 0.1 grin. will exhibit a difrin. of copper. And if it happe ned that two ferent llue tone. Te color of the formoer grinls. of ore were taken and that the amRio- will be more " fieryv " than that of the latter, ni:ical solution was diluted to the volume of and this peeculialm:itv will diminish thiough 200 c. c., it woul(l appear that theil sample con- the entire -erites of liquids above named, until tained 0.1 grin. of copper. - The only oh- in the solution which contains 0.1 grin. there ject in sealing the tube which contains the will be seen a tinge of' greenish blue. If' only standard solution is to keepl the Iattei firom a single standard liquid were used some diffievaporating. It may sometinmes be more con- culty would be met. especially by unpractised venlient to have the staundard liquid in an open eyes in attemmipting to compare with it liquids tube. Thus in case thee lic(uil to he tested is which contain more or less copper. The iiqlighter colored than the standlard liquid, p'o- uidts showing tIle greenish blue tinge would be eeedl:as follows:- pour 5 c. c. of the standard held to be deepeIr colored than they really are. liquid into the graduated tube and 5 c. c of To avoid this diffieculty v. Hubcrt preparis the liquid to be testedl into a short ungrad- two stanidard liquids, the one ifrom 0.! rin. of uated tube of tile same diameter, and dilute copper and thIe other from 1 rmi., and dilutes the contents of the gradua tc1 tube until both the tfrmer to 200 c. c., and the latter to 2000, the liquids have the same color. Note the so that the relation of 5 c. t. o 0.0025 grin. quantity of water used and calculate how may remain unchanged. In case thIen a difmuch copper is contained in each 5 c. c. of the ferent tone of color appears on diluting tihe dlilutedl liquid. The flrther calcula.tion will liquid in the graduated tube, and especially if then be as above. (,Jacquelain, Comptcs this occurs at the very comnmencement of the Reendeus 8- Juin 1846, thiroiih Keri andc v. process of' dilution, thile two standicrd liquids HIubert.) The process is said to be exact and may be lnixed in the short tublie in saec1 prokeasy of execution. It may be employed fbr thle portions that the color of' thce mixture shall a.nalvsis of' regulus, andl alloys such,a,s brass, appear to the eye identical wit h thit of' the bronze, pack-tong, aidl gold andl silver cmin liquid in the grmacuated tube. If the liquid in and ware. It can hardly be aippied t t thIe the graduated tube shous a brighter blue tmian valuation of slags and ores which containi iron the other, put more of the solution of 1 gril. unless special pains be taken to remove the of copper into the short tube, but it' its tone latter. (See below.) tendCi toward greenish bluem add miore of' the B. Von IHuberiCt's mod'fication if Jacque- solution of 0.1 gim. of copper. lain's test. Accordinig to v. Hubert, several In preparing ores and pi'roiluc'ts of the smelt impor'tant considerations have been neglected works fbr analysis, take care to reduce them to in Jacquelain's description of his process. the finest possible powder. Sla, in particular, The internal diameter iand lengtl of the tube imust be finely powdiered in oi'ier that strong are not matters of inditil'rence. Any given cllorhydii c acid may decomo se then comblue liquid wouli necessarily aippear dlrker in pletely. Let the mixture of' powder and acid a wide than in a narrow tube, since a thicker stanid for some hours at a moiderate heat, or in layer of' it would be looked at. The tube thIe case of' ores, until the sulphur which sepaougiht to be so inarrow that the li(jquid shall rates is no longer brown or green colored, but appear so light colored that the comiparison of yellow. - Tihe oxide of iron which fhlls the blue tints can be readily made. An inter- when the acid solution of an ore is supersatuial diamneter of' I c. in. is well suited fbr the ratei with ammonia water carries down a cerp)uri)ose. The tube should be graduated to tain amount of copper in insoluble combination, 35 c. c.; it is well to have it 46 c. i. long, especially when the proportion of'copper in the in order that there lmay be phlemty of room to liquid is large. The copper thus dragged down shake its contents after the addition of' the may amount to as much as 0.9 per cent in a water. - A single standarci solution is 20 per cent ore; it cannot be removed friom hardly sufficient, for certain differences in the the oxide of iron by long continued washing tone of' the blue color are noticeable NhLen the with hot water. To avoid this loss treat the standard solution contaims miuch mmore or munch moist, thoroughly washed, precipitate upon the less copper than the liquid to be examined. filter with a very small quantity of' concentrated 198 COLORIMETaY. chlorhydric acid, again add an excess of am- rest for a mininute, note the number of c. c. and nionia water to the solution thus obtained, col- tenths of c. c, of water which have been used, lect the precipiitate upon a filter, wash it with and again add water drol) by drop, until tile a little hot water, aind adld the filtrate and liquid to be tested ap-)pears a trifle lighter colwashinrs to the first amnmoniacal solution. ored than the standard. Again note the The (1muantity of' the substance to be weighled amount of' water used and take the minean of out varlies with tihe amount of copper contained the two observations as the correct reading. in it, — 4 or 5 grins. will be enouhji of' an ore The calculation has been explained in A. of' 0.1 to 2 per cent; 2 grins. of an ore of 2 In case the ore contains cobalt or nickel add to 20 per cent, and I grin. of an ore of' imore an exccss of' powdered white miarble to the than 20 per cent. - The first dlilution of the acid solution to pr'ecipitate thle copper, while solution should doepend upon the dleptL of its thl coaltt and nickel are left in solution. Colcolor. In general, the solution of' a 0.1 to 2 lect tie precipitate, dissolve it in chlorhydric per cent ore mary be diluted to 150 or 100 c. c. aci( ald( proceed as above. To remove manand an ore of more than 2 per cent to 200 e. ganese, place the anmmoniacal solution in a c., —in a graduatel cylinder. Care must of porcelain dish, mlddt carbonate of' potassium course be taken to preplare the standard sola- andI heat the mixture fio' several minutes. tions and the solutions to be testedl at sonim The ian mnanese will go,,( lown in the fborm of one common teinperature as nearly as may beV Crnbonate while the copper remains dissolved; To this enil it is well to cool the liquids 1)y iltel the blue solution:nid proceed as above. leaving the vessels whic h coiitain them tfor liIf'1 The process has the Inerit of cheapness and an hour or so in running water, or ill freshly accuracy. (Vou Hubert, Jhukrbnc h i. k. geolodrawn well water. Since the nuniber of' c c,.q,'ch. Reichsanstalt, Wien, 1850, 1. pp. 415, of' water used is directly protportionml to the o562.) per cent of' copper in the weiglied samnple, it C. Bishof's modi/icatioo. A cheap and bfollows that if' 2 grins. of a 60 per cent oire were sinple apimratus dcevised by G. Bischof, Jr., taken, if' the solution were diluted to 200 c c. foi tr tcilitatin?' the comparison of copper soluand 5 c. c. of' the diluted solution measured tionis andl other c(l)ored solutions, is figured in out for the test, their would be obtained a col- l)oigq!er's Poly'ech..Jorot., 184. 433, and untn of' liquid equal to 60 cc. nBut it wouldt Zeitsch. (mlawl/I. C(hem., 1867, 6. 459. be well hiigh impossible to manipulate with L). Iei e's test jfir coppe' slags. Heine was such a tube or to mix the last drops of' water the first who publislhed a description of a colorthoroughly with tlhe rest of the liqluidl. Hence, iiiietiric assay of copper. (See Bergwerksfor all oires that contain over 40 per cent of J'eutld, 1839, 1. 33 andl 17. 405.) His pumcopper, no more than 2 c. c. of the liquid to be po.se wvas to ihave a ready method of detertested should lte ineasured out with a pipette mining the, small P1roportion of' copper in the into the graduated tube; but for ores of' less filmrnace slag of the works at Mansthld, but than 40 per cent coipper 5 c, c. of the liquid the procqss has been funimd usetul for testing should be taken for the test. slags in mam othCer localities. The details of In minaking the compuparison between the it are as f'ol!ows: — A number of' standardi( sostandard liquid and the liquid to be tested, it lutions de 1)tlarcadl by dissolving a known is best to hold tile two tubes parallel with one wei,,ht of' pre copper ill nitric acid, supersatanother in tihe riht hiand betfbre a sheet of' urating thte solution with nammonia water and white paper, while with the left band they pa- diluting with mieasure(l quantities of' water to per is pressed firinly av ainst the tubes, But any desired extent, Tihese solutions are kept in order to avoid( distulrbance from white in a row of glass stol)ppered bottles of' colorless stripes, due to the glhass, which would be seen glass, of precisely the same capacity and of if' the tubes were hcld vertically, it is well to quadrangular shape. In the first bottle there hold the tubes in a slianting position, at an an- Imay be, say 0,0041 gmn, copper to 25 c. c. of gle of about 450, thougih still parallel with one water, in the secold 0.003, in the third 0.002 another, In case the liquid(i to be tested is andi in the tfiurth 0.001 grin, ThIe intensity of' muclh darker than the standard solution, it the blue color will be proportionate to the should first be diluted to such an extent that it aiiouimt of copper in the solutions, and by shall be neeiflv of the color of' the standard,'oompa mr an' other solution with this series though still mnanifistly darker than the latter, of' stantlda. rd'l the amiount of' copper contained Then observe wlethier tmhe tone of color in the in it m ay be infcrmredl fiomi its color, and the two liquids is the same, and if it be not, pro- aimount of' water that has been added to it. ceed to adjust time standard solution as above It is essential that the liquids shliould be very directed, When the standard has beeni dilute, otl'-rwise thie color will )e- so intense broughlt to the required tone proceed to dilute that no just coaMr'piso ns cnm be made. firther the liquid to be tested, adding tlhe A weimlhed quantitv of tle slag was treated water at last, drop by drop, until time color of with concemtrmatetd nitric acid, the solution was the two liquids is as nearly alike af it can he, supcr satmmratedl with ammonia. water, the preand the liquid to be tested still left a shahe cipitatc(i hy(ldates of iron and alum minrmnm were darker than the standard. Leave tihe t.be at allowed to settle or were removed by filtration, CO_,ORIMETRY. 199 the filtrate was diluted with water until it had should be kept of the quantity added after the the same volumle as the standard liquids; it acid liquor has been neutralized. Nitrate of was then poured into a quadrangular bottle, copper yields a mnore intense blue with ammosiilmilar to those which contained the stan(lard( nia than sulphate of' copper. The blue of' the liquids, and its color compared with that of the solution appears to be more intense when held several stan(lar(ls. The value of the liquid before a gray wall than before a white one. under examination was (ledluced fiom that of After a while the solution becomes greeniil, the standlardl solutio.n, which it most nearly and loses its intensity. resembled. If need were, the solution tlnler The processes of Heine and Jacquelain have examination was diluted with water until it been applied by Eggertz (Berg und Hutten resembled sonle one of the stand(ar(l liqluids. Zeitun, 1862, p. 218,) to the estimation of copIn that event only the ordinary volume was per in iron and iron ores. placed in the bottle for comparison, and the E. Earlier colpper test of Dehms. Place whole of the solution was finally ineasllred in a eleven. not too narrow test tubes, of similar gral(uated cylinder. During the examilnation dialmeter, in a rack and fill them with solutions the bottles were placel in agood lilht between of atlllloio-sulphate of' copper, of. strengths a window and the observer. varying froml 5. 6, 7-15 equivalents of copExceedingly poor slags, no matter whether per, to the litre, in terms of' milligrammes, they have been decomposed by fision with car- (H = 1.) Pour the solution to be tested into a bonated alkali, or by acids should be filtered, test tube similar to the rest, and place the tube after the ad(lition of' acil in or(ler to remove between each pair of' the standard solutions silicic acid, andt treated with sulphydric acid to until its proper l)lace is (letermlined. In this precipitate the col)per. The precipitated suil- way there will always be found two limits bephide may then be roasted, the residue tween which the real value of the solution dissolved in nitric acid, an(l the solution super- must lie. Blue glasses can be found in conlsaturated with ammonia. It will not do to add mlerce, of a tint so nearly like that of the ammlonia imlmetliately to the original acid so- ammln-onio-copper solution, that they may be lition, since much copper would be carried emtuloyed with advantage as standards ot conndown withl the slitmy precipitate; wlhen much parison instead of solutions of known strength. iron is present the iton and copper may be (Dellms, Zeitsch. analyt. Client., 1864, 3. precipitaLtel together with sulphide of sodi- 218.) For the later methods of Dehmls, and nlm, and the sullhi(le of iron afterwards dis- for A. Mueller's copper test, see below. solved out with dilute sulphuric acid. Or the F. Herapath's method (!f estimiating Iron, precipitated hydrate of iron may be redis- C'yanogen adl Sul)phocyao?/ qen. For the analsolved and again precipitated, as in Hubert's ysis of waters containing minute quantities of process above. - 1Or the slag may be de- iron Herapath employs a process founded composed by Mohr's (Zeitsch. analyt. Chenm., on the colorific power of fkrrlic sulphocy1. 143) process, as follows: Place the powdler anide. A standard( solution of perChloride in a porcelain dish, together with somIe sulphu- of Iron, containing a little less than one one ric acil, water and nitric acid, cover the dish, hundredth of a grain of' metallic iron per evaporate to dryness and heat the residue tin- cent, is prepared by (lissolving 1 grain of' iron til non more funmes of' sulphuric aci(l are visible; in chlorby(lric acid, with the addition of a litthen treat the residue with boiling water. tle nitric acid. evaporating nearly to dryness Sulphate of copper together with a little iron and diluting to 10,000 gr. measures with diswill go into solution, while insoluble basic sul- tilled water at 15.5~; fi'ont this solution other phate of' iron, etc., will remain in the residue. standard soltutions of difflerent strengths are The process furnishes useful approxiimations, prepared as required, and colored by the adand is still somewhat extensively used tbr test- dition of a few drops of sulphocyanide of' potingr slafs and shales which contain but little assiurm. A convenient quantity of the water copper; it is less well adapted, however, for to be examine(l, generally half a gallon, is testing richer materials' (v. Hubert; Kerl). evaporated to dryness, and the saline residue Heine (Be'ygwerk-.fireund, 17. 405) clainms that dissolved in chlllorhyldric acid. The solution is for substances poor in copper, such as slags, boiled with a fbw drops of nitric acid, filtered his process is preferable to v. Hubert's; with to separate silica, etc., and( the iron precipisuch materials he can det;rmnine the copper ac- tated as a hydrate, by means of ammonia. curately to 0.03 per cent, while v. Hubert can The hydrate of iron is collected Upon a filter only be sure to 0.3 per cent. According to and well washed with water, after which it is Heine, the oblong or quadrangular form of the dissolved in the smallest possible quantity of bottles is a point of' considerable importance. chllorhydric acid, and the solution placed in a According to Miiller (Bergwerk.sfreund, 18. phial or tube of known capacity. A fbw 118), the color of an ammnmoniacal copper solu- drops of a solution of sulphocyanide of potastion depends very much upon the amount of siurn are then added to the iron solution, a-emnomlia present. For exact experiments a an(l the mixture is diluted with water until it solution of ammonia of known strength should reaches a mark upon the tube corresponding be prepared (see Acidimletry), and an account to 1000 water-grain nmeasures. The depth of 200 COLORIMETrY. tint of the diluted solution is then compared adde(l to an a'queous solution of cyanhydric with that of several standard solutions pre- acid, and the mixture is heated with the addipare(e as above described, contained in tubes tion of flowers of' stlphur; or when a mixture of or phials of similar (lialneter, in which certain cyanhydric acid, aliim onia water and quinquiknown quantities of' iron, ranring friom the sulphi(le of amiulonium is gently heatedl, the one-tholsau(lthl to the one-fourth of' a grain, cyanlllyllric acid is soon converted into sulphoare contained( in the same bulk of solution. cyanite of' allnmoniium. The substance to be At the inoneiit of comparison tile tubes are tested is treated either by distillation with placed against a sheet of' white paper and held dilute sulphuric acid, or in any other approbetween the eve and diffused daylight. By priate wax, so that an aqueous solution of cyoperating in this way the one-thotusandth of a anhydric acid slhall be obtained, and the latter grain of iron per gallon lmay be estimated with is converted to sulphocyanide of amnmonium, the greatest readiness. For small quantities as has been explained. After such converof material the process commends itself for sion, the liquid is carefully evaporated to dryconvenience and accuracy. In soilie ness, the resd(lne is dissolved in boiling water, cases it may be found preferable to employ but the solulion filteredl andl placed in a colorimeone stan(lalrd solution; in that event the p!'o- ter tube,, where it is treated with a slight exportion of' iron is determined by Ileasuring cess of ferric chloride. The tint produced is the quantity of water which it required to then coinllpared fiom tiime to time with that of lighten tllhe tint of the liquid tested so as to a liquild in another colorilneter tube, containrendler it identica:l with that of the stan(dard ing a weak solutioll of ferric chloride, to which solution, or vice versa. ('. J. Ilerapath, a stan(ard solution of sul)phocyanide of ammoJourn. London Chenm. Soc., 1853, 5. 27.) nium, or sulpliocyanide of potassium, is gradThe samne princih)le has been employed by ually ad(led(, until the two correspond. From Herapath, (Chemlical Gctzette, 1853, 11. 294,) the alllount of sulphocvanide solution thus exfor the estiiiiation of iron in tile ashes of' plants pentled, that of' the cyanhydric acid in the and animal matter, in guano and other substance analyzed is calculated. According manures, etc. The ash or other liatter is to Herapath tle process yields excellent results, treated with boiling chlorhydric acid and the and is specially valuable where minute quantimixture evaporated to drlyness. The residue ties of cyanogen are to be determined. By is mIoistened with strong cl-lorhydric acid and usin( small sized tubes and operating with warmed until everything soluble in the acid care, the three-thousandth of a grain of' cyanhas dissolved; water is then poured upon the hmydric acid may be estimated with the greatest mass and the silica separated by filtration. exactness. - When the process is emThe acid filtrate is heated to boiling after ployed fob estimating sulphocyanide of potasaddition of a few drops of nitric acid, and sium in saliva, the latter should be evaporasupersaturated with anmonia water, whlli(ch pre- ted to driynes on a water bath, anti the residue cipitates hydrate of' ilon, either pure or corn- treated with dilute chlorhydric acid. The filbined with phos)phoric acid, and usually more tered solution is placed( in a colorilmeter tube, or less contaminated with the phosphates of a drop or two of a solution of ferric cllloride calcium and niagnesium. Collect the precipi- is added to it, and the mixture is diluted with tate on a filter and wvash, (ldr and weigh it. water to the mark. The tint is then compared Then redlissolve it in boilinig chlorhydric acid with that of amn iron solution, to which a standand transfer thle solution to a burette. Pour ard solution of' sulpllocyanide of ammonium is 5, 10 or 20 measures of the solution into the added, as above ldescribed. (Plerapath, loc. cit.) colorimeter tube, add anl excess of sulphocy- G. Houllon's lztliUo test. The colorimlleter anide of potassium, andt dilute the liquid to the of Houolli-Lkalillldiere (Description d'uz colormnark upon the tube, which immay correspond to imne're, Rotuen, 1827) consisted of two cylin500, 1000, 10,000 or 20,000 water grain incas- drical tubes of thle same glass and of the same ures. The tint is thell compared with that diameter anll thickness. The tubes were of produce(t by the gradual addition of a stand- about halft' an incl bore and 13 or 14 inches ard solution of' f'terric chloride to water imllreg- long. The tubes were closed at one end, and nated with sulphllocyanide of potassium, and at a dlist.ance of about five-sixths of' the lemigth contained in another tube of' similar dimnen- fi'oiii the closed endl they were divided into sions placed besiide the first against a sheet of two parts of equal capacity, the second half white paper. From the number of' imeasures being g'raduiated into 100 divisions. To reof the standard iron solution that ar'e cxpen(led ceikve these tubes a small wooden box was prein bringing the fluids to a uniform tint, the paried, and blackened upon the inside. This amount of iron in the solution to be examined box had two contiguous }oles in its upper is ascertained. part for the receiption of the tubes, and at one The same principle has been applied also by en.d, illlmmediately behindl the tubes, there were Herapath (Chemical Gazette, 18a53, 11. pp. two rectanglular slits corresponding to the (ti295, 296) to the estimation of' cyanogen, cytan- amleter s of' the tubes. At the otller cdl( of tlle hydric acid and sulphocyanhydric acid. When lbx, fi('illg the tubes, was -in ey e-hole, so that sulphide of ammonium and ammonia water are by holdlinl the box to the lighllt, andl look co)PPEr. 201 ing at the tubes through this hole, any differ- Copper may be determined as metallic copence of hue in the colored liquids pllaced( in 1per, or as Oxide, Carbonate, Sulphide, or the tubes could be readily appreciate(l. Sulphocyanide; by various voluimetric proThe process of testing was as follows: Draw cesses depending uponi the (leoxi(lationi of a fair sample of the indigo to be tested, reduce Copper Salts by reducing ag(ents; aind by it to fine powder by trituration an( sifting. processes dependling upon the color of its soWeigh out 20 graiils of the powder, place it in lutions (See Colorilnetrv). Descriptions of a dry flask, pour upon it 400 grains of concen- the various methods of assaying copper ores trated sulphuric acid of 1.845 sp. gr., and in the dry way will be fobnd in the treatises Iheat the mixture to 38~ to 430 for about an of Kerl, Percy, and Mitchell. Compare hour, with occasional shaking. In the same Watt's Dict. Chenm., 2. 63.' None of these way and at the sanie time treat 20 grains of a dry assays come fairly within the scope of standard sample of indigo, which is kept for the present work, since the results obtained the purpose of com-parison; when the indigo by Ineans of thenl are, at the best, mere aphas dissolved let the liquids cool, an(l pour proxinations to the truth. each solution into a separate two-quart bottle. Principle I. Insolubility in dlilute acids Wash the matter which adheres to the flasks when in presence of metallic zinc, iron or into the bottles, and add' enough water to fill cadmium, and when subjected to the influence the bottles. Shake the bottles thoroughlly, of a galvanic current. [Compare Copper mIeasure out 10.000 fluid grains of each solu- Salts.] tion into tall beakers or cylinders, and let the Applications. Assay of copper salts and liquids settle. Pour a portion of the clear so- ores. Separation of Cu from other imetals lutions into the colorimeter tubes to the 0~ not precipitated by zinc, cadllniull or iron. mark, place the tubes in the holes in the box Notably fi'om Fe, Zn, lMn, Ni, Co and the, and look at themn through the eye-liole. If a inetals of the alkalies, alkaline earths and dlifference in the (lepth of color is observed earths. Also from Bi and Pb (Method 1, B). aldd water to the (leeper colored liquid until eI1ohtod 1. Precipitation of the copper by the contents of both the tubes exhibit tlhe saine Zin)c. tint. After each addition of water close -the A. The copper must be either in sul)lphuric tube with the finger, andl shake the liquidl thor- or clhlorhydric acid solution; in case nitric oulghly. The amount of water added is finally acid be present it must be expelled by evaprea(d off from the graduated portion of thle orating the solution with sulphuric or chlorhytube. dric acitl. Place the solution, which should II. Mlueller's Complenrentary Colorimeteier. be tolerably dilute, in a weighed p)latillumll A principle somewhat (litlerent fiom that of dish, throw in a lump of pure zinc an(ld acidtnthle methods thus far described has been eml- late the liquid, if need be, with chlorhydric ployed by A. Mueller (Journ. prak/t. Chem., acid(, so that there llay be a mloderate evolu1852, 60. 474; 1855, 66. 193; 99. 337, 366, tion of hydrogen. But if the solution is alalso in a special pamphlet entitled Das Comn- ready so acid that the evolution of hydrogen iIementdar-Colorimeter, Chemnlitz, 18 54. Fur- is violent, dilute with water until the efterther, Zeitsch. analyt. Chem., 1863, 2. 143; vescence mnoderates. Take care to cover the 1864, 3. 407). Instead of comparing similar dish with a watch glass, in order that no parquantities of two liquids, as above, Mueller de- ticles of' the lituid may be lost.; The separaterlnines tlhe de(ree of intensity of the color tion of copper begins at once, a large proporof a liquid by findling how (leep a layer of it is tion of it beingr ldeposited upon the platintum requiredl to neutralize the color of a glass in the form of a spolid coatinii, while another plate- made of glass so colored that it is portion separates in red, spongy masses. If comllplemlentary to the color of the solution to the solution be concentrated the proportion of be tested, — and then mneasurimng tile thickness thle loose, spongy precipitate will be larger. of the layer. The process of Miiller is There is no need of heating the contenlts of evitdently one of great nmerit. It requires a the dish, though tile deposition of the copper special, though sinmple apparatus, which umay would be hastened by the application of heat; be obtained of the dealers in (Germiman chemi- but there must always be enough firee acid cal wares. Figures and descriptions of the present to keep up the evolution of hydrogen. app:Lratus will be found in the original pape'rs After the lapse of an hour or two the whole of' Mueller, cited above. Without the aid of of the copper will have separated. To make a figure it would not be easy tc describe the sure of this point take out a few drops of the process clearly. supernatant liquid frorm time to time, and test I.''le later processes of Dehli's, depend thelmm with sulphuretted hydrogen water; not upon the same principle as the process of' A. even a brown tint should be imparted to the lMiiller. 1)escriptions of them, and firgures of liquid. Prove that the last particles of zinc tlhe aipp:ro:tus required, will be found in Fres- have been dissolved, by feeling for hard lumps emlius's Zeitsch. analyt. Chem., 1864, 3. pp. with a glass rod, and observinr that no further 2 19. 494. T hl'lis a~qhurate s also can readily be evolution of hd'(lrogen occursi on adding soime obtained from Germlal:y. chlorbydrie acid. Then press the spongy 202 (COPPER. copper together with the glass rol, d(ecant the phuretted hydrorgen. Immediately after the liquidl andt ilnineldiately fill the dish with boil- precipitation collect the copper on a filter, ing water, aoain lec ant, add more water and wash it rapidly a;ril dryv it on blotting paper at repeat these operations until the washings are no* too high a heat, lest it oxidize. - For wholly fiee from alcid. Rinse the copper once Mohllr's description of the process see Annal/en or twice with strono alcohol, to remove the Chiem. unrl Phar.c., 96. 215. It differs in no water, dry at 1000~, cool and weigh. - In- essential partic'ular fiolm that given above, exstea(d of a platinum capsule the precipitation cepting that no platinum ca)psule is employed. may be effected almost as well in a porcelain B. Instead of weighing the metallic copper, crucible, or dish, or in a beaker. A little this metal niav be (lissolved in the solutiOll of a more time will then be required, however, ferric salt, andl the amlount of ferrous salt thus owing to the absence of' galvanic action be- folrmedi may be estimated by titration. See tween the platinumi and zinc,-unless indeed below, Principle III. If' the solution contails a weighed strip of clearn platinumll foil be nitric acid or metals reducible by zinc, such as placed in contact with the zinc, —and the bismllutlh or lead, the copper nmlaS be precipiwhole of the copper will be deposited in the tated friom an ainmoniacal solution. To this tbrm of loose nmasses, not adherent to the dish. end mdix the acid solution with an excess of Great care must be exercised in washing anlmnonia water, filter if' need be, add a quanthis spongy precipitate that no minute parti- tity of zinc filings or powder to thle clear solucles of the copper are carried away by the tion, an(l heat the latter moderately until its water and lost. The dry, spongy precipitate blue color has disappeared and all the copper had better be igrnited in a current of' hydro- is precipitated. Wash the copper thoroughly gen before weighing it. I have observed that with hot water in the first place, then digest it an apprecia.ble loss of weight usually occurs, with dilute sulphuric acid to remove the excess varying in my experiments firom 0.5 to 2 per of' zinc, and finally wash with water and add cent of' the dry copper,-whlen the copper the ferric salt. precipitated by Zinc fi'om sulphuric acid solu- C. An important mnodification of the protions is ignited in hy(lr gen. (Storer, Ml1e- cess has recently been introduced by Steinmoibs Amnerican Acad., 1860, 8. 47.) In a beck, who uses tile impure zinlc of' commnerce single experiment, reported by Fresenius, no to precipitate the copper, and subsequently such loss was observed. When carefllly con- estimates the latter by titration with cyanide ducted the process yields very accurate results. of potassium, (See Copper Salts.) In this It is an excellent process, providled only that case the small amount of lead which ordinary pure zinc can be ptocured. But it is essential zinc contains does no harni. - As applied that the zinc employed shall dissolve in cllor- to the poor ores of Mansfeld, the details of hlydric acid without leaving any residue. Such Steinbeck's process are as follows:-Weigh zinc can rarely be fotund in colnmerce, andl it out.5 grins. of the powdered ore, roast it;, if it cannot readily be prepare(l anywhere, except- contain much sulphur or bitumen, put it in a ing froom ores of' exceptional purity. The flask aind pour upon it 40 or.50 c. c. of crtude colmmon statement of' the books that zinc can chlorhydric acid of 1.16 sp. gr. then add be frieed fromn lead by redistillation is an error. either 1 c. c. or 6 c. c, according to the char(Fresenius; Colnpare Wollaston's mnethod of acter of the ore, of diluted nitric acid, preprecipitating Cadmiurm, p. 56.) It is necessa- pared by mnixin-' eqlual volumes of water and rv to avoid using a piece of' zinc much larger nitric acid( of 1.2 sp. gr. Let thIe mixture than is needed, as in that case after all the ligest at a gentle heat on a sand bath tor copper is precipitate(1, a galvanic current half an houll and finall!y heat the liquid to may be forlned between the copper and the re- strong boiling fbr 10 or 15 minutes. In this maining zinc, which may cause a small por- way not only the copper, but the iron, lead, tion of the dissolved zinc to be deposited upon zinc, nickel, cobalt and nlanganese which acthe copper in the metallic state and to mix it- company it are dissolved as chlorides. No self so intimately wvith the copper that its sub- cl-ore than 0.01 to 0.03 per cent of copper is se(quent separation by chlbrhydrie acid is left in the insoluble residue. By operating in lifficult. (H. Rose.) this methodical way no trace of nitric aci(1 or The method now in question is a very old of any oxide of nitrogen will be left in the one. It was used, for example, by Vauquelin solution. - Filter the solution into a as longr argo as 1798 (Annales de Chimie, 28. beaker of aboutt400 c. c. capacity, in which a 50). Pfaff in 1825 (Pfqff's Handbuch anaatlt. strip of platinum foil and a bit of zinc rod Chem., 2. 294) speaks of it inl the following have previously been placed. The zinc mayv terms: Zinc is to be preferred to iron as contain as much as 0.1 to 0.3 per cent of lead the precipitant, since the precipitated copper without dletriment to the process. Copper bemay be removed fronm zinc more readily than it gins to be precipitated (luring the filtration can be fi'om iron; almost the whole of the cop- and( the precipitat:on is speedily finished, per will fall off' in fine scales on the slighltest thanks to the galvanic action between the agitation. InI order to be sure that all the zinic and p)latinunl and to the entire absence copper is precipitated test the liquid with sul- of nitric acid from the concentrated hot solu COPPER. 203 tion. At the end of from one-half to three- prese-ice of an impurity consisting of organic quarters of an hour after the beginningf of the matter, dlerive(l from the iron, which adheres to filtration no trace of copper can be detected tihe spongy copper,-probably some one of' tle in the solution. The precipitated copper is in hydro-carbons which are generated by the part attached to the platinum foil, while anoth- action of acids upon iron. Mere oxidation of er part floats about in spongy nmasses. After the copper could readily be avoided by washthe excess of' zinc has been remloved the cop- ing away the water from it with strong alcoper) is washed by decantation repeatedly with hol before d rying it, and indeed when no clear well water, and is then (lissolved ill nitric alcohol is used the bright surfaces of compact acid and titrated withl cyanide of potassium specimens of copper precipitated by iron will (see Copper Salts, Steinbeck's process). In remain untarnished when rapidly driiedl in the washing the precipitat.ed copperl care should air, at temperatures even as high as 110~ or be taken to decant thle wash water into a large 115~. It is easy to convince one's self' of the (dish, and to collect any. particles of copper presence of iml)urity in the precipitated copwhich may be tleposited there. (Steinbeck, per by hbeating a little of' it in a smlall bulb Zeitsch. canalyt. Chem., 1869, 8. 9.) tube with narrow outlet, such as is used for Ahiethod 2. Precipitafion of the copper by detecting arsenic. A quantity of water will Iron2. (The so-called Swedlissh Assay/.) Acid- be seen to collect as a sublimate in the narulate the copper solution with sulphuric acid, row, cold part of the tube, while the copper in and in case arny nitriic acid be present expel it the bulb becomes bright and lustrous. A d(iscompletely by evaporating the solution. Then tinct elnpyreulnatic odor is at the sanie time dilute with water, heat the solution to boiling, perceptible. Carbonic acid is given off, as anid as soon as it boils place in it a plate of' may be proved by testing with limle water, and it-on which has been made clean and bright by aminonia also is sometimes evolved. The filing, or, better, a rather broad strip of sheet amount of impurity thus retained by porous ilron which has been cleaned by imnersion in spongy copper mllay amount to 2 or 2.5 per cent dilute sulphuric acid. Continue to heat the of' the weight of the precipitate. In a series solution until all the copper has been precipi- of.50 or 60 experiments, in which the copper tated, as is (leterlminedl by testing with sul- was precipitated firom sulphuric acid solutions, p)huretted hydrogen, then remove the copper I found the loss of weight on ignition in hydrofi'oni the iron, wash it with boiling water an(t gen to vary from 1.5 to 4, or even 5 per cent. dry it. In order to retnove'any carbon which WhVen precipitated from chlorhydric aci(l soluma)y have been derived fiom the iron heat the tions the copper is usually crystalline and copper in a glass tube, first in a current of air compact, and doubtless contains less impurity. an(l then in a current of hydrogen, in order to It has often been proposed to calcine the redluce the oxide of copper which has been metallic copper to oxide before weighing it, or formned. Allow the copper to cool in the cur- to convert it to oxide by treating it with nitric rent of' hyrdrogen an(l weigh it, after air has acid and subsequently igniting, but the operabeeni aldmnitted to the cold tube. In case the tion is far less convenient and certain than the copper is collected on a filter, and the latter reduction by hydrogen. According to Reisechis burned by itself afteil the copper has been auer (Zeitsch. analyt. Chenm., 1864, 3. 139) it-iliove(l fronm it as completely as possible, it is as good as imllpossible to convert small there will be fbomed fiom the filter ash a little quantities of finely dividled metallic copper silicate of copper which cannot be completely comlpletely into cupric oxide by long continued reduced by hydrogen. It inmay be reckoned as ignition in a current of oxygen r as. oxitle of copper after subtracting the weight Selected pieces of the best Russian sheet of the filter ash. Iron is less convenient than iron, about 3.5 inches long by 2.5 inches broad, zinc as a precipitant of' copper, as hlas been are well suited for the precipitation of copper. already set forth in SMethod 1. (Berzelius, and Only such pieces as have a perfectly smooth )Dumelil. Schwv., (N. IR.) 3. 445, as cited by and even surface should be used, fo' those Pfiff' in his Hanldbuch analqyt. Chem., 1825, 2. which are corruflgated or uneven will be acted 295.) But little can be a'dted to-day to Pfaff's upon unequally by the acid copper solution, concise account of the Swedish assay. though and some copper mlight ble lost in the cavities itis often better to use chlorhydric than sulphu- thus formled upon the sheet. The corners of ric acid. The use of' hot air, as a, prelimninary the bits of sheet iron had better be rounded to the ignition in hydrocen, is no lonlger re- off with a file, lest by their corrosion particles garded as necessary, it being custolrmary to of metallic iron dirop cff and contaminate tile lheattlthe copper directly in hydrogen as soon copper. Before being used the sheet iron as it is sufficiently dry. must be soaked in dilute sulphuric acid until Thie iSgnitiojn in hvrogen is essential, since the glazed coating of' silicate of iron upon it is the copperl p)recipitated by iron is rarely so loosened to such an extent that it can be pIuire thllatit will not lose something on being washed off. One of' these bits of iron is tlhurs ijilteil. Thisignition is necessitated less nad(le to lean alailst tile side of the beaker in by tile oxi&dl of' copper' forlned (luring the which the precipitation is efftected, so that tile process of' drying the precipitate, than by the largest possible surfa:ce of the iron shall be exC1 '2d04 COPPeeR. posed, andi that the sheet may be equally cor- leave little to he desired when all the requirerodedl upon both side.s by tile acid liquid. ments are fhlfilled, but tile operator must lhave At the close of the precipitation most of had long experience in order that he imay ithe copper will be found detached fi'om the know the assay thoroughly, and must continiron in one or more loose spongy masses. Any ually exercise,th greatest possible care.'I'lle small particles of copper which remain adhe- chief difhciulty lies in the oper'at.ion of prierilng to the iron may lbe rubbed off with the cipitalting thle copper. The cprecilpitation nmust finger. taking care not to disturb the black occur at a certain tenmperature, the solution coating of' impurities from the iron, whiclh must neither be too hot nor too cold, lest tihe forms upon the surface of the latter beneath copper fasten itself too fireidly to the iron. It the copper. Care must be taken, moreover, is necessary also to have tihe right quantity of to avoidl the precipitation of an insoluble acid, so that there,ax, not be a great excess subsalt of iron when the copper comes to be of it to occasion too violent action iand to dliswvashed. solve too hauch of the iron. while there is still If after the removal of the iron the clear enough to prevent tihe firiit;tion of baiic ironr acid solution were largely diluted with hot salts which would containinite the coliler. water, an abundant precipitate of' a basic salt The solution should. Inereover: have neither of iron would iraimmediatelly be formed, es- too large nor too small a volume. It is spepecially it' the precipitation has ben effelcted cially imnportant that tlhe operator be pirecsent at in a sulphuric acid solution, and the same the moment when all tlhe copper hlas ls en thing would happen if hot water were pouredl precipitated, in order that t ie iron inmay be upon thecopper firoom which the clear acid so- inimediately removed and the acid liquors delution htdjmst been decanted. To avoid this canted firom the colppler. 11 these olperations roubhle, wash the copper once or t wice with and precautions require.u:ch lpracti e, expeccold water before any hot water is poured upon rience, patience and ctare, in order that useful it, or, in case of' need, rinse the precipitate results may be obtained. It is true that fr'om once or twie with very dilute chlorhydric 4 to (6 assays may be carried{l on sinultaneotsly, acid befbre washing it with water. -- In but the operator must wvatch them carefi!lyv, conducting the assay it is of importance that especially towards the close. ThIe process the solution should be dilute, since, in that is distinctly inferior to tlIht of Steinbeck (see event, the precipitation of' the copper goes on under Method 1) or to thwat of' Ltclmox, by more regul;arly and is sooner completed; it galvanic precipitation (see Copper Salts). should be warm, not only that the copper may According to Johnson (in his Newv York edibe precipitatedl more ralpidly, but in order to tion of'Fresenius) the precipitation ty iron sucavoid the formation of a basic iron salt which ceeds well when iron cat beI obtainedl, which is very apt to contaminate the copper wllen it dissolves in dlilute acid witlhout the sepiration is precipitated,from a cold solution. This in- of weighable quantities of black particles or soluble basic iron salt is liable to fbrm during flakes. If the copper solutoion be cold, dilute the precipitation even in warm solutions, if and nearly neutral when the iroin is fR.,t placedc they are not sufficiently acidulated. If a so- in it, the copper has little adhesion to the iroii, iution is at tihe sanme time rather concentrated and malay be readily detaciedl finom it for the and but foebly acid, a portion of the copper purpose of weighing. If, as soon as thle iroii is may adhere to the iron so firmly that it can- coated with copper, sonie 20 c. c. of chlorhvnot be rubbed off. dric' acid are added to tile solution, and the iiq1The chief difficulty in the assay is to dis- uid is heated nearly to boiling, and imaintained tinguishi between muinute particles of' metallic at that temperature withtott actual ebullition, copper, which are liable to float away in the the rest of the copper is deposited as a wash water and be lost., and equally minute spongy, coherent mias, xhlirh, with due care, particles of impurities firom the iron which may be removed fimout the iron and washed are ait to remain with and conitamiinate the without falling to pieces. In case the coppler precipitated copper. After some practice, cannot readily be washced by decantation, it however, tile operator can overcome this diffi- may be gathered oil a sm;mall filter amid thie latculty and can obtain. constantly, tolerably sat- ter subsequently burned. isfactory results. As has already been said, It is a matter of great iimportance that the it is usually easier to obtain good results with last traces of' nitric anti nitrous acids be rechlorhydric acid solutions than in those acidu- moved from the copper solution before the inlated with sulphuric acid (Storer, Mlemoirs troduction of' the iron, for if either o' these American Acad., 1859, 8. pp. 43-48). acids be present, even in mninute proportioni, it The fbllovwing judgincent of the process has is well nigh impossible to precipitate the last recently been published by the Directors of portions of the copper. The nitric acid inay be the Mining and Smnelting works at Mansfeld, removed by evaporati.ig the solution as nearly (Zeitsch. analyt. Chein., 1869, 8. 2). The to dryness as can be done uponi a water bath, Swvedish assay is inconvenient on account of with two successive portions of pure sulphurie the multiplicity of operations and the dificul- acid, or until no vestige of blue crystals cnan be ty of conducting it. It is true that the results seen in the residue; or, better, the nitric acid COrPER.'2_05 solution may be twice evaporated to dryness of the ferrous sulphate the last traces of nitric with all excess of ordinary strong mnuriatic acid. acid may be got rid of' flr more quickly, easily In order to bring a ce(pper ore or alloy into and certainly, than by the ~ld method of evapsolution with the use of the least possible quan- orating with several successive portions of titv of nitric acid, Mobr (7'itrirmeithode, 1855, chlorhydric acid.. 363) heats the substance with chlorhydiric According to Gibbs (An.ercacn Journ. Sci.., acid, and adds nitric acid drop by drop, so long 1867, 44, 21 2), the fin ly pulverized ore may as any thing, dissolves, taking care to wait after be mixed in a porcelain erueible with 3 or 4 ach addtition untilno more nitric oxide gas is times its weight of a inixture of ole molecule (of given offL The chlorhydric acid solution is bisuiphate of potassium and one of nitrate of finally heated to )oiling to destroy the last por- potassium. Heat the mixturte srowly to low tious of nitric acidl. Or, better, in case iron is redness, —bst in a inuffle. The sulphides are not to be determined in the solution, some oxidized completely without the least frothing ferrous sulphate may be added anti the mixture of the hot mixture. Add enough strong sulboiled umtil all the nitric acid is destroyed. phuric acid to convert all the sulphate of' poF. P. Pearson (Americnn Journ. Sci,. 1869, tassiumn into bisulphate, and again carefully 4. 1 9)4) proceeds as foillows: — Place a weighed heat the crucible until its contents fuse to a 1quantity of the powdlered ore in a porcelain clear mass. The crucible is not attacked by dish, together with some Chlorate of Potassium, the flux, and the old mass may usually be 5 grins. of an 1 per cent ore will be enough for readily separated from thle crucible. On disan assay, and a small teaspoonful of the chlo- solving the mass in water the wvole of the iron rate may be added to it. Invert a glass fimnel, andt copper are found in the state of sulphates, hiaving a bent stem, in the dish, and pour into and the insoluble silica may be separated by the dish rather more ordinary strong nitric acid filtration. The whole operation requires about than wouldi be sufficient to cover the powd.r. am hour. In the case of ores containing much Place the dish on a water bath, and aifter some hisulphide of iron it is best to heat the powtime throw in siinall quantities of chlorate of po- dered ore as long as sulphur is given of before taassiumn at frequent imtervals, until free sulphur treating it with the oxidizing mixture. can no longer he seen in the dish. As a general Another method, proposed by Mhr' (Zeitsch. rule, it is safer andl more convenient to heat the alaytq. Choen., 1862, 1. 143) is as follows.mixture onl a water bath than upon sand,:though Place 5 grins. of the powdered ore in a porcethe oxihlation of tile sulphur is inmore rapid when lain dish of' 10 c. m. diameter, together with the mixture of niitric acid and chlorate is heated some suipburi' aeit water, and nitric acid. to actual boiling. When the last I)articles of Cover the dish with a large watch glass ant( sullphur have been destroyed remove the fun- heat the mixture gently. Much spirting will iiel firom the dish, rinse it with water, and col- occur, while a quantity of fiee sulphur sepalect the washings in a beaker by thelmselves. rates aind envelopes some of the ore. Dry the Allow the liquid in the dish to become cold, liquid by applying a stronger heat, remove th-e pour 1u)pon it a quantity of ordinary strong watch glass an(l increase the heat until the ~hlorh(Mlric aci l, rath rger than the quanti- sulphur barns and the free acid is volatilized. ty of nitric aci(l tIken at first, evaporate the Allow the dish to cool and add some more nimixer l solution to dryness and heat the dry trie acid and a little s lphuric acid; if red resi(lue, to render silica insoluble. Treat the fluncs appear it is a sign that sonme of the iesi(lcue wiith water and without filterin,, wash ore is still unlecomlposed. In that event tlhe cntents of the dish into the beake.r which evaporate to, dryness and burn o' the sulphur. conitains tilhe rin1sim.ls of the funnel. Heat the for the second time. In the ease of rich ores liquidt nearly to boiling, acld to it some 25 c. c. this operation may have to be repeated a of a strono solution of ferrous sulphate, andl boil third time. The process has the merit of rethe mixture br 4o or 5 minutes, in order to de- moving almost completely any lead, antimony stroy the smill quantity of nitric acid which or tin which i might be contained in the ore.. has previously escapedl decomposition. The For ther' inethlxts of ldecomlposing sulphuferrous salt seldom or never acts instantaneous- retted ores see above, under! Methodl 1, Steinly, but thle redtucing action proceeds rapidly beck's modification; and below, nnder Copperwhliec once begun. If need be, add more of Salts, Parkes's copper assay. the ferrous solution, little by little, until the Method 3. Precipitation of the copper by, entire contents of the beaker become dark col- Ctdaium. Instead of zinc, cadminnum may be oredl or almost black, and no more gas is disen- used with advantage for precipitating copper.. gaged. To be sure that all the nitric acid has Its merits are that it can be obtained pure, and bheemi reduced pl)ace a drop of the boiled liquid that it dissolves with less violetce than zinc in, upon tporcelain, and test it with ferricyanide of acid solutions. It should be employed in the J)otassiumI. Filter the boiled liquid into a wide fbrm of' a rod rather than in that of' fbil beake.r and precipitate the copper on a sheet of since portions of the latter are apt to break iron, at above. It is easy to oxidize the whole off in small pieces, especially in a strongly of the sull1hur in the ore by means of the mix- acid solution, which are dlifficult to remove. ture of niiitric acid and chlorate; and by means (Classen, Journ. prukt. Chem., 96. 259.) 206 COPP,,t. M/[ethod 4. Precipjitftion of the copper hq1 the twisted into the form of a flat coil, thle outergalvanic currenrt. The lrocess of Luckow, most convolution of which is so larae that it (Zeitsch. anlylt. Chem., 1869, 8. 26. Chemi- touclhes the sildes of tre beaker.'hIe rest of cal.News, 1869, 19. 221), for lwh-ich a premium the Nwire is left straight, and is madle to Iprowas recently awarded bS the Directors of the ject u-wards, as iit were tle cotitilluati0 of Mansfb:ld copper mines, is as follows:-Wreigh an axis at tlle centre of the coil. ly m1eans (of out several portions, each of 2 or 3 grmins., of binding screws the uIpper end of the platinnnm the finely-powdere(, well samlpled ore. Place wire is connected with the coiper piolet of a galeach of' the powders on a piece of:heet iron vanic battery. The coil is immtlersed in tle and roast them over the flame, of a. Bunsen beaker so far that it shall Iest tupon the undislarmp, taking care to stir them occasionally solved residue of the evaporation; its convolnwith a stiff platinum wire. With the oires of tions serve to keep the wire in place at the midthe Mansfeld district the whole of the bitumi- dle of the beaker. If' the operation has been nous matter nmay be thus burned off in about carefully conducte(d, tlle liquid above the resi7 minutes. When the pieces of sheet iron due in the beaker will i)e nearly clear. It' it have become col(l, brush off' the powders with be very cloudy, as is likely to be the case when a cainel's-hair brush, upon sheets of glazed the liquid has spirted duling the evaporation, paper, such as book-binder's use, and transfer add to it 1 or 2 c, c. of a concentrated solution them to small beakers having perfectly -flat of nitrate ofbarium. and mix this reatgent with bottoms both within and without. The beak- the rest of the liquid by carefully novinf the ers should be 2 inches high, and about 1.5 inch platinum coil tip and down in the beaker; then in diameter. - Pour upon each of' the leave thle liquid at rest tor a fw nminutes before powders 2 or 3 c. c. of nitric acid of 1.2 sp. gr., subjecting it to the action of the galvanic cur'to(gether with 10 or 15 drops of pure concen- rent. It is not necessary, however, to wait untratedl sulpllhuric: aci(l. Place the beakers upon til the liquid is perfectly clearbefbre beginning a san(l bath, cover them with perforated watch to precipitate the colppel, nor is it essential glasses, or with fuinnels from which the stems that all the copp)er in the residue of thle evapohave been cut, and heat them lmoderately at ration shall Ie brotght into solution at lhe first. When the contents of the beakers have start. The last of' it will gradually dissolve in become almiost dry increase the heat so as to the dilute acidl dui1ing the process of' precipitaevaporate and expel the whole of the free sul- tion. A cylinder-shaped piece of' platinum phuric acid. This operation will require from foil is next placed in the beaker above the coil tllree-quarters of' an hour to ati hoiur. The of' wilie. - To mlake this cylinder take a purpose of' thle sulphuric acid is to increase the flat piece of foil about 2.5 ilinces long by 1.25 oxidizing power of' the nitric acid aRndl to coln- inch broad, and lap one end of' it over a bine with any calcium which may be present. piece 6f platinlum wire so that it shall be atIt is well to add somle 10 or 20 drops of chlol- tached firmly to the wire, then bentd the fbil hydric acid to the original mixture of' nitric into the shape of' a cylinder, or, rather, of a and sulphuric aci(ds, since the rapidity of' the half cylindler, for there niust be some openl evapo'ration is thereby promoted, and the mix- space left in orider that the fbil unaty be Ilalced ture of' aci( and ore is less liable to bumpl and ill the beaker so as to enclose the axis of the spir't than it is when no chlorlhydric acid has coil. This cylinder is illllmersedl in the liquidl been a(dded. Or instead of' proceeding as to such a depth that its lower cdge shall ibe above, measure out for each assay,f fom bu- about one-tenth of an ilnchl (not more tllarln onerettes kept charlged for the putrpose, 4 c. c. of' seventh of' an inch) above the flat coil, whllile a imixture of' equal bulks of strong sulphuric the wiire whlich projects pwairds 1'o0111 tile axis aci(l and water, 6 c. c. of nitric acid, and about of tle coil is iat the (celltre of the cy!linder. If' 25 (lrops of chlorhydric acid. the Ieaker is ialt'f iull of acid about three-qcuarllWhen all the sulplhuic acid has been ex- tel's of thle leight oft' the cylinder will be imipelled(, the beaker is renioved fiom the sand mnersed. --'he wire attached to the c3ylinbath and allowed to cool. The crust of' solid d(lei is fistened to the zillC pole of the battery matter at the bottom of' the beaket is barely by leans ofi binding screws, propelly fitted to moistene(d with a mnixture of' 1 part of' itric the armls of' an iron stailll. acid ot' 1.2 sp. gr., and 6 parts of' water, and I1n a very shlort timle afiterl the admllission of then carefilly pierced in several places with the current the cylinderl of'platinuln foil lwhichl the sharpened point of' a glass red. The trod, fbrmns the negative pole of' the battery is covas well as the covert and sides of the beaker, ered with a layer of' lmetallic copper, which are then washedl with the nitric acid, diluted gra lually spreadls firomn below upward(ls, whllile as above, and the beaker is about half filled bubbles of gas escape fi'om the surface of, the with this liqutid. A ftw drops of' a concentra- coil of' platinium wire and materially facilitate ted solution of tartaric acid are fimnally added the action of' the dilute acid upon the copper to the solution, and a coil of platinunl wire is in thle residue of' the evaporation. Tbhe simmcarefiully imnlnelsed inl it. This wire may be plest way of' determining when all the copper about one-twentieth of an inech thick and 7.5 has been precipitatedl is to add some dilute iiiinches long; for two-thirds of' its length it is tric acid to the liquid in the beaker, and to COPPER. 207 observe whether any copper is dleposited upon lowing details are adapted for a 60 per cent the fresh surface of platinum which has been sulphuretted coppetr ore, wh:ch contains also thus brought into the fiel of action. If no film 0.3 to 0.4 per cent of silver. Digest 2 grms. of copper becomes visible in the course of' or of' thle powdlered( ore with nitric acid, until the 10 minutes, the process is finished. Or, a bit sulpIhur separates in small globules. Pour ot thin platinum wire may be immersed in the into the solution, fromn a Ihurette. dilute standliquid( in contact with the cylintler, and ard chlorhydric acid, until all the silver is watched to see if it remains bright. ()r, test a precipitatedl, anal note low much of the acid drlop of the liquid with sulphurettedl hydrogen. is required. This stanllard acidl is of such When all the copper has been (leposited, strenoth that 1 c. c. of' it is equivalent to 1 lift the platinum cylinder out of the liquid, mnilligrim. of silver (see Cliloride of Silver). without disconnecting it froml the battery, and Neutralize the solution with amlmonia water, imn-erse it several timnes in a beaker of'pure hot then add 15 or 20 drops of nitric acid, and water. Then loosen the binding screw, remove filter. I)ilute the filtrate to the volume of' 200 the platinum cylinder frolm the battery, wash c. c., and procee(l to precipitate the copper by off the water flomn the copper by means of alco- means of the galvanic current, as explained hol thrown from a wash bottle, dry the copper above. The cylinder of platinum foil lmust at 90 —100~ and weigh it. The precipi- present a larger surface than before, in order tation mnay be conveniently effected by means that it may receive the comparatively large of' Kriiger's battery (figured in Zeit.sch. analyt. quantity of copper, andl that the time of' precipChem., 1869, 8. 31). itation may be shortened. Sptecial care must The time required for the precipitation va- be taken that the copper is depositedl in a comnries according to the strength of the galvanic pact state, andt not as a loose sponge. A batcurrent. The whole of the copper will often be tery of 5 small, or 4 somewhat larger, leadprecipitatedl in the course of 3 or 4 hours, zinc cou)les will be needed, —one that can while at other times 5 or 6 hours will hardly generate from 50 to 75 c. c. of mixed oxygen be sufficient. In no case which fhas occurred in and hydrogen in 30 minutes. by the decompothe Mansftld experience has more than 8 hours sition of water, will be sufficient. A current been required when the battery was in order. weaker than this would precipitate the copper It is consequently well enough, in mnost cases, very slowly or incompletely, while with a to let the galvanic current act for 8 hours, fob stronller current the copper is liable to be dethe sake of' certainty. A single assay may posited in too loose a fbrml. The presence of sometiumes be made in 5 or 6 hllors, and never sulphates in the solution is to be avoided as requires more than 10 hours. 18 assays can be far as possible. So, too, as regards chlorhyfinished with 18 small batteries in 12 working dric acid, every trace of an excess of' it hinhours; or, if' the deposition of' copper be allowed ders the compact precipitation of' the copper. to go on by night, 18 assays can be made with IL is of' the first illlpotance that the pre9 balt teries in 24 holurs, or 24 assays with 1 2 cipitated copper be reilloed from contact with batteries, without trouble. the acid liquid before the battery is disconOf the poor Mansfeld ores at least 2 grins. nected, since owing to the large sulface of' the must be taken fobr each assay. It is well, for platinum cylinder the nitric acid would be thatt matter, to take always one a(nd the satme able to act upon the copper to a considerable quantity of'any given ore. Instead of' heating extent even in a very short time. The easiest the ore upon iron it may just as well be roasted way is to watsh out the aci(d liquid fi'Ol the in the porcelain crucible in which it has been beaker, without disturbing the p)latinunl cylinweigled; the operation thus becomles a trifle ler or interrupting the current. To this end1 simpl er and cleaner. By carefill manipulation set a glass tube, attached to a funlnel, in the it is easy to avoid a turbid liquid when the res- beaker,. so that the bottom of' the tube reaches idue of' the evaporation is treated with dilute to the bottom of the beaker, and let rain water nitilic acid. The addition of nitrate of' barium run through the funnel out of' a vessel placed should be carethlly avoided, exceplt in cases of' above it so thalt the acid liquid mlay be pressed nmarked turbidity, for tile sulphate of' barium upwards, anid flow away over the edge of' the I'orlled is liable to attach itself' to the precipi- beaker, or throulh a hole pierced in its side tated copper, and either vitiate the analysis, near the top. Wlheml all the acid has thus been or necessitate a double weighing of the plod(luct. washed away disconnetct the battery, and wash It is important not to disconnect tile battery the cop)ler with water and alcohol in the usual before the precipitated( copper has been re- way. Copper may thus be p)recipitated coinmoved from the acidliquid in the smllall beaker, pletely, as a hard, firm, glistening coating lest soime of it be dissolved by the free nitric upon the, plattinum, even iifro solutions which acid there. T'l'he battery should be disconnected coiitain comllparatively large quantities of' it. at the muoment when the copper is immuiersed in (Zeitsch. clmRiyt. Chesl., 1869, 8. 37.) the beaker of hot water. Several other proposals to estimate copper In order that the priocess Immay succeed with by galvanlie precipitation have been made of rich copper ores, somle slight mlodification of' late years —to say nothingl of' the old experithe foregoing process is required. The fol- ments ot I'ischclr. Thus Gibbs (Avmerican ~~08 COPPER. Journ. Sci., 1865, 39. 64) has shown that cop- which the latter is converted at tlhe positive tPer may be accurately estimated in this way pole of the battery, rapidly acts upon copper in solutions of' tlhe sulphate: —'he deposition iIn presence of a fi'ee acid. To avoid this diflibeing made upIon a platinum capsule wlich culty, Lecoq (Ibid., 1869, p. 35) directs thlat forms the negative elcctrolde of a Bunsen's the apparatus be arranged( in such mlanner that battery of one or two cells in rather feeble ac- the co)pper may be firced fioml thle liquid as tion, and the current being so regulated that the rapidly as possible, without interrlluption of the copper may be preciIitated as a compact, galvanic current. At the close of the precipibright coating. The positive electrode, con- tation he d(raws off' the liquid through a sisted of a stout platinum wire plunged into syphon, taking catre to push down the positive the surface of the copper solution at its centre. electrode, meanwhile, so that it inay ahldniost The time required for the precipitation varied touch the bottom of the l)latinuini c(l ucible from 1 to 3 hours. which forlls the negative electrode, in ordler So, too, Luckow, in 1865, (Dingler's poly- that the current mna lnot be interrupted. Suctech. Jourrl., 177. 296), insisted on the merit of cessive quantities of dilute sulphuric i cid are the process as applied to sulphuric acid solu- then poured upon the metal, withou t intertions of copper ores, salts and alloys. At a rupting the current, until the mothier liquor later date Luckow (see Zeitsch. analyt. Chemr., has been comlpletely removed. The waRshing 1869, 8. 23) extended his process to the analy- is then finished with hot water. By operating sis of nitric acid solutions of copper. He found in this way accurate results iinav be obtained, that even a comparatively f'eeble galvanic cur- unless a very laige excess of flrric salt is rent is competent to precipitate the whole of present. But uince tile loss of copper is prothe copper in excellenlt condition, from solu- portional to the aniouiit of ferric salt, when tions which contain no nmore firee nitric acid tle other conditions of the experiment remain than 0.1 grin. to the c. c. The precipitation unchanged, it is Ipossible to determIiine this lprogoes on regularly and easily, and is far less portion once for all, and to apply a correction influenced by the strength of' the current than forl' it. Lecoq uses 8 of' Bunsen's elelmets, of by the presence of free sulphuric acid in the mecdiuni size and weakly charged, as the source solution. - The process has great merit, in- of the ganlvanic currlenl t, and allows the latter asmuch as it admlits of the previous easy sep- to act lurillng 4 or 5 houis. In presence of aration of tin and antimony, as Oxides, and of nickel, cadnliiium, and zinc (but particularly of' silver as chloride, as has been explained in a nickel), only a weak current should be mainprevious paragrap)l. Even the presence of tained, lest traces of' the foreign metal be prelead does no harlli, since in a solution which cipitated with the cop)per. But the nickel or contains fi'ee nitric acid the action of the gal- other metal thus precipitated can always be vanic current will cause all the lead to be pre- reatlily remloved( by washing with aci(l iin the cipitated in the forml of peroxide, at the posi- manner just described, the action of the tive pole of the battery, while the copper is syphon being merely mllade interimittent. attaching itself to the negative pole. Of' the various mletals likely to occur with copper it A sinmple method of precipitating copper by may be said that thlose of' the alkalies, alka- galvailic action was devised by Ullgren, in line eartlhs and earths, as well as chromiuim, 1866 (see Journ. prak/. C'/ient., 102. 477, iron, cobalt, nlickel and ziiic, will not be thrown and niore fllly in Zeitsch. analyt. Chent., 1868, down by the galvanic current fi'oli acid solu- 7. 442). lIe proceeds as follows:-Bind a pliee tions; that Ilimecury, silver, and bismuth will of' lmoist bladder tightly over onie end of a glass be precipitated like copper, and that lead and tube about 10 c. mu. long and 14 Im. in. wile; manganese will be completely precipitatedl at fill the tube five-sixths imull of' a saturated soluthe positive pole, as peroxides. Silver also, in tion of' chlori(le of' sodiumn, and close its open part, will go dlown is a peroxide. In case a end loosely -with a cork through which a strip mllixture of copper and mercury is operated of zinc, which has been rolled iltto the form'i of upon, the mercury will be precipitated before a cylinder about 0.5 in. Iii. in (.ialneter, is manXlde the copper, in the forlm of' liquid drops, and to pass in such wise that it can be slipped up an aialganlll of copper and mercury will fbrm and down at will. At the upper end. of the as soon as any copper is precipitated. Silver cylinlder the strip of zinc is left flat, and sontme and copper are precipitated well nigh sinmulta- 4 or 5 nl. m. broad; this flat strip, which serves neousiy, but bismluth only after niiost of' the as a conductor, is attached to a striip of platicopper has been deposited. Arsenic and anti- nunm fbil of' siiiiilar width. - Tile copper niony are precil)itated froom a nitric acid solu- solution to be analyzed is placed in a p)iatition, only loug after all the copper has gone nuin capsule of' froml 35 to 40 c. c. capacity. do wnv. This cap)sule is placed on a wet pane of' glass According to Lecoq de Boishaudran (Soc. upon the strip of platinul with which the zinc Chimn. de Iarils, 1867, ). 468), the process of is connlected, the bladder end of the tube is precipitating copper by means of the galvanic sunk a little below the elow the surfce of' the liquid in curreint, is rendered less exact by the presence the capsule, and the tube is clamped finmly in of sulphate of' iron, for the ferric salt into that position. The zinc cylinder is then ill COPPER. 209 -mersed to a depth of 1 c. m. in the solution of the crucible or the boat. Instead of a perfochloride of sodliumi. The purpose of the wet rated cover for the crucible. the bowl of an orglass beneath the capsule is to ensure a con- dinary tobacco piipe may be invertedl in or upon nection between the platinum of the capsule the pcrcelain crucible, and tbe hydrogen passed and the strip. The copper is deposited upon thlrough the stein of the pipe (Allen). the inside of the capsule, and the only care to be Where a small quantity of oxide of copper taken is to avoid a current strong enough to oc- has beenecollected upon a lar1ge filter, it is best casion any considerable development of hydro- to reduce the oxide with hydrogen, as above, gen, fobr in that event the copper would be but after burning the filter. There will always be loosely attached to the platinum. No trouble a considerable loss of material if the oxide be of this sort will be experi,-nced if the zinc is moistened with nitric acid, and then ignited merely touched to the solution of salt in the fbr the purpose of re-oxidizing the copper beginning, and afterwards gradually immersed which has been reduced by the combustion of more deeply, from time to time, as occasion the filter. - In the analysis of certain cyamay require. nides of copper it is not sufficient to heat the'i'he plat':nlum capsule should be clean and compound in hydrogen, since a quantity of carhave been recently ignlted, an(l the solution to bon or nitrogen, amnounting to about 3 per be analyzed should be so dilute that it con- cent of the weight of the residue, remains mixed tains no more than from 0.1 to 0.15 grnm. of or combined with the copper. To remove this copper for a capsule of' the dimensions above imnpurity the copper may be heated alternately given. The copper should be in the form of a in oxygen and hydrogen. until the weigllt of sulphate, and the solution should be acidulated the metal remains constant. (Reischauer, to such an extent that it may contain about Zeit.'ch. analyt. C/hem., 1864, 3. 139.) 1 c. c. of' fiee sulphuric acid for every 30 c. c. Principle III. Power of reducing ferric salts. of solution. In case the proportion of' copper (Compare din Oxide of Copper.) in the substance to be analyzed is totally un- _Application. Estimation of' metallic copper known, it is best to dilute the solution to a de- by titration, instead of' by directly weighing it. termnined volume, to measure out a slnall quan- Met hod. In order that copper may be accutity of' the diluted solution and to add water to rately estirmted in this way, it nmust have been this portion until it has a volume of 30 c. c. precipitated by absolutely pule zinc, in the With an apparatus of the size d(escribed the first place, and afterwards digested with dilute copper will usually all be precipitated in the sulphuric acid, until the last traces of the precourse of 4 or 5 hours. The copper is careful- cipitant have been dissolved. Pour upon the ly washed, first with water, then with alcohol, washed but still illoist spongy copper a quanto remove tl'e water, dried and weighed. If titS of a solution of ferric chloride, fiee from arsenic be present, it will be deposited in black any contamination of ferrous salt, and acidustrips after a part of the copper has been pre- late the mixture with chlorhrdric acid. The cipitated. In case zinc (or cobalt, nickel, iron, copper will tlissolve speedily, while a correor mangiranese,) is to be determined, as well as sponding quantity of the fierric chloride is recopper, a cylinder of cadmium or of aluminum d(uced to the condition of ferrous cliloIcide:may be placed in the chloride of sodium instead cu + 2FeC13 = CuCl, + -2eCl. of' the cylinder of zinc. When cadmium is thus When the copper has all dissolved, dilute used it is not easy to employ sulphuretted hy- the liquid, and determine how much of the fir(tro(gen to test whether all the copper has been rous salt has been forlned, by titrating with precipitated; but by leaving the apparatus in permanganate of potassium. Every 56 parts, action fbr a couple of hours after copper has by weight of' iron found, correspond to 31.7 ceased to be deposited on a fine needle placed parts of' copper. (Fleitmlann, Anlnalen Chenm. in the solution, there will be no risk of lear- tund Pharrn., 98. 141). ing any copper unprecipitated. If it were only possible to obtain pure zinc Princil)le II. Fixity of when heated in hy- readily and cheaply, this process would have a drogen gas. certain value in cases where a large number Applications. Purification of' precipitated of analyses haLve to be made simultaneously. copper. Estimation of copper in mnixtures of It has of course no significance in the case oxide of copper and metallic copper. where only a sillngle determination is to be Mlethod. Place the substaclee in a porcelain nmade. Were it not for the sake of saving crucible, provided with a perforated cover, con- timie it would always be best tb weigh the copduct a stream of dry hydrogen gas into the cru- per (lirectly. cible and heat the latter with a lamp. After ra Properties. Copper fuises only at a white while remove the lamp, and let the contents of heat. Solid copper suffers no change in dry the crucible cool in the atmosphere of hydrogen. air, or in mo,ist air firee fromn carbonic acid, but Or, instead of' the crucible, put the substance gradually t;-;rnishes in moist air which conto be reduced in a porcelain boat, and place tains carbolnic acid. Finely divided copper, the latter in a tube through which hydrogen such as is obtaiaed by precipitation, oxidizes may be conducted. In some few cases a bulb rather (Iluckly in imoist air, especially when tube of hard glass may be better than either *, the air is wal~rm. When ignited in the air a 14 210 corPPER SALTS. layer of black oxide forms upon the surface of and alloys. Assay of copper ores. Separathe metal. Copper (issolves easily in nitric tion of copper fiaom Fe, Mln, Zn, Co, Ni and vaacid, and in hot, strori suilphuric acid. But rious other mectals. in chlorLbYdrici acid and in dilute coldl sulplihu- Mfetho ds. ric acidl it dissolves so slowly that it has often 1. Itedac/ion; o the Copper Salt by Cyanlide been said to be insoluble in these liquids. of Potao;siuo,. IThe process depends upon the According to Mohr (Tzrhi;methode,, 1855, 1. tinct that. vhen a solution of cyanide of potas204), pirecipitated copper dissolves slowly in siumi is slowly added to the ammoniacal soludilate chllorhdric and sulphi1uric acids, with tion of a copper salt the azure blue color of reduction of the latter to suplip uro us acid. The the latter gradually dlisappears, so that the action is sufficiently rapid thai the solution liquid becomes light violet red towards the will give a distinct reaction for copper with close, and at last completely colorless. The sulphuretted hydrog'en, ten minuates after the completion of the reaction is well defined. addition of the acid. For an elaborate set of Accordting to Liebig (Annalen Chlem. und experimeists on' the action of chlorhydric acid Pharii., 95. 118), dicyanide of copper, eyaupon solid mmetallic copper, out of contact with aide of anmoniumni caustic potash and fiee cythe air see Lcewe Zeisch. analyt. Chiem., anoen are folrmed, and the latter, acting upon 1865, 4. 361. LcEwie finds that while solid the free ammonia, gives urea, cyanide of ammetallic copper is uindoubtedly soluble to a cer- noniiium and formlmate of ammonium. tain extent, the action of the chlorhydric acid, A. Parkles's copper test. To prepare t lihe out of contact with the air, is well nigh insig- standard solution of cyanide of potassium pronificant, unless it is concentrated. In propor- ceed as follows: —Dissolve 2000 grains ofphotion as the acid is more dilute, so much the tographer's cyanide of potassium, or about mess does it act upon the copper. Copper dis- 2880 grains of the ordinary cyanide, in 4 pints solves slowly in animonia water if air be fireely of water. On the other hand clean some pure admittedto it but out of' contact with the air electrotype copper, by nmeans of' chlorhydric, ammonia has no solvent action upon it. WL'en or dilute nitric acid, and wash and dry it.' broughbt in contact with an ammoniacal solu- W.Veigh out tlhree pieces of the copper, each of tion of a copper salt, or with a solution of friom 5 to 10 grains. Dissolve them in sepachloride of copper in clhlori ydric acid, out of rate pint flasks, in dilute nitiric acid and boil contact with the air, metallic copper reduces the liquidls to expel nitirous fumes. Dilute the cuprit salts in these solutions to the state each of't the solutions with water to the volume of' cupreous salts, which remain dissolved in the of about haif a pint, supersaturate them with amnmonia, oi in the ehlor!hdric acid, as the ammuoni a water, and allow them to stand until case may be. Copper dissolves with consider- cold. Fill a M!ohr's burette with the solution able facility in solutions of' ftrric salts. espec- of cyanide of' potassium, and allowv the latter a'ily when a fi'ee acid is present. to flow, ltt.lie h little, into one of the flasks For the use ofcoliper cas a eaogent in organic until the blue color of' the copper solution is analysis see under Carbon, p. 64. When almost discharged and is replaced by a faint pure copper is required for other purposes, as lilac tint. Note the unumber of c. e. of the for the indirect assay of eopper, describ ed un- cyanide solution whiichli have been expe ndled, der Copper Salts, or that of iron clescribed un- ammain fill thle buette and titrate the liquids in der Ferriic Salts, it is best to precipitate a the second and in the third flasks in the samne quantity of thIe metal from a solution of the way~ Tak telic iiean of the three results ars sulphate upon a clean iron plate. The precip- the true value of the cyanide soluticn. Or if' itated copper is then boiled with elhlorhydric the results of the first alnd second trials agree acid, to remove the last traces of iron, washed closely it iaiy be iiiinecessarv to proceed with dried, fused, cast into hars and rolled into thin the thim,!.. The'ce uml c sscy is a's fall ows: sheets (Fuchs). Japanese copper, as fbundt in — Pl1acc a known wiicihit of the piowiderdcl ore commerce, is often pure enough for analytical in a iiIsk or beaker providedl with a glass purposes. - The foillowing tests will shlow cover, and anoisten it with strong sulphuric whetliei the copper is pure enough for use:-I' acid. lThen add stron'g nitric acd and adig'est must dissolve completely in niitric acid, andd no the ni xtur t at a eemtle heat until nitmrous trace of a precipitate of' the hydrates of' iron, furnes cease to lbe given of' Addl sniall quanleadl, etc., miust be left, even after long-contin titles of nitice acid, fiom time to time, as occaued standlnog, when the solution is saturated sion mayv require. "lhen tie evoluati on of' iiwith'minmonia water. Neither should any pmoe- trous i comes has wiholly ceased. dilote the solucipitate of' chloridcleof silver appear when clhlor~ tion wvith w-ater, reheat te'olutitmas t'amnsfier it ]lydarie acid is addedl to the solution in dilute WidmlOut fi!teindm to a pint flasIk mnd clitm it nitric acid. After all the copper has been cui it:h watero to the volulmme of' ane-lih:-'lor thIeethirown down with sulphuretted hydrogen, the qucarters of m pint. When the ore is a sulphide, fil lite should leave no residue on evaporation. it nay be, with ordinarv care, completely,xiCopper Salts. dizetl by the sculphuric and nitric acids; but if I',ctpole. Oxidizing power of. assy g'l(cis)Iles,ft'sulphur remain, they sholldll be -1 pffciitions. Estimatio n of copper in salts picked out after the dilution and burned, amid COPPER SALTS. 211 the residue, if any there be, should be dissolved redissolved in acid before the titration can in nitric acid, and added to the main solution. be proceede(d with. - Aecordinio to'Field If any difficulty is experienced in d(issolvinll the (CheomicalNews, 19. 253), manoane e'ntci'lres basic sulphates formed, some chlorhydrii acid in the contrary sense; less than ilhe normdal may be added with advanta. - To the quantity of' cyanide of potassium beine suflidiluted solution of the ore add'an excess of am- cient to efl'ect the decoloration when it is piresmonia rwater, and let the solution stand until it ent. The manganese can be got rid of by addis as. cold as the air of the apartment Then, ino- carbonate of animmonium and a few dhops of without heeding the precipitate d lhyvdrate of Bromine, and heating' the solution. Arsienic iron which mays be present, pour in the stan- does not interfere, except when present with dard solution of the cyanide from a. burette, iron. In that event arseniate of' iron dissolves gradually and cautiously, by small portions, un- in the amimoni a, and, in the presence of copper, til the blue color is nearly discharged, and forms a brownish green solution.'hlis diffithere remains only a faint lilac tiiit. Take culty can be easily remedied byT adding some care, meanwhile, to shake the copper solutionii solution of' sulphate of' mnagnesium; ars:eniate of firequently. Read off the number of'ec. c. of ev- mag nesiunm is formed, and the solution, after anide expendcd, and calculate, fi'om the known the lapse of a few minutes, acquirtes the proper value of that solution, how much copper was color. The assay can then be made, without contained in the sample. - Fromni one-half filtration in the usual way. to three-quarters of' an hour will be required for The standard solution of cyanide of potassithe complete decolorization of the solution, ac- um should be kept in bottles of green olass, cording as more or less copper is present. The' since lead glass is rather easily acted upon by cyanide being added very slowly, especially the solution.' Even thie,reen glass is slowly towards the end of the process, the last tint acted upon a thin scaly deposit beingu formetd. should remain permanent., or nearly so, for Thlie cyanide solution, moreover, slowly deconiabout 10 minutes. To aid in recognizing the poses on keeping. This circumstance is not of tint of the solution, a white glazed tile, or piece any material consequence where nmlanV assays of' white paper, should be placed beneath and arce to be muade, fbr considerable timie is rebehind the flask during the titration. quired to iiaike any decided altieration in the When sesqui-oxitde of'iron. is present, it im- strength of' the solution. For pr:'ctical purparts a greenish appearance to the ammoniacal poses the standard solution will not require to solution, and the proper tint of' the solution is be chectkci oftcnei than once a wt, el, i' it has then best observed by placing the eye on a been piepareid fiomn the best cyaiidle of potaslevel with the top of' the liquid!; after a little sium A solution prepared firom coimmol cvapIractice the alteiation in the tint of' the oxide nide of potassium can only be kept fbr a flew of i-on, wvhich occumrs will afford a sufficient in- dlays without becoming- discolored and mudddy, dication iintil near completion, the reddish but when the solution is rapidly consumed after brownii color becoming liore distinct as the havini( been standardized, it answers very well assay is proceeded with. It will not (10do to re- fo' assay pur'poses. (Parkes, Mining,Joxrnal, move the hydr:itte of iron by filtration befotre 1851; tlnough Percy s:lelalurf/ly.) The addiing any of the cyanide, fbr the iron pre- process Iias been extensively used. particularly v cipitate would thern retain a portion of the cotp- folr assaying ores which eonsst chiefly of oxides, per solutioni witl such tenacity that it could carbonates, silicates and oxyehlorid:es, and for not all be reinoved, either by ammonia or 1by assaying slags;-in general, it has proved to be several hours' washing w ith boiling water, but if well adapted iofbr assaying copper' oires. Like any difficulty is experienced in observing the all other minethods, it requires experience to 1bi tint towardts the completion of the titration, the skilfully conducteld; but tmhat it is capable of iron precipitate may then be removed by fil- yielding correct results, within 0.1 or 0.2 per tration without riisk of losing much copper. ceit, las been tully proved by some thousandus When the assay is finished, the hydrate of iron of' }ssays made by various persons. Soime difis commpletely fiee froim copper, since that ficultics avill alwayss be met with in taking up which was retained at iirst gradually goes into any newv process, but no process slhould be consolution as the decolorization proceeds. The denimedl by, an opera tor, bIecause lih iidis to suciron thus fieed from' copper may be estimiated ceedi in his first trials (Percy, lelallih rgy, 1861, by meains of' biChromiate or 1ermanaganate of p. 479).'otassiunm (see IFrric Salts). The process is imnproperly crtedited to C. Certain metals, such as silver, nickel, co- AMohlr insonie Germnal treatises. (See Fresenrihalt and zinc, interfire with the titi tion moore Vis' Qwcolit. AInal.;.iohr's 7'ilriraoe/hode, 1856, of the cyanide of' potassiuml being then re quited 2 912 iiiid naioeIn C/eiii. aild Phorm., 94. to decolorize the copper solmtion. Silver mmay 1O8.) Flajolot (Anamlies des l'neu;, 1862, 2. be precipitated with chlorhydric acid, and re-, and boinyler's polytech. Jotirn., 168. 217) minoved by filtration fioum the original acid liq- also descri'bcs the process as if hlie (F.) were nor; but when cobalt. niuckel or zinc are pres- its idiscoveirer. ent, tihe copier must first be precipitated, either Renewied attention has recently been called to as Coppei', or as Sulphide of Copper, andti the process by Steinbeck, to whom a premium 212 COPPER SALTS. has been awarded by the directors of the Mans- Clem., 1869, 8. 13; Chemical News, 1869, 19. feld copper mines. 207). Steinbeck's method of procedur e is as follows: The chief merit of Steinbeck's process seems -5 grins. of the ore are treated as described to consist in the methodical and systematic way under Copper, and the precipitated copper is in which the nitric acid and ammonia are enmwashed. The spongy metallic copper, sonme of ployed. It lhad been shown long ago by Liebig which lnav still be adlhering to the platinum (AnLnalen C(hem. und Pharm., 95. 118), that foil, is then dissolved in moderately warm di- the quantity and degree of concentration of the luted nitric acid, prepared by mixinog equal animonia eimp!oyed has a marked influence bulks of water and pure nitric acid of' 1.2 sp. upon the character of the reaction between the gr. For copper ores which contain no more cyanide of potassium and the copper salt. Exthan 6 per cent of copper, 8 c. c. of the diluted l)erillents of Fresenius had also shown that neuacid will be sufficient, but for ores richer than tral salts of ammonium could interfere to a cer6 per cent 16 c. c. of the acid should be taken. tain extent with the reaction. But by operaAfter a little practice the operatori can judge ting always with similar quantities of ammonifiomn the bulk of the spongy metal how much acal compounds, for any one kind of ore, these of the acid to take. The solution of' nitrate of sources of inaccuracy are practically eliminated. copper is allowed to cool, is then mixed with The idea of precipitating the metallic copper 10 c. c. of' a solution of' ammonia, prepared by by means of' commercial zinc is an excellent mixing one volume of anmmonia water of 0.93 one; it follows naturally fiom the observation sp. gr. with 2 volumles of water, and is finally of' Field that the presence of metallic lead does titrated with a standard solution of' cyanide of not interfere with the conduct of Parkes's propotassium, of such strength that 1 c. c. of it cor- cess. respondls to 0.005 grin. ot copper, until the blue Fleck's modtfication. Instead of neutralizing color disappears.. - In the case of ores of the acid solution of copper with ammonia wanlore than 6 per cent copper where 16 c. c. of ter., as directed( by Parkes, Fleck (IPolytech. the diluted nitric acid are used, dilute the solu- (i'entllrblatt, 1859, p. 1313) uses a solution of tion to the voluime of 100 c. c. divide it into sesquic.arbonate of ammonium (1 to 10), and two portions each of 50 c. c., add to each por- lheats the mixture to about 64'; and in order tion 10 c. c. of the anlmmonia water, above do- to lmake the end reaction plainer, lie adds a scribed, and proceed with the titration. The couple of drops of' a solution of foerrocyaiaide of small amount of lead with which the copper, is potassium (1 to 20). Neither the blue color contaminated, derived finom the impure zinc nor the (learlness of the copper solution is alemployed as the precil)itant, does no harm. It tered by this addition. The cyanide solution is precipitated as a hydrate on the addition of is standardlized against a copper solution of the ammonia, and imparts a slight mlilkiness to known strength. On dropping the cyanide sothe liquid. The presence of' smeall quantities lotion into tle blue coplp~r solution warmed to of zinc (less tl;han 5 per cent of the col)per pres- 60, thle odor ot cyancogen is perceptible, and ent) does mot interfrte with the visibility of' the the color ra(ltually disappears. When the ampoint of' decoloration, but any larger iproportion mnonio-coppmer comlpound is destroyed, the soluof' zinc than 5 per cent should be excluded by tion becoells r.d through the fovniation of f'rcarefully washing the precipitated copper. The rocyvanide of' eopper, though no precipitate solutions to. be titrated niust nevel be warm; fitlls, and( with the add.ltion of the final (lrop of tlhey should. always be allowed to acquire the cyanide of p)otassiuni this red, color van)ishes in temperature of the laboratory. its turn, anl the liquitl is left conmpletely colorThe standard solution of' cyanide of potassi- less. - The process is convenient, and apumn is made of' such strength that 1 c. c. shall pears to be an improvement upon tlhat of correspond to 0.005 grin. of' copper. Since 5 Parkes.. According to Fresenius, the presence grms. of' substance are taken for an analysis, of' amni-aoninin salts may exert a. certain dis1 c. c. will consequently represent 0.1 per cent tumbing' inlfiunce, as in Parkes's method. Hence of copper in accordance with th.e proportion. the staundardizing of the cyani(le and the actual 0,005:: 100: x (= 0.1) assay, sllould be performied under circumstances The number of' c. c. of' the cyanide solution as nearly similar as they can be made. expended in destroying the blue color of' the C.. Mlohr's reelhod of' estinating Cyarogen is copper solution multiplied by 0.1 will conse- the converse of' Parkes' copper a ssay, the amquently give the percentage of' copper in the moniacal solution of' a cyanide being titrated sample. In works where niany assays have to with a standard solution of' a copper' salt, until a be iimade daily, new quantities of the cyanide persistent blue color pei'vades thle liquid. The solution must be standardized so often that no cyanide solution is placed in a porcelain dish, trouble is experienced from alteration of the and is stirred continuously during the titration. liquid. It will be enough if the standard be Each drop of the copper solution gives a deep cllecked each week. Starting with the pow- blue color at the point where it touches the amdered ore 6 assays can be made in this way moniacal cyanide, but this color disappears on within. hours, or 20 assays in a working day stirr'ing so long as there is any of' the cyanide of 7 1-2 hlours. (Stienbeck, Zeitsch. analyt. left undeconlposed;i the disappearance of' the COPPER SALTS. 213 color is immediate at first, but becomes more 1 molecule of grape-su(a.r (C6H1206) 180 gra(lual towar(ls the close. (C. Molr, Anna- re-duces 5 molecules of oxide of copper (CuO) len Chem. und Pharm. 94. 198, and 95. 110; = 397. Or 100 parts by weight of anhydrous Mohr's Titrirmethode, 1856, 2. 8). For cer- grape-sugar correspond to 220.5 parts of cutain degrees of concentration and (quantities of pric oxide. Hence if' the quantity of copper ammonia the process gives correct results; but salt reduced be known, the quantity of grapeunder different circumstances, as regards the sugar required to re(luce it may I e readily calamount and strength of the ammonia, a diffter- culated. Milk-su!rar red(uces tle solution of ent quantity of the copper salt will be required the copper salt directly, but in a different profor the same quantity of cyanhydric acid (Lie- portion fiom grape-sugar; -where one equivabig, Annalen C/hem. und Pharim. (95. 118). lent of the latter reduces 10 equivalents of 2. Reduction of the copper salt by Grape- oxide of' copper, 1 equivalent of mnilk-sugar sugar. When the solution of' a copper salt is will reduce only 7 or 8 (quivalents. It is best mixed with a sufficient quantity of tartrate of therefore to convert milk-sugar to grape-sugar potassium or tartrate of sodium, and an excess by boiling the solution for an hour or so with of caustic soda, a deep blue clear solution is a li tle sulphuric acid, before subjecting it to produce!. If this solution be then warimed and analysis. mixed with a sufficietnt quantity of grape-sugar, First method (applicable to clear solutions). the whole of the copper will be thllrown lown To prepare the standard solution of' copper, after a short time in the fborm of' dinoxidle. grind somle fiesh crystals of' pure sulphate of The prinrciple is applied boli to the estimation copper to powder, (dry the powvder by pressing of copper and( of sugar, as. will appear below. it between iolds of filter pipeer until the partiA. Schwarz's copper test. Dissolve the ore cles of' the poxvder no lolger clingr to the paper, or alloy to be tested in nitric acid, or if the weigh out exactly 34.639 grlls. of the powder, substance to lie analyzed is a salt, dissolve it in and dlissolve it in about 200 c. c. of' water. water. Mix tile cold solution with a solution Dissolve in another vessel 173 grinls. of' pure,of normal tartrlate of potassium ill a capacious crystallized Rochelle salt in 480 c. c. of a pure porcelain (islh, and ald an excess of' caustic solution of caustic soda of' 1.14 sp. gr. Add soda or caustic potash. Alix the dllrk blue the first solution gradually to the second, takliquid with a sufficient quantity ot' a solution ot' ing care to wash out the last i)ortions of it, grape-sL(gar or Inilk-sugar, and hleat thle mix- and -dilute the blue mixtulre to the volume of 1 ture on a water bath until the li(luid sho,\s a litre. 10 c. c. of this solution contain 0.34639 tbrown color on the border, whic4h is a sign. that grinl. of' sulphate of' coppeir, and correspond to the whole of' thle copper is precipitated, aunl 0.05 grin. of anhllydrous grape-sugar. The that the alka;li begins to act upont the sugar solution should be kept in a cool, (lark place in with fobination of brown-colored p)ro(lucts. tightly stopperend bottles filled to the top; for When the precipitate has subsided, filter. Thle by the action of' light, or the absorption of filtrate is, in most cases, of' a deep brown color, carbonic acid froml the air, the solution and shows a muddy yellowish layer ast the might be changed to such an extent that it point of contact with the waslh wNater. But would deposit dinoxide of copper on being this turbidity disalp._ars on stirring the liquid, heated. and is not dlue to the presence of cop')er. When properly prepared and in good condiWash the dinoxide of copper with hot water, tion, the copper solution will remain unaltered, until the washings are perlectly colorless; but even when strongly boiled; it is only on the leave in the dish any particles oft' tle prccipi- addition of grape-sugar that any dinoxide of tate which may filrlmly adltcre to it. Finally copper is precipitated. Before using the soluestimnate the copper by means ofa afeiric salt, as tion it should be tested as follows: -Mix 10 explained undter dinOxi(le of' Ci)ppe.. c. c of the solution with 40 c. c. of water, or B. Fehleng's method of estima;ing -Squgar. Two with a dilute solution of caustic soda, if there general metlods for estimating sugar depend is reason to believe that the liquid has absorbed upon the principle now in question. Either carbonic acid, and boil the mixture f'or some there may be adldedl to a solution of copper of minutes; in case even the smallest quantity of known strength the exact quantity of' grape- dinoxide of copper separates out in this expersugar required to reduce the whole oft the c,~p- iment, the solution is unfit for use. - The per salt to the state of' dinoxide; or the copper solution of sugar to be tested must be highly solution may be added in excess, andl the dilute; it should contain no more than 0.5 per amount ot'dinoxide which separates determined. cent of' sugar. In case the first experiment The tormer method is usually employed when showrs that the sugar solutjon is too strong, practicable; the latter being resorted to when- dilute it with a definite quantity of water, and ever the liquid to be tested is so dark-colored repeat the trial. that it woult be difficult to dletermine the point For the actual analysis measure 10 c. c. of at which the reduction of' the copper salt and the copper solution, fiom a pipette or burette, precipitation of the dinoxi(le is accomplished. into a small flask or porcelain dish, add 40 c.c. The quantity of' copper salt re(luced is pro- of' water, or of a very dilute solution of soda, portional to that of the girape-sugar added: - in case water should make the- solution turbid, 214~l~~t ~COPPER SALTS. heat the mixture until it boils gently, and let reduce the whole of the copper salt, and heat the sugar solution flow in slowly, and by small the mixture fbor about ten minutes on a water portions. firom a burette, dlivided to tenths of bath. W~hen the reduction is complete, wash cc. The i:Lqui, vill exhibi'o a greenish-brown the dinOxidle of Copper by decantation with tint, after th a(ddition of the first few l'rops of hoilini water, pass the decanted liquors the su'-,r so 1.ii-sn. due to the suspension of thrbouh a weioshed filter, then transfer the p u,.rievles of' te ir ed ~linoxide acld ytllow iy- pricipitate to tbe filter, dlry at 100 and w1eigwor. dra. ted dinoxike in the blue liquor. In proper- O(r leterlllle the co)pper by one of the volulion as more su(rar is ad(ed, thile prccipitate metric nmethods dependin i uipon the redluction becomes larger, acquires a reddler tint, andl of teinrit chloride, as explained undler tdinOxide ubsides more speedily. When the precipitate of' Copper. It is important to wash the p'esents a deep red color, remnove the lamp, dinoxide in the manner above described, for allow the mixture to settle a little, andl place if the liquid were allowed to cool in contact the fl sk on whijte p:per;' or, in case a poree- with the precipitate, the latter would gradually lain tish hs beien eillploy edl, set it in an in- redissolve in piroportion as it absorbed oxygen clined position, so th:t tile finiteist trnt of fironm the atmllosphere and clihanged to cuprio bluish green may be detected To inlake qullite oxide (Fel!iniu, iil, cealen Cheim. 1d( Pihalma., sure that the precipitation is comlplete, pouni a 72. 106, -umd 106. 75; Neubauer, Arctrio. s1all portion of thle clealr superin:tta lit liquid P]htrio., (2) 72. 278). ilto a test tube, add a drop of the sugar solu - TIhe tobregvoino methods maiy be applied imtion, and heat tile tube. A yellowish reid pre- mediately to( the estimation of sucar in the cipitate will form if the least tirace of the juece of,rapes, apples, and other fi'uits, after colpper salt has been left undlecolposed. in tile liquid has been properly diluted. So also case any precipitate does foimin, pouri the con- to brewer's wort, the filtrate fi'om distiller's tents of the test tube back into the dish or inash and to diaibetic urine. The other subflask, and continue to t dli tile solution of sui'ar stances besidles sugar contained in tlhese liquids until tile reaction is comlplete, The voluinme of generally exert nto perceptible reducing action the solutioi of sugar which has been-expenl(led upon the copper salt. Ili case there is reason contains 0.05 grin. of' anhvdrous'rrape-suga ri to appirehind the presence of any reducing When the iprecipitation is finished it is ivell agent, beside sugar, mix the liquid in a mleasurto try whether thle operation h:as beell a thorl- in flask with a solution of acetate of lead, unoughly successful onc thiat is to say, whether til the fibreign matters are precipitated, then the solutioni is rieally fiee fioin copper, sugar, dilute with wivater to the mark, let the mixture and brown products of the decomposilion of settle, filter throutgh a dry filter, and estimate sugar. To this en I filter o(l a portion of the the sugar in the filtrate (Fehling). In case liquid while it is still hot, and heat somne of the the amount of grape-sugar in fermented liquids -filtrate with a drop of' tile copper solution, and is to be determinlied with the greatest possible some of it with a little of the sunar solution; accuracy, the foregoing process of purification or, instead of testing with surar, acidifA the should be resorted to in order to remove a reliquid and add sulphuretted hydrogen.'Tile ducing substaincee kinown as glucic acid (Grafiltrate itself nust be colorless, oand firee fion hain & others, Journ. London Chem. Soc., 5. the last tinge of brown If' any excess of 235), vhich accoiianiilies the sugar in such copper or suiar is found by tlhese trials, the liquids. - To clarify dark colored vegetaexperiment should be repea ted. Except in ble juices, heat a measured quantity of the practised handls, the first experiment will iuisu- liquid just to boiling; add a feiw tdrops of' milk ally yield only an a.pproximnzte result. In the of lime, which will usually produce a copious second experieincnt take care to adcd alliost the precipitate of' albunmen, coloring matters, salts whole of the stuear solution required, anti then of calciuni, etc., filter the liquid through boneproceed cautiously to the end, Laddling only two black, ixash the precipitate thoroughly, alnd drops at a tiiie. Be:ri in lnind that the copper adtld the waslings to the filtrate. Then dilute solution nmuist be stronglyN alkalinie from first to the filtrate to 10, 15 or 20 times its original last. In case the,ugar solution is acid add volume'(Neubauer). - To determine the enough soda to the copper solution to counter- nmilk-sugar in milk, remove the Casein by addlact the acidity. The process yields very sat- ing acetic acid at the temperature of boiling, isfhictory results. clarify tile wvhey wvith a little white of egg:, an(d The second method (applicable to colored filter. Boil the filtrate for 1 hour with a little liquors) requires the same solutions as the first. iplphUrie acid, dilute tile liquid to 10 times the For the analysis? transfer 20 c. c. of the cop- volume of' the original miilk, and proceed as per solution to a porcelain dish, and add to it above. 80 e. c. of water, or of a highly dilute solution The processes in question apply only to of caustic soda. Or perhaps better, take a grape-sugar, ifruit-sugar, nuilk-sug:ar and glustill larger volume of the copper solution, and cese. In case cane-sugar is to be estimaltedi dilute it in the same proportion. Add a incas- in this waiv, as in the analysis of rnily vegetaurecd quantity of' the dilute so!utioll of sugar ble juices such as the juice of the sugari cane, to the contents'of the dish, but not enough to beet root, maple, etc., it must first be chang ed COPPER SAI,TS. to grape -sugar by boiling with an acid, as will grains of iodide of potassium in the form of be described under Sugar. Starch and Dex- crystals, free from iodate, into the flask, and trin, -anid substances whi(ch contain-: thq:e allow the salt to dissolve. Then proceed to bodies miust be treated like cane-sugar. titrate the fiee iodine with a solution of by3. Reduction of the copoer salt b/y.odide of poosulphite of sodlilmm In case iron is present, Pota ssium. When the solutionr of a cuprio' sxalt the copper must be precipitated as SulIhlide, is mixed with an excess of a solution of iodide an(l the latter rediss(lvel, befbro the Ilprocess of potassiuml, diniodide of copper and free now in question caln be employed!. Aciodine are formed in accordance with the fol- cording to Molr, (Titfirnmethode, 18.55,. 388) lowing equation:- impurities maly be got rid of by supersaturatCuSO4 + 2KI- Cul + I +K 2SO4,, ing the nitric acid solution with ainmmonia The insoluble diniodide of copper is precip- water, filtering and acidulating the filtrate itated, but the free iodine remlains dissolved in with chlorhydric acid. The nitrous acid is the excess of iodide of potassium, and its amount thus changed to nitric ac id, which does no may readily be determined bv titration with harml, and the iron precipitated as a h),drate; hyposulphite of sodium, or in any other suitable though if' much iron be present, sonime copper way, as explained under Iodine.' Each atomi will be dragged (lown by the firrie hy(lrate, of iodine ( 127) found corresponds to one and so lost. Fresenius, on the contrary, does atom of' copper, (- 6 =.3.4). - Th-el:actual not approve of Mohr's suggestion. I-e could analysis may be made as follows:-dissolve not obtain satisfactory results by operating in the copper compound in sulphuric acid, best this way, since a solution of nitrate of' amimonto a neutral solution, though the presence of a ium mi.xed with somle chlorhy dric acid, will in.no(lerate excess of free sulphuric acid does no a very short tilne begin to liberate iodine from special harm. Dilute the solution to:sole solutions of iodide of potassium. - It willbe definite volume in a mIeasuring flask, to such observed that Brown's mlethod of working, an extent that each 100 c.c. of' liquid may con- does away with this objection of Fresenius. tain from 1 to 2 grins. of cuprie oxide. Put 10 For a description of' the pi.ocess by Riimlpler, c.c. of a solution of iodide of potassium (1 to 10) see Journal plra(lt. Chem., 105. 193. into a large beaker, add 10 c. c. of the copper The process can be used in conjunction with solution, mix the two solutions and proceed Chhloride of Tin, as follows: —Place a weighed without delay to estimate the iodine which is quantity of the copper salt in a flask, dissolve set iree. The copper solution must not con- it in water acidulated with sulphuric acid, add tain any free nitric or fiee chlorhydric acid, an excess of a solution of iodide of potassium, ferric salts or nitrous acid; and all other sub- and a little thin starch paste. Shake the flask stances which would deconipose iodide of continually, and pour into the blue liquid fiom potassiumn, must also be arefuilly excluded. a burette a standard solution of' protochloride If' tllese rules be strictly attended to, tolerably of tin, until the blue color of the iodide of accurate results may be obtained by the pro- starch has disappeared. The liquid will then cess, though't can hardly be regalrded as a be white and cloudy fiom separatiou of subiomethod of wide applicabilit;. Itis commended dide of copper. Note how much of the chlolmby Fresenius, and by F. Muhr, (Zeitsch. cnalyt. ide of tin solution has been unsed, and from C(hien., 1864,. 3. 139.) as well suited for esti- another burette pour a one-tenth nornial solumating small quatiie.s of' copper. (1)e Haen, tion of biChlromate of' Potassium into the flask, Anna/len Chem. ancd Pl/ar,., 18)4 91. 237.) It until the blue color of' the iodide of starch is important not to leave the mnixturei of cupric reappears. As only half the iodine is set salt and iodide of potassium stmalding. The free, 2 equivalents of'copper must be reckoned titration: of the fiee iodinle mitust be )roceeded for each equivalent of iodine. The imethod -with at once. is of' but narrow applicability, since it cannot De Haen's method has been recommended be employed in presence of free nitric, chlorhyby E. 0. Brown, (Journ. London Chem., Soc., dric or acetic acids, f'erric salts, or other sub1857, 10. 65), fon' estimating copper in alloys, stances which decompose iodide of' potassium. such as gun metal and bronze, and in those The solution mnust not be too dlilute, nor should varieties of' commercial copper which contain the Inixture of copper solution and iodide of no very large quantities of' lead or iron. Ac- potassium be left ibor any length of time before cordinig to Percy it has been extensively used tie tin solution is added to the inixtllre. at the Royal Arsenal, Woolwiclh, to this end. (Mohr, 7itrirmnethode 1855, 1. 277.). Another As desecribed by Percy (Metallurgy), the pro- mIlethlod of estiimating copper by mleans of iodide cess is as follows:- Dissolve 8 or 10 grains of of potassium and clloride of tin, is referred to the alloy in nitric acid, and boil, to expel nitrous in Zeitsch analyt. Chewm., 1869, 8. 14. Two acid. Dilute the acidl solution with a little stanladard solutions arle employeeC, one of iodide water, and add carbonate of sodium, until a of potassium, and the other of' chloride of tin. portion of the copper remlains precipitated. 4. Reduction oq' copper salt by Sulphite of Add an excess of pure acetic acid to the imix- Sodium. Supersaturate the acid solution of ture,.transf'er the s; lution to a pint flask, and copper vithi ammonia water, add a solution of dilute it firther with water. Drop about 60 sulphite of' sodium to the mixture, and boil 216 COPPER SALTS. until the cupric salt is reduced. Expel the For Gibbs's method of bringing the metal in excess of sulphurous acid by boiling with an ore to the form of a sulphate, see under chlorhym dric acid, and estimate the Copper by Copper, prccipitation of by iron. meanls of ferric chloride and perlmnrllg:inate of 6. Reduction of the Colpper salt by H:Iposulpotassium. The niethod is said to be easier of phite of Sodium. See Sulphide of Copper. execution than that lepenldilg on the relduc- 7. Reduction of the copper salt by hot Hytion of tile copper salt with grape-sugfar, since drogen. See Copper, fixity of. it is difficult to wash out the whole of the 8. Reduction of the copper salt by metallic sugar from the precipitated dinoxide (Terreil, Iron. (Compare the processes described under Conmptes Rendlus, 1858, 46. 230). the head of Copper.) A process described by 5. Reduction of the copper salt by flypo- C. Mlohr (Annalen Chem. und Pharm., 92. phosphorous Acild. Add to the cold, slightly 97, and Mohr's Tiltirnmethode, 1855, 1. 203), acid, and not too dilute solution of sulphate depends upon the reduction of a slightly acid of copper, an excess of a soluble hypophosphite, solution of' the copper salt by iron and titrasuch as hypophosphite of magnesium, for exam- tion of the fierrous salt produced. ple, and heat the mixture gradually, until after CuSO4 + Fe = Cu + FeSO4. standling for some minutes between 80~ andl Place the coppei solution in a glass stoppered 90~, the hydride of' cofpper has entirely sepa- bottle, aci(lulate it very slightly with a few rated in coherent masses. It is best not to drops of' chlorhydric acid, add about 0.25 part allow the liquid to boil, in order that the sud- of pure chloride of sodium, and a number of den evolution of hydrogen gas which would pieces of soft iron wire. Close the bottle and result fromn decomposition of the hydride of let it stand at a temperature of 30~ or 40~. copper, if the latter were heated to 1000 may The reduction proceeds rapidly, so that the be avoided, and that the precipitate may be whole of' the copper will be precipitated in the obtained in a spongy, coherent form. It is course of 1 or 2 hours. It is essential that the easy to determine when the precipitation is solution must not be too strongly acid, lest complete, by testing a drop of the solution with some iron dissolve directly without taking part sulphuretted hydrogen water on a white plate. in the reduction. Neither must the solution No filter need be used, if the precipitation be heated too strongly, lest a basic ferric salt be effected in an assay flask; fobr the precip- be formed which ha's no action upon the peritate may easily be washed by decantation manganate of potassiumn. - When the rein the flask, and afterwards transferred to a duction is complete, as may be seen by the porcelain crucible by the method of inversion, absence of color in the liquid, and by the fact described under Chloride of Silver. After that a drop of' it tested with sulphuretted hyhaving been dried, the precipitate is gently drogen no longer gives a black precipitate, the ignited in a current of hydrogen, and is weighed solution is diluted with water to the volume of as Copper. It is essential that the substance to 300 or 500 c. c., and portions of 50 or 100 c. c. be analyzed should be in the formi of a sulphate, are taken out with a pipette and titrated with and that the solution should contain a little permanganate of potassium. (See Ferrous firee sulphuric acid. If nitric acid be present, Saits.) The purpose of' the chloride of sothe precipitation will be incomplete; and when dium, as well as the small quantity of free chlorhydric acid or a chloride is present, the acid, is to facilitate the reduction of the copprocess fails entirely, the copper being then per salt by increasing the conducting power of reduced to dichloride which remains in solution. the liquid. According to Fresenius, the proThe presence of iron in the form of sulphate eess gives unreliable results, sometimes as does no harm, and copper can be perfectly well much as 12 per cent too high. It would hardly estimated also in presence of manganese, nickel be applicable in any event to the analysis of and zinc. But the process is inapplicable in ores or alloys containing iron, in spite of presence of arsenic and antimony, even when Mohr's proposal to determine the iron by ittartrates are adtlded to the solution. As has self' in a separate portion of the substance, been already stated, the solution must not be after reducing the ferric salt with zinc, and too dilute. But the precipitation of the copper making an allowance fobr it. will be complete if a saturated solution of' the 9. Reduction of the copper salt by smetlallic sulphate is diluted with not more than 10 times Copper. its bulk of water befobre the addition of the hy- A. Levol's indirect copper test. Supersatupophosphite. The process yields excellent re- rate the copper solution with amniollia water, suits. Gibbs and otlhers, (American Journ, Sci., and p)our the clear solution into a widle 1867, 44. 210). mouthed bottle, which can be closed air tiglit As A. Wurtz (Bulletin Soc. Chirn. de Paris, with a glass stopper. Warm the bottle and 1866, p. 194) has shown, hydride of copper is dilute the solution with boilinmg water, until the precipitated when a mixed solution of' copper bottle is almost completely filled with it. and hypophosphorous acid is heated to 70~ and Place a weighed sheet of' bright pure copper the hydride when exposed to the temperature foil (see Copper as a reagett) in the liquil, of boiling, is reduced to mletallic copper with close the bottle, and set it aside- until the blue evolution of hydrogen. liquid has become completely colorless. Then CREATIN. 217 take out the strip of copper, wash it clean and the solution of creatin care must be taken dry and weigrh it. The loss of weight repre- that the sides of the dish above the liquid are sents the copper which was contained in the no hotter than the liquid, lest a part of the original solution: liquid be changed, and a brown ring formed, cucI2 + cu = 2cuCl. which would color the liquid in case it disThe process, which is an adaptation of solved in it. - The process of Liebig yields Fuchs's indirect iron assay (see Ferric Salts), less creatin than the improved llethods (lehas merit in so far as it is applicable to the scribed below. It is seldom used now-a-days. analysis of copper solutions in almost any of (Compare, Nawrocki, Zeitsch. analyt. Chetr., the acids. even nitric acid, no matter how 1865, 4. 339.) A mnodification of Liebig's strongly acid the original solution may be. process recently employed by Valentiner (see There must of course always be used such an Zeitsch. analyt. Chem., 1863, 2. 29) consisted excess of ammnonia that the whole of the sub- in extracting the flesh with spirit, according to salt of copper formed shall remain dissolved in Stredeler (see below), and afterwards precipit. But on the other hand, the process has the itating with baryta water, as above. great disadvantage of requiring a long time B. Stoadeler (.Journ. prakt. C'hem., 1857, for its completion. With a liquid containing 72. 256) pours upon the minced flesh, or'upon about 1 grin. of' cupric oxide, and using a strip that which has been rubbed in a mortar with of copper weighing 4 or 5 grins., the experi- moderately coarse glass powder, firom 1 to 1.5 ment takes about 4 (lays for its completion. times its bulk of spirit, heats the mixture (H. Rose.) According to Phillips (An- gently upon a water bath with constant stirnolen Chem. und Pharnm., 81; 208) and Erd- ring, andl presses out the liquid. After evapmann (Journ. prakt. Chem., 75. 211), the orating the alcohol, acetate of lead is added to process is apt to give incorrect results, and to the solution, the mixture is filtered and the indicate more copper' than the solution really excess of lead remove(l fiom the filtrate by contained. But Plessy and Moreau (Berg sulphuretted hydrogen. The filtrate from the und /iitten. Zeitung, 1860, p. 10, and 1861, p. sulphide of lead is evaporated to a syrup, and 168) have sought to improve the process. See the creatin allowed to crystallize from the latalso the recent improvements in the corres- ter. According to Nawrocki (Zeitsch. analyt. ponding iron assay, under Ferric Salts. CheinL., 1865, 4. pp. 338, 339), it is not well to B. Runge's indirect copper test consists in use strong hot alcohol for extracting creatin boiling the solution of copper, acidulated with fiomn flesh, since some of the fatty matters (hlorhydlric acid, but free florom nitric acid, feir- which go into solution in the alcohol cannot t'ic salts and other oxidizing agents, with a be completely separated from the crystallized weighed strip of' metallic copper. After the creatin without occasioning the loss of some of fluid has been decolorized, the strip of copper the latter. - In remarking on Stdlteler's is washed and weighed, as in A. The process process, Neubauer (Zeitsch. analyt. Chem., has lallen into disrepute. For the action of 1863, 2. 25) admits that the extraction with acids and other agents upon the strip of cop- spirit is easy, and that the creatin obtained is per, see Copper, properties of. remarkably pure. He was repelled firom the Creatin. process, however, on finding that the mother Principle I. Solubility in water and diffi- liquor from which the creatin had crystallized cult solubility in alcohol. contained a substance other than creatinin, Applications. Estimation of creatin in flesh precipitable by chloride of zinc, which would Methods. of course interfiere with the determination of A. The ol(l method of Liebig (Annalen creatinin. But since Neubauer has himself Chent. und Pharm., 1847. 62. 287, 293) of' ex- shown by subsequent researches that there is tracting creatin from flesh was as fobllows:- really no creatinin in the mother liquor in The finely minced flesh was well kneaded with question, this objection to Staedeler's process water, anl the fluid expressed by wringing the would seem to f:all to the ground. mixture, by slnall poitions, in coarse cloths, The difficulty just mentioned may be care beilng taken to stir the residue of the first avoided by extracting the flesh with water expression with water, and to again express the instead of with spirit, anIl in this sense Neuliquid. The extract was gradually heated to bauer (Zeitsch. analyt. C/lhen., 1863, 2. 26) has boiling to coagulate the albumin and coloring devised the following process:imatters, and from the filtrate the phosphoric C. Thoroughly nlix solne 200 to 250 grins and sulphuric acids were precipitated by ba- of the finely mniceed flesh with an equal rvta water. The filtrate from the barium pre- weight of' water, and heat the mixture during cipitate was carefully concentrated upon a 10 or 15 minutes to 55~ or 60~, upon a water water bath to about one-twentieth of its vol- bath, with constant stirring, so that the albuumne. The syrupy liquid was then set aside in min may begin to coagulate. Decant the a Ilmoderately warln flask to crystallize. The liquid and press out the residue by twisting it, cr.stls were separated from the mother liquor by small portions, in a piece of cotton cloth. by filtration [and washed first with spirit and Stir up the residue with some 60 to 80 c. c. of then with strong alcohol?]. In evaporating water, and press it thoroughly a second time. 2,18 CREATIN. Jeat the combined filtrates over a lamp, with wards with absolute alcohol, dry at 100~ and constant stirring, until the albumin is coin- weihl. The anhvdrous creatin tllus obtained ]lctely',ogncl1atcd, a.nd filter the liquid after it is completeily colorless, leaves no tra.e f' esihas become cAold.. In order to avoid the d(Pe when burned, an(d is absor!utely fiee -orom fbrmlation of much glue, it is imlportant not to creatinin. According to Neub:lier, alnd ieit the moistened flesh any longer than is Nxawrocki also, there is no eratinin in normnal:bsolutely necessary. 10 or 15 minutes heat- flesh; that which has been obtaine(l by other in- at 55~ or 60~ is amply sufficient to brinr observers has resulted fiom the decomposition all the soluble inoredients of the flesh into so- of creatin. See belkw, under properties of' crelution, and to contra ct the.flesh so that it meay atyin. mWhen the operation of extlraeting creabe easily pressed with the hand in a porcelain tin, as above described, is carefully conducted, strainer. To the thoroughly cold filtrate no creatinin can be detected in the mother!?olr the albumin add a solution of acetate of liquor, from which the crystals of creatin lhave dlead, as long as anry precil)itate is produced, separate(d. (Neu.baiuer, loc. cit., pp. 31, 32.) but avoid adding any appreciable excess of D. Na wrocki (Zeitsch.b tnrl!/t. Clhem., 1865, the acetate. Let the mixture stand for an 4. 332) employs a combination of Stmdeler's houri then throw it uponl a plaited filter, wash anld Neubauer's methods, as foliows: — From it twice and precipitate the excess of lead in 15 to 30 grnis. of musole is carefully fieed thse filtrate with sulphuretted hydrogen. After fiom lymph and bloodl ly Ineans of a clotlh, filterino the sulphide of' lead, there will be ob- and placed in a weighlled flask full of 95 per tained a liquid clear as water, which may be cent alcohol. The flask is carefully closed, concentrated over a small gas flame at iirst, if and again weighed; it is then warmed slightly, care be taken that the liquid (loes not boil; it and left at rest (luring 12 or 24 hours, in order must afterwards be evaporated upon a water that the nmuscle may harden and be nmade fit bath to the consistence of a thin syirup of for coiminution. The alcohol is then debright yellow color. This syrup is set aside canted into a clean dish, and the muscle is cut for 2 or 3 days in a cool place, in order that into small pieces by means -of scissors, and the creatin may crystallize. - The evapo- rubbed fine with- some pure sand. Pour some ration had better be made at first in a large almiost boiling' water upon the powder, and dish, but when the liquid has been reduced to heat the mixture from 3 to 5 minutes (but no a volume of 40 or 50 c. c., it may be decanted longer) upon a water bath, with constant stirand washed into a'small dish, and there fur- rin. -. It is better to treat the muscle with ther'evaporated to a volume -of about 5 c. c. hot water several times, anid to press the resiCare must be taken, however, not to push the due between whiles, than to digest it for half evaporation too far, nor to expose the resid(ue or three quarters of an hour upon the water too long to the action of heat. By the con- bath, for in the latter case it is easy to forml a tinued action of heat' the residue gradually quantity of glue which disturbs the subsequent:acquires a'brownish or'bro.wn color, while operationis. After each digestion in hot water sonle of the creatin is destroyed. To avoid the muscle is pressed with the hand in a bit this decomposition of creatin it is well to fre- of linen cloth upon a funnel. The pressed quently remove the dish from the water bath residue should be taken fiomn the cloth, and during the evaporation,:and to swing the liq- broken down with a glass rod before pouring uid about in the dish, so that no dry rings of the hot water upon it. From 3 to 5 doses or residue may form upon the sides of the (lish. hot water are sufficient to extract the whole of In case the syrup obtained is brown, no confi- the creatin. The aqueous extract and washdence can be placed, iii the results obtained ings are now mixed with the. alcohol in which from it; but if the.operation has been care- the muscle was hardened, and the liquid, is left fully conducted there will finlally be found alln upon a slightly warm water bath lntil the alabundant crop of crystals of colorless creatin cohol has evaporated. It is then filtered beneath a light yellowish mother liquor. through,,lvery: porous paper- such, as that The crystals of creatin are collected upon a iiade from wool,-:which is used in the arts for wei(hed filter as follows: - Decant the mlother filtering coffte. The perfectly cold filtrate is liquor into a very small beaker, and let the treated with the smallest possibhle quantity of crystals (irain. The decanted liquid, though acetate of' lead which will sufice to coiualmost absolutely clear, contains some snall pletely precipitate the phosphohoric and sulplhuisolated crystals of creatin; it mnay be mixed ric acids anti the albumlin which has remlained with 2 or 3 ti-nes its volume of alcohol of 88. in solution. But, as Neubauer has urged, an per cent in order to make it fit for filtration, excess of the acetate mnustl carleflly be avoided and then poulre(d into a smalll plain filter which if' correct results are to be obtaimnd. XWheln ma has previously been miloistened with alcohol. sufficient quantity of the acetate hIas been After the inother liquor has been filtered, wash added, the precipitate settles rapidly, and the out the crystals froml the dish by means of' the liquid,. which was opalescent. before, becomes filtrate, or in case of need, with alcohol of 88 clear and transparent, Since the flocculent, per cent, wash the dish and crystals once or adhesive precipitate easily clogs the pores of twice with aicohlol of' 88 per cent, and after- the:filter, as nmuch of the.. supernatant liquid CREATIN. 21 9 as possible must be decanted from'the precii.l-'Application. Estimation of creatin in- flesh. tate. It is well also to place a filter of the Milethod. Prepare an aqueous extract of coarse coffee paper within an ordinary filtel in flesh, as described above, under Principle I, order to prevent the clogging of the latter. Nawrocki's'i:TIlthod, and, after the alcohol has The precipitate is washed with water as qiickly been evaporated, add to the solution a feiw as possible. In case it sticks closely to the drops of very dilute sulphuric acid to reimove filter'loosen it with a glass rod. The reason the albumin. To the filtrate from the albumin for haste in washing is that some of the albu- add from 3 to 5 c. c. of dilute sulphuric acid, minate of' lead is liable to be decomposed by prepared by mixing 1 volume of' the monocarbonic acid fiomn the air, so that the filtrate hydrated acid with 19 volumes of water, and might become cloudy from the presence of boil the acidulated liquid 6 or 8 hours. Then albumin. - The clear filtrate is freed from decompose the sulphate of creatinin by hea-ting lead by means of sulphuretted hydrogen, the the liquid with carbonate of bariuml, filter, snlphide of lead is separated by filtration, and acidulate the filtrate with acetic acid, concenthe filtrate is evaporated at a very Inodlerate tra.te it to a small bulk, mix with several voltemperature. The temperature of the water nineS of alcohol, and after several hours filter bath must be closely attended to; a broad, flat and add an alcoholic solution of chloride of dish should be employed, and the liquid within zinc, as explained under Creatinin. Or init should be frequently agitated to prevent the stead of using sulphuric acid, acidulate the formation of dry rings. It is well to have the extract of flesh with acetic acid, heat the mixopening at the middle of the water bath so ture to coagulate albumin, and boil the filtrate srrall that only a very small portion of the for 6 hours with addition of about 2 per cent; bottom of the dish can come into immediate of acetic acid of 25 per cent. (Sarokow; contact with the aqueous vapor. By tha ex- Nawrocki, Zeitsch. anolyt. Chem., 1865, 4. ercise of due care and patience the liquid may 340.) The process yiells considerably less be reduced to a volume of 2 c.e. without creatin than the direct method as employed becomingr yellow to any noticeable extent. by Neubauer and by Nawrocki, and described Sometimes it remains absolutely colorless. Af' under Principle I. ter the syrup has been left for 2 or 3 days to Instead of operating as above, Valentiner -crystallize, the crystals are carefully separated (Zeitsch. analyt. Chem., 1863, 2. 29) boils from the mother.liquor and collected on a the filtrate from albumin with chilorhydric weighed filter. In case the mother liquor is acid, adds acetate of sodium to the boiled litoo thick, which is seldom the case, or when it quor, and precipitates the creatinin with chlo-.has almost completely evaporated on standing, ride of zinc. it may be diluted with a few drops of 50 pe I Proffperties. Creatin crystallizes in small cent spirit. The mother liquor should be al- rectangular prisms, which are transparent, lowed to drain away completely fronm the filter brillialit and pearly, and permanent in the air. before beginning to wash. The washing is ef'- The crystals contain 2 molecules of water of fected by means of 88 per cent alcohol fol- crystallization, which are expelled at the temlowed by absolute alcohol. The crystals are perature of 1000, 12'17 per cent of the weight dried at 100~ and weighed between two watch of the crystals being lost. Anhydrous clreatin, glasses. It is best to weigh twice, or until the in which form the substance is usually weighed, results of two weiThinos aorlee, in order to be must consequently be multiplied by 1.1:374, in sure that the creatil is anhyd dous. order to obtain the weight of' crystallized creaThe process gives satisf tctory results, and tin to which it is equivalent. 1 part of' clrysis doubtless the inost convenient and exact tallized creatin dissolves in 75 parts of' water method of estimating creatinr hitherto pub- at 18~ in a very small quantity of boiling walished. It is to be. commended in default of ter, and in 9400 par'ts of' cold, strong alcohol. better mnetaods, thouolh it ca-n lay no claim to It is much more easily soluble in weak alcohol the precision of the ordinary processes of' in- than in strong, and is nearly or quite insoluble organie analysis. - In Nawrocki's control in ether. It does not act on vegetable colors. experiments the weight of' the creatin found It dissolves in cold baryta water without varies, at the mnost, fieom 0.01 to 0.02 per cent change, but is decomposed when boiled with of the weig-ht of the mnluscle taken, and from baryta., water. It dissolves in dilute acids with 2 to 7 per cent of' the weight of' the creatin but little, if any, c.hange, but when boiled fbr fund. But since the quantities of creatin a long time with dilute sulphulic, chlorhydric range from 0.01 to 0.02 per cent, and the *or acetic acids, or heated fir some tiIme with limits of error from 0.01 to 0.02 per cent, the strong acids. it is completely converted to erroi of observation in an extreme case might creatinin. It is changed to creatinin also, amount to one-tenth of the entire quantity of when its aqueous solution is heated, and this creatin. Hence the utmost care must be ex- fact explains not only the small percentage of ercised in the experiments, and in the drawing creatinin found in flesh by the earlier obhservof conclusions fitom their results. ers, but the false impression that creatinin is a Principle II. Decomposition of by dilute, normal constituent of flesh (Neubauer, Zeitsch. b)oiling acids, with formation of creatinin. alnalyt. Chemn., 1863, 2. 33;. Nawrocki, ibid, 220 CREATININ AND CHLORIDE OF ZINC. 1865, 4. 336). Creatin dissolves in tolerably this difficulty can be in good part overcome by large quantity in a coldl concentrated solution mlixing the syrupy residue with fine sand beof' chloride of zinc, and wart-like crystals of a fore treating it with alcohol, but in that event compound of the two substances fbrm readily, solme of the sugar is (lissolved by the alcohol, especially on the addition of alcohol (Neu- and is liable to interfere with the subsequent bauer, loc. cit., p. 31). deposition of the compoundc of' creatinin and Creatinin and Chloride of Zinc. chloride of zinc. - The best way of proPrinciple. Sparing solubility of the coin- ceeding is to destroy the sugar by fiermentation pound in strong alcohol. at the start. To this end mnix 500 c. c. of the Applications. Estimation of creatinin and urine with a quantity of pure yeast, and set it of creatin after it has been chatlged to crea- aside in a tolerably warmn place. After the tinin, as above described,. completion of. the fiermentation add a mixture Method. To estimate creatinin in urine of milk of limne and chloride of calciumr, and measure out 300 c. c. of' the liquid, add to it filter the mixture after it has stood for 2 hours. milk of linme until an alkaline reaction per- Evaporate the filtrate on a water bath to the sists, and afterwards a solution of chloride of consistence of' a thick syrup, mix the residue calcium as long as any precipitate falls. Let with 100 c. c. of alcohol of' 95 per cent, transfer the mixture stand for all hour or two, then the mixture to a flask, and let it stand for sevfilter and evaporate the filtrate, and wash-wa- eral hours in the cold with occasional shakin(. ter on a water-bath almost to dryness, as rap- Then filter, evaporate the filtrate to about idly as possible. Stir into the concentrated 50 c. c., add the solution of chloride of zinc, warm liquor 30 or 40 c. c. of alcohol of 95 per and let the mixture stand in the flask for a cent, pour the mixture into a beaker, wash out week. Collect the deposit on a small weighed the dish with a small quantity of alcohol, anrd filter, and wash it with hot alcohol until the let the mixture stand 4 or 5 hours in the cold, washings cease to give any reaction for ebhloin order that all insoluble matters maly separ- rine, then weigh. In ease the microscopic ate. Filter the liquid through the smallest extamlination of' the dleposit reveals the'prespossible filter, and wash the precipitate with ence of any foreignl substance, confirm the small portions of alcolhol after it has been al- foregoing result by determining, the amount of lowed to drain thoroughly. In case the vol- zinc in the deposit. TI'o this end ignite the unie of the filtrate, is much larger than 50 c. c. contents of' the filter, expel the chlorine with set the beaker on a warm iron plate, let the nitric acid, boil and wash the residue with liquid evaporate to the bulk of 40 or 50 c. c., water and dry, ignite and weigh the Oxide of anti afterwards set it aside to cool. To the Zinc. (Gaelltgens, Zeitsch. analyt. Cheem., 1869, thoroughly cooled liquid add 0.5 c. e. of an'8 101.) alcoholic solution of chloride of zinc, abso- The process is simpler when creatinin is to lutely free from acid, and of specific gravity be estimated in pure aqueo(us solutions. The 1.2. Stir the mixture persistently, since such flilowing details apply to experiments made by agitation greatly facilitates the separation of Neubauer (l.c. cit., p. 35) to test the accuracy the precipitate, then cover the beaker with a of his process. A standard solution of purse glass plate and set it aside in a cellar for 3 or creatinin was prepared by dlissolvingr 0.8938 4 da)s. After the lapse of this time collect grm. of the substance in 2 or 3 c. e. of water, the crystals oil a weighed filter, taking care to and dilutin(t with absolute alcohol to the voluse the mother liquor, or filtrate for washing umne of' 160 c. c. Portions of' 50 c. c. each of the last portions of crystals out of the beaker. this solution were measured out, and to each When all of the crystals are upon the filter let portion there was added 0.5 c. c. of an alcothem drain thoroughly, and finally wash them holic solution of chloride of zinc of 1.195 with small portions of alcohol until the wash- sp. gr. Afterthe mixture had been allowed to ings are colorless, and no longer give any re- stand 48 hours in a cellar, the crystals were action for chlorine. The washing should be collected and weighed, as above (lescribed. thorough, but not too long. I)ry the filter and From 99 to 99.2 per cent of the ereatinin crystals at 100~, and weigh (Neubauer, Anna- taken was fobund again in each experiment. len; Chem. unrd Pha'rm. 1861, 119. 35). Nawrocki (Zeitsch. analyt. Chem., 1865, 4, According to Winogradoff' (Zeitsch. analyt. 335) estimates creatinin in the mother liquor C(hem., 1869, 8. 100), some inconvenience will from creatin as follows: - Mix the solution be experienced if the foregoing process is ap- with twice its volume of' alcohol of 95 per plied directly to the estimation of' creatinin in cent., Let the milky mixture stand at rest diabetic urine. The sugar in such urine is during 18 or 24 hours, and filter to separate an reduced by evaporation to the condition of a albumninous substance which collects upon the viscous mass, which is very difficulty miscible bottom and sides of the beaker. Add to the with alcohol. Moreover, some of the creatinin clear filtrate 5 or 6 drops of a concentrated alis converted into creatin during the process of coholic solution of chloride of zinc. After 3 evaporation, which is necessarily tedious, so or 4 days collect the crystals of the compound that less creatinin is obtained than was really of creatinin and chloride of zinc on a weilghed present in the urine. According to Gaehtgens, filter, wash thema first with alcohol of 70 or 75 CYANII)ES. 221 per cent, and afterwards with absolute alcohol, tin, especially when in presence of lilne or until chlorine cain no longer be (letected in the anllnonia. filtrate. Dry at 1000 and weigh. In app)ling Cyanhydric Acid. [Compare Cyanothe process tbr the estimation of the creatinin gen, below, and( in the fin(lina list ill the obtained by decomposing Creatin. as above Appendix. See also Cyanogen Comlpounds.] described, tile first drops of chloride of zinc P'riciple. Volatility of. produce a flocculent precipitate which must be Application. Estilmatiom of' cyanlydric acid remllovedl by filtration before the solution is set in all cyanides froml which it may be comaside to crystallize. pletely expelled by heating with chlorllydric A process emlployed by Schottin (cited in acid. Separation of cyanogen fiom many Annalen CAhent. und Pharm., 119. 40) and metals,. others for estimating creatinin in urine, con- MAethod. Fit a cork, or caoutcllouc stopper, sisted in evaploralting the urine. extracting the with two perforations to a small flask. Through residue with spirit, and treating the extract one holb of the cork thrust the point Of' a with baryta water, or with acetate of lead, - MIohr's burette, and through the other hole a after the alcohol had been expelled from it bent glass tube, the outer end of which is by evaporation; the mixture was then filtered, fitted air tight to a tubilated receiver, in the excess ot' barium or of lead was removed which a small quantity of a solution of caustic fromll the filtrate, and the latter evaporated to soda has been placed. Attach to the receiver the consistence of' a syrup froml which the a U-tube, and place in it also a snmall quantity compound of' creatinin and chloride of zinc of' a solution of' caustic soda, Fill the burette was then obtained. This process, however, with chlorhydric acid. Place the cyanide to yields very much less creatinin than that of be analyzed in the flask, together;with somne Neubauer, above described, and is objection- water, warm the mixture and, by opening the able, inasmich as some of' the creatinin ap- elip of the burette, let the ehlorhydrfe acid flow pear's to be changed to creatin during the into the flask by small portion:s, unlltil an excess; evaporations, and( so lost. of' it has been alddled. Heat the flask until the The original crude process of Liebig was to whole of' the cyanhydric acid has been expelled, treat the urine with lilme water and chloride aand estiimate the acid in the distillate as ex,of calcium, to separate the precipitate by fil- plained under Cyanide of Silver, Cyanide of trationi, and evaporate the filtrate until the Silver and of Potassium, or Cyanide of Potasgreater part of the salts had crystallized. The siUm. The reason why the chlorhydrie acid in mother liquor poured off' from the crystals in. added by instalients's that free cyvanhydrie question was treate(l with one-twentyfourth acid is easily changed to fiomin acid when of' its veight of' a syrupy solution of-'hloride heated with the mineral acids, By operating of' zinc, and the mixture set aside for some as above, howeverls there will, never be any firee days to crystallize. chlorhydric acid in the flask until the close of Properies. As precipitated fiom alcoholic the operation, after all the cyanhyldrie. acid has solu;tiolns, the compound of' creatinin and chlo- been expelled. ri.de of zinc is a crystalline powder of light Cyanide of Cadmium. yellowish color. Under the microscope this Principle. Solubility in an aqueous solution powd er appears to be composed of' well de- of cyanide of' potassium. fined balls of' various sizes, transparent and Applications. Separation of Cd from Bii yellowish.. When m.agnified 400 diamletels, and Pb. concentric stripes are plainly visible. When Mlethod. See Carbonate of Bismuth.. Comprecipitated firom a solution which: contains pare Cyanide of Copper. sugar and clhloride of' sodlium, the presence of Cyanide of Cobalt. transparent octahedral crystals mlay be de- Princizle. Solubility in an aqqueous solution tected with the nIicm'oscopge. In ease there are of' cyanide of potassium. amorphous white particles colmmingled with Applications. Separation of Co from mNii, the compound of chloride of' zinc and crea- Mn,- Zn, Ca, Ba, Sr, Mg and.i1. tinin, a compound containingr phosphoric acid. Methods. See the Cobaltcyaynides of Potasis present, and this phosphlloric acid would go to sium and of Zinc; Cyanide of ManRganese, anad contaminate the zinc it' that substance were Carbonate of' Cobalt. For separati.ng Co,fronl determined for the sake of control. - 1 part Al it is only necessary to add. an excess of' a of the compound is soluble in about 9200 parts solution of' cyanide of potassiur,, and avoid of alcohol of' 98 per cent, and in about 5700, warming the mixture.. Hydrate of Aluminum parts of' alcohol of 87 per cent, at a tenllpera- will r'emain undissolved. For separating Co ture of' 15~ to 20~. It is readily soluble in fioma Mg, precipitate with carbonate of' potaswater, and slightly soluble in ether; yeast has siuln, add an excess of cyanide of' potassium no action upon it. Its composition mnay be to dissolve the carbonate of cobalt; add soimle represented by the formula, more carbonate of' potassium, and boil the C4H-7N30, ZnC12. mixture down to dryness. On treating the It may here be mentioned that creatinin, when residue with water all the Carbonate of' Magin aqueous solution, is slowly changed to crea- nesium will be left undissolved. (Haidlen & ~_2,22 2 CYANIDES. Fresenius, A1annlen Cein. und Pharmo, 1842, simple cyanides, but of many double cyanides, 43. 141.) such as Prussian blue, ferro- and f erri-cydanites, Cyanide of Copper. and the double cyanide of' nickel and pota:sP'rinciple. Solubility in an aqueous solution sium; but not of the cobalticyalnides. Iln genof cyanide of potassium; - or solubility in wa- eral terms it!nay be said that the process is ter of the double cyanide of copper and potas- applicable to those compounds of cyanogen miu!lm..'which a-re not easily soluble in nitric acid., and A]pplications. Separation of Cu fiom Bi'precipitable by nitrate of silver. The and Pb. details of the process are as follows: - Boil Method. See Carbonate of Bismnuth, insol- the compound in water, to which a decided ubility of' in cyanide of potassium. It is excess of oxide of mercury has been added, to be remembered that commercial cyanide of for a few minutes, or until complete decoinpopotassium contains carbonate of potassium, sition has been effected. In case iron is presand that when a solution of it is added to a ent add nitric acid, drop by dIrop, to the, hot solution of bismuth or lead, carbonates of these liquor until the alkaline reaction has almnost, metals are thrown down. - To prepare the but not quite disappeared, in order that the filtlate for the estimation of the copper, boil it liquid, which would be muddy if not thus with some chlorhydrie acid, to which a little treated with acid, mav be ma(le fit for filtranitric acid has been added. (}Iaidlen & PFe- tion. Collect the sesquiOxide of Iron on a senius, Annalen Chlem. und Pharm., 1842, 43. filter, and determine the cyanogen in the filpp. 134, 135, 1.43.) trate by precipitation, as Cyanide of Silver Cyanidei of Cold. using the requisite precautions (HI. Rose' Principle. Solubility in an aqueous solution Zeitschi. analyt. Cliem., 1862,!. 297). Atof cyanide of potassium;-or solubility in wa- tempts to substitute oxide of silver for oxide ter of the double cyanide of gold and potas- of mercury in this process resulted in failure. siumrn. Not only does some of the cyanogen escape in Applications. Separation of Au fromn Bi the form of ammonia on long continued boiland Pb. ing of the mixture, but the cyanide of silver Method. See Carbonate of Bismuth. To finally obtained is impure, and there is always estimate the gold in the solution, boil the lat- much less of it than there should be (H. Rose, ter with chlorhydric acid to expel the cyanhy- - loc. cit., p. 304). dric acid, and precipitate the Gold with a Principle II. Power of resisting nitric aci reducing agent. reducing agent. Application. Separation of Hg fiorn Cd. Cyarnide oT ianganese.e iMethod. Add a solution of cyanide of po-:;rncipoe. D ifficult s61hblity of the cyanPrincle.1 Difficult solubility ot' the cyan- tassium to the mixture until the precipitate ide in an aqueous solution of cyanide of potas- icors at first has redissolved, then add which forms at first has redissolved, then add ApplicationU S. fan excess of very dilute nitric acid, and boil. pplication. eparation of an from Co. tThe cyanide of mercury is not decomposed, Method. Add a considerable quantity of but the cyanides of adiu and potassi cyanhydric acid to the solution of the two e c metals, then some soda or potash lye, and re chnged to nitrt wavrm the mixture. The cyanide of cobalt cyanhydric acid has been expelled, throw warm the mixture. The cyanide of' cobalt down the cadmium as a Carbonate, and estiwhich is precipitated at first, will dissolve com- down the micury in the fiCtrate therestip!etely, while most of the cy anide of manga- a lt b..(1aidlen & Fresenius, Annalen Chem. und nese remains undissolved. i lter and oil the Parm. 142 43. 145.) filtrate with finely pulverizedl oxide of mercury to precipitate the rest of the Oxide of Principle II. Decomposability of by variManganese. Ignite the two' man[ganese pre- ous aents. cipitates together, and weigh as Mfanganite of Application. Separation of cyanogen frorn iManganese. Estimate the cobalt in the fil- mercury, as a step preliminary to its estimatrate, as explained under Cobalticyanide of tion. Potassium. See also under that head the pro- JMethods. Cyanide of silver is not precipcess to be followed for separating cobalt from itated when a soluble silver salt is added to a a mixture of nickel and manganese. solution of cyanide of mercury. On the conCyan ide of Mercury. trary, a somewhat soluble crystalline compound rili((l e I. Solubility in water. of the two cyanrides is fobrnmed. Hence the neApplications. Separation of cyanogen fiom cessity of resorting to indirect methods in ormetals, -as a step preliminary to its estimation. der to convert the cyanogen of the cyanide of 3lethAod. Many metallic cyanides may be mercury into Cyanide ot Silver, or into some compietely decomnposed by boiling them, either other form in which it niay be estinmated. as solutions, or in the form of fine powder, A. One way is to distil the cyanide with with an excess of oxide of mercury, all the chlorhydric acid, as described under Cyanhycyanogen being obtained in solution as cyan- dric Acid, volatility of. ide of mercury, while the imetals are changed B. Another way is to precipitate the iuerto oxides. This fact is true, not only of the cury as Sulphide of Mercury, though after CYAMDI)ES. 223 that has been done it is still difficult to esti- Cyanide of Palladiu; m. -mate the ervanoelen inl the filtrate. Principle. Insoilbiiitv ill v.ter. C. Another way is to precipitate the Mer- Application. Estimlation of Palladium. curv as such, by means of phosphorous acid.:llethod. Add carbonate of sodium to the:). A far better method recently devised solution of protochloridue (of palladaum until by H. Rtose (Zeitsch. anal yt. Chem., 1862, 1. the latter is altost neutralized, then add a pp). 294-296), is as follows:- Dissolve the solution of cyanide of mercury, antd leave the yanide of mercury in 300 parts of water. and mixture in a warm place. If the solution is add to the solution about 2 parts of nitrate of dilute some little time will be required in order zinc dissolved in ammonia water. Add more that the yellowish white precipitate of protothan enough pure potash lye to the mixture to cyanide of palladium may subside completely. combine with thle whole of the cyanhydric and Collect the precipitate upon a filt:er, wasl, (3ry nitric acids, and afterwards as much ammrlonia and ignite it, and weigh the Palladium which water as may be needed to make the solution is left in the crucible. In case the original clear. Add sulphuretted hydrogen water by solution contains any nitric acid it must be instalments, until the last portion added gives evaporated to dryness with an excess of ehloronly a perfectly white precipitate of sulphide hydlrlc acid, before proceeding with the precipof zinc. Let the mixture stand for quarter of itation, in order that the precipitate obtained an hour and then filter. Wash the mixed pre- may not deflagrate when ignited (Wollaston). cipitate of sulphide of mercury and sulphide Cyanide of Potassium. of zinc with very dilute almmonia water,'Pri nciple 1. Decomposition of by free which seems to take up the cyanide of zinc iodine. better than water would. The filtrate con- Applications. Volumetric estimation of cytains cyanide of zinc, nitrate of zinc and anhydric acid and of cyani(le of potassium. ammnonia. It does not smell in the least of aiethod. The reaction upon which the procyanhydric acid. To determine. the cyanogen cess depends may be expressed by the equaadd nitrate of' silver to the filtrate, acidulate tion: with dilute sulphuric acid, wash the precipi- KCN + 21 KI + ICN. tate somewhat by decantation, and then heat The standard solution of iodine may be preit with a dilute solution of nitrate of silver pared by dissolving 40 grins. of iodine in a in order to remove any cyanide of silver wlhich litre of alcohol, and testing with hyposulphite may have been precipitated with it, before of sodium to determine its real strength; or, throwing it upon the filter. Wash, dry and perhaps better, by dissolving the iodine in a weioh the Cyanide of Silver in the usual way. solltion of iodide of potassium, as explained Good results may be obtained also by using under Iodine. 5 grms. of the cyanide of poonly anmmlonia water and omitting the potash tassiumn to be examined are weighed out, and lye after the addition of the nitrate of zinc; dissolved in water to the voluhme. of 500 c. c. and the point is one of importance in cases 50 c. c. of this solution corresponding' to 0.5 where potassium is to be determiined, as well grm. of the salt are measured out into a flask of as when no potash lye firee from contamination 2 litres capacity, and there mixed with 1 litre of chlorides is to be had. of water and 100 c. c. of Seltzer water; the E. Still another method devised by Rose purpose of the latter being to change the alkali (Zeitsch. analyt. Chem., 1862, 1. 296) depends present to the condition of a bicarbonate, on the reduction of the mnercuric cyanide by which will not absorb iodine. The flask is imeans of nmetallic cadmium. The cyanide of placed on white paper, and the standard iodine -mercury dissolved in firom 25 to 30 parts of solution poured into it, until a permanent yelwater is digested in a stoppered bottle for 36 low color is produced. The cyanide tested hours with an equal quantity of cadmium must be free fiom sulphide of potassium. The filings. The liquid is then poured out and average strength of the commercial cyanide is treated with nitrate of silver and nitric acid said to be about 55 per cent. - If the subin the usual way. A small quantity of cyanide stance to be examined is an aqueous solution of cadmium which adheres to the bottle as a of fi'ee cyanhlydric acid, mix it careftdlly with white deposit, must be dissolved in acetic acid a solution of soda to alkaline reaction, add and added to the rest. The process yields ap. some carbonic acid water, either Seltzer waproximative results when applied as above, ter or soda water, until the fluid no longer but is worthless when the solution of' cyanide turns turmneric paper brown, and add the iodine of mercuiy is highly dilute. Neither zinc nor solution as before, until the liquid becomes iron can be used in place of the cadmium. permanently yellowish. 2 atoms of iodine cor — Cyanide of Nickel. respond to 1 equivalent of cyanogen, cyanhy79rinc'ile. Solubility in an aqueous solu- dric acid or a cyanide. The nlethod gives tion of cyanide of potassium. satisfactory results, but is not applicable to the Application. Separation of Ni from Co, Ca, valuation of bitter almonJ water (Fordos & Ba, Sr, Mg and Al. Gelis,.1ourn. prakt. Chem., 59. 255). AccordMlethod. See Cobalticyanide of Potassium ing to Souehay (Zeitsch. analyt. Chemn., 1863, and Cyanide of Cobalt. 2. pp. 176, 180) the close of' the reaction is 224 CYANIDES. indicated plainly enoughl. The process lain crucible until it ceases to lose weight. naiv be use(d finr sep)arating CN from Cl, Br The ignition may be completed in a quarter of tuni I, by deterinining the cyanotgen in one an hour at the temperature of' redness. It is portion of the mixture as above, and throwing neither necessary nor admissable to heat the sildown and weighing everything in the form of ver to the melting point, nor is any thing gained insoluble silver salts (see Chloride of Silver) by igniting the cyanide of silver in a current in another portion. of hydrogen. The metals in the substance anPrinciple IL. Power of reducing copper alyzed are determined in the filtrate from the salts. cyanide of silver after the excess of silver has Applications. Estimation of Cu and of' CN. been separated therefrom. The object in addMethod. See Copper Salts, reduction of by ing the nitrate of silver to the solid cyanide cyanide of' potassium. rather than to its solution is to avoid the loss For use as a reagent, cyanide of potassium of those traces of cyanhydric acid which exmay be obtained pure enough in commerce. hale from aqueous solutions. It is fbr a simiIt should be of a pure milk white color, free lar reason that the nitric acid is added after, from specks of iron or charcoal, and should dis- an(l not before, the silver salt. Care must alsolve in water to a perfectly clear liquid. It ways be taken to avoid an unnecessary excess should neither contain any sulphide of potas- of nitric acid, for cyanide of silver is somesium nor silicic acid. In other words it should what soluble in that acid, especially if it be give a white precipitate when tested with ace- warm (H. Rose, Zeitsch. analyt. Chem., 1862, tate of lead, and should leave no residue insol- l. 199). uble in water when evaporated to dryness, In the case of a solution of free cyanhydric after addition of chlorhydric acid. The uses acid in pure waler mix the rather dilute soluof the cyanide are to precipitate certain me- tion with a solution of nitrate of silver in extallic cyanides, as above described, and to dis- cess; then add a little nitric acid and proceed solve certain other cyanides, oxides, sulphides as before. - But for estimating cyanhydric and carbonates (see, for example, Carbonate acid in bitter almond water or cherry laurel waof Cobalt). It is used also as a reducing ter, add anmmonia water in strong excess to the agent, as explained under the heading Copper mixture, after the addition of the nitrate of Salts. The commercial cyanide, prepared by silver, until the precipitate has all dissolved, Liebig's method, always contains some carbon- and then immediately add nitric acid to slight ate and cyanate of potassium. It precipitates acid reaction. The precipitate thus obtained'many metals as carbonates, when added to will contain the whole of the cyanhydric acid their solutions. which was present in the original solution, but. Cyanide of Silver. any precipitate thrown down directly ifronl the Principle 1. Insolubility in water acidu- original solution, or from that solution after lated with nitric acid. acidulation with nitric acid, would contain only Applications. Estimation of cyanhydric acid a part of the cyanogen. The addition of the in pure aqueous solutions, as well as in bitter anmmonia water is an indispensible necessity to almond water, cherry laurel water, etc. Sep- success, but, on the other hand, the ammonia aration of CN from Na, K, Cu, Sr, Ba, Mg, must not be allowed to act for any length of Zn, Cd, Mn, Co, Ni, Pb, Cu and Bi; but not time, lest a portion of the cyanogen be lost from Hg. Separation of H2CN from As203, (Souchay, Zeitsch. analyt. Chem., 1863, 2. As205, CrO3, SO3, P205, B203 and HFI. Pre- pp. 177, 180). cipitation of CN as a preliminary step to its According to Feldhaus (Zeitsch. analyt. separation from C1, Br and I. Estimation of Chem., 1864, 3. 36), bitter almond water consilver. Separation of Ag from Hg, Cu and Cd. tains, when fresh, cyanhydrate of benzaldeMllethods. The method now in question is hyde, free benzaldehyde, free cyanhydric acid esteemed to be the best, and is indeed almost and cyanide of' am nonium. But only the last the only direct method of estimating cyano- two of these solutfns are acted upon by a sogen. But there are comparatively few com- lution of nitrate of' silver at the ordinary teinpounds of cyanogen from which cyanide of perature. In order that the cyanogen of the silver can be precipitated directly. Hence the cyanhydrate of' benzaldehyde may be comnecessity of several modifications of the pro- bined with silver it is necessary to decompose cess, as will be described. this compound by means of potash or ammoA. Graaimetric. nia. But care must be exercised in doing If the substance to be analyzed is a solid cy- this, for an excess cf the alkali must be used of anide of an alkali metal pour upon it a solution necessity, since it is a matter of experience of nitrate of silver, and afterwards, water, and that one equivalent of the alkali-or, indeed, acidulate slightly with nitric acid. Allow the several equivalents-are insufficient to effect precipitate to settle without warming the. mix- this decomlposition; while, on the other hand, ture, then collect it upon a weighed filter, any long continued action of the alkali would wash with hot water and dry at 1000, or collect induce other decompositions, and tend to dithe precipitate upon an unweighed filter, and minish the amount of precipitable cyanogen; instead of drying at 1000, ignite it in a porce- hence it has lon, been customary to add ni This signature is not to be bound in the completed volume. APPENDIX TO PAiT Ie EXAMPLES FOR PRACTICE. Examples are here given more for the sake Valuation of Arsenious Acid. of roughly indicating the method which will Select a sample of arsenious acid, pure' be followed in the appendix to the finished enough to volatilize completely when heated work, than on account of any special merit on platinum foil. WVeigh out two portions of which may attach to the examples themselves. the substance, each of' about 0.5 grin., and Though none of these examples can be re- estimate the arsenic contained in them, by the garded as specially difficult, the beginner, be- methods described under Arseniate of' I,ead fore undertaking either of them, will of course and Arseniate of Magnesiumn and Ammonium. perfornm several simpler experiments,-4such as are described in almost any treatise on quanti- Estimation of Lead. tative analysis. See, also, a few simple exam- Weigh out about one gramime of pure, dry ples on the next page, at the close of' the list. nitrate of lead, dissolve it in water and determine the lead by the method described under' The following examples are taken fiom Part Carbonate of Lead. I. (pages 1 to 112). - The completed volume will contain five such parts. Analysis of Sulphide of Atimony. Ancal~ysis of Hi~iarble. Treat about 0.3 grm. of the pure, crystal, lized native sulphide, as directed under AnGrind a quantity of pure white marble, or timony Compounds. better, Iceland Spar, to powder, dry the poEwder at 1000 and weigh out three portions of' it, Estimation of.Vitric Acid. each of about one gramme. Weigh out about 0.5 grim. of pure, dry Place one portion in a beaker covered with nitrate of potassium, and proceed as directed a watch glass, dissolve it in dilute chlorhydric under Arsenious Acid (Method F). acid and determine the calcium by precipita-tio o ia..Estimatoon of Amnmonia. tion, as Carbonate of Calcium. In another portion estimate the Carbonicon 0.6 to 1 gr. of pre clo Acid by Johnson's method, see p. 84; and in ride of' ammonium, and proceedl as directed the third portion estimate the carbonic acid by under Amilnonia, volatility of (Method A). the method of absorption in alkali, see p. 91. Separation of Ironfro, Magnllnesium. To control the amount of calcium, weigh,To control the amount of (adocium3, weigh of Dissolve about 0.2 grin. of the finest iron out a fourth small portion (about 0.3 grin.) of i in chlohydric ai mi wih nitric, znM / wire in chlorhydric acid inixed with nitric the original marble, heat it intensely over a cid. Al to the solution about 0;8 grm. of blast lamp to expel the carbonic acid, randently crystallized Epsom salt, dlute weigh the oxide of calcium which is left. t ixture a proeed to precipitate the Again heat and weigh, and repeat the opera- iron as Acetate of Iron. Ieternline magnetions until the results of two successive weigh- sin in the filtrate as Phospha7te of Magnesium ings are the same. The amount of calcium in and Amonium the residue is found by the proportion:-oiec. Wt.'of an " Wt.of W~t.of Ca Separation of A ntimony from Tinl, Ct a ( of 40 atom of) rende ( e ictne ) See Antlimonyl 0 Method B. 8 2 APPENDIX. Valuation of Carbonate of Sodium. the carbon and hydrogen by Method 2, above 1. By Alkalimetry, through neutralization. cited. The amount of oxygen in the tartaric 2. By fusion with bichromate of potassium, acid is obtained from the difference. The see p. 80. composition of pure tartaric acid is:3. By Rumpf's method, see p. 88. 4 = 48 32 H6 = 6 = 4 Valuation of Acetic Acid. 06 5 64 By several of the methods described under E ro ~~~~~~~that head. ~Estimation of Carbon in Cast Iron. See Carbon, Principle I, Methods B and C. Valhuation of Blecaching Powder. By Penot's method (the chlorine acting upon Separation of Bromine from Chlorine. arsenious acid in an alkaline solution). See Dissolve about 0.8 grin. of pure bromide of Arsenious Acid. potassium, and from 2 to 3 grms. of pure chloride of sodium in two or three hundred c. c. of water; precipitate with nitrate of See Alcohol, Principle III. silver (see Bromide of' Silver), and treat portions of the dry, weighed precipitate as described under Bromide of Silver, Principles II Weigh out from 0.3 to 0.4 grin. of pure, dry and III. oxide of magnesium, prepared by igniting the oxalate; and about 0.5 grim. of pure, dry Estimation of Carbonic Acid in AtmosphericAir. chloride of sodium. Dissolve the mixture in By Pettenkofer's process, see page 97. dilute chlorhydric acid, and proceed as de- Estimation of Carbonic Acid in "Sod-water" scribed under Carbonate of Magnesium and of Ammonium. Determine the Sodium in the By the method of Fresenius, described on filtrate as'Chloride of Sodium, page 101. Analysis of Organic Compounds. Indirect separation of Barium firom Strontium. A. Prepare a quantity of oxalate of lead, See page 80 by precipitation; wash it carefully, dry at 1000 and weigh out three portions, of about 0.6 As examples of simpler experiments, fit for absogrm. each, for analysis. Burn one sample lute beginners, may bementioned:A. The precipitation of iron, by ammonia, as with oxide of copper, affter Liebig (see Carbon, hydrated sesquioxide, and its estimation as ferric Principle II, Mlethod 1), another by Bunsen's oxide. As the starting point, weigh out from 0.3 to mollification (p. 61) of that process, and a 0.4 grin. of fine, tough, iron wire and dissolve it in third wilth' oxide of' copper and oxygen, as pure, dilute chlorhvdric acid mixed with a small quantity of nitric acid. explained under Method 2. B. The estimation of sodium in chloride of soThough oxalate of lead contains no hydro- dium; by adding an excess of pure, diluted sulphuric gen, the student should nevertheless weirh the acid to a weighed quantity (fiom 0.5 to 1 grm.) of chloritde of' alcium tube before and af'ter each pture fused chloride of sodium, evaporating to expel colmlbustion, in order to gain souidea of' the chiorhydric acid and the excess of sulphuric acid, combustim, in ortier to gain soe idea of' the and weighing the sulphate of sodium. errors whichl nla be introduced through the C. Estimation of chlorine in chloride of sodium absorption of atmospheric moisture by oxide of by precipitating, with nitrate of silver, as chloride of copper. silver. B. Weirh out about 0.4 grm. of pure, D. Estimation of silver in chloride of silver by decomposing the latter with pure metallic zinc, in crystallized tartaric acid, which has been pre- presence of dilute sulphuric acid, and weighing the viously powdered and dried at 1000. Estimate metallic silver. FINDING LISTS, FOR METHODS OF SEPARATING ELEMENTS. ALUMINUM: Separation of from Bi: See Sb2O. As: See MgO, (NH4)2 O. As205, - and Ar- Cd: See Sb205. seniomolybdate of Ammonium. Co: See Sb2O0;- Sb203, and Sb. Ba: See A1203, Acetate of. Cu: See Sb20; - Sb2O3, - and Sb, Ca: See A1203, Acet.; B- aO, CO2, - and Au: See Sb203,- and Sb. MgO, CO2. Fe: See Sb205;- Sb203, — and Sb. Co: See A1l0, Acet.; - Na20, A120l; - Pb: See Sb20,. BaO, CO2, - and CoO, Co2. Mg: See Sb2O5. Fe: See A1203, Acet.; - NaO, A12O3, - Mn: See Sb2O. and BaO, CO2. Hg: See Sb205. Li: See A1203, Acetate of. Ni: See Sb205; -Sb203, - and Sb. Mg: See A1203, Acet.; - Na2O, 2B203; K: See Hg20, Sb20-. BaO, CO, -- and MgO,CO~2 Ag: See Sb2O;- Sb20,- and Sb, Mn: See A1203, Acet.; — Na2O, A1203;- Na: See H20, Sb20,. BaO, CO2, - and MnO, CO2. S: See Sb203. Ni: See A1203, Acet.; - Na2O, A1203; Sn: See Na2O, Sb202, - and Sb. BaO, CO, - and NiO, CO2. Zn: See Sb202. P: See BaO, CO2. K: See Al203, Acetate of. ARSENIC: Separation of from Na: See A12O3, Acetate of. Al: See MgO, (NH4)20, As205, — and ArSr: See A1203, Acetate of. seniomolybdate of Ammonium. Ur: See A1203, Acetate of. Zn: See Al2O3, Acet.,- and BaO, CO2. As2e;- Sb20; Sb;As N [For thle decomposition of refractory alumin- ee O. (20As: See M4gO, (NH4)20, AsO,, — and As2O3. ates see Na2O, A1203; — BaO, C02, - and0, A s Ba: See HO20, As2O3; - FeO3, AsO3; — NO, 2BO0,1. K20, As2O,;- UrO3, As2sO; - As;AMMONIUM: Separation of from As2O3;- AssOs;- BaO, CO2,- and ArAll the elements: See Ammonia (Princi- senionolbdate of Ammonium. pie III) and Ammonium Salts. Bi: See As; — As203, - and Arseniomolybdate of Ammonium. ANTIMONY: Separation of from Br: See AgBr. Sb: See Sb203. Cd: See Ag2O, As2O3; - MgO, (NH4)20, As: See NaO, Sb20; - MgO, (NH4)2, AsO; - As; - As20, - and ArsenioAs20O;- Sb, - and As. molybdate of Ammonium. 4 A PPENDIX. Ca: See HI~fo(), AO205; - Fe203, AO,;- -PBO, CO, -and Arseniomolybdate of K20, As0- U 0 Li 0,S A0) As; —; AsllAmloniLun. As -- B3.:tO, CO,,, —- and - A1rSenliom1o11903; y1bO Cof O > anti.~Rniosno- ABRI 1 Separation of from lyblalite of Ainll lit lll. Cr: See Arsentil:l)1 vbl te of Aiinnoniutm. Al: See A1,0,, Acetate of. Co: See 1MgO, (NJI4)0, AOA20; H- IH20, As: See H-)O, As,0O;- As2O3; - Fe'O,, As90O; — Fe 0, As,O; - s; As203; As;,0 A- KO, As2O;- UrO3, As205;-BaO, CO2 - and Arseniomolybdate of As;- Ass0s; - BaO, CO2 - and ArsenAmmon Lim. iomiiolvbdate of Amlnonium. Cu: See HesO, As3Oa; — As2Oe; — Mige, Ca: See CO,, - and CaO,CO. (NtI4)20O, As2O'; 20,, tS205; - As;- C: See C, pp. 69, 79, 80;- and BaO, CO2. As203, - and Arsenlioolybdate of Am- Co: See BaO, CO2, -and CoO, CO2. nlonium. I:-I See B303. Fe: See MgO, (NH4)20, AssO2;;- AS20; — Fe: See Fe2Oa, Acet., - and BaO, CO2. IKO, As.203;- As; — AsO03, - and Ar- Mg: See BaO, CO2. seniomolybdate of Ammonium. -Ifn: See BaO, C02, - and MnO, CO2. Pb: See Hg20, AsO,; - As20; -As;- Ni: See BaO, CO, -and iNiO, CO2. As203, —and Arsenioenolybdate of Am- P: See BaO, CO. moniumr. K: See BaO, C2, - and MgO, CO2. g: See Hg2O,; - As20e; - Ur2O3, Na: See BaO, CO2. As20,; — As; - A s203, - and Arsenio- Sr: See C02, - and BaO, CO2. molybdate of Ammonium. Zn: See BaO, CO2. iMn:. See V~!gO, (Nlu4)2O, As20,; - As90;Fe203, iAs0,;- 0, As20; - As;- B3ISMUTH: Separation of from As203; — BaO, CO0, - and Arseniomo- Sb: See Sb20,. lybdate of Ammnonium. As: See As; - Ass03, and Arseniomolyblg: See As; - As23, - and Arsenionmolyb- date of Ammonium.n. date of Ammonium. Cd: See Bi2O3, CO, -and CdO, CO2. Ni: See MgiO, (NH4)2O, As2sO; - lg2O, Cl: See Bi. AsO20,;- Fe3, A As;O3; As; As03; Cu: See Bi03, C02, and CuO, CO. - BaO, C02, - and Arseniomolybdate Au: See Bi303, CO2. of Amllonium. Pb: See Bi. [K:'See MgO, (NH4)2O, As2eO; -- Hg2O, M1in: See Bi2O3, CO2, — and MnO, CO. As2e; - As2O; -- -I 3e2O, As2A; - Hg: See BiO23, C02. Ur203, As20O, - and Arseniomolybdate Ag: See Bi103, C02. of' Ammonium. S: See Bi. Ag: See As;- As203, - and Arseniomolybdate of AmmoniuLm. BORON: Separation of from Na: See MgO, (N114)20, As2O,;- HgO2, Most metals other than alkali-metals: See As2O,; -As2O,; - Fe2O, As2AO;- SnO2, Na2O, 2B203, 2 and CO2. As250; — Ur2O3, As20O, - and Arsenio- Br: See AgBr. molybdate of Ammonium. K: See MgO, BO03. Sr: See Hg2O, As20s; Fe203, As2s0;- Nla: See MgO, B203. K20, AsO2O; - Ur2O3, As20;- As;As203; - BaO, CO2,- and Arseniomo- BROMINE: Separation of from lybdate of Ammonium. Most metals: See AgBr. S: See As2O3. As: See AgBr. Sn: See SnO2, As 20, - and As. B: See AgBr. Ur: See M\IgO, (NH4)2O, As2O5. C: See HgBr; - AgBr; - Br, - and C, pp, Zn: See MgO, (NH4)20, AS2O; - Hg20, 64, 68, 71, 73, 74. As2O;- As2,;- Fe2O, As2O; K- O, Cl: See AgBr; - KBr;- NaBr, — and Br. As20;;-UrO03, As2O0; - As; -_ AsOs; Cr: See AgBr. APPENDIX. 5 Fl: See AgBr. Fe: See C, pp. 57, 58, 71, 75, 76. I: See KBr,- and Br. Pb: See CO2. P: See AgBr. Mg: See CO2, - and MgO, C02. Si: See AgBr. 1Ni: See CO2. S: See AgBr. N1i: See C, pp. 63, 68, 71, 73. K: See CO2;-K20, CO2, — and C, pp. 69, CADMIUIMI: Separation of from 79, 80. Sb: See SbO2. N -':;See C, pp. 69, 79, 80. As: See tig20, As2O5; - MgO, (NH4)20, Sr: See C02, -and C, pp. 69, 79, 80. As2O5; - As; — As203, - and Arsenio- S: See Ai(2O, CO2; and C, pp. 64, 71, 73, 74. molybdate of Ammonium. Bi: See Bi2O2, CO, - and CdO, CO2. CHLORINE: Separation of from C: See CO2. Bi: See Bi. Cu: See CdO, CO, —and CuO, CO2. Br: See AgBr; — KBr;-NaBr, - and Br. Pb: See CdO, CO2, -and PbO, CO2. C: See C, pp. 64, 68, 71, 73, 74. Mn: See CdO, C02,- and MnO, CO2. I: See KBr, —and Br. [For the estimation of chlorine " (chlorimCALCIUM: Separation of from etry)" see As Al: See A1203, Acet.; - BaO, C02, - and MgO, CO2. CHROMIUM: Separation of from As: See Hg20, As205; - Fe2O,, As205; - As: See Arseniomolybdate of Ammonium. (20, As205;- Ur2O3, As2O5; - As; Br: See AgBr. As2O;- BaO, C0, - and Arseniomo- Co: See BaO, CO2. lybdate of Ammonium. Fe: See BaO, CO2. Ba: See CO2, -and CaO, CO2. Mn: See BaO, CO2. C:- See C, pp. 69, 79, 80; - CO, - and Nii: See BaO, CO2. CaO, CO2. Zn: See BaO, CO2. Co: See CaO, CO2, - and CoO, CO2. [For the decomposition of refractory ChroFe: See Fe2O0, Acet., -- and BaO, CO2. mites see BaO, CO, -and Na2O, B203]. Mg: See CaO, CO2. Mn: See CaO, C02,- and MnO, CO2. COBALT: Separation of from Ni: See CaO, C2, - and NiO, CO2. Al: See A1203, Acet.; - Na2O, A1203; - P: See BaO, CO2. BaO, CO2, -and CoO, CO2. K: See BaO, C02; -- CaO, C02, - and Sb: See Sb20; —Sb2s, - and Sb. MgO, CO2. As: See MgO. (NH4)20, As2%O; - Hg20, Na: See CaO, CO. As2O0;-Fe203, As205;- As; - As20O; Sr: See CO2, — and CaO, CO2. - BaO, CO2, - and Arseniomolybdate Zn: See CaO, CO2. of Ammonium. Ba: See BaO, C02,-and CoO, C02. CARBON: Separation of from Ca: See CaO; C02, - and CoO, CO2. All bases: See CO2, -and C, p. 64. Cr: See BaO, CO2. Ba: See BaO, CO2,-and C, pp. 69, 79, 80. Fe: See Fe2O, Acet., -and BaO, CO2. B: See CO2. Ni: See (CaO, CO2; CoO, C02). Br: See HgBr; -AgBr;- Br, -and C, pp! Sr: See CoO, CO2. 64, 68, 71, 73, 74. Cd: See CO2. COPPER: Separation of from Ca: See C02;-CaO, C02, -and C, pp. 69, Sb: See Sb20s;- Sb3, - and Sb. 79,80. As: See Hg2O, AsO; - As205; - MgO, Cl: See C, pp. 64, 68, 71, 73, 74. (NH4)20, As205; - K20, As2O2;- As;Cu: See CO2. As2O3, - and Arseniomolybdate of AmH1: See C. nionium. I: See C, pp. 64, 68, 71, 73, 74,. Bi: See Bi20, CO2, -and CuO, CO2, 6 APPENDIX. Cd: See CdO, CO2, —and CuO, CO2. Zn: See Fe203, Acet.; - BaO, CO2,-and C: See CO2. Fe203, Benz. Pb: See CuO, CO2, - and PbO, CO2. LEAD: Separation of from Mn: See CuO, CO2, -and MnO, CO2. FLUORINE: Separation of from Sb: See Sb20O. As: See Hg20, As20O; — As2O5; - As;Br: See AgBr. As203, - and Arseniomolybdate of AmGOLD: Separation of from monium. Sb: See Sb2O3, - and Sb. Bi: See Bi. Bi: See Bi,. Cd: See CdO, CO2,- and PbO, CO2. Pb: See PbO, CO2. C: See CO2Cu: See CuO, CO2,- and PbO, CO2. HYDROGEN (and Water): Separa- Au: See PbO, CO2tion of from Mn: See PbO, C02, - and MnO, CO2. Ba: See B 0O. Hg: See PbO, CO2. C: See C. Ag: See PbO, CO2. K: See B103. iNa: See B203. LITHIUM: Separation of from Sr: See B203. Al: See A1203, Acetate of. IODINE: Separation of from As: See Fe203, As5, - and Arseniomolyb13r: See KBr, -and Br. date of Ammonium. C: See C, pp. 64, 68, 71, 73, 74. Fe: See Fe2 O, Acetate of. Cl: See KBr, - and Br. Si: See CaO, CO2, - and BaO, CO2. EFor the estimation of iodine, see As203]. MAGNESIUM: Separation of from IRON: Separation of from Al: See A12, Acet.; Na9O, 2B103;Al: See A1203, Acet.;- Na2O, A1203,-and BaO, CO2, -and MgO, CO,2 BaO, CO2. Sb: See Sb2O,, Sb: See Sb20O;- Sb203,-and Sb. As: See Hg2 0, As,20;- AS205; - Ur2O3, As: See MgO, (NH4)20, As205; - As2Os; As2Os; - As;- Ass2O3, - and Arsenio: -K20, As2Os; - As; - As203, -- and molybdate of Ammonium. Arseniomolybdate of Aminonium. Ba: See BaO, CO,2. Ba: See Fe2O,, Acet.,- and BaO, CO2. Ca: See CaO, CO2. Ca: See Fe203, Acet., -and BaO, CO2. C: See CO2, - and MgO, CO2. C: See C, pp. 57, 58, 71, 75, 76. Fe: See Fe203, Acet., - and BaO, CO2. Cr: See BaO, CO2. Mn: See MgO, C 02, - and MnO, CO2. Co: See Fe2O,, Acet.,-and BaO, CO2. K: See MgO, (NH4)20,As2 05; - BaO, Fe: See Fe203, Acet:; - BaO, CO, 2- and CO2;- -gO, CO2,- and [MgO, O,2; MgO, CO2. (NH4)02, CO2]. Li: See Fe0O3, Acetatd of. Na: See MgO, (NH4)20, AssOs, - and Mg: See Fe203, Acet., -and BaO, CO2. [MgO, C.02; (NH4)20, C02]. Mn: See Fe2O3, Acet.; - Fe2O3, As205;Fe2O, Benz.;- BaO, CO2, - and MnO, MANGANESE. Separation of from CO2. A1: See A1203, Acet.; N- Na2O, A1203;Ni: See Fe2O3, Acet.; - Fe2O3, As2Os; - BaO, CO, — and MnO, CO2. Fe2O3, Benz.,- and BaO, CO2. Sb: See Sb20O. P: See BaO, CO2. As: See MgO, (NH4)20, As20O5;- As205;K: See Fe203, Acetate of. Fe2O3, As20; — 20, As205; -As; Si: See Na20, 2B203. As2O;- BaO, CO,2 - and ArsenionmoNa: See Fe2O,, Acetate of. lybdate of Ammonium. Sr:'See Fe2O3, Acet., — and BaO, CO2. Ba: See BaO, CO2, - and MnO, CO2. Ur: See Fe2O3, Acetate of. Bi: See BisO3, CO2, -and MnO, CO,2 APPENDIX. 7 Cd: See CdO, C02, -and MnO, CO2. POTASSIUM: Separation of from Ca: See CaO, C02, - and MnO, CO2. Al: See A1203, Acetate of. Cr: See BaO, C02. Sb: See Hg20, Sb20O. Cu: See CuO, CO2, —and MnO, CO2. As: See MgO, (NH4)20, As20,; - Hg20, Fe: See Fe2O3, Acet.;- Fe20A, As20- As2O5; _ As2O5; -Fe2O, As2O,; - Fe2O3, Benz.; - BaO, CO2, - and Ur2O,, As205, - and Arseniomolybdate MnO, CO2. of Ammonium. Pb: See PbO, CO2, - and MnO, C02. Ba: See BaO, C0O2,-and MgO, CO2. Mg: See MgO, C02,-and MnO, C02. B: See MgO, B203. P: See MnO, CO2. Ca: See BaO, CO2; - CaO, CO2, - and Sr: See MnO, CO2. MgO, CO.2 Zn: See MnO, CO02 C: See CO2;- K2O, C02, and C, pp. 69, MERCURY: Separation of from 79, 80. H: See B203. Sb: See' Sb20O. Fe: See Fe203, Acetate of. As: See As;- As203, - and Arseniomolyb- Mg: See MgO, (NH4)20, As20; -BaO date of Ammonium. CO; — MgO, CO2,-and [MgO, CO; Bi: See Bi203, CO. (NH)20, C021. Pb: See PbO, C02. Si: See CaO, CO2, - and BaO, CO2. NICKEL: Separation of from [See also Alkalimetry, for the estimation of potassium, and the separation of KHO from Al: See AlsO, Acet.; - NaO, Alo3;K20, COs. BaO, CO0, - and NiO, CO. Sb: See Sb20; — Sb203,- and Sb. SILICON ~ Separation of from As: See MgO, (NH4)20, As20D; - Hg2O, Br See AgBr As2O0;- FeO03, As20e; - As; — As203; 2Fe: See;NaO, 2B O. - BaO, CO2, - and Arseniomolybdate: See 2 of Ammonium. Li: See CaO, CO, -and BaO, CO2. Ba: See BaO, CO2,-and NiO, CO2. See CaO, C02, and BaO, CO Ca: See OaO, 0-and O, 2. Na: See CaO, CO0, - and BaO, COs. CC 2: See 002,CO2,-and NiO, C~@ [For the decomposition of refractory sil`C: See CB 02 0 cates see B203;-Na2O, B203; -BaO, 002; Cr: See BaO, CO. -aad Co: See [CaO, CQ2; CoO, CO20. Fe: See Fe23, Acet.; - Fe20, As2s; — SILVER: Separation of from FeA0, sen.z-, - and BaO, C~02- Sb: See Sb205; — Sb203, - and Sb. Sr: See NiO, CO2. As: See As; - As2O3, - and ArseniomolybNITROGEN: Separation of from date of Ammonium. C: See C, pp. 63, 68, 71, 73. Bi: See Bi2O, CO2 [For a method of estimating nitric acid, see Pb: See PbO, C02. As2O8]. SODIUM: Separation of from PHOSPHORUS (and Phosphoric Al: See' Al20, Acetate of. Acid ): Separation of from Sb: See Hg2O, Sb205. Al: See BaO, CO2. As: See MgO, (NH4)2O, As2Os; - Igs20, Ba: See BaO, CO2,- and Ag2O, CO0. As2O5; - As2O5; - Fe203, As2;05Br: See AgBr. Sn2, As205; - Ur03, As20, - and ArCa: See BaO, CO, - and Ag20, CO. seniomnolybdate of Ammonium. Fe: See BaO, CO2. Ba: See BaO, CO2. Mn: See MnO, C02. B: See MgO, B203. K: See Ag2O, CO. Ca: See CaO, C02. Na: See Ag2O, CO. C: See C, pp. 69, 79, 80. Sr: See BaO, CO02 - and Ag2O, CO2. H: See B203. 8 APPENDIX. Fe: See Fe2O3, Acetate of. IBr: See AgBr. Mg: See MgO, (NHI)20, As2Os, - and C: See Ag20, CO2; and C, pp. 64, 71, 73, 74. [Mg6, C02; (NH4)20, C0O2. Si: See CaO, C02,-and Ba~, CO2. TIN: Separation of from Sn: See SnO2, AsO2. Sb.: See Na20, Sb20, - and Sb. [See also Alkalinetry, for the estimation of As: See SnO2, As20O, - and As. sodium and the separation of NaHO from Na: See SnO2, As20. NaO, C02]. URANIUM: Separation of from STRONTIUM: Separation of from Al: See Al203, Acetate of. Al: See A1203, Acetate of. As: See MgO, (NH4)20, As205. As: See Hg20, As20; - Fe2O3, AsO,2; - Fe: See A1203, Acetate of. K20, As205; - Ir203, AsO5;- As; — WATER: See Hydrogen, above. As203;- BaO, CO2, - and Arseniomolybdate of Ammonium, ZINC: Separation of from lybdate of Ammoniumn, EBa: See CO2. Al: See A1203, Acet., and BaO, CO2. Ca: See CO2, - and CaO, CO2. Sb: See Sb205. C: See C02, - and C, pp. 69, 79, 80. As: See MgO, (NH4)20, As2O; - Hg2O, Co: See CoO, CO2. As205; - As05; - FeO3, As2O;-:I: See 1320. K20, As2O5; - Ur2, AsO5;-As;Fe: See Fe2O3, Acet., -and BaO,CO. As2O3; BaO, C02, - and Arseniomo Mn: MnO, CO2. lybdate of Ammonium. Nii: See NiO, CO2. Ba: See BaO, CO2; P: See BaO, CO. Ca: See CaO, CO2. C: See CO2. SULPHUR: Separation of from Cr: See BaO, CO2. Sb: See Sb203~ Fe: See Fe2O3, Acet., -FeO3, Benz.,-ani As: See As2O3i BaO, CO2. Bi: See Bi. Mn: See MnO, CO2. This signature is not to be bound in the completed volume. FINDING LISTS, [RELATING TO PART II.] FOR METHODS OF SEPARATING ELEMENTS. ALUMINUM: Separation of from K: See SbCl3. Ba: See Na2O, CO2. Ag: See SbC1l; - AgC1. Ca: See Na2O, CO2. Na: See SbCI3. Cr: See BaO, CrO3. Sr: See SbC13. Cu: See Cu. Zn: See ZnC12. Fe: See FeCI2. [For the estimation of Sb203 see further Mg: See Na2O, CO2. K20, 2CrO3.] Mn: See Na2O, CO2;- C1. ARSENIC: Separation of from Hg: See fHgCI. Ba: See AsCl3. K: See 2KC1, PtC14. Ca: See AsC13;- CaCI2. Ag: See A C: See AgC1. Sr: See Na20, CO2. Cr: See Cr. Znl: See ZnO, CO2. Co: See AsC]3; — CoC12. AMMONIUM: Separation of from Cu: See AsC13 — CuCI,2 Ba: See 2NH4CI, PtCI4. Au: See AsCI3. CaM: See 2NH4C1, PtCI4. Pb: See AsCI3; - PbCI2. Cr: See CrO2. Ni: See AsC13 - NiC12. Li: See 2NH4C1, PtCI4. Pt: See AsC13. Mg: See 2NH4CI, PtCI4. K: See AsCI,; - 2KC1, PtCI14. Ag: See AgCI. Ag: See AsC13; - AgC1. Na: See 2N14C1, PtCI4. Na: See AsC13. Sr: See 2NH4C1, PtC14. Sr: See AsC13. [For the estimation of NH3, see further Zn: See ZnC12. NH4C1 and 2ENI4C1, PtCI4.] [For the estimation of arsenic see further Cra 4;- K, 2CrO..] ANTIMONY: Separation of from Cr03; 20, Ba: See SbCl3. BARIUM: Separation of from Ca: See SbCls;- CaCI2. Al: See Na20, CO2. Cr: See CrO,. NH4: See 2NH4C1, PtCI4. Co: See SbC15; - CoC12. Sb: See SbC13. Cu: See SbCls; - CuC12. As: See AsC13. Au: See SbCl1. Bi: See BiCI3 (basic). Pb: See SbC1r; — PbC12. C1: See HC1. Ni: See SbCl,;- NiC12. Cr: See CrO3; - (NH4)20, CrO3;- BaO, Pt: See SbC1x. CrO,; — Na20, CrO3. 2 APPENDIX. Co: See CoCl; — Co. Sb: See SbCI; — CaCI9. Cu: See Cu. As: See AsCIX;- CaCl2. Pb: See Ci Ba: See B:.', CrO. Mn: See C1. 2i: See BiCi; (basic); - CaCI2. HIg: See HgC1; - igCl;- NiCI2. C1: See IIC1. K: See 2KCI, PtC14. Cr: See Cr10; - (NH4)20, Cr03; - CaO, Ag: See AgC1. CrO3; - PbO, CrO; - Hg20, CrO3;Sr: See BaO, CrO,. Na20, Cr03. Zn: See ZnO, CO2. Co: See CoC12; — Co. Cu: See Cu. BISMUTH: Separation of from Pb: See C1. Ba: See B;C1s (basic). Ig: See CaC2;- MgCI2. Cl: See MiCI3 (basic); Bi203, 2CrO3. Mn: See Cl. Ca: See BiCl, (basic);- CaCI2. Hg: See CaCl,; - HgC1. Cr: See CrOs. Ni: See NiCI. Co: See BiCI, (basic);-CoC1 K: See 2KC1, PtC. Ag: See CC1. Cu: See BiCl atnd BiC13 (basic); — CuC2; Ag: See AgC1. - Cu. Sn: See CaC12. Pb: See BiCI,; — PbCI9. IZn: See ZnO, CO2. MItJn: See BiCLo (basic). nHg: See BiCl3 (basi(). CCARBON: Separation of from Hg: See BiCl3 (basic). Ni: See BiCI3 (basic);-NiC2. Cl: See CaC12;- CuC12; - PbC12; - KC1; Pt: See 2NH4 C1, PtCI4;- 2KC1, PtC14. - ZnC12. K: See BiCI, (basic). H: See CaC2; — 2KC1, PtC14. Ag: See BiCI3; - AoC1. Fe: See FeCl3. Na: See BiCI3 (basic).:N: See 2KC1, PtCI4. Sr: See BiCl3 (basic). K: See KC1. Zn: See BiC13 (basic).!Nea: See Na2O, C02; -- NaC. Sr: See SlO, CO2. BORON: Separation of from S: See CuO, CrO3. C1: See AgC1. [For the oxidation of carbon see Chlorates; K: See 2KC1, PtCI4. — CuO, Cr03; — PbO, CrO3.] [For the separation of B203 see further [For the estimation of C see further 2KC1, HC1.] PtC14; - CrO3; of CO2 see further ZnO, COs.] BROMINE: Separation of from 2: See AgCl; NaC;. CHLORINE: Separation of from C1: See AgC1; — NaC1; - C1. I: See C1. As: See AgCl. [For the estimation of bromine see further Ba: See HC1. SnC12;- C1.] Bo: See AgCl.' 1Br: See AC1;- NaCl;- C1. CADMIUM: Separation of from Ca: See HCI. Bi: See BiC13 (basic);- Bi203, 2Cr03. C: See CaCl2; - CuC12 -PbC12 - ZnCl2. Cr: See CrO3. C1: See AgC1:; — C1. Cu: See Cu. Cr: See AgCl. Hg: See HgC1. i H: See CuC12. Pt: See 2NHIIC1, PtC14;-' KCl, PtC14. I: See NaC1; — C1. Ag: See AgCI. Pb: See PbCI2. *Mg: See HC1; — HgCL2. CALCIUM: Separation of from Hg: See HgC Hg: See HgC1s. A1: See Na20, CO2. N: See AgC1. NH4: See 2NH4C1, PtCl4. P: See AgC1. APPENDIX. S Pt: See HCI; - NaiCl. COBALT: Separation of from K: See HCI; - KC1. Sb: See SbCI3; -CoCI2. Ag: See AgC1. As: See. AsC1; —CoC12. Si: See AgC1. Ba: See CoCl,; - Co. Na: See HC1; — NaC1. Bi: See BCI, (basic); —CoC12. Sr: See HC1. -Ca: See CoC2; — Co. S: See AgCl. Cr: See CrO3; —BaO, Cr03;-Na2O, CrO3. [For the estimation of chlorine see further Cu: See Cu. Chlorates; -NH4C1; - CuC12; - ItgCl; - Mn: See CoC12; - MlnC12; -- Co; - K20, KC1;- AgC1; — SnCI2.] col)alticvani(le. CHROMIUM: Separation of from Hg: See CoC12. Al: See BaO, Cr03O Ni: See Cl; - CuO, cobalticyanidle;-Hg.), NH,: See Cr0,3:. cobalticya:nide; - K,0. cobalticyalnide. Sb: See CrC0. Pt: See 2NHI4C1, PtCI, - 2KIC1, PtCl4. ee. K: See 2KC1, PtCI4; - CO, cobalticyatide; Ba: See CrO; —(NL4).20, CrO; - BaO, lt2cvaulii CrO:3; — NaO, CrO0. Ag: See AgCI. B ~i: See Cr3~. 8 ~Sr: See SrO, C02; — CoCI; — Co. Cd: See Cr. n: See CoC2; - SIC14. Ca: See CrO,3; -(N-I)O, Cro; - CaO, Zn: See ZnO, cobalticvlaui(le. CrO; -- PbO, CirO; - Hg,20, Cr3; -- [For the estimation of cobalt see further Na20?, Cr03. Cr2CI:; - CoCl2; - SnCI,-.] Cr: See CrO3; - (NH4)20, CrO3; - H-20, COPPER: Separation of from CrO3. Co: See CrO3;- BaO, CrO,;- a2 Al: See Ci. Cr03. Sb: See SbC15; -- CuC1,. Cu: See Cr03; - Cu. As: See AsCl3; - CuCI.. Au: See Cr03. Ba: See Cu.:F: See FeCl2;- BaO, Cr03; -,O, MgBi: See BiCu3 (norinal and basic); — CuC2; -Cu. Cd: See CU. Pb: SeePbCI- Cr0:. Se Cu. Mg: See Cr03;- C(N1H)0, CrO,;- BaO, Ca: See Cu. CrO; — PbO, CrO,; — H!O- 0, CrOs; Cr: See Cr13,;- Cu. -NarO,2 CrO3. ACo: See Cu. Mn: See CrOs; —BaO, CrO; O, CrO. Fe: See Cu. Hg: See CrO0. Pb: See PbCI C1; - Cu. Ni: See CrO; -- BaO, Cr03; — NaO, CrO. g: 2 C; Cu Mg: See Cu. Zi: See CrO:3; - BaO, C"03;- \a.20, Cr03- Mn: See Cu. Pb: See CrO. n Se Cu. K: See KCI; - CrO,; - (N114)0, Cr0 Hg: See CuC2;- gC;-IC. HgFr2 0,, Cr03o. i: See Cu. Ag: See Agl-C1; — CrO,. Pt: See 2iNH4C, PtC14; -- 2KC, PtCI,. Na: See NaCl; - Cr03; - (NH4)20, Cr03; K: See 42I;, PtCl4; - Cu. -- Hg20, Cr03. Ag: See AgCl. Sr: See CrO03; — (NH1)90, Cr03; — PbO, Na: See Cu. CrO,; - gIg20, Cr0,;; - NaO, CrO3; - Sr: See Cu. SrO, Cr03. 8: See NaO, CO9. 8: See CrO;;- PbO, CrOs. Sn: See CuCI2; - SnCl. Sn: See Cr03. Zn: See Cu. Zn.: See CrO3; —B;O, Cr0;; —Na2O, CrO0. [For the estinmation of Cu see further [For the estimation of chromium see further. SnC1,.] CrC3; -l Cr03: of CrO,, see SuClt-.] For the estimation of Ferricyanhydric acid 4 APPENDIX. see SnC12; - of Ferrocyanhydric acid see Cu: See PbC12; — C1;- Cu. Cr0..I: See PbC12. FLOURINE: Separation of from Mg: See C1. Hg~: See PbC12; HgCl;-HgCl,. C1: See AgCl. Ni See C1 n Ni: See C1. GOLD,: Separation of from N: See PbCl2. Sb: See SbC]5. K: See C1. As: See AsC13. Ag: See PbC2; — AgCl. Cr: See CrO0..Na: See C1. Pt: See 2KC1, PtCI4. Sr: See C1. Ag: See AgCl1. Sn: See PbC12; — SnCl4. Sn: See SnCl4. Zn: See C1. HYIDRO~~GEN: Seplaration of from [For the estimation of lead see further PbC12; m SnCI2-. C: See CaCI2; - 2KC1, PtCl4. Cl: See CuC12. LITHIUM: Separation of from K: See'KC1. NH4: See 2NH4C1, PtC14. Na: See NaC1. K: See LiCl;- 2KC1, PtCI4. [For metliods of estimating water see CaCl2; Na: See LiCl. - CoC12; - NaCI.] MAGNESIUM: Separation of from IODINE: Separation of from A1: See Na2O, CO2. Br: See C1. NH4: See 2NH4C1, PtC14. Cl: See AgCI: —NaC1; - C1. Ca: See CaC12;-MgC12. [For the estimation of Iodine see further CI: See IHCI' HgCI2. SnC]2; — Cl; - K90, 2CrO3. Cr: See CrO0; - (NH4)20, CrO0; - BaO, CrO13; — PbO, CrO3; — Hgo0, CrO0;IRON: Separation of from Na2O,CrO. Al: See FeC]2. Cu: See Cu. C: See FeCI3. Pb: See C1. Cr: See FeC2; - BaO, CrO,; — Na.20, Mn: See C1. Cr.03. Hg: See HgC1;- HgCI2. Cu: See Cu. Pt: See 2KC1, PtCI4. Gl: See FeCl2., K: See MgCl,;- HgC,;- AgC1; - 2KC1, Mn: See C1. PtCI4. P: SeePCl3. Ag: See AgCl. Pt: See 2NH4C1, PtCl4; - 2KC1, PtCIl. Na: See MgCl2; — TIgCl2; — AgCl. K: See 2KC1, PtCl4. Sr: See SrO, CO2. Ag: See AgC1. Zn: See ZnO, CO2. S: See Na2O, CO,. MANGANESE: Separation of from [For the estimation of iron see further Al: See Na90, CO 2;- C1. CuCl; - FeC13; - SnC12; - CrO; - K2O, Ba: See C1. 2CrO3.] Bi: See BiC!3 (basic). Ca: See C1. LEAD: Separation of from Ca: SeeCl. Cr: See CrO3; — BaO, CrO3; — Na20, Cr,,. Sb: See SbCl3;- PbC12. Co: See CoC12;- MnC1,2;- Co; —K20, (oAs: See AsClI;- PbCI2. balticvanide. Ba: See Cl. Cu: See Cu. Bi: See BiC1; — PbC2. Fe: See C1. Br: See PbC1l. lMfg: See C1. Ca: See C1. Ni: See MnC1l; - NiC12;- C1. Cl: See PbC12. Pt: See 2N11,C1, PtCl4; — 2KC1, PtCl4. Cr: See PbCI2; - CrO, K: See C1. APPESDIX. 5 Ag: See A(Cl. [For the estimation of nitrous acid se Na: See Cl. CrOa.] Sr: See SrO, C02; -C1. PHOSPHORUS: Separation of from Zn: See ZnO, C09;- C1. [For the valuation of MnO2 see further Cu See AgC. Cu: See Cu. Fe: See PC13. MERCURY: Separation of from K: See 2KC1, PtCI4. A1: See HgCl. Ag: See AgCl. Ba: See HgC1; - HgC12. P205: (estimation) See PbO, CrO3.:Bi: See Bicl, (basic). Cd: See BI —gCI (basi. PLATINUM: Separation of from Cd: See HgCl. Ca: See CaC12; — HgCl. Sb: See SbCIx. C1: See HgCl2. As: See AsCI3. Cr: See PbC12; - CrO3. Bi: See 2NH4C1, PtC14; — 2KC1, PtCI4. Co: See CoCI2. Cd: See 2N'H4CI, PtCI4; — 2KCI, PtC-14. Cu: See CuC2;- HgC1l; — gCI2. C1: See HC1; NaC1. Pb: See PbCl2; — HgCl; - HgCI2. Cr: See CrO,. Mg: See HgC1; — HfgCI2. Co: See 2N14C1, PtC14; - 2KC1. PtCl4. Ni: See NiC12. Cu: See 2NH4C1, PtCI4;-2KC1, PtCI4. Pt: See 2NH4CI, PtC4; - 2KC1, PtCl4. Au: See 2KC1, PtCl4. K: See HgCl; — HgCI2. Fe: See 2NH4C1, PtCl4; — 2KC1, PtC14. Ag: See HgCl2; -AgCI. Mg: See 2KC1, PtCl4. Na: See H-ICl; - -HgCI2. Mn: See 2NH-4C1, PtCl4; - 2KC1, PtCI4. Sr: See Hg C1; - HgC12. Hg: See 2NH4CI, PtC14; - 2C1, PtC14. Zn: See ZnCl2. Ni: See 2NHI14CI, PtCI4; - 2KC1, PtC14. [For the estimation of mercury see further Ag: See AgCl. HgCI; — HgCI2;- SnCI2.] Sn: See SnC14. NIC(KEL: Separation of from Ur:' See 2NH4C1, PtCI4; — 2KCI, PtC14. Zn: See 2NH4C1, PtCl4; — 2KCI, PtCI4. Sb: See SCl3; - -NiCl2. [For the estimation of Pt see further PtCI4;..ks: See AsC1,3; NiCl.. Ba: See AsCI3;-. NiC22Nt14C1, PtC14; — 2C1, PtC14.] Ba: See NiCL. Bi: See BiC1, (basic); — NiCI,. POTASSIUM: Separation of from Ca: See NiCls. Ca: See NiC12. Al: See 2KC1, PtC14. Cr: See Cr03; - BaO, CrO3;- NaO, CrO3. Sb: See ShCl. Co: See C1; —CuO, cobalticyanide;- Hg2, A: Se AC3 KC, PtC As: See AsCI; -- 2KC1, PtC14. cobalticyanide; - K20, cobalticyanide. Ba: See 2KCi, PtCl Cu: See Cu. Pb: See Cl. Bi: See BiCIl (basic). Mn: See MnC12; - NiC2; - C. Bo: See 2KC1, PtCI14. Hg: See NiCl2. Ca: See 2KC1, PtC14. HgbC: See KCl. Pt: See 2NH4C1, PtCI4; - 2KC1, PtCl4. Cl See IC1; KC1. Ka: See 2KC1, PtCI4. C See KC Cr; - )0 Cr0; Ag: See ArCl.C1 -eg, C r03. Sn: See NiCr,; - SnCCI. Co: See 2KCl, PtCI4; - CiG,( cobalticyaSn: See NiCI2; - SnCl2. nide; - r1(), coba-ticyanide. [For the estimation of nickel see further cu C, Scoblticyanide. NiCl2; — SnCl2.] Cu: Se K C1- Cu H: See KCl. NITROGEN: Separation of from Fe: See 2KC1, PtCl. Cl: See AC1. Pb: See Cl. C: See 2LKC1, PtCl4. Li: See LiCL; - 2KC1, PtCl4. APPENDIX. Mg: See MgCI2; — HgCI2; -AgC1; —2KC1, Zn: See AgC1. PtCI4. |SODIUM: Separation of from IMn: See C1. MHg: Seoe 1IC; - HgC. NI- 4: See 2N1I4C1, PtC14..I-g: See HaC1; — HgC12/ Sb: See SbCIP. Ni: See 2KC1, CO -2KC PC: See AsCl se ri ofmM: See ABsC1l3. P1: See A,2), CO2; — 2KC1, PtC14. Si: See C1 Bi: See BiC (basic). Ag: See AgC1. C See 0 C02; - aC. C1: See ItC1;- NaC1. Na: See KCI; - -AgC; - 2KC1, PtC14. [FoSr: Se dcompositin- 2KCof, PtC s- Cr: See NaCl; — CrO,; —(NH1,)20, CrO, 5s: See SrO, C 2;- t]C 1, PtC14. S: See KC1; — 2KC1, PtC14. rZn: See ZnO, C02; —2KC1, PtC14. Cu: S Cu. ~ i: See N;aC1. [For the estimation of K see further KC; H: See aC. Pb: See C1. 21iC1, Pt~l4.] aLi: See Li C1. SILICON: Separation of from Mg: See M-C1;-IgC; - AgC1. Cl': See AgCl. Mn: See C1. K: See K C1. Ig: See ZIgC1;- HgCl2. Na: See NaC1.'' P: See Ag2,1 CO. [For the decomposition of refractory sili-: See; - AC; - Na - cates see Na2O, CO2.] PtCI4. Si: See NaCl. SILVER: Separation of from Ag: See Ag C1. Al: See AgC1. Sr: See SrO, CO2. NH4: See AgrC1. S: See NaCi. S-: See SbCI;- AgC. i Zn: See ZnO, CO. All: Ste Atr~l. 4 Bi: See ZsO, oCr. As: See AsC.; — AgC1. [See further Carbonate of Sodium for the Ba: See AgCl1. estimation of Na.] Bi: See BiCAg, C1. Bi: See BiCl; — AgCl. STRONTIUM: Separation of from Cd: See AgC1. Ca: See AoCl. Al: See Na2O, CO2. CP: See AgC1. I4: See 2NHJIC1, PtC14. Cr: See AgC1; CrO3. Sb: See SbCul. Co: See AgC]. As: See AsCl1. Cu: See AgCl. Ba: See BaO, Cr02. Au: See AgC1. Bi: See BiC1, (basic). Fe: See AfC1. Ca: See C1. Pb: See PbC12 - AgC1. C: See SrO, CO2. Mg: See AgCl. C1: See H C1. Mn:,See Ag-CI. Cr: See CrO,; - (NH4)20, CrO:v; - PbO, Hg: See HC12; — AgC1. CrO;- Hg2O, CrO; — Na20, Cr0; — Ni: See AgC1. SrO, Cr0. P: S-e AgC1. Co: See SrO, CO2; — CoCl2;- Co. Pt: See AgCI. Cu: See Cu. K: See AgCI. Pb: See Cl. Se: See AgC1. M-.g: See SrO, CO2. Na: See AgCI. Mn: See SrO, CO,;- C1. Sr: See AgC1. Hg: See HgC1; H- gC12. S: See AgC1. Ni: See SrO, C02; — NiCI2. Te: See AgCl. K: See SrO, C02; — 2KC, PtCI4. Sn: See AgCI; —SnCl1. Ag: See AgC1., Ur: See AgC1. Ia: See SrO, CO2. APPENDIX. 7 Zn: See SrO, CO2;- ZnO, CO2. [For the estimation of tin see further SnCI,; [For the estimation of Sr see further SrO, - 1K20, 2CrO0.] CO.] ~~2 ~~] ~WATER: Compare Hydrogen. SULPHUR: Separation of from [For methods of estimating wvater see CaCl,; C: See CuO, CrO8. C1: See AgC1. 2 Cr: See CrO,; -PbO, Cr03. ZINC: Separation of from Cu: See Na20, CO2;- Cu.:Fe:* See Na2O, CO,.; Al: See ZnO, CO2. Fle: See NZO, CO2.oSbltSeyZni K: See KC1;- 2KCl PtC14. Sb: See ZnC12. Ag: See AgCl. As: See ZnC12. Na: See NaCL.: See ZnO, CO2. Zn: See ZnC12. Bi: See BiCI3 (basic). Au: See Sn~l4 NCa: See ZnO, C~r [For the separation of S from metals see C: See Z, CO b: SC ee.] Pbol2;-SnCr: See CrO,; —BaO, CrO3;- Na2O, CrO0. [For the estimation of H2SO4 see further Co: See ZnO, cobalticyanide. AgC1; —BaO, CrO; —PbO, CrO,3; —of SO, Cu: See Cu. see SnCl2;-Cl; -of H2S202 see C. P: See C. Mg: See ZnO, CO2. TIN: Separation of from Mn: See ZnO, C02; - C. Ca: See CaCl2. Hg: See ZnC12. Cr: See CrO0, Pt: See 2N1HtC1, PtC14; - 2KC1, PtC1l. Co: See CoCI2; — SnC14. K: See 2KC1, PtC14. Cu: See CuC12; — SnCl4. Ag: See AgC1. Au: See SnCl4. Na: See ZnO, CO2. Pb: See PbC12;- SnC14. Sr: See SrO, C02; — ZnO, CO. Ni: SeqNiC12; - SnCl4. S: See ZnC12. Pt: See SnC14. Sn: See ZnC12' Ag: See AgCl;- SnC14. Va: See ZnO, CO2. Sn: See SnCl2. [For the estimation of Zn see further ZnO, Zn: See ZnCI2. CO.]