BERKELEY STBRARY or CALIFORNIA EPITOME OF CHEMISTRY, IN THREE PARTS. PART I. Intended to facilitate, to the Student, the Acqui- sition of Chemical Knowledge, by minute In- structions for the Performance of Experiments. PART II. Directions for the Analysis of Mineral Waters ; cf Earths and Stones j of Ores of Metals ; and of Mineral Bodies in general. And PART III. Instructions for applying -Chemical Tests and Re- agents to various useful Purposes. BY WILLIAM HENRY. THE SECOND EDITION, CORRECTED. LONDON: Printed for J. Johnson, No. 72, St. Paul's Church-yard, By J. Crowder, Warwick Square, PREFACE., THE small volume, which I now offer* to the public, is one of humble pre* tensions : yet its plan and objects appear to me sufficiently distinct, from those of every other compendium of chemistry, to authorize the addition of one more to the extensive Hit of elementary works. The " Chemical Pocket Book" of Mr. Parkinson, and the " Description of a Portable Cheft of ChemVrv," translated from the German of Gottlinjr, and pub- lished in the year 1791, might, perhaps, from the similarities of title and size, be supposed to have precluded the ne- cessity of this publication. A very cur- sory comparison, however, of Mr. Par- kinson's work, with this manual, will evince that the plan and objects of the IV two books are totally different. To the work of Mr. Gottling, the present bears, indeed, a nearer Resemblance , but the coincidence is not such, as k> supersede the utility of this epitome. The enume- ration of tests for minefal waters ; the in- structions for applying these reagents ; and the rules for detecting adulterations, are subjects common to both. But the progress of chemical knowledge, during the last ten years, has been so rapid, as to enable me to make numerous additions to the information of Mr. Gottling ; and to induce me materially to vary the ar- rangement, under which it was offered. It may be added, that the ancient > nomenclature of chemistry, employed throughout Mr. Gottling's work, inuft render it nearly unintelligible to students of the reformed system. The arranged series of experiments was suggested to me as proper for r publication, by a written catalogue, which I drew up, more than two years ago, of the experiments performed dur- ing my course of chemical lectures. This I deem it necessary to state; be- cause something similar is tx> be found in an excellent manual, lately published by Bouillon la Grange. Another object, which I propose to be fulfilled by this epitome, is, that it may serve as a companion to the collec- tions of chemical substances, which I have been induced, by the repeated applications of students of this science, to fit up for public sale*. The utility of these collections has, hitherto, been limited, by the want of a concise but comprehensive code of instructions for their use. With the concurrent aid of the first part of this work, and of a corresponding chest of chemical re-.- gents, * See the advertisement at the end of the work, 4 VI the labours of the student cannot fail to be much facilitated: for one of the prin- cipal difficulties in studying the science of chemistry, experimentally, is the acqui- sition of a great variety of substances, many of which are not easy of attain- ment. The directions for analyzing waters, and mineral bodies in general, I shall enable any one to apply prac- tically, by corresponding collections of chemical tests, of so small a bulk, as to add, in the least possible degree, to the 'incumbrances of the traveller. In a work, professedly compiled from others, new and original information is not to be expected $ and it cannot be ne- cessary to quote all the authorities for fat:ts. If there be any one author, to whom I owe most, it is certainly to Mr. Kirwan, whose interesting and masterly Works comprehend almost every subject of chemical enquiry. The directions for VJl analyzing minerals are translated, with considerable additions and alterations, from Vauquelin's paper, in the 30th vo- lume of the Annales de Chimie. I have now only to intreat the candid indulgence of the reader towards the errors and omissions which will doubt- less be found in this work ; and in apo- logy for which, I have to allege, that on undertaking the publication, I had a prospect of considerably more leisure, than fell to my lot in the prosecution of it. This apology, I am under the ne- cessity of prefixing, also, to a second edition ; the rapid sale of the first having allowed me no time for material altera- tions, and having limited me to a few verbal corrections. Manchester^ June 26, 1801. CONTENTS. PART /. Page SECT. I. x\ DVICE tq Persons who are entering on the Study of Chemistry I SECT. II. An arranged Series of Experiments, to be performed by the Student of Chemistry 3 Art. I Chemical Affinity Solution &c 3 Art. II. Properties and Effects of Caloric 7 Caloric of Temperature Uncombined Caloric , zb. Combinations of Caloric 10 Fluidity.. ib. Vapour la Art. III. Gasses in General 13 Art IV. Oxygenous Gas 18 Art. V. Azotic or Nitrogen Gas 21 Art VI. Atmospheric Air ib. Art. VIL Hydrogenous Gas 23 Art. VIII. Composition and Decomposition of Water 27 Synthetic Experiments 28 Analytic Experiments ..*. 29 Art. IX. Properties -and Effects of Water 34 Art. X. Alcalts General Qualities ..... 38 Pure Potash and Pure Soda ib. Pure Ammonia or Ammoniacal Gas ... 39 Art, XT Acids in General 40 Art. XII. Carbon Carbonic Acid and their Compounds 41 . Carbon ib. Carbonic Acid , 42 Car onates-^-Carbonate of Potash ... 46 Carbonate of' Soda , 50 Carbonate of Ammonia .,,, 51 Carbonated Hydrogen Gas ib, Art, XIII. Sulphur Sulphuric Acid and their Compounds 52 Sulphur ib. Sulphuric Acid ., 53 Sulphureous Acid Gas $6 Sulphate of Potash ib. Sulphate of Soda 57 Sulphate of Ammonia .. 58 Siilphurets of Potaj^b and Soda ...... ib. Sulphurated H\ drogenGas 60 Art XIV. Azote or Nitrogen 'Nitric Acid and their Compounds 61 Nitric cid ib. Nn^'iis Gas 61 N't ions Qxyd (Gaseous Oxyd Oi Azote) , 65 Nitrate of Potash .,,,,,,,*,,,,. 6& Nitrate of Ammonia 70 Art, XIV*. Muriatic Acid and its Compounds ... ib. Muriatic Acid ib. Iv uriate of Potash 71 Muriate of Soda ib. Muriate of Ammonia 72 Oxygenated Muriatic Acid ib. Oxygenated Muriate of Potash . 74 Soda 76 Decomposition of Ammonia by Oxy- genated Muriatic Acid ib. Kitro-Muriatic Acid 77 Art. XV. Phosphorus - Phosphoric Acid- and their Compounds Phosphorus Phosphoric Acid 79 Phosphorated Hydrogen Gas 80 Art. XVI. Porac c cid, and its Compounds 81 Art. XVII. "Earths .. 82 Lime, and its r om onnds ib. Magnesia, and its Compounds ... 88 Alumine, and its Compounds ... 89 Silex 91 Barytes 92 Strontites 94. Art. XVIII. Metals in general 95 Art. XIX. Gold 97 Art. XX. Piatina 99 Art. XXI. Silver , ib. Art, XXII, Mercury MMMfMM.*M. **....,, 101 XI I Page ArtXXlil. Iron 103 Art. XXIV. Copper 107 Art. XXV. Lead 108 Art. XXVI. Tin , 109 Art. XXVII. Zinc no Art XXVIII. Bismuth ib Art. XXIX. Arsenic in Art. XXX. Antimony 112 Art. XXXI. Manganese 113 Art. XXXII. Cobalt 114 Art. XXXIII. Nickel 115 Art XXXIV. Vegetable Substances 116 Art. XXXV. Animal Substances 127 xia PAR T II. DIRECTIONS ?OR EXAMINING MINERAL WATERS, BODIES IN GENERAL. Page SECT. I. Examination of Mineral Waters 131 Tests enumerated ............ 132 143 Infusion of Litmus Syrup of Violets, &c ................... 133 Tests of Alcalis ........... . ......... 134 Tincture of Galls .... .......... .... ib. Sulphuric Acid . .................... 135 Nitric and Nitrous Acids ...... ib. Oxalic Acid and Oxalates ...... 136 Pure and carbonated Alkalis ... 137 Lime Water ........................ 138 Solution of Pure Barytes ......... ih. Metals ............ . ................. 139 Sulphate of Iron .................. ib. Sulphate and other Salts of Silver 140 Nitrate and Acetite of Lead ... 141 Nitrate of Mercury ............... ib. Nitrate, &c. of Barytes ......... 142 Prussiates of Potash and of Lime ib. Solution of Soap in Alcohol ...... 143 Alcohol .............................. ib. Sulphuret of Ammonia .. ...... . a*. b xiv Page Table of Substances that may be expected in Mineral Waters $ and the Means of detecting them . 144 Analysis of Waters by Evaporation 146 SECT. II. Analysis of Minerals 149 Method of examining an unknown Mineral 151 Analysis of Salts .... 153 of Earths and Stones ... 156 of Inflammable Fossils... 168 of Ores of Metals 169 in the moist Way 1 70 in the dry Way . 175 PART HI. APFLICAT10K OF CHEMICAL TESTS AND REAGENTS TO VARIOUS USEFUL PURPOSES. Page SECT. I. Method of detecting Poisons ., , 178 of detecting Arsenic 179 Corrosive Sublimate 181 Lead and Copper ... j8j SECT. II. Rules for ascertaining the Purity of Chemical Preparations, intended for the Purposes of Medicine, and for other Uses .^.n^.-.f.*^-..^. 184 XV Page SECT. III. Use of Chemical Reagents to Ar- tists and Manufacturers 204 SECT. IV. Application of Chemical Tests to the Uses of the Farmer and Country Gentleman 208 Analysis of Lime and Lime Stones 209 of Marls *. 212 cfSoils 213 SECT. V. Miscellaneous Uses of Chemical Reagents ....... 220 ERRATA. Page 143, line 9 from the bottom, for SULPHURATE read SULVHURET. 216, 8 from the bottom, dele the sign o r plus at the end. A CONCISE EPITOME OF CHEMISTRY. PART I. SECTION I. ADVICE TO PERSONS WHO ARE ENTERING ON THE STUDY OF CHEMISTRY. 1 HE few suggestions, which I am about to offer, are addressed peculiarly to those, who have not the opportunity of attending chemical lectures j and who have no means of acquiring a knowledge of chemistry, except from books, and from the evidence of experiments. The principal difficulty, experienced by all, who embark in a scientific pursuit, unaided by the advice of an intsructor, is the attainment of the best adapted books. In Chemistry, fortunately, this difficulty is limited to selection only : For we have, in the English language, many elementary works both original and translated, of great merit. I shall, at present, however, confine myself to the mention of very few ; of such only, as are sufficient to convey, to a person of tolerable understanding and competent education, a general acquaintance with chemical science; and I shall afterward sub- join a list of other books, necessary to those, who intend to pursue the study more extensively. Of all the introductory treatises on Chemistry, that of Mr. Lavoisier is certainly the one, from which a person, entering, for the first time, on this study, will derive most pleasure and advantage. The first part of this work, comprehending the more general doctrines of Chemistry, should be perused with attention, and clearly understood, before the reader proceeds any further. It may, even, be necessary, that, previously to the remainder of this \vork, he should study other elementary books, such as those of Chaptal, Fourcroy, and Nicholson. These works will supply the deficiencies of Lavoi- sier's Elements, especially on the subject of chemi- cal affinity, the divisions and laws pf which are essential to be known, as the ground-work of all chemical, explanations. After having made himself mastet of the more general truths of Che- mistry, as delivered in the first part of Lavoisier's and in the first volume of Chaptal's Elements, and also of the principles of the new nomenclature, the student will be qualified to reap advantage from the performance of experiments. In repeating these, lie may either follow the order which I shall pre- sently point out; or he may assume, as the basis of his arrangement, the general propositions laid down by Chaptal or Fourcroy ; referring to the following section, for more minute and .specific directions. In the conducting of experiments, I would recommend great attention to neatness and to order. Let every jar or vial have a label fixed to it, denot- ing the substances it may contain, (except in cases, where the nature of the contents is evident .from mere inspection) and the date and object of the experiment. I would caution the student, not to engage in many different experiments at once 5 the consequences of which are, that the attention is distracted, and that many interesting changes pass unnoticed. It will contribute to form a habit of accurate observation, if the appearances, that occur in experiments, be regularly and distinctly noted down 5 and such an exercise will tend, also, to facilitate the acquirement of the art of describing chemical phenomena, to do which, with selection and precision, is far from being an universal talent. In advising an attention to neatness, however, I am far from recommending a frivolous regard to show, or even too scrupulous a nicety about the appearance of apparatus. With the aid merely of Florence flasks, of common vials, and of wine glasses, some of the most interesting and useful experiments may be made; and in converting these vessels to the purpose of apparatus, a considerable saving of expense will accrue to the experimentalist. SECTION II. AN ARRANGED SERIES OF EXPERIMENTS, WHICH SHOULD, EITHER WHOLLY OR IN PART, BE PERFORMED BY THE STUDENT OF CHEMISTRY. IN the selection of these experiments, I shall generally choose such as may be undertaken by persons not possessed of an extensive chemical apparatus. On some occasions, however, it may ; be necessary, in order to complete the series, that others should be included, requiring, for their per- formance, instruments of considerable nicety. The same experiment may, perhaps, in a few instances, be repeatedly introduced, in illustration of different principles; but this repetition will be avoided as much as possible. Each experiment will be pre- ceded by a brief enunciation of the general truth, which it is intended to illustrate. ART. I. CHEMICAL AFFINITY, SOLUTION, &"C. For these experiments, a few wine glasses, or in preference deep ale glasses, will be required, and a Florence flask for performing the solutions. I. Some bodies have ?io affinity Jor each other. Oil and water, or mercury and water, when fhaken together, do not combine, the oil or water always rising to the surface, and the mercury sinking to the bottom. ?, Examples of Solution. Sugar or common salt in watery chalk in dilute muriatic acid*. 3. Influence of mechanical division in promoting the action of chemical affinity % or in favouring solu- tion. Lumps of chalk or marble dissolve much more slowly in dilate muriatic acid, than equal weights of the same bodies in powder. In the common arts of life, the rasping or grinding of wood, and other substances, are familiar examples. 4. Hut liquids are more powerful solvents than cold ones. To four ounce measures of water, at the temperature of the atmosphere, add three ounces of sulphate of soda in powder. Only part of the salt will be dissolved, even after being agitated some time. Apply heat ; and the whole of the salt will disappear. When the liquor cools, a portion of salt will separate again in a regular form. This last appearance a fiords an instance of crystaflizatio/t. $. A very minute division of bodies is effected by solution. Dissolve two grains of sulphate of iron in a quart of water, and add a few drops of this solution to a wine glaes full of water, into which a few drops of tincture of galls have been fallen. The dilute infusion of galls will speedily assume a purplish hue. This shows that every drop of the quart of water, in which the fulphate of iron was dissolved, contains a notable portion of the salt. 6. Seme bodies dissolve much more readily and copiously than ethers. Thus an ounce measure of distilled water will dissolve one third its weight of * I omit, purposely, the distinction between folution and dissolution. 5 sulphate of soda $ one sixteentli of sulphate of potash -, and only one five hundredth its weight of sulphate of lime. 7. Mechanical agitation facilitates solution. Into a wine glass full of water, tinged blue with the infusion of litmus, let fall a small lump of solid tartarous acid. The acid, if left attest, even during some hours, will only change to red that portion of the infusion, which is in immediate contact with it. Stir the liquor, and the whole will immediately become red. 8. Bodies do not act on each of her, unless either one or both be in a state of solution. A. Mix some dry acid of tartar with dry carbonate of potash. No combination will ensue till water is added, which, acting the part of a solvent, promotes the union of the acid and alcali, as appears from the violent effervescence. B. Spread thinly on a piece of tinfoil, three or four inches square, some dry nitrate of copper*, and wrap it up. No effect will follow Unfold the tinfoil, and having sprinkled the nitrate of copper, with very little water, wrap it up again as quickly as possible, pressing down the edges closely. Con- siderable heat attended with fumes will now be excited : and if the experiment has been dexte- rously managed, even light will be evolved. This shows that nitrate of copper has no action on tin, till in a state of solution. 9. Tti'O bodies, having no affinity for each oilier, unite by the intervention of a third. Thus, the oil and water, which, in expl. 1st, could not, by agitation, be brought into union, unite intimately * To prepare nitrate of copper, dissolve the filings or turnings of that metal, in a mixture of one part nitrous acid, and three parts water; decant the liquor, when it has ceased to emit fumes; and evaporate it to dryness in a copper or earthen 'di^u. Thy dry mass must be kept in a bottle. on adding a little solution of caustic potash. The alcali, in this case, acts as an intermedium. 10. Saturation illustrated. Water, after having taken up as much common salt as it can dissolve, is said to be saturated with salt. Muriatic acid, when it has ceased to a<5t any longer on lime, is said to be saturated. 11. The properties, cliaracterizing bodies when separate, are destroyed, by chemical combination. Thus muriatic acid and lime, which, in a separate state, have each a most corrosive taste, lose this entirely, when mutually saturated ; the compound is extremely soluble, though lime itself is very difficult of solution ; the acid no longer reddens syrup of violets 5 nor does the lime change it, as before, to green. 12. Simple elect lie affinity illustrated, (A) Add to the combination of oil with alcali, formed in expt. 9th. a little dilute sulphuric acid. The acid will seize the alcali, and set the oil at liberty, which will rise to the top. In this instance, the affinity of alcali for acid is greater than that of alcali for oi 1 . (H) To a dilute solution of muriate of lime, (prepared in expt. 2(1) add a little of the solution of pure potash. The potash will feize the muriatic acid, and the lime will fall down, or be precipitated. 13. Double elective affinity exemplified. In a watery solution of sulphate of zinc, immerse a thin sheet of lead. The lead will remain unaltered, as will, also, the sulphate of zinc ; because zinc attracts sulphuric acid more strongly than lead. But let acetite of lead be mixed with sulphate of zinc. The lead will then go over to the sulphuric acid, while the zinc passes to the acetous. '! he sulphate of Jead, being inlbluble, will fall down in the state of a white powder ; but the acetite of zinc will remain in solution. The changes, that occur in this experiment, will be better understood irpm ihs following scheme. Ace-lite of Zinc. Sulphate { Zinc and Acetous acid 1 of Zinc < > consisting of (. Sulphc. acid and Lead. ^ Acetous acid ) Acctite of Lead. Sulphate of Lead. For an explanation of these diagrams, which the student will find it highly useful to underftand,! refer to Bergman's Treatise on Elective Attractions. AKT. II. PROPERTIES AND EFFECTS OF THE MATTER OF HEAT, OR CALORIC*. Effects of Caloric of Temperature, or uncom. bincd Caloric. I . Caloric expands all bodies. (A) The expansion of liquids is shown by that of the mercury of a thermometer. (B) That of aeriform bodies, by holding, near the fire, a bladder partly filled with air, the neck of which is closely tied, so as to pre- vent the enclosed air from escaping. The bladder will soon be fully distended, and may even be burst by continuing and increasing the heat. (C) The expansion of solids is shown, by heating a rod of iron, of such a length as to be included, when cold, between two points, and the diameter of which is such, as to allow it to pass through an iron ring. V> hen heated, it will have become sensibly * I onr.it giving a connected series of experiments on Light, becaute the efiects, produced by this agent, are, generally speaking, more complicated than those of Caloric. Thus, fur example, the action of light frequently depends on its property of deoxidating bodies ; and fads ot this kind cannot be understood, without an acquaintance with the class of metallic oxyds. In the progress of this section, however, many instances will be given of the chemical efficiency of Light. 8 longer ; and will be found incapable of passing through the ring. All the above bodies return again, on cooling, to their former dimensions. 2. Construction of the thermometer founded on tlie principle of expansion. For an excellent account of the method of constructing thermometers, which }s too long to be inserted in this place, see N icholfon's Principles of Chemistry, book ist, chapter 3d. 3. Equal increments or decrements of heat produce equal increments or decrements of expansion in the mer- cury of the thermometer. Mix a pound of water, at 172, with a pound at 32. Half the excess of the uncombined Caloric, in the hot water, will pass to the colder portion j that is, the hot water will be cooled 70, and the cold will receive 70 of temperature 5 therefore, 172 70, or 324-70, rrio2-, will give the heat of the mixture. To attain the arithmetical mean, exactly, feveral pre- cautions, however, must be observed. (See Craw- ford on Animal Heat, p. 95, &c.) 4. Uncombined caloric has a tendency to an equi- librium. Any number of different bodies, at various temperatures, if placed under similar circumstances of exposure, all acquire a common temperature. Thus, if in an atmosphere at 60, we place iron filings heated to redness ; boiling water j and various other bodies of different temperatures, they will soon affect the thermometer in the same degree. c. Pciccr inherent in bodies of conducting Caloric; and llie lonaucting power various in different bodies . (A) Solid bodies convey heat in all directions, upwards, downwards, and laterally ; as may be shown by heating one end of an iron rod, and hold- ing it in different directions. (B) Some bodies conduct caloric much more quickly than others. Coat two rods, of equal length and thick- ness, the one of glass, the other of iron, with wax, at one end of each only ; and then apply heat to the uncoated ends. The wax will be melted much sooner from the end of the iron rod, than from the glass one j which shows, that iron conducts heat more quickly than glass. C. Liquid and aeriform bodies convey heat on a different principle, from that, observed in solids, viz, by an actual change in the situation of their particles. Take a glass tube eight or ten inches long, and about an inch in diameter. Pour into the bottom part, for about the depth of an inch, a little water tinged with litmus, and then fill up the tube with common water, pouring on the latter extremely gently, so as to keep the two strata quite distinct. When the tube is heat- ed at the bottom, the cold infusion will ascend, and will tin^e the whole mass. But if the upper part of the tube be heated, the coloured liquor will remain at the bottom. Other experiments, illustrating the same principle, may be found in Count Rumford's Essays, especially in Essay jth. Thus a cake of ice will remain unmelted, during several hours, when confined at the bottom of a jar of hot water, which, if fixed at the surface, would be liquified in a few minutes; and water may even be kept boil- ing, a considerable time, in a glass tube, over ice, without melting it. J. 77; e boiling point differs in various liquors. Thus Ether boils at 104, Alcohol at 182, and water at 212. It varies, also, in the same liquor, under different degrees of atmospheric pressure. Thus water will boil, under the exhausted receiver of an air pump, at i8o,or even much less, of Faht. Hence the particles of Caloric are mutually repul- sive, and they communicate this repulsive tendency to other bodies in which Caloric is contained. This repulsive power tends to change solids into fluids, and liquids into aeriform bodies, and is chiefly 10 counteracted by the pressure of the atmosphere. See some beautiful experiments illustrating this po- sition in Lavoisier's Elements, chnp. i. On the contrary, by considerably increasing the pressure, water may be heated to above 400*, with- out being'changed into vapour. 6. Uncomlnncd Caloric promotes the action ofcJiemical affinity. Thus lead and tin do not combine, till melted together. In other instances, Caloric ferves as the /mean cf separating bodies already united. Thus lead and sulphur are disunited, by exposure in a high temperature. In favouring the operation of affinity, Caloric seems to act as a solvent ; and in decomposing bodies, its effects are perhaps explica- ble on the principle of elective affinity. Thus, in the foregoing example, sulphur, in a high tempera- ture, or when surrounded by a great quantity of un combined caloric, is more powerfully attracted by caloric than by lead. COMBINATIONS OF CALORIC THE CAUSE OF FLUIDITY. 7. 77/6' se?isible heat, or temperature, of ice, not changed by liquefaction. A thermometer in pounded ice stands at 32, and at the very fame point in the water, which results from the liquefaction of ice. 8. Yctf the ice, during liquefaction, must absorb much caloric. Expose a pound of water at 32, nnd a pound of ice at 32, in a room, the temperature of which is above the freezing point, and uniformly the same during the experiment. The water will arrive at the temperature of the room, several hours before the ice is melted. Yet the ice must, during the whole of this time, be receiving caloric, because, according to expt. 4, a hotter body can never be in * To effect this, a strong iron vessel, called a Digester, is necessary. 11 contact with a colder one, without imparting heat to the latter. The Caloric therefore, which has entered the ice, but is not to be found in it by the thermometer, must be chemically combined ; just as muriatic acid, by union with lirne, loses all its characteristic properties. 9, The quantity of un combined, caloric, that enters into a pound of ice, and becomes united, during lique- faction, may be learned by experiment. To a pound of water, at 172, add a pound of ice at 32. The temperature will not be the arithmetical mean, as in expt. 6, but much below it, viz. 32* From 102, therefore, the arithmetical mean, take 32 5 the remainder, 70, shows the quantity of caloric, that combines with a pound of ice, during liquefaction ; that is, as much caloric is absorbed by, and unites chemically with, a pound of ice during its conversion into water, as would raife a pound of water from 32 to 102?. 9. Other examples of the absorption of caloric , during the liquefaction of bodies, are furnished by the mixture of snow and nitric acid j or of snow and common salt, both of which, in common lan- guage, .produce intense cold'*. Most neutral salts, also, duringsolution in water, absorb much caloric, and the cold thus generated is so intense as to freeze water, and even to congeal mercury. The former experiment, however, may easily be repeated. Add to 32 drachms of water, n drachms of muriate of ammonia ; 10 of nitrate of potash ; and 16 of sul- phate of soda, all finely powdered. The salts may be dissolved, separately, in the order set down. A thermometer, put into the solution, will show that the cold produced is at or below freezing ; and a * The extraordinary powers of muriate of lime and snow in generating cold, will be described hereafter. 12 little water, in a thin glass tube, being immersed in the solution, will be frozen in a few minutes. Various other freezing mixtures are described in Mr. Walker's papers in the Philosophical Trans- actions for 1787, 88, 89, & 95. IO. On the contrary liquids, iu becoming solid, evolve or give out caloric, or in common language, produce heat. (A.) Water, if kept perfectly free from agitation, may be cooled down below 32; but, on shaking, it immediately congeals, and the temperature dies to 32. B. To a saturated solution of sulphate of potash in water, or of any salt that is insoluble in alcohol, add an equal measure of alcohol. The alcohol, at- tracting the water more strongly than the salt re- tains it, precipitates the salt, and considerable heat is produced, CALORIC THE CAUSE OF VAPOUR. 1 1. Steam has exactly the same temperature as boiling water. Let a tin vessel be provided, having a hole in its cover, juft large enough to admit a thermome- ter. Fill it partly with water, and let the bulb of the thermometer be an inch or two above the sur- face of the water. When the water boils, the ther- mometer, surrounded by steam, will rise to 212, which is precisely the temperature of the water be- neath. Yet water, placed on a fire, continues to receive heat, very abundantly, even when boiling hot j and as this heat is not appreciable by the ther- mometer, it must be in a state of chemical union. 12. The absorption of caloric, during evaporation, shown by experiment. Moisten a thermometer with alcohol, or with ether, and expose it to the air, repeating these operations alternately. The mercury of the ther- mometer will sink at each exposure, because the IS volatile liquor, during evaporation, robs k of its heat. In this way, (especially with the aid of aa apparatus, described by Mr. Cavallo in the Phil. Trans, for 1781, p. 509) water may be frozen in a thin and small glass ball, by means of ether j ancj also by immersing a tube, containing water at the bottom, in a glass of ether, placed under the. re- ceiver of an airpump. During the exhaustion of the vessel, the ether will evaporate rapidly; and, robb-: ing the water of heat, will completely freeze it. 13. On the contrary t vapours during their center* sion info a liquid form, evolve, or give out, much caloric. The heat given out, by the condensation of steam, is rendered apparent by the following expe- riment. Mix 100 gallons of water, at 50, with one gallon of water at 212*. The temperature of the water will be raised about i\ degree. Con- dense, by a common still-tub, one gallon of water from the state of steam, by ico gallons of wa- ter, at the temperature of 50. The water will be raised 1 1 degrees. Hence, eight pounds of water, condensed from steam, raise 100 gallons of cold water, p| degrees more than eight pounds of boil- ing water ; and by an easy calculation, it appears, that the caloric imparted to the 100 gallons by the steam, if it could be condensed in one gallon of water, would raise it to 950?. A pound cf water, therefore, in the state of steam, contains more caloric, than a pound of boiling water, in the pro- portion of 950 to 212. ART. III. GASSES IN GENERAL. For performing the necessary experiments on passes, many articles of apparatus are essential, * This experiment will be equally conclusive, if repeated on a smaller scale. 14 that cannot be included in a portable chemical , chest, which may yet, however, contain the mate- rials for procuring gasses. It may assist the student in obtaining the necessary instruments, if a few of the most essential be here enumerated. I shall men- tion none, however, except such as are necessary in making a few general experiments on this inte- -resting class of bodies. The apparatus, required for experiments on gasses, consists partly of' vessels fitted for containing the materials that afford them ; and partly of vessels adapted for the reception of gasses, and for submit- ting them to experiment. j. For procuring such gasses, as are producible /without a very strong heat, glass bottles, furnished with ground stoppers, and benr tubes, are sufficient. .Of these several will be required of different sizes and shapes, adapted to different purposes. If these .cannot be procured, a Florence flask with a cork perforated by a bent glass tube, will serve for obtain- ing some of the gasses. Those gasses, that require for their liberation a red heat, may be procured by exposing to heat the substance, capable of affording them, in earthen retorts, or tubes*; or in a gun barrel, the touch- jiole of which has been accurately closed by an iron pin. To the mouth of the barrel must be affixed a glass tube, bent so as to convey the gasses, where- ever it may be requisite. 2. For receiving the gasses, glass jars of various sizes are required, some of which should be furnished with necks at the top, fitted with ground stoppers. * Very compact earthen retorts and lubes are m?de by Messrs. Wedgwoods and Byeriy of Etruria. Others, also, less c!ose 4n thL'ir texture, but Jess apt to break in the tire, may be had of Messrs. Pugh and Speck of Booth Street, Spital Fu-ldi, London., &l\j make portable liiriuiccs, crucibles, &c. 15 Tliese jars will, also, be found extremely useful iiv experiments on the properties and effects of the gasses Some of them ihould be graduated into cubical inches. To con t;i in these jars, when in use, a vessel will be necessary, capable of holding a lew gallons o ; water. This may either be of wood, if of consider- able size; or, 51 small. or" tin, japanned or painted. Its size may vary with that of the jars employed ; and about an inch and half from the top, it should have a ^helf, on which the jars may be placed, wo.- n iilltd with air, without the risk of their being oveiset. A ^lass tube, about 18 inches long and 3 quarters of an ir eb diamretvr closed at one end, p.nd dividecl into and ; - ^nths of inches, will be required for -^certdininu; the purity of air. It'" .should be accompanied, also, with a small mea- sure, containing aboufct wo cubjc inches, and similarly graduated. Besides- these, the experimenter should be furnished with air funnels, for transferring gasses from wide to narrow vessels. These, and almost every other article of apparatus, necessary for ex- periments on gashes, may be seen figured, in the plates to Dr Priestley's Experiments on Air, in 3 vols. bvo. 3 and in those subjoined to Lavoisier's Elements For those passes, that are absorbed by water, a mercuiiai trough is necessary. For the mere exhi- bition of a few experiments on these condensible- gasses, a small wooden trough, i j inches long, 2- wide, and 2 deep, cut out of a solid block of mahogany, is sufficient ; but for experiments ot re- search, 01142 of considerable size i* required. Previously to undertaking experiments on other ga:-ses, it may be well for an unpractised experimea- B 2 16 talist to accustom himself to the dexterous manage- ment of gasses, by transferring common air from on vessel to another of different sizes. Of experiments illustrative of the nature of gasses in general, it may be proper to mention one or two, that show the mode in which caloric exists in this class of bodies. In vapours, strictly so called, as the steam of water, caloric seems to be retained with bat little force j for it quits the water, when the vapour is merely exposed to a lower temperature. Hut, in gasses, caloric is united by very forcible affinity, and no diminution of temperature, that has ever yet been effected, can separate it from some of them. Thus the air of our atmosphere, in the most intense arti- ficial or natural cold, still remains in the aeriform state. Hence is derived one character of gasses, viz. that they shall remain aeriform, under almost all variations of pressure and temperature ; and in this class are, also, included those aerial bodies, which, being condensed by water, require confinement over mercury. '1 he following experiment will show tlvu the caloric, contained in gasses, is chemically com. bined. Into a small retort, put an ounce or two of com- mon salt, and about half its weight of sulph uric acid. By this process, a great quantity of gas is produced, which" might be received and collected over mercury. But, to serve the purpose of this experiment, It-t it pass through a glass balloon, having two openings (as in the 4th plate of Lavoisier, tig. i. G }, into one of which the neck of the retort passes, while, from the other, a bent tube proceeds ( of the same fig.)' which ends in a vessel of water, before clos- .ing the apparatus, let a thermometer b<* included iu the balloon to show the temperature ot the gab. It 17 \vill be found, (hat the mercury, in this thermometer, will rise only a few degrees, whereas the water, in the vessel which receives the bent tube, will sooa become boiling hot. In this instance, caloric flows from the lamp to the muriatic acid, and converts it into gas 5 but the heat, thus expended, is not appreciable by the thermometer, and must, there- fore, be chemically combined. 1 The caloric, how-' ever, is again evolved, when the gas is condensed by water, and, in this experiment, we trace it into combination, and again into the state of un- combined caloric. For demonstrating the influence of variations of atmospheric pressure on the formation of gasses> better experiments cannot be devised than those of Lavoisier. See his Elements, chap. i. But as some students, who have the" use of an airpump, may not possess the apparatus described by Lavoisier, (the glass bell and sliding wire), it may be proper to point out an easier mode of showing the same fact. Into a glass tube, about six inches long, and half an inch diameter, sealt d at one end, put a small quantity of ether ; and fill the -tube with, water, tinged blue by litmus. The ether will swim on. the / surface of the water. Place the thumb, expedju-y ously, over the open end of the tube, so as. to coji- ij-ne the water and ether without including ahy air along with them ; and set the tube, inverted, in a jar of coloured water; removing the thumb, when- this has been effected. ^yhen the above apparatus is covered with the receiver of an air- pump, and the air is exhausted, the ether will be changed into a gas, which will fill the tube, and expel the water. On restoring the pressure of the atmosphere, the ether v/ill again become liquid* 18 ART. IV. OXYGENOUS GAS. 1. Oxygenous gas may be procured from various *ttbs(at;ce$ t A: From oxyd of manganese, heated to redness in a gun barrel, or earthen retort ; or from the same oxyd, heated by a lamp in a retort or gas bottle, with half its weight of strong sulphuric acid- B. From the red oxyd of lead (the common red lead used by painters) heated either with or without fnlphnric acid. C. From various other oxyds, as will be hereafter mentioned. D. From nitrate of potash (common saltpetre) made red hot in a gun barrel, or in an earthen retort. E. From oxygenated muriate of potash, heated in a small glass retort, coated with c'ay j or in an earthen retort. The oxygenous gas thus cproduced is much purer than that obtained in any other mode, especially the last portions, which should be kept separate. This gas has the following properties : 2. It is not absorbed, by' water, or at least is so sparingly absorbed, that when agitated in contact with water, no perceptible diminution takes place. ^. Ail combuxdbk bodies burn in oxygenous gas uith greatly increased splendor. (A.) A lighted wax taper, fixed to an iron wire, and let down into a H vessel of gas, burns with great brilliancy. {See Lavoisier's ^th plate, fig. 8.) Jl the 1^ per be blown out, and lei down into a vessel of the gas, while the s null' remains red hot, it instantly rtkindles^vith a slight explosion. B. A retl hot bit of charcoal, fastened to an iron wire, and immersed in the gas, throws out beautiful sparks. 19 C. The light of phosphorus, placed on- a little tit* cwp, aud burnt in this gas, is the brightest that can be in any mode produced. D. Procure some thin harpsichord wire, andtwiafc it round a slender rod of iron or glass, so as to coil it up in a spiral form. Then withdraw the rod, and tie a little thread round one end of the wire, for about the length of -^ inch, which end is to be dipped into melted sulphur. The other end of the wire is to be iixed into a cork f so that the spiral may hang ver- tically. Fill, also, with oxygenous gas, a bottle capable of holding about a quart, and set it with its mouth upwards. Then light the sulphur, and intro- duce the wire into the bottle of gas, suspending it by t'~e cork. The iron will burn with a most bril- liant light, throwing out a number of spai ks, which fall to the bottom of the bottle, and generally break i*. .This accident, however, may frequently be prevented by pouring sand into the bottle, so as to lie about half an inch deep on the bottom. (See Lavoisier's 4th plate, fig. 17.) . A little of Homberg's pyrophorus, a substance to be hereafter described, when poured into this gas, immediately flashes like inflamed gun-powder.. 4. During every combustion -in oxygenous '#.?, the gas suffers a material diminution To exhibit this- experimentally, in a manner perfectly free from all sources of error, would require such an apparatus, as lew persons are likely to possess. The apparatus required, may be seen described iiv the 6th chapter of Lavoisier's Elements. The fact may, however, be shown less accurately, in the following manner. Fill, with oxygenous gas, a jar of moderate size, which has a neck and ground glass stopper at the top. 1 hen, with the assistance of a stand, formed of bent iron wire, (like that shown in the plate to Nicholson's Chemistry, fig. 16,) place a shallow tin 20 vessel, containing' a bit of phosphorus or sulphur, three or four inches above the level of the water of a pneumatic trough. Invert the jar of oxygenon* gas, cautiously and expeditions!}', over this cup, ib as to confine it with its contents in the gas, and pressing down the jar. to the bottom of the trough, open the stopper. A quantity of gns will imme- diately rush out, and the water will rise to the same level within the jar as without. \\hen t.;is has taken place, .let fire to th- siijjp&ur or phosphorus by an iron wire, and instant'y put in '..he stopper. The first effect of the c.;;r : bus lion \v i! be a depression of the water within the jar ; but when the combustion has closed,, and the vessel has cooled, a considerable absorption will be found to hare ensued. 5. All bodies, by combustion in oxygenous gas, ac- quire an addition to their weight ; and the increase is in proportion to the quantity of -gas absorbed. To prove this by experiment, requires, <;Ko, a com- plicated apparatus \ and the reader,, who cannot possess himself of this, must remain satisfied with the account given by Lavoisier of his experiments, establishing the principle, hi chapter $th of his Elements. 6. Qyc$gnottsi % $as si'pporfs, eminently, animal life. It will be found that a. mouse, bird, or other-small animal, will live six times longer in a vessel of oxygenous gas, than in one of atmospherical a: r of the same dimensions. 7. This effect see?} is connected itilti the absorption, of oxygen by the blood. Pass up a little dark colouied blood into a jar partly filled with oxygen gas, and standing over mercury. The i ... will in part be absorbed, and the colour of tlu bliod will be changed to a bright and florid red. This change to red may be shown by pulling a little b'cod into a- common vial iiiled wi h oxygenous gas, and shaking .it up,i ' ART. V. AZOTIC OR NITROGEN GAS. T. Azotic Gas may he procured, though not ab- solutely pure, yet sufficiently so for the purpose of exhibiting its general properties, in the following manner. Mix equal weights of iron filings and sulphur into a paste with water, and place the mixture in a proper vessel, over water, on a stand similar to that described, Art. IV. No. 4. Then invert over it a jar full of common air, and allow this to stand exposed to the mixture for a day or two. 1 he air, contained in the jar, will gradually diminish, as will appear from the ascent of the water within the jar, till at last, only about three-fourths remain of its original bulk. The vessel, contain- ing the iron and sulphur,' must next be removed, by withdrawing it through the water; and the remain- ing air may be made the subject of experiment. 2. This gas has the following properties: A. It is not absorbed by water. B. It immediately extinguishes a lighted candle", and all other burning substances. C. It is fatal to animals that are confined in it. D. Plants, however, live in it, and even flourish. E. When mixed with pure oxygenous gas, in the proportion of one part to three oi the latter, it com- poses a mixture, resembling atmospheric air in all its properties. Of this any one may be satisfied, by mixing three parts of azotic gas with one of oxy- genous gas j and immersing in the mixture a lighted taper. The taper will burn as in atmospherical air. ART. VI. ATMOSPHERIC AIR. The air of our atmosphere, it appears, therefore, fom the iuiegoing fa6b, is a mixture, or rather ^a 22 corabi nation, of two different gasses, viz. oxygenous gas, and azotic gas. The former of these two seems to be the only ingredient on which the effects of the air, as a chemical agent, depend. Hence combustible bodies burn in atmospheric air, only in confequence of the oxvgenoiis gas, which it contains ; and when this h exhausted, air is na longer capable of supporting combustion*. The abstraction, from the air, of its oxygenous gas, \vill be rendered apparent by the following expe- riments. 1. Burn a little sulphur or phosphorus, in the manner described, Art. IV. No. 4. substituting for pxygenous gas, common atmospherical air. The combustion \viil in this instance be less vivid ; will cease sooner 5 and the absorption, when the vessels have cooled, will be much less considerable than in- die former case. 2. Take two tubes, each a few inches long, closed at one end, and divided into aliquot pares. Fill the one with atmospherical air, the other with oxygenous gas, and invert them in two separate cups filled with a solution of s.ulphuret of potash. The suVphmet will ascend gradually within ths tube of common air, till, after a few days, only about three-fourths of its original volume remain : But in that containing oxygenous gas, it will ascend much higher j ai-d if the ga> be pure, will even absorb the whole. i he explanation of this fact is, that liquid sulphuret of potash has the pioperty of absoroirg oxygen, but not azote. It, therefore, acts in ai- nuspheric air, only as long as any oxygenous gas remains ; and may be employed as a rneaus of ascer- taining the quantity of this gas in th\' afii.o^phcro at * Certain combustible bcdi s even cense to bun in atmos- pheric :ur, long before its oxygenous j crticn is consumed j igr icaSjns that vii.il hereaflti bu given. 23 different times, and in distant places. An improved instrument, thus graduated, has lately been employed by Guyton as an Eudiwncter* > (See Nicholson's Philosophical Journal, Vol. I page 268 ; orTilloch's Philosophical Magazine, Vol. ILL p. 191.) 3. AtiwjSfjheric air ministers to the support of animal life, only in consequence of the oxi,ge7ious gas ichich it contains. Air, after having been received into the lungs, and again expired, is found to have lost considerably of its oxygenous part, viz. 10 or 12 per cent. It proves fatal lo rnimals, however, long before the whole of this purer portion is wholly exhausted; and hence it appears, that a considerable proportion of oxygenous gas is even necessary to fit the air for supporting respiration,. As the analysis of expired air requires an acquaintance with another gas not hitherto described, viz. carbonic acid, its examination will be postponed to a future occasion. ART. VII. HYDROGENOUS GAS. 1. To procure hydrogenous gas, let sulphuric acid, previously diluted with five or six. times its weight of water, be poured on iron filings, or on small iron nails, in a gas bottle or fmall retort. An effer- vescence will ensue, and the escaping gas may be collected in the usual manner. This gas has the following properties : 2. It remaim permanent over water, or is not ab- sorbed in- any notable proportion. 3. // is inflammable. This may be shown by the following experiments. A. Fill a small jar with the gas, and holding it with the mouth downwards, bring the gas into contact * Other Eudiometers will he described hereafter, 24 with the flame of a candle. The air will take fire, and will burn silently with a lambent flame. B. Fill, with this gas, a bladder which is furnished Vith a stop cock, and with a small pipe, of diameter less than that of a common tobacco pipe. Press the air out through the pipe, and on presenting a lighted candle the steam will take fire. If this apparatus cannot be procured, a very simple contrivance will answer the purpose. Break olf part of an eight ounce vial, within an inch or two from the bottom, by setting fire to a string tied round it, and mois- tened with spirit of turpentine. The vial will then resemble a jar with an open neck at the top. Next bore a small hole through a cork that fits the neck of the vial, and insert in it part of a common tobacco pipe, which may be fixed into the neck of the bottle, by a cement of resin and bees wax. Then fill the bottle with water, and hold it with the thumb pressed down on the aperture of the pipe, while hydrogenous gas is passed into it. When the bottle is full of gas, remove the thumb, press the bottle down into the water, and on the approach of a candle the stream of air from the pipe will take fire 1 prefer this mode of making the experiment to the common one of inflaming the gas as it pro- ceeds, through a small tube, from the bottle in which it is produced j because I have once seen an 'explosion, and frequently heard of similar accidents, from the latter mode of making the experiment. C. In a strong bottle capable of holding about four ounces of water, mix equal parts of common air and hydrogenous gas. On applying a lighted candle, the mixture will burn, not silently as in expt. A, but with a sudden and loud explosion. If a larger bottle be used, it should be wrapped round with a handkerchief, to prevent the glass from doing any injury, in case the bottle should burst. D. The same experiment may be repeated with oxygenous gas, instead of atmospherical air ; chang- ing the proportions, and mixing only one part of oxygenous gas with two of hydrogenous. The report \villbeconsiderablylouder. The bottle should be a very strong one, and shouUl be wrapped round with cloth, to prevent an accident*. E. The same experiment may be made over water, by means of the electric spark. Procure a strong tube about three quarters of an inch diameter, and 12 inches long, closed atone end. ^bout a quarter or half an inch from the sealed end, let two small holes be drilled, opposite to each other, and into each of these let a brass conductor be cemented, so that the two points may be distant from each other, within the tube, about one eighth of an inch. Into this tube standing over water, pass about a cubic inch, or less, of a mixture of hydrogenous and oxygenous gasses, in the proportion of two measures of the former to one of the latter. Hold the tube firmly, and pass an electric spark through the mixed gasses. An immediate explosion will take place 5 after which the gasses, if pure, and in the proper proportion, will be found to have disap- peared entirely. If atmospheric air be used, the re- maining gas will be found to be unfit for supporting combustion, the hydrogenous gas having robbed it of all its oxygen. Hence, the inflammatiop of hy- drogenous gas, in graduated tubes, has been en} ployed as a means of measuring the purity of air, and is the principle of Volta's eudiometer. * These experiments may, also, be m light the stream j and bring it under the glass bell, by raising this, and depressing it into the mercury, as soon as the inflamed gas is introduced. A portion of air will escape at first, in consequence of the rarefaction. As the combustion continues, water will form, and will cendense on the sides of the glass. This water 29 is produced by the union of hydrogen with the oxygen contained in atmospheric air. B. Those persons who are not possessed of a sufficient quantity of quicksilver, to repeat the above experiment, may substitute the following. Procure a large glass globe, capable of holding three or four quarts, and having two openings, opposite to each other, v. hich may be drawn out for a short distance, like the neck of a retort. Inflame the stream of hydrogen gas, and introduce it into the centre of the globe. The rarefied and vitiated air will ascend through the upper aperture of the globe, and a con- stant supply of fresh air will be furnished from, beneath. By this combustion, a quantity of water will be generated, which will be condensed on the inner surface of the vessel. C. A simple --. nd ingenious apparatus, Jess costly than any other intended for the purpose of exhibiting the composition of water, is made by Mr. Cuth- bertson, of London. It may be seen described and figured in Nicholson's Journal, Vol. II p. 235 ; or in the Philosophical Magazine, Vol.11, p 317. D. Those persons, who h;.ve the oppo: tunity of repeating this interesting experiment on a large scale, and with an accurate attention to proportion, may consult Lavoisier's Iflements. K. By firing repeated portions of a mixture of oxygenous and hydrogenous gasses, over mercury,, a sensible quantity of water will ac last be pn>- duced. 2. ANALYTIC EXPERIMENTS. The analytic experiments on water are of two kinds, ist, such as present us with one of its ingredients only, in a separate and dis i ct form 5 zdly,. such as present us with its two component c 3 so principles, the hydrogen and oxygen, mixed toge* ther in the state of gas. Of the first kind are the following: A. Procure a gun barrel, the breech of which has been removed, so as to form a tube open at each end. Fill this with iron wire, coiled up in a spiral form. To one end of the barrel adapt a small glass retort partly tilled with water, and to the other a bent glass tube, the open end of which terminates under the shelf of the pneuraa to-chemical apparatus. Let the barrel be placed horizontally, (or rather with that end, towliieh the retort is fixed, a little elevated) in a furnace, having two openings in its body op- posite to each other, or in a grate like that figured by Lavoisier plate 7, figure 11. Light a fire in the Uirnace ; and when the gun barrel has become red hot, apply a lamp under the retort. The steam of the water will pass over the red hot iron, and will be decomposed. Its oxygen will unite with the iron - y and its-hydrogen will be obtained in the form of a gas. This is the readiest and cheapest mode of procuring, hydrogen gas, when wanted in consider- able quantity. B. The same experiment may be repeated ; substituting an earthen tube for a gun barrel, and weighing the iron wire, accurately, both befc-re and after the experiment. The iron will be found to have gained weightvery considerably ; and if atten- tion be paid to the weight of the water, that escapes decomposition, by an addition to the ap- paratus, similar to that employed, by Lavoisier, (plate 7, fig. n, SandH) and to the weight of the gnsses obtained, it will be found that? the weight gained by the iron, added to that of the hydrogen gas, will make up exactly the weight of the \vaier ; that has disappeared. From experiments SI of this kind-> conducted with' the utinost. attend lion to accuracy, as well as from synthetic expert* nients, it appears that water is compounded of 85 percent oxygen, and i5 : hydrogen, by weight, very nearly. But as hydrogen gas is eleven times lighter than common air, the proportion of gasses, by volume, required to form water, is about two of hydrogen to one of oxygen gas. C. Water may be decomposed, in a similar ap- paratus, over charcoal instead of iron. The -results*, however, are different in this case, as will appear from a subsequent section. D. Another mode of effecting the decomposition of water yet remains to be mentioned, in which not the hydrogen but the oxygen is obtained in a gaseous state. This is by the action of living vtge- tables j eitherentire, or by mems of their leaves only. Fill a clear glass globe with water, and put into it a number of green leaves* from almost any tree or plant. A sprig or two of mint will answer the pur- pose perfectly well. Invert the glass, and place it with its mouth downwards* in a vessel of water. Ex- pose the whole apparatus to the direct light of the sun, which will then fall on the leaves, surrounded 1 by water. Bubbles of air will soon begin to form on the leave.*, and will increase in size, till at last they rise to the top of the vessek This process- may be carried on, as long' as- the vegetable con<- tinues healthy 5 and the gas, when examined, will prove to be oxygenous gas nearly pure. In this experiment, the hydrogen combines with the planr> to the nourishment and support of which it contri^ butes,while the oxygen is set at liberty. 2dly. The processes-, by which the elementary parts of water are separated from each other, and both are presented in an aeriform state, as a mixture of 32 of hydrogen and oxygen gasscs, are dependent on the agency of electricity. A. The first of these experiments requires, for its performance, the aid of a powerful electrical ma* chine. This fact was the discovery of a society of ingenious Dutch chemists; and the principal cir- cumstance, in the experiment, is the transmission of electrical shocks, through a confined portion of water. The apparatus employed in this experiment of Messrs. Deimen and Van Troostwyk, h a glass tube, about one eighth of an men diameter, and 12 inches long, one of the ends of which is sealed her- metically, a go d wire being insert _,1 at this end, and projecting about an irch and hair within the tube, /iboutthe distance of riy?-eighthsi : :.n inch from the extremity of this, another wire is tr be iixed, which may extend to the open end of the tube. The tube is next to be rilled .vith distilled water, and to be placed inverted in a vessel of the same. When thus dispf sed, electrical shocks are to be passed, between the two ends of the wire, through the wter , and if these shocks be sufficiently strong, bubbles of air will be formed at the explosion, and will ascend, till the upper part of the wire is uncovered by the jwater. As soon as this is effected, the next shock that is passeel will set lire to the air; and the water \vili rise again in the tube, a very small quantity of gas remaining. Now as hydrogen and oxygen gasse.s, in a state of admixture, are the only ones, that are capable of inflaming by the electric shock ; and as there is nothing in the tube, besides water, that c , /.t, :-j:d them in this experiment, \ve may safely infer, that the evolved hydrogen anj oxygen gas.ses arise from decomposed w. ter. B. An improved apparatus, exhibiting the same experiment with less trouble to the operator, has S3 been invented by Mr. Cuthbertson, ami may be seen described and figured in Dr Pearson's paper, in the Phil Trans, lor 1797^ or in Nicholson'* Journal, Vols. i and 2. C. 'I he same experiment mny be performed witft 1 theaidofan npparatusof greatMmpliciiy, and which ii is in the power of almost any person to make for himself. This is the newly discovered pile of' signior Voltaj a discovery, which for cariosity, and importance in a philosophical view, ranks with the first that have been made, during the present cen- tury. It is constructed in the following manner. Procure, at a brazier's or copper smith's, 30, 40; or 50 pieces of zinc or speltre, cast in sand, of the size of half crowns or shillings, but rather thicker. A corresponding number of half crowns or shil- lings will, also, be required, according to the size of the pieces of zinc, that may be employed. Let an equal number of pieces of woollen cloth be cut of a circular shape, to correspond with the pieces of zinc j and steep these in a strong solution of ccmmon salt in water. Then dispose the three sub. stances, alternately, in the following order, silver> zinc, moistened cloth $ silver, zinc, &c. till a sufficient number of these triplicates, not less than 20 or 30, have been thus arranged, the silver terminating the pile at the top. In order to facili- tate the touching of the bottom piece of silver, it may be well to put under it a slip of tinfoil or Dutch leaf, which may project a few inches. Next, let the hands be moistened with salt and water, and on touching the piecj of tinfoil wilh one hand, and the uppermost piece of silver with the other, a: shock will pass through the arms, which will be strong, in proportion to. the number of pieces Q& zinc, &c. that are employed. 31 VHth this apparatus, tlie decomposition cf water is effected with the utmost facility. Take a narrow glass tube 3 or 4 inches long; (it each end with a cork, penetrated by a piece of slender iron wire, and rill the tube uith water. Let the ends of the two wires be distant from each other, about three- fourths of an inch j and let the one be made to communicate with the bottom of tltfe pile, the other with the top. On making this com muni cation, bubbles of air will form, and will ascend to the top of the tube j the wire being rapidly oxydated. In this experiment, water is decomposed : Its oxygen unites with the iron j while its hydrogen appears in the state of ggj. If this experiment be made with the substitution, for iron, of some metal that is not oxydated by water, as gold for example, we obtain a mixture of Hydrogen and oxygen gasses, as in the experiment of Mess;s. Deimen and Van Troostwyk. In Mr. Nicholson's Journal, a variety of interest- ing observations on the phenomena, produced by Volta's Galvanic Pile, have bten published by Messrs. Nicholson, Carlisle, Cruickshank, Davy, and others. ART* IX PROPERTIES AND EFFECTS OF WATER. T. Water contains air. This may be shown by placing a glass vessel of water under the receiver of an air pump. During the exhaustion of the receiver, bubbles of air will be seen to ascend very plentifully. Much air escapes, also, from water, during ebullition, and may becvllected by a proper apparatus. 2. Water is contained in the air of the atmosphere, eve?i during the driest weather. Expose to the air, in a shallow vessel, a little carbonate of potash (not crystallized, but the common salt of tartar.) In a few days, it will have become moist, or detiquiated. On the same principle, water, exposed to the air in a shallow vessel, disappears, being dissolved by the -atmosphere. 3. IVater dissolve* a great -variety of solid bodies. The substances, on which it exerts this effect, are said to be soluble in water; and there are various degrees of solubility, see Art. I, No. 6. 4. During the solution oj bodies in water, a change of temperature ensues. In most instances, an ab- sorption of caloric, (in other words, a production of cold) is attendant on solution, as in the examples given in Art. II, No. 9. Put, in other cases, caloric is evolved, or heat is produced. Thus common salt of tartar, during solution in water, raises the temperature of its solvent; and caustic potash, in a state of dryness, does the same still more remarkably. Both carbonated and pure potash, however, when crystallized, observe the usual law : and absorb caloric during solution. Now as their difference, in the crystallized and uncrystallized state, depends chiefly on their containing, in the former but not in the latter, water chemica'ly combined ; we may infer, that the cold, produced during the solution of salts, is occasioned by the conversion of the water, which exifts in these bodies, from a solid to a liquid form. . During the solution of salts in water, a quantity ef air is disengaged. This air was, partly, contained mechanically in the salt, and partly in the water. That it does not arise, entirely, from the former source, is proved by varying the experiment, in the following manner. Let an ounce or two of sulphate 36 of soda be put into a vial : and pour on this as mwtch water as uill completely fill the bottle. The air, contained in the pores of the salt, will be thus dis- engaged j but only a small portion of the salt will be dissolved, agreeably to the principle laid down. Art. I, No. 7. Let the vial be shaken, and the whole of the salt will disappear; a fresh portion of air being liberated during solution. The air that now appears, is extricated from the water, in consequence of the affinity between the water and the salt, being stronger than that between the water and the air. It is, therefore, a case of single elective affinity. 6. During the solution of bodies , the bulk of water changes. Take a glass globe, furnished with a long narrow neck (commonly termed a matrass) and put into it an ounce or two of sulphate of soda. Then Sdd as much water as will fill the globe, and about fhree-fourths of the neck. This should be done with as little agitation as possible, in order that the salt may not dissolve, till required. Mark, by tying a little thread, the line where the water stands 5 and tfien agitate the matrass. The salt will dissolve - y air will be set at liberty ; and, during the solution, die water will sink considerably below its level. This contraction of bulk is owing to the diminution of temperature $ and when the water has regained its former temperature, it will also be found, that fts bulk is increased by the addition of salt. The bishop of Llandaff found that water exhibits a manifest augmentation of bulk, by dissolving only the two thousandth part of its weight of salt $ a fact Sufficiently decisive against that theory, which sup- poses pores in water, capable of receiving saline todies without an augmentation of volume* 57 7 Water has its solvent power increased by di~ minishing the pressure of the atmosphere. Jnto a Florence flask, put a pound of sulphate of soda j pour on it barely a pint of water j and apply heat so as to boil the water. The whole of the salt will be dissolved. Boil the solution for several minutes, pretty strongly, to as to drive out the air \ and cork the bottle tightly, immediately on its removal from the fire. To prevent, more completely, tho admission of air, tie the cork over with bladder. As the vessel cools, an imperfect vacuum will be formed over the solution 5 for the steam, which arif.es during the ebullition, expels the air, and takes its place. The steam is condensed again, when the vessel cools. The solution, when perfectly cold, may be shaken without any effect ensuing, so long as the vessel is kept closely stopped; but on removing the cork, and shaking the vessel, the so- lution will immediately congeal, and heat will be produced. This experiment, besides the principle, which it is peculiarly intended to illustrate, exem- plifies, also, the general rule laid down, Art. If, No. 10, viz. that, caloric is always evolved, during the transition of bodies from a fluid to a solid Hate ; and it furnishes a fact exactly the converse of that, in which cold is produced, or caloric absorbed, during the solution of salts. 8. Jt is unnecessary to add any thing, to what has been already said in a former section, respecting the combination of caloric with water, constituting iteam ; or to the history of the phenomena attending its conversion into ice 5 except that during the latter change, its bulk is enlarged in the proportion of 9 to 8, and that in consequence of this expansion, water, during congelation, is capable of bursting the strongest vessels 5 and becomes, also, specifically D 38 lighter. Hence ice swims always on the surface of water. ART. X. ALCALIS. General qualities. The properties, common to all the three alcalis, may be shown by those of a solution of pure potash. A. The alcalis change vegetable blue colours, as that of an infusion of violets, to green, B. They have an acrid and peculiar taste. C. They serve as the intermedia between oils and water, see Art. I, No. 9. D. They corrode woollen cloth ; and, if the so- lution be sufficiently strong, reduce it to the form of a jelly. PURE POTASH, AND PURE SODA. These alcalis may be procured, in a dry state, by evaporating tht-ir respective solutions, the mode of preparing which will be hereafter pointed out. The alcalis, thus obtained, are very far from a state of complete chemical purity. Their properties, also, in a solid form, are not particularly interesting ; as most of these may be exhibited in a state of solution. It may be proper, however, to state, A. That they powerfully attract moisture from the atmosphere, or deliquiate. B They readily dissolve in water, and produce heat during their solution. C. They are not volatilized by a moderate heat, and hence have been called fixed alcali$. PURE AMMONIA. i. Ammonia, in its purest form, subsists in the state of a gas. In order to procure it, one of the following processes may be employed. A. Mix together equal parts of muriate of am- monia, and quicklime, each separately powdered ; and introduce them into a small gas bottle or retort. Apply the heat of a lamp ; and receive the gas, that is liberated, over mercury. B. To a saturated solution of ammonia in water, or the pure liquid ammonia, in a gas bottle, apply the heat of a lamp, and collect the gas as in A. 2. This gas has the following properties. A. It has a strong and very pungent smell. B. It immediately extinguishes flame 5 and is fatal to animals. C. It is lighter than atmospheric air. Hence a jar filled with this gas, and placed with its mouth upwards, is soon found to change its contents for common air, which, being heavier, descends, and displaces the ammoniacal gas. I). It is not inflammable ; nor does it explode when mixed with hydrogen gas. E. It is rapidly absorbed by water. A drop or two of water, being admitted to this gas, confined over mercury, the gas will be immediately absorbed, and the mercury will rise, so as to fill the whole of the jar, provided the gas be sufficiently pure. Ice produces the same effect, in a still more remarkable manner. F. Water, by saturation with this gas, acquires its peculiar smell \ and constitutes what has been called liquid ammonia ; or, more properly, solution D 2 . 40 wf pure ammonia in water. This solution ngain yields its gas on applying heat, (see No. I. B ) G. This gas is decomposed by electricity. Provide a jar furnished with two conductors (as described, Art, VIT, No. 3, E.) and having admitted about a cubic inch of ammoniacalgas, pass through it ;i succession of electrical discharges. When 150 or 200 shocks have been passed, the gas will have Increased to three times its original bulk. Admit a small quantity of water. The gas will not, as before,, be completely absorbed by the water; but a part will remain. Hence it appears that some new gas has been generated ; and, on examination, it is found to be a mixture of hydrogen and azotic gasses. H. The decomposition of ammmonia may, also, be easily shown, by galvanizing, with the apparatus described, page 33, a saturated solution of am- monia in water. In this experiment, a consider- able quantity of gas is produced. Expose this over a solution of sulphuret of potash. A small part .of it will disappear, being oxygenous gas. The remainder consists of hydrogenous and azotic' gasses. -ACTDIFI ABLE BODIES ACIDS -COMBINATIONS OF ACIDS WITH ALCAL1S. ART. XI. ACIDS IN GENERAL. Acids in general have the following properties ; A. They redden vegetable blue colours. Hence blue vegetable infusions, and the papers stained with them, are tests of the presence of acids. To a little of the infusion of litmus, add a drop of dilute sulphuric, or any other acid, The colour will im- mediately change to red 41 B. They have a peculiar taste, expressed by the terms acid or sour. C. They combine chemically with atcalis, and totally destroy the peculiar properties of tfiose bodies. Let a few ounce measures of water be tinged blue with genuine syrup of violets. Add some solution of pure potash, and the colour will become green. Then gradually drop in sulph uric acid, much diluted ; and if this be done very cautiously, the blue colour will be restored. In this state, neither the alcali nor acid is in excess ; or, in other words, they are exactly saturated with each other. One of the most remarkable properties of the alcali and the acid, when separate, disappears, therefore, on combina- tion. And, on further examination, it will be found that all the other characteristics of the com- ponents are lost in the compound. ART. XII. CARBON CARBONIC ACID CARBO- NATES OTHER BINARY COMPOUNDS OF CAR- EON. 1. Carbon is obtained, though not absolutely pure, yet sufficiently so for the purposes of exhibi- tion, by charring, in a covered crucible, pieces of oak, willow, hazle, or other woods, from which the bark has been previously peeled. For purposes, to which it is applied in a powdered state, it may be purified, by powdering it, and washing it first with dilute muriatic acid, to separate any earths it may contain, and afterward with repeated affusions of distilled water. 2. In its aggregated state, carbon is black ; per- fectly insipid, and free from smell; brittle, and easily pulverized, D 3 42 COMBINATION OF CARBON WITH OXYGEN". 3. If a piece of charcoal be introduced cold into oxygenous gas, no effect will ensue -, but if the charcoal be previously made red-hot, it burns in this gas with considerable brilliancy. To perform this experiment with accuracy, and with the proper attention to the products, it should be made over mercury. The oxygen will unite with the carbon 5 2nd tf-e product is a compound of carbon and oxy- gen, which subsists over mercury in the state of gas. On this account, no diminution ensues. 4. Another mode of effecting the combination of carbon with oxygen, is by driving the vapour of water over red-hot charcoal, in an apparatus similar to that described, page 29, B. The water is de- composed -, its oxygen combines with the carbon -, while is hydrogen combines with another portion of carbon, and forms a compound, which will be hereafter described '? he union of carbon with oxygen, however produced, furnishes a compound, called CARBONIC ACID. I. To procure carb nic acid, sufficiently pure for the exhibition of its properties, neither of the above processes is advisable. The student may, therefore, have recourse to another, the rationale of which he will not, at present, understand 5 but which will be explained afterward. Into a common gas bottle, put a little powdered marble or chalk, and pour, on this, sulphuric acid diluted with 5 or 6 times its weight of water. A gas will be produced, which those, who have an opportunity, may receive over mercury ; but a mercurial apparatus is noi absolutely 43 essential ; since the gas may be collected over water, if used immediately when procured. Its properties are the following. A. It extinguishes fimne. Set a vessel, filled \vith the gas, with its mouth upwards, and let down a lighted candle. The candle will instantly be extinguished. B It is fatal to animak. Put a mouse or other small animal i?;to a vessel of the gas, and cover the vessel to prevent the contact of common air. The animal will die in the course of a minute or two. C. '/Aw gas is heavier than common air. Let a long glass tube, proceeding from a gas bottle con- taining the materials (No i ), be twice bent at right angles, like those figured in Lavoisier's 4th plate, fig. i, E. Let the open end of the longer leg reach the bottom of a glass jar, perfectly dry within, and standing with its mouth uppermost. The carbonic acid will expel the common air from the jar, because it is heavier. This superior gra- vity may be further shown as follows : When the jar is perfectly filled with the gas (which may be known by a lighted candle being instantly extinguished when let down into it) take another jar, of rather smaller size, and place, at the bottom of it, a lighted taper supported by a stand, ''hen pour the contents of the first mentioned jar into the second, as if you were pouring water The candle will be instantly extinguished, as effectually, as if it had been im- mersed in water. It is owing to its superior gravity, that carbonic acid gas is often found at the bottom of deep wells and of mines, the upper part of which is entirely free from it. Hence the precaution, used by the sinkers of wells, of letting down a lighted candle, before they venture to descend in person. 44 D. Carbcmic acid gas is absorbed by water. Fill partly a jar with this gas, and let it stand a few hours over water. An absorption will gradually go on, till at last none will remain. This absorption is infinitely quicker, when agitation is used. Repeat the above experiment with this difference, that the jar must be shaken strongly. A very rapid diminu- tion will now take place. In this manner water may be charged with its own bulk of carbonic acid gas; and it acquires, when thus saturated, a very brisk and pleasant taste. This impregnation is most commodiously effected in an apparatus, sold in the glass shops, under the name of Nooth's machine. E. From water, thus impregnated, carbonic acid is again set at liberty, on boiling the water, or on exposing it under the receiver of an air pump. During exhaustion, the gas will escape so rapidly, as to present the appearance of ebullition \ and will be much more remarkable than the discharge of air from a jar full of common spring water, confined, at the same time, under the receiver, as a standard of comparison. F. Carbonic acid gas, when combined with water, reddens vegetable blue colours. This may be shown by dipping, into water thus saturated, a bit of litmus paper ; or by mixing, with a portion of it, about an equal bulk of the infusion of litmus. This fac~t eitnblishes the title of the gas to be ranked among acids. G. Carbonic acid gas precipitates lime water. This character of the gas is necessary to be known -, because it affords a ready test of the presence of carbonic acid, whenever it is suspected. Pass the gas, as it proceeds from the materials, through a por- tion of lime water. This, though perfectly trans- parent before, will instantly grow milky. Or mix 45, equal measures of water saturated with carbonic acid, and lime water. The same precipitation will ensue. l j . By the application of the test G, it mill be found y that carbonic add is generated in several cases tf combustion. Fill the pneurnato-chemical trough with lime water, and burn a candle, in a jar filled with atmospheric air, ov ; er the lime water, till the flame is extinguished. On agitating the jar, the lime water will become milky. The same appearances will take place, more speedily and remarkably, if oxygenous gas be substituted. The carbonic acid, thus formed during combustion, by its admixture with the residuary air, renders it unfit for support- ing flame, sooner than it otherwise would be. Hence, if a candle be burnt in oxygenous gas, it is extinguished, long before the oxygen is totally ab- sorbed, because the admixture of carbonic acid with oxygen gas, in considerable proportion, unfits it for supporting combustion. Whenever any substance, by combustion in oxygenous gas or common air, over lime water, gives a precipitate, soluble with effervescence in muriatic acid, we may confidently infer that it contains carbon, J . The respiration (f animals is another source of carbonic acid. On confining an animal, in a given portion of atmospheric air, over lime water, this production of carbonic acid is evinced by a preci- pitation. The same effect is, also, produced more remarkably in oxygenous gas The production of carbonic acid by respiration, may be proved, also, by blowing the air from the lungs, with the aid of a quill, through lime water, which will immediately grow milky. The carbonic acid, thus added to the air, unfits it for supporting life, not merely by diminishing the proportion of oxygen gas, but ap- 46 parently by exerting a positively noxious effect. Hence a given quantity of air will supporc an animal much longer, when the carbonic acid is removed as fast as formed, than when suffered to remain in a state of mixture. It has been found that an atmosphere, consisting of oxygen gas, and carbonic acid, is fatal to animals, though it contain a larger proportion of oxygen, than the air we com- monly breathe. 2. Carbonic add gax exerts powerful effects on living 1 vegetables. These effects, however, vary according to the mode of its application. . Water, saturated with this gas, proves highly nutritive, when applied to the roots of plants. The carbonic acid is decomposed, its carbon forming a component part of the vegetable, and its oxygei* being liberated in a gaseous form. On the contrary, carbonic acid applied as an at- mosphere, by confining a living vegetable in this- gas over mercury, is injurious to the health of the plant, especially in the shade. M. Saussure, jun., found that a proportion of carbonic acid in common air, greater than one eighth, is always injurious to vegetation -, but that in this proportion it promotes their growth, and is manifestly decomposed. CARBONATES IN GENERAL. Carbonic acid is susceptible of combination with alkalis, earths, and metals, and forms an order of compounds termed carbonates At present, how- ever, we shall only attend to the results of its union with alkalis. CARBONATE OF POTASH. A. Carbonic acid gas is very abundantly absorbed by a solution of pure potash. The simplest mode of 47 showing this is the following. Fill a common vial with this gas over water; and when full, stop it by applying the thumb. Then invert the bottle in a solution of pure potash, contained in a cup, and rather more in quantity than is sufficient to iill the bottle. The solution will rise into the bottle, and, if the gas be pure, will fill it entirely. Pour out the alcaiine liquor; fill the bottle with water; and again displace it by the gas. Proceed as before ; and repeat the process several times. It will be found that the solution will condense many times its bulk of the gas ; whereas water combines only with its own volume. B. Tlie changes effected in the alcali may next te examined. It will be found to have lost much of its corrosive and penetrating taste, and will no longer destroy the texture of woollen cloth ; but it still turns green the blue infusion of vegetables. Before its absorption of this gas, no remarkable change ensued, on mixing it with diluted sulphuric acid; but if this, or any other acid, be now added, a vio- lent effervescence will ensue, arising from the escape of the gas, that had been previously absorbed. If the mixture be made in a gas bottle, the gas, that is evolved, may be collected, and will be found to exhibit every character of carbonic acid. C. In this state of combination with carbonic acid, potash generally occurs in the arts. The potash, and pearlash of commerce ; and the salt of tartar'and salt of wormwood of the shops, are car- bonates of potash of different degrees of purity. The quantity of carbonic acid, contained in these alcalis, may be learned by a very simple experiment. Put one or two hundred grains of the alcali into a Florence flask, and add a few ounce measures of water. Take, also, a vial filled with dilute sulphuric 18 acid, and place this, as well as the flask, in one scale. Balance the two, by putting weights into the opposite scale; and when the equilibrium is attained, pour gradually the acid into the flask of alcali, till an effervescence no longer ensues. When this has ceased, the scale containing the weights will be found to preponderate. This shows that the alcali by combination with an acid, loses consider- ably of its weight ; and the exact amount of the loss may be ascertained, by adding weights to the scale containing the flask and vial, till the balance is restored. D. As it is sometimes of importance to know what proportion of real alcali a given weight of potash or pearlash contains, it may be proper to point out how this information may be acquired. The strength of the alcali is in proportion to the quantity of an acid required to saturate it. Thus if an ounce of one kind of potash requires, for saturation, a given quan- tity of sulphuric acid; and an ounce, of another kind, requires twice that quantity, the latter is twice as strong as the former. In order, however, to obtain a sufficiently accuratestandard of comparison, it will be necessary to employ, constantly, an acid of the same strength. This may be effected, though not with absolute uniformity, yet sufficient for ordi- nary purposes, by diluting the common oil of vitriol of commerce to the same degree. For example, let the standard acid consist of onepartof sulphuric acid, and five of water. The strength of an atcali will be learned, by observing what quantity of this acid a given quantity of alcali requires for saturation. For this purpose, put half an ounce of the alcali, or any other definite weight, into a jar with a few ounces of water, and filtre the solution; weigh the dilute acid employed, before adding it to the alcali; then pour it in gradually, till the effervescence ceases, aud 49 till the colour of litmus paper, which has been reddened with vinegar, ceases to be restored to blue. When this happens, the point of saturation will be attained. Weigh the bottle, to ascertain how much acid has been added ; and the loss of weight will indicate the strength of the alcali. Another less accurate mode of determining the strength is founded on the following property of car- bonate of potash. E. Carbonate of potash dissolves very readily in water, which, at the ordinary temperature, takes up more than its own weight. Hence, when an alcali, which should consist almost entirely of carbonate of potash, is adulterated, as very often happens, with substances of little solubility, the fraud may be detected by trying how much of one ounce will dissolve-in two or three ounce measures of water. Jn this way, I have detected an adulteration of one third. There are certain substances of ready solu- bility, however, which may be used in adulterating ashes, as common salt for example j and, when this is done, we must have recourse to the above men* tioned test, for the means of discovery. F. Carbonate of potash, in the states which have been already described, is far from being completely saturated with acid. This sufficiently appears from its strongly alcaline taste. It may be much more highly charged with carbonic acid, by exposing its solution to streams of carbonic acid gas, in a Nooth's machine, or other apparatus. When a solution of alcali, after this treatment, is slowly evaporated, it forms regular crystals. In this state the alcali con- stitutes the crystallized carbonate of potash, which contains, per cent, poparts of alcali, 43 of acid, and 17 of water. It has therefore a much larger proportion of water and of acid than the common 50 carbonate, 100 parts of which are composed of 70 parts of alcali, 23 of acid, and 5 of water. G. The crystallized carbonate differs from the common one in the regularity of its form ; in the greater mildness of its taste; in remaining dry when exposed to a moist atmosphere ; and in being more sparingly soluble in water, which at the ordi- nary temperature takes up only one fourth of its weight. When carefully prepared, this is the purest form, in which carbonate of potash can be obtained. H. Carbonate of potash, in all its forms, is de- composed by the stronger acids, as the sulphuric, nitric, and muriatic, which unite with the alcali, and set the gas at liberty. CARBONATE OF SODA. A. The absorption of carbonic acid gas, by a solution of pure soda, may be exhibited by experi- ments, similar to those directed to be made on the solution of potash. Indeed every thing that has been said of the preceding carbonate, will apply to this ; except that the carbonate of soda has a less strong affinity for water. Hence it continues dry, when exposed to the atmosphere, and even gives up a part of its water of crystallization, the crystals losing their transparency and something of their weight. Hence, also, it requires a greater quantity of water for solution, than common carbonate of potash, water taking up only half its weight. The crystals, too, differ considerably in form and size from those of the former carbonate. The carbonate of soda is known in commerce by the names of barilla, fossil or mineral alcali, &c. j but as applied to the uses of the arts it is never met with pure. 51 CARBONATE OF AMMONIA? A. Ammonia, in its pure state, exists in the form of a gas, permanent over mercury only ; and carbonic acid has, also, the form of an aerial fluid. But when these two gasses are mixed together over mercury, in proper proportions, (viz. one mea- sure of carbonic acid to two or three of alcaline gas) they each quit the state of gas, and are entirely con- densed into a white solid body, termed carbonate of ammonia. B. Carbonate of ammonia retains, in a consider- able degree, the pungent smell of the pure volatile alcali. It is, also, unlike the other carbonates, volatilized by a very moderate heat; and evaporates, without entering previously into a liquid state. The vapour, that arises, may be again condensed, in a solid state; affording an example of sublima* Hon. This may be shown, by applying heat to the carbonate of ammonia in a retort, to which a receiver is adapted. The carbonate will rise, and be condensed in the receiver in the form of a white crust. C. This carbonate does not attract moisture from the air, but, on the contrary, loses weight. Its other properties resemble those of the carbonates of potash and soda. The mode of preparing it will be described hereafter. * COMBINATION OF CARBON WITH HYDROGEN, FORMING CARBONATED HYDROGENOUS GAS. i. When water is decomposed, by passing its vapour over red hot charcoal*, we obtain two different products. Carbonic acid is formed, in consequence of the union of the carbon with the * See Lavoisier's Elements, Chap. vi. E 2 52 oxygen of the water : and the hydrogen of the water, combining with another portion of carbon, constitutes the carbonated hydrogenous gas. The carbonic acid may be separated by agitating the produced gas in contact with lime and water, mixed together so as to be of the consistence of cream 5 and the carbonated hydrogen gas will remain pure. 2. This gas has the following qualities. A. It is 7iot absorbed by water* B. It is inflammable. This mny be shown by burning it in the manner directed in Art. VII, No. 3, B. The colour of the flame, however, may be observed to differ from that of hydrogen gas, inclining rather to a deep blue. C. When jired over mercury, carbonic acid gas and water are the products \ In burning pure hydro, gen gas, water only is generated 5 but in the com- bustion of this gas, two inflammable bodies are present, viz. hydrogen-and carbon. The production of carbonic acid may, also, be shown by burning the gas over lime water, by means of a bladder and bent pipe, as directed, page 28, A. The lime water will soon become milky. D. This gas is heavier than pure hydrogen gas, and even than common atmospheric air. Soap bubbles, blown with it, descend like the common ones ; and ajar filled with it, and held inverted a few minutes, exchanges its contents for common air. ART. XIII. SULPHUR SULPHURIC ACID * SULPHATES BINARY COMPOUNDS OF SUL- PlJUR, SULPHUR. l. Sulphur occurs in two different forms ; that of flowers and of stick sulphur. The former is gene- rally purest. 53 2. Sulphur is readily fused. A very gentle heat is sufficient to melt it; and, if very slowly cooled, it forms regular crystals. 3. Sulphur is volatilized by heat. A little sulphur may be put into the bottom of a tube, the mouth of which is loosely stopped with paper 1 , to prevent the free access of air. On applying heat, the sulphur will rise to the top of the tube. 4. Sulphur does not dissolve in water. 5. It is inflammable. In the open air, it burns with a blue flame, and emits a very penetrating smell. When burnt in a confined portion of com- mon air, an absorption takes place ; but the sul- phur is extinguished, before the whole of the oxygen is consumed. In oxygenous gas, it burns with a very beautiful and brilliant light ; and the absorption is more remarkable, but is still far from being com- plete. The product of both these combustions, is SULPHURIC ACID*. i . Though this is not the mode, in which sulphuric acid is ordinarily prepared , yet it will be proper for the chemical student to examine the result of this combustion, on account of the simplicity of the process. Let the glass bell, under which sulphur has been burnt, be rinced out with a little water. This water will have an acid taste 5 will turn vege- table blue colours red j and will effervesce with carbonated alkalis. It is, therefore, an acid, and, as it is composed of sulphur and oxygen, it is termed, the sulphuric acid. The properties of this acid must be exhibited by a portion of that usually found in the shops, or contained in the chest. They are as follows. * Much sulphureous acid is, also, generated in these pro- cesses. 54 A. Sulphuric acid has a thick and oily consistence as may be seen by pouring it from one vessel into another. B. It is nearly twice as heavy as water. This will appear from weighing a small vial filled with the acid $ and afterward filled with distilled water. C. In a pure state it is perfectly limpid and co- lourless. D. When mixed suddenly with water, considerable Tieai is produced. A diminution of bulk, also, ensues ; that is, one measure of acid and one of water do not occupy the space of two measures, but considerably less. Owing to the heat produced by its admixture with water, the dilution should be conducted very gradually -, and the acid should be added to the water by small portions at once, allowing each portion to cool, before a fresh addition is made. On the principle of its attraction for water, is to be explained, also, the rapid increase of weight, which the acid acquires, when exposed to air. E. A perfectly pure sulphuric acid remains quite limpid during dilution. The sulphuric acid, how- ever, commonly found in the shops, under the name of oil of vitriol, on admixture with water, deposits a white powder, in considerable quantity, consisting of various impurities. F. To purify sulphuric acid t it must be distilled in a glass retort, placed in the sand bed of a rever- be.atory furnace. This process is a very difficult one 5 and an inexperienced chemist should, there* fore, not attempt it. It may be less perfectly- purified, by diluting it with an equal weight of /water; allowing the impurities to settle 3 decanting the clear liquor ; and evaporating it, to the proper degree, in a glass vessel. 55 G. Sulphuric acid is decomposed at the temperature of the atmosphere, by infuuiiniable substances, and ac- quires a dark colour. The addition of a little brown sugar, or a drop of oil, to a. portion of the acid, imparts to it a brownish hue, which in time changes to black. Hence this acid should always be kept in bottles with glass stoppers; for a small bit of cork, if dropped into a considerable quantity, changes it in the manner that has been pointed oat. H. In high temperatures, sulphuric acid is still farther deccmpcse'd by combustible bodies. Into a glass retort put such a quantity of sulphuric acid, as will fill about one fourth part of it ; and add a small portion of powdered charcoal. On applying the heat of a lamp, gas will be produced very abundantly. Let this gas be conveyed, by a tube fixed to the mouth of a retort, and bent in the proper manner, into an inverted jar of water ; or, if it can be had, into an inverted jar of quicksilver in a mercurial apparatus. During this operation, the carbon attracts part of the oxygen of the sulphuric acid, and forms carbonic acid gas. But the sulphur is not entirely disoxygenated ; and a compound is, there- fore, formed of sulphur and oxygen, containing less oxygen than the sulphuric acid. This compound exists- in the state of a- gas, and its properties may next be examined. To avoid, however, the com- plication, whieh'the admixlureof carbdnic acid with this new product introduces into the experiments, it maybe proper to prepare : it in a mode-less objection- able, but the rationale of which cannot at present be explained. This consists, in dissolving one part by weight of quicksilver in two of sulphuric acid, and boiling the mass to 'dry ness. The dried mass, still remaining in the retort, is next to be distilled in a strong sand hjeat 3,.$ glass., globf being interpp$edt 4 56 between the retort and the receiving trough, to con- dense any sulphuric acid that may escape decompo- sition (see Lavoisier's 4th plate, fig. I, G.) The gas, thus obtained, is termed, conformably to the principles of the new nomenclature, SULPHUREOUS ACID GAS. Its properties are the following. A. Jt has a pungent and suffocating smel/, exactly resembling that which arises from burning sulphur, B. It is heavier than atmospherical air. C. It $}f tiiiguifh.es bur?iing bodies, and kills aniinah. D. // has the property of whitening or bleaching si//c. E. It is absorbed by water; but only in small proportion. F. This watery solution dees not redden infusion of litmus, as acids in general do, but totally destroys its colour. G. Sulphuric acid, saturated with this gas, (which may be effected by passing the gas through the acid) acquires tJie property q/ assuming a solid form, by a moderate reduction of its temperature. H. Sulphureous acid is, again converted to the state, of sulphuric y by restoring oxygen to it. To a portion of water saturated with this gas, add a little oxyd of manganese, a substance that contains much, oxygen loosely combined. The pungent smell of the water, and the other characteristics of sulphureous acid, will soon disappear. Both these aqids are susceptible of combination with alcalis. COMBINATION OF SULPHURIC ACID WITH ALKALIS. SULPHATE OF POTASH. This salC toy ttefdrmed by saturating the car* 57 bonate '-of potash with sulphuric acid, and crystal- lizing the solution. Its properties are the following. A. It crystallizes in small six-sided prisms, termi- nated by six- sided pyramids, with triangular faces. B. It has a biiter taste. C. // decrspitates, or crackles, when thrown on a red hot iron or on red hot coals, and is volatilized in a strong heat, D. Water, at 60 of Fahrenheit, takes up only one sixteenth of its weight ; but boiling water dissolves one fifth. E. 100 parts contain 30.21 acid, 64.61 alkali, and 5.18 water. G. This sulphate is decomposed, in high temperatures, by carbon. Mix any quantity of the salt with one fourth of its weight of charcoal finely powdered $ and expose the mixture, in a crucible, to a strong heat. The carbon will unite with the oxygen of the sulphuric acid, and will escape in the state of a gas. What remains is a compound, hereafter to be described, of sulphur and potash. SULPHATE OF SODA. A. This salt forms regular octahedral crystals, of a prismatic or cuneiform figure, the two terminating pyramids of which are truncated near their basis. B. It has a more bitter taste than the preceding, and melts more easily in the mouth. C. It swells upon a heated iron, in consequence of the loss of its water of crystallization, and a white powder is left. D. By exposure to the atmosphere, it effloresces and loses weight. E. It is very soluble iti water, 3 parts of which. 58 at 60 of temperature, dissolve one of the salt; and boiling water dissolves its own weight. F. It contains per cent, 14 acid, 22 alkali, and 64 water. G. It is decomposed by charcoal like the preced- ing salt, and a compound remains of sulphur and soda. SULPHATE OF AMMONIA. A. The sulphate of ammonia forms long flattened prisms with six sides, terminated by six-sided pyra- mids. B. It slightly attracts moisture from the air. C. It liquefies by a gentle heat, and is volatilized. If a stronger heat be applied, it is decomposed. See Mr. Hatchett's paper, in Phil. Trans. 1796, or Davy's Researches. D. The pure fixed alkalis, potash and soda, seize the sulphuric acid, and set at liberty the alkali. Hence a strong smell of ammonia arises, on the admixture of pure soda or potash with this salt. The combinations of sulphureous acid with alkalis have no peculiar qualities that are likely to prove interesting to the general student. Those, however, \vho may wish to pursue this subject, I refer to some interesting papers in the Annales de Chimie, vols. 2 and 24. BINAKY "COMPOUNDS OF SULPHUR jst. WITH 2rd. WITH HYDKOpEN. The combinations of sulphur with the two fixed alkalis, sodaand potash, are so similar in properties, tndt what is said of the one will equally apply to the other. 59 I. Sulphur may be united with these alcalis, either in the dry or humid way. To prepare a sulphuret, in the dry way, mix equal parts of sulphur and of carbonate of potash or soda, in a perfectly dry state $ and fuse the mixture in a crucible. T*he melted mass, when poured out, will have a reddish or liver colour. Or, a sulphuret may be formed by the decomposition of sulphates by charcoal, see preced- ing G. The process, in the moist way, consists in boiling together flowers of sulphur and a solution of pure potash or soda in a glass vessel. The sulphur is thus dissolved. - 2. Sulphurets of alcalis have the following qua- lities. A. In a moist state they emit an offensive smelly and have a disagreeable taste. B. They change to green the colour of 'violets , in the same manner as uncombined alkalis. C. They blacken the skin, silk, arid other animal substances. D. 'They are decomposed -by all acids. Into a Nooth's machine put a weak solution' of sulphuret of alcali, and pass through it streams of carbonic acid gas. In the course of a few days, the sulphur will be pre- cipitated, and a carbonate of alkali obtained. This decomposition ensues, instantly, on adding, to a solution of a sulphuret, any of the stronger acids,, as the sulphuric, nitric, or muriatic; and we obtain a compound of the alkali with the respective acid em- ployed. E. The liquid sulphurets absorb >, oxygenous gas. This may be shown by the experiments already described. (Art. VI.) If the change thus effected be examined, it will be found that the oxygen has combined with the sulphur, and formed sulphuric acid, which, uniting with the al&di, has composed the sulphate of potash. 60 F. If dilute muriatic acid be poured on the solu- tion of sulphuret of potash or soda, a violent effer* vescence will ensue, and a very offensive gas be dis- engaged. This gas may be collected over water. It is termed SULPHURATED HYDROGEN GAS. 1. This gas may be obtained in the foregoing manner; or from a mixture of three parts by weight of iron tilings and one of sulphur, previously melted together in a covered crucible. A portion of the fused mass may be put into a gas bottle, and diluted sulphuric or muriatic acid poured on it, which will extricate the sulphurated hydrogen gas. 2. Its properties are the following. A. Its smell is extremely offensive, resembling that of putrefied eggs. B. It is inflammable, and burns either silently or \vith an explosion, accordingly as it is previously mixed or not with oxygen gas or atmospheric air. During this combustion, water results from the tinion of the hydrogen with the oxygen, and sul- phuric and sulphureous acids from that of the oxygen and sulphur. C. It tarnishes silver t mercury, and other polished metals, and instantly blackens white paint. D. It is absorbed by water, which thus acquires the peculiar smell of the gas. It is this gas which gives to the Harrogate, and some other natural waters, their peculiar smell. E. Water saturated with this gas turns green the infusion of violets, in this respect producing the effect of an alcali. F. It is copiously absorbed by alcalis, which thus acquire colour, smell, and the property of diminish- ing oxygen gas. The compounds of this gas with 61 alcalls are termed hydro sulpliurets. Thus, the compound of this gas with potash is named hydro- sulphuret-of potash, and differs from the sulphuret of potash, in containing hydrogen besides sulphur. From these combinations, the gas is liberated by acids. ART. XIV. COMBINATION OF AZOTE WITH OXYGEN, CONSTITUTING NITRIC ACID- NITROUS GAS NITROUS OXYD AND COM- POUNDS OF NITRIC ACID WITH ALCALIS. 1. Tlie direct combination of azote and oxygen, affording a decisive synthetic proof of the nature of this acid, may be effected by passing the electric shock through a mixture of azotic and oxygen gasses. The circumstances of this experiment, however, cannot be understood without the aid of a plate, and of a very detailed description, for both of which I must refer to Mr. Cavendish's paper in the Phil. Trans, for 1785, &c. 2. The analysis of the acid may be obtained by driving it through a red hot porcelain tube, and receiving the generated gasses, which turn out to be a mixture of azotic and oxygenous gasses. "3. The nitric acid has the following properties. A. It is heavier than water > in the proportion of 1.5 to i. B. It is perfectly limpid and colourless. C. // gives a yellow stain to the akin. D. // produces heat when diluted with water, but by no means equal to that excited by diluting sulphuric acid. E. It becomes coloured by exposure to the surfs light, passing first to a straw colour, and then to a deep orange. This effect is produced by the union of the light of the sun with oxygen, in consequence f F 62 which the proportion of the acidifying principle to the azote is diminished. F. Tin's acid retains its oxygen with but Hi tie force. Hence it is decom posed l?y all combustible bodies, whi-cji are oxydated by it, with more or less rapidity in proportion to their affinity for oxygen. Charcoal decomposes it, and carbonic acid is formed; azotic gas being produced at the same time, if the propor- tion, and temperature, in which the experiment is made, be duly regulated. To effect the complete decomposition of nitric acid by charcoal, it may be driven over that substance made red hot in a porcelain tube. G. The acid is also decomposed by metals, as irorf, tin, zinc, copper, &:c. and with different pheno- mena, according to the affinity of each metal for . oxygen. This may be seen by pouring some strong nitric acid on iron filings or powdered tin. Violent heat, attended with red fumes, will be produced 5 and the metals will be oxydated. H. If the action of metals on nitric acid be more moderately conducted, a new product is obtained in a gaseous state. Dilute some nitric acid with twice its weight of water, and dissolve, in this, some turn- ings of copper, or a portion of quicksilver, applying heat if necessary. This must be done in a gas bottle, and the product received over water is NITROUS GAS. The properties of this gas are the following. A. It is permanent over tcater. "J}.' If 'hen well washed with water it is not acid. It will be found not to redden litmus paper, when introduced into it through water. C. // extinguishes flame, and is fatal to animals. D. When mixed li'ith oxygenous gas, redjnmes arise; keat is evolved $ and a diminution takes place ; and if the two gasses be in proper proportion and per- 63 fectly pure, they disappear entirely. Nitrous acid, at the same time, is regenerated. K. The same appearances ensue, less remarkably, with atmospheric air; and the diminution is only propoiv tionate to the qilantity of the oxygen gas, which it contains. Thus 100 measures of atmospheric air and 85 of nitrous tas, containing 13 per cent of azotic gas, are reduced, by admixture, to about 39; and deducting n measures for the azotic gas, contained in 8q measures of nitrous gas, we find that the air, under examination, contained 28 per cent of oxygen gas. On this principle, of its con- densing oxygenous but no other gas, is founded the application of nitrous gas to the purpose of eudio* iijt-try, or of ascertaining the purity ot air. The sources ' of'error/ however, in its employment in this mode, are such' as to forbid our relying implicitly on the results which it may afford, notwithstanding the improvements lately wade in its application by M. Humboldt, (.see Annales de Chim.ie, Vol. 2^, p! 123.) I prefer thesulphuret of potash as a more cer- tain test of the purity of air; and in this opinion I have the sanction of M. Berthollet, (see Ann. de Ch. VoK 34, p.. 73.) F. Trie generation of an acid, lj/ the admixture of tn'twns gas with common air or oxygen gat, may be shown ly the following experiment. Paste a slip of litmus paper within a glass jar, near the bottom ; and inro the jar, filled with and inverted in water, pass as .much nitrous gas, previously well washed, as will ,djsplace the water below the level of the paper. The colour of the litmus will remain unchanged ; but, on passing, up atmospheric air or oxygen gas, it will be immediately reddened. G. That the peculiar acid % thus produced* is the nitrous, will appear from the following experiment. Into a jar filled with, and inverted in. mercury, pass F % 64 a stroll quantity of a solution of pure potash ; and afterward, measures of oxygen and nitrous gasses, separately, and in proper' proportion. On removing the solution from the jar 5 exposing it, for some time, to the atmosphere j ani afterward evaporat- ing it, crystals of nitrate of potash will be formed, a salt which is ascertained to be formed of potash and nitrous acid, H. Nitrous gas is absorbed by nitric add, which, by this absorption, is considerably changed in its properties. Pass the gas, as it issues from the .ma- terials that afford it, through colourless nitric acid. The acid will undergo successive changes of colour, ti'l at last itwili become orange coloured and fuming. In this state it is called nitrous acid, because it con- tains a less proportion of oxygen than the colourless nitric. . . I. The nitrous gas, tints absorbed, is expelled- again, by a gentle heat, This may be shown by gently heating 'the acid coloured in expt. H, till it again becomes limpid. .In this experiment, light should be ex,- , eluded. .. . K. Nitrous gas is decomposed, by exposure to bodies .that hare a strong affinity Jer oxygen. Thus iron fil- ings decompose it, and become oxyded, affording a proof of the presence of oxygen in this gas. SuU phuret of potash, &c. have a similar effect. L. Nitrous gas is absorbed by the green sulphate and muriate oj iron *", which do not absorb azotic gas. To ascertain, therefore, how much azotic gas a given quantity of nitrous gas contains, let it be exposed in a graduated tube ove^ one of these solu- tions. This information is necessary, previously to deducing, from its effects on atmospheric air, the proportion of oxygen gas. * For an account of these salts, see Art. xxiv. we owe tp Dr. Milner, of Cambridge*. Into an earthen tube, about 20 inches long, and -J- Inch wide, opea at both ends, put as much coarsely powdered man- ganese, as is sufficient nearly to fill it. Let this be placed, horizontally, in a furnace, having two open- ings opposite to each other. To one end of the earthen tube adapt a retort, containing a strong so- lution in water of pure ammonia, and to the other a bent glass tube. Let a fire be kindled in the fur- nace; and when the manganese may be supposed to be reel hot, drive over it the vapour of the- ammonia. The alcali will be decomposed ; its hydrogen, unit- ing with part of the oxygen combined with the man- ganese, will form water; while its azote, uniting with another portion of the oxgen, will constitute nitrous gas. The gas, thus generated, may be col- lected by the usual apparatus. N. Another j act t showing the mutual relation of am- monia and oj' the compounds of azote, was discovered, seme years ago, by Mr. Wm. Higgins\, Moisten some powdered tin (which is sold under this name by the druggists) with strong nitricacidj and when the red fumes have ceased to arise, add some 7 quick- lime, or solution of pure potash. A strong smell of ammonia will be immediately produced. GASEOUS OXYD OF AZOTE NITROUS OXYD OP DAVY. i. This compound, also consisting of oxygen and azote, but in different proportions, may be obtained by several processes. * Phil. Trans. 1789. i See his Comparative View of the Phlogistic and Anti- phlogistic Theories, Z& edition, page 309, note. 66 A. By exposing common nitrous gas, for a few da,yp, to iron filings, or to various other bodies strongly attracting oxygen, this gas is changed into the gaseous oxyd. B. By dissolving zinc or tin in dilute nitric acid. But by neither of these processes, is the gas obtained sufficiently pure, for exhibiting itsqualities. To procure it in a state of purity, the following process is the best. C. To dilute nitric acid, add carbonate of am- monia, till the acid is saturated. Then evaporate the solution; and, to supply the waste of alcali, add occasionally a little more of the carbonate. Let the solution be evaporated, by a very gentle heat, to dry ness. The salt, thus obtaine J, is next' to be put into a glass retort, and distilled with a sand heat not exceeding 500 Faht.. The heat of an Argand's lamp is even sufficient. '1 he gas may be collected over water, and allowed to stand a few- hours, before it is used j during which time it will cleposite a white cloud, and will become perfectly transparent. The gas, thus obtained, was termed by the society of Dutch chemists, gaseous oxyd of azote, but for the sake of brevity, and as more conformable to the nomenclature of other compounds of azote, I shall use, with Mr. Davy, (he name of nitrous oxyd*. T his gas has the following properties. A. A ca?,dle burns in this gas with a brilliant flame and crackling noise. Before^ its extinction, the white inner flame becomes surrounded with an exterior blue one. B. Phosphorus introduced into it in a state qf in- flammation burns with increased splendor. * For a full account of this gas, consult Mr. Davy's Researches, Chemical and Philosophical. London. Johnson, 1800. 67 C. Sulphur, introduced into it when burning with a feeble blue flame is instantly extinguished. But when in a state of active inflammation, it burns with a vivid and beautiful rose coloured flame. D. Red hot charcoal burns in it more brilliantly than in the atmosphere. E. Iron wire burns in this gas with much the same appearances as in oxygenous gas. F. If is rapidly absorbed by water that has been previ- ously boiled, about 3 J o the original bulk of the //<> ontact with the air. This may be shewn by letting it escape into the air as it issues from the retort, when a very beautiful appearance will ensue. B- When mixed suddenly with oxygen gas, it de tonatcs.r-'fhit experiment should be made cau- tiously. C. The same phenomenon ensues on mixing it with oxygenated muriatic acid gas, or with nitrous (\xi,d. Phosphorus is also soluble in oils; and, when thus dissolved, forms what has been called liquid phos- phorus, which may be rubbed on the face and hands without injury It dissolves, too, in ether ; and a very beautiful experiment consists in pouring this phosphoric ether in small portions, and in a dark place, on the surface of hot water. The phosphoric matches consist of phosphorus calieroely dry, minutely divided, and perhaps a 81 little oxydated. The simplest mode of making them fs to put a little phosphorus, dried by blotting paper, into a small vial; heat the vial, and when the phosphorus is melted, turn it round, so that it may adhere to the sides. Cork the vial closely, and it is prepared. On putting a common sulphur match into the bottle, and stirring it about, the phosphorus will adhere to the match, and will take fire when brought out into the air. ART, XVI. BORACIC ACID AND ITS COMBINATIONS. The Boracic acid is very rarely found native, and is generally the result of chemical operations. Its properties are as follow. A. It subsists in a solid state. B. Unlike acids in general, it is not distinguished by a sour taste; yet it reddens vegetable blue co- lours, and effervesces with carbonated alcalis. C. It is very sparingly soluble in water. D. It is volatile, and capable of being sublimed. E. // dissolves in small proportion in alcohol^ and the solution burns with a beautiful green Jlame. F. // combines with alcalis. The most important of its combinations is that with soda, known com- monly by the name of bornx. From this it may be separated by adding sulphuric acid, which forms sulphate of soda, a salt much more soluble than the boracic acid, and therefore easily separable from it. G. The bar ate of soda contains an excess of alkali, and hence changes vegetable blue colours to green. On the application of a strong heat, it swells and loses its water of crystallization, and, on a further increase of heat, it melts into a glass* which is perfectly transparent when cold. 82 ART. XVII. EARTHS. LIME. 1 . //? ex/&vml qualities. These may be exhibited in common quicklime, such as is employed for the purpones of building or agriculture. In the same stale, also, it is sufficiently pure for demonstrating its chemical properties j but when used tor purposes of the latter kind, it should be fresh burnt from the kiln. 2. Relation of lime to wafer. A. Lime absorbs water very rapidly ; with con- siderable heat, and noise. This may be shewn by sprinkling a little water on some dry quicklime. The above mentioned phenomena will take place, and the lime will fall into powder. The degree of heat produced is even sufficient to set fire to soms inflammable bodies. When a sufficient quantity of water has been added to reduce lime into a thin paste, this is called milk or cream of lirne. B. Lime absorb* moisture from the atmosphere, and falls gradually into powder, as when slaked in the foregoing manner. C. Lime is very sparingly soluble in water, and when thus dissolved, forms what has been termed lime water. This solution tastes of lime j turns vegetable blues to green ; and unites with oil, form- ing an imperfect soap. To prepare the solution, lime is to be slnkecl to a thin paste, and a sufficient quantity of wiuer afterwards added. The mixture is to be stirred repeatedly ; the lime allowed to set- tle \ and the clear liquor decamed for use. 3. Relation qj lime to hijiamtnable substances. A. Lime unites with sultykur, both in the dry and humid ways. Mix powdered lime with half iis "weight of sulphur, and expose them to heat in a 83 covered crucible. The product will be a sulpburet of lime, which will be found to have the property of diminishing atmospheric air, and absorbing oxy- genous gas, like other compounds of the same kind. Or boil in a glass vessel, with a sufficient quantity of water, some powdered sulphur and powdered lime. The lime and sulphur will unite 5 and a liquid sulphuret of lime will be obtained. B Another interesting combination of lime is that which it forms with phosphorus, or the phos- phuret of lime discovered by Dr. Pearson. Take a glass tube about 12 inches long, and f of an inch diameter, sealed hermetically at one end. Let this tube be coated with clay, except within about half an inch of the sealed end. Put first into it a drachm or two of phosphorus,, cut into small pieces ; nnd then fill the tube with small bits of fresh burnt lime, of the size of split peas Stop the mouth of the tube loosely with a little paper, in order to prevent the free access of air. Next, heat to redness that part of the tube which is coated with clay, by means of some charcoal ; and, when the lime may be sup- posed to be red hot, apply heat to the part containing th phosphorus so as to sublime it, and to bring the vapour of it into contact with the heated lime. The lirne and phosphorus will unite, and will afford a compound of a reddish brown colour. This p'hos- phuret of lime has the remarkable property of decomposing water, ?\ the common temperature of the atmosphere. Drop a small piece of it into a wine glass of water, and in a short time bubbles of phosphorated hydrogen ga ignition even ensues, The combination of magnesia with sulphuric acid affords a neutral salt, termed sulphate of magnssies* This salt forms small crystals, which have a 6ool bitter taste, and dissolve readily in water. It is decomposed by pure and carbonated alkalis. If a solution of a pound of the salt, in a pound of boiling water, be mixed, suddenly, with a solution of ari equal quantity of carbonate of potash, in the same weight of water, a double decomposition ensues ; and the two fluids instantly form a thick solid coa- gulum. This, when well washed with boiling water, affords the carbonate of magnesia. The compounds of magnesia with other acids have no properties, that render it necessary to de- scribe them in this place. ALUMINE, OR AKGIXL. it Pure alumine may be obtained by precipitating a solution of alum in water, by the crystallized car- bonate of potash. To secure its complete purifica- tion from sulphuric acid, Guy ton advises, that -the precipitate be redissolved in nitric ac?d ; that ni r trate of barytes be cautiously added to the solution, till it no longer occasions milkiness j and that the alumine be afterwards precipitated, or separated from the nitric acid by heat. (Ann, de Chim. xxoui. 64). : ; 2 . Alum ine has the following qualities. 1 1 ad h e ijes to the tongue 5 when moistened with water* it forma H 3 90 a cohesive mass; and when Heated to redness^ ifc shrinks considerably in bulk, and becomes very hard. Jt dissolves slowly in all acids. The only combina- tion of importance, is that which it forms with the sulphuric acid. 3. With sulphuric add it affords sulphate of alumine 9 r alum. Sulphate of alumine is distinguished by the fol- ing characters. A. It has a sweetish astringent taste. B. It dissolves in water, 5 parts of which, at 60, take up one of the salt, but hot water dissolves it in greater abundance. C. This solution reddens vegetable blue colours ; which proves the acid to be in excess. D. When mixed with a solution of carbonate of potash, an effervescence is produced by the uncom- bined acid, which, also, prevents the first portions of alkali, that are added to a solution of sulphate ofalumrne, from occasioning any precipitate. E. On a further addition of alkali, the alumine is precipitated. F. Sulphate of alumine, when heated; swells- up j loses its regular form $ and becomes a dry spungy mass. G. It is decomposed by charcoal, which com- bines with the oxygen of the sulphuric acid, and leaves the sulphur attached to the alumine. A com- bination of alumine, sulphur, and charcoal form* the pyrophorus o/Homberg. To prepare this, equal parts of powdered alum and brown sugar are melted over the fire, and are kept stirring, till reduced to dryness. The mixture is then to be finely pow- dered, and introduced into a common vial, coated with clay, to which a glass tube, open at each end, is Juted, to allow the escape of the gasses that are pro- duced. The vial must then be set in the fire, sur- 4 91 rounded by saiul, in a crucible. Gas will issue from the open end of the tube, and may be inflamed by a lighted paper. When this ceases to escape, the crucible may be removed from the fire j and a little moist clay pressed down upon the open end of the tube, to prevent the access of air to the contents of the vial. The pyrophorus thus formed, is a black and very light powder, which instantly takes fire, when poured out of the bottle into the air ; arid inflames suddenly in oxygenous gas. SILEX. 1. Siliceous earth, or silex, may be obtained, tolerably pure, from flints, by the following process. Procure some common gun-flints, and calcine them in a crucible, in a red heat. By this treatment, they will become brittle, and easily reducible to powder. Mix them, when pulverized, with three or four times their weight of carbonate of potash, and let the mixture be fused, in a strong red heat, in a crucible. We shall thus obtain a compound of alkali and siliceous earth. Dissolve this in water ^ filtre the solution 5 and add to it diluted sulphuric or muri- atic acid. An immediate precipitation will ensue j and, as long as this continues, add fresh portions of acid. Let the precipitate subside ; pour off the liquor that floats above it ; and wash the sediment with hot water, till it comes off tasteless. Then dry it. 2. Siliceous earth, as thus obtained, has the following qualities. A. It is perfectly white and tasteless. B. When mixed with water, it does not form a cohesive mass like alumine 5 and has a dry and harsh feel to the fingers. 92 C. It is not acted on by any acid, except the fluoric. D. When prepared in the foregoing manner, and very minutely divided, silex is soluble in a so- lution of pure potash. In the aggregated state of flints, however, k is perfectly insoluble in this way, an excellent illustration of the principle laid down, Art. 1. No. 3. E. When mixed with an equal weight of carbo- nate of potash, and exposed to a strong heat in a furnace, it forms a glass, insoluble in water, and identical, in all its properties, with the glass com- monly manufactured. It is owing to the siliceous earth, which it contains, that glass is decomposed by the fluoric acid. Glass, however, has occasionally other ingredients, besides the two that have been mentioned. F. With a Lm-er proportion of alkali, as three or four parts to one of silex, this earth affords a com- pound called by Dr. Black, silic&ted alkali. This compound is soluble in water; and affords a good example of the total change of the properties of bodies by chemical union ; for in a separate state, no substance whatever is more difficult of solution trun silex. The solr.tion of silicated alkali was formerly, termed liquor siluum, or liquor of Jiints. Acids, seize the alkaK, and precipitate the siiex> which is even separated, by mere exposure to the atmosphere, in consequence of the absorption of carbonic acid, by the alcalL BARYTES. 1. Barytes, in a pure form, has a sharp, caustic taste; changes vegetable blues to green ; and serves as the intermedium between oil and water. 2, It is readily dissolved by boiling watery and 93 the solution, on cooling, shoots into regular crystals, which have the form of flattened hexagonal prisms, having two broad sides, with two intervening nar- row ones, and terminated at each end by a quadran- gular pyramid. 3. These crystals are so soluble, as to be taken up, when heated, merely by their own water of crystallization. When exposed to a stronger heat, they swell and foam, and leave a dry white powder. At 60, an ounce of water dissolves only 25 grains of the crystals. 4, Pure barytes has a very strong affinity for carbonic acid. A. Let a solution of pure barytes be exposed to the air. It will soon acquire a pellicle, like lime water, because barytes, when saturated with car- bonic acid, is rendered insoluble. B. Blow, by means of a quill or glass tube, the air from the lungs, through a solution of pure ba- rytes. It will instantly become milky. C. With a solution of pure barytes, mix a little water impregnated with fixed air. The barytic solution will be immediately precipitated. D. Barytes, combined with carbonic acid, is termed carbonate of barytes. If this combination be found in the earth, it is termed native carbonate of barytes ; if formed by chemical processes, arti- ficial carbonate. E The carbonateof barytes is tasteless ; inso'uble in water ; and does not change vegetable blues. F. Carbonate of barytes is decomposed by exr posure to an intense heat. Its carbonic acid is separated, and we obtain the earth in a pure form, as described, No. I. G. Carbonate gf barytes is decomposed by the stronger acids, as the sulphuric, nitric, and muriatic* The two last afford salts, that dissolve readily in wtHcr, 94 . With sulphuric acid, barytes forms the sulphate of barytes. A. To a solution of pure barytes, add sulphuric acid. A white precipitate will appear, which is the sulphate of barytes. B. The same compound is formed by adding sul- phuric acid to carbonate of barytes ; or to a solution of muriate or nitrate of barytes. C. The sulphate of barytes is one of the most insoluble substances that chemistry presents, requir- ing, for solution, 43000 times its weight of water. D. Barytes has a stronger affinity than any other body, for sulphuric acid. E. Owing to these properties, the solution of pure barytes, and of the nitrate and muriate of barytes, are excellent and very sensible tests of sul- phuric acid, and of all its combinations. Let a single drop of sulphuric acid fall into a wine quart of pure disjU led waier. On adding' a few drops of one ot thr foregoing solutions of barytes, a precipitation will ensue. F. Sulphate of barytes is decomposed by carbonate of potash. Boil the powdered sulphate, with a solution of twice or three times its weight of car- bonate of potash. The carbonic acid will pass ta the barytes, and the sulphuric to the potash. STRONTITES.* I. Strontites, in a state of purity, has a caustic taste j changes vegetable blues to green j and unites oil with water. * I use this name aftjr Dr. Hope, who first established the peculiar nature of tins earth (though before suggested by Dr. Crawforr) j and who discovered its veiy interesting properties in a state of purity, as well as those of barytes. (See his memoir in the fourth vol. of Edmburgh Transactions.) 95 a. It dissolves very readily in boiling water; and the solution, on cooling, shoots into regular crystals. These are thin quadrangular plates, sometimes square, oftener parallelograms $ not exceeding in length, and not equalling in breadth, a quarter of an inch.. Of these crystals, one ounce of water at 6o tt takes up only 25 grains. When exposed to heat they undergo the same changes as those of barytes. 3. Pure strontites strongly attracts carbonic acid. This may be shown by experiments similar to those on barytes. Indeed the properties of this earth are so similar to those of barytes, that every thing, which has been said of the latter, will apply to strontites. 4. The characteristic distinctions, between the two earths, are derived from the different forms of crystals, and different solubility, of the salts, afforded by their union with the same acid. The salts, with base of strontites, are always much more soluble than barytic salts. The salts of strontites have, also, the singular property, when dissolved in alcohol, of tinging its flame a deep blood red colour. The remaining earths I omit 5 because they very seldom occur, and are noi likely to become the sub. jects of experiments to the chemical student. They may be found enumerated and described, in Mr. Par- kinson's Chemical Pocket Book. ART. XVIII. METALS IN GENERAL. The most interesting quality, general to all the metals, is their relation to oxygen. . 1. Some metals are oxydated merely by exposure to atmospherical air, at the. ordinary temperature. Such ace arsenic and manganese. 2. Other metals are oxydated by exposure to air; but not without a considerable increase of their 96 temperature. Iron, zinc, copper, tin, &:c for ex- ample, when made red hot, lose their metallic bril- liancy -, and are converted into oxyds of different co- lours. 3. Other metals are not oxydated, even by the combined operation of air and of an increased tem- perature; such are gold and platina. 4. But even these metals (and all others more readily) are oxydated by acids. Thus the nitro- muriatic and oxygenated muriatic acids first oxydate gold, and then dissolve the oxyd. Iron is oxydated by dilute sulphuric acid, the metal attracting oxygen from the water; and the oxyd of iron, thus produced, is dissolved by the acid. 5. All metals, that are oxydated by air, undergo the same change, much more readily, in oxygenous gas. 6. Some metals are oxydated by water, both at the ordinary temperature of the air, and in high temperatures. Thus iron filings, moistened with water, become oxyded, in consequence of its de- composition; and the vapour of water, passed over red hot iron, is rapidly decomposed, and the iron gains 28 per cent of oxygen. Other metals, as gold, silver, &c. are not oxyded by water, in any tempe- rature. 7. All metals, in consequence of oxydation, ac- quire weight. This may be shown, by keeping a given weight of iron-wire red hot, for sometime, in the bowl of a common tobacco-pipe; taking care that dust or ashes do not fall into it. 8. Metals retain oxygen with different degrees of force. Some oxyds, (that of mercury for instance) are reduced to a metallic state by heat only ; but others (as that of iron) require the addition f some substance, that attracts oxygen more strongly than 97 the metal retains it. Tims, to reduce the. oxyd of iron, charcoal must be added. 9. Metals are precipitated from acids, by each other, not in the form of oxyds, as they are separated by alkalis, but in a metallic form. Thus when a polished plate of iron is immersed in a solution of sulphate of copper, the copper appears, on the sur- face of the iron, in the state of a metallic coating. In thft case, the iron attracts the oxygen from the copper 5 and, as no metal is soluble in an acid, unless when combined with oxygen, the copper is precipi- tated. ART. XIX. GOLD. 1. Gold may be melted, by a moderate red heat. 2. Pure gold is not oxyded by exposure to heat, with the access of air. 3. It is not acted on, by sulphuric, nitric, or mu- riatic acid, even at the boiling temperature. 4. It is dissolved, however, by nitro-muriatic acid, and also by the oxygenated muriatic acid. A thin sheet of gold introduced into the latter acid, when hi a gaseous state, takes fire and burns. 5. The nitro-muriate of gold gives a purple stain to the skin, and is susceptible of crystallization, 6. It is decomposed by alkalis. A solution of pure ammonia separates an oxyd of gold ; and a por- tion of ammonia, uniting with the oxyd, forms a compound, which detonates very loudly in a gentle heat, and is termed fulminating gold. It may be exploded by laying a little on a shovel, and applying a very gentle heat over a fire. 7. The solution of gold is, also, decomposed, by certain combustible bodies, which attract the oxygen from the gold and render it insoluble. (A) Into a 98 dilute solution of gold*, contained in a glass jar, put a long narrow slip of cKarcoa'l, and expose the whole to the direct light of the sun. The gold will be revived, and will appear on the charcoal in a metallic state, exhibiting a very beautiful appearance. The same change ensues without light, if the solution be exposed to a temperature of 212. B Moisten a piece of white taffeta ribband, with the dilute solution of gold, and expose it to a current of hydrogen gas from iron filings and dilute sulphu- ric acid. The gold will be'reduced, a'nd the ribb.ind will be gilt with the metal. By means of a camel's hair pencil, the gold may be so applied as to exhibit regular figures, when reduced. C. The same experiment may be repeated, sub- stituting phosphorated fiydrogen for common hydro- gen g?s. Th's reader who wishes for a detail of va- rious experiments of a similar kind, may consult ah ffssay on Combustion, by Mrs. Fulhanie, published by Johnson, London, 17945 and also Count Rum- ford's paper, in the Phil Tra'ns 1798, p. 449. 8. When a sheet of tin is immersed in a solution of nit ro- muriate of gold, the oxyd of gold is precipi- tated of a purple, colour, and u 'hen scraped off aiid collected forms the purple powder of Cassius, much employed in enamelling. The same precipitate is obtained by mixing a so'iuiion of gold with a solution of tin in muriatic acid. 9 Gold is precipitated frdm its solvent by ether; but the oxyd of gold is instantly redissolved by the emerj and forms the ethereal Solution of gold. 10. Sulp'hurets of alkalis unite with gold both in the dry and humid way. To exhibit tins, sortie leaf * The nitro-ir.uri;tte of gold, employed in these experiments, shoul'd be previously evaporated to dry ness, in order t j expel the superfluous acid, and afterward dissolved in distilled water. 99 gold may be digested, with heat, in a solution of sulphuret of potash. ART. XX. PL ATI N A. 1. Platina is a white metal, resembling silver in colour, but greatly exceeding it, and indeed all other metals, in specific gravity. 2. It is. ot all metals, the most difficult of fusion. It may be melted, however, by a blow pipe, with the aid of oxygenous g:is. 3. It is noi oxyded when exposed, red hot, to the air, for a considerable length of time. 4. Jt dissolves in no acid, except the nitro- muriatic and oxygenated muriatic acids. 5. These solutions are decomposed by alkalis and, also, by a solution of muriate of ammonia, which last has noefiecton solutions of gold. ART. XXI. SILVER. 1. Silver, alfo, is a metal, which is difficultly oxyded by the concurrence of heat and air. 2. It is acted on by sulphuric acid, which when a. (lifted by heat, oxydates, and partly dissolves it. 3. Nitric acid dissolves it with a disengagement of nitrous gas; and the solution, when evaporated, shoots into legulnr crystals . If the silver be pure, the solution is colourless, otherwise it has a green hue. 4. Muriatic acid does not a6t on silver. Yet this acid takes silver from others. ' Thu, when muriatic acid is added to nitrate of silver, a while curdy precipitate falls down, in great abundance. This precipitate is decomposed by light ; for when ex- posed to th-j direct rays or the sun, its colour become^ gradually darker. If fused by a gentle 100 heat, it forms a femi transparent mass of the consist- ence of horn, called luna cornea, or horn silver, 5. A solution of nitrate of silver stains animal substances a deep black. Hence it has been applied to the staining of human hair; but when thus em- ployed, it should be very much diluted, and used with great caution, on account of its corrosive quality. 6. The solution ot nitrate of silver, when evapo- rated, forms regular crystals. These crystals fuse, uhen heated; and being poured, in this state, into moulds, form the common lunar caustic. 7. Nitrate of silver is decomposed by other metnls. Thus the surface of a plate of copper, to which a little of the solution is applied, becomes plated over with silver. If a little mercury be poured inton bottle filled with this solution, and the bettlebe left some time undisturbed, the silver is precipitated in a beautiful form, refembling the branches ef a tree, and which has been termed Arbor Diana. (See Nicholson's Chemistry, page 249.) 8. Precipitate nitrate of silver by lime water; and wash and dry the precipitate. Let this be afterward put into a vessel of liquid ammonia. It will then assume the form of a black powder, from -which the fluid is to be decanted, and the black substance left to dry in the air. This is the cele- brated compound termed fulminating silver, which detonates with the gentlest heat, and even with the slightest friction. When once prepared, no attempt must be made to enclose it in a bottle; and it must be left undisturbed, in the vessel in which it was dried. Great caution is necessary in the prepara- tion of this substance, and in making experiments on it. It even explodes/ when moist, on the gentlest friction, J01 9. Silver is acted on by sulphurets of ale alls, and by sulphurated hydrogen gas. Both these substances Blacken sijver, when exposed to their operation ; and the common tarnishing of silver has been. traced .to, a similar cause. ART X^II. MERCURY. ',i. .Mercury, or quicksilver, is the only one of the .paetals, that retains a -fluid form, at the ordinary temperature of the atmosphere. ; 2 When its temperature is reduced to about 40 below zero of Faht, it assumes a folid form. This is a degree of cold, however, that only occurs in high northern latitudes : and in this country quick- silver can only be exhibited in a solid state by means of artificial mixtures. Seepage 87. 3. At about 6oo J of Faht., mercury boils, and is changed into vapour. Hence it may be driven over by distillation, and may thus be purified, though not accurately, from the admixture of other -metals. 4. Mercury is not oxydated, when pure, at the ordinary temperature of the atmosphere ; but when boiled for a considerable time, in a glass vessel, wi_ili a long narrow neck, it is converted into a reddish .brown gxyd. <;. Mercury is dissolved by Jiot sulphuric acid, ,and forms a white salt. When this is washed with ^boiling water, a yellow substance is obtained called . turbuh rnineral. 6. Mercury is dissolved by nitric acid, and nitrous gas is disengaged. The properties of the solution vary, accordingly as it is made with or with- put heat, the mercury, in the former case, being more highly charged with oxygen. When the nitrate of mercury is evaporated to dryndss, and made very 102 hot, it is changed into a bright red oxyd, which still contains a small portion of acid. 7. Mercury is the basis of a new fulminating com- pound, lately discovered by Mr. E. Howard. To pre- pare this powder, 100 grains (or a greater propor- tional quantity not exceeding 500) are to be dissolved, with heat, in a meafured ounce and half of nitric acid. The solution, being poured cold upon two measured ounces of alcohol, previously introduced into any convenient glass vessel, a mo- derate heat is to be applied, till effervescence is excited. A white fume then begins to undulate on the furface of the liquor 5 and the powder will be gradually precipitated, on the cessation of action and reaction. The precipitate is to be immediately collected on a filtre ; well washed with distilled water; and cautiously dried in a heat, not exceed' ing that of a water bath. The immediate washing of the powder is material, because it is liable to the reaction of the nitric acid ; and while any of that acid adheres to it, it is very subject to the action of light. From 100 grains of mercury, about izo or 130 of the powder are obtained. (See Phil. Trans. 1800, p. 214.) This powder has the pro- perty of detonating loudly in a gentle heat, or by light friction. 8. Mercury is not dissolved by muriatic acid ; but may be brought into union with this acid, by' double elective affinity. Thus when sulphate of mercury and muriate of soda, both well dried, are mixed and exposed to heat, we obtain a combina- tion of oxyd of mercury and muriatic acid. This compound is the corrosive sublimate of the shops. r l he same components, with a still further addition of mercury, constitute an insoluble substance called calm net. 103 9. The oxyds of mercury are all reduced by heat alone, without the addition of any combustible substance, and afford oxygenous gas. 10. Mercury dissolves gold, silver, tin, and many other metals ; and if these be combined with it, in sufficient quantity, the mercury loses its fluidity, and forms an amalgam. A solid amalgam of lead, and another of bismuth, on admixture together, have the singular property of instantly becoming fluid. ART. XXIII. IRON. 1. Iron is oxyded by the action of air, with the aid of an increased temperature, and gains about 28 per cent. The oxyd, thus obtained, is black. 2. It is oxyded also by water, both at the ordinary temperature of the air, and in a high temperature. Iron tilings, moistened with water, acquire rust and become oxyded j and the vapour of water gives up its oxygen to red hot iron, the hydrogen being- liberated in an uncombined state, see p. 29. 3. Iron is attacked by most acids. The sulphuric acid, when concentrated, acts but feebly on iron, without the assistance of heat. But when diluted, the iron is first oxyded by the decomposition of the water, and this oxyd is dissolved by the acid. The solution, when evaporated, gives the sulphate of iron, which has the following properties. A. It forms regular-shaped crystals, of a green colour, which have an astringent tafte, and dissolve readily in water. B. From this combination, an oxyd of iron is thrown down by alcalis and by earths, varying in colour, with the kind and ftate of the precipitant. C. When the iron, contained in this salt, is still farther oxyded, the colour of the sslt changes to red ; and, if the oxydation be carried still farther, 104 the iron becomes insoluble in sulphuric acid, affording an example of a metal soluble only when oxyded to a certain degree. Mere exposure to air is sufficient to precipitate an oxyd of iron ; and the effect is rapidly produced, by adding a little oxygenated rnuriate of potash to a solution of ; the tail. The different states of oxydntion of iron, when, combined with sulphuric and other acids, ha/ve been discovered, by M. Proust, to be the foun- dation of essential differences in the characters of these salts. According- to this ingenious chemist, there exist two varieties, of sulphale of iron, r the green and .the red. In the green sulphate, the iron contains 27 per cent of oxygen; in (he red 4$. The green salt, when pure, is, soluble jn alcohol; its solution is of a pale green colour ; it is not altered by the gallic acid; . and gives ,a white preci- pitate with prussiate of potash. The red sulphate is soluble in alcohol, and uncrystallizable ; it .forms a black precipitate wijth jthe gallic acid, and a blue one with prussiates. The ^veen sulphate may .be changed into the red by long exposure to , the air 5 by oxygenated muriatic acid; or by nitric acid. The red sulphate may be changed into tfce green one, by agitation in contact with sulphurated hy- drogen gas. f \ he common sulphate of iron is .a mixture of these two, in various proportions. .(See Ann. de Chimie, vol. 23.) D. The sulphate of iron is decomposed by heat alone. When distilled in an earthen retort, the sulphuric acid passes over, and an oxyd of iron remains in the retort. 4. Iron is acted on by the muriatic and nitric acids, and by the last, when concen.trated, very violently, so that the acid undergoes a complete . decomposition. The compounds, .thus obtained do 105 not admit of being crystallized, and, like the sul- phate of iron, exist in two different states, the green and the red, which vary according to the degree of oxydation of the iron. (Davy, 186). 5. Iron may be united, in the way of double elective aiiinity, with the prussic acid*. Thus when pru.ssiate of potash, and sulphate of iron, both in solution, are mixed together, the prussic acid and oxyd of iron quit their former combinations, and unite together. The beautiful blue precipitate is prussiafe of iron. A. Prussiate of iron is nearly insoluble in water. B. It is not soluble in acids. C. It is decomposed by a red heat ; the prussic acid being destroyed, and an oxyd of iron remain- ing. , D. It is decomposed by pure alcalis and earths, which abstract the prussic acid, and leave an oxyd of iron. Thus, when pure potash is digested with prussiate of iron, its beautiful blue >l cqlour disap- pears ; and we obtain a compound of potash and prussic acid, or a prussiate of potash. E. When the prussiate of potashes mixed with sulphate of iron, in which the m6taUis t as little oxyded as possible, the prussiate of 'irpn, that is formed, is of a white colour ; but gradually becomes blue, as the iron, by Exposure to air, acquires more oxygen. (See Proust's Memoir, in 'Nicholson'^ Journal.) F. The effect of a sympathetic ink may be ob- tained, by writing with a pen dipped in prussiate of potash. No characters will appear, till die paper is moistened with sulphate of iron, when letters of a prussiaa blue colour will be apparent. The experi- ment may be reversed, by writing with sulphate of * This acid will be mentioned hercafterl 106 Iron, and rendering the characters legible by prus- siate of potash. 6. "When sulphate of iron is mixed with an infu- sion of galls, we obtain a black solu.iion, which is a new combination of oxyd of iron, with the gallic acid. This compound is the basis of inks, the other ingredients of which are chiefly added with the view of keeping this suspended. A. Write upon paper with an infusion of galls. The characters will not be legible, till a solution of sulphate of iron is applied. This experiment may be reversed like the preceding one, No. 5, F. B. The combination of iron, forming ink, is destroyed by pure and carbonated alkalis. Apply a solution of alcali to characters written with common ink. I he blackness will disappear, and the characters will become brown, an ox)d of iron only remaining on the paper. C Characters, which have been thus defaced, may again be rendered leg ble by an infusion of galls. D Ink is decomposed 'by most acids ; w!,ich feparate the oxyd of iron from the gallic acid, in consequence of a stronger affinity, Hence, ink stains are removed by dilute muriatic acid, and by fome vegetable acids. Hence, also, if to a satu- rates! solution of sulphate of iron, there be added an excess of acid, the precipitate no longer appears on adding infusion of galls E. Ink is decomposed by age, partly in conse- jjuence of the further oxydation of the iron, and partly, perhaps, in consequence of the decay, or escape, of (lie acid of galls. Hence .ink-stains degenerate into ironmoujds ; and these last are .immediately produced, on an inked spot of linen, When washed with soap, becap.se Uie alkali of the 107 soap abstracts the gallic acid, and leaves only ah oxyd of iron. F. Ink is decomposed by oxygenated muriatic acid, which destroys the gallic acid, and the re- sulting muriatic acid dissolves the oxyd of iron. 7. Iron is dissolved by water impregnated with carbonic acid. A few iron filings when added to a bottle of aerated water, and occasionally shaken up, impregnate the water with this metal. The solu- tion is decomposed by boiling, and in a less degree by exposure to air. 8. Iron combines with sulphur. (A) A paste of iron filings, sulphur, and water, if in surrlcient quantity, will burst into rlatne. (B) A mixture of one part of iron filings, and three parts of sulphur, accurately mixed, and melted in a glass tube, at the moment of union, exhibit a brilliant combustion. (C) This sulphuret of iron, when moistened, ra- pidly decomposes oxygenous gas (D) When di- luted sulphuric or muriatic acid is poured on it, we obtain sulphurated hydrogen gas. ART. XXIV. COPPER. 1. Copper is oxydated by air. This may bft Shown by heating ohe end of a polished bar of copper, which will exhibit various shades of colollr* according to the force of the heat. 2. Copper does not decompose water, even with the assistance of hekt. 3. It combines with strong sulphuric acid, ift fc boiling hent, and affords a blue salt called sulphate Of copper. (A) Sulphate of copper is a regularly crystallized salt, tiisily dissolved by \vater. (B) The solution is decomposed by pure and carbonated alkalis. The former however redissolve the preci- pitate. Thlis, dh adding pure H^iid ammonia to a 103 solution of sulphate of copper, a precipitate appears, which, on a farther addition of the alkali, is redis- solved, and affords a beautiful bright blue solution. (C) The sulphate of copper is decomposed by iron. In a solution of this salt immerse a polished plate of iron. The iron will soon acquire a covering of : copper in a metallic state. 4. Copper dissolves readily in nitric acid, with a disengagement of nitrous gas. The salt, resulting from this combination, has the singular property of detonating with tin. See page 5, D. . 5. Copper is soluble in muriatic acid, with the aid of heat. 6. When corroded by vinegar, it forms verdi- grise. 7. Copper combines with sulphur. A mixture of three parts of copper filings, and one part of sulphur, when melted in a glass tube, exhibits a combustion, more brilliant than that of iron and sulphur. ART. XXV. LEAD. I. Lead, when melted, and exposed to the action of the air, becomes covered with a pellicle of oxyd. By long continued exposure to heat, it is converted into oxyds of different colours. This oxydation it is difficult to exhibit on a small scale. The oxyds of Jead may, therefore, be examined, as they are found in the shops, in the states of minium or red lead \ massicot; and litharge. a. The oxyds of lead give up their oxygen, on the application of heat. When distilled in an -earthen retort, they afford oxygenous gas ; and still more readily, when distilled with the sulphuric acid. 3.. Of all the acids, the nitric acts most strongly 109 on lead, nitrous gas being disengaged during the solution. 4. The muriatic and sulphuric acids decompose nitrate of lead, and form a difficultly soluble muriate and sulphate. $. The oxyds of lead decompose muriate of soda. Mix two parts of finely powdered red lead with one of common salt ; and form the two into a paste \vith water, adding more occasionally, as the mix- ture becomes dry. The alcali will be disengaged, and the muriatic acid will unite with the oxyd of lead. Wash off the alcali j dry the white mass ; and fuse it in a crucible. It will form the pigment, called mineral or patent yellow. 6. Lead, when exposed to the vapour of vinegar, is slowly corroded into a white oxyd, or rather car- bonate. This, when dissolved in distilled vinegar, and crystallized, forms acetite of lead, or sugar of lead. This acetite of lead, and indeed all the solu- ble salts of lead, are decomposed by sulphurated hy- drogen gas. Hence characters, written with acetite of lead, become legible on exposure to sulphurated hydrogen gas. ART. XXVI. TIN. The properties of tin must be examined in the state of block tin 5 what is commonly known by the name ofnin, being nothing more than iron plates, with a thin covering of this metal. 1. Tin melts on the application of a moderate heat; by a long continuance of which, it is con- verted into a grey powder. This powder, when mixed with pure glass, forms a white enamel. 2. Tin is not oxyded by exposure to air with the concurrence of moisture, a property which is the foundation of its use in covering iron. K 110 3< Tin is dissolved by all the three mineral acids. 4. Tin may be brought to combine with the oxygenated muriatic acid by first forming it into amalgam with mercury; triturating this with an equal weight of oxygenated muriate of mercury j and distilling the mixture. The result is a liquid which emits dense white fumes, when exposed to the air, and was formerly termed the fuming liquor of Li- bavius. 5. Solutions of tin have the property of precipi- tating the colouring matter of vegetables, a property \\hich will be noticed hereafter. ART. XXVII. ZINC. 1. Zinc is melted by a very gentle heat. 2. It is rapidly oxycled by atmospherical air. \Vhen thrown into a red hot crucible, it burns with a bright light, and a white oxyd sublimes. 3. It dissolves readily in all the mineral acids. With diluted sulphuric acid, it affords the purest hydrogen gas, that can be obtained. The salt, when evaporated, shoots into regular crystals, called sul- phate of zinc. 4. It detonates, when mixed with powdered nitre, and projected into a red hot crucible. ART. XXVIII. BIfeMUTH. 1. The proper solvent for bismuth is the nitric acid. 2. From this solution, a white oxyd is precipitated by the mere addition of water. This, when well washed, is the pigment called flake white. 3. This oxyd of bismuth is blackened by sulphu- rated hydrogen gas. 4. Bismuth forms a component of the fusible mix- 5 ture of-metals, discovered by Sir Isaac Newton. Melt Ill together in a crucible eight parts of bismuth, five of lead, and three of tin 3 or three of bismuth., one of lead, and five of tin. The result is a compound, which will be found to melt in a heat less than that of boiling water, and which will even fuse, under the surface of hot water. ART, XXIX. ARSENIC. I. Arsenic, as it is to be found in the shops, oc- curs in the state of a white oxyd, from which the metal may be obtained by the following process, ivlix two parts of the white oxyd with one part of black flux*, and put them into a crucible. Invert, over this, another crucible ; lute the two together, \vith a little clny and sand'; and apply a red heat to the lower one. The ;rscmc will he reduced, and will b^ found lining the inside of the upper crucible, in a form of metallic brilliancy. z'. Arsenic is oxyded by mere exposure to the air. It soon, becomes tarnished, and loses hs metallic lustre. 3. It is volatile. When laid on a heated iron, it evaporates in the form of a white smoke, and emits a strong smell of garlic. 4. It is acted on by all acids, 5. It gives a white stain to copper. Let a little of the metallic arsenic be put between two small plates of copper; bind these closely together, by i on-wire; and ! eat them in a fire The inside of the copper plates will be stained white by the arse- nic. 6. The white oxyd of arsenic is soluble in water, which dissolves about $ of its weight. * Black flax is formed by detonating, in a crucible, enc r?.rt of nitre with iwq of cream oi tartar. K * 112 7. The oxyd is soluble in most acids. 8. The oxyd of arsenic, by repeated distillation with nitric acid to dryness, is converted into an acid, tei med arsemac acid, or acid of arsenic \ and also by oxygenated muriatic acid. 9. The oxyd of arsenic, when mixed with pow- dered nitre, and detonated in a red hot crucible, affords a salt consisting of arseniac acid and potash, and termed arseniute of potash. jo. Oxyd of arsenic combines with fixed alkalis, both in the dry and humid ways. 11. It is decomposed, when distilled with sul- phur, sulphureous acid being disengaged, and a bright red compound of arsenic and sulphur re- maining, termed realgar. When water, saturated with sulphurated hydrogen gas, is added to the so- lution of arsenic No. 6, a yellow precipitate is pro- duced. 12. A beautiful green colour, termed, from its. inventor, Scheele's green, is obtained by adding a solution of oxyd of arsenic in alkali to a solution of sulphate of copper. (See Scheele's Chemical Essays.) ART. xxx, A.NTIMONY. j. Antimony, as it is found in the shops, is a compound of the metal with sulphur. From this, the metal may be obtained by first roasting off the sulphur, and then fusing the oxyd with black flux. 2. Metallic antimony is of a silvery white colour > very brittle j and of a plated or scaly texture. 3. Antimony is easily fused, and when the fire is strongly urged, the antimony, if in a close vessel, may be volatilized. 4. Jt is oxydecl by the concurrent action of heat and air. 5. Antimony is soluble in all acids. When the 113 regulus is pulverized and distilled with twice its weight of oxygenated muriate of mercury, a com- pound comes over, into the receiver, of oxygenated muriatic acid and antimony, formerly termed, from its thick consistence, butter of antimony. From, this, a white oxyd of antimony is precipitated by the mere affusion of water, which was formerly called Algaroth's powder. This powder, by solution in the acidulous tartiite of potash, affords a tartar emetic of certain efficacy. 6. If the crude sulphuret of antimony be boiled with solution of pure potash ; the solution, on cool- ing, deposits a substance formerly termed Kermes mineral. ART. XXXI. MANGANESE'. 1. Manganese never occurs in a metallic state ; the black substance, known by that name, being a compound of manganese, with a large proportion of oxygen. The metal is obtained by mixing this oxyd, finely powdered, with pitch; making it info ;i ball j and putting this into a crucible, with powdered charcoal, T ^ of an inch thick on the sides, and J o an inch deep at the bottom. The empty space is then to be filled with powdered charcoal ; a cover is to be luted on ; and the crucible exposed, for one hour, to the strongest heat that can be raised. 2. This metal is of a dusky white colour, and bright and shining in its fracture. When exposed to the air, it soon crumbles into a blackish brow a powder, in consequence of its oxydation. 3. The metal is soluble in acids, but most readily in the nitrous. It is precipitated by alkalis, in the form of a white powder. 4. The black oxyd of manganese gives up its osygen, when distilled alone in a retovt ; or slili . * 3 114 more readily and abundantly, if distilled with a mixture of sulphuric acid. 5. It gives up its oxygen to muriatic acid. (See page 73-) 6. The black oxyd contains too much oxygen to dissolve in nitric acid ; but when to a portion of this acid in contact with the oxyd, a little sugar is added, and heat is applied, the oxyd is dissolved. 7. The black oxyd of maganese imparts to borate of soda, when melted with it, a violet colour. When this is effected by the blow-pipe, the colour may be destroyed by the interior flame, and again reproduced by the exterior one, or by a small par- ticle of nitre. 8. When powdered manganese, and nitre, are mixeJ together, and thrown into a red hot crucible, the nitric acid is decomposed j and we obtain a compound of highly oxydated maganese with pot- ash. 1 his compound has the singular property of exhibiting different colours, according to the quan- tity of water that is added to it. A small quantity gives a green solution ; a further addition changes it to a blue ; more still to purple ; and a still larger quantity to a beautiful deep purple. Hence this has I een termed the chameleon mineral. This property is destroyed by a very small quantity of sulphuret of potash. 9. The rose colour of solutions of maganese, in sulphuric and phosphoric acids, is destroyed, by ex- posure to the light of the sun, and restored again, when removed into darkness. This effect depends on the deoxydatk>n of the metal by the sun's rays. ART. XXX 11. COBALT. i. Cobalt may be purchased in a metallic form, at a price lower than that of pure silver. 115 2. Cobalt becomes tarnished by exposure to nir, but is not easily oxydated, to any extent, by the action of heat and air combined. 3. Its best solvents are the nitric and nitro- muriatic acids ; and the solutions have the singular property of forming sympathetic inks. Characters, written with these solutions, are illegible when cold j but, when a gentle heat is applied, they assume a beautiful blue or green colour*. This ex- periment is rendered more amusing, by drawing the trunk and branches of a tree, in the ordinary manner, and tracing the leaves with a solution of cobalt. The tree appears leafless, till the paper is heated, when it suddenly becomes covered with beautiful foliage. 4. Oxalic acid throws down, from solutions of cobalt, a rose coloured precipitate. 5. Cobalt, when oxyded, forms zafTre, which has the property of giving a deep blue colour to glass. The rarer and newly discovered metals, Molybde- nite, Uranite, Tellurite, Chrome, &c. I omit; be- cause, owing to their dearness and scarcity, they are not likely to become subjects of experiment to the chemical student. ART. XXXIII. NICKED. This metal may, also, be procured in the state of a regulus. Its solutions in nitrous and muriatiq acids are of a green colour, and are precipitated blue by ammonia, in which the oxyds are, also, soluble. * For some ingenious speculations on the cause of these phe- nomena, consult Mr. Hatchett's paper on the Carinthian mulyt)-* an.tf is inflammable when 127 heated, taking fire on the approach of a lighted paper, and burning like alcohol. 3. It unites with alcaiis, and the solutions, when evaporated, do not become black Hence it is probable that the change of acetous into acetic acid depends in great measure on the separation of carbon. 5 This acid may be obtained from the acetite of copper by distillation per se 5. The acetic acid, in the temperature of 38 of Faht, congeals or becomes glacial; and again li- quefies at ^9. 6. When distilled with alcohol it affords an ether, termed acetic ether. The acetous acid may be, also, combined with oxyds of lead and of copper Lead corroded into a white oxyd, or rather carbonate, by the fumes of vinegar, forms ceruse or white lead, which, when dissolved in distilled vinegar, and crystallized, con- stitutes the acetite or sugar of lead. This salt is not decomposed, without the addition of sulphuric acid. Copper, corroded in a similar manner, affords ver- digris, which, when dissolved in distilled vinegar, affords a crystallizable salt, called acetate of copper. From this the acetic acid may be separated by distillation per se. ART. XXXV. ANIMAL SUBSTANCES. I. ANIMAL JELLY. Animal jelly may be extracted from most of the soft parts of animals, and even from bones, by long continued boiling. It forms the basis of soups, broth, &c. and imparts to these their nutritious properties. It is readily soluble in warm water > and eon- 128 geals, when cold, into a cohesive stibstance, which may again be dissolved by water. It becomes sour, when exposed to the influence of the air. When evaporated to dryness, it forms portable soup, glue, isinglass, &c. 2 ANIMAL ALBUMEN. The white of an egg may be employed, in exhi* biting the qualities of animal albumen. A Albumen is insoluble in water, even at the boiling temperature. B. It is soluble in pure -Icalis, and is precipitated again by the addition of acids. t . It is coagulated, by the temperature of 160, into a solid cohesive mass j and also, by acid : >, oxyds, and alcohol. The coagulum, thus pro- duced, is soluble in alkalis only, and during the solution ammonia is evolved. D. On exposure to air, it passes to the putre- factive state. E, When exposed to a gentle heat, in a retort, with diluted nitric acid, azotic gas is disengaged, which proceeds not irora the aeid, but from the animal matter. GLUTES, OR ANIMAL FIBRE. Gluten forms the basis of the muscular or fleshy parts of animals, and remains, combined with al- bumen, when all the soluble parts have been was.hed away by water. It may, also be obtained from coagulated blood by laying this on a linen strainer, and pouring on water, till a white fibrous matter alone remains. i. Gluten is insoluble in water, except by ths long continued heat of a Papin's digester. 129 2. It is soluble in acids, and in pure alkalis. 3. With diluted nitric acid, it yields much more azotic gas than any other animal substance. 4. It differs from albumen, in being coagulated by the mere contact of air, and by a temperature of 120 j and in being insoluble in cold liquid ammo- nia Its structure, also, is fibrous 3 whereas that of albumen is smooth and homogeneous. ANIMAL OIL. Animal oil differs frcrn the vegetable oils, in be- ing generally solid at the temperature of the atmo- sphere, but is similar to tbem in its other properties. Among animal oils, may be ranked butter, tallow, lard, suet, spermaceti, &c. They all contain a peculiar acid, called thesebacic acid. This may be obtained, by adding to the oil, when liquefied by heat, finely powdered quicklime; collecting the sebate of lime ; and distilling it with sulphuric acid. A singular instance of the production of animal oil from the lean or muscular part of animals, is presented by the conversion of muscle into a sub- stance strongly resembling spermaceti. To effect this conversion, it is only necessary to confine the fleshy part of an animal, in a box with several holes in it, under the surface of a running stream. When thus confined, the change takes place spon- taneously in the course of a few months. But it may be accomplished, much sooner, by digesting animal muscle in strong nitric acid, and washing off the acid by water, as soon as the change has ensued. The spermaceti, thus obtained, may be bleached, by exposure to the oxygenated muriatic acid gas. ISO ANIMAL ACIDS. Of these, I shall mention none except the prussic ncid. as being the only one likely to be the subject of experiment. The prussic acid is formed in animal matters, w^.en exposed to a high temperature. Let blood be evaporated to dryness, and let the dried blood be mixed with an equal weight of carbonate of potash, and the mixture be exposed to heat in a crucible, two thirds only of which are filled. The crucible is to have a cover applied, and the heat must be kept up till the flame ceases to proceed from the ma- terials. By this operation, the prussic acid is formed, and combines with the potash. The prussiate of potash is next to be washed off, by repeated effu- sions of water; and mixed with a solution of sul- phates of iron and alumine. The precipitate, thus formed, ' wjien washed with muriatic acid will assume a beautiful blue colour, which is owing to a combination of prussic acid with oxyd of iron. This prussiate of iron has the properties already described, page 105, No. 5. The prussic acid may be obtained, in a separate state, by the process described in Cbaptal's Ele- ments, Vol. II. IS! PART II. DIRECTIONS FOR EXAMINING MINERAL 'WATERS, AND MINERAL BODIES IN GENERAL. 1 HE complete and accurate analysis of mineral waters and of mineral bodies in general, is one of the most difficult subjects of chemical manipulation 5 and requires a very extensive acquaintance with the properties and habitudes of a numerous class of substances. Long and attentive study of the science is therefore, essential to qualify any one for undertaking exact and minute determinations of the proportion of the component parts of bodies, Such minuteness, however, is scare* ly ever re- quired, in the experiments that are subseivient to the ordinary purposes of life; a general knowledge of the compos tion of bodies, being sufficunt to assist in directing the most useful a plications of them I shall not attempt, therefore, to lay down rules for accurate analysis ; but shall only describe such experiments, as are suited to afford an insight into the kind, but not to decide the exact propor- tion, of the constituent principles of natural waters, and of mineral substances in general. SECT. I. EXAMINATION OF MINERAL WATERS. Water is never presented by nature in a state of complete purity. Even when collected as it de- scends in the form of r ain, chemical tests detect in it a minute proportion of foreign ingredients. And 133 when it has been absorbed by the earth ; has tra- versed its different strata; and is returned to us by springs, it is found to have acquired various impregnations. The readiest method of judging of the contents of natural waters, is by applying what are termed tests, or reagents ; i. e. substances, which, on being added to a water, exhibit, by the phenomena they produce, the nature of the saline or other ingredients. For example, if on adding infusion of litmus to any water, its colour is changed to red, we infer, that the water contains an uncom- bined acid: If this change ensues, even after the water has been boiled, we judge that the acid is a fi ed and not a volatile one : And if, on adding the muriated barytes, a precipitate falls down, \ve safely conclude that the peculiar acid, present in the water, is, either entirely or in part, the sulphuric acid. I shall first enumerate the tests, generally employed in examining waters, and describe their application j and, afterwards, indicate by what particular tests the substances, generally found in waters, may be detected. I. INFUSION OF LITMUS- SYRUP OF VI'OLETS, &C. As the infusion of litmus is apt to spoil by keep- ing, 1 include in the chest some solid litmus. The infusion >s prepared by steeping this substance, first bruised in a mortar, and tied up in a thin rag, in distilled water, which extracts its blue colour. Jf the colour of the infusion tends too much to purple, it may be amended by a drop or two of so- lution of pure ammonia ; but of this, no more must be added than is barely sufficient, lest the delicacy of the t st should be impaired. The syrup of violets is not easily obtained pure. The genuine syrup may be distinguished from the 133 spurious, by a solution of corrosive sublimate, which changes the former to green, while it reddens the latter. When it can be procured genuine, it is an excellent test of acids, and may be employed in the same manner as the infusion of litmus. Paper stained with the juice of the march violet, or with that of radishes, answers a similar purpose. In staining paper for the purposes of a test, it must be used unsized; or if sized, it must previously be washed with warm water; because the alum, which enters into the composition of the size, will other- wise change the vegetable colour to red. In the Philosophical Magazine, Vol. I. p. 180, may be found some recipes for other test liquors, invented by Mr. Watt. Infusion of litmus is a test of most uncom- bined acids. (1) If the water, under examination, redden the unboiled, but not the boiled water ; 'or if the red colour, occasioned by adding the infusion to a recent water, return to blue on boiling, we iruiy infer that the acid is a volatile one, and most pro- bably the carbonic acid. Sulphurated hydrogen gas, dissolved in water, also reddens litmus, but not after boiling. (2) To ascertain whether the change be produced by carbonic acid, or sulphurated hydrogen, when experiment shows that thereddening cause is volatile, add a little lime water. This, if carbonic acid be present, will occasion a precipitate, which will dissolve, with effervescence, on adding a little mu- riatic acid. Sulphurated hydrogen may, also, be contained in the same water, which will be ascer- tained by the tests hereafter to be described. (3) Paper tinged with litmus is, also, reddened by the presence of carbonic acid, but regains its blue colour on drying. The mineral and fixed aeids M 134 redden it permanently. That these 'acids, however, may produce their effect, it is necessary that they should be present in a sufficient proportion. (See Kirwan on Mineral Waters, p. 40.) II. INFUSION OF LITMUS REDDEN ED BY VINEGAR SPIRITUOUS TINCTURE OF BRAZIL WOOD TINCTURE OF TURMERIC AND PAPER STAINE'D WITH EACH OF THESE THREE SUBSTANCES SYRUP Of VIOLETS. All these different tests have one and the same object. (1) Infusion of litmus reddened by vinegar, or litmus paper reddened by vinegar, has its blue colour restored by pure alkalis and -pure earths, and by carbonated alkalis and earths. (2) Turmeric paper and tincture are changed to a reddish brown by alkalis, whether pure or car- bonated, and b) pure earths, but not by carbo- nated-earths. (3) The red infusion of brazil wood, and paper stained with it, become blue by alcalis and earths, and even by the latter when dissolved by an excess of carbonic acid. In the last mentioned case, however, the change will either cease to appear, or be much less remarkable, when the water has been boiled. (4) Syrup of violets, when pure is, by the same causes, turned green ; as also paper stained with the juice of the violet or wiih radishes. III. TINCTURE OF GALLS. Tincture of galls is the test generally employed for discovering iron, with all the combinations of which it produces a black tinge, more or less in- 13 j tense according to the quantity of iron. By ap- plying this test before and after evaporation or boil- ing, we may know whether the iron be held in so- lution by carbonic acid, or a fixed acid ; for (1) It" it produce its effect before the application of heat and not afterward, carbonic acid is the solvent. (2) If after as well as before, a mineral acid is the solvent. (3) Jf by the boiling a yellowish powder be pre- cipitated, and yet galls continue fo strike the water black afterwards, the iron, as often happens, is dis- solved both by carbonic acid and by a fixed acid, IV. SULPHURIC ACID. (1) Sulphuric acid discovers, by a slight efferves- cence, the presence of carbonic acid, whether un- combined, or united with alcalis or earths. (2) If lime be present, whether pure or uiicom- bine.d, the addition of sulphuric acid occasions, after a few days, a white precipitate. (3) Barytes is precipitated, instantly, in '.he form of a white, powder. (4) Nitrons and muriatic salts, 01 adding sul- phuric acid and applying heat, are decomposed ; and if a stopper, moistened' with solution of pure am- monia, be held over the vessel, white clouds will appear. For distinguishing whether nitric or mu- riatic acid be the cause of this appearance, rules \vill be given hereafter. V. NITRIC AND KITEOUS ACIDS. These acids, if they occasion effervescence, give the same indications as the sulphuric. The nitrous acid has been recommended, as a test distinguish- ing between hepatic waters that contain sulphuret M 2 136 of potash, and those that contain only sulphurated hydrogen gas. In the former case a precipitate rnsues on adding nitrous acid, and a very feet id smell arises : In the latter a slight cloudiness only appears, and the smell of the water becomes less disagreeable. VI. OXALIC ACID; AND OXALATES. This acid is a moft delicate test of lime, which it separates from 11 its combinations. (1) Ii" a water, which is precipitated by oxalic acid, become milky on adding a watery solution of carbonic acid, we may infer that pure lime. (or barytes, which has never yet been found pure in waters) is present. (2) If the oxalic acid occasion a precipitate, be- fore but not after boiling, the lime is dissolved by an excess of carbonic acid ; (3) If after boiling, by a fixed acid. A consi- derable excess of any of the mineral acids, however, prevents the oxalic acid from occasioning a preci- pitate, even though lime be present, because some acids decompose the oxalic, and others, dissolving the oxalate of lime, prevent it from appearing. (Vid. Kirwan on Waters, p. 88.) The oxalate of ammonia, or of potash, (which may easily be formed by saturating their respective carbonates with a solution of oxalic acid) are not liable to the above objection ; and are preferable, as reagents, to the uncombined acid. The fluate of ammonia, recommended by Scheele, I find to be a most delicate test of lime. It may- be prepared by adding carbonate of ammonia to diluted fluoric acid, observing that there be a small excess of acid. 137 vii. PURE ALKALIS, AND CARBONATED ALKALIS. (1) The pure fixed alkalis precipitate all earths and metals, whether dissolved by volatile or fixed menstrua; but only in certain states of dilution 5 for example, sulphate of alumine may be present in water, in the proportion of 4 grs. to 500, without being discovered by pure fixed alcalis. As the alkalis precipitate so many substances, it is evident, that they cannot afford any very precise information, when employed as reagents. From the colour of the precipitate, as it approaches to a pure white, or recedes from it, an experienced eye will judge, that the precipitated earth contains less or more of me- tallic admixture. (2) Pure fixed alcalis, also, decompose all salts with basis of ammonia, which becomes evident by its smell, and also by the white fumes it exhibits, when a stopper, moistened with muriatic acid, is broaght near. (3) Carbonates of potash and soda have similar effects. (4) Pure ammonia precipitates all earthy and me- tallic salts. Beside this property, it, also, imparts a deep blue colour to any liquid that contains cop- per in a state of solution. (5) Carbonate of ammonia has the same proper- ties-, except that it does not precipitate magnesia from its combinations. Hence, to ascertain whether tliis earth be present in any solution, add the car- bonate of ammonia, till no further precipitation ensues -, filtre the liquor; and then add pure am- monia. If any precipitation now occurs, we may infer the presence of magnesia. 138 VIII. LIME-WATER, As any quantity of lime-water, that can be in- cluded in a chemical chest, would very soon be ex- pended, it will be necessary for the experimenter to prepare it himself, which may be done according to the process described in page 82. (1) Lime water is applied to the purposes of a test, chiefly for detecting carbonic acid. Let any liquor, supposed to contain this acid, be mixed with an equal bulk of lime-water. If carbonic acid be present, either free or combined, a precipitate will immediately appear, which, on adding a few drops of muriatic acid, will again be dissolved with effer- vescence. (2) Lime.water will also shew the presence of corrosive sublimate, by a brick-duft coloured sedi- ment. If arsenic be contained in a liquid, lime- water, when added, will occasion a precipitate, consisting of lime and arsenic, which is very dif- ficultly soluble in water. This precipitate, when mixed up with oil and laid on hot coals, yields the well known garlic smell of arsenic. I-X. PURE BARYTES, AND ITS SOLUTION IN WATER. (i) A solution of pure barytes is even more ef- fectual than lime-water, in detecting the presence of carbonic acid, and is much more portable and convenient, since from the crystals of this earth, which are also included in the chest, the baryt;c solution may at any time be immediately prepared. In discovering fixed air, the solution of barytes is used similarly to lime-water, and if this acid be pre- sent, gives, in like manner, a precipitate, soluble with effervescence in dilute muriatic acid. 139 (2) The barytic solution is, also, a most sensible test of sulphuric acid and its combinations, which it indicates by a precipitate, not soluble in muriatic acid. Pure strontites has similar virtues as a test. X. METALS. (1) Of the metals, silver and mercury are tests of the presence of sulphurets, and of sulphurated hy- drogen gas. If a little quicksilver be put into a bottle, containing water impregnated with either of these substances, its surface soon acquires a black film, and, on shaking, a blackish powder separates from it. Silver is immediately tarnished by the same cause. (2) The metals may be used, also, as tests of each other on the principle of elective affinity. Thus, for example, a polished iron plate, immersed in a solution of sulphate of copper, soon acquires a coat of this metal 5 and the same in other similar examples. XI. SULPHATE OF IRON. This is the only one of the sulphates, except that of silver, applicable to the purposes of a test. When used with this view, it is generally em- ployed for ascertaining the presence of oxygenous gas, of which a natural water may contain a small quantity. A water, suspected to contain this gas, may be mixed with a little recently dissolved sulphate of iron, and kept corked up. If an oxyd of iron be precipitated, the water may be inferred to contain oxygenous gas. 110 XII. SULPHATE, NITRATE, AND ACETITE OF SILVER. These solutions are all, in some measure, appli- cable to the same purpose. (1) They are peculiarly adapted to th j discovery of muriatic acid, and of muriates. For the silver, quitting the nitric acid, combines with the muriatic, and forms a fiakey precipitate, which, at first, is white, but, on exposure to the sun's light, acquires a bluish colour. A precipitation, however, may arise from other causes, which it may be proper to state. (2) The solutions of silver in acids are precipitated by carbonated alcalis and earths. The agency of these may be prevented by previously adding a few drops of the same acid, in which the silver is dissolved. (3) The nitrate and acctite of silver are decom- posed by the sulphuric and sulphureous acids ; but this may be prevented by adding, previously, a few drops of nitrate or acetite of barytes, and, after allowing the precipitate to subside, the clear liquor may be decanted, and the solution of silver be added. Should a precipitation now take place, the- presence of muriatic acid, or some one of its com- binations, may be suspected. To obviate uncer- tainty whether a precipitation be owing to sulphu- ric or muriatic acid, a soJation of sulphate of silver may be employed, which is affected only by the latter acid. (4) The solutions of silver are, also, precipitated by sulphurated hydrogen and by sulphurets; but the precipitate is then reddish, or brown, or black; or it may be at iirst white, and afterwards become speedily brown or black. It is soluble in dilute nitrous acid, which is not the case, if occasioned by muriatic or sulphuric acid. (5) The solutions of silver are precipitated by ex- 141 tractive matter; but in this case, also, the precipitate is discoloured, and is soluble in nitrous acid. XIII. NITRATE AND ACETITE OF LEAD. (1) Acetite of lead, the most eligible of these two test.-, is precipitated by sulphuric and muriatic ticids, but as of both these we have much better in- dicators, I do not enlarge on its application to this purpose. (2) The :\cetite is also a test of sulphurated hydrogen, and of sulphurets of alealis, which occasion a black precipitate j and if a paper, on which characters are traced with a solution of acetite of lead, be held over a portion of water containing sulphurated hydrogen, they are soon rendered visible. (3) The acetite of lead is employed in the dis- covery of uncombined boracic acid, a very rare ingredient of waters. To ascertain whether this be present, some cautions are necessary, (a) The uncombined alkalis and earths (if any be suspected) must be saturated with acetic or acteous acid (b) The sulphates must be decomposed by acetite or nitrate of barytes, and the muriates by acetite or nitrate of silver. The filtered liquor, if boracic acid be contained in it, will give a precipitate solu- ble in nitric acid of the specific gravity of i. 3. XIV. NITRATE OF MERCURY PREPARED WITH AND WITHOUT HEAT. This solution, differently prepared, is sometimes employed as a test. But since other tests answer the same purposes more effectually, I have not thought proper to include the nitrate of mercury in the chest. For the same reason, also, oxygenated muriate of mercury is omitted. 142 ^V\ MURIATE, NITRATE, AND ACET1TE OF BARYTAS. (1) These solutions are all most delicate tests of sulphuric acid, and of its combinations, with which they give a white precipitate, insoluble in dilute muriatic acid. They are decomposed, however, by carbonates of alkali ; but the precipitate, occa- sioned by these, is soluble in dilute muriatic or nitric acids, with effervescence. (2) Phosphoric halts occasion a. precipitate, also, which is soluble in muriatic acid, without effer- vescence. XVI. PRUSSIATES OF POTASH, AND OF LIME. Of these two, the prussiateof potash is the most eligible When pure it does not speedily assume a blue colour on the addition of acid, nor dots it immediatdi; precipitate muriated b;'.rytcs. Prussiateof potash is a very sensible test of iron, with whose solutions in acids, it produces a Prussian blue precipitate, in consequence of a double elective affinity. To render its efiect more certain', how- ever, it may be proper to add, previously, ?o any water suspected to contain iron, a little muriatic acid, with a view to the saturation of uncombincd alkalis or earths, which, if present, prevent the detection of very minute quantities of iron. (1) If a water, after boiling and filtration, does not afford a blue precipitate, on the addiiion of prussiate of potash, the solvent of the iron may be inferred to be a volatile one, and probably the carbonic acid (2) Should the precipitation ensue in the boiled water, the solvent is a fixed acid, the nature, of which must be ascertained by other tests. 145 The best mode of preparing prussiate of potash, in a state of purity, is described by Mr. W. Henry, in Nicholson's Journal, vol. 4, XVII. SOLUTION OF SOAP IN ALCOHOL. This solution may be employed to ascertain the comparative hardness of waters. With distilled water it may be mixed, without any change en- suing; but if added to a hard water, it produces a milkiness, more or less considerable, as the water is less pure; and from the degree of this milkiness, an experienced eye will derive a tolerable indication of the quality of the water. This effect is owing to the alkali quitting the oil, whenever there is pre- sent in a water any substance, for which the alkali has a stronger affinity than it has for oil. Thus all uncombined acids, and all earthy and metallic salts decompose soap ; and occasion that property in waters which it termed hardness. XVIII. ALCOHOL. Alcohol, when mixed with any water, in the proportion of about an equal bulk, precipitates all the salts, which it is incapable of dissolving. (See dbLirwan on Waters, p. 263.) XIX. SULPHUUATE OF AMMONIA. This and other sulphurets, as well as water saturated with sulphurated hydrogen, may be em- ployed in delecting lead and arsenic, with the former of which they give a black, and with the latter a yellowish, precipitate. As lead and arsenic, however, are never found in natural waters, I shall reserve, for another occasion, what I hav.e to say of the application of these tests. 144 SUBSTANCES THAT MAY BE EXPECTED IN MINERAL WATERS} AND THE MEANS OF DETECTING THEM. ACIDS IN GENERAL. Infusion of litmus Syrup of violets, I. ACID BORACIC. Acetite of lead, XIII. 3. ACID CARBONIC. Infusion of litmus, I. i. 2. Lime water, VIII. i. Barytic water IX. i. ACID MURIATIC. Nitrate and acetite of silver, XII. ACID NITRIC. Sulphuric acid, IV. 4. ACID PHOSPHORIC. Solutions of barytes, XV. 2. ACID SULPHUREOUS. By its smell and de- stroying the colour of litmus, and of infusion of red roses by the cessation of the smell, a few hours after the addition of the black oxyd of man- ganese. ACID SULPHURIC. Solution of pure barytes, IX. Barytic salts, XV. Acetite of lead, XII. ALCALIS IN GENERAL. Vegetable colours, II. AMMONIA, by its smell and tests, II. BARYTES AND ITS COMPOUNDS, by sulphurrc acid, IV. CARBONATES IN GENERAL. Effervesce on adding acids. EARTHS DISSOLVED BY CARBONIC ACID. By a precipitation on boiling by pure alkalis, VII. IRON DISSOLVED BY CARBONIC ACID. Tincture of galls, III. i. Prussiate of potash, XVI. i. BY SULPHURIC ACID. Same tests, III. 3. XVI. 2. 145 LIME IN A PURE STATE. Water saturated with carbonic acid. Blowing air from the lungs. Oxalic acid, VI. DISSOLVED BY CARBONIC ACID. Pre- cipitation on boiling Caustic alkalis, VII. Oxalic acid, VI. MAGNESIA DISSOLVED BY CARBONIC ACID. Precipitation on boiling the precipitate soluble in dilute sulphuric acid. MURIATES or ALCALIS. Solutions of silver, XII. OF LIME. Solutions of silver, XIL and oxalic acid, VI. SULPHATES IN GENERAL. Baiytic solutions, IX. and XV. Acetite of lead, XII. SULPHATE OFALUMINE. Barytic solutions, IX. and XV. A precipitate by carbonate of ammonia not soluble in acetous acid, but soluble in pure fixed alkalis by boiling. SULPHATE OF LIME. Barytic solutions IX. and XV. Oxalic acid, VI. A precipitate by alkalis not soluble in dilute sulphuric acid. SULPHURETS OF ALCALIS. Polished metals, X. Smell on adding sulphuric or muriatic acid. Ni- trons acid, V. SULPHURATED HYDROGEN GAS. Infusion of lit- mus, I. Polished metals, X. Acetite of lead, XIII. 2. The reader, who may wish for rules for the com- plete and accurate analysis of mineral waters, will lind in almost every elementary work, a chapter allotted to this subject. He may, also, consult Bergman's Physical and Chemical Essays, Vol. I. Essay zd. and Kirwan's Essay on the Analysis of 146 Mineral Waters, London, 1799. As this manual, however, may sometimes be employed as a travel- ing conipanion, and may attend the chemist where more balky works cannot be had, it may be proper to state, briefly, the mode of analyzing waters, by the more certain, but still not unobjectionable, mode of evaporation. The vessels, employed for evaporation, should be of such materials, as are not likely to be acted on by the contents of the water. I prefer those of un- glazed biscuit ware, made by Messrs. Wedgwoods; but as their surface is not perfectly smooth, and the dry mass may adhere so strongly as not to be entirely scraped off, the water, when reduced to about one tenth or less, may be transferred, with any deposit that may have taken place, into a smaller vessel of glass. Here, let it be evaporated to dryness. A. The dry mass, when collected and accurately weighed, is to be put into a bottle, and alcohol poured on it, to the depth of an inch. After having stood a few hours, and been occasionally shaken, pour the whole on a filtre, wash it with a little more alcohol ; and dry and weigh the remainder. B. To the undissolved residue, add eight times its weight of cold distilled water ; shake the mixture frequently; and, after some time, filtre j ascertain- ing the loss of weight. C. Boil the residuum for a quarter of an hour, in some what more than 500 times its weight of water, andvafterwards filtre. D. The residue, which must be dried and weighed, is no longer soluble in water or alcohol. If it has a brown colour, denoting the presence of iron, let it be moistened with water, and exposed to the sun's rays for some weeks. I. The solution in alcohol (A) may contain one or all of the following salts muriates of lime, mag- 147 nrsia, or barytes, or nitrates of the same earth?., Sometimes, al*o, the alcohol may lake up a sulphate of iron, in which the metal is highly oxydated $ as \vi!l appear fronj its reddish brown colour. t. in order to discover the fnialiiy arul quantity of the ingredients, evaporate todryness, add alxnc: half its weight of: strong sulphuric-acid, and apply a mode- rate heat, Therminaucorttitricacid will IK- ex pel led j Find will be known by the colour of their fum:^, the former being white, and tin- latter orsn-ge coloured. 2. To ascertain whether lime or magnesia be the basis, let the heat bo continued, till no more fumes arise j and let it then be raised, to expel the excess of sulphuric acid. To the dry masv, add twice its weight of distilled water. This will take up the sulphate of magnesia, and leave the sulphate of lime. The two sulphates may be separately decomposed by boiling with three or four times their weight of carbonate of potash. The carbonates of lime and magnesia, thus obtained, may be separately dis- solved in muriatic acid and evaporated. The weight of the dry Stilts will inform us, how much of each the alcohol had taken up. The presence of barytes, which is very rarely to be expected, may be known by a precipitation en- suing, on adding sulphuric ackl to a portion of the alcohol solution, which has been diluted with 50 or Co times its bulk of pure water. II. The watery solution (B) may contain a variety of salts; the accurate separation of which, from each other, is a problem of considerable difficulty. i. The analysis of this solution may be attempted by crystallization. For this pur pole, let one half be evaporated by a very gentle heat, not exceeding 80 or 90. Should any crystals appear on the sur- face of the solution while hot, in the form of a pellicle, let them be separated and dried on bibu- H8 Jous paper. These are muriate of soda or common salt. The remaining solution, on cooling very gra- dually, will, perhaps, afford crystals distinguishable by their form and other qualities. When a variety ot" salts, however, are contained in the same solu- tion, it is extremely difficult to obtain them suffi- ciently distinct to ascertain their kind. 2. The nature of the saline contents must, there- fore, be examined by tests or reagents. The presence of an uncombined alkali will be discovered by the stained papers (p. 134), and of acids by the tests (p. 132). The vegetable alcali vv potash may be distinguished from the mineral or soda, by saturation with sulphuric acid, and evapo- ration to dryness; the sulphate of soda being much more soluble than that of potash ; or by supersatu- ration with the untarous acid, which gives a soluble salt with soda, but not with potash. If neutral salts be present in the solution, we have to ascertain both the nature of the acid and of the basis. This may be done by attention to the rules already given for the application of tests, \vhich it is unnecessary to repeat in this place. III. The solution by boiling water contains scarcely any thing besides sulphate of lime. IV. The residuum (D) is to be digested in distill- ed vinegar, which takes up magnesia and lime, but leaves, undissolved, alumine and highly oxydated iron. Kvaporate the solution todrynesb. If it con- tain acetitc of lime only, a substance will be ob- tained, which does not attract moisture from the air ; if magnesia be present, the mass will deli- quiate. To separate the lime from the magnesia, proceed as in I. 'I he residue, insoluble in acetous acid, may con- tain alumine, silex, and iron. The two first may be dissolved by muriatic acid, from which the iroa '149 maybe precipitated first by prussiate of potash, and the alumine afterward by a fixed alcali. SECT. II. EXAMINATION OF MINERALS. The chemical analysis of minerals is attended even with greater difficulties than that of natural waters. It would, therefore, be a vain attempt to comprehend, in a concise manual, rules sufficiently minute for the accurate separation of their com- ponent principles. On the present occasion, I mean only to offer a few general directions for attaining such a knowledge of the composition of mineral bodies, as may enable the chemical student to refer them to their proper place in a mineral arrange- ment 3 and to judge whether or not they may admit of application to the uses of common life*. The great variety of mineral bodies, which nature presents in the composition of this globe, have been classed by late writers under a few general divisions. They may be arranged under four heads, ist. Earths. 2dly. Salts. 3dly. Inflammable fossils and 4thly. Metals, and their Ores. EARTHS. The formation of such a definition of earths, as would apply exactly to the bodies defined, and to no others, is attended with considerable dif- ficulty, and indeed has never yet been effected. It would lead me into too long a discussion, to com- ment, in this place, on the definitions that have been generally offered, and to state the grounds of objection to each of them. Sensible, therefore, that I am unable to present an unexceptionable character of earthy bodies, I shall select such a one, as may * Those who are solicitous to become adepts in the art of ana- lysis, may read attentively the numerous papers on this subject, dispersed through various chemical collections, and especially an a~bi'/ii-:ible work of M,.Klaproth, lately translated intu JLnglish. N 3 150 I e sufficient for tre less accurate purpose of general distinction. " The term earth," says Mr. Kirwan, " denotes a tasteless, inodorous, dry, brittle, uninflammable substance, whose specific gravity does not exceed 4. 9. (i. e. which is never five times heavier than water), and which gives no tinge to borax in fusion." After stating some exceptions to this definition, afforded by the strong taste of certain earths, and the solubility of others, he adds : " Since, however, a line must be drawn between salts and earths, I think it should begin where solution is scarce per- ceptible ; salts terminating, and earths, in Strict- ness, commencing, where the weight of the water, requisite for the solution, exceeds that of the sol- vend, icoo times. But, not to depart too widely from the commonly received import of words that ore in constant use, substances, that require 100 times their weight of water to dissolve them, and luve the other sensible properties of earths, may be so styled in a loose and popular sense." 1 he simple, or primitive earths, are those which cannot be resolved into more remote principles. Such are lime, argill, magnesia, &c. The compound earths are composed of two or more primitive earths, united chemically together. Sometimes, the union of an earth with an acid con- stitutes what is vulgarly called an earth, as in the examples of sulphate of Hme, fluate of lime, &c. SALTS. Under this head, Mr. Kirwan arranges " all those substances, that require less than 200 times their weight of water to dissolve them." This description, though by no means so amply charac- teristic of the class of salts, as to serve for an exact definition, is sufficient for our present purpose. '* By INFLAMMABLE FOSSILS," tbs same author observes, " are to be' iu;ck.T:-uod all those, of mi- 151 neral origin, whose principal character is inflam- mability, a criterion, which excludes the diamond and metallic substances, though, also, susceptible of combustion." METALLIC SUBSTANCES are so well characte- rized by external properties, as not to require any definition. " Those, on which nature has bestow- ed their proper metallic appearance, or which are alloyed only with other metals or semi-metals, are- called native metals. But those that are distin- guished, as they commonly are in mines, by combi- nation with some other unmetallic substances, are said to be mineralized. The substance that sets them in that state is called a mineralizer, and the compound of both an ore." Thus, in the most common ore of copper, this metal is found oxydated, ' and the oxyd combined with sulphur. The copper may be said to be mineralized by oxygen and sul- phur, and the compound of the three bodies is called an ore of copper. METHOD OF EXAMINING A MINERAL, THE COM- POSITION OF W r HICH IS UNKNOAVN. A mineral substance presented to our examina- tion, without any previous knowledge of its com- position, should first be referred to one of the above four classes, in order that we may attain a general knowledge of its nature, before proceeding to ana- lyze it minutely. I. To ascertain whether the unknown mineral contains saline matter, let 100 grains, or any other determinate quantity, in the state of fine powder, be put into a bottle, and shaken up repeatedly with 30 times its weight of water, of the temperature of 120 or 130. After having stood an hour or two, pour the contents of the bottle on a filtering paper, pre- 152 vionsly weighed, and placed on a funnel. When the water has drained off, dry the powder on the filtre, in a heat of about 212; and, when dry, let the whole be accurately weighed. If the weight be conside- rably less than (he joint weight of the powder before digestion and the tillering paper, we may infer that some salt has been dissolved, and the decrease of weight will indicate its quantity. In certain cases, it may be adviseable to use re- peated portions of boiling water, when the salt, sus- pected to be present, is difficult of solution. Should the mineral, under examination, be proved, by the foregoing experiment, to contain much salt, the kind and proportion must next be determined, by rules which will hereafter be laid clown. II. The second class, viz. earthy bodies, are distinguished by their insolubility in water ; by their freedom from taste; by their unintiarnmability ; and by their specific gravity never reaching c;. if, therefore, a mineral be insoluble in water, when tried in the foregoing manner ; if it be not consumed, either wholly or in considerable part, by keeping it, for some time, on a red hot iron ; we may conclude that it is neither a salt nor an inflammable body. III. The only remaining class, with which it can be confounded, are ores of metals, from many of which it may be distinguished, merely by poising it in the hand*- the ores of metals being always heavier than earths. Or if a dtmbtshould still remain, it may be weighed hydrostatically. The mode of doing this & may be proper to describe; but the principle, on which the practice is founded, cannot with pro- priety b" explained here. Let the* mineral be suspended by a piece of line hair, silk, or thread, from the scale of a balance, and weighed in the air. Suppose it to weigh 2^0 grains. Let it next (still suspended to *the balance) be immersed 153 in a glass of water of the temperature of 60. The scale containing the weight will now preponderate. Add, therefore, to ihe scale from which the mineral hangs, as many grain weights as are necessary to restore the equilibrium. Suppose that 50 grains are necessary : then, the specific gravity may be learned by dividing the weight in air by the weight lost in water. Thus in the foregoing case, 250 50 ~ 5 ; or a substance, which should lose weight in water according to the above proportion, would be live times heavier than water. It must, therefore, con- tain some metal, though probably in no great quan- tity. Any mineral, which, when weighed in the above manner, proves to be j, 6, 7, or more .times heavier than water, may, therefore, be interred (v contain a metal, and may be referred to the class of ores. IV. Inflammable substances are distinguished by their burning away, either entirely or in considerable part, on a red hot iron ; and by their detonating, when mixed with powdered nitre, and thrown into a red hot crucible. Certain ores of metals, howr ever, which contain a considerable proportion of inflammable matter, answer to this test but may be distinguished from purely inflammable sub- stances, by their greater specific gravity. I shall now proceed to offer a few general rules, for the more accurate examination ot substances of each of the above classes ; without, however, pre- tending to comprehend, in this manual,, a code of directions sufficiently minute, to enable any one to perform a complete analysis.- I. EXAMTNATION OF SALTS. I. A solution of salt obtained in the foregoing manner (see page 151) may be slowly evaporated. 154 sfnct left to cool gradually. When cold, crystals will probably appear, which a chemist, acquainted with the form of salts, will easily recognize. But as se- veral different salts may be present in the same so- lution, and may not crystallize, in a sufficiently dis- tinct shape, it may be necessary to have recourse to the evidence of tests. 2. Let the salt, in the first place, be referred to one of the following orttara. (a) Ac-iils, or talts w/th excess of acid. These are known by their effect on blue vegetable colours. The particular species of acid may be discovered by the tests described, page 144. (b) Alcalis. These are characterized by their effect on vegetable colours, and by the other proper- ties enumerated, page 39. (c) Salts with metallic bases. These afford a very copious precipitate, when mixed with a solution of prussiate of potash. To ascertain the species of me- tal, precipitate the whole by prussiate of potash ; calcine the precipitate j and proceed according to th# rulgp, which will hereafter be given, for separating metals from each other. (d) Suits with earthy bases. If a solution of salt, in which prussiate of potash occasions no precipitation, afford a precipitate on adding pure or carbonated potash, we may infer, that a compound of an acid, with some one of the earths, is present in the solu- tion. Or if, after prussiate of potash has ceased to throw down a sediment, the above mentioned alcali precipitates a further portion, we may infer that both earthy and metallic salts are contained in the solution. In the first case, add the alcaline solution, and when it has ceased to produce any effect, let the sediment subside 5 decant the supernatant liquor ; and wash and dry the precipitate. The earths may be examined, according to the rules that will be 1 55 given in the following article. In the second case, prussiate of potash must be added, as long as it pre- cipitates any thing ; and the liquor must be decanted from the sediment, which is to be u ashed with dis- tilled water, adding the washings to what has been poured off. The decanted solution must next be mixed with the alcaline one, and the precipitated earths reserved for experiment. By this last pro- cess, earths and metals may be separated from each other. E, Neutral salts with alcaline bases. These salts are not precipitated either by prussiate or carbonate of potash. It may happen, however, that salts of. this claos may be contained in a solution, along with me- tallic or earthy ones. In this case, >the analysis be- comes difficult; because the alcali, that is added to precipitate the two last, renders it difficult to ascer- tain, whether the neutral salts are owing to this ad dition, or were originally present. I am not aware of any method of obviating this difficulty, except the following. Let the metals be precipitated by prussiate of ammonia ; and the earths by carbonate of ammonia, in a temperature of 1 80 or upwards, in order to ensure the decomposition of magnesian salts, which this carbonate does not effect in the cold. Separate the liquor by nitration, and boil it to dry ness. Then expose the dry mass to such a heat, as is sufficient to expel the ammoniacal salts. Those, with basis of fixed alkali, will remain fixed. By this process, indeed, it will be impossible to ascertain whether ammoniacal salts were originally present ; but this may be learned by adding, to the salt under examination, before its solution in water, some pure potash, which, if ammonia be contained in the salt, will produce its peculiar smell. The vegetable and mineral alkalis may be distinguished 156 by adding to the solution a little tartarous acid, which precipitates the former but not the latter. Having ascertained the basis of the salt, the acid will easily be discriminated. Iviuriated barytes will indicate sulphuric acid ; nitrate of silver the muri- atic ; . and salts containing nitric acid may be known by a detonation ensuing on projecting them, mixed with powdered charcoal, into a red hot crucible. II. EXAMINATION OF EARTHS AND STONES. When a mineral, the composition of which we are desirous to discover, resists the action of water, and possesess characters that rank it among earthy bodies, the next object of inquiry is the nature of the earths, that enter into its composition ; in other words, how many of the simple earths, and which of them, it may contain. Of these earths, viz. silex, alumine, magnesia, lime, strontites, and barytes, one or more, and sometimes all, may be expected in the composition of stones, besides a small propor- tion of metals, to which the colour of the stone is owing. In general, however, it is not usual to find more than four of the simple earths in one mineral. The newly discovered earths, jargonia, glucine, &c. occur very rarely. A stone, which is intended for chemical exami- nation, should be finely powdered ; and care should be taken that the mortar is of harder materials than the stone; otherwise, it will be liable to abrasion, and uncertainty will be occasioned in the result of the process. For soft stones, a mortar of Wedg- wood's ware is sufficient ; but for very hard ones, one of agate or hard steel is required ; and the stone should be weighed both before and after pulveriza- tion, that the addition, if any, may be ascertained 157 and allowed for. When a stone is extremely difficult to reduce to powder, it may sometimes be necessary to make it red hot, and, while in this state, to plunge it into eold water. By this treatment, it becomes brittle, and is afterwards easily pulve- rized. The chemical agents, employed in the analysis of stones, should be of the greatest possible purity. To obtain them in this state/directions have been given in the former part of this work. In treating of the analysis of stones, it may be proper to divide them, ist. into such as are soluble, either wholly or in part, and with effervescence, in nitric or muriatic acids, diluted with five or six parts of water; and 2dly, into such as do not dissolve in these acids. I . Earths or stottes, soluble with efferrescensce, in diluted 'nitric or sulphuric acids. A. If it be found, on trial, that the mineral, under examination, effervesces with either of these acids, Jet a given weight, finely powdered, be digested with one of them diluted in the above proportion, in a gentle heat, for two or three hours. Ascertain the loss of weight, in the manner pointed out, page 151, and filtre the solution, reserving the in- soluble portion. B. The solution, when effected, may contain lime, magnesia, alumine, barytes, or stromites. To ascertain the presence of the two last, dilute an aliquot part of the solution with 20 times its bulk of water, and add a little sulphuric acid, or, in preference, solution of sulphate of soda. Shoukl a white precipitate fall down, we may infer the pre- sence of barytes, of strontites, or of both. C. To ascertain which of these earths, (viz, barytes or strontites) is present 5 or, if both are contained in the solution, to separate them from SffS each other, add salphate of soda*, till the precipitate- ceases ; decant the supernatant liquid ; wash the sediment on a filtre ; and dry it. Then digest it with four times its weight of pure carbonate of potash, and a sufficient quantity of water, in a gentle heat, during two IT three hours. A double ex- change of principles will ensue, and we shall obtain a carbonate of barytes on strontites, or a mixture of both. Pour, on these, nitric acid, of the specific gravity 1.4, diluted with an equal weight of dis- tilled water. This will dissolve the-strontites, but not the barytes. To determine, whether any stron- tites-has been taken up by (he acid, evaporate the so- lution to dryness, and dissolve the dry massin^aleohol. This alcoholic solution, if it contain nitrate 06 strontites, will burn with a deep blood red flame. Baryte.s- and strontites may, also, be separated from each other, in the following manner. To a> saturated solution of the two earths in a*n acid, add prussiate of potash, which, if pure, w.ill occasion no- immediate precipitation ; but after soms time, small and insoluble crystals will form on the surface of the jar. These are the prussiatedi barytes, which may be changed into the carbonate by red heat, con- tinued with the access of air, till the black colour disappears. The strontites may be afterward sepa- rated from the solution- by carbonate of potash. A third method of separating strontites front barytes is founded on the stronger affinity of barytes, than of the former earth, for acids. Hence, if the two earths be present in, the same solution, add a solution of pure barytes (see page 93) till the pre- cipitation ceases. The barytes will seize the acid^ and will throw down the stromites. The strontitic solution, in this case, should have no excess of acid, which would prevent the action of the barytic earth. D. The solution (B) after the addition of sul- 159 piharte of soda, may contain Hme, magnesia, alu- mine, and some metallic oxyds. To separate the o-xyds, add prussiate of potash, till its effect censes, and tiltre the solution, reserving the precipitate for future 'experiments. E. When lime, magnesia, anclalumine a-re con- tained in the same solution, proceed as follows. (a) Precipitate the solution, previously made hot by carbonate of potash 5 wash the precipitate well, and dry it. It will consist of carbonates of iime, magnesia, and alomine. (b) The alumine HK.'V be ''separated, by digestion with a solution of Tjur.'e potash, which will -dissolve the nlumine, but nut the -other earths. (<".) I'o -this solution afnlnmine, dd -diluted inuriat-ic acid. ti : ll the -precipitate ceasvs ; decani the supernatant liquor : uk answers this purpose .extremely well, and hears, without breaking, 4ke .lfet and if lime be, also, found, the phosphate of lime is indi- cated. (d) To a portion of the liquor (a) add a solution: of muriate of lime, till the precipitate, if any, ceases. 164 Collect this precipitate, wash it, dry it; and pour ini it'a little sulphuric acid. Should acid fumes arise, the fluoric acid may be suspected. To ascer- tain its presence decisively, distil a portion of the pre- cipitate v\ n h hal; ns weiglit of sulphuric acid. The iiuoric acid \vill be- known by its effects on the re- tori, and by the properties described, page 88. S. Ihe method of sepaiating, from each other, the metallic oxyds, usually found as the colouring ingredients ot .stones, remains to he accomplished. {a) Let the precipitate, by the prqssiate of .potash (D) be exposed to a red heat; by which the prussic acid will be decomposed. The oxyds, thus obtained, if insoluble in dilute .nitric or muri-ati'C acid, will be rendered so by a^ain calcining them with the addition of a huie wax or oil. (b) Or the piocess may be varied by omitting the precipitation b) prussiaie of potash, and proceeding as directed, K. page i^y. The oxyds will remain mixed with the magnesia and lime j and after the addition of sulphuric acid, will be held in solution by that acid, along will* magnesia only. In both cases, the Fame method of proceeding may be adopted, such variation only being neces- sary, as is occasioned by the presence of magnesia in the latter. (c) To the solution (a or b), containing several metallic oxyds dissolved by an acid, add a solution pf crystallized carbonate of poia-sn, as long as any precipitation ensues. This wi'.l t>< paiate the oxyds of iron, chrome, and nick-el; but tire oxyn of man- ganese, and the magnesia, if any be present, will remain dissolved. (d) Magnesia, and oxyd of manganese, may be separated, by adding to their solution (c) the hydro- sulphuret of potash (see p. 6c^ JF,), whicii will 165 throw down the manganese, but not the magnesia. The precipitated manganese must be calcined with the access of air; and weighed. The magnesia may afterward be separated by solution of pure potash -j and when precipitated, must be washed, dried, and calcined. (e) The cxyd of chrome may be separated, from those of iron and nickel, by repeatedly boiling the three, to dryness, with nitric acid. This will acidify the. chrome, and will render it soluble in pure pot- ash, which does not take up the other oxyds. From this combination with potash, the chromic oxyd may be detached, by adding muriatic acid, and evaporat- ing the liquor, till it assumes a green colour. Then, on adding a solution of pure potash, the oxyd of chrome will fall down, because the quantity of oxygen, required for its acidification,, has been se- parated by the muriatic acid. (f) The oxyds of iron and nickel are next to be dissolved in muriatic acid j and to the solution, pure liquid ammonia is tobe added, till there is an evident excess of it. The oxyd of iron will be precipitated ; and must be dried and weighed. The oxyd of nickel remains dissolved by the excess of ammonia, to which it imparts a blue colour. It may be "sepa- rated by evaporating the solution to dryness, and dissolving the salt. The analysis of the stone is now completed, and its accuracy may be judged, by the correspondence of the weight of the component parts, wish that af the stone, originally submitted to experiment. It may be proper to observe, that certain stones, which 'are not soluble in diluted nitric and muriatic acids, may be decomposed by an easier process than that described A. Among these, are the compounds of barytes, strontites,. and lime, with acids, chirily with the sulphuric, fluoric, and phosphoric. 1i}?> 166 n lp hates of barytes, strontites, and lime j the flu ate of lime; and the phosphate of lime, are a 1 ! found native in the earth, and, except the last, are all insoluble in the above-mentioned acids. They may be known .generally by their external characters. The compounds of barytes and strontites have a specific gravity greater than that of other earths, but infeiior to that of metallic ores. They have, frequently, a regular or crystallized form; are more or less transparent; have some lustre; and their hardness is such as does not prevent their yielding to . the knife. The combinations of lime, with the above mentioned acids, are distinguished by similar cha- racters, except that they are much less heavy. To the mineralogist, the outward form and characters of these stones are sufficient indications of their composition. Instead of the fusion with alcali, an easier pro- cess may be recommended. Let the mineral, under examination, be reduced to powder, and be di- .gested, in nearly a boiling heat, during one or two hours, with three or four times its weight of carbonaie of potash, and a sufficient quantity of distilled water. The acid, united with the earth, will quit it, and pass to the potash; while the carbonic acid will Jeave the alcali, and combine with the earth. We shall obtain, therefore, a compound of the acid of" the stone with potash, which will remain in solution, while the carbonated earths will form an insoluble .precipitate. 1 he solution mny be assayed, to dis- cover the nature of the acid, according to th,e formula I; and the earths may be separated from each other by the processes B, &c. T. In the foregoing rule ;-, for analysis, I have omit- td t lie mode of detecting and separating giir.itic,; because this" earth is of very rare occurrence. Whep alumjne and glugiae are present ,in 41 mineral. rer they may be separated from the precipitate (E. a.) by pure potash, which dissolves both these earths. A sufficient quantity of acid -is then to be added to saturate the alcali ; and carbonate of ammonia is to be poured' in, till a considerable excess of this car- bonate is manifested by the smell. The alumine is thus separated; but the glucine, being soluble in the carbonate of ammonia, remains dissolved, and may be precipitated by boiling the solution. U. The presence of potash (which has lately been discovered in some stones) may be detected, by boiling the powdered mineral, repeatedly, to dry- ness, with strong sulphuric acid. Wash the dry mass with water ; add' a little excess of acid j and evaporate the solution to a .smaller bulk. If crystals of alum should appear, it is- a decisive proof of potash, because this- salt can never be obtained in a crystallized form, without the addition of the vege- table aJca-li. But, since a mineral may contain potash, and little or no alumine, in which case no crystals of alum will appear, it may be necessary, in the latter case,, to add a little alumine, along with the sulphuric acid. Or the stone may be so hard as to resist the action of sulphuric acid; and it will then be neces- sary to fuse it, (in the manner directed I) with soda, which has also a solvent power over alumine and silex. The fused mass is to be dissolved in water j and supersaturated \vith sulphuricacid. Evaporateto dry ness ; redissolve in water; and fill re, to separate the silex. Evaporate the solution, which \\ill first afford crystals of sulphate of soda, and afterwards of sulphate of alumine, should this alcali be con- tained in the mineral. The potash, contained in sulphate of alumine, may be separated from the earth, by adding a solu- tion of pure barytas, as long as any precipitation 168 is produced. The alumine and sulphate of barytes will fall down together, and the potash will remain in solution. Its presence maybe known by the tests, p. 148. II. 2. V. Soda may be detected in a mineral by the follow- ing experiments. Let the powdered stone be treated with sulphuric acid, as in U; wash off the solution,, and add pure ammonia, till the precipitation ceases. Then filtre} evaporate the solution to dry ness ; and raise the heat so as to expel the sulphate of ammo- nia. The sulphate of soda will remain, and may be known by the characters, page 57. III. ANALYSIS OF INFLAMMABLE FOSSILS. The exact analysts of inflammable fossils is seldom necessary in directing the most beneficial application of them. It may be proper however to offer a few general rules for judging of their purity. I. SULPHUR Sulphur should be entirely vola- tilized, by distillation in a glass retort. If any thing remain fixed, it must be considered as an impurity, and may be examined by the preceding rules. Sulphur, also, should be totally dissolved by boil- ing with solution of pure potash, and may be separated from its impurities by this alcali. 2. COALS. j. The proportion of bituminous matter in coal may be learnt by distillation in an earthen retort, and collecting the product. 2 .The proportion of earthy or metallic ingredients may be found, by burning the coal, with access of air, on a red hot iron. What remains unconsumed must be considered as an impurity, and may be analyzed by the foregoing rules. 169 . The proportion of carbon may be acertained, by observing the quantity of nitrate of potash, which a given weight of the coal is capable of decomposing. For this purpose, let 500 grains or more of perfectly pure nitre be melted in a crucible, arc! when red hot, let the coal to be examined, reduced to a coarse powder, be pro- jected on the nitre, by small portions at once, not exceeding one or two grains. Immediately, when the flame occasioned by one projection has ceased, let another be made; and so on till the effect ceases. The proportion of carbon in the coal is directly proportionate to the quantity required toalcalize the nitre. Thus since 12.709 of carbon are required toalcalize 100 of nitre, it will be easy to deduce the quantity of carbon in a given weight of coal, from the quantity of nitre, which it is capable of decomposing. This method, however, is liable to several objections, which its inventor, Mr. Kirwan, seems fully aware of. See his Elements of Minera- logy, Vol. II. p. $14. PLUMBAGO, or BLACK LEAD, is another in- flammable substance, which it may sometimes be highly useful to be able to identify, and to judge of its purity. When projected on red hot nitre, it should detonate ; and on dissolving the decomposed nitre, an oxyd of iron should remain, amounting to one tenth the weight of the plumbago. Any mineral, therefore, that answers to these characters .j and leaves a shining trace on paper, like that of the black lead pencils, is plumbago. IV ANALYSIS OF METALLIC ORES. The cla e s of metals comprehends so great a number of individuals, that it is almost impossible to offer a comprehensive formula for the analysis of ores. Yet some general directions are absolutely 170 necessary, to enable the naturalist to judge of the composition of bodies of this class. The ores of metals may be analyzed in two modes, in the humid and the dry way. The first is effected with the aid of acids and of other liquid agents j and may often be accomplished by persons who are prevented, by the want of furnaces and other neces- sary apparatus, from attempting the second. It is hardly possible to employ a solvent capable of taking up all the metals. Thus, the nitric acid does not act on gold or platina ; and the nitro- rmiriatic, which dissolves these metals, has no solvent action on silver. It will be necessary therefore to vary the solvent, according to the nature of the ore tinder examination. FOR ORES OF GOLD AND PLATINA, the nitro- muriatic acid is the most proper solvent. A given v/eiglit of the ore may be digested with this acid, as lung as it extracts any thing. The solution may be evaporated to dryness, in order to expel the excess of acid ; and dissolved in water. The addition of a solution of tin in muriatic acid will shew the presence of gold, by the purple precipitate; and platina will be indicated by a precipitate, on adding a solution of muriate of ammonia. When gold and platina are both contained in the same solution; ^ they may be separated from each other, by the last- mentioned solution, which throws down the platina but not the gold. Jn this way platina may be detached, also, from other metals. When gold is contained in a solution, along with several other metals, it may be separated from most of them, by adding a dilute solution of sulphate of iron The only metals, which this salt precipitates, are gold, silver and mercury. For extracting SILVER from its ores, the nitrid acid is the must proper solvent. The silvermay beprecipi- 171 fated by muriate ofsoda(common salt). Every hundred parts of the precipitate contain 75 of silver. But as lead may be present in the solution ; and this metal is, also, precipitated by muriate of soda, it may be proper to immerse in the solution (which should not have any excess of acid) a polished plate of copper. This will precipitate the silver, if present, in a metallic form. The muriate of silver is also soluble in liquid ammonia, which thafof lead is not. COPPER ORES may be analyzed by boiling them \vith five times their weight of concentrated sul- phuric acid, till a dry mass is obtained, from which! water will extract the sulphate of copper. This salt is to be decomposed by a polished plate of iron, immersed in a dilute solution of it. The copper will be precipitated in a metallic state, and may be scraped off, and weighed. If silver be suspected along with copper, nitrons acid must be employed as the solvent; and a plate of polished copper will detect the- silver. IRON ORES may be dissolved in dilute muriatic acid, or, if too highly oxydated to be dissolved by this acid, they must be previously mixed with one eighth their weight of powdered charcoal, and calcined in a crucible for one hour. The iron is thus rendered soluble. The solution must then be diluted with 10 or 12, times its quantity of water, previously well boiled^ to expel the air, and must be preserved in a well Stopped glass bottle, for six or eight days The phosphate of iron will, within that time, be preci- pitated, if any be present, and the lujuor must be decanted off The solution may contain the oxyds of iron, manganese, and zinc, it may be precipitated by carbonate of soda, which will separate them all. The oxyd of zinc will be taken up, by a solution v z 172 of pare ammonia ; distilled vinegar will take up the manganese; and will leave the oxyd: of iron. From the weight of this, after ignition, during a quarter of an hour, 28 percent, may be deducted. The remainder shows the quantity of iron. TIN ORES. No successful mode of analyzing these, in the humid way, has hitherto been disco- vered. The presence of tin in an ore is indicated by a purple precipitate, on mixing its solution in muriatic acid, with one of gold in nitre-muriatic acid. LEAD ORES may be. analyzed by solution fn nitric acid, diluted with an equal weight of water. The sulphur, if any, will remain undissolved. Let the solution be precipitated by carbonate of soda. If any silver be present, it will be taken up by pure liquid ammonia. Wash off the excess of ammonia by distilled water ; and add concentrated sulphuric acid, applying heat, so that the muriatic acid may be wholly expelled. Weigh the sulphate of lead, and after deducting 70 per cent, the remainder shows the quantity of lead, MERCURY may be delected in ores that are sup- posed to contain it ; by distillation in an earthen retort with half their weight of iron filings Or lime. The mercury, if any be present, will rise, and be condensed in the receiver. ORES OF ZING may be digested with the nitric acid, and the part that is dissolved, boiled to dry- ness j again dissolved in the acid, and again eva- porated. By this means the, iron, if any be present, will be rendered insoluble in dilute rime acid, which will take up the oxyd of zinc To this so- lution, add pure liquid ammonia in excess, which will separate the lead, and iron if any should have been dissolved , and the excess of alkali will retain 173 the oxyd of zinc. This may be separated by the addition of an acid. ANTIMONIAL ORES'. Dissolve a given weight, in three or four parts of muriatic and one of nitric acid This will take up the antimony, and leave the sulphur, if any. On dilution with water, the oxyd of antimony is precipitated, and the iron and mercury remain dissolved. Lead may be detected by sulphuric acid. OKKS OF AKSKNIC may be digested with nitro- muriatic acid, composed of one part nitrous, and one and a half, or two, of muriatic. Evaporate the solution to one fourth ; and add water, which' will precipitate the arsenic. The iron may after- wards be separated by ammonia. ORES OF BtSMUTH'are also assayed, by digestion in nitric acid, moderately diluted. The addition of water precipitates the oxyd, and if not wholly ^epa- rated at first, evaporate the solution ; after which a further addition of water will precipitate 'the remainder. ORES OF COBALT may be dissolved in nitro-mu- riatic acid. Then add cnrbon.u^ of potash, whic.-,,. at first, separates iron and arsenic. Filrre and add a further quantity of the carbona e, when a grevish red precipitate will fall down, winch is oxyd of cobalt. The iron and arsenic miy be separated by heat, which volatilizes the ar-enic Cobalt is a!s>, ascertained, if the solution ot an ori* in muriatic acid give a sympathetic ink ; NCC p 1 15. ORES OF NICKEL'. Dissolve ihi-in in nitric acid $, and add to the solution pure iimmon a, in surli 1 proportion that the alcah mav hr ouMde-ah y in excess. This will precipitate other m<-ui*. and will retain the oxyd of nickel in solution, which m \\ be obtained by evaporation to dryne^s and hexing h& dry mass, till the nitrate of ammonia lias subauicu* p 3 174 ORES OF MANGANESE. The earths, and several of the metals, contained in this ore, may first be separated by diluted nitric acid, which does not act on highly oxydated manganese. The ore may af- terward be digested with strong muriatic acid, which will take up the oxyd of manganese. Oxy- genated muriatic acid will arise, if a gentle heat be applied, and may be known by its peculiar smell, and by its discharging the colour of wet litmus pa- per, exposed to the fumes. From muriatic acid, the manganese is'precipitated by carbonate of soda, in the form of a white oxyd, which becomes black when heated in a crucible. Ores, suspected to con- tain manganese, may also be distilled per se, or with sulphuric acid, when oxygenous gas will be obtain- ed. Oxyd of manganese may be separated from oxyd of iron, by solution of pure potash, which takes up the former but not the latter. Ores of manganese may, also, be distinguished, by the colour they impart to borax, when exposed to- gether to the blow pipe. See p. 1 14. ORES OF URANITE. These may be dissolved in dilute nitric acid, which lakes up the uranitic oxyd, and leaves that of iron ; or in dilute sulphuric acid, which makes the same election. Or if any iron has got into the solution, it may be precipitated by zinc. Then add caustic potash, which throws down the oxyds of zinc and uranium. The former may be separated by digr&iion in pure ammonia, which leaves, undissolved, the oxyd of uranite. This-, when dissolved by dilute sulphuric acid, affords, on eva- poration, crystals of a lemon yellow colour. If copper be present, it will be dissolved, along with the zinc, by the ammonia. If lead, itwill form with sulphuric acid a salt much less soluble than th& sulphate of uranite, and which, on evaporation, *wiil, therefore,, separate first, 175 ORES or TUNGSTEN. For these, the most pro- per treatment seems to be digestion in nitro muria- tic acid, which takf-s up the earths, and other me- tals. The tungsten remains, in the form of a yel- towoxyd, distin . uishable by its becoming white,- on the addition of liquid ammonia, from the oxyd of uranite. To reduce this oxyd to tungstenite, mix it with an equal weight of dried blood ; heat the mixture to redness; press it into another crucible, which should be nearly full ; and apply, a violent heat, for an hour^at least. OKES OF MOLYBDENA. Repeated distillation to dryness, with nitric acid, converts the oxyd into aa acid; which is insoluble in nitric acid, and may be thus separated from other metals except iron, from which it may be dissolved by sulphuric or muriatic acids. The solution in sulphuric acid is blue when cold, but colourless when heated. That in muriatic acid is only blue, when the acid is heated and con eentrated. ANALYSIS OF ORES IN THE DRY WAY. To analyze ores in the dry way, a method which affords the most satisfactory evidence of their compo- sition, and should always precede the working of large and expensive strata, a more complicated ap- paratus is required. An assaying furnace, witli muffles, crucibles, &c. are absolutely necessary ; but as these may be found described in most ele- mentary books, 1 shall omit the detail of them in this place The reduction of an ore requires, frequently, previously roasting to expel the sulphur, ;-nd other volatile ingredients. Or this may be effected, by mixing the powdered ore with nitre, and project- ing the mix lure into a crucible. The sulphate of 176 potash thus formed, may be washed ofFj and the oxyd must be reserved for subsequent experiments. As many of the metals retain their oxygen so forcibly, that the application of heat is incapable. of expelling i', the addition of inflammable matter becomes expedient. And to enable the reduced particles of met^l to agglutinate and form a collected mass, instead of scattered grains, vh'cli would otherwise happfcn, some fusible ingredient must be added, through which, when in fusion, the reduced metal may descend, and be collected at the bottom of the crucible. Substances, th: t answer both these purposes, are called / a crucible, one part of powdered lime, one part of fluate of lime, and half a part of charcoal: Or four hundred parts of calcined borax, forty of lime, and fifty of charcoal : Or two parts of pounded glass, one of borax, and half a part of charcoal, are all well adapted to the purpose of fluxes. The ore, after being roasted, if necessary, is to be well mixed with three or four times its weight of the flux, ami put into a crucible, with a little powdered charcoal over the surface. A cover rmvst be luted on ; and the crucible exposed to the necessary heat in a < wittd furnace. Ores of Acidum Nitrosiim, Pharm. Land. Aquafortis. The nitric acid should be perfectly colourless and as limpid as water. It should be preserved in a dark place ; to prevent its conversion into the nitrous kind. These acids are most likely to be adulterated with sulphuric and muriatic acids. The sulphuric acid may be discovered by adding to a portion of the acid, largely diluted, nitrated or muriated barytes, which occasion, with sulphuric acid, a white and insoluble precipitate. The muriatic acid may be ascertained by nitrate of silver, which affords a sediment, at first white, but which becomes coloured, by ex- posure to the direct light of the sun. Both these acids, however, may be present at once; and. in this case, it will be necessary to add a solution of* nitrate of barytes, as long as any precipitate falls, which will separate the sulphuric acid. Let the sediment subside ; decant the clear liquor; and add the nitrate of silver. If a precipitate appear, mu- riatic acid may be inferred to be present also. Mu- riatic acid may, also, be detected by adding a solu- tion of sulphate of silver. These acids should have the specific gravity of 1550. 3. Muriatic Acid Acidum Muriaticum, P. L, Spirit of Salt. This acid generally contains iron, which may be known by its yellow colour, the pure acid being 186 perfectly colourless. It may also be detected by the same mode, as was recommended in examining sulphuric acid. Sulphuric acid is discoverable by a precipitation, on adding to a portion of the acid, diluted with five or six parts of pure water, a solution of the muriate of barytes. The specific gravity of this acid should be 1170. 4. Acetic Acid Acidnm Acetosum, P. L. Radical or concentrated Vinegar. This acid is often contaminated by sulphureous and sulphuric acid. The first may be known by drawing a little of the vapour into the lungs, when if the acid be puie, no unpleasant sensation will be lelt j but, if sulphureous acid be contained in the acetic, it will not fail to be discovered in this mode. The sulphuric acid is detected by muriated barytts: Copper by super-saturation with pure ammonia: And lead by sulphuret of ammonia. The specific, gravity of this acid should be 1050 at least. $*. Acetous acid Aceti.m Distillatum, P. L. Distilled Vinegar. If vinegnr be distilled in topper vessels, it can hardly fail being contaminated by that metal ; and if a leaden worm be used, for its condensation, some portion of lead will certainly be dissolved. The former metal will appear, on adding an excess of solution of pure ammonia; and lead will be de- tected by the sulphurated ammonia, or by water saturated with sulphurated hydrogen. It is not unusual, in order to increase the acid tnste of vinegar, to add sulphuric acid. This acid may be immediately discovered, by solutions of 187 barytes, which, when vinegar has been thus adul- terated, throw down a white precipitate. 6. Boracic acid Sedative Salt of Homberg. Genuine boracic acid should totally dissolve in five times its weight of boiling alcohol -, and the solution,, when set on fire, should emit a green fiame. The best boracic acid forms small hexangular scaly crystals, of a shining silvery white colour. Its specific gravity is 1480. 7. Tartarons Acid. This acid often contains sulphuric acid, to discover which, let a portion be dissolved in water, and a solution of acetire of lead be added. A precipitate will appear, which if the acid be pure, is entirely redissolved by a few drops of pure nitric acid, or by a little pure acetic acid. If any portion remain undissolved, sulphuric acid is the cause. Muriate of barytes, also, when the acid is adulterated with sul- phuric acid, but not otherwise, gives a precipitate insoluble by an excess of muriatic acid. 8. Acid of Amber. Acid of amber is adulterated, sometimes with Sulphuric acid and its combinations; sometimes with tartareous acid j and at others with muriate of ammonia. Sulphuric acid is detected by solutions of barytes ; tartareous acid by carbonate of potash, which fo.ms a difficultly soluble tartrite; and muriate of ammonia by nitrate of silver, which discovers the acid, and by a solution of pure potash, which excites a strong smell of ammonia. 188 Pure acid of amber is a crystalline white salt; of an acid taste ; soluble in twenty-four parts of cold and eight of hot water ; and is volatilized when laid on red hot iron, without leaving any ashes or other residue. 9. Acid of Benzoin Flores Be?iwes, P. L. This acid is not very liable to adulteration. The best has a brilliant white colour, and a peculiarly grateful smell. It is soluble in a large quantity of boiling water or alcohol -, and leaves no residue, when placed on a heated iron. 10. Carbonate of Potash. Kali Preparation, P. Z. The salt of tartar of the shops generally contains sulphate and muriate of potash, and siliceous and calcareous earths. It should dissolve entirely if pure, in twice its weight of cold water; and any thing, that remains undissolved, may be regarded as an impurity. Sometimes one fourth of foreign ad- mixtures may thus be detected, the greater part of which is sulphate of potash. To ascertain the nature of the adulteration, dissolve a portion in pure and diluted nitric acid. The siliceous earth only will remain undissolved. Add, to one portion of the solution, nitrate of barytes. This will detect sulphate of potash by a copious precipitate. To another portion add nitrate of silver, which will discover muriatic salts ; and to a third oxalate or fluate of ammonia, which will detect calcareous earth. The solution of carbonate of potash (Aqua Kali, P. L.) may be examined in a similar manner. 189 1 1 . Solutio?i of pure Potash Aqua Kali Puri, P. L. This may be assayed for sulphuric and muriatic salts by saturation with nitric acid, and by the tests, recommended in speaking of carbonate of potash. A perfectly pure solution of potash should remain transparent, on the addition of barytic water. If a precipitate should ensue, which dissolves, with effervescence, in dilute muriatic acid, it is owing to the presence of carbonic acid j if the precipitate is not soluble, it indicates sulphuric acid. A redun- dancy of carbonic acid is, also, shewn by an effer- vescence on adding diluted sulphuric acid ; and an excess of lime, by a white precipitate, on blow- ing air, from the lungs, through the" solution, by means of a tobacco pipe, or a glass tube. l This solution should be of such a strength, as that an exact wine pint may weigh 18 ounces troy. 12 Carbonate of Soda Natron Preparation, P. L. Carbonate of soda is scarcely ever found free from muriate and sulphate of soda. These may be dis- covered by adding, to a little of the carbonate satu- rated with pure nitric acid, first nitrate of barytes, to detect sulphuric acid 3 and afterward nitrate of silver, to ascertain the presence of muriatic acid. Carbonate of potash will be shown by a precipitate ensuing, on the addition of tartarous acid to a strong solution of the alcalij for this acid forms a dif- ficultly soluble salt with potash, but not with soda. 13. Solution of Carbonate of Ammonia Aqua Ammonia, P. L. This should have the specific gravity of ujo; should effervesce on the addition of acids ; and should afford a strong coagulum, on adding alcohol. 190 II. Carbonate of Ammonia Ammonia Preparata. P. L. This salt should be entirely volatilized by heat. If any thing remain, when it is laid on a heated iron, carbonate of potash or of lime may be suspected j and these impurities are most like)y to be present, if the carbonate of ammonia be purchased in the form of a povvder. It should therefore always be bought in solid lumps. Sulphuric and muriatic salts, lime, andiron may be discovered by adding to the alkali, saturated with nitric acid, the appro- priate tests, already often mentioned. 15. Solution of Pure Ammonia in Water Aqua Am- monite Pur F&wers oj Zinc. Oxyd of zinc may be adulterated with chalk, which is discoverable by an effervescence with acetous acid, and by the precipitation of this solu- tion with oxalic acid. Lead is detected by adding, to the acetous solution, sulphurated water, or sul- phuret of ammonia. Arsenic, to which the activity of this medicine has been sometimes ascribed, is detected, also, by sulphurated water, added to the acetous solution, but in this case the precipitate has a yellow colour ; and when laid, on red hot char- coal, gives first a smell of a sulphur, and afterwards of arsenic. 42. JHiile Oxyd of Lead. Cerussa, P . L. White Lead. This is frequently sophisticated with chalk, the presence of which may be detected by cold acetous acid, and by adding, to [his solution, oxalic acid. Carbonate of baryirs is detected by sulphate of soda added to the same solution, very largely diluted with distilled water; and sulphate of barytes or sulphate of lead, by the insolubility of the cerusse in distilled vinegar. 43. Acetite of Lead, -^- Cerussa Acetata, P. L. Sugar of Load. If the acelite of lend should be adulterated with acetite of lime or of barytes, the former may be detected by adding, to a dilute solution, the oxalic acid; and the latter by sulphuric acid, or solution of sulphate of soda, added to a solution very largely diluted with water. Acetite of lead ought to dis- solve entirely in water; and any thing that resists solution may be regarded as an impurity. 201 ^. Green Oxyd of Copper This oxyd is scarcely ever found pure, being mixed with pieces of copper, 'grape stalks, and other impurities. The amount of this admixture of insoluble substances may be ascertained, by boil- ing a portion of verdegris, with 12 or 14 times it? weight of distilled vinegar 5 allowing the undis- solved part to settle; and ascertaining its weight. Sulphate of copper may be detected, by boiling the ^verdegris with water, and evaporating the solution. Crystals of acetite of copper will first separate ; and, when the solution ha-s been further concentrated, the sulphate of copper will crystallize. Or it may oe dis- covered, by adding, to the watery solution, muria't'e of barytes, which will throw down a very abundant precipitate. Tartrite of copper, another adultera- tion sometimes met with, is discovered by dis- solving a little of the verdegris in acetous acid, and adding acetite or muriate of barytes, which will afford with the tartarous acid a precipitate, soluble in muriatic acid, 45- Crystallized Acetite of Copper. Distilled, ar Crystallized t 7 croegris. This is prepared by dissolving the common verde- gris in distilled vinegar, and crystallizing the solar- lion. These crystals should dissolve entirely in six times their weight of boiling wa=ter ; and the solu- tion should give no precipitation with solutions of barytes; for, it these solutions throw down a pre- cipitate, sulphate of copper, is indicated. Thus impurity, which I have frequently met with, may be discovered, by evaporating the solution very low, and separating the crystals of acetite of copper. 202 Further evaporation acd cooling will crystallize the sulphate, if any be present. 46. Carbonate of Mag?iesi&. Magnesia Atba y P. L. Carbonate of rnngnesia is most liable to adultera- tion with chalk $ and as lime forms with sulphuric acid a very insoluble salt, and magnesia one very readily dissolved, this acid may be employed in detecting the fraud. To a suspected portion of magnesia, add a little sulphuric acid, diluted with 8 or jo times its weight of water. If the magnesia should entirely be taken up, and the solution shoula remain transparent, it may be pronounced purej hut not otherwise Another mode of disco- vering the deception is as follows. Saturate a por* lion of the suspected magnesia with muriatic acid f and add a solution of carbonate of ammonia. If any lime be present, it will form an insoluble preci- pitate, but the magnesia will remain in solution. 47. Pure Magnesia, Magnesia Usict, P. L ic ed Manesia. Calcined magnesia maybe assayed by 1 he same tests as the carbonate. It ought not to effervesce at all with dilute sulphuric acid ; and, if the earth and acid be put together inio one scale of a balance, no diminution of weight should ensue on mixing them together. It should be perfectly free from taste, and when digested with distilled water, the filtered liquor should manifest no property of lime water. Calcined magnesia, however, is very seldom so pure as to be totally dissolved by diluted sulphuric acid; for a small insoluble residue gene- rally remains, consisting chiefly of : siliceous earth, derived from the alkali, The solution in sulphuric 203 acid, when largely diluted, ought not to afford any precipitation with oxalate of ammonia. 48. Spirit of Win*} ; Alcohol; and jEthers. The only decisive mode of ascertaining the purity of spirit of wine and of ethers, is by determining their specific gravity. Highly rectified alcohol should have the specific gravity of 829 to 1000. Common spirit of wine 837. Sulphuric ether 739. The spiritus zetheris vitriolicus, P L., or sweet spirit of vitriol, about 753 and nitric ether, the spiritus etheris nitrosus, or sweet spirit of nitre, 908. The ethers ought not to redden the colour of lit- mus ', nor ought those, formed from sulphuric acid, to give any precipitation with solutions of bary tes. 49. Essential or Volatile Oils. As essential oils constitute only a very small proportion of the vegetables, from which they are ob- tained, and bear generally a very high price, there is a considerable temptation to adulterate them. They are found sophisticated, cither with cheaper- volatile oils, with fixed oils, or with spirit of wine. The fixed oils are discovered, by distillation with a very gentle heat, which elevates the essential oils, and leaves the fixed ones. These Inst may, also, be detected by moistening a little writing paperwith the suspected oil, and holding it before the fire. If the oil be entirely essential, no stain will remain on the paper. Alcohol, also, detects the fixed oils, because it only dissolves the essential ones ; and the mixture becomes milky The presence of cheaper essential oils is discovered by the smell. Alcohol, a cheaper liquid than some of the most costly oils, is discovered by adding water, which, if alcohol be present, occasions a milkiness. 204 SECT. III. USE OF CHEMICAL REAGENTS TO CERTAIN ARTISTS AND MANUFACTURERS. To point out all the beneficial applications of chemical substances to the purposes of the arts, would require a distinct and very extensive treatise. In this place, I have no further view than to describe the mode of detecting adulterations in certain articles of commerce, the strength and purity of which are essential to the success of chemical pro- cesses. I . Mode of detecting the Adulteration of Pot-ashes , Pearl-ashes, and Barilla. Few objects of commerce are sophisticated to a greater extent than the alcalis, to the great loss and injury of the bleacher, the dyer, the glass-maker, the soap-boiler, and of all other artists who are in the habit of employing these substances. In the firft part of this work (see page 48) I have already given rules for discovering such adulterations ; and to -what has been said, 1 apprehend it is only necessary to add the directions of Mr. Kirwan, intended to effect the same end, but differing in the mode. They are transcribed from his paper, entitled " Ex- periments on the Alcaline Substances used in Bleaching ;" see Transactions of the Irish Acade- my for 1789. " i o discover whether any quantity of fixed al- kali worth attention exists in any saline compound, dissolve one ounce of it in boiling water, and into this solution let fall a drop of a solution of subli- mate corrosive ; this will be converted into a brick colour, if an alkali be present, or into a brick co- 205 lour mixed with yellow, if the substance tried con- tains lime. " But the substances used by bleachers being al- ways impregnated with an alkali, the above trial is in general superfluous, except for the purpose of de- tecting lime. The quantity of alkali is therefore what they should chiefly be solicitous to determine, and for this purpose : f< i st. Procure a quantity of alum, suppose one pound, reduce it to powder, wash it with cold wa- ter, and then put it into a tea-pot, pouring on it three or four times its weight of boiling water. " 2dly. Weigh an ounce of the ash or alkaline substance to be tried, powder it, and put it into a Florence flask with one pound of pure water (com- mon water boiled for a quarter of an hour, and afterwards filtered through paper, will answer) if the substance to be examined be of the nature of barilla, or potash ; or half a pound of water if it contain but little earthy matter, as pearl-ash j let them boil for a quarter of an hour : when cool let the solution be filtered into another Florence flask. . <( 4thly. The earth being thus dried, throw it into a Florence flask, and weigh it; then put about one ounce of spirit of salt into another flask, and place this in the same scale as the earth, and counter- balance both in the opposite scale : this being done, pour the spirit of salt gradually into the flask tiiat contains the earth; and when all effervescence is over (if there be any) blow into the flask, and ob- serve what weight must be added to the scale con- taining the flasks, to restore the equilibrium ; sub- tract this weight from that of the earth, the remain- der is a weight exactly proportioned to the weight of mere alkali of that particular species which is contained in one ounce of the substance examined - y all beside is superfluous matter. " I have said that alkalies of the same species may thus be directly compared, because alkalies of differ- ent species cannot but require the intervention of another proportion $ and the reason is, because equal quantities of alkalies of different species precipitate unequal quantities of earth of alum. Thus 100 parts by weight of mere vegetable alkali, precipitate 78 of earth of alum; but 100 parts of wine.ral alkali precipitate 170,8 parts of that earth. There- fore the precipitation of 78 parts of earth of alum by vegetable alkali, denotes as much of this as the precipitation of 170,8 of that earth by the mineral alkali denotes of the mineral alkali. Hence the quantifies of alkali in all the different species of pot-ashes, pearl-ashes, weed or wood-ashes, may be immediately compared with the above test, 35 they all contain the vegetal le alkali 5 and the tiif- 207 fcrent kinds of kelp or kelps manufactured in dif- ferent places, and the different sorts of barilla, may thus be compared, because th^y all contain the mi- neral alkali. But kelps and pot-ashes, as they con- tain different sorts of alkali, can only be compared together by means of the proportion above indi- cated." 2. A'fode of detecting the Adulteration ofMangeniese. In the section on drugs, instructions may be found for discovering impurities in several chemical preparations, employed by the artist, as cerusse or white lead 5 red lead; verdegris, &c. No rules, however, have been given for examining manganese, which is a substance that varies much in quality, and is often sophisticated; as the bleachers experi- ence, to their no small disappointment and loss. The principal defect of manganese arises from the admixture of chalk, which is not always an in- tentional adulteration; but is sometimes found united with it, as it occurs in the earth. When to this impure manganese, mixed with muriate of soda (seepage 73), the sulphuric acid is added, the ma- terials effervesce and swell considerably; and a large proportion passes into the receiver, in conse- quence of which the bleaching liquor is totally spoiled. This misfortune has, to my knowledge, ireque ntly happened ; and can only be prevented by so -low ?nd cautious an addition of the acid, as is nearly inconsistent with the business of an extensive bleaching work. The presence of carbonate of 1 me may be discovered in manganese, by pouring, on a ponion of this substance, nitric acid diluted with 8 or ten parts of water. If the manganese be good, no effervescence will ensue ; nor will the acid dis- solve any thing 5 but if carbonate of lime be present, 208 it will be taken up by the acid. To the solution, add a sufficient quantity of carbonate of potash to precipitate the lime ; wash the sediment with water ; and dry it. its weight will show, how much chalk the manganese under examination contained. Another adulteration of manganes-e, that may, perhaps, be sometimes practised, is the addition of some ores of iron. This impurity is less easily discovered. ]>nt if the iron be in such a state of oxydation as to be soluble in muriatic acid, the following process may discover it. Dissolve a por- tion, with the assistance of heat, in concentrated muriatic acid 5 dilute the solution largely with di- stilled water ; and add a solution of crystallized car- bonate of potash. The manganese will remain suspended by the excess of carbonic acid, on mixing the two solutions ; but the iron will be precipitated in the state of a coloured oxyd. SECT. IV. APPLICATION OF CHEMICAL TESTS TO THE USES OF THE FARMER AND COUNTRY GENTLEMAN. The benefits that might be derived, from the union of chemical skill with extensive observation of agricultural facts, are, perhaps, incalculable. At present, however, the state of knowledge, among farmers, is not such, as to enable them to reap much advantage from chemical experiments : and the chemist has, himself, scarcely ever opportunities of applying his knowledge to practical purposes, in this way. It may, perhaps, however, be of use to offer a few brief directions for the analysis of marls, lime-stones, &c. ; and, on this occasion, I shall owe much of my information, as in various other parts of this work, to the writings of Mr. Kirwan, whose 209 pamphlet on philosophical agriculture, I strongly recommend to general perusal'*. I. LIME. It is impossible to lay down any general rules respecting the fitness of lime for the purposes of agriculture, because much must depend on the pecu- liarities of soil, exposure, and other circumstances. Hence a species of lime may be extremely \vell adapted for one kind of land, and not for another. All that can be accomplished by chemical means, is to ascertain the degree of purity of thci lime, and to infer, from this, to what kind of soil it is best adapted. Thus a lime, which contains much argillaceous earth, is belter adapted, than a purer one, to dry and gravelly soils ; and stiff clayey lands require a lime as free as possible from the argillaceous ingredient. To determine the purity of lime, let a given weight be dissolved in diluted muriatic acid. Let a little excess of acid be added, that no portion may remain undissolved, owing to the deficiency of the solvent. Dilute with distilled water ; let the insolu- ble part, if any, subside; and the clear liquor be decanted. Wash the sediment with further portions of water 5 and pour it upon a filtre previously weighed. Dry the nitre, and ascertain its increase of weight, which will indicate how much insoluble matter, the quantity of lime, submitted to experi- ment, contained. It is easy to judge, by the exter- nal qualities of the insoluble portion, whether argil- laceous earth abounds in its composition. * It is entitled 661b.and if to 5,66 Ib. there be- long 1 2 ozs of stone, to ilb. must belong 2, 1 2014 ozs. or 2 ozs 57,66 grs.n: 1017 ,66 grs. This then is the stoney supplement of each succeeding pound S. " 3' Of the earth thus freed from stoney matter, take i Ib >S r . (thai is intheabovecaie ilb 2oz-57-| grs.) heat it nearly to redness in a flat vessel, otten stirring it for half an hour, and weigh it again when cold. Its loss of weight will indicate the quantity of water contained in lib. of the soli. Note this * Troy weights are generally more exactly made truin avoir- C:;'pu'S, and therefore should be preferred. A cubic foot oi pine \vater weighs 75,945 troy, very rteaiiv, or 6'2,5 avoirdupois poundj, at die temperature G'2 r< 215 loss, and call it the watery supplement W. Sup- pose it in this case 100 grains. te 4' Take another pound of the above mass freed from stones, deducting the stoney and watery supplements ; that is, i Ib. S W, or in the above case lib. 2 oz, $7ygrs. for stone, and icogrs. for water: consequently lib. 2 oz. 157! grs. re- duce it to powder : boil it in four times its weight of distilled water for half an hour ; when cool, pour it off, first into a coarse linen filtre to catch the fibrous particles of roots, and then through paper, to catch the finer clayey particles diffused through it : set by the clear water, add what remains on the filtre to the boiled mass j if it be insipid, as I sup- pose it to be, then weigh the fibrous matter, and call it the. Jihrous supplement^]?. Suppose it in the example in hand to weigh logrs. " 5- Take two other pounds of the mass fr^ed from stoney matter, No II. subtracting from them the weight of the stoney, watery, and fibrous sub- stances already found ; that is, zlb 28 2\V 2-F 5 pour twice their weight of w*.rm distilled water on them, and let them stand twenty-four hours or longer j that is, until the water has acquired a colour, then pour it off and add more water as long as it changes colour j afterwards filtre the coloured water and evaporate it to a pint, or half a pint; set it in a cool place for three days, then take out the saline matter, if any be found, and set it by. " 6* Examine the liquor out of which the salts have been taken ; if it does not effervesce with the marine acid, evaporate it to dryness, and weigh the residuum ; if it does effervesce with acids, saturate it with the vitriolic or marine, and evaporate it to one fourth of the whole ; when cool, take out the saline residuum, evaporate the remainder to dryness, and weigh it 5 this gives the coaly matter, which may be tried by projecting it on melted nitre, with 216 which it will deflagrate. The half of this coaly matter call the coaly supplement of i Ib. I shall sup- pose it to amount to 12 grs. and denote it by C. " 7' The filtred water, No .IV. is next to be gently evaporated to nearly one pint, and then suffered to rest for three days in a cool place, that it may deposit its saline contents, if it contains any ; and these being taken out, the remainder must be evaporated nearly to dryness, and its saline and other contents examined. Flow this should be done, I shall not mention, the methods being too various, tedious, and of too little consequence ; few salts occur except gypsum, which is easily distinguished. The water may be examined as to its saline contents when it is evaporated to a pint ; if any salts be found, call them the saline supplement, and denote them by S. I shall suppose them here = 4 grains. " 8 9 . We now return to the boiled earthy resi- duum, No. IV. which we shall suppose fully freed from its saline matter, as, if it be not, it may easily be rendered so, by adding more hot water : let it then be dried as in No. III. is mentioned. Of this earthy matter thus dried, weigh off one ounce, deducting one- twelfth part of each of the supple-, ments 6. ll- r . F. C. and ; that is, in this 1017.66 100 10 case* 84,40544- =8,3334 -f- 12 12 12 12 4 =0,8333 -f =i -f - 0,3333 95 grs. 12 12 in all : then 480 95 385 grains will remain, and represent the mere earthy matter in an ounce of the soil. - " 9. Let this remainder be gradually thrown into a Florence flask, holding one and an half as much epirit of nitre as the earth weighs, and also diluted 217 with its own weight of water (the acids should be freed from all contamination, of t,he vi- triolic acid) : the next day the flask with its con- tents being again weighed, the difference between the weights of the ingredients and t(ie weights now found, will express 'he quantity pf air that escaped during the solution. Th,us in the above case, the earth weighing 385 .grains, t(ie acid 577,5 grains, and the water c;7>5 grains, in, all 1540 grains, the weight after solution should also be j 540, if nothing escaped : but if the soil contains caicar,epus matter, a loss will always be fo^nd after solution. Let.\is suppose it to amount to 60 grains. " The weight of air that escaped, furnishes us with one method of estimating the quantity pf cal- careous matter contained in the earth essayed ; for mild calx generally contains 40 per ctnt of air^ then if 40 parts air indicate 100 of .calcareous matter, 60 parts air will indicate 150"*. " 10. The solution is then to be carefully poured off, and the undissolved mass washed and shaken in distilled water; the whole thrown on a liltre,, and washed as long as the water that passes through has any taste. The contents of this water should be precipitated by a solution of mild mineral alkali : this precipitate also being washed and dried in a heat below redness, should then be weighed. Thus we have another method of finding the weight of the calcareous matter. " n. The undisaolved mass is next to be dried in the heat already mentioned, and the difference between its weight and the weight of the whole earthy mass before solution should be noted, as it furnishes a third method of discovering the weight of the calcareous matter of which it is now de- * I take no account of iiiagne.iia, as in .agriculture I believe U 6t little importance. T 218 prived. Supposing this to amount to 150 grains, the weight of the undissolved residuum should in the above case be 385 150 235 grains. f injuring thvm 5 and the saaie discharge, AKMU papev, xvrit-uto but not ink* Heue^ they imu* be employed in ei^atiirg books, xvhieh have hcciv d< K,ecd by wraing aii the nirgi.n, \vlihout impairing iht-. trxt. 2. /' <;// Stains. 'I hso n">ay be occasioned etlhflE by ink stains, \i'lii(:l), on tlu* * :pp!]ciition of sf)ap, are changed into iron stains, or by the direct contact of rusted- iion. 1'hey may be. renio\ed by -dilntftl nnniiitic r.cid, or by one of the vegetable acid* nlready mentioned. When stii-lert:ri to IH main long on cloth/ they become extremely diriienlt to take out, because live iron, by repeated moistening with. \\ater, and exposure to iLe air, acquires- such aiu addition of oxygen, as venders it insoluble in acids. J Lave found, hovveier, that even these spots may l>c discharged, by applying iifbt a solution of .ui; alkaline sulphurelj which must be v/ell xvashedt the cloth j and afterwards, a liquid acid. .sulphuret, in this case, extracts part of the oxygen from the iron j and renders it soluble in dilate acids. 3. F;-uit aiid // inc Stains. These are best removed by a watery solution of the oxygenated muriatic aeid. (see p. 74) or by that of oxygenated* muriate of potash or lime, to which a little sulphuric acid has been added. The sunned spot may he steeped in one of these ft Uitions till it is discharged 5 but the solution catior.ly be applied with safety to while goods , because the uncombin^d oxygenated acid, discharges oil printed and dyed colours. A- convenient mode or' applying the oxygenated acid; easily practicable by persons, who have not Hie apparatus for saturating xvater with the gas, is as foUo\vs> Put abtmt a table spoonful of muriatic ae*d (spirit of stU) iota a tea cup, and add to it about a tea spoonful of powdered manganese. Then set this; cup in a larger on tilled with hot water* Moisten the stained spot with water, and expose it to the Amies that arise from the tea cup* if the xpmun- he .continued a r suiiicu'nt length of time* the s?ain will disappear, 4, ^HH'S (>/' G.-'tf^-? may be rm-oved hj a dilated solution of pur potash j but this roust be cautiously applied, U) prevent injury to (he cloth. Stains of vkits wax, which sometimes fall upon the eloaths irom wax caudlc.% are removable by spirit of turpen- tine or sulphuric ether. The marks of uhite pa^nt also be discharged by the last mentioned THE Tinted by J. LIST OF ELEMENTARY BOOKS CHEMISTRY. THE following list comprehends a selection of a few elementary works on Chemistry, which are sufficient for the purpose of the general reader. To have offered such a catalogue, as would compose a complete chemical library, would have occupied too much room ; and perhaps would not have been of much utility, x, Lavoisier's Elements of Chemistry, Svo. 2. Works, from ihf French, by Henry, i vol. Svo. and a pamphlet, 3. Chaptal'g Elements of Chemistry, 3 vols. 8vo. 4. Nicholson's First Principles of Chemistry, Fvo, , .*.. Chemical Dictionary, zvcls. 4to, 6. Thomson's Translation of Fourcroy's Che*- mistry, 3 vols. Svo. 7. Gren's Principles of Chemistry, 2 vols. Svo. 8. La Grange's Manual of Chemistry, 2 vols. Svo. 9. Pearson's Chemical Nomenclature, 2d edi- tion, 4,10. 10. Parkinson's Chemical Pocket Book. It. Nicholson's Philosophical Journal, published monthly. 12. Philosophical Magazine, published monthly. To the above may be added a large work, lately published, in France, by VI. Fourcroy -, and which Mr. Nicholson is now translating, it will be en- titled f> A System of Chemical Knowledge/' and will extend to several 8vo, volumes. OF J.JOHNSON, No. 72, ST. PAULAS CHURCHYARD, LONDON, may be had, A general View of the Nature and Objects of Chemistry, and of its Application to Arts, and Manufactures, by WILLIAM HENRY, 8vo. is. 6d. And the following Works, By Thomas Henry, F.R.S. 8c. 1. An Account of a Method of preserving Water at Sea, 8vo, pamphlet. 2. Experiments and Observations on the follow- ing subjects : 1. On the preparation, calci- nation, and medicinal use of Magnesia. 2. On the solvent qualities of calcined Magnesia. 3. On the variety in the foi- vent powers of quick-lime, when used in different quan- 4. On varijus absorbents as promoting or retarding pu- trefaction. 5. On the comparative an- tiseptic powers of vegeta- table infusions prepared with lime, &c. 6. On the sweetening proper* ties of fixed air. 8vo. price 2s. 6d. 3. Essays Physical and Chemical/by M. Lavoisier, translated from the French, 8vo. 73. 4. Essays on the Effects, produced by various Processes, on Atmospheric Air, with a particular View to an Investigation of the Constitution of Acids, translated from the French of Lavoisier, 8vo. 2s. 6d. N. B. The two foregoing works afford an his- torical view of the progress of pneumatic che- mistry ; and'a full and very interesting develop- ment of those accurate and admirably conceived experiments -of M. Lavoisier, which serve as the basis of the reformed system of chemical science. 5. Memoirs of Albert deHaller. 121110.38^ DESCRIPTION AND PRICES F THE PORTABLE CHEMICAL CHESTS, INVENTED BY WILLIAM HENRY, And sold by him at his Laboratory in Manchester, No. i. A large double mahogany chest, with folding doors, containing eighty-six strong square bottles, with ground and cut stoppers, filled with tests, &c. and so arranged that the labels may be seen at one view ; together with five drawers, in which are various articles of apparatus; accurate scales, decimal weights, improved blow- pipe and spoon, complete ....... 15 guineas. No. 2. A hest of similar construction, but smaller; containing fifty-two bottles, with other articles, as in No. i . ..... 1 1 guineas. No. 3. An upright chest, box shaped, intended chiefly as a travelling companion ; holding thirty- six bottles, with a drawer, containing articles anil apparatus, as in the two foregoing ones 6 guineas and a half. N.B. Any one of the foregoing chests may be had either with or without the scales and blow- pipe. If sold without scales and weights, 16 shillings may be deducted from the foregoing prices j and 14 for the blow-pipe and spoon. The tests are all prepared with the most scru> pulous attention to accuracy ; and supplies may be obtained, by purchasers of the chests, when the stock they contain is exhausted. Letters, containing orders for the chests, which will be sent, carefully packed, to any part of Great- Britain, to be post paid, and a remittance of the value will be expected before the chest is delivered to the carrier. RETURN CIRCULATION DEPARTM 202 Main Library LOAN PERIOD l 2 3 4 5 6 LIBRARY U This book is due before closing time on the last date stc DUE AS STAMPED BELOW FORM NO. 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