She i. B. Hill ICibrarg North (Tarolina &tatp limtiprHtti| TP897 N21 T£X. LIB: 97if/ This book is due on the date indicated below and is subject to an overdue fine as posted at the Circulation Desk. DEC 4 WZ BKAJtY IS^EJtSITY **6£a^#" -xix' T'v *>..4 *u-^*^ Digitized by tlie Internet Arcliive in 2010 witli funding from NCSU Libraries littp://www.arcliive.org/details/manualofartofdyeOOnapi A MANUAL ART OF DYEING. ly ACTIVE PBEPABATIOIf, A MANUAL OF DYEING RECEIPTS, rOE GEKT.RAT. CSC BY JAMES NAPIER, F.C.& ■WTTH KTKEBOUS BAJCFLES OF DTED CXOTBL -^t'^' A MANUAL I NO- \ ART OF DYEING. JAMES NAPIER, F.C.S. ILLUSTRATED BY ENGRAVINGS. GLASGOW : PUBLISHED BY RICHARD GRIFFIN & COMPANY. LONDON : JOHN J. GRIFFIN & CO. 1853. GLASGOW : PEIXTKD BT BELL AKD BAIN. PREFACE. If there be any trade which, more than another, requires the knowledge of first principles, it is that of dyeing, it being essentially progressive. The particular conditions of the trade render information of this description more needful, and therefore more valuable, than ordinary. The trade is what is termed open, so that any man may enter it ; and, in conse- quence, there are few instances where young men are taught the business systematically. A great many enter the trade who are grown up, — their chief ambition being to learn the mechani- cal operations of the dye-house, and when sufficient dexterity in these is attained, to secure the highest rate of wages. When this is accompHshed, zeal for improvement in a great measure subsides. However, there are many who, not content with acquiring a knowledge of the mere mechanical routine, desire to look deeper into the principles of the art, and aim at higher honours than those of a mere labourer in it, but who believe that the means of success consist simply in long and steady service, and a good memory for the rules of manipulation. Both of these are valuable qualifications, but neither of them would be depreciated in the slightest degree by being conjoined with a more extended knowledge of the fundamental prin- ciples of the art than usually faUs to the share of the practical dyer. There is another evil arising out of this condition of of this conditio! 97491 VI PREFACE. the trade. Individuals who attain the position of good work- men value their abilities by the contrast which exists between them and the newly-initiated journeyman ; but they rarely or never look forward to the wide field which lies unexplored before them. Often indeed they boast of their capabiUties, of their expertness, and their knowledge ; and it is no uncommon thing for them to indulge, in petty jealousy, and endeavour to conceal the secret of their mode of working from their neigh- bours. Under these circvunstances it is no wonder that years are often spent — we should say wasted — in endeavouiing to discover what was long before patent to every one who knew the scientific principles of the trade, although ignorant of the practical operations of it. This ignorance of principles often makes both workman and master the dupes of knaves who go about hawking valuable secrets at so much a piece. It must be admitted, however, that notwithstanding aU untoward circumstances, the degree of advancement which the art has attained is truly astonishing. A single practical hint is sometimes sufiicient to cause a complete revolution in some branch of the trade, so that were the principles of chemistry in their appUcation to dyeing but once generally \mderstood by those practically employed, we can hardly conceive what changes and improvements might not be effected. Another circumstance calling for a few remarks is the fluc- tuating state of the trade, which, even in its best condition, throws not less than a fourth part of the workmen idle during the winter months. But while we admit the hardship of such a state of things in its fiillest extent, we do not believe that this time should be allowed to glide by in absolute Hst- lessness. It is still a portion of the allotted span of life, and ought to be turned to all the advantage which circumstances will admit ; and if it can be made subservient to future ad- vantage either by advancing the personal interests, or in aug- menting the mental enjoyment, of the individual, it is surely PREFACE. VU culpable to allow it to run to waste. We sincerely believe that it may be turned to account in both ways, and we promise with some confidence that the following Treatise will suggest the means of deriving remuneration even from idle hours. Lord Bacon's maxim, that " Knowledge is power," has been reiterated till it may be thought to have lost its virtue, but it is still as true as ever, and we are confident that it cannot be more aptly applied than to the case of the practical dyer. From our own experience we are aware that there at present exists a strong desire amongst a great many of those employed in the processes of dyeing to understand the prin- ciples of the art, and to be able to assign reasons for the various changes that take place in producing the colours. Such knowledge is often eagerly sought for without success, both in books and in the lecture-room. The disappointment arises from two sources : first, the inabihty of the dyer to apply chemical principles to his special purposes; and second, a want of practical knowledge in the author or lecturer, which disquaUfies him for pointing out the special applications of the principles he may be defining. These circumstances have long impressed the Author with the opinion that an ap- plication of principles to any practical operation can best be done by an individual working at, or familiar with, all the practical details of that particular operation or trade, and that every branch of trade or art ought to have its own guide-book prepared by one of its own operatives. The carrying out of this idea has induced the Author to publish the present Manual, which is a " System of Chemistry applied TO Dyeixg." Having been himself a practical dyer for many years, and having experienced the difficulties which an unedu- cated man has to contend with in striving to become a Dyer in the proper sense of the term, he has in the following pages endeavoured to clear away some of the technical difficvdties besetting the path of the practical man, and to guide him in viil PREFACE. following out first principles while engaged in experiments to advance his art. The Author acknowledges his obUgations to a few intelli- gent dyers for several practical hints contained in these pages, and which had not come under his own observation. It Avill also be seen in reading the work, that advantage has been taken of some valuable articles in foreign journals, translations of some of which have appeared in chemical periodicals, such as the Pharmaceutical Times, which is now discontinued, and the Chemical Gazette, a journal which he earnestly recommends to the practical dyer, as containing from time to time papers of great value upon Dyeing and Dyestuflfe. Partick, Glasgow, 25rt Feb., 1853. CONTENTS. Preface, GENERAL PROPERTIES OF MATTER, Heat, Conditions of matter, Heat the cause of conditions of matter, General effects of heat. Measures of temperature. Boiling of liquids, Substances affecting boiling point, . Strong boiling, Chemical effects of heat upon colours, Light, Nature of light, Relation of colours to the fabric, Effects of different rays upon colours. Effects of light causing combination, Light decomposes chemical compounds, Practical application of the principles. Elements of Matter, Difference between an element and compound. Use of symbols, .... Chemical nomenclature, Rules for naming compounds. Salts, their nature and nomenclature, Chemical Affixity, Application of affinity, Circumstances influencing affinity, Catalytic influence, . Constitution of salts. Salt radicals. 10 11 13 14 14 16 20 22 24 24 20 29 30 30 31 33 CONTENTS. NON-METALLIC SUBSTANCES. Oxygen, . Hydrogen, Water, Nitrogen, Protoxide of nitrogen, Binoxide of nitrogen, Nitrous acid, Peroxide of nitrogen, Nitric acid, . Ammonia, Chlorine, Hypochlorous acid, Clilorous acid, Cliloric acid, Hj'perchloric acid, Hydrochloric acid, Chloride of nitrogen. Processes and theories of bleaching, Ozone, Sulphur, Sulphurous acid, Sulphuric acid, Hyposulphurous acid, Hyposulphuric acid. Sulphuretted hydrogen, Selenium, Phosphorus, Iodine, Bromine, Fluorine, SiLlCIUM, Boron, Carbon, . Carbonic oxide, Carbonic acid. Oxalic acid, Cyanogen, Mellon, CONTENTS. METALLIC SUBSTANCES. General Properties of Metals, Potassium, Potash, Sulphate of potash, . Bisulphate of potash, Sulphite of potash, . Nitrate of potash, Chlorate of potash, . Phosphate of potash, Oxalate of potash, Ferrocyanide of potassium, Ferricyanide of potassium, Cyanide of potassium, Cyanate of potash, Sodium, . Soda, Soda-ash, Sulphate of soda. Chloride of sodium, Nitrate of soda, Borate of soda. Phosphate of soda, Lithium, Soap, Barium, . Chloride of barium, Nitrate of barytes, Stroktium, Calcium, . Caustic lime. Sulphate of lime. Carbonate of lime, Magnesium, Magnesia, Aluminum, Alumina, Alum, Acetate of alumina, CONTEKTS. Manganese, Mineral cameleon, Iron, Sulphate of iron. Chloride of iron. Carbonate of iron. Acetate of iron. Persulphate of iron, Nitrate of iron, Protosalts of iron, Persalts of iron, Cobalt, . Nickel, . Sulphate of nickel, Chloride of nickel, Nitrate of nickel, Carbonate of nickel. Zinc, Chloride of zinc, Sulphate of zinc. Nitrate of zinc, Cadmiubi, Copper, . Protoxide of copper Sulphate of copper. Nitrate of copper, Chloride of copper, Acetate of copper Oxalate of copper, Arseniate of copper, Arsenite of copper. Lead, Suboxide of lead. Protoxide of lead. Peroxide of lead. Carbonate of lead. Nitrate of lead. Acetate of lead. Sulphate of lead, Chloride of lead, CONTENTS. BlSMDTD, . Nitrate of bismuth, . Tin, Protoxide of tin, Protochloride of tin, Protosulphate of tin, Protonitrate of tin, . Tartrate of potash and tin, Deutoxide or sesquioxide of tin. Peroxide of tin, Perchloride of tin, Spirits, Red spirits, . Plumb spirits, Banvood spirits. Yellow spirits. Acetate of tin, Oxalate of tin, Titanium, Chromium, Chloride of chromium. Sulphate of chromium. Chromic acid, Bichromate (red chromate) of potash Chromate of lead. Chrome yellow. Chrome green, Chrome orange, Vanadium, tungstenum or wolfram, moltbdenum, Peroxide of molybdenum, Molybdic acid. Tellurium, Tellurous acid, Telluric acid. Arsenic, Arsenious acid, Arsenic acid, Sulphurets of arsenic. XIV CONTENTS. AuTiMOirr, Oxide of antimony. Sulphate of antimony, Antimonious acid, Antimonic acid, Ubanium, Protoxide of uranium, Peroxide of uranium, Ceeitisi, . Mbecuet, Suboxide of mercury, Protoxide of mercury, Peroxide of mercury, Silver, . Nitrate of silver, Sulphate of silver, Gold, Subchloride of gold, Perchloride of gold, Platinum, Palladium, Iridium, Osmium, Rhodium, Lanthanium, MORDANTS Red Spirits, Bar-wood Spirits, Plumb Spirits, . Yellow Spirits, Nitrate of Iron, Acetate of Iron, Acetate of Alumina, Black Iron Liquor, Iron and Tin for Royal Blues, Acetate of Copper, CONTENTS. VEGETABLE MATTERS USED IN DYEING. Introductory Remarks, Galls, . Sumach, Catechu, Valonia nuts, Divi divi, Myrobalans, Indigo, Commercial indigoes Woad and pastel, Indigo blue. Pastel vat, . Woad vat, . Modified pastel vat, Indian vat, . Potash vat, . German vat, Management of the vats. Logwood, Brazil-Woods, Santal or Sandal-Wood, Barwood, Camwood, Fustic or Yellow- Wood, YoDNG Fustic, . Bark or Quercitron, Flavine, Weld or Wold, Turmeric, Persian Berries, Safflower or Carthamus, Madder, Levant madder, Dutch madder, Alcase madcfer. Madder of Avignon Madder purple. Madder red, XVI CONTENTS. PAGE Madder, Madder'oraDge, . - » . . 359 Madder yellow, . 359 Madder hrown, . 360 Madder acids, . 360 Useful products. . 360 Madder preparations, . 361 Colorine, .... . 364 Mdsjeet, .... . 365 Ansotta or Arnotto, . .365 Alkanet Root, . 369 Archil, .... . 370 TROPOSED NEW \T:GETABLE DYES Sooranjee, Cakajuru or Chica, "WOKGSHT, Aloes, . PiTTACAL, Barbart Root, 372 376 377 381 382 383 ANIMAL MATTERS USED IN DYEING. Cochineal, Carmine, Lake Lake or Lac, IVERJIS, . 384 385 389 390 GLOSSARY OF TERMS, INDEX, 393 397 DYEING. GENERAL PROPERTIES OF MATTER. HEAT. Conditiona of wiatter.— Matter, wbicli is every thing capable of affecting the senses, exists in three different states, — soHd, fluid, and gaseous. Looking upon matter in any of these states, the most casual observer cannot fail to distinguish a great variety of appearance. For example, — stone differs from brick, bread from wood, and iron from both, among the solid forms ; while differences quite as great are seen both in fluids and amongst gases. But, although these difiereuces are famihar to all, there are few who inquire the cause why, under the same circumstances, one portion of matter exists as a solid, another as a fluid, and a thu'd as a gas. Correct answers to these in- quiries are the objects of all scientific research. They are, in their nature, twofold — phjsical and chemical. The former, embracing the study of matter in mass, takes cognizance of shape, measure, hardness, weight, flexibility, tenacity, divisi- bility, and such like properties ; while the latter, the chemical, investigates those more remote differences which depend on the relative powers, properties, and mutual actions of the elemental components of the given substance — an inquiry which embraces a universal interrogation of all kinds of matter. Heat the Canse of Conditions of Matter — That One body is solid, another fluid, and a third gaseous, is an inquiry which belongs more directly to physics than to chemistry ; yet heat, which is the cause of tliese differences, is so intimately con- nected both with the molecular changes, and the constitution of bodies, particularly of the colouring matters used in dyeing, D. H. HILL LfORARY ttotth Carolina State Coilcgo 2 HEAT THE CAUSE OF CONDITIONS OF MATTER. that it ^vill be proper to enumerate, preliminarily, a few of its most prominent effects and general laws, for conveni- ence of frequent reference when we come to speak of the practical effects of those laws on many of the operations in the dye-house. All bodies are supposed capable of existing in the three states — solid, fluid, and gaseous — by the addition or subtrac- tion of heat ; but the same degree of heat does not affect all kinds of bodies to the same extent. For example, — water, subject to the ordinary pressure of the atmosphere, at 32''Fah. and under, is solid, from 32" to 212^ it is fluid, and from 212° upwards it is gaseous ; while quicksilver, another fluid, at ordinary temperatui'e, does not become sohd until it is cooled 72" below that of the sohdi^'ing point of water, and does not pass into the gaseous state until it is heated lapwards of 400° above the aeriform point of water. Again, lead and several other bodies only become fluid at the temperature which gasifies quicksilver. The follo^ving table will make this more apparent : — Solid Becomes Becomes Range of matter tluid at gaseous at fluidity. SvdphuTous Acid,... 105 105 14 91 Carbonic Acid, 71 None. 7 1 None. Mercury, 39 39 622 701 Water, 32 32 212 180 Tin, 442 442 aboiit2400 about 2058 Lead, 594 594 Not kno-s\Ti. Bismuth, 500 500 900 400 Arsenic, 356 None. 356 None. Silver, 2283 2283 Not kno\\Ti. Cast Iron, 3479 3479 Not known. This table shows how differently the same degree of heat affects different substances. We cannot conceive a condition so cold that all matter would be solid, nor so hot that all would be gaseous. In the cases of carbonic acid and arsenic, there appears an exception : these bodies have no fluid range — they have no existence in a fluid state. The former may be bbtained fluid by pressure ; but this is under extraordinary circumstances, and the particles still retain their elasticity, which a true fluid does not. But when in the sohd state, and GENERAL EFFECTS OF HEAT. 3 under ordinary conditions — that is, under the ordinary pres- sure of the atmosphere — it passes directly from the soUd to the gaseous state. Some philosophers, reasoning from analogy, and not admit- ting any exceptions to general laws in nature, object to the apparent fact, and give, as their opinion, that such substances as carbonic acid really have a iluid range, but being so little, probably only a few degrees, the body may pass through that state without obsei'vation. This supposition is imtenable, and is founded upon a mistaken view of what is a general law. The range of fluidity of any body depends upon the amount of pressure which the body is subject to. There are many other bodies, besides carbonic acid and arsenic, that re- quire a greater amount of pressure than that of our atmos- phere to maintain them in the fluid state ; so that both the facts and the circumstances are quite in accordance with the general laws of nature. General liffceis of Heat.— In connection with the general laws of heat, we may notice, first, that bodies Avhen they become heated expand, or become larger — the particles which compose them seem to separate farther from one another. This effect is produced upon matter in all states. Familiar illus- trations of this effect of heat are numerous. If a pair of tongs, with legs of equal length, have one of the legs put into the fire and made red hot, it will be found, in this state, longer than the other. It is well known to dyers, that if a boiler be filled to within a little of the mouth with cold water, and a fire put under it, by the time it begins to boil the water runs over, having enlarged so much that the boiler is too small to con- tain it when hot. And another circumstance often occurs — when a certain quantity of a decoction of a dye is required, and is measured out of the boiler in gross while hot, and then distributed in its requii'ed proportions when cold, there is often wanting a considerable portion of liquid, causing serious annoyances in the dye-house, when the difference of tempera- ture is not taken into consideration. That gaseous bodies are affected in the same way by heat, may be illustrated by taking a bladder, and filling it three parts full with cold air, tying it round the neck, and holding it before a fire — or, what is better, taking the bladder into the drying-stove connected with the dye-house. In a very little 4 MEASURES OF TEMPERATURE. the bladder becomes distended and quite full, and may be made to burst by the expansion of the air, if the heat be high, or the bladder nearly filled. measures of Temperalnrr.— Upon this expatisive effect of heat isfounded the means of measuring its intensity. Our senses tell us when a body is hot or cold, but they are very imper- fect indicators of the degree or intensity of the heat. Our own temperature being the standard, we can only tell that a substance is hotter or colder than our own body. In the dye- house, where the hand is often made the indicator of the tem- perature of the dyeing liquid, the result varies according to whether the person has been previously working in hot or cold liquids, and is therefore a very imperfect test of temperature, and often productive of evils by giving different tints of shades, and deteriorating the beauty of a colour. Temperature is very correctly measured by observing the amount of expan- sion in any given body. Instruments for this purpose are plentiful and cheap : we will therefore not require to detail their mode of manufacture, but a good thermometer is an essential instrument in the dye-house, and ought to be con- stantly employed. The thermometers used in this country are generally those of Fahrenheit. The scale of measurement of this has been determined in the following manner : — Fahren- heit divided the two points, from the freezing of water to its boiling, into 180 degrees : he called the freezing point the 32d degree, from some reason of his own ; hence 32°-f 180°zr212, the boiling point of water, according to Fahrenheit. There is another scale sometimes used, called Reaumur's. This has the two points, from the freezing to the boiling of water, divided into 80 degrees. Another, and more generally used scale, has the range from freezing point to boiling of water divided into 100° ; thus the freezing point is marked 0, the boiling point 100. This is termed the Centigrade thermo- meter. In reading books where temperature is referred to — such as in many dyeing recipes and processes — attention must lie paid which thermometer scale is referred to. They are generally indicated by abbreviations, — as F., or Fah., for Fahrenheit's scale, R., or Reau., for Reaumur's, and C. for the (Centigrade. The following table of the comparative value of the different scales, will guide the operator in using one or other of them : — COMPARATIVE VAIXE Ob" THE SCALES. Cent 0.. 1 .. 2 .. 3.. 4.. 5... 0.. 1 ... 8... 9.., 10.. 11... 12... 13.. 14.. 15.. 16.. 17.. 18.. 19.., 20.., 21.. 22.., 23.. 24.. 25.. 26... 27... 28.., 29... 30.. 31.. 32... 33... Fall. 32 33.8 ,35.G 37.4 39.2 41 42.8 44.6 46.4 48.2 50 51.8 53.6 55.4 57.2 59 ,60.8 62.6 G4.4 66.2 68 69.8 71.6 73.4 75.2 77 78.8 80.6 82.4 84.2 86 87.8 89.6 91.4 Cent. 34. 35. 36. 37 38. Fall. 93.2 95 96.8 98.6 100.4 39 102.2 40 104 41 105.8 42 107.6 43 109.4 44 111.2 45 113 79 174.2 46 114.8 80 176 47 116.6 81 177.8 48 118.4 82 179.6 49 120.2 83 181.4 50 122 84 183.2 51 123.8 85 185 52 125.6 86 186.8 53 127.4 87 188.6 54 129.2 88 190.4 55 131 89 192.2 56 132.8 90 194 57 134.6 91 195.8 58 136.4 92 197.6 59 138.2 93 199.4 60 140 94 201.2 61 141.8 95 203 ^'i 113.6 96 204.8 63 145.4 97 206.6 64 147.2 98 208.4 65 149 99 210.2 66 150.8 100 ... 212.0 67 152.6 It will be seen from this table that every 5 degrees of the Centigrade scale is equal to 9 Fahrenheit ; so that any degree of the one may be converted into the other by a simple rule, namely, by multiplying the Centigrade by 9, and dividing by 5, then adding 32°. Thus, if any liquid is recommended to be at 60*' C, then GO'' Cent, x 9 ^ 5 + 32° = 140" F. ; or, by Cent. Fuh. 68 154.4 69 156.2 70 158 71 159.8 72 161.6 73 163.4 74 165.2 75 167 76 168.8 77 170.6 78 172.4 6 SUBSTANCES AFFECTING BOILDfG POINT. Eeaumur's, the only difference in the process is to divide by 4 instead of by 5. Thus, 60° E., x 9 -4- 4 + 32° =167° F. Boiling of iiiqnids.— The heating and boiling of Hquids is explainable by the principle of expansion. "WTien heat is ap- pUed to a vessel holding water, the particles of water nearest the fire become heated, and consequently expand ; and, in this expanded state, being hghter than the particles above them, they rise to the surface and give place to another layer of particles. These particles are in turn heated, and rise to the surface; and so on, successively, until the fluid is all heated to the point at which it passes off as vapour or steam. The .exact temperature at which this takes place is stated above as 212° Fall., but varies a httle from the amount of pressure upon its siuface, so that water boUs at a lower heat upon a high hUl than at the foot of it ; and, for the same reason, it requires a higher temperature to boil the water at the bottom of a deep pit than upon the surface at the mouth of the pit — there being a greater pressure of air at the bottom of the pit in proportion to the depth. Substances AiTecting Boiling Point.— Anything that gives an increased attraction to the particles of a fluid also raises the temperature of the boiling point. Some kinds of vessels — such as glass and polished metals — retain the water with greater force than rough vessels, hence it requires a httle higher heat to boil water in vessels of polished material. Water, upon the surface of oil, boils two degrees of heat below water in a glass vessel, in consequence of the oil having no attraction for water. Substances dissolved in .water have often a similar effect, the attraction of the two substances having to be overcome. Thus, alkaline leys — soda or potash dissolved in water — re- quire higher temperatures to boil them than pure water does. But, connected with this, we may mention a circumstance of great importance in the dye-house. In boiling alkaline leys, so strong is the attraction of the water for the alkali, that it carries a small quantity with it in passing off as steam ; so that great care should be taken in a dye-house where leys are being boUed, that the steam or vapour does not come into contact with any coloui's that will be affected by alkalies. Where con- venient, it is, mdeed, safest to have all alkahne leys boiled entirely apart from where any coloured goods are likely to be STRONG BOILING. 7 exposed to the influence of these vapours. We have seen many annoying and expensive accidents caused by neglect- ing this precaution, especially upon such colours as safHower reds and Prussian blues. Strong Boiling.— Another circumstance of common occur- rence in the dye-house is what is termed strong boiling. This means that, in the process of boiling, we increase the fire, in order to give the liquor more heat, and make it hotter. We need hardly say that this is an error ; for a Uquid at the boil- ing point cannot be more heated by increase of fire. All that is reqiured is as much heat as will retain it on the spring of the boil, and the liquid will then be as hot as though it boiled with the greatest violence. The only difference in strong boiling is, that much more steam is driven off, which carries off the heat applied, and lessens the quantity of solution ; stUl, if a thermometer be placed in the liquoi', the tempera- tiire is found to be the same, and the only effect is that the heat is more rapidly carried off by the steam, and lost. The amount of heat which steam thus imbibes and takes away, is calculated, in round numbers, at 1000° Fah., which may be illustrated as follows : — If one pound of water, at 32°, requires the burning of a pound of coal to bring it to the boiling point, (212°) the water will have received 180° of heat; if the fire be continued at the same rate, it will take 5-^ lbs. of coal to convert the pound of boiling water into steam, and the tem- perature of the steam will never be above 212° Fah. : thus 1000° of heat have been taken up by the steam, and retained in a latent state, — that is to say, in a state not sensible to the thermometer. Or we may illustrate this principle by another experiment : if we take 5^ lbs. of water at 32°, and pass a jet of steam at 212° through it, until the water begins to boU, the whole water will weigh 6-g^ lbs. ; thus 1 lb. of steam has brought 5-5- lbs. of water up 180°, thereby showing that this pound of steam had contained 1000° of heat. These facts the practical dyer can easily apply to his own purposes. Steam is very generally used in the dye-house as a heating agent for water, making decoctions, and the boiling of goods. It is an observed fact that steam is not so effective for many pur- poses as fire — as in the making of some decoctions. In the using of steam for boiling, some of the circumstances referred to ought to be kept in mind, such as the fact that steam can- 8 CHEMICAL EFFECTS OF HEAT UPON COLOURS. not raise the temperature of the boiling liquid above 212". Hence the conditions noticed of the raising the boiling point of water by the presence of matters held in solution, and by different kinds of vessels, do not apply to liquids when boiled by steam. This may be one cause of the observed difference of effect in the dye-house. Again, water boiled by passing a jet of ordinary pressure steam into it, never gets above 210°, a small deficiency, but sufficient to cause a difference in the results of many operations in the workshop. This fact may be accounted for by the circumstance that in this process there is no attraction of the water by the surface of the vessel, as when boiled by fire, which, as has been ob- served by Berzelius, causes the boiling point in different vessels to vary upwards of 2°. In boiling by steam, no such attraction has to be overcome as that between the vessel and water; hence the boUing point is lower, and 210° may be actually the true boihng point of water. For all ordinary pur- poses, however, steam, as a heating agent, is of the highest value to the dyer. Chemical Eflects of Seat npon Colours.— The effects of heat in relation to chemical combination and decomposition, are of the utmost importance in all the operations of the dyer. The influence of heat in producing particular tints and coloui's, and also upon many colours when produced, are subjects of eA'ery- day observ-ation. Nevertheless, the consequences are often so important, that the subject cannot be too fully impressed upon the minds of all interested. We shall, therefore, enumerate a few of the more prominent effects in this place. In making a decoction of quercitron bark, for dyeing yellow, if it is made at a temperature of about 90°, a much finer and purer yellow is obtained than when the decoction is made by boiling. When woollen cloth is dyed by bark, and then hot- pressed, the heat impairs the colour; but generally dyed colours are more liable to be affected by heat when moisture is present, than in a dry atmosphere. For instance, — a safllower red will stand a high temperature when the air is dry, but if moistiu-e be present, it passes rapidly into a yellowish brown. If a Prussian blue be placed in a moist atmosphere, and raised to the tempera- ture of about 300° Fah., it fades entirely in a few hours. Many of the colouring matters of flowers, when imparted to cloth, may be dried without change m the cold and dark, and afterwards CUEMICAL EFFECTS OF HEAT UPON COLOURS. 9 be submitted to a temperature of 200" without alteration, but could not stand a temperature of 95** without being altered were these precautions not taken : such colours, therefore, if put on goods, could not be dried in a stove. The kind of material on which the colour is dyed also influ- ences the effects of heat. Indigo blue dyed upon cotton is permanent, exposed to heat and moisture ; but the same colour, with the same dye-stuff, upon silk, is readily changed imder those conditions. Safflower colours upon silk and cotton, placed under similar circumstances in regard to heat and moisture, are affected oppositely ; that on the cotton is completely destroyed before that upon the silk is at all affected. Thus we find that heat operates upon colours differently ■when the heated atmosphere or colour is dry and when it is moist, which suggests the propriety of paying strict attention to the condition of the drying-stove, and the hanging of the coloured fabrics, so as to give a free outlet to all moisture. If this is neglected, the colours are subjected to a hot vapour bath, and are under the most favourable conditions to be de- stroyed by the joint action of the heat and steam. The same kind of coloui-ing matter fixed upon cotton by different mordants, is affected by heat differently, whether moisture be present or not. This can be observed daily of logwood colours, when fixed by tin or by alumina. The dif- ferent changes which these colours undergo in the process of drying, and the dependence of these upon the state of the stove, as to being hot and clry^ or hot and moist, are famihar to the practical dyer. But as we shall have occasion to notice some of these changes when describing the dye-stuffs, and the colours produced, we pass over the details in this place. The follow- ing, however, may be stated as a general rule, namely — that all organic colouring matters are destroyed at a red heat. There are some, however, such as indigo, which sublime, or may be distilled by a heat less than sufficient to effect their destruc- tion. Those colouring matters which are volatile, are in general most permanent when fixed upon fabrics, and resist the action of heat best ; and those colours that do not sub- lime, are most susceptible of decomposition under the com- bined influence of air, heat, and moisture. b2 LIGHT. Nature of liight.-The effects of light upon colours are so closely related to that of heat, and so powerful — particularly "the direct rays of the sun — that we cannot pass over the con- sideration of those accidental phenomena, which we must un- derstand as independent altogether of that essential relation which Hght has to produce colour. Strictly speaking, coloiu-s have no material existence, but are altogether the effect of light — at least colours do not exist in the objects appearing coloured, but in the light which is reflected from the appa- rently coloured object. In order, then, to define colour, we may briefly state what is known upon the nature and compo- sition of light — at least so far as is necessary for our present purpose. A beam of light is composed of three differently coloured rays — red, blue, and yeUow — termed sometimes the luminous, calorific, and chemical rays, from their different properties of giving out heat and light, or in exciting chemical action. When a beam of light strikes the surface of a body, it bounds off as an elastic ball would do striking the same surface, and this bounding off is termed reflection ; or, it is absorbed by the body and disappears, and is altogether extinguished ; or, lastly, it passes through the body, making it transparent. In the first case, the bounding or reflected rays pass into the eye, and the body from which it is reflected appears white, or some particular colour. In the second place, there can no light proceed from the object to the eye, it being absorbed and ex- tinguished — the body, therefore, is invisible ; or, if the sur- rovmdiug objects are illuminated, or reflect light, it appears black ; and, in the third place, the light passing through unaltered, the body appears clear. The less the light is altered, the more clear and transparent the body, and conse- quently the more nearly invisible. Thus, that which we are ac- customed to call white light is the simultaneous transmission of three coloured rays. Thus also, when light is admitted into RELATION OF COLOURS TO THE FABRIC. 1 1 a dark room through a small aperture — say a hole in a window- shutter — and a glass prism is placed in the aperture, so that the light passes through it, and is made to fall upon a sheet of white paper, the hght is decomposed, and appears upon the paper in the following order of colours : — Violet. Green. Orange. Indigo. *Yellow *Red. ^Blue. These are termed the seven prismatic colours, and the share they all occupy is termed the spectrum, of which each occupies a definite breadth. Those marked by a * are the onl}' simple colours — that is, requiring no admixture — the others are pro- duced by a mixture of different colours, and are therefore compound. The violet and indigo, for example, are com- posed of a mixture of blue and red : the green is a mix- ture of blue and yellow, and the orange of yellow and red. Hence, the primary colours are blue, red^ and yelloic. The equal admixtui'e of these three colours gives white light ; but any thing disturbing that simultaneous equality, produces a colour according to the nature and amount of disturbance. Thus, the prism through which the light entered the room, in the experiment referred to, from its shape and properties effects a complete disturbance, and the different coloiu's are made visible. Similar effects are produced, as has been already stated, when the light is reflected from a surface. If the different coloiu-ed rays are not reflected or absorbed in the same ratio, the result is a colour according to the difference in the reflection or absorption of the different ray or rays. If the red ray is absorbed, and only the blue and yellow rays reflected,- the object from which they are reflected appears green ; if the yellow ray is also absorbed, the object appears blue ; or if it has been the blue ray that is absorbed, and red and yellow reflected, the object appears orange ; or if the yellow ray only is absorbed, the object appears violet or purple. Thus, by the rate of the disturbing influence, and the different combinations of these three colours, are all the various shades in nature produced. Kelatiou of Colours to the Fabric— Although these remarks go to prove that colour has no material existence in the body appearing coloured, still the question is one of chemical science. 12 RELATION OF COLODRS TO THE FABRIC. As every chemical change affects the character of the substance in its relations to hght, the dyer's object is to effect a combi- nation with his stuffs that -will produce certain effects upon light, and thereby produce colours. It is found, sometimes, that the nature of the fabric affects the beauty and tint of a colour. A chemical compound alone may be obtained that vies with nature, both in the beauty and brilliancy of its colour ; but, when that is obtained ^Yithin the fibre of silk, cotton, or wool, the light must be transmitted through the material as a medium, and the fibre not bemg transparent, the original beauty of the colour is much diminished. Hence, the same colour, fixed within the fibres of those three substances, has different appearances in each ; the cotton never yields the beauty of colour that the silk does, or even the wool. These circumstances, in all their relations, afford matter of constant study to the practical dyer. It may be said that we cannot follow nature in the produc- tion of colours — that were the dyer to attempt to produce a white by an exact admixtm-e of blue, red, and yellow, he would fail, and would produce instead a black, or deep brown ; but this would not be a proper application of the law above stated. Nevertheless, to a certain extent, the practice of producing white by the combining the three colom'S, is had recourse to every day by the practical bleacher and dyer. All goods coming from the bleaching process, no matter what the nature of the process has been, have always a brownish yellow tinge : to cotton goods, a little indigo or cobalt blue is added, and the result is, a much purer white : to silk, which has much more of the yellow tinge than cotton, a httle Prussian blue and cochineal pink, or what is more common, a little archil, which gives a violet colour, is added, the quantity varying according to the depth of yellow — the result is a beautiful white. The following simple experiment serves to illustrate how far the production of colours depends upon the relation of the substance to light : — Take a solution of iodide of potassium, which is colourless and transparent, and divide it into three proportions : into the one pour a little acetate of lead, (sugar of lead,) into the other a persalt of mercury, and into the third a httle starch, with a few drops of nitric acid. These are all colourless substances ; but after they are mixed, in the first EFFECTS OF DIFFERENT RAYS UPON COLOURS. 13 we have a deep and beautiful yellow; in the second a red; and in the third a blue. Thus we have the three primitive colours produced by the same substance combining with other sub- stances, all previously colourless. Many white flowers, when macerated in water, yield a yellow colour, which alkalies turn green and acids red. Eflects of Diflcreiit Rays upon Coionrs —The three separate rays of light have peculiarities of action : one has heating power, and is therefore termed the calorific ray ; another has more of the property of giving light, and is termed the lumi- nous ray ; and the third has the greatest effect in changing the composition of bodies, and is in consequence termed the chemical ray. But, in our remarks upon the eflfects produced by light, we will speak of their total action. The effects of heat upon dyed colours, which we have already described, are equally applicable to light, the presence of moisture greatly facilitating the effects. Keds, dyed by Brazil- wood and a tin mordant, exposed to light, pass into a brown- ish orange, and then gradually fade away. Prussian blue becomes reddish, and passes into a dirty grey. Yellows become brown, and then fade. The effects of light and moisture are beautifully shown by taking a piece of Prussian blue dry, and another wet, and placing each under a glass, exposed to the rays of the sun for a day. The wet piece becomes a reddish lavender, while the dry piece is very little affected. SafHower colours are easily affected by light, but more so when wet ; so that when such colours are being dried in the air, care should be taken to keep them from exposure to light. The action of light upon different matters and colours, and its power of changing the constitution of these substances, have re- cently formed the subject of a distinct branch of chemical study, known by the name of actino chemistrij. Mr. Eobert Hunt, who has done a good deal in this department of chemical science, says — " The changes produced by the influence of the solar rays are of a remarkable character, and few of them, in the present state of our knowledge, can be satisfactorily explained. In some instances it would appear that new properties arc imparted to bodies by exposure to sunshine; in others that radiation has the power of disturbing the known chemical forces, and apparently establishing a new order of affinities ; whilst, in all, we are forced to recognize the operations of a 14 LIGHT DECOMPOSES CHEMICAL COMPOUNDS. principle, the nature of whicli is involved in the most per- plexing uncertainty." Effects of £.ight causing Combination.— We will here refer to a few examples of the action of Ught upon substances, and the power it possesses of inducing changes, with a view to impress upon the practical man the necessity of a strict atten- tion to all the conditions and circumstances in which he may have to place his coloured fabrics and colouring materials. In many cases bodies remain mixed and without action upon each other in the dark, but combine rapidly and form new compounds when exposed to light. Thus, chlorine and hydrogen may be kept mixed in the dark for any length of time; but, if exposed to daylight, they sUently combine and form mvu'iatic acid. If the mixtm-e be exposed to strong sunshine, the combination becomes so rapid as to cause an explosion. Chlorine, in water, remains a long time unaltered in the dark, but by exposure to light the water is decomposed, muriatic acid is formed, and oxygen given off. These effects are observed daily m the operations of bleaching. If grey goods are put into the bleaching liquor, and kept in the dark, they whiten much more slowly than when exposed to light. Many bleachers know this, and expose their goods to light, and keep their bleaching vessels in the hghtest part of the premises. Mixtures of chlorine with carbonic oxide, of chlorine ^vith sulphurous acid, and clilorine Avith pyroxilic spirit, and many other substances, are similar examples of the same kind, being all inactive upon each other in the dark, but combining easily and rapidly when exposed to light. liight Decomposes Clientical Compounds.— Chemical com- pounds are also decomposed by exposure to hght. Carbonic acid gas, exposed to strong sunshine, is decomposed into oxygen and carbon. This decomposition is supposed to go on daily in vegetable bodies during their growth, causing them to give olF oxygen and take up carbon. Colourless nitric acid, exposed to the svm, soon becomes yellowish brown, from a portion of it being decomposed, and the red nitrous fumes remaining in the acid, produce the colovu:, — whicli again shows the propriety of keeping the carboys with that acid in the shade as much as possible, as such changes by the sun's LIGHT DECOMPOSES CHEMICAL COMPOUNDS. 15 rays materially affect the preparation of many of the dyeing compounds, and also the strength of the acid. Nitrate and chloride of silver — both white salts — become black by exposure to light : paper or cloth saturated with these salts, and exposed to light, is dyed permanently black. This is the principle of the new art, photography, which con- sists in exposing a piece of paper saturated with such salts, with a leaf or picture interposed between the light and the paper : an impression of the leaf or picture is thus obtained ; and, by washing the paper afterwards in a solution of hypo- sulphite of soda, or weak ammonia, all the silver, not affected or decomposed by the light, is dissolved and removed, and the picture thus fixed. A piece of paper prepared with a solution of silver, and exposed to the coloured rays passing through a prism as described (page 11) is affected thus: — Names of coloured ray. Change on paper prepared. Violet, PurpUsh black. Indigo, Black not so purplish. Blue, Black. Green, Green. Yellow, Red. Orange, Faint brick red. Red, No change. These results are exceedingly curious and interesting, and may point out some useful application in respect to the pre- serving of compounds from change, by keeping them in vessels which admit those rays only which least affect them. Bichromate of potash put upon cotton fibre becomes dark brown by exposure to light. Chromate of copper, a brown substance, passes into white by exposure to the sun's rays. Solutions of substances are also affected by the sun's rays, sometimes sufficiently to cause a precipitation. A solution of proto-sulphate of iron (copperas) in distilled water, may be kept a long time clear in the dark ; but, when exposed to sunshine, it becomes cloudy, and oxide of iron precipitates. A solu- tion of bichromate of potash, exposed to the sun's rays, ac- quires a property of precipitating many metals, as chromates, much darker than will be pi'oduced by a similar solution kept in the dark. The reddening and darkening of chrome colours 16 PRACTICAL APPLICATIOX OF THE PRINCIPLES. by exposure to light is well known to dyers. The great effects of light upon precipitates are well known to the manufac- turers of lakes — which, let it be borne in mind, are simply the colouring matter which constitutes the dyes, precipitated and dried — and, therefore, the effect produced upon these pre- cipitates is equally true of the same colours as dyes. Sir H. Davy gives the following anecdote of a maker of carmine — a lake made from cochineal : — " A manufacturer of carmine, who was aware of the superi- ority of the French coloiu", went to Lyons for the purpose of improving his process, and bargained Avith the most celebrated manufacturer in that city for the acquisition of his secret, for which he was to pay £1000. He was shown all the process, and saw a most beautiful colour produced, but he found not the least difference in the French mode of fabrication and that which had been constantly adopted by himself. He appealed to his instructor, and insisted that he must have kept something concealed. The man assured him he had not ; and invited him to inspect the process a second time. He minutely ex- ammed the water and the materials, which were in every respect similar to his own ; and then, very much surjjrised, said — * I have lost both my labour and my money, for the au* of Bbgland does not adrnit us to make good carmine.' 'Stay,' said the Frenchman, 'don't deceive yourself; what kind of weather is it now ?' ' A bright sunny day,' replied the Englishman. 'And such are the days,' said the French- man, ' on which I make my colour ; were I to attempt to manufacture it on a dark and cloudy day, my results would be the same as yours. Let me ad"\dse you, my friend, only to make your carmine on bright sunny days.' " Practical Applicaiion of the Principles.— In the application of some of these phenomena to the trade, we must pause and inquire experimentally how this can be effected. For instance, if we dissolve a piece of iron in nitric acid, and expose a por- tion of this solution for some time to the rays of the sun, and keep the other portion in the dark, on adding a solution of prussiate of potash to each of these, the precipitate formed by the portion exposed to light will be much deeper in colour than that kept in the dark. "Were we to reason directly from the result, we would expose our nitrate of iron solutions to the light in order to have a deeper dye ; but if we test this by ex- PRACTICAL APPLICATION OF THE PRINCIPLES. 17 periment, and dye a piece with eacli of the iron solutions, it will be found that the darkest blue is obtained from the iron solution kept in the dark. Thus, we observe, without experi- ment we may be hable to reason falsely. The change effected upon the iron by the light may make it less fit to enter within the pores or cells of the fibre ; or if the combination of the stuff and fibre be affinity, these relations are affected — which we will discuss more fully in another part of this work. These brief notices of the more prominent effects of light upon colours, and other compounds, will serve to impress the dyer with the importance of attending to what he too often considers trifling cii'cumstances ; and to show that while every different condition — the moistiu-e of the air, the temperature, the degree of hght, &c., are all acting and reacting upon the substances composing his colours, both before and after they are fixed upon the fabric, nothing should be considered too trifling or of too little consequence to warrant its being overlooked. The consideration of the chemical changes which are sup- posed to be taking place in the vegetable kingdom through the influence of hght, will be more fully explained when we are treating of the colouring matters of vegetables. In, connection with hght, there is an application of a very important practical kind which it will be well to notice, namely, the arrangement of colours, so that their harmony should produce the best effect. Upon this subject many pro- positions were made for the decoration and laying out the manufactures in the Great Exhibition. Upon the philosophy of the arrangement of different colovu-s for effect, we will quote, from the Athenceum, (Athen. 1851, page 273), a few passages upon this subject, which we think will be useful to the dyer : — " The ' successive' contrast has long been known ; and it consists in the fact, that if you look steadfastly for a few minutes on a red surface fixed on a white sheet of paper, and then carry your eye to another white sheet, you will perceive on it not a red but a green one ; if a green, red ; if purple, yellow ; if blue, orange. The ' simultaneous' contrast is the most in- teresting and useful to be acquainted with. When two coloured surfaces are in juxtaposition, they mutually influence each other — favourably, if harmonizing colours, or in a contrary manner if discordant ; and in such proportion in either case 18 PRACTICAL APPLICATION OF THE PRINCIPLES. as to be in exact ratio with the quantity of complementary colour which is generated in our eye. For example, if two half-sheets of plain tint-paper — one dark green, the other red — are placed side by side on a grey piece of cloth, the colours will mutually improve, in consequence of the green generated by the red surface adding itself to the green of the juxtaposed surface — thus increasing its intensity — the green in its turn augmenting the beauty of the red. This effect can easily be appreciated if two other pieces of paper of the same colours are placed at a short distance from their corresponding influenced ones, as below : — RED. KED GREEN. GREEN. It is not sufl&cient to place complementary colours side by side to produce harmony of colour, the respective intensities having a most decided influence : thus pink and light green agree — red and dark green also ; but light green and dark red, pink and dark green do not ; therefore, to obtain the maximum of effect and perfect harmony, the following colours must be placed side by side, taking into account their exact intensity of shade and tint : — HARMONIZING COLOURS. Primitive Colours. Scconclaiy Colours. f Light blue. Eed Green •< Yellow. (Eed. ^Red. Blue Orange., ■< Yellow. (Blue. (Blue. Yellow orange Indigo ■< Red. (Yellow. fRed. Greenish yellow. . .Violet. < Blue. (Yellow. (Yellow. Black White -^Blue. (Red. " If respect is not paid to the arrangement of colours ac- cording to the above diagram, instead of colours mutually PRACTICAL APPLICATION OF THE PRINCIPLES. 19 improving each other, they will, on the contrary, lose in beauty : thus, if blue and purple are placed side by side, the blue throwing its complementary colour', orange, upon the purple, will give it a faded appearance ; and the blue receiving the orange-yellow of the purple, will assume a greenish tinge. The same may be said of yellow and red, if placed in juxta- position. The red, by throwing its complementary colour, green, on the yellow, communicates to it a greenish tinge ; the yellow, by throwing its purple hue, imparts to the red a disagreeable purple appearance. It is of very great importance that every one should be acquainted with the laws of colours who intends to display or arrange coloured goods or fabrics. " The mixed contrast gives the reason why a brilliant colour should never be looked at for any length of time if its true tint or brilliancy is to be appreciated ; for if a person looks, for example, at a piece of red cloth for a few minutes, green, its complementary colour, is generated in the eye, and adding itself to a portion of the red, produces black, which tarnishes the beauty of the red. This contrast explains why the shade of a colour may be modified according to the colour which the eye has previously looked at, either favourably or other- wise. An example of the first instance is noticed when the eye first looks to a yellow substance and then to a pui'ple one; and as exemplifying the second case, looking at a blue and then at a purple." ELEMENTS OF MATTER. 1>iflerences between an Element and Compound —It has been intimated that the conditions of matter — solidity, fluidity, and gasuity — depend upon heat ; and it was also stated that, in each state, there is a A^ast variety — a variety so great that the idea of telling where their conditions begin and end is a task seemingly beyond human power. Nevertheless, by labour, by experiment, and comparison, much has been done not only to distinguish every variety of substance, but why one sub- stance differs from another both in appearance and quality. Let us take a known compound as an illustration : When a piece of steel is placed into diluted sulphuidc acid, the acid dissolves the greater part of it ; but there is left undis- solved a black matter, which, by testing, we find to be charcoal or carbon, and that which has been dissolved is iron. We therefore infer that steel is composed of iron and charcoal — that it is a compound substance ; but if we take the carbon, and treat it in any way within our power, we find it still the same, without components. In the same manner let us test iron — dissolve it, melt it, or treat it as we will, it yields nothing but iron. All such substances, then, that resist every effort to decompose, or show any admixture, are termed ele- mentary, or simple substances. The number of such elements known to the chemist at the present time are sixty-two, and all the varieties in which we find matter presenting itself to us — whether in the mineral, the vegetable, or the animal kingdoms — are made up of one, or a mixture of two or more of those sixty-two elements. The following table gives the names and particulars necessary to be observed in the study of these elements: — DIFFERENCES OF AN ELEMENT AND COMPOUND. 21 Aluminum Al Antimony Sb Arsenic As Barium Ba Beryllium Be Bismuth Bi Boron B Bromine Br Cadmium Cd Calcium Ca Carbon C Cerium Ce Chlorine CI Chromium Cr Cobalt Co Copper Cu Didymium D Erbium E Fluorine Fl Gold Au Hydrogen H Iodine I Iridium Ir Iron Fe Lanthanium La Lead Ph Lithium ....,,... Li Magnesium ]\Ig Manganese Mn Mercury Hg Molybdenum . . .Mo When two or more of these elements combine together, it is found that the union does not take place indeterminately, but always in definite proportions. Those proportions are expressed by the figures placed opposite to the names in the above table. For example, if we mix together one ounce of hydrogen and one ounce of oxygen, and bring them under circumstances to cause combination, it is found that the one ounce of oxygen has combined with an eighth part of the hydrogen, or two drams, and that other seven ounces of 13-7 Nickel ..Ni = 29-6 129 Niobium ... ..Nb 75 Nitrogen ... ..N = 14 = G8-5 Norium .... ..No : 47 Osmium... . ..Os = 99-6 213 Oxygen.... .0 = 8 10-9 Palladium . ..Pd = 53-3 80 Pelopium... ..Pe 56 Phosphorus ..P = 32 20 Platinum .. • Pt =- 98-7 6 Potassium . .K = 39-2 47 Rhodivim . .R = 52-2 35-5 Ruthenium . ..Ru = 52-2 26-7 Selenium... .Se = 39-5 29-5 Silicium.... ..Si = 21-3 = 31-7 Silver ..Ag =108-1 Sodium .... ..Na = 23 Strontium . ..Sr = 43-8 : 18-9 Sulphiu- .... .S = 16 =197 Tantalum . ..Ta =184 = 1 Tellurium . ..Te = 64-2 = 127.1 Terbium ... ..Tb = 99 Thorium ... ..Th = 59-6 -- 26 Tin .Sn = 59 Titanium... ..Ti = 25 =103-7 Tungsten . . . ..W = 95 = 6-5 Uranium ... ..U = 60 = 12.2 Vanadium . ..V = 68-6 -- 27-6 Yttrium .... ..Y 3100 Zinc ..Zn = 32-6 = 46 Zirconium . ..Zr = 22-4 22 rSE OF SYMBOLS. oxygen are required to combine with the whole of the hydro- gen. Their combining properties are therefore set down as 1 to 8. The same law holds good for every other element ; so that the union is invariably distinct and definite. One ele- ment, however, is often found to combine with another in a greater number of proportions than one to one. Thus, sup- pose nitrogen — which, according to the table, has a com- bining weight of 14 — combines with oxygen in proportions as under : — One nitrogen = 14 to one oxygen = 8. One nitrogen r= 14 to two oxygen =16 two times 8. One nitrogen = 14 to three oxygen = 24 three times 8. One nitrogen r= 14 to four oxygen = 32 four times 8. One nitrogen =: 14 to five oxygen rr 40 five times 8. Thus we observe that the proportion of oxygen is always 8, or a multiple of 8 ; so it is with nitrogen, always 14, or twice 14, and so on to any number of multiples of 14. The same rule holds good with every element in the table ; they combine only according to the number follo^ving the name. But when they thus combine in different and distinct quan- tities, the compounds formed are also distinct and definite. Thus, one portion of nitrogen and one oxygen is laughing gas ; and it is so at all times and under all circumstances, and can be nothing else. But when two of oxygen combine to one of nitrogen, a different substance is formed from laughing gas, also distinct and definite from every other proportion in which the elements unite. The first and last of the above list is an apt illustration — the former being laughing gas, the latter acjuafortis — nitric acid. Use of Symbols.— The letters placed immediately after the names of the elements in the above table, are the symbols com- monly used to represent the respective elements, and facilitate the expression of the compounds into which they enter. Thus, to represent laughing gas, we write N O, which means one of nitrogen and one of oxygen. The symbol always re- presents the weight of the j^^'oportion, as given in the table ; and the figures attached show how often that proportion is repeated. Thus, the formula for aquafortis, NOj, which means one part of nitrogen and five of oxygen — the figure USE OF SYMBOLS. 23 being placed immediately after the symbol which is multiplied. Were there two of nitrogen and one oxygen, the formula would be N^O ; but sometimes there may be two or more proportions of a compound combined with another compound : this is represented by placing the figure before the compound to be multiplied, and a comma at the end. For example, — two proportions of aquafortis united with one of w^ater is ex- pressed thus, 2N0j, HO. The figure 2 applies to all between it and the comma. Some use the sign + instead of a comma — thus, 2NO5, + H0. It being important to the student that these be fidly understood before beginning to read for study, we will take another series of compounds : — SO3 one sulphur, three oxygen, sulphuric acid. SO3-1-HO sulphuric acid with one water. 2SO3-I-HO two sulphuric acid with one Avater. SO3 + 2HO sulphuric acid and two water. SO3-I-3HO sulphuric acid and three water. SOs + FeO or SO3, FeO sulphuric acid and oxide of iron. SOgFeO+HO sulphuric acid, oxide iron, and water. SOsFeO-f- 5110 sulphuric acid, oxide of iron, and five water. 3SO3, Fe203-|- Olio, here we have three of sulphuric acid, two of iron, three of oxygen, and nine water, which is the formula of one of the salts of iron. To make up the equivalent weight of any compound from symbols, we have simply to multiply the elements given ac- cording to the table. Thus, suppose we take the sulphuric acid and two watei', which is strong vitriol, we have One sulphur,. equivalent weight, 16 z= 16 Three oxygen, 8x3 = 24 Two water, 1 Hy. and 8 oxygn...=9 x2 = 18 58 which is the proportion or weight of sulphuric acid of the strength which would be required to combine with any other element, suppose iron, which is 28 ; therefore it -would require fully twice the weight of sulphuric acid of this strength to that of a piece of iron to dissolve it. 24 CHEMICAL XOMENCLATCKE. The following formula of crj'stallized alum Avill serve as an exercise for the student upon the symbols and equivalents : — - KOSOj, AlA 3S03+24HO. Some chemists, instead of using O for oxygen, express it by a simple . — thus sulphuric acid will be S, or the alum — KS aL 3S 24:H. iVomenciatnre.— In the nomenclature of these elements in the above table there has been no definite rule, being named either from the fancy of the discoverer, or from some leading property or appearance they present, which will be noticed under their separate descriptions ; but, in naming compounds, a distinct rule has been adopted, so that the name of the compound ex- presses, as nearly as possible, its composition and property. We will give a few of the leading principles observed in this rule of naming compounds. Rales for iVnining Componnds — TVTien two elements Combine together, and the compound formed has not acid properties, the name ends in ide, such as oxide, chloride, bromide, iodide, &c. Sometimes uret is used instead of ide, such as in sulphu- ret, carburet, phosphuret, «fcc. ; but ide is now most generally adopted even for these, giving suljjhides, carbonides, phosphides, &c. When the compound foi'med by the union of the ele- ments has acid properties, the name ends in ic, or ous ; thus we have sulphuric, sulphurous, nitric, 7iitrous, chloric, and chlo- rous acids ; but these elements, uniting together in different multiples, have prefixes added to express the number of pro- portions. Thus, proto denotes one proportion, or first ; deuto, or bi, two proportions ; trito, three proportions ; per denotes no particular number only the highest proportion. As ex- amples, take the compounds of hydrogen and nitrogen, already noticed : — NO protoxide of nitrogen. NOo binoxide of nitrogen. NO3 nitrous acid. NO4 peroxide of nitrogen. NO5 nitric acid. Thus, we observe, the full name of the substance not having CHESnCAL NOSIENCLATURE. 25 acid properties denotes its composition. In the case of acids, it does not tell the number of elements combined, as with oxides — ous simply signifying that it has less oxygen than an- other acid composed of the same elements, and which ends in ic. There are sometimes more than two acids formed by the com- bining of the same elements ; in this case, if the oxygen is less than in the acid whose name terminates with ous, the prefix /ii/])o is put to the name of the ous acid; if there be more oxygen than in the ous acid, and less than the ic acid, the same prefix is made to the last-named acid. Finally, when there is more oxygen present than in the acid whose name termi- nates with ic, the prefix ]7e)- is put as in oxides. The follow- ing illustrations will exemplify these terras : — S2O0 hypo-sulphurous acid. 502 sulphurous acid. S2O5 hypo-sulphiu'ic acid. 503 sulphuric acid. Any acid found having more oxygen, in relation to the sul- phur, than the last named in this Ust, would be called per- sulpkuric acid. It will thus be seen that the names of the compounds denote their composition, and give an idea of their leading properties. The term sesqui — as sesquioxide — is often used, "and means one and half of an equivalent, which, as may be inferred from what has been said, cannot take place. Never- theless, the name is conveniently retained to denote such com- pounds as have two of one element and three of another — such as sesquioxide of ii'on, also termed peroxide, and which is composed of two iron with three oxygen, FcoOj. Some- times one proportion of oxygen, chlorine, &c., combines with two proportions of a base as a metaj ; such compounds have the prefix sub, or di, as FeaO, sub-oxide of iron, or dinoxide of iron. CuoCl, sub-chloride, or dichloride of copper. Wlien one proportion of oxygen, chlorine, &c., combines with three of a metal, the prefix tn'sub or tridi, is occasionally used, but this is not very convenient ; the best and most general plan is to denote such compounds as basic, and then apply the ordinary prefixes, such as bibasic, tribasic, &c., thus : — c D. H. HILL LIBRARY North Carolina State College 26 CHEItflCAL NOMENCLATURE. CujO, bibasic oxide of copper. CusO, tribasic oxide of copper. In the name of a compound ending in ide, the base or ele- ment with which the oxygen, chlorine, «S:c., is combined, is named last, as Oxide of iron. Oxygen and iron. Chloride of iron. Chlorine and iron. Iodide of iion. Iodine and iron. Oxide of sulphur. Oxj'gen and sulphur. Oxide of nitrogen. Oxygen and nitrogen. But with compounds having acid properties, the base is placed at the beginning, thus : — Sulphuric acid. Sulphur and oxygen. Nitric acid. Nitrogen and oxygen. Hydrochloric acid. Hydrogen and chlorine. Sails—Their Nature and Nomenclature. —The acids combine with other substances, as the metals, and form another class of compounds termed Salts. The names of these also denote their composition : the salt formed between the acid terminat- ing in ic and a base, ends with ate ; that formed by the acid ter- minating in ous ends with ite, the name of the element with which the acid combines being added. Thus, Sulphuric acid and iron form sulphate of iron. Sulphurous acid and iron sulphite of iron. When these acids unite with elements or bases in different proportions, the same prefixes are used as with oxides. If one proportion of acid unites with one of another element, the compound is termed 2)roto — as proto-sulphate of iron ; if two of acid and one metal, the compound has bi — as bisulphate of iron, &c. Per is also used as denoting the highest proportion, as when three equivalents of acid unite with two equivalents of iron, the salt is termed persulphate of iron. Sometimes wo have the metal uniting with acids, forming l)asic salts, as described in the case of the basic oxides, such as having two proportions of metal to one of acid, and three pro- portions or equivalents of metal to one of acid. In such cases, the same prefixes are used as we have before stated, namely, — CHEMICAL NOMENCLATURE. 27 hibasic sulphate of copper, two equivalents of copper to one of sulphuric acid ; tribasic sulphate of copper, three copper to one acid. Combinations of water with oxides or salts are termed hy- drates, or the compound is termed hydrous, in contradistinction to substances having no water, which are termed anhydrous — thus, hydrate of potash, or hydrous potash, KO HO ; anhy- drous potash, KO. Two salts sometimes unite together, and form a definite compound, which is termed a double salt. Alum, as already given, is a good instance of this class of compounds : it is a double salt of sulphate of alumina and sulphate of potash. CHEMICAL AFFINITY. The elements of matter have a disposition, if we may use the term, to unite with one another : this disposition is termed affinity, or chemical attraction. The aliinity of any one element for the others is not equal, but is greater for some one element, or, for a particular class of elements. Thus oxygen has a stronger attraction for those elements, the combining with which forms alkalies, than for any of the others ; and amongst these potassium has the strongest affinity for oxygen, so that, by the operation of this law, should a number of elements be arranged together, under proper cir- cumstances for combining, those which have the strongest attraction for each other will combine first. The same law holds good when compound bodies unite together, such as an acid with the oxide of a metal. "Were we to take sulphuric acid, and add to it a mixture of potash and magnesia, the acid would combine with the potash before it would take the mag- nesia ; and were there enough of potash to combine with the whole of the sulphuric acid, the magnesia would be left, because the potash has a stronger attraction for this acid than magnesia. This peculiarity of selecting is not merely owing to the substance having acid properties, but from a peculiar attraction between the base and acid compounds. Thus the two acids, sulphuric and muriatic, comport themselves towards the following bases, as under : — Muriatic Acid. Sulphuric Acid. Silver. Barytes. Potash. Strontia. Soda. Potash. Barytes. Soda, Strontia. Lime. Lime. ^lagnesia Magnesia. Silver. AI'PLICATION OF AFFINITT. 29 Although we have named silver here, under the sulphuric acid column, in order to complete the comparison, it is not immediately next to magnesia in affinity for that acid ; a great many of the other metals rank before it, such as mercury, copper, iron, zinc. So that, were there a solution of sulphate of silver added to a solution containing these, the acid would leave the silver and combine with the mercury, next leave the mercury and combine with copper, then leave the copper and take the iron, and lastly leave the iron and take the zinc. It is this law of affinity that regulates compositions and de- compositions, all of which are matters of daily experience in the dye-house, particularly that class of decompositions termed double, in which two salts being put together, there takes place a mutual exchange of partners, if we may so term it. For instance, in mixing nitrate of iron with yellow prussiate of potash : the nitric acid leaves the iron, and combines with the potash, while the iron and prussic acid combine, forming Prussian blue. When any of the two compounds so com- bined forms an insoluble substance, the decomposition is always more apparent, more complete, and most apphcable to dyeing purposes. Compounds which cannot easily be formed, directly by bringing their elements together, are often formed by means of double decomposition : thus carbonate of iron is difficult to form directly, but by mixing a solution of carbon- ate of soda with sulphate of iron, this compovmd is instantly formed, which may be thus represented — NaO CO,, FeO SO3 =-FeO CO,, NaO SO3, Application of Affinity — These double decompositions and re- compositions are of the utmost importance to the practical dyer, who should make himself thoroughly acquainted with all their laws and conditions; as it is, these formations of new and often insoluble compounds, wliich constitute a prominent feature in the production of colours, and every circumstance connected with this class of phenomena, favour this kind of reaction for practical purposes. It is a general law in ordi- nary atfinity, in the union of two elements, or of a com- pound with an element, such as dissolvhig a metal in acid, that there is always a great evolution of heat. This circum- stance would interfere with many dyeing operations, both upon the fibre and colour ; but in the double affinity referred to, 30 CATALYTIC INFLUENCE. where two compounds merely exchange elements, there is no quantity of heat evolved, to interfere with the dyeing opera- tions or fabric. The interchange of elements takes place quietly, so that the dyer may fix within the fibres of the most delicate material any compound required for the colour. C'li-cumstanccs influencing Afllnily.— The force of affinity is greatly influenced by the conditions in which the combining bodies are placed, as indicated when treating of light and heat. Where the atoms of any body are brought into contact with another body, under more or less favourable circum- stances, anything that diminishes the cohesion of the par- ticles, allows those of the other body to come into closer approximation, and therefore favours chemical union. Solid bodies, in general, are without chemical action upon one another, therefore, before any chemical change can take place, it is necessary to bring the substance into a fluid state. This is eminently necessary in all dyeing operations, not only for the purpose of causing combination, but to enable the particles to enter within the fibres of the cloth, and to be, while there, acted upon by the affinity of another body, also in solution, brought into contact with them. This is an essential condition of all dye drugs, and of all salts used in dyeing, either as dyes or mordants, and must never be lost sight of in studying either its philosophy or practical operation, as anything that interferes with the fre>3 operation of these conditions or solu- bility, necessarily retards the process or deteriorates the dye. Cainiyiic inHucucc— Another circumstance or power some- times occurring in dyeing operations, which interferes with or directs chemical affinity amongst the particles of bodies, is, that one body often induces a chemical change in another, while it undergoes no change itself This kind of affinity, or power, is termed Catalysis. A good instance of this is in fermentation : a little yeast put into beer induces fermentation in all the solu- tion, while the yeast is not altered. If we boil starch with dilute sulphimc acid, the starch is first changed into gum, and then into sugar. Yet notwithstanding these changes, the sulphuric acid is found imaltercd, either in property or quan- tity. A great many substances possess this property of cata- lytic influence ; and it is not unlikely that fibrous materials, such as silk, woollen, and cotton, possess it towards many of the vegetable colouring matters used in dyeing; indeed many oper- CONSTITUTION OF SALTS. 31 ations in the dye-house indicate the presence of some such power. The real nature of this power is not well understood ; only we know that bodies subject to change by catalysis have their particles held together by a weak affinity, and therefore changes are less or more easily eflected, accord- ing to the power exerted, to keep their elements together. The elements of many organic compounds seem held together by a balance of power among them, so that while another substance put into such a compound may possess a sufficient attraction for some of the elements in the compound, to disturb this balance of power, yet it may not have sufficient power to combine with them, but only cause the whole elements to re-arrange themselves in a new, and probably more stable, form. The study of such reactions is of the greatest interest ; and as these principles of action, in all probability, play a pro- minent part in the art of dyeing, it will be again brought under consideration, when describing operations where we think this action takes place. We may here mention, however, that the introduction of such a term as catcdijsis is only considered useful as bringing under one group a certain class of pheno- mena ; but indeed the same may be said of the no less useful term, affinity. When our knowledge of these hidden powers is more extended, all those phenomena may, perhaps, be ac- counted for, and ranged vmder the operation of some one universal power or law, of which at present we know only by particular terms. Constitution of Salts.— It may have been observed that, in describing the constitution of compounds and their nomencla- tvire, we grouped the elements together, as compounds, in a certain order, such as sulphate of protoxide of iron, FeO SO^. This formula, by its term and grouping, it may be farther ob- served, indicates that the sulphoric acid is combined with the oxide of the iron, and not directly with the iron itself. Now there is a difficulty which attaches to the nomenclature, that the formula is made to indicate a certain definite arrangement of particles, which is now pretty generally considered as incor- rect. However, it is not intended to enter here into the merits of the different views entertained by chemists regarding this point, but briefly to give a general idea as a guide to the workman. We will take sulphuric acid as our first illustration. The com- position of this acid is given as SO3, but SO3 is a solid crystalline 32 CONSTITUTIOX OF SALTS. compound, wliicli has no acid properties until it is combined with one proportion of water, being then SOJ + HO, or hydrous sulphuric acid. If into this acid we place a piece of iron, the reaction may be expressed thus, SO3 HO 4- Fe = SO3 FeO + H ; or as follows : — ' I H...- >^ .Hydrogen Gas. Sulphuric Acid, . . . SO3 . ~-^_^\,^^ Iron, Fe... ^^~~~r^^Protosulphate of Iron. Here we have water decomposed, to give an atom of oxy- gen to the iron, forming an oxide ; and then we have the acid combining with this oxide. The same principle of action is ascribed to all metals, and used to be described as a sort of disposing affinity. The acid SO3 is conceived to have such an attraction for the oxide of the metal, that it dis- poses both the metal to combine ynth oxygen and the oxygen with the metal, in order that it might unite with the two, to form a salt. Sir H. Davy, with his usual clear perception of all chemical phenomena, thought, that as sulphuric acid SO3 had no acid properties, and was incapable of combining with any body as such, except in union with water, it was more probable that what is termed hydrated sulphuric acid SOg-f- HO, may be the true composition of sulphuric acid, rather than SO3, and ought to be represented thus, SO4 -|- H. The hydrogen being the base or metal, and that its presence is an essential qualifi- cation to the acid, so that a piece of iron, being put into sul- phuric acid, will have a reaction as under, SO4 H + Fe = SO4 Fe + H .— Sulphuric Acid, I f-^ Hydrogen Gas. Iron, Fe.. -^^^^ -^ Sulphate of Iron. Here we have no supposed primary-disposing action, but the iron simply taking the place of hydrogen, by substitution, in virtue of SO^, having a stronger affinity for it than for the hydrogen. The same reaction explains the dissolving of any other metal in sulphuric acid. Names have been proposed in accordance with this theory, as, for instance, the SO4 is termed suljyhton; therefore, SO4 -f- H, instead of being termed sul- phuric acid, will be sulphionide of hydrogen, and sulphate of SALT RADICALS. 33 iron, sulphionide of irou. Such names will, however, be very difficult to be introduced into the science ; and although they were approved of, their use must necessarily be a matter of gradual growth. As the truths of these views become apparent, a new and improved nomenclature may grow up sponta- neously. The views given above, of the true formula of sulphuric acid, may be applied to all hydrated acids. Nitric acid of the formula NOj has never been isolated ; its existence is merely supposed from analogy. There is NO5 -|- HO, hydrated nit- ric acid ; but why NO^ -|- HO, rather than NOc + H ? Any metals dissolving in it only replace the hydrogen. The same with muriatic acid which is a compound of hydrogen and chlorine, properly termed hydrochloric acid. In dissolving a metal in this acid, the acid, not the water, is decomposed. Or if we put hydrochloric acid upon the oxide of a metal, as soda, the action is not that of the acid combining with the oxide, but there is a double decomposition and composition, represented by HCl HO + NaO = NaCl + 2 HO. So that bodies termed muriates are more properly chlorides. Salt Kadicals.— There is another thing necessary for the student to bear in mind, in reference to these views, and the nomenclature resting upon them. The SO4, NO^, &c., are called the Salt Radical, which term is often used in chemical books, and is applied equally to a compound, such as the above, or to an element, such as chlorine. It refers to any element, or compound, that will form an acid when combined with hydrogen, and a salt when united with a metal. There are a great many salt radicals Avhich ai-e compound substances, but which deport themselves in their reactions as elements. One eminent example of a substance of this kind is cyanogen, (C2N) which is the salt radical of Prussic acid, and which we will have occasion to notice when treating of the compounds of this acid and the ferro-prussiates, so much used in the dye-house. This view of the constitution of salts is much more simple than that of oxides combining with the acids, and, as it will be apparent, reduces the compound bodies, termed acids and salts, into one great class. It also enables us to account for a remarkable law which has been already noticed, namely, that bases, such as metals, always unite with the same number of proportions, or eqiaiva- c2 34 SALT RADICALS. lents of acids or salt radicals. Thus, if we dissolve protoxide of iron in sulphuric acid, one proportion of iron only com- bines with one proportion of acid, and is represented by FeO, SO4H = Fe SO4, HO. But if we take the peroxide of iron, and dissolve it in sul- phuric acid, we then have three proportions of acid, thus — Fe2 O3, 3 SO4 H = Fe. 3 SO.HO. It must, however, be borne in mind, that both theories re^ quire several hypothetical conditions to be taken for granted, to enable us to account for all the phenomena which take place in the actions of one body upon another ; and also, that both these views of the constitution of salts, as to the manner in which the atoms or particles arrange themselves, are liable to objec- tions. "We have stated the fundamental principles of these views, both as a general guide to the student in his inquiries into chemical science, and because we wiU have occasion to refer to them hereafter. But the reader who mshes to obtain more extended information, may consult such works as those of Graham, Liebig, Daniell, Gmelin, and others, who have given this matter much close attention ; and such research will be found amply to repay any labour and time expended upon it, for on the proper understanding of the fundamental laws of affinity depends, in a great measure, the proper application of chemical science to practical purposes, and more especially in such delicate operations, and with such materials, as the animal and vegetable fibres operated upon in a dye-house. ELEMENTARY SUBSTANCES. Oxygen (O. 8.) By referring to the table of elements, it will be found that several substances are therein named which many of our prac- tical readers have never heard of There are, indeed, a num- ber of elements of which little more is known than the fact of their existing in certain compounds ; they have only been seen by the discoverers and a few friends, and are as yet so rai'e, and found in such small quantities, that, under present circumstances, their application to any common branch of raanufocture is not thought of Sucli substances we will therefore pass over with a very short notice, and confine our- selves more to those that are, or, so far as their cost and quan- tities are concerned, may be brought into common use. The name of the element at the head of this chapter is a veiy familiar term in the dye-house, but is applied so indiscrimi- nately, and so often erroneously, to different substances, as to cause a considerable misunderstanding of its real nature and properties. Many of these erroneous applications of the name, and consequent confusion of ideas, will be noticed more ap- propriately under chlorine, with which gas, oxygen is often identified in the dye-house. Oxygen exists in Nature both free and combined : when free, it forms a colourless and transparent gas, without taste or smell ; it is a little heavier than common air, of Avhich it forms a part, and is dissolved or absorbed by water, in the propor- tion of from 3 to 4 per cent, by weight. Its wide range of aftinity for other elements, its presence in almost every com- pound, and the part it plays in nature, invest it with an im- portance not possessed by any of the other elements. It constitutes more than a fifth part of the atmosphere, as much as eight-ninths of the water, and fully half of the soUd crust of the globe ; and it is, besides, a prominent ingredient in all 36 UOW TO MAKE OXYGEN GAS. animal and vegetable bodies. The following table shows its numerical importance more precisely : — Water has 8 oxygen in 9 by weight. The Air, 3 ,, in 9 „ Crust of the Earth, 5 „ in 9 „ Animals and Vegetables, 7 „ in 9 „ How to make Oxfgen Gas.— The name oxygen was given to this element from the idea which the old chemists had, that it gave acid properties to its compounds. It was first recog- nized in this country as a distinct substance by Dr. Priestley, in the year 177-i, and about a year after in Sweden, by Scheele, without any previous knowledge of Priestley's dis- covery. It was obtained by Priestley by heating, in a retort, red oxide of mercury, which is thereby resolved into fluid mercury and oxygen. But other and more economical means are now adopted for its preparation, as follows : — An iron bottle is prepared, with an iron tube fitted into the mouth air tight, forming a retort ; into this a quantity of black oxide of manganese is put, and the bottle placed with its contents, into a good fire, with the open end of the iron pipe dipping into a vessel filled with water. The following figure shows the bottle in the fire, with the conducting pipe. Care must be taken not to allow any of the contents of the bottle to get into the pipe. "Wlien the bottle becomes red hot, bubbles of gas are seen to rise from the pipe through the water : these bubbles are oxj'gen gas, and may be collected by fiUing a bottle or jar with water, and holding its mouth downwards over the extremity of the pipe ; the gas, ascending into the bottle or jar, gradually displaces the water. In explanation of what is taking place within the retort-bottle in the fire, it may be stated, that black oxide of manganese is composed of Mn Oj ; the high heat drives off, or sets at liberty, a portion of the oxygen, and the manganese is converted PROPERTIES OF OXYGEN. 37 into a lower state of oxidation, so that 3 Ma O2 becomes Mn^ O3, Mn + 2 0. Another and more rapid method of preparing oxygen is, by taking equal parts of oxide of copper and chlorate of pot- ash, and placing the mixture into a small flask or test tube, fitted with a glass tube, as represented by the annexed cut. AVhen heat is appUed, by means of a lamp, a rapid evolution of gas takes place, very pure, and without any danger to the opera- tor. One ounce of chlorate of potash, treated in this way, will yield about 500 cubic inches of gas. The chlorate of potash is composed 01 KO CI O5, all the oxygen is set free, and chloride of potassium left. The oxide of copper undergoes no decomposition. The part it plays is not well understood ; but a practical use of its presence in this experiment is, to prevent fusion of the salt, which would take place, and is liable to break the vessel used. When the experiment is finished, and the flask cold, a little water will dissolve out the chloride of potassium from the oxide of copper, which, when dried, may be used again for a similar experiment. There ai'e a variety of other means of obtaining this gas, but they need not be detailed. Properties of Oxygen.— Oxygen is au eminent supporter of combustion. If a candle be placed in an atmosphere of this gas, it burns with intense brilliancy. Sulphur and charcoal being kindled, and placed in oxygen, give a vivid light, and there is formed sulphurous acid with the sulphur, and carbonic acid with the charcoal. If a piece of iron or steel wire be made red hot, and then immersed into oxygen gas, the com- bination is so rapid, that the heat produced causes the iron to scintillate, and the oxide to fuse, and drop off" hke water, sufficiently hot to melt or fuse china and glass. Many other metals burn in the same way as iron in this gas. It is upon this gas depend the processes of combustion and respiration; and the various functions of organized exist- ence, in aU its forms, are essentially connected and sustained 38 HYDROGEN. througli the agency of oxygen. Indeed there are few opera- tions in chemistry which are not in some way connected with oxygen, so that, under the A'arious heads in which we intend to treat our subject, its nature and properties will be constantly developed. Dyed fabrics, whether wet or dry, suspended in this gas, are not affected, a fact for the dyer to bear in mind when he is identifying this gas with chlorine. Htdeogen (H. 1.) Hydrogen is a gaseous element, never found free or un- combined in Isature, but is easily obtained from some of the compounds of which it is a component. Wlien pure, it is without smell or colour, and is the lightest substance known ; it is therefore used for inflating balloons. Its distinctive character as an element was fiirst pointed out by Cavendish, in 1766. It exists abundantly in nature, in combination with other elements ; it is a constituent of all animal and vegetable substances; and, being one of the constituents of water, it enters as such into the composition of almost all compounds. It is from the decomposition of water that hydrogen is generally prepared for experimental pm-poses. The pro- cess is simple. By putting some iron or zinc into a retort, and pouring over it a little dilute sulphuric or hydrochloric acid, the metal dissolves with effervescence, and tlie gas, in passing off, may be caught in bottles or jars over the pneumatic trough, as described for oxygen. Instead of a retort, a flask, or bottle, may be used, having a tube fitted by a cork in the mouth of the bottle, as represented by the annexed figure. The reaction which takes place, by the acid acting on the metal, is as we have before shown, (page 32,) SO4H + Zu = SO.Zn + H. We observe here that the change is only the substitution of the metal for the hydrogen in the acid. The use of the WATER. 89 water mixed with the acid is to dissolve the salt of zinc formed in the process, which requires a considerable quantity of watei\ From these and similar facts, hydrogen is sup- posed to be a metal existing in a gaseous form. At all events, its chemical character exhibits many of the properties possessed by the metals. Hydrogen, when prepared in the way de- scribed, has a slight smell, which results from impurities in the substances used, generally a small trace of arsenic, or sul- phur, in the metal. When iron is used instead of zinc, the smell is still more perceptible. Hydrogen is a combustible gas, and burns with a yellow flame, but does not support combustion. A burning candle immersed in it is instantly extinguished. When mixed with oxygen, and heat is ap- plied, the mixture explodes with a loud report, and water is formed by the union of the gases. Hydrogen does not support life. An animal immersed in an atmosphere of it soon dies. Several attempts have been made to breathe this gas, and some curious effects have been observed, but from incautiousness in not purifying the gas perfectly before inhaling it, two fatal accidents have followed. All such attempts are extremely foolish. Hydrogen combines with oxygen in two proportions, forming the protoxide or water, and peroxide or binoxide, a substance which has strong bleaching properties. ■W'atcr.— The discovery of the true composition of water was made by Cavendish in 1781, by burning known quantities of oxygen and hydrogen in a dry glass vessel, and observing that water was formed and deposited on the glass, and in quan- tity exactly equal to the weights of the gases which disappeared. He also found that these gases unite exactly in the propor- tion of two volumes of hydrogen with one of oxygen, and by weight, 1 to 8. Pure water is colourless and transparent, and has neither taste nor smell. It is eminently neutral, having neither acid nor alkaline properties, and does not alter the nature of sub- stances put into it. It often enters, however, into the compo- sition of compounds ; and many substances put into it have the property of decomposing it, and appropriating its ele- ments. The statement that water is entirely neutral, and having no action upon matters put into it, may appear doubtful to the practical dyer, as his daily experience teaches him, that the 40 WATER. waters he uses have a strong effect upon many of the dyes, and that certain kinds of water are better for some of his colours than others, which manifests a difference either in the condition or constitution of the water. This difference in vater, experienced by dyers, depends upon foreign matters Jissolved in it. It would therefore be a great object for the dyer to obtain pure water ; or, if this is not practicable, to know, what the ingredients are that are in the water he is using, so that he may either counteract their effects and escape their consequences, or render them subservient to his purpose. The great practical importance of water to the dyer is, not only its neutrality, but also its solvent power. The cohesion of solid bodies is thus overcome, and the particles are diffused through those of the Avater, and so placed in the best possible condition for combining with the particles of other bodies, brought into proximity with them. We may illustrate this by taking two solid substances that have a strong affinity for each other, say tartaric acid and carbonate of soda; mix them together dry, there will be no apparent action ; but if these substances be previovisly dissolved in water, and mixed, the action is violent and immediate. As may be supposed, there- fore, it is its great solvent powers that gives us impure water. Water is rendered pure by distillation. When caused to boil, it passes off as steam, and when steam is condensed by cooling, it is pure water, provided the impurities which were in the water before boiling do not fly off at a lower temperature than that of 212°. For instance, gaseous matters are expelled at lower temperatures, and alcohol, which boils at 180°, is also given off; but the impurities that are found in common water to affect the dyer are not given ofl^, except these be in the water in great quantities, as in leys, in boil- ing which, some of the soda or potash is carried away with the steam, as already noticed. The original source of all our water is from the surface of the ocean: it is evaporated, or vaporised, and carried through the atmosphere in the form of clouds, or in solution, and de- posited upon the earth as dew or rain ; but in this state it dissolves matters fronx the atmosphere, such as carbonic acid, ammonia, &c. ; so that i-ain water, especially if near towns, is not altogether free of impurities. Nevertheless, when far from towns, or after having fallen for some time to purify the WATER. 41 ait-, rain is the purest water in nature, but the moment it touches the earth, it dissolves some solid matters, and becomes contaminated with the ingredients of the soil over or through which it passes ; and these ingredients cause the differences experienced by dyers. The nature of the impurities depends upon the immediate source of the water, the nature of the soil or strata of earth through which it has passed, and as these substances act and react upon the dye-stuffs used, it be- comes of the first importance that the dyer should fully com- prehend the character and effects of the substances dissolved in the water he is using. These ingredients are generally lime, magnesia, alumina, potash, soda, ii-on, copper, sulphuric acid, hydrochloric acid, and carbonic acid. There are also other substances, which have been found in springs, in more minute quantities, but which we need not enumerate here, as they are not common ; and even some of these given, such as copper, are not often present in waters used in the dye-house. These earthy substances are generally found in the water com- bined as sulphates, chlorides, or carbonates. There are also gases present in all waters, as atmospheric air, carbonic acid, sulphm-ous acid, &c. The last named gas is easily detected by the smell, and water could not be used for dyeing containing an appreciable quantity of it. Copper will not be present except in the vicinity of a copper mine, or a copper-ore vein, which would not be a fitting locality for a dye-house. Iron, as a sulphate, or chloride, is often present in very minute quantity ; but when the quantity is considerable, the water is not good for many pvu-poses ; and, if the water is conveyed through lead pipes, or retained in leaden tanks, a small trace of lead may be detected, which is not only deleterious to the dyer's operations, but very destructive to health. One common definition of the quality of water is hard and soft ; but this expression, so far as regards the dyer, is somewhat ambiguous, and is only useful when alkahes and soaps are to be used. Distilled water is soft and pure, and useful for all purposes of the arts ; but a water may be soft and useful for bleaching and washing, and very deleterious in dyeing ; and it may be hard, and yet good for dyeing most colours. Such a term, therefore, does not denote any particular kinds of impurities. If a piece of pure white soap be dissolved^ in alcohol, not so strong as to form a jelly, and a little of 42 WATER. this solution be dropped into water, if tlie soap curdle.? the water is hard; if not, it is soft. If hard, the ingredients are of an acid or an earthy nature, such as carbonic acid, car- bonate of lime or iron, sulphate of hme, &.c. ; if soft, it may contain alkalies. The ingredients in the water are often so minute that the ordinary tests do not, for some time, detect them. The best mode of proceeding is to apply the soap test preliminarily, as a sort of guide ;* next, to try the water \\'\tl\ dehcately-prepai-ed test papers, and observe whether it has any acid or alkaUne reaction, then take a gallon of the water and boil it down to a pint ; put this into a narrow jar, and allow it to Settle for a few hours ; pour off the clear Uquid into another vessel, and retain the turbid remainder for exami- nation. The insoluble precipitate, if any, will most probably be carbonate and sulphate of lime, and a little iron. Car- bonate of lime is held in solution as bi-carbonate ; but the boiling decomposes this compound, one proportion of carbonic acid being given off, and the insoluble carbonate precipi- tates. The sulphate of lime is soluble only in small quantity, and a little is precipitated by boiling. To the precipitate add a few drops of hydrochloric acid, and the carbonate of Ume and iron will dissolve with effervescence, while the sulphate wUl remain undissolved. A drop or two of gallic acid added to the acid solution will detect iron, by gi\ing a black or bluish colour. A portion of this solution may be taken, and a httle ammonia added to neutralize the acid; if Ume is present, the addition of a httle oxalate of ammonia will give a white pre- cipitate. The pint of water boUed down is now divided into five dif- ferent portions, and put into small wine or test glasses. To one portion is added a few drops of gaUic acid, which, if iron be present, will, after standing some time, produce a bluish colour. To another portion add a few drops of oxalate of ammonia, which wiU give a white precipitate if hme is present. This should be heated a little. To a third portion add a few drops of phosphate of soda, and stir it well. After standing some time, if a white precipi- " The soap test for water has been carried out to a great extent, and probably to general practical use, by Professor T. Clark, (See his papers in the Chemical Gazette.) AVATER. 43 tate be formed, this will indicate the presence of mag- nesia. To a fourth portion add chloride of barium ; if a ■white pre- cipitate is obtained, -which is not re-dissolved by adding a little pure nitric acid, sulphuric acid is present. To the fifth i)ortion add nitrate of silver ; if a white pre- cipitate is formed, not re-dissolved by the addition of a little pure nitric acid, then hydrochloric acid is present. These tests, and the nitric acid used, of coiu-se, must be perfectly pure, or no dependence can be placed upon the re- sults. If carbonic acid exists in the water, which it does very commonly in combination with a base, it will be known, as already intimated, by the eftei'vescence caused by the addition of an acid ; but it may exist free ; and the best way to detect it, is to take a separate quantity of the water, without boiling, say a pint, and add to it a little clear lime water ; if milkiness appear, carbonic acid is present, either free or as bi-carbonate of lime. If blue litmus paper be reddened, there is free acid pre- sent in the water. This manner of proceeding, which is very simple, is suffi- cient to give the dyer an idea of the impurities he has to contend with. Of course, the effects of each of these separ- ately, or together, upon his dye-drugs, will also have to be studied ; but this we refer to the separate heads under which they natiu-ally fall. Should a more correct investigation be required, such as the exact quantities of each ingi-edient, this must be done by a regular course of analysis, which, we are afraid,, few practical dyers have the apparatus, or other means of making. However, with the tests referred to, a near approximation may be come at, by boiling the gallon of water to dryness, and carefully w'eighing the contents, which will give the whole solid matters in the gallon ; and afterwards, by dissolving this in distilled water, pouring off the solution, and drying the insoluble portion, the quantity of soluble salts, which may be those of potash, soda, magnesia, &c., will be found. The water is tested for these and all the other ingredients, by the tests given. To the remaining insoluble part, a few drops of hydrochloric acid are added ; and notice is taken if this produces effervescence. This acid solution is 44 WATEB. then diluted with distUled water, and tested as above ; if any thing remains insoluble, it is again dried and weighed, and the result ^vill indicate the silica present. The following table, from Parke's Chemical Essays, a book well worth perusal by practical men, will be a guide to the testing of water : — Test Used. "Will Detect. Oxalates, or oxalic acid. Lime, or its salts. Litmus. Uncombined acids. Turmeric paper. AlkaHs and alkaline earths. Chloride of platinum in al- \ r; u ^ ^ i 1 , ^ > oalts of potash. Nitrate of silver. Hydrochloric acid or chlorides. Salts of barytes. Sulphuric acid or sulphates. Lime water. Carbonic acid. Acetate of lead. ^Sulphuretted hydrogen in be- ( coming black, or sulphates. Chloride of hme. Carbonated alkaUes. Polished iron. Copper (is precipitated.) Phosphate of soda. Magnesia. For the particular eflPects of some of these tests, the reader is referred to the articles upon these substances. Water is used in the dye-house principally as a solvent ; but its solvent property depends upon certain laws. The action being the mutual attraction between the solid and fluid, it becomes weaker as the attractions are satisfied. If, for example, we take a piece of white sugar of lead, and immerse one small point of it in water, the liquid is quickly drawn up into its pores, and adheres to the particles of the salt. If more water than is merely sufficient to wet the particles is allowed to enter, the solid particles of the salt break down and disappear in the water; in other words, the salt is dis- solved. But this action of the water upon the salt is limited : it is very powerful at first, but the salt becoming diffused through the liquid, the action upon the solid decreases gradu- ally, until the water gets satisfied, and will dissolve no more ; the water is then said to be saturated. An important point in dissolving salts may here be noticed. In dissohing quantities of crystalhzed salts, such as alum, sugar of lead, &c., the custom is to put the solid crystals inlo M'ATER. 45 a vessel, and pour water upon them ; and a person keeps stirring until the whole is dissolved. This takes up much valuable time, and there is often a remainder of the salt not dissolved. If, instead of proceeding in this way, the quantity of water which it is necessary to use be put into the vessel, and the crystals of the salt be suspended iipon the surface, the solution would proceed much more rapidly, and more eco- nomically, than any other way. As the particles of water take up the particles of the salt, they become heavier, and sink ; other particles take their place, dissolve more of the salt, and sink in turn ; so that the action of a constant current of liquid is kept up on the suspended crystals, and always of that por- tion of the liquid most capable of dissolving. "When crystals of any salt are put into a vessel, and water poured over them and allowed to remain, they are a very long time in being dissolved ; as the water surrounding the crystals becomes satui'ated, and incapable of dissolving more, and from its weight it remains at the bottom of the vessel. This may be beautifully illustrated by taking three tumblers filled with ■water, and adding to each an equal weight of crystallized sulphate of copper. In the one let the crystals rest at the bottom, stir the other constantly, and let the third be sus- pended upon the surface of the water, the action will be seen, and the difference in time appreciated. In general, hot water dissolves more of a salt than cold water ; but the relation of different dissolving powers of water, at different temperatures, and for different salts, is very curious. Some salts dissolve equally at all temperatures, such as common salt. Some salts dissolve least in cold water, and increase gradually as the water is heated ; others, again, increase rapidly, until the water is at a certain temperature, and then become less soluble ; while other substances, such ae lime, dissolve most easily when the water is cold. Thus, 66 gallons water, at 32" Fah. dissolve 1 lb. lime ; but it will take 75 gallons at CO" Fah., or 128 gallons at 212°, to produce the same effect ; so that boiling water can contain only about the half of the lime that ice-cold water can. Thus, when lime water, at 60", which is about the maximum heat of water in summer, is boiled, a quantity of lime is deposited as the heat increases. This is often experienced in the raising of chrome oranges. 46 "WATER. The following table illustrates these remarks, and is of the greatest value to the dyer : — so 1 1 \\J/ U i i U Uf^ 1 1 1 y/ n 1 rru^d^r % 1 i ieV> i 1 1 rji^^i 1 CO 1 i 1 >v1 1 1 a*\V^ ^l' 1 1 1 k — — — 1 4V 1 1 i |p^.^r '~^\,'<^J^^^ d >-! i Ipr. — — — — ^/id^SSH^ =:=i-^ ^Pr l/l 1 1 o — 1 — 1 l/i 1 1 ; m 5 40 1 1 i t 1 \/ ^^rfS&Ti (.iit<^-i,le 0/ Sodium 1 ^1/; 1 1 1 1 1 ~'^ /I 1 1 : -^ . 1 1 '..^ i . £ <^^ / M 1 1 1 1 >^ '-^L'-i-i^ 1 1 IJ-^ /i/^) 1 i 1 1 i/r. ^'&=:^-ir:r-^^*v^- 1 30 .4*^ 1 1 1 _Ly I^f^ _ 1 1 1 1 1 1 m^^r^^n 1 1 1 1 1 Mill U„i_ 1 1 1 10 -r,^ ■—'^■f^\ 1 1 1 — ■ 1 1 1 1 1 1 i 1 1 ! 1 1 i M 1 SU^ 104^ 12 140= 15S^ YIS^ 194' 212° 230= It will be seen here that if a salt is dissolved in boihng water to saturation, and allowed to cool, a great quantity will be deposited either as crystals or powder ; also, if we wish to have a highly- saturated solution, there are certain tempera- tures better adapted for obtaining it than others. The best means is to use the salt dissolved in cold water, as above stated ; and the dyer, while he uses his stuff, as the salts of iron, alum, &c., should know that when he uses the full of a ladle, or pail, or small mug, he is taking exactly so many ounces or pounds of the salt, not so many measures, as is generally the case, without reference to the particular strength of the solution. The following table of the quantity of a salt dissolved in a gallon of cold water at saturation, wiU be an example of this : — Common salt, 4|-lb. per gallon. Sal-ammoniac, 3 J — Sulphate of copper, 4^ — Sulphate of iron, 7 — WATER. 47 Sulphate of zinc, 9^ lb. per gallon. Sulphate of nickel, 7i — Sulphate of soda, 4|- — Alum, 14 — Comparing this -with the diagram above, it will be seen that double the quantity of some of these salts is dissolved in boiling water. Besides the property for dissolving solid bodies, which we have been considering, water, as has been previously said, has also the property of dissolving gases, and hold- ing them in solution. In this case, cold water is a more powerful solvent than hot. Some gases, if held in solution by water used in dyeing, would be very deleterious ; and as many of these gases are often floating about in the dye-house, they may be absorbed by the water in small quantities, and be injurious, and the cause of the injury may not be known or thought of. The following are a few of these gases, and their solubility in water. 100 volumes, or cubic inches of water, at 60", will dissolve about 253 volumes of sulphuretted hydrogen, weighing 93.6 grains. 438 • ,, sulphurous acid, ,, 300. ,, 206 ,, chlorine, ,, lo5"7 ,, 100 „ carbonic acid, ,, 47"2 „ 76 „ nitrous oxide, „. 75. „ Any of these gases, in the water, will affect colours, and they are all, to some extent, gases given off in the dye-house. One gallon is equal to 277 cubic inches, so that each gallon is capable of holding in solution 259 "3 grains of sulphuretted hydrogen. 189 "7 grains of sulphurous acid. 431 "3 grains of chlorine. 130"7 grains of carbonic acid. 273" grains of nitrous fumes. Bin-oxide of Hydrogen. -Bin- oxide of hydrogen is a coloiu-- less hquid like water ; it has a metallic taste, and bleaches almost instantly all organic coloured substances. Its prepara- tion is dithcult and expensive. It is obtained by the decom- 48 MTEOGEN. position of the bin-oxide of barium ; the preparation of which is also difficult. There are so many minute precautions re- quired for the preparation of the bin-oxide of hydrogen, that almost no description which our limits permit would enable the student to prepai-e it ; these are all given in detail, by Thenard, the discoverer of the compound, in his " Traite de Cheiyiie," (vol. I., Gth edition.) Could there be any means of procuring it readily and cheap, its uses would be invaluable, both as a bleaching agent, and also for oxidizing, and many other operations in the arts. It is often referred to in proof that oxygen has bleaching properties as well as chlorine, a fact which will be noticed to some extent imder that element. Hydrogen combines with other elements besides oxygen, giving rise to important compounds, such as sulphuretted hydrogen, a gas we have just referred to, and others, which ^vlll be treated of under the separate elements with which it combines. Nitrogen (X. 14.) If a small vessel be floated upon water, with a piece of phosphorus in it, and this be set on fire, and a glass jar be inverted over it, as represented by the annexed figure, the flame is soon extinguished, and the wa- ter, when the air within the glass cools, rises into the jar. Let the whole stand tmtil the white fumes in the glass disappear, the remain- ing air in the jar wiU be found to differ entirely from common air ; a candle wiU not burn in it, and an animal put into it wovdd very soon die. This gaseous substance is nitrogen. The atmosphere is composed of oxygen and nitrogen : and the burning phosphorous combines with the former of these gases, forming phosphorous acid, constituting the white cloud referred to, which is absorbed by the water after a little time. The rising up of the water into the jar is NITROGEN. 49 to supply the place occupied by the oxygen consumed, and nothing but nitrogen remains. This element was first called azote — the life-destroyer — by its discoverer, Dr. Rutherford, from its not having the power of supporting life ; but the name was afterwards changed to nitrogen, on account of its being found to be the basic constituent of nitric acid, (aquafortis.) Nitrogen has neither taste nor smell, and is rather lighter than oxygen. Its use in the atmosphere is supposed to be for diluting the oxygen; but there is no doubt that other important purposes are served by its presence in the air, although we may be ignorant of them, as it forms an essential constituent of animals and vegetables, and also of many mineral productions. Nitrogen is peculiar for what are termed inert or negative propertie?. We cannot cause it to combine directly with any other element, as we do oxygen and hydrogen, or hydrogen and chlorine ; nevertheless, it combines with a number of ele- ments, when their compoimds are being decomposed. With oxygen, nitrogen forms a variety of interesting com- pounds, already alluded to (page 24), but which we will here notice more in detail, particularly those more commonly met with. As already remarked, the atmosphere is a mixture of nitrogen and oxygen, found to be in very nearly the same proportions under all circumstances and at all places, not in chemical union, but maintained in equal mixture by the prin- ciple of diffusion. There are a variety of methods for ascer- taining the proportions of oxygen and nitrogen in the air : the one just described, the bm'uing of phosphorus in an inverted jar over water, will suffice as an example. The results of careful investigations into this subject give as the constitution of the atmosphere in 1 00 parts : — 21 Oxygen. 79 Nitrogen. But, from the constant evaporation of water from the sea and surface of the earth, and the production, by many causes, of carbonic acid gas, which finds its way into the atmosphere, the air always contains a small portion of those ingredients, which, being taken into account, makes the composition — Oxygen, 20. Nitrogen, 79. D 50 BINOXIDE OF NITROGEN. Vapour of water, 0'9. Carbonic acid, O'l. 100-0 The dyer cannot fail to have observed a thin crust of solid matter upon the surface of his lime solution, bleaching liquor, and blue vats. This crust is the carbonate of lime, and is caused by the carbonic acid in the air combining ^Yith the lime, and forming an insoluble carbonate. The presence of this gas in the air has no deleterious effects in the dye- house, so far as we know, except its combining with caustic alkalies, if exposed, and deteriorating them. The oxygen of the atmosphere plays a very prominent part in the dye-house, and the knowledge of the true constitution of the air will make many of these phenomena better under- stood. This gas not being in chemical union with the nitrogen, there is no chemical force retaining and preventing it from acting upon other bodies, when brought under its influence. The principal compounds formed between nitrogen and oxygen are — Protoxide of nitrogen, NO. Deutoxide of nitrogen, NOo. Nitrous acid, NO3. Peroxide of nitrogen, NO4. Nitric acid, NO5. Some of these being of no known importance in the dye- house, we need do little more than refer to the condition in which they may be found. Protoxide of Niii-ogen is a gaseous body, and is easily obtained by distilling nitrate of ammonia in a retort, as de- scribed for obtaining oxygen (page 37), and collecting the gas as it escapes over water. It is known imder the appellation of laughing gas. Binoxide of Nitrogen is also a gaseous body, and is evolved when metals are being dissolved in nitric acid. When dis- solving iron or copper in nitric acid, in open vessels, as is done for the preparation of mordants, a dense red gas is seen to escape during the process. This red. gas is produced by the binoxide of nitrogen combining with the oxygen in the atmosphere, and forming a peroxide ; but when the metal is PEROXIDE OF NITROGEN. 51 dissolved in a retort, or other close vessel, as described for hydrogen, and the gas collected in a glass jar, it is found perfectly colourless. The following is the reaction which takes place when a metal is being dissolved in nitric acid and oxide of nitrogen evolved. Every three proportions of metal require foiir proportions of acid, one of which is decom- posed according to the following formula, supposing copper to be the metal dissolved : — 3 Cu + 4 NO5 = 3 Cu O NO5 + NOo. But, according to the theory of salt radicals (page 33), the reaction is the following : — 3 Cu X 4 NOcH = 3 Cu NOo + 4 HO, NO2. According to either view of the reactions Avhich take place, it will be observed that the proportions are the same, which may enable the dyer to guide himself in these substances when making nitrates of iron or copper. ivitroiis Acid. — This acid is prepared by taking four volumes of the binoxide of nitrogen, adding to them one volume of oxygen, and exposing this mixture to a low degree of cold : the gases, under these circumstances, unite, and form a greenish- coloured liquid, which is nitrous acid. As may be supposed, from the manner in which it is prepared, this substance is very volatile. If thrown into water it is decomposed. But it can be obtained by several means, in combination with bases, such as potash, soda, lead, &c., with which it is more stable. Peroxide of Nitrogen. — This compound is formed when the binoxide of nitrogen is allowed to escape into the atmos- phere, and constitutes the red fumes observed when dis- solving iron or copper in nitric acid. It is also obtained by distilling nitrate of lead in a retort, and allowing the fumes to pass into a bottle or flask kept cool by placing it in a freezing mixture, such as snow and salt. It condenses in this vessel, and forms a reddish-yellow liquid, which, however, passes off as gaseous fumes, by the slightest elevation of temperature. These fumes are very corrosive : they are fatal to animal and vegetable life and rapidly destroy all colours, and also the fibres of the cloth or yarn exposed to theii" action. The dissolving of metals in nitric acid should, there- 52 NITRIC ACID, fore, never be carried on vsathin or near the dye-house, or any place where goods are exposed. We have seen a Jitlle inat- tention to these precautions destroy the labour of several days, and this, too, when the destructive agent was hardly percep- tible to the senses, although its odour is amongst the most easily detected of gaseous compounds. This gas is also very suffocating and hurtful to health, and care should be taken that it is not breathed. It is its presence in nitric acid which gives that acid the reddish-brown colour which the aqua- fortis of commerce often has. Nitric Acid. — This acid exists abundantly in nature, in combination with other substances forming nitrates. We have said before that nitrogen and oxygen do not combine directly in the same manner as oxygen and hydrogen. There is no doubt, however, that the nitric acid which is found united with bases in nature, has been the result of the union of the oyxgen and nitrogen of the atmosphere. T^Tien a quantity of hydrogen is mixed ^Tith nitrogen in an open vessel and ignited, it burns rapidly in contact with the oxygen of the air, forming water ; and the water thus formed is found to contain nitric acid. If electric sparks be passed through air, confined in a vessel above a solution of an alkah, a portion of the alkali is converted into a nitrate. Rain which falls dur- ing a thunderstorm, almost always contains nitrate of ammonia. Ammonia is always being given into the air by the decompo- sition of animal and vegetable substances, and absorbed by the watery vapour ; so that when electric currents pass through the air during a thunderstorm, the nitric acid formed combines with this ammonia, forming a nitrate. In warm cUmates, where electric currents are abundant, the quantity of ammonia in the au- is considerable ; the formation of nitrate of ammonia is, therefore, proportionably great; and this, being washed down by the rain into porous limestone soils, is decomposed by the nitric acid combining with the lime and also with potash and soda, which are general constituents of soils, forming nitrates with these bases, and the ammonia is accordingly Uberated, either to be given to the air again, or taken up by plants, as a constituent of their food. In this way, immense beds of nitrates have been formed in the East Indies and in South America. In Chili and Peru, there are foimd large deposits of nitrate of soda upon the surface of the NITRIC ACID. 53 soil. Great quantities of nitrate of potash and soda are im- ported from these loctdities for the various manufacturing purposes of this country, where they are now extensively applied. The nitrate of lime and other earths, are converted into nitrate of potash, by mixing them with carbonate of pot- ash, before sending them to this country. Nitric acid is prepared from the nitrate of potash or soda, by decomposing it with sulphuric acid. This may be done, on a small scale, by putting a Httle of any of these salts into a retort, adding some sulphuric acid, and then applying heat. The beak of the retort is inserted into a receiver, which must be kept cool by causing cold water to drop upon it. The arrangement of the apparatus is indicated by the annexed figure. At the beginning of this experiment, red fumes of peroxide of nitrogen come oflP; but soon after a colourless liquid is seen to distil over, and drop into the receiver — this is nitric acid. The reaction which takes place may be repre- sented by the following formula. Na NOe + SO4H = Na SO4 + NO^ H. Nitrate of soda is now more generally used tliau potash, being cheaper, and having a lower combining equivalent, more nitric acid is obtained from a given weight. Thus, lOOlbs. of nitrate of potash give 621bs. of acid; while lOOlbs. of nitrate of soda would give 74lbs. The best proportion of sulphuric acid to use with nitrate of potash is 2 equivalents, whereas less suffices with nitrate of soda. Nitric acid is generally prepared, on the large scale, in iron cylinders, placed so that a fire plays round them. Into these 54 NITRIC ACID. cylinders are put tlie materials ; and the acid vapours which are distUled over are conveyed to the condensing apparatus by glazed earthenware pipes. The nitric acid of commerce has generally a hght-brown colour, caused, as before stated (page 52), by having a httle peroxide of nitrogen in it. Sir H. Davy drew out the follow- ing table of proportions of nitrous gas contained iu tliis acid, from its shades of colour. Thus, in 100 parts — ^ , . . , -^ Peroxide of Colour. Real Acid. Water. Xitrogen. A pale yellow has OOo 8-3 1-2. A bright yeUow has 88-9 8-1 2-9. A dark orange has 86"8 7"6 O'O. A hght olive has 86" 7'5 6'4. A dark olive has 85"4 7"5 7'4. A bright green has 84-8 7*4 7'7. A blue green has 88"6 7*4 8* This table must be considered to refer only to strong acid, for the colour is changed by dilution. Thus, when water is added to the dark orange-coloured acid, it changes it to a greenish-yellow. Exposure to the sun's light produces change of colour, by decomposing the acid, and liberating peroxide of nitrogen which remains dissolved in the acid. A little oxygen gas is, at the same time, evolved ; and, if the bottle is stoppered, will either drive it out or burst the bottle, a fact too often expe- rienced. Tlie great effect of hght upon this acid may be tried by placing a little of the colourless acid in the rays of the sun, and obser^'ing the change that follows ; this will show the propriety of keeping nitric acid always in the dark. Neither should it be exposed to the air, by leaving the stoppers out of the bottles or carboys, as it thereby loses its strength rapidly. The nitric acid, formed as we described, is often contam- inated with iron from the retorts, and also with sulphuric and hydrochloric acids, from a little common salt and other impurities being in the nitre used. It is purified from these matters by redistilling in glass retorts. The acid coming off first in the distillation contains some hydrochloric acid ; then notliing but pure nitric acid passes over, imtil nearly three- foiuths of this acid is distilled. But if the operation be NITRIC ACID. 55 pushed further, there is danger of impurities passing over. Of course, what remains in the retort contains the impurities. Sometimes the quantity of impurities in the nitric acid of commerce is very considerable, and very deleterious to the dyer. The general test applied to this acid in the dye-house is the specific gravity, taken by Twaddell's hydrometer ; but density is often given to the acid by dissolving a little nitre in it, or adding sulphuric acid. We have seen nitric acid, with 8 per cent, of sulphuric acid, giving it a high specific gravity. We have also seen it with as much as 5 per cent, hydrochloric acid. The presence of either of these acids is disadvantageous for the preparation of many of the mordants, as will be noticed under the proper heads. When nitric acid contains nitre, or any other salt dissolved in it, the impurity may easily be detected by evaporating to dryness a little of the acid, either iipon a piece of glass or a porcelain plate ; when the acid is pure, no residue is left. The presence of sulphuric acid is detected by diluting a small portion of the acid with four or five times its volume of distilled water, and adding a little solution of nitrate of barytes, which will give a white precipitate if sulphuric acid is present. Hydrochloric acid, or chlorine, may be detected by adding a Httle nitrate of silver to the dilute acid, which will also give a white precipitate if any hydrochloric acid be present. Iron is detected by adding a little gall water to the dilute acid, a bluish-black colour then appears. Or, if on eva- porating a small portion of the acid there is a residue of a brown colour, it indicates the presence of iron. After having tested for the presence of these substances, and finding the acid pure, or nearly so, then the specific gra- vity may be taken, as a further certainty of the value of the acid. This varies much with the acids of commerce, but is generally about 1-300 = 60" Twaddell, although it may be made as high as 1-500 = 100° Twaddell. Nearly all the hydrometers used in this country are those known as Twjid- dell's, which is an arbitrary scale. The true specific gravity may be reduced to Twaddell's, by dividing the fractional figures by 5, as will be observed from the above. But in trying the acids by a Twaddell's hydrometer, the above rule is to be reversed : we then multiply the degree of Twaddell by 5, add 1000, and divide the sum by 1000. Thus, supposing 56 NITRIC ACID. the specific gravity to be 60° of Twaddell, then 60 X 5 = 300 ; which, increased by 1000, becomes 1300 : and this, divided by 1000, gives 1'300, the true specific gravity. Or say 64°, Twad. which is a common number, then — (64 x 5 = 320) + 1000 = 1'320 specific gravity. The following table shows the quantity of acid in 100 parts, which may be called ounces or pounds, or any weight convenient, according to the true specific gravity. TABLE OF THE QUAJSTTITY OF ACID IN 100 PARTS BY WEIGHT. Specific Gravltv. 1-5000 .'., 1-4980.., 1-4960... 1-4940 ... 1-4910 .. 1-4880.. 1-4850 .. 1-4820.. 1-4790.. 1-4760.. 1-4730 .. 1-4700 .. 1-4670... 1-4640.. 1-4600 .. 1-4570... 1-4530.. 1-4500.. 1-4460.., 1-4424 .. 1-4385 .. 1-4346 .. 1-4306 .. 1-4269 .. 1-4228 .. 1-4189 .. 1-4147 .. 1-4107.. 1-4065 .. 1-4023 .. Acid in KK) parts. 100 99 98 97 96 95 94 93 92 91 90 89 88 87 86 85 84 83 82 81 80 79 78 77 76 75 74 73 72 71 Specifl 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 1 c Gravitv. •2947 '.. -2887 .. -2826 .. •2765 .. •2705 .. -2644 .. ■2583 .. •2523 .. •2462 .. •2402... •2341 .. •2277 .. •2212 .. •2148 .. •2084 .. •2019 .. -1958 .. •1895 .. -1833 .. •1770 .. -1709 .. •1648.. •1587.. •1526 .. •1465 .. •1403 . •1345 .. •1286 .. •1227 .. •1168.. Acid in IfiO parts. 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 33 32 31 30 29 28 27 26 25 24 23 22 21 NITRIC ACID. 57 Specific Gravity. Aciil in 100 parts. Specific 1-3978 70 1 1-3945 69 1 1-3882 68 1 1-3833 67 1 1-3783 66 1 1-3732 65 1 1-3681 64 1 1-3630 63 1 1-3579 62 1 1-3529 61 1 1-3477 60 1 1-3427 59 1 1-3376 58 1 1-3323 57 1 1-3270 56 1 1-3216 55 1 1-3163 54 1 1-3110 53 1 1-3056 52 1 1-3001 51 1 Gravitj'. 1109 .. 1051 .. 0993 .. 0935 .. 0878 .. 0821 .. 0764 .. 0708.. 0651 .. 0595 .. 0540 .. 0485 .. 0430.. 0375 .. 0322 .. 0267 .. 0212 .. 0159 .. 0106 .. 0053 .. , 100 parts. 20 19 18 17 16 15 14 13 12 11 10 9 8 7 6 5 4 3 2 1 The presence of free nitric acid in a solution is easily ascer- tained by the production of red ilimes when a metal is put into it, such as iron or copper ; or by adding to the substance sup- posed to contain it a drop of sulphate of indigo, and heating the solution to the temperature of boiling : the indigo will be discoloured if nitric acid is present. But if the acid is combined with a base, such as soda or potash, this test will not answer. In that case, the best mode of proceeding is to put a little sulphuric acid into the Uquid suspected, and then to add a crystal of sulphate of iron, (copperas.) If nitric acid be pre- sent, a ring of an oUve-brown coloured liquid will form round the crystal as it dissolves ; and by applying heat, the well- known smell of nitrous fumes is felt. By these simple means, the dyer can easily ascertain if nitric acid is present, either free or combined, in any compound with which he is working. The action of nitric acid on the dilFerent metals will be noticed under the proper heads ; but one remarkable cir- cumstance connected with this class of action must have been observed by most dyers when dissolving iron, namely, that c2 58 AjnioNiA. on putting the iron into the acid, it often remains without any action : when this occurs with new acid, complaints are made that the acid is bad or weak, or that something is wrong that prevents it dissolving the iron ; and not unfrequently have we seen carboys of acid returned on this account. Recently we had a sample of such acid, and found it to stand in specific gravity 1 -425 ; and to contain a mere trace of salts and sulphuric acid, with O'l per cent, of hydrochloric acid. It was a strong and comparatively pure nitric acid, which was its fault. The cause of the iron not being acted upon, is ii'om a condi- tion which iron is known to assume, termed the passive state ; in which condition acids do not act i;pon it. Strong and pure nitric acid places the iron in this state, and therefore it is not dissolved till the acid is diluted, or heat applied. We cite the above case as an illustration of the value a little atten- tion to chemical principles would be in many dye-houses, not only in saving money, but also preventing the manufacturer being necessitated either to adulterate or dilute his acid, in order to preserve a good and profitable customer. Xitric acid is very corrosive, from which property it was named aquafortis. It destroys all organic bodies, both veget- able and animal. It converts vegetable matter into oxalic, carbonic, and several other acids. Animal substances are acted upon by this acid, producing the yellow-coloured com- pounds, observed when it comes in contact wth the skin or nails. It should be used at all times with great care. Ammonia. — Xitrogen combines with hydrogen, and forms a very important compovmd, ammonia ; composed of one proportion of nitrogen and three hydrogen, NHj. Ammonia is abundantly obtained from the destructive distillation of organic matters containing nitrogen, such as bones, horns, skins, blood, and other animal matters. It is also obtained as a product in the gas-works. When animal matters are decom- posed by burning or putrefaction, ammonia is formed, and produces the disagreeable smell which these operations gene- rally give. The ammoniacal liquors obtained from gasworks, or by distiUing animal matters, are saturated \vith hydrochloric acid, which converts the ammonia into hydrochlorate of ammonia, (sal-ammoniac,) which crystaUizes in a very impure state. These crystals are collected and put into iron pots, set in a CHLORINE. 59 farnace lined with fii'e tiles, and having a large cover or head of lead fitted to them. Fire is applied to the pots, the sal- ammoniac sublimes and collects as a crust upon the leaden top, from which it is removed from time to time. Ammonia is prepared by mixing equal parts of slaked lime and sal-ammoniac, and applying heat. The lime combines with the hydrochloric acid, and the ammonia passes off as a gas, and is conducted by a pipe into water, with which it combines, and forms liquid ammonia. Ammonia, long known as hartshorn, is a strong alkali, and has a very pungent, sharp smell. It is an exceedingly valu- able re-agent in the laboratory, both as a test and for making many interesting salts by combination with acids, the greater number of which are volatile. These salts are, however, not much used m the dye-house. Ammonia is sometimes used for the preparation of archil, for bringing gut the colour. Its action upon ^ the colouruig matter of the woods is very powerful. It is the presence of ammonia and some of its salts in lurine, which gives that fluid the pecuhar properties for which it is used in the dye-house — as a cleansing agent for woollen, and for raising the colour of a decoction of log- wood. Nitrogen also combines with some of the other elements, forming compounds more or less interesting according to their applications, some of which will be noticed when treating of the elements with which these combinations take place. Chlorine (CI 36). Chlorine was discovered by Scheele, in 1774, and was called by him dephlogisticated muriatic acid. About eleven years after this, Berthollet considered that he had found it to be a compound of mui'iatic acid with oxygen, and hence termed it oxygenized muriatic acid — a name which was after- wards contracted into oxymuriatic acid. In 1811, Sir H. Davy discovered it to be a simple or elementary substance, and gave it the name of chlorine, from its having a greenish- yellow colom-. Chlorine has a very strong, suffocating smell, occasions violent coughing and debUity, and gives an astrin- 60 HTPOCHLOROUS ACID. gency to the mouth : therefore breathing it ought to be avoided as much as possible. Chlorine exists in nature in large quantities, in combination \vith other elements, particularly sodium, forming chloride of sodium (common salt). It is from this som-ce that it is pre- pared for use in the arts. If we mix about 8 parts of salt with 6 parts of black oxide of manganese, and add to this about 3 parts of sulphuric acid, a portion of the oxygen of the manganese combines with the sodium, and the chlorine is set at Hberty. The action may be thus defined : — CI Na, Mn 0-, 2 S04H = SO^ Mn, S04Na 2 HO, CI. Chi Chlorine Gas. Sodium Peroxide ] ol'^.V \ .Water. Manganese, 1 ^ _V^ Water. Common Salt, -< 2 proportions J SO^ X\^ \ SuIphate Soda. Sulphuric Acid, ] H (^ SO4 • ^Sulphate Manganese. Chlorine combines with almost all the elements, and fonns with them a series of compounds as numerous as they are im- portant. Its power of combining with, and decomposing, colom-ing substances is remarkable, and has given it a promi- nent standing in the arts. It combines with oxygen in vari- ous proportions, gi\*ing origin to several compounds, both usefiil and interesting to the dyer. These, as the following list shows, have all acid properties : — Hypochlorous acid, CI O. Chlorous acid, CI O4. Chloric acid, CI O5. Perchloric acid, CI O7. Bypochlorons Acid— This is a very tmstable compound, sup- posed to be connected with many of the operations of bleaching. It may be prepared by diffusing some red oxide of mercury in a httle water, and then introducing it into a bottle previously filled with chlorine gas. The chlorine is rapidly absorbed, and combines with both the mercury and oxygen. It pro- CHLORIC ACID. 61 duces, with the former, an insoluble oxychloride, and with the latter it forms hypochlorous acid, which is in solution in the water. This solution has a yellow colour, smells hke chlorine, and bleaches powerfully; but it cannot be kept for any length of time, even in the cold, but passes into chloric acid. Hypochlorous acid combines with alkaline bases, and forms hypochlorites, wliich also possess bleaching powers. It is generally supposed that when chlorine gas is passed through solutions of the aJkaUes, such as potash and soda, a similar de- composition takes place as that described of the oxide of mer- cury, and that the hypochlorite of the alkali is the bleaching salt formed. This salt is decomposed by heat. Chloroas Acid may be prepared by adding strong sulphuric acid to chlorate of potash. The process is a dangerous one, and we would not advise any student to try it, especially as neither the acid nor its salts are of any great importance. The acid is a gaseous body of a yellow colour : it combines with bases, and forms salts termed chlorites. These also possess bleach- ing powers, and are very vmstable. Chloric Acid. — This acid is not of any value in a separate form, and is obtained with difficulty ; but it is easily enough obtained in combination. When chlorine gas is passed through a solution of caustic potash, it is rapidly absorbed. This, by standing some time, or by the application of a little heat, be- comes converted into a mixed salt of chloride of potassium and chlorate of potash. Thus — 6 CI, 6 KO = 5 CI K, CI Oe K. The chlorate of potash being less soluble than the chloride, it is easily separated by crystallizing. Chlorate of potash has very strong detonating powers, and should be used with great care by the student, especially when mixing it with any other substance, as these are often explosive. It is extensively used for lucifer matches. We are not aware that this salt is used to any extent as yet in the dye-house ; but from the property it possesses of giving off oxygen easily, it may be made very usefi.ll in many operations, where oxydation is an object. It is becoming extensively used in calico print-works. Chloric acid combines with other bases besides potash. These compounds were for a long time, and are occasionally still termed hyper-oxymw^ates. 62 HYDROCHLORIC ACID. Hyperchioric Acid is formed from the chlorate of potash. It may be obtained in combination with potash, by acting upon the above-named salt with nitric acid, and putting the whole afterwards into a small portion of boiling water : on cooling, the hyperchlorate of potash separates in crystals. The acid may be separated from the base by boiling it with fluosilicic acid, when the hyperchloric acid remains in solution. This acid, or its salts, has no bleaching properties. It is an inter- esting compound in its chemical relations, but not yet of much importance to the arts. Hydrochloric Acid.— Chlorine unites with hydrogen, and forms an important compound, hydrochloric acid (muriatic acid.) It is a gaseous substance, very soluble in water, in which state it is used, and has been known since a very early period in history under the names oi' marine acid, spirit of salt, &c. Hydrochloric acid is easily obtained by the action of sulphuric acid on common salt. It is prepared on the large scale, by pouring vitriol on common salt, in a furnace pre- pared for the purpose ; the fumes passing off are absorbed by water, which thus becomes liquid hydrochloric acid, weak at first, but it is afterwards concentrated by distillation. The reaction going on during the preparation may be thus repre- sented : — NaCl SO, H = NaSO,, CI H. The sulphuric acid is generally used in a diluted state, so that there is always a great quantity of watery vapour passing oiF with the gas. This acid combines with bases, and forms a series of important salts. That from which it is obtained, viz. chloride of sodium, is a good example. It is matter of inquiry, as we have laefore stated, whether this acid be capable of combining with bases, or if it is not de- composed, and water formed along with the chloride of the base. As for instance, if hydrochloric acid be added to nitrate of silver, a white precipitate is formed, which, if collected and analyzed, will be found to be composed of chlorine and silver. Ag CI, not H CI and Ag O, the action having been — Nitrate of C N0«. Nitric Acid. Silver, 1 Ag.. Hydrochloric J H . . . Acid, 1 CI...- "Chloride of Silver. HYDROCHLORIC ACID. 63 But if we dissolve a piece of zinc in hydrochloric acid, and evaporate to dryness, we get a white powder, which, on analysis, will give zinc, chlorine, and water, in single equiva- lents. The question then is, whether these elements do not arrange themselves — — ^- Water. Chloride of Zinc. Forming: chloride of zinc with water. T^ Hydrochloric Acid. Oxide of Zinc Forming Muriate of Zinc. We have, at the risk of repetition, introduced this here, knowing that there is confusion in these names among prac- tical men, and have only again to state that all muriates should be properly termed chlorides. Some authors, to make a distinction, call salts that are in union with water, such as the zinc salt above, viuriates, and only dry salts, as that of silver, chlorides. The terms, when thus understood, may be used synonymously, so that no confusion need occur on that head. When hydrochloric acid is exposed to the air, it emits white fumes, which is hydrochloric acid gas with a little watei-y vapour ; hence exposure weakens the acid, and should be avoided as much as possible in the dye-house. This gas, besides, corrodes rapidly any substance it comes into contact with, and destroys colours. It is a colourless acid when pure, but exposure to the light renders it of a yellow colour ; strong sunshine decomposes it, and, of course, should be avoided. The common impurities in this acid are iron, sulphuric acid, and sulphurous acid. The iron may be detected by adding to a little of the dilute acid a drop of gallic acid. Sulphuric acid may be detected by adding a solution of chloride of barium to some of the acid diluted wath distilled water: which gives a white precipitate with sulphuric acid. If the clear solution filtered from this test be boiled with a little 64 HYDROCHLORIC ACID, nitric acid, any sulphurous acid will be converted into sulphuric acid, which wUl be precipitated by the barium, and its presence detected. Different chloride salts, such as common salt, are sometimes added to hydrochloric acid, to give it weight and specific gra\dty. This admixture may be detected by evaporating a little of the acid in a small porce- lain saucer, or on a piece of glass, and seeing if any residue be left. Pure acid should leave nothing ; if residue of a brown colour, it indicates iron. If the acid is found by these tests to be pure, then the specific gravity may taken to ascertain its strength. The following table will serve as a guide : — "^"20 1 %0%ant^' Specific Gravity. Muriatic Acid. 100 1-2000 40-777 90 1.1982 40-369 98 1-1964 39-961 97 1-1946 39-554 96 1-1928 39-146 95 1-1910 38-738 94 1-1893 38-330 93 1-1875 37-923 92 1-1857 37-516 91 1-1846 37-108 90 1-1822 36-700 89 1-1802 36-292 88 1-1782 35-884 87 1-1762 35-476 86 1-1741 35-068 85 1-1721 34-660 84 1-1701 34-252 83 1-1681 33-845 82 1-1661 33-487 81 1-1641 33 029 80 1-1620 32-621 79 1-1599 32-213 78 1-1578 81-805 77 1-1557 31-398 76 1-1536 30-990 75 1-1515 30-582 74 1-1494 30-174 73 ... 1-1473 29-767 HTDKOCHLORIC ACID. 65 Acid of Spec. Grav. 1-20 in 100 parts. 72 71 , 70 69 68 67 66 65, 64, 63 62 61 60 59 58 57 56 55 54 53 52 51 50 49 48 47 46 45 44 43 42 41 40 39 38 37 36 35 34 Specific Gravity. Muriatic Acid. 1452 29-359 1431 28-951 1410 28-544 1389 28-136 1369 27-728 1349 27-321 1328 26-913 1308 26.505 1287 26-098 1267 25-690 1247 25-282 1226 24-874 1206 24-466 1185 24-058 1164 23-650 1143 23-242 1123 22-834 1102 22-426 1082 22-019 1061 21.611 1041 21-203 1020 20-796 1000 20-388 0980 19-980 0960 19-572 0939 19-165 0919 18-757 0899 18-349 0879 17-941 0859 17-534 0838 17-126 0818 16-718 0798 16-310 0778 15-902 0758 15-494 0738 15-087 0718 14-679 0697 14-271 0677 13-863 66 CHLORroE OF NITROGEN. Acid of Spec Grav. 1-20 in 100 parts. 33 Specific Gravity 1-0657 Mnriatic Acid. 13-456 32 1-0636 13-049 31 1-0617 12-641 30 1-0597 . ... 12-233 29 1-0577 11-825 28 1-0557 11-418 27 26 1-0537 10517 11-010 10-602 25 1-0497 10-194 24 23 10477 10457 9-786 9-379 22 1-0437 8-971 21 1-0417 8-563 20 1-0397 8155 19 1-0377 7-747 18 1-0357 7-340 17 10337 6-932 16 1-0318 6-524 15 1-0298 6-116 14 1-0279 5.709 13 1-0259 5-301 12 1-0239 4-893 11 1-0220 4-486 10 10200 4-078 9 1-0180 3-670 8 1-0160 3-2G2 7 1-0140 2-854 6 1-0120 2-447 5 1-0100 2-039 4 1-0080 1-931 3 1-0060 1-224 2 1-0040 0-816 1 1-0020 0-408 t^hloride of iNiirogen— Chlorine combines with nitrogen to form NClj, wliich is one of the most explosive compounds known. It is a heavy liquid substance, and, from its dan- gerous properties, cannot be of any use to the dyer. Chlorine also combines with some of the other non-metallic elements, such as phosphorus, sulphur, carbon, &c., and BLEACHLNft. 67 forms compounds, some of which are interesting in a chemical point of view, but not in respect to their practical use in the dye-house. The chlorides of the metals, however, are some of them important, and will be described as they occur, under the metals. The great use of chlorine in the dye-house is as a bleaching agent — into the consideration of which we will now enter a little more in detail. While treating of light (page 12), we had occasion to notice the necessity of goods being a pure white previous to being dyed any light fancy * shade ; otherwise the natural yellow colour of the goods, whether cotton, silk, or woollen, would interfere with the particular shade wanted. If, for example, the shade required be a light pink upon cotton, and a little safflower, the stuff used for dyeing pink, be put upon it, un- bleached, the resulting colour would not be a pink, but a shade intermediate between a salmon and a brick colour, from the yellow ray reflected from the cotton mixing with the red reflected from the dye. We must, therefore, before dyeing a light pink, get rid of these yellow rays, and this is effected by the process of bleaching. Hence, the dyer must, of neces- sity be also a bleacher. Where and when the practice of bleachmg cloth first began, we have no account ; but we may reasonably suppose that, as soon as man became so far civilized as to manu- facture clothing, that the constant exposure of that clothing to the atmosphere, and occasional washing, would naturally suggest the idea of bleaching. However, we know that bleach- ing is of very ancient origin, mention being made of it in the oldest books extant. What was the nature of the process practised in these early times is not clear : but from the ear- liest description to the close of last century, no other process was known but alternate boiling, washing, and exposure to the atmosphere, a process which required a number of mouths to complete ; but, since the appUcation of chlorine to this pur- pose, an application which, as Professor Graham observes, " is one of the most valuable which chemistry has presented to the arts," the process is completed in a few days; nay, for the most of dyeing operations, in a few minutes. As many are now unacquainted with the routine of the * This is a technical term for fugitive colours, or colours not fast. 68 BLEACHING. process of bleaching previous to the introduction of chlorine, it may be worth while to give a short description of it, to illustrate the advantages obtained from the application of science to the arts. The first operation was that of steeping, which was merely immersing the yam in hot water or cold alkaline leys. When water was used, the steeping lasted for three or four days, but -with alkahne leys forty-eight hours were sufficient ; the goods were then washed, and boiled in an alkaline ley for four or five hours ; washed and exposed on the grass for two or three weeks ; again boiled or bucked^ which is a technical term for boiling ; wtished and crofted, a techni- cal term for exposing on the grass, as before. These alternate operations of bucking, washing, and crofting, were generally repeated four or five times, each time reducing the strength of the alkaline leys ia which the bucking was performed. The nest process was that of soiiring, which, tiU nearly the middle of last century, consisted in steeping the goods for several weeks in soured butter-mUk. This process was much shortened by Dr. Home, who suggested the use of sulphuric acid (vitriol) instead of milk ; and twelve hours, with a sour of this acid, were sufficient.* After the first souring, the operations of boiling, washing, souring, and crofting were repeated in regular rotation, untU. the yam came to a good colour, and was considered perfectly clear. A quantity of soap was generally used in the last operations of boiling. The num- ber of times these operations were repeated varied according to the quahty of the goods ; linen was seldom finished in less than six months, and cotton goods varied from six weeks to tliree months. Various opinions were advanced to explain the nature of the chemical changes induced during these operations : but such opinions could be only hypothetical so long as the com- position of the atmosphere and of water were not known, two substances which acted a very prominent part in these opera- tions, and also while we were ignorant of the nature of the colouring matter upon the goods, and its composition. We have already given the composition of water and air, but the com- position of the colouring matter upon cotton, &c. has not as yet been very accurately ascertained. Its properties are neutral, and of a resinous nature, from which, as a general principle, we • Home on Bleaching, BLEACHING. 69 may safely say, that the neutral is composed of hydrogen and carbon with oxygen ; and, from the composition of resinoiis matters in general, it will be composed of hydrogen and carbon, and soluble in alkalies and water, and therefore mostly all taken out by steeping and boiling. These resinous and colour- ing matters do not form a part of the cotton, but mechanically adhere to it, so that substances may act upon and decompose them without in the least destroying the cotton ; indeed, from a number of experiments, cotton is found as strong when de- prived of these substances as before. In boihng cotton yarn in water alone, it loses considerably in weight ; different qualities of cotton varying in this respect ; fine qualities lose least. From a number of experiments, made expressly to ascertain this point, and with various qua- lities of cotton, the average of loss may be taken at 5 per cent, of the weight of the cotton. In order to ascertain the chemical changes which take place when goods are bleached in the air, M. BerthoUet, finding that those seasons when most dew was deposited, were the most effective upon the colour, examined the dew which falls from the atmosphere, and also that which transpires from the grass, and found both to contain a sufficient quantity of oxy- gen to destroy the colour of turnsole paper.* Wlaat errors led to these residts we do not know, for although dew did contain oxygen, it would not give it acid properties to redden turnsole paper. Or whether M. BerthoUet considered the bleaching property of dew owing to its having free oxygen, or to this acid property, we do not know, not having seen the original details. Could we suppose the formation of peroxide of hydrogen (page 47), the effects would be easily explained. f The theory of croft bleaching has been explained variously as follows : — 1. The oxygen of the atmosphere combines with the colour- ing matter of the cotton, forming a new substance capable of solution in water or alkaUes, and comes off by washing or boiling ; or it combines with some of the elements of the colouring matter, such as the carbon, forming carbonic acid gas, which escapes into the air, or with the hydrogen, and forms water ; those elements which are left, form either colour- less substances, or substances soluble in the next operation. » Parke's Chemical Essavs. t See Ozone. 70 BLEACHING. 2. The oxygen combines directly with the colouring matter, forming a permanent and colourless oxide. 3. The water acts otherwise than being merely a solvent ; that it, or one of its elements, combines with the colouring substance producing the effects noticed in the first proposition. Hence dew being pure and free from any admixture which might retard this union, is better fitted for bleaching ; conse- quently, in seasons when most dew is deposited, the bleach- ing process will be accelerated. "Which of these theories is the true one, we cannot say ; but we know that light facilitates the process of bleaching, and this circumstance, we think, favours the supposition of the colouring matter being decomposed. Other interesting theories might be advanced from phenomena observed during the process of croft bleach- ing ; and also the part that boihng in alkali and the sours take in the operation. The modern process of bleaching, and that which is now almost universally practised, is by means of chlorine. This substance, as has been mentioned (page 59), was discovered by Scheele, who also described its peculiar property of destroy- ing vegetable colouring matters ; but M. BerthoUet was the first who called the attention of the public to its value as a bleaching agent, in 1785. About the time this chemist was prosecuting his inquiries into the nature of this substance, he was visited by the celebrated James Watt, to whom BerthoUet related the results of his experiments upon bleaching, and from this circumstance the inventor of the modern steam-engine became also the introducer of the new process of bleaching into this country.* The introduction of chlorine, as a bleaching agent, like all other discoveries which tend to overturn old practices, met with a host of opposition. The most prominent objections offered were, that it destroyed the cloth, did not give a per- manent white, and that it killed the men who wrought with it. These statements were not altogether groundless, but the force with which they were urged hastened improvements, and effected remedies. The first method of using chlorine was by saturating cold water with the gas, the water taking * Some give this honour to Professor Copland of Aberdeen ; but, from the evidence we have seen, it belongs to Watt, although the difference of time was little. BLEACHING. 71 up about twice its volume of it. The goods were put into this water, after which it was heated to drive off the chlorine, or set it free, that it might act upon the colouring matter ; but, the goods being impaired by this process, even when the greatest care was taken, suggested the diluting of the chlorine water ; w^hich diluted liquor was found to bleach equally well, and the goods were preserved. The defect of the goods be- coming yellow after a few days, suggested alternate boiling with alkaline leys ; and the difficulty arising from the work- men being unable to endure the effects of the escaping gas, led to the discovery that alkalies not only absorb a greater quantity of chlorine than water, but that they hold it with greater affinity, not allowing the gas to escape and affect the atmosphere, at the same time parting with it more regularly and effectively to the goods. The alkalies used were soda and potash, and each bleaching-work had its regular apparatus of retorts and carboys, or wooden chests, for the purpose of mak- ing their own chloride of potash or soda. This practice is still continued in many print-works, both in Scotland and England, for particular fabrics, or delicate operations, as it is considered much safer and better adapted for certain purposes than the common bleaching powder. In the year 1798, INIr. Tennant of Glasgow patented a process for using a solution of lime for absorbing the chlorine instead of potash and soda ; shortly after, the hydrate of lime (slaked lime) was substituted for lime-water, and this is the preparation now used for bleaching, under the names of bleaching powder and chloride of lime. Other minor improvements have been made regard- ing the quantity of chlorine absorbed by the lime under certain conditions, which will be noticed afterwards. Notwithstanding all these discoveries and applications, the real nature of the decolouring agent was still unknown : it was prepared by digesting together a mixture of common salt, per- oxide of manganese, and sulphuric acid. A decomposition took place, which was explained as foUows : — The sulphuric acid combined with the soda of the salt and set the nuu-iatic acid, which was in union with the soda, at liberty. The oxide of manganese gave off a part of its oxygen which combined with the free muriatic acid, and formed oxygenated muriatic acid, a name which was first applied to this new substance ; but after being introduced into the arts, this name was considered 72 BLEACHING. too unwieldy for common use, and was therefore contracted into oxy-muriatic acid. It was ultimately contracted, by the workmen, into oxygen^ and, notwithstanding the discovery of Sir H. Davy, in 1811, that oxy-muriatic acid was not common muriatic acid with more oxygen, but a simple body which he called chlorine, the name oxygen is stUl given to bleaching powder, and all its preparations. This is a serious evil to the workmen ; not practically, but for their own understanding ; as it identifies chlorine with oxygen, a substance which effects reactions in the operations of dyeing, quite distinct from that with which it is identified. We still rememljer the difficulty we were in when hearing that it was the oxygen of the air that supported life, and that it was the same oxygen which turned the green colour of the goods whUe in the vat, to blue when exposed to the atmosphere, and at the same time, seeing bleaching liquor, which w^as also termed oxygen, destroying blues, and felt that we could not breathe its gas but -with the greatest difficulty. To solve this puzzle, every chemical book we could find was examined for remarks on oxygen ; but, to our mortification, not one of these works alluded to its bleaching properties. We doubt not but many others have been in the same dUemma. The following order will show our chemical friends the ridiculous position in which dyers and bleachers place themselves by retaining such names : — " Glasgow, . " Messrs. * * Will please send, at their earUest con- venience a cask of their strongest oxygen, containing as near as possible 2 cwt., let it be newly made and dry: the last was damp, so that in a few days it became Hke as much clay, and lost the most of its strength. — Your attention ^vill obhge yours," &c. &c. The dyer will do well to turn to the article oxygen, and peruse it, and then the absui'dity of the above order will be observed. We are informed that chemic is a common name for bleaching liquor in many print-works ; and there are many names for other substances, equally unsuitable. We ■wUl give a table of these technical terms with their proper designations in another part of the volume. In the meantime we state that there is no better name for the substance we have been BLEACHING POWDER. 73 describing than bleaching powder, or, if in solution, bleaching liquor. Bleaching powder is prepared by exposing the hydrate of lime (slaked lime) to an atmosphere of chlorine gas till the lime ceases to absorb the gas. In practice, it is found that when the lime is in combination with an extra equivalent of water, it will absorb much more chlorine than when it has just as much water as slakes it. The chlorine is passed into large vessels or chambers furnished with shelves, ujjon which the lime is placed. Bleaching powder is white and pulverulent : it has a hot, bitter, and astringent taste, and a peculiar smell. W^ien digested in water, carbonate of lime and some other impurities remain. Some of the continental chemists first suggested that the chlorine was not merely absorbed and retained by the lime, but that it combined with it, and formed one or more definite compounds. This has led to a great deal of research, but scarcely to any definite conclusions, as there are various compounds of chlorine with oxygen which may be formed during the preparation of bleaching powder, and which possess bleaching properties as well as the chlorine alone. The most general supposition is, that hypochlorite of lime is formed, and that on this salt, and its decomposition, depend the operations of bleaching. This opinion is well-founded, and may be taken as expressing the true composition of bleaching powder, which is therefore to be regarded as a definite salt of Ume and hypochlorous acid, with chloride of calcium and hydrate of lime : * thus, CaOC10 + CaCl+ CaOHO. The best bleaching powder of commerce seldom contains above thirty per cent, of chlorine available in bleaching ; but there are few of the substances employed by the dyer or bleacher more liable to change ; indeed, from its first for- mation, there seems to be a constant chemical action going on between the chlorine and the lime ; oxygen is disengaged, and chloride of calcium formed, a substance which possesses no bleaching properties. These changes may be much re- tarded by keeping the powder perfectly dry, or by dissolving • Whoever is desirous of entering into the merits of the researches made upon the chemical character of bleaching powder, will find a series of valuable papers upon the subject, by Balakd, in the 2d volume of the General Records oj Science. E 74 BLEACHING POWDER. it in cold water, and keeping the solution excluded from the air. Chloride of hme (bleaching powder) does not attract moisture from the atmosphere, as is supposed by dyers, but when exposed, it is rapidly changed into chloride of calcium, a substance that is very deUquescent, and allowing that the lime previously contained two atoms of water, these combine with the chloride of calcium, when formed, and place this salt in the best circvmastances for attracting more water from the air, thus hastening the destruction of the remaining chlo- ride of lime. We have seen good bleaching powder by a little inattention reduced to this state in a few weeks, and its bleaching properties almost totally destroyed. As chloride of lime loses its. bleaching properties by stand- ing and several other circumstances, it is of the utmost con- sequence to the consumer that he should have some means of determining its real value, both for the sake of safety and accuracy in his processes, and its commercial worth. We have seen bleaching powder, which did not contain above ten per cent, of chlorine, charged and paid for at the same rate as that which contained thirty per cent. ; but not having the means of testing it previously, the quality was not discovered till the salt was in solution ; indeed, Ave are not aware of any relative prices according to the quality of this article, although with a very little care and trifling expense the dyer may know the value of the article he is about to pui-chase, and of course only pay accordingly. The first method of determining the value of bleaching powder was by sulphate of indigo, but the indigo solution alters by keeping, and is therefore objectionable. "Several exact methods," says Graham in his Elements of Chemistry^ " of which that in which sulphate of iron is used, appears to be entitled to preference. This method is based upon the circumstance that the chlorine of cliloride of lime converts a salt of the protoxide into a salt of the peroxide of iron. It is found by experience that ten grains of chlorine are capable of peroxidizing 78 grains of crystallized sulphate of iron. In an experiment to determine the per centage of chlorine in a sample of bleaching powder, some good crystals of protosulphate of iron (copperas) are to be pounded and dried by pressing between folds of cloth ; 78 grains are dissolved in about two ounces of water acidulated by a few drops either of sulphuric or muriatic BLEACHING POWDEB. 75 Q acid ; then 50 grains of the chloride of lime to be examined, are dissolved in about two ounces of water, by rubbing them together in a mortar, and the whole poured into a vessel graduated into a hundred parts. The common alkalimeter will do. This is a straight glass tube, or generally a very narrow jar about fths of an inch in width, and 14 inches high, mounted upon a foot, as shown in the accompanying figure, capable at least of containing a thousand grains of water, and graduated into a hundred parts. The jar containing the 50 grains of chloride of lime is filled up to the highest graduation by the addition of water, and the Avhole is well mixed. The clear part of this solution is gradually poured into the solution of sulphate of iron, tiU the latter is completely peroxidized. This is known by means of red prussiate of potash, which gives a blue precipitate with the protoxide, but not with the peroxide of iron. A white plate of porcelain or glass is spotted over with small drops of the prussiate ; a drop of iron solution is mixed with one of these after every addition of chloride of Ume ; and the additions continued so long as the prussiate drops are coloured blue. They may be coloured green, but that is of no moment. When the iron is peroxidized, the number of graduations or measures of chloride of lime required to produce that effect is noted ; the quantity of chlorine in the 50 grains of bleaching powder is now known, being ascertained by proportion. Thus, if it required 68 measures of the bleaching solution, then, as 68 is to 10, so 100 is to 14"7 the chlorine in the fifty grains of powder ; this being multiplied by two gives the per centage of chlorine in the sample, which is 29 '4." We have found, in operating in this way, a liability to lose a little chlorine as gas. This is obviated by having the iron solution in a stoppered bottle, and upon every addition of bleaching hquor to put in the stopper and shake the bottle. Another process has been recommended by Gay Lussac, which combines simplicity with accuracy, and is coming into general use with the manufactiu-ers of bleaching powder. A solution of arsenious acid is made in muriatic acid, and diluted with water. On adding a solution of chloride of lime. 76 BLEACHING POWDER. the muriatic acid takes the lime ; the chlorine decomposes the water, combining with its hydrogen, while the oxygen unites with the arsenious acid, and converts it into arsenic acid. "When the arsenious solution is tinged with sulphate of indigo, and bleaching liquor added, there is no change takes place on the indigo until the whole arsenious acid is transformed into arsenic acid ; but the first drop after this discolours the indigo. The correctness of this test is founded upon the knowledge of what proportion of chlorine is necessary to oxidize the ar- senious acid in the test solution. Various proportions have been proposed as the standard strength of the solution, but it does not matter much what proportions are used provided the operator knows what proportion of chlorine is necessary to transform it, and being careful always to have it the same. The best proportions for general use are those that require the least calculation. The following proportions we have found to do very well, and to be easily counted. Take one ounce of arsenious acid (common arsenic of the shops), and dissolve it by digestion for a few minutes at a boiling heat, in 24 ounces by measure of pure muriatic acid, then add 46 ounces by measure of distilled water ; but in case of any loss by evaporation during digestion, it is better to have a vessel which contains up to a certain mark 70 ounces, and when the acid solution is put into it, to fill up to the mark with water. This may be bottled and put past as the standard test Uquor. Every three ounces by measure of it are equivalent to twenty- five grains of chlorine. T^1len a sample of bleaching powder is to be tried, two hundred grains are carefully weighed and dissolved in the manner already described, in twice as much water as will fill the alkalimeter, or any other vessel graduated into a hundred parts. Tliree ounces of the arsenious solution are measured out and put into a glass jar or tumbler, and tinged with sulphate of indigo. The alkaUmeter is now filled with the bleaching liquor, which is added slowly to the arsenious solution, stirring constantly, and watching every drop that is added for the decolouring of the indigo. If the sample be so poor in chlorine that one measure of the alkali- meter ^vill not change the colour of the indigo, it may be filled again, and the process continued tUl the indigo is decoloured, and the whole number of graduations taken to effect this carefiiUy noted ; the fewer the number of graduations required, the richer the sample is in chlorine. Now, as every three BLEACHING POWDER. 77 ounces of the test liquor contain arsenious acid equivalent to 25 grains of chlorine, if the hundred measures effect the change of the arsenious into the arsenic acid, the value of the sample is exactly 25 per cent.; in other words, every four graduations taken to effect this change indicate one per cent, of chlorine. These equivalents were practically determined, and may differ a little from the theoretical calculation by atomic numbers, but the difference does not vary above half a per cent., and is not of much consequence in practice. The following table will serve as a guide to those who may adopt our proportions : — Mea- Per cent. Mea- Per cent. Mea- Per cent. Mea- Per cent. sures. sures. sures. sures. 150 16-66 127 19-68 104 2403 81 30-86 149 16-77 126 19-84 103 24-27 80 31-24 148 16-89 125 2000 102 24-51 79 31-64 147 17-00 124 20-16 101 24-75 78 32-05 146 17-12 123 20-32 100 25-00 77 32-46 145 17-24 122 20-49 99 25-25 76 32-89 144 17-36 121 20-66 98 25-40 75 33-33 143 17-48 120 20-83 97 25-77 74 33-78 142. 17-60 119 21-00 96 26-04 73 34-24 141 17-73 118 2118 95 26-31 72 34-72 140 17-85 117 21-36 94 26-58 71 35-21 139 17-98 116 21-55 93 26-87 70 35-71 138 1811 115 21-73 92 27-17 69 36-23 137 18-25 114 21-93 91 27-48 68 36-75 136 18-38 113 22-12 90 27-77 67 37-31 135 18-51 1'12 22-32 89 28-08 66 37-87 134 18-65 111 22-52 88 28-40 65 38-46 133 18-79 110 22-72 87 28-73 64 39-09 132 18-94 109 22-93 86 29-06 63 39-68 131 19-08 108 23-14 85 29-41 62 40-32 130 19-23 107 23-36 84 29-76 61 40-98 129 19-38 106 23-58 83 30-12 60 41-26 128 19-53 105 23-81 82 30-48 The above table includes almost the whole range of per centage of the bleaching powder of commerce ; but should the dyer meet with any not included in the table, the per centage may be calculated as follows. As the number of measures is 78 BLEACHING POWDER. to 100, so is 25 to the answer required. Say, for example, the measure is 160,— then 160 : 100 : : 25 : 15-62. Any of the two methods just described may be performed in a few minutes ; and in a substance that is Hable to such deterioration, it is surely of importance that the purchaser should have some knowledge of the quality of the article he is purchasing, and that the workmen know something of the strength of the substance they are working with. Might not a certain price be fixed for a standard strength of bleaching powder, and to rise and fall according to the per centage of chlorine which it contains, in the same manner as practised with soda ash? It would at least save much annoyance, and the common complaint, " that the last cask was not so good as the former." The average per centage of good bleacliing powder varies from 25 to 30 per cent. Were this average fixed at threepence per pound, which has been the constant price of bleaching powder these some years, then that which contains from 20 to 25 per cent, would be 2-^d., and from 15 to 20, 2d. per pound, while above 30 per cent, the value ought of course to rise in the same ratio. The adoption of some such plan, we are confident, would be satisfactory to all parties. To prepare chloride of hme for bleaching, an aqueous solution is requisite For this purpose a quantity is put into a large vessel filled with water, well stirred, and al- lowed to settle ; this is termed the stock liquor. There are no definite proportions for making up this vat : every bleacher makes up his stock-vat to a certain strength indicated by Twaddell's hydrometer, a most fallacious test, as the chloride of calcium, and evexy other matter which i§ soluble in water, although it has no bleaching properties, affects the hydro- meter. Care should be taken that this stock-vat be protected from the air as much as possible, as the lime absorbs carbonic acid, and the chlorine being set at liberty, occasions consider- able loss. This may be illustrated by putting a little of the solution upon a flat plate, and allowing it to stand a few days, when it wiU be found to have lost its bleaching power alto- gether. The first operation in bleaching cloth is steeping it in a waste ley, or tepid water, for a number of hours, generally over night : this is termed the rot steep : its object is to loosen the paste and dirt that may have adhered to the cloth BLEACHING POWDER. 79 during its manufacture. This steep ought not to be hotter than blood heat, otherwise, if oil be upon the cloth, it is not saponified, neither is it so easily taken out after ; in all cases when oil is observed, it ought to be taken out by rubbing it with soft soap and cold water previous to putting it into the steep. The goods are thoroughly washed from this steep in the dash wheel, but if a wheel is not convenient, they are tramped in water, and then washed by rinsing them through water with the hands ; they are then ready for the boiler. The boiling ley is made up by taking strong caustic ley (see soda and potash), a quantity equal to about six pounds Aveight of alkali to one hundred pounds weight of cloth, having as much water in the boiler as will allow the goods sufficient play when boiling ; they ought to boil for three hours. When goods are for Ught delicate colours, such as Prussian blues, the success of a bleach for such colours depends much upon a good boil. The goods are well washed from the boil, and allowed to drain ; the draining is facilitated by pouring hot water upon them ; they are then hanked up, taking out all the tAvists, and laid into the bleaching liquor as loose as possible. The vessels which contain this liquor are large, made either of stone or wood, and are termed bleaching vats, or tixjughs. To prepare this liquor, these troughs are filled with water, and a quantity of the stock liquor added until the required strength is obtained, which is indicated bj its action upon the sul- phate of indigo, in what is termed the test- glass, a vessel of this form. It is filled to the mark a with the sulphate of indigo, this in- digo is generally supplied by the manufac- turers of the powder as test blue, the liquor is added drop by drop until the colour of the indigo is destroyed ; the quantity taken to effect this is denoted by the graduations above ; the weaker the liquor, the greater the number of graduations required ; eacli of these graduations is termed its degree, two degrees are considered a fair strength for hght goods, but for heavy fabrics it may be made stronger ; they are allowed to steep in this for several hours, varying according to the nature of the goods. The objections we had to the use of sulphate of indigo as a test in the former case are equally applicable here. We have found 80 BLEACHING POWDEB. this test to be very uncertain. A much better method has been adopted by Mr. Walter Crum, a description of which was read by him to the Glasgow Philosophical Society, and published in the Report of that Society for 1841. We quote the foUomng important paragraphs of the paper : — " Chlorimetry requires to be practised by the bleacher for two purposes — First, he has to learn the commercial value of the bleaching powder which he purchases ; and with that view he can scarcely desu-e any thing better than the method either by arsenious acid, or green copjieras. But the more important, because the hourly testing of his bleaching liquor, and that on which the safety of his goods depends, is the ascertainmg the strength of the weak solutions in which the goods have to be immei-sed. If the solution is too strong, the fabric is apt to be injured. If too weak, parts of the goods remain brown, and the operation must be repeated. The range within which cotton is safe in this process is not very wide. A solution standing 1° on Twaddell's hydrometer, (spec. grav. 1.005) is not more than safe for such goods, while that of half a degree is scarcely sufficient for the first operation of stout cloth, unless it is packed more loosely than usual. When the vessel is first set with fresh solution of bleaching powder, there is little difficulty, if the character of the powder be known ; but when the goods are retired from the steepirig vessels, they leave a portion of bleaching Hquor behind, unexhausted, which must be taken into account in restoring the hquor to the requisite strength for the next parcel. The chlorimeter must, therefore, be applied every time that fresh goods are put into the hquid. It must, con- sequently, be intrusted to persons who may not be expert either in figures or in chemical manipulation. Hence all the processes I have described are too dehcate and tedious. " I introduced another into ovu* establishment some years ago, which has been in regular use ever since, and by which the testing is performed in an instant. It depends on the depth of colour of the peracetate of iron. A solution is formed of proto-chloride of ii'on, by dissolving cast-iron turn- ings in muriatic acid of half the usual strength. To ensure perfect saturation, a large excess of iron is kept for some time in contact with the solution at the heat of boiling water. One measure of this solution, at 40° Twaddell, (spec. grav. 1.200) is mixed with one of acetic acid, such as TujnbuU and Co. BLEACHING POWDEK. 81 of Glascrow sell at 8s. a gallon. That forms the proof solution. If mixed with six or eight parts of water it is quite colour- less but chloride of Ume occasions with it the production ot perL^etate of iron, wliich has a pecuharly intense red colour. "A set of phials is procured, 12 in number, all ot the same diameter. A quantity of the proof solution, equal to tth of their capacity, is put into each, and then they are filled up with bleaching liquor of various strengths, the first at ^tU ot a degree of TwaddeU, the second, ^ths, the third, -/^ths, and so on up to iSths, or 1 degree. They are then well corked up, and ranged together, two and two, in a piece of wood, in holes drilled to suit them. We have thus a series of phials showing the shades of colour which those various solutions are capable of producing. To ascertain the strength ot an unknown and partiaUy exhausted bleaching liquor, the proot solution of iron is put into a phial similar to those m the instrument, up to a certain mark, Jth of the whole, ihe phial is then filled up with the unknown bleaching liquor, shaken, and placed beside that one in the instrument which most resembles it. The number of that phial is its strength in 12ths of a degree of the hydrometer; and by inspecting the annexed table, we find at once how much of a solution ot bleaching powder, which is always kept in stock, at a uniform strength of 6 degrees, is necessary to raise the whole ot the liquor in the steeping vessel to the desired strength. " The instrument is formed of long 2 ounce phials cast m a mould ; those of blown glass not being of uniform diameter. The outside, which alone is rough, is polished by grinding, and in this state ^g they can easily be ^ e ,00 Be Be BB BP; .E l procured at 4 s. 6d. a dozen. They are placed two and two, so that the bottle con- taining the liquid to be examined may be set by the side of any one in the scries, and the colour compared by looking through the liquid upon a broad piece of white paper stretched upon a board behind the instrument.* • The above figure represents the instmment fitted •with tubes, which serve equally well. 82 BLEACHING POWDER. " To explain the table it is necessary to state that the steeping vessels we employ contain, at the proper height for receiving goods, 1440 gallons, or 288 measures of 5 gallons each, — a measure being the quantity easily carried at a time. In the following table, represents water, and the numbers 1, 2, 3, &c., are the strength of the liquor already in the vessel in 12ths of a degree of Twaddell, as ascertained by the chlorimeter. If the vessel has to be set anew, we see by the first table that 32 measures of liquor at 6° must be added to (256 measures of) water to produce 288 measures of liquor at Aths of a degree. But if the liquor already in the vessel is found by the chlorimeter to produce a colour equal to the 2d phial, then 24 measm-es only nre necessary, and so on. To stand t%" To stand t^° requires 32 measures. requires 24 measures. 1 _ 28 — 1 — 20 — 2 — 24 — 2 — 16 — 3 — 20 — 3 — 12 — 4 — 16 — 4 — 8 — 5 — 12 — 5 — 4 — 6 — 8 — 7 — 4 — To stand A" To stand t^° requires 16 measures. requires 12 measures. 1 — 12 — 1 — 8 — 2 — 8 — 2 — 4 — 3 — 4 — " Let us see Avhat takes place on mixing chloride of lime with protomuriate of iron. On the old view of the constitu- tion of bleaching powder — that it is a combination of chlorine and lime, we have — 3 (CaO, CI)) , . ( ^ S''^C1 6 FeCl C becommg 4 2 Fe^Clg ) . ( Fe^Os BLEACniNG. 83 the peroxide of iron forming peracetate with the acetic acid which is present. Or, supposing with Balard that when two atoms of chlorine unite with two atoms of hme, the product is CaCl + CaO, CIO, we have this formula : 3 CaCl ) (6 CaCl 3 (CaO, CIO) [■ becoming -{ 4 FcCls 12 FeCl ) (2Fe203 " Here one third only of the iron goes to form the deep coloured peracetate, while the whole might be employed for that purpose, by using protoacetate instead of protochloride. The latter however is preferred, from the greater tendency of the acetate to attract oxygen from the air, and consequently the greater difficulty of preserving it. Even with the chloride it is best to give out small quantities at a time, preserving the stock in well closed bottles." From this description it will be seen that the method recommended by !Mr. Crum may be adopted for testing the per centage of the powder, as well as the strength of the hquors. To return to the bleaching process. The goods being allowed to steep in the bleaching liquor for some hours, they are lifted and washed, after which, if they are thick stout goods, they are put into a sour for a little, then washed, and go through the same operations of boiling, liquoring, and souring, as before ; but for all common fabrics, we have found it the best practice to sweeten * the goods from the liquor, hank them anew, and put them back into a new liquor of the same strength for a few hours, wash them from this, and allow them to steep for an hour in strong sour of vitriol and water, about 1^ pint of the former to four gallons of the latter. There is perhaps no single branch connected with the art of dyeing upon which there is more difference of opinion than bleaching. Every one has some peculiarity of his own ; but, when the peculiarities are all compared, the difference in general is only nominal. One thing may be noticed, namely, the necessity of washing the goods well from the liquor before souring, as any Ume remaining upon the cloth will be formed into an insoluble sulphate, and resist the dye. Some main- » Building the goods on a drainer, and pouring water upon them till the •water ceases to taste of liquor as it comes from them is termed sweetening. 84 BLEACHING. taiu that this is of no consequence ; in our opinion, it depends wholly upon the colour which is to be dyed on the cloth. We have found that Hght pinlvs, light greens, light lavenders, and sometimes light blues, v/hen not vrashed well from the liquor, were often full of white spots, which we ascribed to that cause, although there are white spots often occurring both on yarn and cloth from other causes ; but, for other dark shades we found no difference, and for colours to be dyed with the bichromate of potash (chrome), such as yellows, ambers, and orange, we seldom gave them any sour, only washed from the first liquor, and then dyed.* Cotton, in the hank (yarn), when it is to be finished white, goes through the same process as cloth, with the exception of the 7'ot steep ; but, for dyeing, a quicker operation is adopted. All cotton yarn must be boiled in water for thx'ee or four hours previous to being dyed. Every lot of ten pounds weight, constituting what is termed a bundle, is divided into six equal numbers of spindles, and hung upon wooden pins about three feet long, and two inches thick ; this is termed sticking. The stock-liquor for yarn is generally prepared in a cask containing about 120 gallons of water; to this is added about 20 lbs. of good bleaching powder, stirred, and allowed to settle. A small tub of a size in which a bundle is wrought freely, termed a ten pound tub, is filled nearly two- thirds full with boiling water, and a bucket or ^)a?7/«Z (about four gallons) of the stock hquor added. The bundle is now let down as quickly as possible, and turned over for about ten minutes, after which it is put through a second tub of the same size, with water made a little sour by adding about an imperial gill of vitriol. It is wrought in this for about five minutes. Being then well washed, it is ready to be dyed of almost any light shade. By this method two men can bleach and wash two hundred pounds weight of yarn in about three hours, a quantity which, by the other process of boiling, steeping, and tiouring, would have occupied two days. Having detailed the present method of bleaching cotton goods for dyeing, we may say a httle upon the chemical nature of these processes. Previous to the discovery of the * In souring fine goods the vessel used is of consequence. In using a vessel lined with lead, there was experienced for a long tune a constant occurrence of small holes in the goods. On changing the vessel for a wooden one, this evil has entirely disappeared. The cause of the holes has ■ not however, been determined. BLEACUING. 85 elementary nature of chlorine, when that substance was con- sidered a compound of muriatic acid and oxygen, it was thought that the acid parted with its oxygen, and that this constituent bleached the goods in the same way as atmo- spheric air in croft bleaching, but more rapidly. When the true nature of chlorine was discovered, the theory was some- what changed ; finding, as was then supposed, that chlorine did not bleach except water was present, it was considered that the chlorine united with the hydrogen of the water form- ing muriatic acid, and that the liberated oxygen was still the bleaching agent. This theory is still maintained and supported by various analogies. We quote the following from Gregory and Liebig's edition of Turner''s Chemistry : " One of the most important properties of chlorine is its bleaching power. All animal and vegetable colours are speedily removed by chlorine, and when the colour is once destroyed, it can never be restored. Davy proved that chlorine cannot bleach except Avater be present ; thus dry litmus paper suffers no change in dry chlorine, but when water is admitted, the colour speedily disappears. It is well known also, that hydrochloric acid (muriatic acid) is always generated when chlorine bleaches. From these facts it is inferred that water is decomposed during the process, that its hydrogen unites with chlorine, and that decomposition of the colouring matter is occasioned by the oxygen liberated. The bleaching property of binoxide of hydrogen, and of chro- mic, and permanganic acids, of which oxygen is certainly the decolouring principle, leaves little doubt of the accuracy of the foregoing explanation." Another theory has been advanced, and equally if not more tenable, by which the chlorine is supposed to act directly upon the colouring matter. The following is from Sir Robert Kane's Treatise on Chemistry : — " Formerly it was considered that water was necessary for this bleaching, and that the chlorine combined with the hydrogen, while the oxygen of the water being thus thrown upon the organic substance, oxidized it, and formed a new body, which was colourless. I have shown, however, that tlys is not the case, but that the chlo- rine enters into the constitution of the new substance formed, sometimes replacing hydrogen, at others, simply combining with the coloured body, and in some, the reaction being so com- plete, that its immediate stages cannot be completely traced." 86 BLEACHING. This theory is also supported by several analogies, such as the action of chlorine upon indigo already noticed ; but Avhich of the changes, alluded to by Sir Robert Kane takes place during the bleaching of cotton, is not yet kno^vn. Chloride of lime, says the same author, does not bleach except an acid be present to combine with the lime, and set the chlorine at liberty ; but this is only conditional. It is true, that if blue litmus paper be put into a solution of newly dissolved chloride of lime, it is not bleached ; but if the solution be allowed to remain in contact with the air for an hour or two, the lime combines with the carbonic acid of the atmosphere ; and if the blue litmus paper be put into this solution, it is instantly bleached by the liberated chlorine. Cotton that has not been boiled in alkalis, is acted upon as the litmus paper in both cases ; but if the cotton has received a good alkaline boil, and is well washed, the bleaching process goes on, although the bleaching powder be newly dissolved. This shows that the alkaline leys effect a change upon the colouring matter. The nature of this change we are not as yet prepared to state : several opinions have been given, but they are hypothetical, and some of them are not borne out by practice. Neither is the theory of Sir Eobert Kane, of the formation during bleach- ing of a colourless chloride, or oxide, at all admissible, at least as regards cotton. According to this theory, goods being bleached by having formed upon them a new com- pound would become heavier, whereas practice shows that the operation of bleaching causes the goods to lose about 3 per cent, in weight. From several experunents which we made, we found that the loss by boiling was 5 per cent., and by bleaching 3 per cent., in all 8 per cent. Whenever the cloth is put into the bleaching liquor, there are acids formed, the principal of which is the hydrochloric ; but whether it is from the chlorine combining with the hydro- gen of the water, or the colouring matter of the goods, we cannot say, the latter we think most probable. Our opinion is, that the chlorme combines with the hydrogen of the colouring matter ; and according to a law we have several times alluded to, the remaining elements of the colouring matter form a new substance, which is soluble, and thus the whole colouring matter is taken off the cloth. In vats, where several hundred pounds weight of cotton have been bleached before changing the liquor, there is evidence of OZONE. 87 more substances remaining than merely a solution of muriate of lime ; but what these are, Ave dare not as yet ventui'e to assert. The effects of light in the operation of bleaching, also favours this hypothesis, for we know that exposure to the sun facilitates the process very much. This circumstance, how- ever, tells in favour of the theory that the oxygen is the bleaching agent, as well as in favour of the theory -which makes the chlorine the bleaching agent. There is only this diificulty, which, however, must not be overlooked, namely, that if a solution containing chlorine is exposed to the light, there is a decomposition of the water ; for the chlorine com- bines with the hydrogen, and liberates the oxygen of the aqueous molecule. The oxygen would again, by this theory, require to combine with the laydrogen of the colouring matter, and form water, a series of affinities which we cannot conceive, for if the affinity of the chlorine be stronger for the hydrogen than for the oxygen of the water, it would necessarily take the hydrogen from the colouring matter, seeing that oxygen, which by this showing has the weaker power, decomposes it to form water again, a series of reactions altogether irreconcUeable with one another. That the oxygen combines with the colour, forming a colourless oxide, is quite irreconcileable with the practical fact of the goods losing weight by bleaching. Such is an outUne of the processes of bleaching cotton goods for dyeing, as practised in most dyeworks at the present day. "Woollen and silk are bleached by exposing them after being boiled or scoured, to the vapour of sulphurous acid, which process will be noticed under sulphur ; but they are not thus bleached for dyeing. OsBone— Within these few years a substance, or property, which has got the name of Ozone, has been discovered to have extraordinary bleaching properties. If a few sticks of phosphorus be placed in a large bottle containing a little water at bottom, and corked, in a short time the atmosphere of the bottle is found to possess peculiar properties, and is said to contain ozone, and acts in relation to a great many substances the same part as chlorine. Professor C. F. Schon- bein, the discoverer of this substance, and who has made it the subject of careful investigation, was able to bleach, or decolour, svdphate of indigo, and also many flowers, by means of it. The real character of ozone is as yet only imperfectly 88 SULPHUR. understood. The discoverer supposes it to be a volatile per- oxide of hydrogen ; and this idea has been to some extent verified by experiments, while others suppose it to be a new condition of oxygen. However, enough is known of it to induce us to think that when easy methods of producing and applying it are discovered, ozone will be found of much value in the arts. Sulphur (S. 16). Sulphur has been known from the earliest ages. It is found in large quantities, uncombined, in the neighbourhood of volcanoes ; and is also extensively diiFused through nature in combination, especially with metals. It is obtained in great abundance by roasting the sulphurets of iron, lead, copper, and zinc. Sulphur is a hard, brittle, substance, of a greenish-yellow colour. It is not soluble in water, and is not changed by exposure to the air. When heated to the temperature of 170° Fah. it subUmes, and deposits again in the fine powder weU known as the Jioivers of sulphur. K heated in a close vessel, say a glass flask, to 218° Fall, it melts and becomes liquid as water, but by increasing the heat it undergoes some curious changes ; at 340° it begins to get thick, and assumes a reddish colour, and if the heat be continued, it becomes so thick that it will not pour from the vessel. At 482° it begins to become thinnner, and continues thinning until it boils at 750°. AVhen suddenly cooled fi'om its most fluid state, which is about 224°, by throwing it into cold water, it becomes instantly brittle ; but if cooled in the same manner, when thick (about 400°), it remains quite soft, and may be draNvn into threads. If heated in the open air to about 300° it takes fii-e, and bums with a pale blue flame, and give^ off most suffocating fumes of sulphurous acid gas. Sulphur combines with oxygen in several proportions, forming acids of considerable importance in the arts. These are: — Sulphui'ous acid SO2 Sulphuric acid SO3 Anhydrous Hyposulphiu-ous acid S2 Oj Hyposulphuric acid So Oj sniphnrons Acid is a gaseous substance, and is always pro- SULPHURODS ACID. 89 duced when sulphur is burned in the air, or in oxygen. It may be prepared also from the compounds of sulphur. If sulphuric acid be heated in contact with metallic copper, or charcoal, sulphiurous acid is given off. We have : — 2 SOi H and Cu = SO, Cu SO. + 2 HO If charcoal be used instead of copper in this experiment, carbonic gas is also liberated. It may also be prepared by heating together 3 parts flowers of sulphur, and 4 parts black oxide of manganese, in a similar apparatus to that described for the preparation of oxygen from manganese. This gaseous acid, as has been stated, is much used in bleaching animal substances, as silk and woollen ; and also some vegetable substances, as straw. For these operations the gas is procured by merely burning the sulphur in the air. The articles to be bleached are put into a chamber, or box, made as tight as possible, in which is placed a small pan of sulphur, which is kindled by putting into it a piece of red hot iron. The chamber is then closed, and the articles, damp and well spread out, are thus exposed to the sulphurous fumes. The gas is absorbed in the first place, by the water on the goods, and is thus brought into immediate contact, and enabled to combine with the fabric. Goods bleached by this gas are increased in weight, showing a combination ; they are not permanently white, showing that the compound formed is decomposed, indeed, the gas gradually escapes, and by immersing the goods in a stronger acid, the white compound is decomposed. This may be beautifidly illus- trated by exposing a red rose to the fumes of sulphurous acid gas, it is bleached white, but by putting it hito a sour (vitriol and water), the red colour is restored. This shows the distinctive characters of this gas and chlorine, as bleaching agents, and that any analogy drawn between them to support a theory is groundless. Some bleachers of woollen pass the goods through a solution of sulphurous acid in water, instead of stoving them. Bleaching by this gas is not done with goods that are to be dyed. Sulphurous acid passes readily into sulphuric acid by ab- sorbing more oxygen. In newly distilled water, or water having no air or oxygen dissolved in it, sulphurous gas may be kept a long time if well corked up, but without these precautions it very soon combines with the oxygen dissolved 90 StTLPHURIC ACID. ill the water. If a quantity of peroxide of iron is put into a solution of this gas, it passes into the state of sulphuric acid, and protoxide of iron. The formula is Fe2 O3 + SO2 = SO4 Fe + FeO Snipharic Acid is One of the most important of the compounds of sulphur ; it is not produced by the direct action of its elements, but generally from the oxidation of sulphurous acid. We mentioned when treating of nitrogen, (page 50) that the binoxide of nitrogen on coming into contact with the air combines ^vith more oxygen, and is converted into the peroxide of nitrogen ; and that this compound readily yields its oxygen again to other bodies which have a strong attrac- tion for it. If sulphurous acid is brought into contact with peroxide of nitrogen in the presence of water, a decomposition takes place, and there is formed sulphuric acid and nitrous acid, which may be represented by the formula, SO2 + N04=S03 + NO3 Crystalline sulphuric acid. O O O O N ~'~^ - Nitrous acid. One proportion of sulphurous acid. One proportion of peroxide nitroggn. SO, Both of these compounds when formed are taken up by the water, the first forming hydrous sulphuric acid, the second is decomposed, every three proportions being resolved into 3 N02=2 NO2+NO5 NO2 Binoxide of nitrogen. O^ ^ NO2 — ^^-^;r -Binoxide of nitrogen. NO, ^^""~^^ Nitric acid. 3 Proportions of nitrous acid, NO3 is resolved into The nitric acid remains in the water mth the vitriol, but the binoxide of nitrogen rises to the surface and imbibes oxygen, and is again converted into peroxide, ready to undergo again the same changes. On the large scale these changes and reactions are brought about by causing the sulphurous acid fumes from burning sulphur, and the peroxide of nitrogen SULPHURIC ACID. 91 fumes from pouring sulpliuric acid upon nitrate of soda or potash, to pass together into large leaden chambers along with a jet of steam. In this chamber the reactions above des- cribed "0 on. At the bottom of this chamber is a layer of water for absorbing the acids formed ; and at the top is an aperture to admit air, so that the binoxide of nitrogen becomes peroxidised as it rises to the top. The water from the bottom is drawn off at short intervals as it becomes impregnated with the acid. These intervals are so arranged that the specific gravity of the acid when drawn off is about 1-GOO = 120° TwaddeU. It is then evaporated in leaden tanks, until the specific gravity becomes about 1-76, or 1520 TwaddeU. If the operation were continued further, the acid would act upon the lead ; it is consequently transferred to vessels of glass or platinum, and evaporated until the specific gravity rises to about 1-847, or 169 V TwaddeU. The whole of the operation of making sulphuric acid may be done, for illustration, by the foUowing simple apparatus :— Generate sulphurous acid SOo in one bottle, (B) and peroxide of nitrogen NO, in another (C), and cause the t^^'o S^Jff ^ ^^ meet in a third bottle (A), having a little water at bottom the formation of sulphuric acid will go on as descnbed and be found in the water of the condensing vessel (A) alter tne operation. 92 SULPHURIC ACID. A great quantity of sulphuric acid is made by burning iron pyrites, a native compound of iron and sulphur. This mineral often contains arsenic, which the sulphurous acid car- ries with it into the acid-chamber ; and therefore the vitriol made from this source, contains arsenic as an impurity. Sulphuric acid may also be prepared by putting a quantity of sulphate of iron into an earthenware retort, and applying a strong heat to it; the sulphuric acid is distUled over, and peroxide of iron remains. This is the oldest method of obtaining sulphuric acid and is still practised in some parts of Germany. The acid so obtained is very strong ; has a dark colour, and gives off a quantity of white fumes ; hence it is called fuming sulphuric acid. It is also called Xordhausen acid, from its being manufactured there. When this acid is poured into cold water, it produces a hissing noise, like that produced by putting a red hot iron into water. This acid is excellently adapted for making sulphate of indigo. Sulphuric acid may be mixed with water in any propor- tion, but there seems to be certain definite quantities with which it will combine with water chemically. When added to water, there is always heat evolved ; this heat is a definite quantity, and accompanied by a condensation of bulk, as the dyer may easily convince himself by taking measured quan- tities of strong \-itriol and water, and mixing them ; when the mixture is cool, he will find a considerable diminution of bulk. The following experiments upon the amount of condensation, and heat given out, were performed with a common alkalimeter and thermometer. Measure of Measure of Heat n^hen Increase of Loss by con- Water. Acid. lulxed. heat. densation. 90 10 86° 40° 5 80 20 116° 70° 7 70 30 154° 108° 8 60 40 188° 142° ^ 50 50 210° 164° 11 40 60 212° 166° 11 30 70 200° 154° 9 20 80 164° 118° 8J 10 90 136° 90° 7 The above is the mean of three trials. The proportions SUI-PHDRIC ACID. 93 of acid and water were taken to make 100 graduations, and mixed. The heat was observed immediately after mixing, and the mixture was kept in a stoppered bottle until cold, when it was measured by the alkalimeter, and the loss by condensation noted. The heat of the water and acid separately, Avas 46°. The acid used was specific gravity 1-795, taken by Twaddell, 179°. Another proof that water and sulphuric acid form a definite compound is, that when the acid has the specific gravity of 1-78, the composition is SOJI + IIO. This, at a temperature of 32° will crystallise in large and regular crystals, while stronger, or weaker acid, at the same temperature will not crystallise. This is a circum- stance sometimes experienced in the dyehouse, and is com- monly taken as an evidence of impurity in the acid, which, however, it is not. The ordinary impurities in sulphuric acid are lead, nitric acid, arsenic, and sometimes sulphate of potash which is added to give it density. The presence of lead is easily detected by diluting a little of the acid with distilled water ; sulphate of lead is not soluble in dilute acid, and when present, there is produced a milkiness in the solution, as is often seen in the dyehouse when the acid is added to water. Nitric acid may be detected, as described page 57, by suspending a clean crystal of sulphate of iron in the acid, and heating it, a black ring is then seen, or the smell of peroxide of nitrogen perceived. Sometimes a little of this peroxide is present in the acid, and either of these impurities is very bad when the sulphuric acid is to be used for indigo, garancine, or any organic substance. Arsenic may be detected by diluting the acid, and passing a current of sulphuretted hydrogen through it, which gives a yellow precipitate wlien arsenic is present. This substance, however, is not deleterious in those operations of the dyehouse wherein sulphuric acid is used. Sulphate of potash, or soda, may be detected by putting a few drops of acid into a small basin, and saturating it with ammonia, then evapoi'ating to dry- ness, and continuing a strong heat until all white fumes of sul- phate of ammonia cease; nothing will remain if the acid is pure. After ascertaining that the acid is pure, the hydrometer may be used to discover its strength. The following table will be useful in this operation : — 94 SULPHURIC ACID. Liquid acid. Specific gravity. Dry acid 803 in 100 parts. Liquid add. Specific gravity. Dry acid S03 in 100 parts. lUO 1-8485 81-64. 50 1-3884 40-77 99 1-8475 80-72 49 1-3788 39-95 98 1-8460 79-90 48 1-3697 39-14 97 18430 7909 47 1-3612 38-32 96 1-8400 78-28 46 1-3530 37-51 95 1-8376 77-46 45 1-3440 36-69 94 1-8336 76-66 44 1-3345 36 88 93 1-8290 76 83 43 1-3-256 35-06 92 1-8233 7502 42 1-3165 34-25 91 1-8179 74-20 41 1-3080 33-43 90 1-8115 73-39 40 1-2999 32-61 89 1-8043 72-57 39 1-2913 31-80 88 1-7962 71-76 38 12826 30-98 87 1-7850 70-94 37 1-2740 30-17 86 1-7774 70-12 36 1-2654 29-35 85 1-7673 69-31 35 1-2572 28-54 84 1-7570 68-49 34 1-2490 27-72 83 1-7465 67-68 33 1-2409 26-91 82 1-7300 66-86 • 32 1-2334 26-09 81 1-7245 66-05 31 1-2260 26-28 80 1-7120 65-23 30 1-2184 24-46 79 1-6993 64-42 29 1-2108 23-65 78 1-6870 63-62 28 1-2030 22-83 77 1-6760 62-78 27 1-1956 22-01 76 1-6630 61-97 26 1-1876 21-20 75 1-6520 61-15 25 1-1792 20-38 74 1-6415 60-34 24 1-1706 19-57 73 1-6321 59-52 23 1-1626 18-75 72 1-6204 68-71 22 1-1649 17-94 71 1-6090 57-89 21 1-1480 17-12 70 1-5975 57-08 20 1-1410 16-31 69 1-5868 56-26 19 1-1330 16-49 68 1'5700 65-45 18 1-1-246 14-68 67 1-5648 64-63 17 1-1165 13-86 66 1-5503 63-82 16 1-1090 13-05 65 1-5390 53-00 15 1-1019 12-23 64 1-6280 52-18 14 1-0953 11-41 63 1-5170 51-87 13 10887 10-60 62 1-5066 50-55 12 1-0809 9-78 61 l-49t0 49-74 11 1.0743 8-97 60 1-4860 48-92 10 1-0682 8-15 59 1-4760 48-11 9 1-0614 7-34 58 1-4660 47-29 8 1-0544 6-52 57 1-4560 46-48 7 1-0477 5-71 56 1-4460 45-66 6 1-0405 4-89 55 1-4360 44-85 5 1-0336 4-08 54 1-4265 44-03 4 1-0268 3-26 53 1-4170 43-22 3 1-0206 2-45 62 1-4073 42-40 2 1-0140 1-63 61 1-3977 41 •.58 1 1-0074 0-82 HYPOSULPHUROUS ACID. 1)5 The presence of sulphuric acid is detected by adding to any compound in solution a salt of barium, which gives a white precipitate not soluble in nitric acid. Sulphuric acid has a strong attraction for water, so much so, that if left exposed to the atmosphere, it will absorb moistiire and become dilute. A saucer half filled with strong sulphuric acid will become full in a few days by exposure to the atmosphere of a dye- house. This shows the evil of leaving the stoppers out of the bottles, or as is often the case, leaving quantities of this acid in an open jug. Animal and vegetable substances put into sulphuric acid become charred ; the hydrogen and oxygen of these bodies go to form water, which combines with the acid, and the carbon is left as charcoal ; this is the effect it pro- duces upon the skin. The presence of these matters also tends to weaken the acid, and should therefore be avoided as much as possible. This may be the proper place to refer to a bad practice we have seen in the dye-house. When using vitriol, the jug containing it is often placed upon the floor for convenience, and a workman passing that way comes against it with his foot, and not only spills the acid, but occasionally his shoe is filled with it. AVhen this happens, the first impulse, which is often obeyed, is to plunge the foot into water,. when, of course, the mixture of vitriol and water in the shoe is brought nearly to the boiling point, as may be learned from the table above. Severe accidents by this reck- less habit are not uncommon. When such an accident does take place, the person ought to take off his shoe and stocking before putting his foot in water ; and if his foot has been previously dry, or merely moist, he will escape unhurt. The hand, if dry, may be kept in strong vitriol for some time without biirning, but very shortly the acid begins to decom- pose the skin, and then pain is felt. llrposniphuroas Acid.— This acid is of singular composition ; although it is composed of equal equivalents of sulphur and oxygen, what might be termed SO, yet it is represented double S2 O2. This seeming anomaly is got over by supposing it to be a compound of sulphurous acid with sulphur, thus : SO^-l-S. This acid is not prepared directly from its elements, but is formed either in combination as a salt, or by double decom- position. If a current of sulphurous acid gas SOj, and sulphuretted hydrogen gas SH, are passed through water 96 SULPHURETTED BYDROGEN. together, four parts or equivalents of the former, and two parts or equivalents of the latter, combine to form three equiva- lents of hyposulphurous acid, and two of water. The formula may be accordingly this :— 480, and 2SH = 88028 2H0. The acid when uncombined is very unstable ; after exposure for a short time it deposits sulphur, and sulphurous acid remains. "UTaen a solution of soda or potash is boiled with sulphur, there is formed in the liquid hyposulphate, and sulphuret, of the base, supposing that soda is employed, then four propor- tions of sulphur, and three of soda, produce One hyposulphite of soda XaO 82O2 and Two sulphuret of sodium 2NaS. The hyposulphites are not yet much used in dyeing ; but from the property which the alkaline salts of this acid has of dissolving many metallic oxides, it might undoubtedly be advantageously applied for several purposes. Hyposuipharic Acid — This acid is easily formed in combina- tion by passing a current of sulphurous acid through water in which is difiused a quantity of black oxide of manganese ; two proportions of the acid combine with one proportion of oxygen from the manganese, and form the hyposulphuric acid, which combines with the remaining manganese to form the hyposulphate of manganese : — Mn02 2S02=MnO S2O,. This acid may be obtained free from the manganese by precipitating that metal, but cannot be freed from water. Its hydrate is moreover very unstable, but in union with bases it forms salts of great stability. Salphiiretted Hydrogen.— Sulphur combines with hydrogen in equal equivalents, and forms a gaseous compound very useful as a test — this is sulphtu-etted hydrogen, or sulphide of hydrogen, which is not inappropriately termed hydrosulphuric acid, as the gas has acid properties. This gas is prepared by acting upon a metallic sulphuret, with an acid in this manner : — a few pieces of proto-sulphuret of iron are put into a glass or porcelain vessel containing a little water, and a small quan- tity of sulphuric or hydrochloric acid is added ; a gas of a strong, suffocating smell immediately begins to come off, which SULPHURETTED HYDROGEN. 97 is sulphuretted hydrogen. The reaction which takes place is as follows : — -^ Sulphide of hydrogen. Sulphate of Iron. Sulphuret of iron, \ ^ Sulphuric acid, '\iic\ This gas is absorbed by water, and is sometimes used in solution as a test. It is also taken up in great quantity by a solution of ammonia, forming hydrosulphurct of ammonia, also much used as a test. When used for this purpose in the gaseous state, such an appara- tus as the accompanying will serve. The sulphuret of iron, or other sulphuret, is put into the bottle a, containing some water, and the acid is added by the long funnel d. The gas escapes by the tube c, f, and passes through the solution to be tested, contained in the glass g. The same apparatus serves for passing the gas through water or liquid ammonia, wlien it is required to produce a saturated solution. The precipitates formed by passing this gas through solutions of vai'ious substances, are very charac- teristic. Thus, a solution containing — Antimony produces Orange precipitate. Tin and Arsenic Yellow precipitate. Manganese Flesh red precipitate. Zinc "White precipitate. Lead, Copper, Iron, &c Black precipitate. Sometimes, however, it is necessary to add a little ammonia before these results are obtained. Sulphuretted hydrogen is evolved from decaying animal and vegetable matters, and from dunghills, common sewers, and putrifying bodies that contain sulphur. It is very deleterious / 1 (2. % %'^ 98 PHOSPHORUS. to health, and care should be taken to avoid breathing it. The effect of this gas upon many dyes is so very great, that the slightest quantity in the atmosphere is hurtfuL It gives to chrome yeUows and oranges, a smoky appearance, which cannot be removed ; and to spirit reds, it gives a rusty browTi appearance. Wherever, indeed, there is a metal present in the dye, this gas affects the colour. Sulphur does so also, consequently the same effects are often produced by burning sulphury coals in a drying stove. We have seen a whole stove-charge of goods, yam and cloth, spoiled in this way ; the colours appearing as if dried in smoke, and the watchman superintending the stove, notwithstanding his protestations that there was no smoke, compelled to bear the blame of negligence. Sulphur combines with hydrogen in ^lother proportion, and forms a bisulphuret HS*, which is an oily liquid of no known importance in any process of tLe dyehouse. Selemoi (Se 39-5). This element very much resembles sulphur in its properties, and in some of its combinations. It is solid, of a dark brown colour and metallic lustre ; and is found in nature in combination with some of the metaUic sulphurets, as those of copper, silver, lead, &c. It is very rare, and as it has only been obtained in minute quantities, it has not yet been intro- duced into the arts, or appUed to any useftil purpose. Phosphorus (P 32). Phosphorus is a soft, solid substance, of a light amber colour, and insoluble in water. It is very abundant in nature in combination with other substances, but principally with lime in the bones of animak . It is exceedingly inflammable, oxidates rapidly when exposed to the air, and emits light visible in the dark, from which circumstance it derives its name. It b manufactured from the bones of animals, by various compUcated methods not veiT easily imitated on a small scale. This element unites with oxygen in various proportions, IODINE. 99 and most of the compounds formed have acid properties, as : — Suboxide of phosphorus, . . .P2O. Hypophosphorous acid, PO. Phosphorous acid, PO^. Phosphoric acid, PO,,. These acids all unite with bases, forming salts which are interesting in their relations to each other, and also to salts of other acids. Phosphoric acid and the phosphates, evince peculiar properties in combining with various proportions of water, and producing compounds which differ characteris- tically from one another. These combinations have been extensively investigated by Professor Graham and other chemists. We are not aware that any of these salts are used in the operations of dyeing, except in so far as they constitute a portion of the salts in dung, and the substance called dung substitute, used in dyeing turkey reds and other madder colours. Phosphorus combines also with hydrogen, nitrogen, chlorine, and sulp])ur, and likewise with many of the metallic elements forming the class of compounds termed phosphurets, or phosphides. Iodine (I 127-1). Iodine is obtained from the ashes of sea weed. The ashes are put into water, and the soluble portions are withdrawn, and boiled down. During the process common salt and other salts are deposited and withdrawn ; and when the liquid is reduced to a very small quantity and attains a dark coloui', a little sulphuric acid is added ; the whole is then allowed to remain at rest for a day or two. The hquor is then mixed up with oxide of manganese, and put into a retort, to which heat is applied. The iodine distils over, and is con- densed in receivers fitted to the retort. Iodine is a solid substance, of a metallic lustre, and a bluish black colour ; it stains the hands yellow if touched, and is volatile at a low heat, rising in vapour of a beautiful violet colour. It combines with nearly all the non-metallic elements, and also with the metals ; with many of the latter it forms compounds having beautifiil colours, suitable in every way as 100 BEOMIKE. dyes. But from the volatile nature of iodine, the colours pro- duced by it are fugitive, and do not bear exposure. Many attempts have been made to employ the salts of iodine as dye- drugs, and to fix the colour, but they have all failed. The compounds of iodine v;ith oxygen, are the two acids : Iodic acid lOs. | Hj'periodic acid IO7. These acids combine with bases to form salts termed iodates. It forms an acid with hydrogen, namely: — Hydriodic acid, HI. The salts which this acid forms are termed hydriodates. Iodine combines with starch, and forms a deep blue violet colour, which soon passes away. The principal compound with which experiments upon the colours formed by iodine may be carried on, is the iodide of potassium, KI. This is easUy prepared by boUing iodine in a solution of caustic potash to dryness, then fusing the dry mass in an iron vessel or crucible. The result of this is iodide of potassium, which is easily soluble in water. This salt is abundant, and always very pure in commerce. A httle of the solution added to a salt of lead produces a beautiful yellow precipitate, which when boiled in water, and the clear part set aside to cool, gives brilliant golden-coloured crystals in scales. The salts of mercury give with iodide of potassium a deep orange red precipitate. This salt indeed gives precipitates and colours with the salts of nearly all the metals ; and, were it possible to render the colours it affords permanent, it would no doubt become a most useful drug in the hands of the operative dyer. Bromine (Br 80). Bromine is another element obtained from the ashes of certain sea-weeds, but not in nearly so great abundance as iodine. It is a liquid at ordinary temperatures ; has a deep red colour, and is much heavier than water, in which it is generally kept to prevent it volatilizing as it does rapidly when exposed to the air. It has a very penetrating odour, and its fiimes destroy vegetable colouring matters, leaving merely a yellow tint. Bromine is known to combine with oxygen in only one SILICIUM. 101 proportion = BrO^. This is bromic acid, -which combines with bases, forming the salts termed bromates. With hy- drogen it combines and forms hydrobromic acid = HBr, the salts of which are termed hyckobromates. It also unites du-ectly with some of the other elements forming bromides, of whicb the bromide of potassium is an example. The compounds of bromine with some of the metals might also form a dye were they procured abundantly ; but the same objection to iodine is also applicable to bromine, it is unstable, and vanishes on exposure. Bromine and some of its compounds have been much used in the operations of daguerreotyping. Fluorine (F1 18-9). This element is only known in combination, and has never been obtained free. By its powerful attraction for every other substance, it fultils in some degree the old hypothetical notion of a universal solvent. It is however very abundant in natui-e, combined with calcium as a fluoride, Ibrming the mineral Jluor simr. It is not known to combine with oxygen, but it combines very readily with hydrogen, and forms hydro- fluoric acid = HFl. This acid may be evolved from fluor spar by acting upon it with sulphuric acid. It dissolves glass, and all matters containing silica, and therefore cannot be kept in glass, china, or earthenware vessels ; and as it dissolves all metals except lead, silver, gold, and platinum, it can only be kept in vessels made of any of these metals, but lead bottles are commonly used. By mixing fluor spar and pieces of glass or fine sand, and acting \ipon the mixture by strong sulphuric acid, an acid gas is given off, this is fluosilicic acid = SiFlg, which, together with hydrofluoric acid, combines with water, and is termed hijdrojiuosilicic acid==3riFl-|-2SiFJ3. This solution is occasionally used in the laboratory as a test ibr potash and soda. SiLiciuM (Si 213). Silicium is a light brown powder. It is one of the most extensively diffiised elements in nature, but it always exists in combination with oxygen, forming silica or silicic acid = Si O;,. 102 CARBON. The substances known as flints, agates, quartz, sand, &c., are nearly pure silica, and every other earthy substance in nature contains more or less sihca combined ■with it. This substance is of essential importance to the potter and glass maker, but it is of little consideration in dyeing. Boron (B. ]0-9). Boron is a solid, and generally obtained as a greenish brown powder, destitute of metallic lustre. It is not found in nature except in combination with oxygen, with which it forms boracic acid = BO3. This acid combines with bases forming borates ; but it is found in nature vincombined, especially among the volcanic products of the Lipari islands. The prin- cipal sources of the compounds of boron are, however, some springs in India, and the waters of Sasso, which hold in solu- tion a quantity of borate of soda (borax). In some lakes in the neighbourhood of volcanoes there are also great quantities of boracic acid. These waters are concentrated by evaporation sufficiently to allow the acid to crystallize, and in this state it is known in commerce as raw borax. Arrived in this country it is dissolved and saturated with soda to form borate of soda, which is obtained in large crystals ; this is the refined borax of commerce, and the principal compound of boron known in the arts. It is much used in medicine and as a flux in the operations of metallurgy. Carbon (C 6). Carbon is very extensively diffused through nature, and the complete description of this element and its compounds would embrace the whole chemistry of organic matter. It is met with also in various forms and combinations in the mineral kingdom. Carbon exists pure in diamond and coal, and forms nearly the whole of plumbago and graphite (popularly black lead). It may be obtained by submitting either animal or vegetable matter to a high heat in a close vessel : the oxygen, hydrogen, and nitrogen of these bodies pass off, and the carbon is left. Charcoal is therefore carbon with a little earthy matter; and coke, ivory black, and lamp black, are other familiar names for it in an impure state. These substances CARBON. 1 03 differ in character from each other in having different pro- portions of earthy ingredients in combination or mixture with the principal element. Carbon is infusible, therefore we only know it in a solid form. It possesses many singular pro- perties connected with the principles of dyeing ; some of these we will state here and reserve the appUcations till we come tc> consider the methods and theory of dyeing. Carbon has the property of absorbing gases within its pores. One cubic inch of the best charcoal made from boxwood has been found to absorb or imbibe the following quantities of the different gases named : — Cubic inches. 90 Ammoniacal gas. 85 Hydrochloric acid gas. 65 Sulphiu-ous acid. 55 Sulphuretted liydi-ogen. 40 Peroxide of nitrogen. 35 Carbonic acid. 9 Oxygen. 7 Nitrogen. 1.7 Ilydi'ogen. Thi,s curious property is not well understood ; it is generally supposed that it results from the powerful cohesive attraction between the gas and the surface of the charcoal by which the gas is liquified. Somewhat analogous to this property is its power of absorbing or imbibing colouring matters, and on this account it is extensively used for discolom-ing sugar ; charcoal has also the property of keeping water sweet for a long time. The various kinds of charcoal possess this discoloiu'ing power differently, probably depending on their state of purity. Supposing that the substance to be discoloured is sulphate of indigo, the following are the powers of some kinds of charcoal compared with that of charcoal from bones, which we call 1. Lamp black r=: 4 Charcoal from starch, ignited with potash = 12 Lamp black, ignited with carbonate of potash .. = 1G Ivory black, ignited with carbonate of potash ..=45 Blood charcoal, ignited with carbonate of potash =50 This property of absorbing colours is also considered an attraction of surface, and it is found in some cases to be 104 CARBONIC ACID. sufficiently strong to overcome chemical affinity. The same property of imbibing colours is possessed by other porous matters to some extent, and the porous nature of the fibre of cotton, woollen, and silk, may exercise an influence of a similar kind, a subject which we intend to consider further on. Carbon combines with oxygen in three proportions, forming: Carbonic oxide CO. Carbonic acid CO^. Oxalic acid C2, O3. Carbonic Oxide is obtained by heating together strong vitriol and crystallized oxalic acid. This operation may be performed in a retort or flask, as described for hydrogen (page 38) ; the action taking place is — Carbon. Carbon . Oxygen. Oxygen. Oxygen. Water..., Crystallized oxalic acid. Oxide of carbon. Carbonic acid. Strong sul- phuric acid. Sulphuric acid Sulphuric acid- The action is simply the siilphuric acid taking the water from the crystallized oxalic acid and setting the elements free. By passing the gases through a solution of caustic potash or lime water, the carbonic acid is absorbed, and carbonic oxide is obtained pure. It is a colourless gas, inodorous, and burns with a blue flame. It is the presence of this gas which gives the blue flame of a coke fire. The product of its combustion is carbonic acid. Carbonic Acid.— When carbon is brought to a red heat, it burns and dissipates ; the oxygen combines with the carbon, and produces gaseous carbonic acid. This gas is generally obtained for experiment from its compounds. Thus, when a few pieces of marble or elialk are put into a flask or retort, and some dilute muriatic acid is added, effervescence takes place, and the action is — rCarbonic acid, -Carbonic acid. Marble.... -(Calcium. (Oxygen, Muriatic /Hydrogen ^^^^^^=7=- Water. acid \Chlorine ^ Chloride calcium. OXALIC ACID. 105 Caibc'iuc acid is absorbed by water, in quantity equal to the volume of the gas; but tlie materials from which it is prepared are so cheap, that this absorption does not signify much in an experiment. The gas is colourless, and heavier than atmosiihcric air, so that it may be poiu'ed from one vessel to another as if it were a liquid. A light is instantly extinguished by immersion in an atmosphere of it, and an animal soon dies if kept in air containing nine per cent of it. Combined Avith water, it manifests acid properties, and gives the water an agreeable taste and pungency, as experienced in aerated waters. It combines readily with alkaline and earthy bases, producing carbonates. Its affinity for lime is very great ; but it is liberated from all its compounds with effervescence by a stronger acid. When the dry gas is passed over redhot charcoal, it is decomposed ; the charcoal combines with half its oxygen, and forms oxide of carbon. Oxalic Acid has been long known in commerce as salt of so)TeL It was formerly obtained from the a'olis acetese/la, a plant which contains it as oxalate of lime ; but it is now manufactured in large quantities from sugar and starch, by acting upon these substances with nitric acid, which oxidates and decomposes them. The action is probably as follows : — 6 Proportions of ( G Binoxide of nitrogen given off. nitric acid. ^18 Oxygen.. r^ Oxalic acid. o (12 Carbon -- — ^ bugar, 1 1 A TT 1 ° \ r -N 1 Hydron;en — composed 01... jmri ~~~~-~-- itt 4. ^ (10 Oxygen... =- Water. The acid crystallizes with water, which, as has been shown above, is essential to its existence. It combines with bases, and forms salts of great importance in the laboratory. Thus the oxalates of potash and ammonia are excellent tests for lime ; and they are also of some importance in the dyehouse, as are also the oxalates of tin, &c. Oxalic acid is easily distinguished from any of the alkaline and earthy salts such as the sulphate of magnesia (epsom salts), for which it has occasionally, through ignorance, been mistaken by its strong acid cliaracter. It is easily detected by heating it to redness upon a piece of platinum, when it will all evapo- rate, and leave no residue, while the magnesian salt does. It sometimes contains nitric acid, peroxide of nitrogen, f2 106 CrAXOGEN. and epsom salts ; the two first may be detected by dissolving a little of the acid, and adding a minute colouring of sulphate of indigo, and then boiUng : the presence of these impurities decolours the indigo. The presence of epsom salts may be detected by chloride of barium, or by evaporation as directed above. There is often about one per cent, of this salt in the commercial oxalic acid. This acid has been long used in the dyehouse, and acts powerfully upon many substances, but it is not now so generally used. A carious salt, of a beautiful colour, may be obtained by taking One part of bichromate of potash, Two of binosalate of potash. Two of oxalic acid ; and dissolve the whole together in hot water, when carbonic acid is evolved, and a double salt of oxalate of potash and chrome, having a fine purple colour, is formed in solution. Crystals of the salt, possessing a very deep blue colour, may be obtained by evaporation. cyanogen.— Carbon combines with nitrogen, and forms cyano- gen, a very important compound, consisting of one equivalent of nitrogen, and two equivalents of carbon = C2N. It is a gas, and has the property of combining ^nth other elements as if it were itself an element. It belongs, therefore, as was stated at p. 33, to the class of compounds known as salt radicals. It is not obtained by directly bringing nitrogen into contact with carbon, but by the decomposition of animal compounds in contact with metallic bases, as we will have occasion to describe further on. The gas is generally obtained for experiment from its salts, by heating cyanide of mercury in a retort. The mercury runs over in a metallic state, and the cyanogen escapes as gas, and may be caught at the pneumatic trough. Cyanogen combines with oxygen, and forms an acid called cyanic acid, and this combining with bases, terms cyanates. Cyanogen combines also with hydrogen, and fonns an acid termed hydrocyanic acid, or more commonly prussic acid, which, like hydrochloric acid, does not combine with bases, as CNj+H, and although certain salts are termed prussiates. MELLON. 107 they are properly cyanides. Some of them are highly import- ant' in the arts, and will be noticed in their proper places. Cyanogen also combines with the metals in the same manner as chlorine and iodine, and forms that class of salts termed cyanides* jflelloa.-Carbon combines with nitrogen in other proportions besides that of cyanogen. There is one expressed by N^Cg, which is a soUd substance of a lemon yellow colour, insoluble in water, but which acts the part of a salt radical, and com- bines with hydrogen to form an acid which also combines with several of the metaUic bases. This salt radical is termed Mellon, and the salts from it are termed mellonides ; but these compounds are not so well known as the cyanides, and they are less useful. Carbon combines with hydrogen in various proportions, forming dififereut kinds of gases, such as light carburetted hydrogen = CHo; olefiant gas = C^Hi ; common coal gas, and some other hydrocarbons consist of those gases as constituents. Carbon also combines with sulphur, and forms with it a colour- less, volatile, and inflammable liquid, possessing a most putrid smell : this is sulphuret of carbon. In organic bodies, car- bon is combined with oxygen, hydrogen, and nitrogen, in an endless variety of proportions. Some of these compounds will be brought under notice when treating of the organic substances which fall within the scope of our subject. * The distinction between the names ending in ate and vJe must here be borne in mind. METALLIC SUBSTANCES. General Properties of Metals. We now proceed to consider that division of the elements commonly known as metals. To define the peculiar properties of a metal is somewhat difficult, for whichever property we select, it is either absent in some metal, or it is possessed by some non-metallic element. A few of the more prominent physical properties may, however, be named. ]st, They all possess a peculiar lustre. 2d, They all reflect light, which is the cause of that lustre. 3d, They are all fusible by heat, and while in fusion retain their lustre. 4th, They are all conductors of light and heat. 5th, They have all to a certain degree the property of extension ; they are malleable under the hammer ; and laminahle under the roller ; and being capable of extension by drawing into wire, they are termed ductile. There are also chemical distinctions which are much more universal. They are all basic, that is to say, capable of com- bining with oxygen, and forming oxides ; and with acids they form a series of compounds termed salts, of which the metal is termed the hose. It is on account of the possession of these general properties that hydrogen is regarded as a metal in a gaseous state : it is pre-eminently basic. "When metals combine with one another the compound is termed an alloy. Brass is a chemical mixture of copper and zinc ; and German silver is a like mixture of copper, zinc, and nickel ; both brass and German silver are therefore alloys. Alloys retain most of the physical properties of the metals of which they consist. A great many of the recently discovered metals are very rare, and have only been found in certain localities, and in minute quantities. The alkalis and earths were long looked upon as elements ; they had never indeed POTASSIUM. 109 been decomposed till 1807. What was until that time known as the element Potash, we now know to be the oxide of the metal Potassium. Soda, Sodium. Lithia, Lithium. Lime, Calcium. Bary tes, Barium. Magnesia, Magnesium. Alumina (pure clay), Aluminum. Potassium (K 39-2). Sir H. Davy decomposed potash by a powerful electric current, and demonstrated it to be the oxide of a peculiar metal which he termed potassium. This metal may be obtained easily by roasting a quantity of bitartrate of potash (cream of tartar) in a covered crucible : tlie immediate product is what is termed Mack flux ; then mi.xing this matter with a quantity of finely ground charcoal, and putting the whole into a wrought iron bottle, and distilling it at a high heat, the metal comes over, and is caught in a vessel contahiing naphtha, a fluid that contains no oxygen. Only such a Huid can be used for this purpose, as the attraction of potassium for oxygen is so great, that it decomposes all substances which contain that element. Potassium is a white metal, with a lustre somewhat like silver ; at ordinary temperatures it is soft, and may be flattened between the fingers, but at 32*^ it is hard and brittle. It melts at 136°. When exposed to the air it becomes covered immediately with a white crust of oxide. It is lighter than water, and when thrown upon that fluid it swims, and instantly bursts into flame, combining with the oxygen of the water so rapidly, as to produce heat suiUcicnt to kindle the hydro- gen as it makes its escape. The metal not only fuses, but a small portion of it goes off as vapour, and burning with tlie hydrogen produces a beautiful red-coloured flame. In this experiment potash is formed in the water. Pure potash is the oxide of the metal potassium, but it is not prepared from the metal for manufacturing purposes. 110 POTASH. Potash —Sometimes termed the vegetable alkali, takes its name from being prepared for commercial pui'poses in iron pots. When a piece of wood, or other vegetable substance is slowly burned until all inflammable matters are consumed, there is left a white substance called ash. This ash consists of the mineral ingredients of the vegetables, along with potash, lime, and other earthy ingredients. The potash and other soluble ingredients are extracted by treating the ash with water. The average quantity of ash obtained from wood is about one per cent. In America, where wood is an incumbrance, it is felled, pUed up in masses, and burned for the manufacture of potash. The ashes of the wood are collected and put into cisterns provided with false bottoms, and run-off plugs under- neath. A quantity of water is thrown upon the ashes in a cistern, and after stu'ring and settUng a few hours, all the soluble matters are dissolved, and the liquor is drawn off, evaporated to dryness, and the residue afterwai'ds fused at a red heat into compact masses, and in this state constitutes the commercial hlach 'ash. As other matters besides the potash are soluble in water, the black ash thus prepared contains these substances as impurities. These are mainly sulphites, sulphurets, and chlorides of potash, along with some earthy matters. Pearl ash is prepared by calcining the black ash in a reverberatory furnace imtil all the carbonaceous matters and the sulphur are driven off". The remaining mass is then dissolved in water, and the solution evaporated to dryness in large iron pans. Towards the conclusion of the process the mass is stirred to give it a lumpy granulation. This ash contains much less extraneous matter than black ash, and is consequently weaker as an allvali. It is more fully carbonated. Dr. Ure states (Dictionary of Arts, &c.) that he found the best pink coloured Canadian potash to contain GO per cent, of real potash, while the best pearl ash contained only 50 per cent. These are the two states in which potash is introduced into the dyehouse. The methods for testing the quantity of real alkali they contain will be given when we come to speak of soda. The principal use of potash is to destroy or take off any grease or oil which may exist in or upon the fibre to be dyed, and it does this by combining with these substances and form- POTASH. Ill ing soap, which, being soluble in water, is easily removed. Dyers are often in the habit, when about to steep or boil their goods, of simply adding to their solution or boiler, some pearl ash or potash, but as the alkali is in union with an acid (carbonic acid) forming a carbonate, its power of combining with oil or grease is to a great extent neutralized. The white obtained upon the fabric may be good enough, and as was before remarked when speaking of chlorine, a good white can be got without potash ; but it is not so permanent. If grease or oil be present they are not removed, but only concealed, and the dyer is often annoyed by large resist spots which he cannot account for, and which are not so easily removed after the goods are boiled as before. The alkali, whether pearl or potash, before being used ought to be made caustic, that is, deprived of its carbonic acid, and converted into oxide of potassium. This is done by boiling the carbonated alkali with newly slaked lime ; the lime combines with the carbonic acid of the alkali, and fidls to the bottom, while the caustic alkali remains in solution. Without detailing the various methods practised, some of which are not good, we shall rather give what we consider the best. The carbonate of potash ought to be dissolved in not less water than six tunes its weight ; it is better, however, to use ten times its weight, as if a less quantity of water be used, the potash is not deprived of all its carbonic acid. The reason assigned for this singular phenomenon is, that both caustic potash and its carbonate have a strong affinity for water, and when less than six times its weight is used, there is sutticieut water to supply the carbonate, but not the caustic alkali, and hence the carbonate is not converted into the caustic state. The exact quantity of lime is not material, provided there be enough. The lime ought to be added when the alkali is boiling, and from time to time, until, a little of the solution being taken out, it does not effervesce by the addition of a Uttle dilute sulphmic acid. If strong acid is used, care must be taken before adding it that the solution be cold, for if not, it will spurt, and may injure the maripulator. The best way is to take a little of the alkali and dilute it with cold water, and then add the acid. When there is no effervescence, the alkali is caustic. The boiling is then stopped, and when the lime settles the clear is taken off and kept in an iron vessel covered closely, 112 POTASH. as the potash readily takes up carbonic acid from the air. For bleaching, and other cleansing operations, and also for many purposes in the dyehouse, the supply should be taken from this stock vessel. It will be necessary, however, that the operator know the exact strength of the solution, in order that he may know the proper quantities of it he ought to use for particular purposes. On this point a pretty correct approximation is obtained by knowing the per centage of pearl or potash used in making the solution, and then calcu- lating the quantity to each gallon : but greater exactness is attained by using the following table, (drawn up by Dr. Dalton,) in Avhich the specific gravity is supposed to be known, and hence the quantity present of the alkali in solution: — Potasli, iier cent, in ;io!ution. Specific pravity of solution. Specific gr.-xvity by Twaddull's. Boiling^ poirit of solution. 72-4 2-ooa 200° 600° 63-6 1-880 176 420 56-8 1-780 156 360 51-2 1-680 136 320 46-7 1-GOO 120 290 42-9 1-520 105 276 39-6 1-470 94 265 36-8 1-440 88 255 34-4 1-420 84 246 32-4 1-390 78 240 29-4 1-3 GO 72 234 26-3 1-330 66 229 23-4 1-280 56 224 19-5 1-230 46 220 16-2 1-190 38 218 13- 1-150 30 215 9o 1-110 20 214 4-7 1 -060 12 213 In the first column of this table the percentage of alkali is given by weight. Thus a gallon of water is lOlbs. weight, therefore a gallon of the caustic ley solution will have one- tenth part of the potash indicated by the table according to the specific gravity. Say the solution stands 30° l)y Twaddell, — the percentage of this is 13, and this divided by 10 gives 1"3 POTASH. 113 lb. = lib. 5oz. nearly of caustic potash to a gallon of the k^y. The stock ley should not be made stronger than tliis. In the last column the boiling points of the solution at different strengths are entered. These numbers are impor- tant, and explain to some extent why boiling by steam is not so effective as by fire ; for the steam heat, as was stated at page 7, is not higher than 210", whereas the lowest tempera- ture noted in the table is 213°. Potash, as used in the dyehouse, is never chemically pure. Even when used as caustic, it generally contains lime and soda, and often their sulphurets. Lime may be detected by adding a little clear solution of carbonate of potash to a clear solution of the caustic potash, when its presence will be known by the milkiness produced. It is not, however, detrimental to the dyer in the operations in which potash is commonly used. Sulphurets may be detected by adding to a dilute solution of the potash some acetate of lead ; if a sulphuret is present, there will be a blackish precipitate. Sulphvu'ets are destructive to gold ornaments on muslin and other cloths, for the metal is rarely pure ; commonly it is an alloy of gold with copper, &c., and sometimes the inferior metal is merely gilt. The sulphuret acts upon all the inferior metals by contact, and at least blackens them. Potash containing sulphurets should therefore be avoided for goods having such ornaments. Caustic potash is evaporated to dryness, fused, and poured into moulds to form it into small cyhnders ; in this state it is sold by druggists under the name of stick-potash. Potash has a strong affinity for water, and deliquesces rapidly when exposed to the air ; this property is also pos- sessed by the carbonates. The following table gives the average quantity of pure alkali, &c., in the different sorts of commercial potash : — 1 , , , MuriKte Insoluble 1 Name of Place from which It Re.ll Sulphate of of TOIiL. is procured. 'Potasli i Potash. Potash. Water. cnt3. 1 Potash of Russia, . 772 65 5 254 56 1152 1 — America, . ■857 154 20 119 2 1152 American Pearl,.. :754 80 4 308 6 1152 Potash of Treves, . !720 165 44 199 24 1152 — Dantzic, . . . '■ fi03 152 14 304 79 1152 — Vosges, .... 444 1 148 510 304 1 34 1440 "*114 SALTS OF POTASH. Potassium combines with chlorine, and forms chloride of potassium — more commonly termed muriate of potash : which may be prepared by adding hydrochloric acid to caustic potash, or its cai'bonate. It combines also with iodine, and forms iodide of potassium (page 100); with bromine it forms bromide of potassium ; and with sulphur it forms the sul- phuret, or sulphide of potassium. We have already noticed most of these salts. Sulphate of Potash.— When sulphuric acid is added to potash it forms a salt which has neither acid nor alkaline properties, and which is easily crystallised. 'Jliis neutral salt is produced abundantly in the manufacture of nitric acid from nitre. It is not deliquescent, and requires 15 times its own weight of Avater to dissolve it. Bisniphatc of Potash.— This Salt is also obtained like the sulphate in the process of making nitric acid from nitre ; but it may be prepared by adding to the sulphate half its weight of sulphuric acid, and bringing the mixture up to a red heat in. if. porcelain or platinum vessel. This salt has strong acid reactions, is very soluble in water, melts easily with heat, and is exceedingly useful for dissolving metals, many of which may be dissolved by it easily, although of very difficult solu- tion in the pure acid. Sulphite of Potash is prepared by passing a current of sulphuroiis acid gas through a solution of carbonate of potash tiU saturated. It crystaUises, and should be kept close, as it rapidly passes to tlie state of sulphate by exposure to the air. Nitrate of Potn»>h may be prepared by saturating potash with nitric acid ; but it is obtained abundantly in native beds (page 52). It is prepared artificially in Germany and France, by forming large beds of animal and vegetable refuse, in which decomposition is effected by putrefaction. Potash is present in the organic matter, and these also yield nitrogen and oxygen to form nitric acid; and by combination the nitrate of potash is formed. The chief uses of nitrate of potash are in the manufacture of gunpowder and nitric acid. Chloi-ate of Potash is prepared by passing chlorine gas through carbonate of potash. When the solution is saturated, crystals of this salt are formed (page Gl). This salt, as already stated, is advantageously used in several operations in 'the dyehouse, in which oxidation is required; also with FERROCTANIDE OF POTASSIUM. 115 decoctions of some of the woods. When mixed with sub- stances containing carbon, it gives them great combustibihty. Thus, if a drop of sulphuric acid is added to a mixture of chlorate of potash and sugar, combustion instantly commences, and the mixture burns with great rapidity. Phosphate of Potash. — This salt is obtained by adding car- bonate of potash to a hot solution of phosphoric acid, until the solution ceases to redden blue litmus paper. By careful evaporation, the salt may be crystallized. If the carbonate of potash be added to the phosphoric acid while cold, in sufficient quantity to saturate it, the solution, by evaporation, gives crystals of a salt having two propor- tions of acid — a biphosphate of potash. Oxalate of Potash. — This Salt is obtained by saturating carbonate of potash with oxalic acid, and crystallizing. In this state it contains one proportion of water. The Binoxalatc is obtained from wood sorrel, in which it exists ready formed. It is obtained by reducing the expressed juice of the sorrel to the consistence of a syrup, and setting it aside to crystallize. It is sold as salt (f sorrel and essential salt of lemons. The taste of the salt is acid ; it is employed for removing ink stains from goods and recently formed iron moulds. Its crystals are composed of 2 acid, 1 potash, and 2 water. Fcrrpcyanide of Potassinm. — This salt is known as yeUow prussiate of potash. "VVe have already referred to the com- pound salt radical termed cyanogen, and stated that it com- bines with other bodies, and forms salts resembling the chlorides ; but it is occasionally found that two such salts group together and form a distinct compound. Thus, one proportion of the protocyanide of iron ^= Fe, Cy, combines with two proportions of cyanide of potassium, = 2Cy K, and forms the fcrrocyankle of ])otassmjn. These two proportions of potassium may be replaced by another metal, but the iron and the three equivalents of cyanogen maintain themselves together. It has, therefore, been inferred, that Fe Cys is a distinct salt radical, which may be termed fe/TO prussic acid ; a theoretical deduction very interesting to study, and wOiich will be more fully developed as we proceed. The salts formed by this acid are distinguished by the prefix yerro. The ferrocyanide of potassium, or prussiate of potash, is pre- 116 FERROCTAMDE OF POTASSIUM. pared on the large scale by calcining together dried blood, hoofs, horns, hides, old woollen rags, or similar materials, with carbo- nate of potash, in an iron vessel : commonly those substances are partially carbonized or burned in large cast-iron cylinders previously to being mixed with the potash. If the animal matters are used without being subjected to this preliminary process, they are mixed in the ratio of about 8 to 1 of pearl ash ; but if burned previously, one and a half of the charcoal is mixed with one of pearl ash. When the animal matters are used without being charred, the calcining pot is left open to allow the materials to be stirred and the noxious vapours to escape ; after which the vessel is closed, and the heat is increased. This is continued for some time, and at intervals of half an hour, the mouth of the vessel is uncovered for the purpose of stirring the matter within. This process is con- tinued until the flame ceases to rise from the surface, and the materials are reduced to a red semifluid mass, which generally takes place in about eight hours after the pot is closed. From this description, the nature of the action is easily luiderstood. The animal matters which contain nitrogen and carbon abun- dantly, are decomposed by the heat ; but, on account of the presence of the iron and potash, definite portions of the elements combine and form cyanogen, which is simultaneous]}' taken up by the potassium and Iron, and we have two proportions of cyanide of potassium, with one proportion of cyanide of iron. The molten mass is scooped out with iron ladles, and allowed to cool. When the mass has cooled, it is dissolved in cold water, and the solution is filtered tlirough cloth. Lest any cyanide of potassium should remain which had not received the proportion of iron, sulphate of iron (copperas) is added by degrees to the solution, so long as the prussian blue which is at first formed on adding the iron salt is redissolved. The whole is then evaporated to a proper consistency ; after which, pieces of coarse cord are suspended throughout the liquid, upon which crystals of ferro-prussiate are foimed in regular bunches, of a beautiful light citron yellow. Ferrocyanide of potassium crystallizes with three pro- portions of water, which it loses at 212°. It dissolves in 4 parts of cold and 2 parts cf boiling water. From this salt all other ferrocyanides are derived as precipitates ; those of the metals are formed by adding a salt of the metal to a solution FERROCYANIDE OF POTASSIUM. 117 of the prussiate. The following are the appearances of a few of those precipitates, corresponding to the metals employed : — Protoxide of Manganese... White, turning to a deep red. Peroxide of Manganese. ..Greenish grey. — Lead White, with a yellowish hue. Peroxide of Iron Deep blue. Protoxide of Iron White, turning blue by exposure. — Copper Brown. — Zinc White. Protoxide of Tin White. Peroxide of Tin Yellow. Each of these precipitates is a ferrocyanide of the metal used, which has taken the place of the potassium ; they are all insoluble in water, and where a colour can be obtained by them, they are suitable for a dye, although the colours dyed by the yellow prussiate are fugitive. Every alkaline sub- stance, such as soap, destroys them, and they are easily affected by that universal creator and destroyer of colours, the sun. The principal use of the ferrocyanide salt in the dye-house is for dyeing Prussian blue. To dye this colour, the goods are impregnated with a persalt of iron, and then passed through a solution of yellow prussiate of potash ; but this mode is objectionable for light shades and light goods, as it causes much loss of the Prussian salt. The general method of dyeing light Prussian blues upon cloths is, to put a little nitrate of iron into a vessel full of water ; the cloth is wrought in this for about ten or fifteen minutes, and then Avashed through two or thi-ee tubs full of clean water, to take off all the superfluous acid and iron. Whether the cause of the reception of the dye be an attraction of the material of the cloth for the iron, or the simple power of absorption of the fibres, we shall not stay to examine here ; but although the nitrate of iron is an exceedingly soluble salt, a portion of the peroxide of iron remains fixed in the fibres, having abandoned its acid, and this no washing will remove. The cloth, being well washed from the acid, is put into the prussiate. A small quantity of acid must be added to the ferrocyanide of potas- sium solution, to take up the potassium, and to set the ferro- cyanogen at liberty, to unite with the iron upon the cloth. 118 PBUSSIAX BLUE. this forms ferrocyanide of iron or Prussian blue, and consti- tutes the dye. Considerable care ought to be taken in adding acid to the prussiate, otherwise the colour is liable to change, becoming grey or reddish when dried. The following mode of adding sulphuric acid to the prus- siate, when a considerable quantity of goods are to be dyed at once, is commonly practised. What is considered the proper quantity of yellow prussiate of potash is dissolved in just as much boiling water as is necessary for solution. To this solution a quantity of sulphuric acid is added, sufficient to make it strongly acid ; and the mixture thus prepared is added to the j^'^^^^siate tub as required. This method of add- ing the sulphuric acid is exceedingly objectionable, as it causes the evolution of prussic acid, which may be detected by the pungent smell it excites ; and in proportion to the escape of that gas, there is a loss of the dyeing power of the prussiate. If three parts of acid be added to seven of yellow prussiate, the loss would amount to one-half, and the remaining half would be so changed in its properties as to produce only a bad blue. Thus the dyer must use an additional quantity of prussiate, and after all he produces but an indifferent colour. The proper method of using the acid is to dissolve the prus- siate in hot water, and to add the necessary quantity of this solution to the water-tub in which the goods are to be dyed. Previously to putting in the cloth, a few drops of sulphuric acid are added, just sufficient to be perceptible to the taste ; or, what is a much better test, sufficient to redden blue litmus paper. The goods being wrought for some time in this mix- ture, they are washed in clean water, having a small quantity of alum in solution. For light shades of sky-blue, they should not be dried from the alum solution, as there is a great ten- dency to assume a lavender hue. A better plan is to employ two tubs of water, the one being touched with alum, and the other pure, for washing from it. Cloths dyed by the prussiate should be exposed to a very dry atmosphere when hung up to be dried. Deep blue is dyed by passing the goods through strong nitrate of iron, then through potash ley, which fixes the oxide of iron upon the cloth, and then through the prussiate. Royal blue is dyed by adding protochloride of tin {salts of tin) to the nitrate of iron ; entering the goods immediately, FERRICYANIDE OF POTASSIUM. 119 and passing them from the u'on through the prussiate without washing. This method gives a rich deep blue, and is now much practised. Some of the peculiarities of the process will hereafter be described ; meantime, it will be sufficient to observe, that a peculiar purple bloom is given, by using hydrochloric acid in the prussiate solution instead of sul- phuric acid. Ferricj-nuide of Potassium. — This is the red prussiate of potash. If a current of chlorine gas be passed through a strong solution of yellow prussiate of potash, till the solu- tion changes to a reddish colour, and when a drop of it added to nitrate of iron gives no precipitate, there is formed chloride of potassium, and a salt differing materially from yellow prussiate. The solution being evaporated, this salt is obtained in beautiful ruby-red crystals, termed, from their colour, red prussiate of potash. They are anhydrous, soluble in 4 parts of cold and a less quantity of hot Avater. The red prussiate is well adapted for many operations in dyeing, but it is too expensive for general use. It yields the following colours with the salts of the different metals undernamed : — Bismuth Pale yellow. Cadmium Yellow. Cobalt Dark-brown red. Copper Yellowish-green. Protosalts of iron Deep blue. Persalts of iron No precipitate. Manganese Brown. Mercury Red-brown. Nickel Yellow-green. Tin While. Zinc Orange-yellow. It will be observed from this table, that the salts of iron, which yield a blue with yellow prussiate of potash, give no colour with the red prussiate ; and the protosalts of iron, which give only a grey with yellow prussiate, yield a deep blue with red prussiate. The true constitution of this salt, or rather the arrangement in which these elements unite, is still subject of hypothesis. We have seen, in regard to the ferrocyanide, that the iron exists as a protocyanide, with two cyanides of another metal ; X 120 SODIUM. but in the ferriq/anide we have iron as a percjanide, with cyanides of other metals. Thus — Ferrocjanide Fe Cy -j- 2 Cy K = Protocyanide. Ferricyanide Fco Cyg-j- 3 Cy K = Percyanide. Those who suppose that the compound Fe Cys of the yellow prussiate forms the salt radical of all the ferrocyanides, sup- pose also that the red prussiate has Fe, Cyc, consisting of the same number of elements combined together in double pro- portions, corresponding to the pro and per oxides of iron. But whatever may be the true relation in which the elements are united, the two salts are distinct in their reactions, and we would suggest to the dyer to give particular attention to the difference of the salts, with reference to salts of iron, as they are important, and will be referred to hereafter. Cyanide of Potassinm.— If yellow prussiate be dried at a heat of about 220"' to 300", and 8 parts of this dried salt be mixed with 3 parts of dry carbonate of potash and the mixture put into a crucible, and fused until effervescence ceases, then re- moved from the fire, and allowed to settle for a few .minutes: by pouring off the clear into an iron vessel, it solidifies into a white crystalline mass which is cyanide of potassium = Cy El. This salt has a strong alkaline reaction, and is peculiar for its power of dissolving metals and giving precipitates which might be advantageously applied to some of the operations of dyeing. Cranate of Potash.— This Salt is prepared in the same way as the last, but with the addition of some oxide of manganese, or other oxide, which converts the cyanogen into cyanic acid, and forms cyanate of potash = Cy O, KO. The cyanates of the alkalis are all soluble in water, and in this they differ from the cyanates of the other metals. Sodium (Na 23.) Soda was not distinguished from potash till near the middle of the eighteenth century, when their distinctive characters were recognised. The potash was termed the vegetable, and the soda the mineral alkali. In 1807, Sir H. Davy demon- strated that soda, like potash, is the oxide of a metal which he named sodium. It is a white metal, having much the ap- SODA. 121 pearance of silver, but is sufficiently soft to yield to the pres- sure of the fingers, and to be cut by the nail. It oxidates spontaneously in the air, but not so rapidly as potassium. When a small piece is thrown upon water, it floats ; the heat, generated by combining with the oxygen of the water, melts it, and it forms a silvery globe, which gyrates rapidly on the surface of the water ; but it does not inflame the hydrogen unless it be kept stationary, and then an explo- sion takes place. If, however, the temperature of the water is as high as 110° Fah., the hydrogen burns as it is evolved, with a bright flame. In these experiments oxide of sodium is formed and dissolved in the water, which thus becomes a solution of caustic soda. Sodium is a very abundant element in nature, but is always found in combination, e. g,, as nitrate of soda, and chloride of sodium (common salt). This last is the great source of soda for manufacturing purposes ; and since the process of making soda from it was discovered, this alkali, owing to its cheapness, has been used instead of potash in almost all the processes of the arts that admit of the substitution. Soda, as sold to dyers and bleachers, is in the state of a dry white powder, or granular substance, termed soda- ash, which is an impure carbonate prepared as follows: — A quantity of about 600 lbs. of common salt is put upon the bottom of a reverberatory furnace, previously heated ; upon this is let do^vn, from an apparatus on the roof of the furnace, a quantity of sulphui'ic acid, of the specific gravity 1*600; and the salt is decomposed. The result is as follows : — Common salt ... IS ^^- %drochloric acid. Sulphuric acid \c,^' ^""^-^^ ci i i . ^ ^ '^ (ii^i ^^ Sulphate of soda The hydrochloric acid passes ofi" with the steam occasioned by the dilute sulphuric acid. This operation, during which the materials require to be stirred occasionally, lasts about four hours : the charge is then withdrawn from the furnace. The sulphate of soda thus prepared, is reduced to powder, and mixed with an equal weight of ground chalk, and half its weight of coal, well ground and sifted. This mixtiu-e is intro- duced into a very hot reverberatory furnace, about two hun- dred weight at a time, and is frequently stirred until it is G ,122 SODA. uniformly heated. In about an hour it fuses ; it is then well stirred for about five minutes, and drawn out with a rake into a cast iron trough in which it is allowed to cool and solidify. This is called ball soda, or British barilla, and contains about 22 per cent, of alkali. To separate the salts from insoluble matter, the cake of ball soda when cold, is broken up, put into vats, and covered by warm water. In six hours the so- lution is drawn off from below, and the washing repeated about eight times, to extract all the soluble matter. These liquors being mixed together, are boiled doAvn to dryness, and afford a salt which is principally carbonate of soda, with a little caustic soda and sulphuret of sodium. For the purpose of getting rid of the sulphur, the salt is now mixed with one- fourth of its bulk of sawdust, and exposed to a low red heat in another reverberatory furnace for about four hours, which converts the caustic soda into carbonate, while the sulphur is carried off. This product, if the process is well con- ducted, contains about 50 per cent of alkali, and forms the soda-ash of the best quaUty. When it is to be converted into crystallized carbonate of soda, it is dissolved in water, allowed to settle, and the clear liquid boUed down imtil a pellicle appears on its surface. The solution is then run into shallow boxes of cast iron to crystallize in a cool place, and after standing lor a week, the mother hquor is drawn off, and the crystals dramed and broken up for the market. This mother liquor is evaporated to dryness, and yields a very impure soda-ash, containing about 30 per cent, of alkali, which is often em- ployed for making soap. The common crystallized carbonate of soda of the shops is very pure, but is crystallized with 10 equivalents of water. "NVlien exposed to the air, these crystals lose a portion of their water, and assume a chalky white appearance ; if they are subjected to heat, they melt in their water of crystallization. We have known these crystals used for the operations of bleaching merely dissolved ; but they are neither good nor profitable used in this way. They contain in 100 parts by weight Caustic soda, 21 'SI Carbonic acid, 15*43 Water, 6276 100-00 SODA-ASH. 123 Thus fjxlly more than three -fifths of their weight is water. The dry carbonate of soda of the shops, so much used for ^1omestic purposes, is the same as the crystalUzed soda de- prived of its water of crystalhzation. Soda-Ash.— Owing to various circumstances attending the manufacture of this salt, its per centage is very uncertain, varying from 40 to 50 per cent., and it is, therefore, generally priced according to its per centage. The per centage may be determined by some such means as we have described for bleaching powder, that is, by having an acid exactly of the strength at which 100 measures of it will saturate 100 grains, of caustic soda. To form the test acid, according to Professor Graham's du-ections, 4 ounces avoirdupois of oil of vitriol are diluted with 20 ounces of water, or larger portions of acid and water may be mixed in these proportions. About three-fourths of an ounce of bicarbonate of soda is heated strongly by a lamp for a few minutes to obtain pure carbonate of soda, (or what will do, take some crystals of soda and dry in a basin until all water is given ofi"; when boiling has ceased, make the heat to about a dull red, this will give the soda salt,) of which 171 grains are immediately weighed, that quantity containing 100 grains of soda ; this portion of cai'bonate of soda is dissolved in 4 or 5 ounces of hot water, and the alkalimeter is filled up to the highest graduation with the dilute acid. The acid is poured gradually into the soda solution till the action of the latter upon blue litmus test-paper ceases to be alkaline and becomes distinctly acid, and the measures of acid necessary to produce that change are accurately observed ; say it re- quires 90 measures. A plain cylindrical jar, of which the capacity is about a pint and a half, is graduated into 100 parts, each containing 100 grain measures of water, or ten times as much as the di\asions of the alkahmeter. This jar is filled up with the dilute acid to the extent of 90, or whatever number of the alkalimeter divisions of acid were found to neutralize 100 grains of soda, and water is added to make up the acid liquid to 100 measures. This forms a test acid of which 100 measures neutralize and are equivalent to 100 grains of soda, or one measure of acid to one grain of caustic soda. This acid ought to be kept in a well-stoppered bottle. By a curious coincidence, strong oil of vitriol diluted 124 TESTING SODA-ASn. with 1 1 times its -weight of water, gives this test acid exactly; but, as oil of vitriol varies a Httle in strength, it is better to form the test acid in the manner described, than to trust to that mixture. Twenty-one measures of the test acid should neutralize 100 grains of crystallized carbonate of soda, and 68'5 measures of it should neutralize 100 grains of pure anhy- drous carbonate of soda. To test a sample of soda-ash, 100 grains are weiglied and dissolved in two or three ounces of hot water. The alkalime- ter is filled with the test acid, which is gently poured into this solution, stirring, as each drop is added, until a piece of blue litmus-paper, which may be kept in contact with the liqiior, is turned red. The number of graduations taken to effect this indicates the per centage of caustic alkah in the sample. Another method of using test acid is by -height. The acid is made to such a strength as one or two grains by weight will exactly neutralize one gi-ain of pure alkali. The vessel commonly used for this purpose is of the annexed form, but any convenient vessel will do. It is fiUed with the test acid, and the whole correctly weigh- ed. The acid is then dropped from the small orifice into a weighed quantity of the carl)onate until a neutral sulphate is produced, indicated as above by test- paper. The bottle with its contents is then again weighed ; the loss of weight gives, by calculation, the quantity of real alkah in the sample. Say that every two grains of the test acid are equivalent to one grain of pure soda, and that twenty- five grains of soda-ash requii-e twenty grains of acid to neu- tralize it, the real alkah present will be ten. Now 25 being the fourth of 100, the 10 is multiphed by 4, giving 40 as the per centage of the sample. This method of testing carbonated alkalis, provided the operator has a good balance, is more cor- rect than that with the graduated tube, and equally simple. Another very ready method, sometimes recommended, is to take a small flask and a test-tixbe that will go inside, and stand nearly straight. Fifty grains of the soda-ash are dissolved in a Httle water in the flask, and the tube, which is nearly filled with sulphuric acid, is carefully placed in the posi- TESTING SODA-ASH. ISf) tion shown in the figure. A small chloride of calcium tube is fitted into the mouth of the llask, and the whole is then carefully weighed ; after which, by holding the flask a little on one side, the acid is poured from the tube into the soda so- lution. This should be done gradu- ally that the effervescence may not be too violent. When all effervescence ceases, and the flask is well shaken, the cork is taken out, that the rest of the carbonic acid may freely escape ; it is then put back, and the flask is again weighed : the loss of weight will of course indicate the loss of carbonic acid, and by this the quantity of soda present may be calculated. If the loss of weight be 1 grains, then as 22 the equivalent of carbonic acid, is to 31 that of soda, so is 10 to 14-09, which, being multiplied by 2, there being only 50 grains of soda used, gives 28*18 as the per centage of alkali in the sample. This method, however, is not much to be relied upon in testing the value of alkali. There are a great many other modes of proceeding, all em- bracing the same principles as those detailed, and also a great variety of apparatus for the pm'pose, but it is needless to men- tion them. It will be observed that the same principle applies to pot- ash as to soda. In the process where the loss of carbonic acid is made the criterion, the difference is in the equivalents. The equivalent of potash being 47 "2, the proportion becomes 22 : 47-2 : : 10 -|- 2 : 21-95 + 2 = 43 9 per cent. With the test acid process, there may be obtained an acid of such strength that one graduation will be equal to one grain of potash, which will be found in the same way as for soda, namely, by neutralizing a known weight of pure dry car- bonate of potash. The operation most frequently tried, is performed by neu- tralizing a given quantity of acid, which does for either soda or potash. — Prepare a little pui-e anhydrous carbonate of soda as described for the soda test ; weigh 53 grains, which is an equivalent, and dissolve in water, then take dilute acid in the alkalimeter, and add it to the soda until it is perfectly neutral ; mark the number of graduations it takes for this : 126 TESTING SODA-ASH. say it takes 30; then to every 30 of the acid add 70 of water, and thus we have a stock acid, of which 100 gradua- tions is equal to an equivalent of any alkali. Thus, , 100 graduations is equal to 32 grains caustic soaa, / ^ -■ 47'2 potash, ^^ 17 ammonia, 28 lime. To test by this method, take 100 graduations of the test acid, and weigh 100 grains of the alkaU, and dissolve in 100 mea- sures of water ; add this solution to the acid till it is neutra- lized, and mark how many measures have been necessary to effect this ; then tlie per centage of alkali is easily calculated. Say that 70 measures of the alkali solution have been neces- sary to neutralize the acid ; if the alkali is soda, then the 70 grains of soda-ash will contain 32 grains of caustic soda; and the per centage is I'ound by the following calcu- lation : — 70 : 32 : : 100 : 45-7 per cent. If the alkali is carbonate of potash, the 70 grams will contain 47*2 grains of caustic potash ; and then the per centage is found by the proportion : — 70 : 47.2 : : 100 : 67.45 per cent. For commercial salts, either of potash or soda, the mode of testing by neutralizing, is preferable to that which depends on calculating from the loss of carbonic acid, as there are sometimes portions of caustic alkali in the sample, which the carbonic acid process will not indicate. It may also be observed that the acid test for soda, derived from a coincident in their equivalents, will serve equally well for potash, each graduation being 1 of caustic soda, and 1^ of potash. The process for making caustic soda from soda-ash, is the same as described for making caustic potash, namely, a quan- tity of ash is boiled, and, when boiling, slaked lime is added until a small portion taken out does not effervesce on adding an acid ; but the equivalent of soda being less than that of potash, it requires more lime for a given weight. The following table, constructed by Dr. Dalton, will be -a^ SULPHATE OF SODA. 127 found useful to the operative bleacher, showing the quantity of caustic soda in his solutions, indicated by the hydrometer: Speciflc Gravity. AlkaU per cent. Twaddells Hydrometer. Specific G^a^ity. Alkali per cent Twaddell's Hydrometer. 2-00 77-8 200 1-40 29-0 80 1-85 63-6 170 1-36 26-0 72 1-72 53-8 144 1-32 230 64 1-63 46-6 126 1-29 190 58 1-56 41-2 112 1-23 160 46 1-50 36-8 100 1-18 13-0 36 1-47 34-0 94 112 90 24 1-44 310 88 1-06 4-7 12 The remarks, (page 113,) in reference to the presence of sul- phurets in potash-ley mjurmg the gold ornaments of light muslins, &c. are equally applicable here ; and the same tests for ascertaining the presence of these impurities in potash may be employed to detect their presence in soda solutions. W ith respect to the solubility of soda — 62° Fah. dissolve 41 parts of caustic soda, 90° „ 46 131° ,, 64 158° „ 72 „ 176° „ 78 ,, 100 parts water, at 100 100 100 100 Cold water, saturated with soda, and brought to boil, attains a temperature of 206° Fah. , . i • i The salts of soda are in general the same m their chemical characters as the corresponding salts of potash, but they are not so generally used, on account, perhaps, of the disposition which almost all soda salts have to effloresce when exposed to the air. . . , „ Salphate of Soda.— Soda, saturated with sulphuric acid, torms sulphate of soda, which crystaUizes easily, and is known by the name of Glauber Salts. A dry and impure sulphate of soda is sold under the name of salt cake; it is obUimcd by beating common salt and sulphuric acid in makmg hydrochloric acid It commonly contains about one-third of its weight ot salt A purer sort of salt cake is obtained by the makers ot 128 SALTS OF SODA. nitric acid ; in this process, the nitrate of soda is acted npon by sulphuric acid, and the product being valuable, consi- derable care is taken to have the nitrate decomposed. We have seen salt cake, from this source, containing as much as 98 per cent, of sulphate of soda. Chloride of Sodiam. — Hydrochloric acid, added to soda, forms hydrochlorate of soda (muriate of soda) — more properly, chloride of sodium, (common salt,) The action is as follows : Chloride Sodium. Soda, Na Hydrochloric Acid Water. This salt is sometimes employed 'vdih nitric acid to make the aqua regia used for dissolving tin. It is often amus- ing to see the care taken to mix the acid and the soda to form what may be got so conveniently as common salt. Nitrate of Soda. — Nitric acid, added to soda, forms nitrate of soda. This salt, as already stated, (page 52,) is found abun- dantly in nature, and is termed cubic nitre, from the shape of its crystals, and to distinguish it from nitrate of potash, (nitre.) When heated to redness, it is decomposed, and gives off much oxygen gas ; it is often employed for this purpose, and for oxidizing metals in a fused state. It is also occasionally used for preparing some of the salts of tin for mordants, along with hydrochloric acid. Borate of Hoda. — Boracic acid with soda, forms borate of soda, (borax or tinJcal.) This, as we have before noticed, (under Boron,) is also a natural product : it is used as a blowpipe re-agent for fluxing metals. Phosphate of Soda. — Phosphoric acid, with soda, forms phosphate of soda, also a useiul salt, as a test for the pre- sence of magnesia in water solutions. Soda, on account of its cheapness, has been substituted for potash in the manufacture of some of the salts most extensively used, such as ferrocyanides, chromates, alum, &c., but none of these modified salts have come into common use, not that they are less suitable in the dye-house, but for other reasons, which we need not here examine. SOAP. 129 Lithium. (L 6-5.) This is another alkaline metal, the oxide of which is termed Lithia. It has properties somewhat resembling those of soda and potash, and combines with acids as a base in the same manner as these other alkalis. It is, however, very rare, and only got in small quantities, from a mineral termed Lepidolite. It has not, as yet, been used in any process of manufacture, and has therefore no claim to ovu: further con- sideration. Soap. In connection with the alkalis, it will be necessary to direct attention to Soap, an article of great importance in the dye- house. If we take a quantity of oil, and add to it some caustic alkali, a milk-white solution is obtained, which is found to be soluble in water. This solution, boiled down to a pro- per consistence and cooled, forms soap. AU sorts of fats and oils are used in soap-making ; they all contain certain acids, capable of combining with the alkali, and giving a detersive character to the compound. The soap made with soda is hard, that with potash soft ; and the degree of hardness, in either case, varies according to the nature of the oil or fat employed. In manufacturing soap, care is taken to obtain a proper mixture of these fats and oils, so as to produce a soap of proper consistence. The following extract on this subject, from '■'■ Normandy'' s Commercial Hand-hooh of Chemical Sci- ence" is important : — " Mottled soap has a marbled, or streaky appearance ; that is to say, veins of a bluish or slate colour pervade its mass, which is white or whitish ; the size and number of these veins depend on the more or less rapid cooling of the soap after it has been transferred from the copper to the frames. The blue or slate colour of these streaks is chiefly due to the presence of an alumino-ferrugenous soap interposed in the mass, and frequently, also, to that of sulphm-et of iron, which is pro- duced by the reaction of the alkaline sulphurets, contained in the soda-ley, upon the iron, derived from the iron, copper, and utensils employed in this manuflicture, or, which even is, at times introduced purposely as sulphate of iron. The veins gra- g2 130 SOAP. dually disappear from the surface to the centre, by keeping, by the oxydation of the sulphuret of iron, A well-manufactured mottled soap cannot contain more than 33, 34, or at most 36 per cent, of water. The addition of water causes the colour to subside, and a white soap is produced. This addition of water is made when the object is to give white soap ; so that, with this additional quantity of water, white soap some- times contains 55 per cent. It is therefore best to buy mottled soap in preference to yellow or white soap, the mottling being a sure criterion of genuineness, as the addition of water or other matters would soon destroy the mottling." — This quality of soap is not much known in Scotland : even the name is not used. " To yellow or white soap," says Mr. Normandy, " in- creditable quantities of water may be added. I have known 15 gallons of water added to a frame of already fitted soap, (10 cwt.), so that the soap, after this treatment, contained upwards of 60 per cent, of water. Common salt had been previously dissolved in the liquor." " Besides being surcharged with water, soap is sometimes fur- ther adulterated with gelatine, made by boiling bones, sinews, hoofs, skins, fish, &c., in alkalis ; also with dextrine, potato- starch, pumice-stone, silica, plaster of Paris, clay, salt, chalk, carbonate of soda, &c., &c. Soft or hlach soap, is the most useful of all the soaps. It is made with fats or oils and a solution of potash, and always contains a great excess of alkali and much water ; also chlorides, sulphates, and other impurities. Fish oil is also often em- ployed in the making of this soap, which gives it a very dis- agreeable smell. Soft soap, which has a greenish colour, is best, although occasionally this colour is given to a very infe- rior article, by the addition of a little indigo. The quantity of water in soap may be ascertained by taking 100 grains of the sample in thin parings, putting them into a water bath or oven, of which the heat does not exceed 212°, and allowing them to stand as long as they continue to lose weight, which is known by occasional weighing ; the loss of weight indicates the water evaporated. In mottled soap, it should not exceed 35 per cent. ; in the Avhite and yellow soaps, it ought not to be more than 50 per cent. The other impurities of soap may be detected by dissolving 100 grains in strong alcohol, and applying a gentle heat: SOAP. 131 the soap is thus dissolved, and the impurities remain as pre- cipitate. The best soap should not contain above one per cent, of matter insoluble in alcohol. Good soap may be known by its comparative transparency. AVheu cut thin, the purer the soap is, the more translucent. Dry soap is also more transparent than wet. The earths combine also with fats and form soaps, some of which are difficijJtly soluble in water, so that if there be oil or grease upon goods, and they are put into matters that form an insoluble or difficultly soluble soap, these spots will be so many white stains in the dyed goods ; and when ordi- nary soap, made from fats, is put into water that has earthy matters or salts in it, these salts are decomposed by the alkali of the soap taking the acid, and greasy or insoluble soapy spots are produced. This is often experienced in washing with soap in hard water : these spots are sources of annoyance to the dyer. When soap is dissolved in water, there should be no oily or fatty matters visible on the surface, — as this would indi- cate that too little alkali had been used in the manufacture ot the soap. The following method of testing the quality ot soaps is given by M. Dumas, in the Chemie Appliquee aiix Arts, tome vi : — " To determine the quantity of water, thin slices are cut from the edges and from the centre of the bars. A portion is then weighed, about 60 to 70 grains, and exposed to a cur- rent of air, heated at 212" F., or in an oil-bath, until it ceiises to lose weight. The dry substance is then weighed ; tlie dii- ference between the first and last weighing will indicate the quantity of water evaporated. If it be a soft soap, it is weighed in a counterpoised shallow capsule. In good soap the amount of water varies from 30 to 45 per cent., in mottled and soft soaps, from 30 to 52 per cent. "The purity of soap may be ascertained by treating it witli hot alcohol ; if the soap be white, and without admixture, the portion remaining undissolved is very minute, and a mottled soap of good (juality does not leave more than about 1 per cent. " If there should l^e a sensible amount of residue from white soap, or more than 1 per cent, from mottled soap, some acci- dental or fraudulent admixtui-e may be suspected, silica, 132 SOAP. alumina, gelatine, &c., the quantity and nature of which may be determined by analysis. " The quantity of alkali contained in the soap is easily de- termined by means of the alkalimeter: a known quantity of the soap is dissolved in -water, and tried by the test acid. " There is no difficulty in ascertaining in the same assay the quantity of the fatty substance. For this purpose 150 grains of pure white wax, free from water, are added to the hquid after saturation with the test acid, and the whole heated to complete liquefaction ; it is then allowed to cool, and when it has become solid, the cake of wax and fatty matter which have united is removed and washed, dried and weighed ; the aug- mentation in weight beyond the 150 grains employed will give the weight of the fatty matter. "The hquid decanted from the soUdified wax may afterwards be tested to ascertain the purity of the base. " The solution of the sulphate may also be evaporated, and by an examination of its crystalline form, or by means of chlo- ride of platinum, it may be ascertained whether the base be soda or potash, or a mixture of the two. " As to the nature of the ilitty substance, it is ascertained, with more or less certainty, by saturating the solution of the soap with tartaric acid, coUectmg the fat acids, and taking their point of fusion. It is possible, at least, by this to prove the identity or the absence of identity with the sample iu the soap supplied, for instance Avhether it is made from oil or tallow, &c. The odour developed by the fatty acids, at the moment of the decomposition of the soap by acids assisted by heat, will often indicate the nature of the fatty substance employed in its fabrication, or that at least of which the odour mav pre- vail. " The soap is proved to contain an excess of fatty matter not saponified, by separating the fatty acids by means of hv- drochloric acid, washing with hot distilled water, then com- bining them with baryta, and thoroughly washing the new compomid with boiling water. Tlie non-saponified fatty mat- ter is easily separated from the barytic soap, by treating the mass with boiling alcohol, which dissolves the fatty substance. We can, moreover, asstire ourselves that it has no acid reac- tion on moistened htmus-paper, that it is fusible, and that it possesses the general characters of a neutral fatty substance." STRONTIUM. 133 Barium. (Ba 68-5.) This is a metal having a silver -white lustre, and consider- able ductility ; it is four times heavier than water, rapidly oxi- dates when exposed to the air, forming Barytes, one of those substances termed earths, and which has strong alkaline properties. This earth, which was decomposed and its metal- lic basis discovered by Sir H. Davy in 1808, exists abun- dantly in nature, in combination with sulphuric acid, forming sulphate of barytes, {heavy spar,) and with carbonic acid forming carbonate of barytes. The artificial salts are gene- rally prepared from the sulphate, which is groimd fine, mixed with charcoal, and kept at a strong red heat in a crucible for about an hour. Sulphuret of barium is thus forined. This is now acted upon by nitric or hydrochloric acid, to form the nitrate or chloride, according as one acid or the other is used. These salts may also be obtained from the carbonate with- out previous heating, by n^erely digesting the mineral in the acid. Chloride ofBarinm is a crystalline salt, of which 100 parts of cold water dissolve about 43 parts. Nitrate of Barytes is also a crystalline salt, but not so soluble in water ; 100 parts of cold water dissolve only about 8-g- parts of it. The affinity of barytes for sulphuric acid is very great ; it takes it from every soluble substance, and forms with it an insoluble precipitate. Hence it is that barytes is pre-eminently the test for sulphuric acid. The Acetate of Barytes is sometimes used to precipitate the sulphuric acid of alum, and form an acetate of alumina ; but this use of the salt is not very extensive. Strontium. (Sr 43 '8.) This is a metal very similar to Barium in appearance and properties. Its oxide is termed Strontia. It is another of the earths which has alkaline properties, and which occurs in nature in combination with carbonic and sulphuric acids, although not very abundantly. The artificial salts are pre- pared Irom the carbonate, by acting upon it with nitric or hydrochloric acid, by which is formed nitrate of strontia, or 134 CALCIUM. chloride of strontium, both crystalUzable salts. Its solutions precipitate sulphuric acid, but not so fully as the solutions of barytes. The salts of strontium are not used in manufactures, except indeed for fireworks : they have the property of com- municating a red colour to flame. Calcium. (Ca 20.) This is a metal of which the oxide is Lime — one of the most widely diffused of all the earths, and also one of the most generally useful. It exists in nature as a carbonate and as a sulphate. Ordinary limestone, chalk, marble, &c. are car- bonates ; gypsum, plaster of Paris, &c. are sulphates. Cansiic lame is obtained by heating the carbonate to red- ness — which is the ordinary process of lime-buming in a kiln. The carbonic acid is di-iven off, and caustic or burned lime remains. The caustic hme combines rapidly with one equivalent of water, and, becoming a hydrate, falls into a fine powder, commonly termed slaked lime, Duiing this operation, much heat is evolved from the water as it passes fi'om a fluid to a sohd state in combining with the lime, and gives out its heat of fluidity. Lime is soluble in water, producing lime-water, which has an alkaline reaction, much valued in the dye-house. It takes 78 gallons of water at 60° to dissolve one poimd of lime ; 97 gallons at 130^ and 127 gallons at 212". Thus we see that cold water dissolves more Hme than hot water ; so the practice of putting boiling water into lime, in order to get a strong solution, is erroneous ; and when a boiler is filled with cold lime water, and brought to boil, as when oranges ai-e to be raised, we see why there is always a quantity of powder deposited ; for, as the hot water does not hold the same quantity of lime in solution as the cold, the surplus is deposited m fine crystalline grains. Lime water, exposed to the air, absorbs carbonic acid rapidly, forming a thin pelicle on the surface, which, falling down from time to time, the lime in the solution will ultimately be all deposited. Lime, in its caustic state, is extensively used in the dye-house, and we will hereafter have occasion to refer to it when de- scribing the operations of the trade. MAGNESIUM. 135 Lime combines with the acids, forming a series of salts of little practical use to the dyer. With hydrochloric acid it forms the chloride of calcium— a very delitiuescent salt, which is sometimes on that account used in absorbing moisture from gases, &c. It is formed in the spontaneous decomposition of bleaching powder, which it makes damp. (See page 74.) Sulphate of liime is an insoluble substance, or nearly so, the acid and lime having a strong affinity for each other. This salt is formed in the common blue vat by the sulphate of u-on. It is held in solution in very minute quantities in some spring waters. Carbouate of i^iine {Limestone) is soluble in water holdmg carbonic acid, probably forming a bicarbonate of lime. The best test for the presence of lime is a solution of oxa- late of ammonia, which gives with hme a white precipitate. Magnesium. (Mg 12-2.) This is a silver-white metal, ductile and hard, and oxidate? rapidly when exposed to moist air and in water. Mngiiesia. — The oxide is the well-known alkahue earth mag- nesia, which, having a low combining equivalent, is remarkable for its great power of saturating acids. Magnesia is abundant in nature" but it is found chiefly in the state of carbonate. There are immense beds of it in combination with lime, termed magnesian limestone. The carbonate is soluble in water, which contains free carbonic acid, and imparts to the water a slightly alkaline reaction. ]\Iagnesia combines with the acids, and forms with them a series of salts of considerable im- portance in several manufactures and in medicine, but they are not much used in dyeing. The salt principally used is the sulphate, (Epsom salt,) which exists in certain springs, and is easily prepared by satirrating magnesia or car- bonate of magnesia, with sulphuric acid, and evaporating the solution to crystallize the salt. Salts of magnesia in water are very bad for delicate colours. The best test for its pre- sence is phosphate of soda, with which, after long stirring, it gives a white precipitate, even with very minute quantities. The five elements — Glucinum, Beryllium, Yttrium, Tho- rium, and Aluminum — have been termed the metals or bases of the earths proper, to distinguish them from the four elements 136 ALUM. we have just been considering; these, from having alkaline properties, have been termed tlie alkaline earths. The first named four elements of the earths proper are very rare, and their characters have been studied by very few chemists ; accordingly, little is known about them, and as no practical application has been made of any of them or their salts, we may dismiss them with this brief notice. But the fifth, namely, aluminum, is of vast importance, and consequently demands special attention. Aluminum. (A1 13* 7.) The metal Aluminum is obtained as a greyish powder, very difEcult to fuse, and attracts oxygen slowly. Alnmina. — There is only one oxide of aluminum known, which is a sesquioxide, AI2 O3. This is termed alumina, which is the pure plastic principle of clay, and is exceedingly abundant in nature as such. It combines with acids, forming salts, but it only combines in the proportions stated : thxis, by dissolving alumina in hydrochloric acid there is formed — Alumina i'^ ? ^^ 3 Water. 3 Proportions hy- (3 H.. --^ -^„.^__^ Chloride of Alu- drochloric Acid (3 CI.. ^^^^ minum. Alum. — Alumina is easily dissolved in sulphuric acid, form- ing the sulphate of alumina, Avhich crystallizes with much diffi- culty; but this salt has a strong affinity for the sulphate of potash; so that when these two salts are mixed, or when a salt of pot- ash is added to a strong solution of sulphate of alumina, they combine, and form common alum, which is easily crystallized. This is what chemists denominate a double salt, being com- posed of two sulphates — the sulphate of alumina, and the sul- phate of potash. This salt has been known, and in general use among dyers, since the earliest accounts wc have of their processes ; but the true nature of its composition was not known till the present century. The alchymists knew that sulphuric acid was one of its constituents ; and during the last century, it was discovered that the precipitate which falls when the acid is neutralized by an alkali, is a particular kind of earth which chemists called alumina, because of its being ALUM. 137 obtained from alum. Amongst other pectdiar properties of alumina, it has a strong attraction for organic matter, and withdraws it from solutions with such force, that if the pm^est water be not used when preparing it, the alumina is coloiu'ed ; and when digested in solutions of vegetable colouring matters, provided the alumina be in sufficient quantity, it will carry down all the colouring matter from the liquid. By this means the pigments called lakes are formed; and it is this that makes it so valuable as a mordant. The fibre of cotton, when charged with this earth, atti'acts and retains colouring matters. A very pure alum is obtained in the Roman States from alum stone, a mineral which is continually produced at the Sol- fatara, near Naples, and other volcanic districts, by the joint action of sulphurous acid and oxygen upon some of the fels- pathic rocks. This mineral contains an insoluble subsulphate of alumina, with sulphate of potash ; but it is partially decom- posed by heat ; so that, for the preparation of alum, the mineral is simply heated, till sulphurous acid begins to escape, and is then treated with water, by which process a very pure and excellent alum is prociu-ed — much superior to that manu- factured in this country. The alum of this country is manu- factured from a mineral termed ahim shale, a kind of clay slate, much impregnated with sulphviret of iron, which is essen- tial to the manufacture. The general composition of this altim ore, as it is also called, is as follows, observing that the proportions of the several components vary according to the depth from which the ore is obtained : the table is therefore to be considered as giving only the average constitution : — Sulphuret of iron, 2G"5 Oxide of iron, 3'1 Alumina, 18"3 Silica, 10-5 Lime and magnesia, 3"0 Magnesia, potash, soda, 1"4 Coaly matter, 28'7 Water, 8-5 1000 The ore is built up in large heaps, with alternate layers of coal : these heaps are set on fire, and allowed to burn for several weeks. During this roasting process, a portion of the 138 ALUit. sulphur is expelled, but the greater portion of it is converted tirst into sulphurous acid, by taking an equivalent of oxygen from the atmosphere, and finally into sulphiuric acid, by taking a further proportion from the peroxide of iron con- tained in the mineral. The sulphuric acid does not, how- ever, remain isolated, but combines •with the iron and alu- mina, and forms sulphates with these oxides. The roast- ing being completed, the material of the heap is removed to large tanks or pits, into which water is allowed to flow, and which dissolves out the sulphates formed in the process. The solution is run into large tanks and evaporated, generally by causing a current of dry heated air to pass over the surfece of the liquid. When the solution is in this way sufficiently concentrated, the sulphate of iron crystallizes, and is then re- moved ; the sulphate of aliimina, being very difficult to crys- tallize, remains in solution. All the ii'on having by this means been separated, the sulphate of alumina in solution is removed to other vessels, where there is added to it sulphate of potash, chloride of potassium, or other salts of potash. There is then formed the double salt of potash and alumina, wliich is alum, and which, after a few days standing, crystallizes, and is re- moved and packed for the market. There are some modifica- tions of this process adopted by different makers, but this description exhibits the general practice of the manufacture, and illustrates sufficiently the principle upon which the prac- tice is necessarily based. Soda may be used in the operation instead of potash, which would give a soda alum, but, nowithstanding its being cheaper, there are practical objections to it. Soda alum is not so easily crystallized as common alum, and it effloresces when exposed to the air, which makes it take the appearance of a dry powder. Sulphate of ammonia may also be used instead of potash, giv- ing an ammonia alum, which, however is expensive, and pos- sesses no corresponding advantage over the ordinary article. The following analysis, by Dr. Thomson, of the alum made in this country, will be useful : — Potash, 9-86] ^ , , Alumina, 1109 f ., r» o cr\ 7rn°cr» . nA xjf\ Sulphuric acid, 3285 f ^^^ ^' ^ b03+K0 bO,+24 HO. Water. 46-20 j 100 00 ALUM. 139 Thus every 100 lbs. of alum contain 46 lbs. of water. From the nature of the processes by which the alum is manufac- tured, we may expect it to contain small traces of sulphate of iron, a substance very deleterious to its use as a mordant or alterant. Iron may be detected by dissolving a little of the salt in distilled water, and adding a few drops of a solution of red prussiate of potash ; or boiling a little, with the addition of a few drops of nitric acid, and adding yellow prussiate of potash. In both cases, a deep blue colour is immediately pro- duced, if iron is present. The addition to a solution of alum of a few drops of gallic acid will give a black colour if iron be present. Or, if a little alum be put into a vessel, and caustic potash added till the sokition is strongly alkalme, then the whole boiled, and set aside to cool and settle, the alumina will be dis- solved, and if iron be present, it will subside to the bottom as a brownish precipitate. When the proportion of iron is consider- able, it is better to reject the alum altogether, especially for bright light shades. We have often experienced bad effects from the use of such alum upon light shades of drab and fawn colours, when dyemg to a particular pattern. Having obtained the particular shade, on adding a little alum as raising, the iron, by combining with the sumach upon the cloth, produced a colour two or three shades darker than required ; leaving no alternative but to take off the colour, and dye anew — a pro- cess much more difficult, and which produces a colour much less brilliant than the first. Pure alum is soluble in water, and should give a colour- less solution. One gallon of water at 54° Fahr. dissolves 1 lb. alum. One 86 2 One 140 3 One 158 9 One 212 35 Alum forms but a weak mordant for cotton goods, owing to the strong attraction Avhich the sulphuric acid has for the alumina ; and in this state there are three proportions of acid to every two of alumina. But if we neutralize a portion of the acid, so that no more remains than is necessary to hold the alumina in solution, which, according to experiment, is not above a third of the acid contained in common alum, its proper- 140 ACETATE OF ALUMIXA. ties as a mordant are greatly improved. That the amount of acid admits of being reduced, may be proved by taking a quantity of carbonate of soda, sufficient to neutralize the whole of the acid contained in a given portion of alum, dividing the soda solution into three equal portions, and adding gradually to the aluminous solution (stirring all the time) two of these portions : it will be found that, although the alumina is at first precipi- tated, by keeping up the agitation for some time, the precipi- tate again dissolves, foiining an alum contaiuing only a third of the acid of common alum. In this state, alum is a more powerful mordant for cotton, as the base is held more feebly by the sulphuric acid, and is readily detached by the superior affinity of the cloth to fonn a mordant ; and thus prepared, it is perfectly pure : any iron formerly present is precipitated in the process. Alum in this state is knoAvn by the name of cubical or basic alum, from the form in which it crystallizes. We have already referred to Roman alum being superior to other alums. For a long time, the dyers considered this su- periority to be whoUy o^ving to its purity ; but a chemical investigation shows it to be caused by the small quantity of acid it contains in comparison with ordinary lUum. Acetate of Alamina. — The most common, and we believe, the best method of using alumina as a mordant, is by sub- stituting acetic acid for sulphuric acid as its solvent. Tlie acetate of alumina has several advantages over the sulphate : 1st, the acetic acid is not so hurtful in its action upon the vegetable colouring matter; 2d, it holds the jdumina with much less force than sulphuric acid, and consequently yields it much more freely to the cloth ; and 3d, being volatile, a great portion of the acid flies off during the process of drying. "VVHien strong colours are wanted, and the mordant is of such a nature as will admit of being dried, it is better to dry the cloth from the mordant previous to dye- ing. This last property of acetic acid is very convenient, as it frees the cloth from any superfluous acid which may have been in the mordant ; besides, it has been foimd that dur- ing the drying by heat, the soluble acetate is converted into a less soluble subacetate. We may here put the dyer in mind that when goods containing volatile acids are drying, no other goods should be allowed to be in the same apartment, as the acid wiU be absorbed by them, and ^viIl affect almost ACETATE OF ALUMINA. 141 any colour that either has been or may be put upon them. Many unpleasant and also expensive consequences occur from the neglect of these precautions. The acetate of alumina is easily prepared by mixing a solu- tion of acetate of barytes, lime, or lead with alum. When any of these salts are added to alum, a double decomposition takes place ; the sulphuric acid of the alum combines with the base of the salt Avhich fails to the bottom, and the acetic acid unites with the alumina, forming acetate of alumina, which remains in solution mLxed with sulphate of potash, which formed a con- stituent of the alum. The acetate of lead is the salt generally used for this purpose in the dye-house ; the proportions of the lead and alum vary according to the nature of the colour to be dyed and the peculiar taste of the dyer, for the preparation of this substance is one of those operations which every one who practices it thinks he has the best method, but so far as we have had an opportunity of knowing, the superiority only existed in the mind of the individual, or rather in its being kept secret. In the proportions used for the preparation of this mordant there is never a sufficient quantity of acetate of lead to precipitate all the sulphuric acid in the alum. This crystallized acetate of lead has an equivalent of 190, and that of alum crystals of 475; but the alum, having 4 equivalents of sulphuric acid, would require 4 equivalents of acetic acid to take its place. Thus, ., {2 Al , Acetate of alumina. Alum \ g gQ contains S i K.. '.*.'.' *....^^..^_ Acetate of potash, exclusive oi water, | -i qc \ . It would take TS Aceticacid/ 4 proportions < 1 Aceticacid/ \\ acetate lead. (^4 Pb —^Sulphate lead. So that the equivalent of acetate of lead 190 must be multi" pUed by 4, giving 670, to be equal to 475 of alum. This is far from the proportions used, showing that the mordant is not a ptu-e acetate of alumina, but a mixture of salts, probably of cubic alum with acetate of alumina and sulphate of potash. The following metliod we have generally foimd to answer very well : — Into a boiler or pot put 20 lbs. of crystallized alum with about nine gallons water, and boil till the alum is 142 ACETATE OF ALUMINA. completely dissolved. In a separate vessel dissolve 20 lbs. of acetate of lead in about three gallons of boiling water. This is added to the alum while at a boiling heat, and well stirred. The sulphuric acid combines with the lead, forming an insoluble sulphate of lead, which falls to the bottom as a lieavy white precipitate ; the soluble part constitutes the mordant. The difference in the preparation of this mordant is in the propor- tion of lead varying from one half of the alum to equal weights. There is also added to the alum and lead a quantity of carbonate of soda varying from four to eight ounces to the five pounds of alum. This is added for the purpose of neutralizing a portion of the acid ; but there are many dyers who will not use soda or any other alkaline substance when light bright shades are wanted, under the impression that the colour is much brighter without alkaUs, bu.t the difference of hue is hardly perceptible; some use lime ; soda, however, is best. Without soda or some other alkaline substance, the mordant is not so effective. There are also some who object to the use of soda, as it throws down the alumina ; but we have already noticed that a very little acid holds the alumina in solution ; so that although soda, when added to the acetate of alumina, appears to precipitate the alumina, by a little agitation the precipitate is again dis- solved, forming a mordant better adapted for strength of colour. From the following recipes, taken from a French work on dye- ing, it will be observed, that the quantities of the aluminous mordants are similar both in England and France: — 60 gallons buihng water, "j 100 pounds alum, f Ihis mordant is best 100 pounds acetate of lead, t adapted for reds. 10 pounds crystallized soda, ) 80 gallons boiling water, ^ 100 pounds alum, (This is best for bright 50 pounds acetate of lead, f yellows. 6 pounds soda, / In addition to the above, Dr. Ure in his Dictionary of the Arts and Manufactures, article " Calico-Printing," gives another proportion : — 50 gallons boiling water. 100 pounds alum. 75 pounds acetate of lead. 10 pounds soda. ACETATE OF ALUMINA. 1^3 The following curious phenomenon was observed by Gay Lussac, viz., that the solution of a pure salt of the acetate of alumina may be boiled without decomposition; but if sulphate of potash, or any other neutral salt of an alkali be present, the solution becomes turbid when heated, and a basic salt precipi- tates, which dissolves again on cooling Now the acetate of alumina, prepared from the common alum, always contains sulphate of potash. If by the presence of this salt a portion of the acetate of alimiiua be thrown down when hot, and incorporated with the sulphate of lead, which falls in a very dense state, it may there be lost to the dyer. AVliether this be so we know not, as we have not, since we knew of this phenomenon, had an opportunity of putting it to the test; but it would be advisable to stir the whole after becoming cold, that if any of this basic salt should be bound up with the pre- cipitate, it might be set at liberty and dissolved ; but it must be borne in mind, that if this be stirred when cold, it takes a long time to settle. Nearly all the acetate of alumina used in dyeing, is pre- pared from pyroligneous acid, and is called by calico-printers red liquo7', but by dyers mordant. No other substance, whatever be its nature, is distinguished as mordant. AU other mor- dants have their technical names. The pyroligneous acid is one of the products of the destructive distillation of wood. The hard woods, such as oak, ash, birch, and beech, alone are used ; they are put into large cast-iron cylinders, so constructed that a fire plays about them so as to keep them at a red heat, and having openings through which all volatile matter escapes by pipes, which lead into condensing vats. The products thus obtained consist principally of pyroligneous acid, mixed with a black tarry matter, having a very strong smell, from v/hich the acid had its name, although it has been long since kuo\s'n that it is simply acetic acid (vinegar.) There is a great variety of other substances present, some of which have very singular properties, and some of the continental chemists suppose, they might be made available in dyeing. The products of the dis- tillation of the wood are allowed to stand for some time, after which as much of the tarry matter as swims is skimmed off; the remainder is filtered, after which it is put into a boiler and heated a little, and lime added by degrees, till the acid is neu- trahzed ; then a quantity of lime is added in excess, and the 144 ACETATE or ALU5HXA. whole is made to boil ; this throws up the tarry matter to the top, where it is taken off. When it is purified as much as it can be by this means, it is syphoned off into another boiler, and a quantity of alum is added ; the acetate of hme, the sulphate of alumina and potash, mutually decompose each other ; the sulphate of lime falls to the bottom; and the acetate of alumina remains in solution, which, when sent to the dyers, has some- times a specific gravity of 1-90, (18 Twaddell) although it is often weaker, ranging from 12 to 18 Twaddell. It has a dark-bro^vn colour, and a very strong pyromatic odour. When the acetic acid is wanted pure, it passes through a num- ber of other processes which do not come within our province to describe in this place. There is a considerable difference in the quality of red liquor, which the mere specific gravity does not indicate, as this can be brought up by the addition of foreign matters such as British gum, dextrine, and such hke. A very simple me- thod may be adopted to test the effective quahty of the mor- dant : — Take a little of the liquor, and evaporate it to dryness, then burn the residue at a red heat until white in colour ; put this into distilled water, which wiU dissolve out all but the alumina. Another way is by digesting a little of the red liquor in nitric acid, adding ammonia until the Hquor smells of it, and then by filtering, the alumina is obtained upon the filtei'-paper. We will add four varieties here, to show the variableness in quality of the liquor as supplied to the d}'er. The quantity given refers to the per centage in solution. t^ ,. , , ,. ii„T ji (acetate of alumina 15'3 English red hquor-U° Twadd. \,^ip^,^^^ ^f potash -8 Scotch, No. 1-13J° Twadd. Scotch, No. 2— 14" Twadd. Scotch, No. 3— 15° Twadd. 16-1 acetate of alumina '.sulphate of potash 11-5 2-3 J 3-8 /acetate of alumina \sulphate of potash 14- 1-2 15-2 ("acetate of alumina (sulphate of potash 12-2 2-6 14-8 . ALUM MOKD ANTS. 145 We have given these varieties to show how little rehance ought to be placed on the indications of the hydrometer. No. 3 is of a higher specific gravity than the English red liquor, but far inferior as a mordant. Again, such a mordant as No. 1 has a tendency to make light spots upon goods dyed green by fustic or bark, the alumina being the effective agent in the red liquor. The above is an ample illustration of the necessity of some better mode of testing than at present in use. During the various applications of these aluminous mor- dants, and the manipulations attending them, many curious and interesting chemical phenomena are witnessed by the dyer, although his familiarity with them often prevents any parti- cular remark ; we shall instance one or two of those attendant upon the process of dyeing madder reds, by means of acetate of alumina. This process, however, is more immediately con- nected with calico-printing, while our particular object in this work is dyeing yarns and cloth to be finished as such. The cloth to be dyed is first thoroughly bleached and dried, it is then padded or soaked in acetate of alumina, about the specific gra^aty of 40°, (8 Twaddell,) and passed at full breadth through nipping rollers (squeezers). 'J'hese are large rollers covered with cloth, which revolve one upon another. The pressure upon the piece, as it passes through for the purpose we are describing, ought to be such that it will dry in five minutes, passing over rollers in a stove heated to 1 60" Fah. Pieces mordanted with acetate of alumina, and dried at a great heat, are higlily charged with electricity. If the hand be suddenly drawn along the piece, a complete shower of fire is observed, with a sharp cracking noise, at the same time a prickling sensation is felt. "NYliether this has any effect upon the mordant, in its immediately combining with other sub- stances, we do not know ; but cloth in this state is very ill to moisten : water runs off it as off a duck's wing, but as yet we offer no explanation. After being dried, the goods are passed through a dung bath, made up with about one part cow's dung to fifty parts water, at a heat of 1 30" Fahrenheit; from this they are well washed through the dash wheel. Into a boiler of cold water is put from one to three pounds of madder, according to the colour wanted, for every pound of cloth. The cloth is put in, and a fire is kindled under the boiler, and so regulated that it will boil in H 146 ALUM MORDANTS. two hours, during which the cloth is kept running over a winch or wheel, first the one direction and then the other, and kept spread as much as possible, so that the whole surface may be equally exposed to the dyeing operation. The boiler is kept at the boil from twenty to thirty minutes : this, with washing first through bran, and then water, completes the dyeing operation. If a white pattern be wanted upon these reds, the pattern is printed upon the goods with citric acid, (about 25° of Twaddell, thickened with pipe-clay and gum,) about twelve or twenty-four hours after being dried from the mordant. This decomposes the aluminous mordant upon these parts, so that no dye adheres to them afterwards. It is of the utmost consequence that the goods be thoroughly cooled previous to printing on the resist, otherwise there is danger of it not being successful. Now, from a difference in the manipulation, or a little vari- ation upon some of these processes, several curious changes take place upon the mordant. For example, were the pieces merely washed with water from the mordant, previous to printing on the resist acid, although the treatment be every way else the same, the discharge of the mordant is not effected; those parts upon which the citric acid is printed wiU be scarcely obserA'able after the cloth is dyed, while in the other case they are perfectly white. A somewhat similar result, in reference to the action of the discharge acid, takes place, if the heat of the stove in which the goods are dried from the mordant exceeds a certain tem- perature, or if dried upon steam rollers.* No acid, printed upon the cloth after this, will produce a white, except it be of a strength that will destroy the fabric of the goods ; besides this, the colours afterwards dyed upon mordants heated in this manner are extremely bad, being heavy and dull. Various opinions have been offered by practical men upon the probable cause of these changes : some suppose that by the excess of heat, the acetate of alumina is altogether decom- posed, the acetic acid flying off, and the alumina left in the goods adhering with such an aftinity, that it requires a stronger acid than the cloth will bear to disengage it ; but from the similarity of the effects which take place, by merely washing " Large metal cylinders, into which steam is admitted, and the cloth passed over the surface. SALTS OF ALUMINA. 147 the piece fi'om the mordant, this opinion is liable to objection, for the sub-acetate of alumina is not decomposed by washing with water; however, different causes may produce the same effects. If this opinion be correct, the circumstance of a bad colour resulting from the acetate being decomposed, will be a proof that it is not the alumina alone which constitutes a mordant, but its salt ; in this case, it is the sub-acetate of alumina — the acetic acid being an essential ingredient to the dyeing process. This we are inclined to believe, for in those mordants, as we have already stat-ed, where the acid can be separated by washing, the proper colour is not produced until some salt or acid be added to the colouring matter as an alter- ant. It is supposed by some writers that the dunging and washing extract the acid from the mordant, and leave the base upon the cloth. This, we conceive, to be an error ; for although the part which dung acts in these processes is not well understood, yet, from the analysis of this substance, and the nature of the salts which are supposed to be useful in these operations, there is no probability of the aluminous salt being decomposed. One principal use of the dung bath is to combine with and carry off any loose or supernatant mor- dant which may be upon the cloth, not combined, and which might affect the colour, or more particularly the parts wanted to be white. Alumina combines with all the acids, forming salts similar to those already described, and all difficult to crystallize, ex- cept as double salts — such as alum — which they form with other salts besides those named; but none of the others have been introduced into the dye-house. Alumina, as an earth, is of great value in many other arts, as in pottery, brickmaking, &c. It also forms the bases of some of the finest precious stones : the sapphire and ruby, for example, are nearly pure alurainju The salts of alumina, such as alum, act towards other salts and reagents, as under : — Potash "White precipitate, which is redissol- ved in an excess of the precipitant. Ammonia White precipitate, insoluble in an excess of the precipitant. Carbonate of potash White precipitate, not soluble in an excess of the precipitant, but soluble in caustic potash. 1 48 MANGANESE. Caustic soda, and its carbonate, act in the same way as caustic potash and its carbonate. Carbonate of ammonia, and phosphate of soda, act in the same way as carbonate of potash. All these precipitates are soluble in acids. Oxalic acid No precipitate. Yellow prussiate of potash... Precipitate, after standing for some time. Red prussiate of potash No precipitate. All these precipitates of alumina have a bulky and a kind of plastic appearance, easily recognized and distinguished. When a substance containing alumina is heated to redness, especially before the blowpipe, and is touched with a solution of nitrate of cobalt, and then again heated, it takes a beautiful blue colour. In this way a very small portion of alumina may be detected in any sohd substance ; but when the substance is in solution, it must be detected by the reaction of some of the re-agents given above. It may also be noticed, that when operating to obtain a precipitate, it is necessary to be careful that only pure water is used for washing the precipitate. If the water is not pure, the precipitate will attract the impurity, especially if it consists of any organic matters, and thus become tinged, and assume an appearance as if iron were present. The next general division of chemical elements consists of the Metals Proper. These are very numerous, but a great many of them are so rare as to have been seen by a very few chemists, and are only obtained in particular localities, consequently their properties have not been much investi- gated, and no practical applications have been made of them. Of these a very short description will suffice, so that our remarks may be more extended upon those which have a known practical value. The first of which is Manganese. (Mn 27-6.) This metal is not found in nature in a separate state, but exists abundantly in combination with oxygen. From this circumstance it was long considered a species of earth. MANGANESE. 149 like magnesia, and was consequently called magnesia nigra, but it was discovered to be the oxide of a metal in 1774 by Sdieele and Gahn, and was then named manganese. As a metal, it has a greyish-white lustre, resembling cast- iron ; it is very difficult to fuse, and it combines with oxygen so quickly, that it cannot be kept in the open air. It passes into several states of oxidation. The one in which it gene- rally exists in nature is the peroxide having 2 proportions of oxygen to 1 of metal = Mn O2. AVhen this oxide is heated at a low red heat, it loses a part of its oxygen, and passes into the state of sesquioxide = Mug O3. When heated to bright redness, it loses more oxygen, and becomes what is termed red oxide, or a mixture of the protoxide Mn O and of the sesquioxide Mn^ O3. The peroxide does not unite with either acids or alkalies. When boiled with sulphuric acid, one pro- portion of the oxygen is evolved, and the protoxide Mn O unites with the acid, and forms sulphate of manganese, which is used in dyeing. Peroxide, or black J fJ" ^^ °' oxideof manganese I \r'*^ ^ J J . .. (H... ^v,^ Water. P \S04. -— ^^Sulphate of manganese. When the peroxide is digested in hydrochloric acid, chlo- rine is evolved, and chloride of manganese formed. This is often done in houses for the purpose of fumigation. The reaction is thus expressed : — /CI... Chlorine gas. Two proportions hydro- J CI... chloric acid ] H... jo ^^A^ Water. Binoxide manganese .. -| O -^ Water. (_Mn.. — -^Chloride manganese- The oxide of manganese is extensively used in the manu- facture of bleaching powder, for obtaining the chlorine from common salt. (See page 71.) Manganese combines with almost all the acids forming salts, which in their crystallized or dry state have less or more of a pinky hue. In making these salts from the per- 150 MINERAL CAMELEON. oxide, there is always oxygen liberated ; they are therefore all what are termed salts of the protoxide. But by removing the acid, the protoxide soon combines with more oxygen, and becomes brown. It is this circumstance that has made it applicable in dyeing. In preparing any of the salts of man- ganese for dyeing purposes, care should be taken that the salt be free of iron, as that metal is deleterious. The sulphate of manganese may be freed from iron by exposing it to a red heat, then dissolving the residue in water. By this means the iron present is peroxidized, it is thus rendered insoluble, and consequently sinks to the bottom. When cotton is passed through a solution of sulphate of manganese, and then through a weak solution of an alkali, the manganese oxide is left within the fibre, and by exposure becomes brown by attracting more oxygen. Or if the cloth be immediately passed through a solution of weak bleaching liquor, the protoxide is converted into peroxide Avithout exposure. This is the method generally adopted ; it gives a brown, which is very dull and heavy, but also very per- manent. iTiincral Cameleon. — When peroxide of manganese is fused with carbonate or caustic potash, there is formed what has been long known as the mineral cameleon. Wlien this is first put into water, it produces a deep green solution, but passes rapidly to a red by absorbing oxygen. This compound is not used in dyeing, but we think it contains properties worthy of examination. It illustrates very forcibly the effects of oxygen in changing the colours of substances, and the rapidity with which these changes take place ; accordingly teaching the necessity of attending to every condition, no matter how apparently trifling, as often the merest trifle may be of the greatest consequence in a process. The salts of manganese, in solution, are affected by the foUomug re-agents : — Potash Brown precipitate. Soda and ammonia Brown precipitate. Carbonates of potash and soda Brown precipitate. Yellow prussiate of potash Dirty-green precipitate. Ked prussiate of potash Brown precipitate. Manganese is easily detected by this general property of IRON. 151 turning brown when exposed, and giving a browu with all the alkaline re-agents. Irox. (Fe 28.) This is one of the most useful, generally diffused, and abun- dant of the metals. There is almost no substance, whether organic or inorganic, quite free from iron. Its uses in the various arts and purposes of life are innumerable. The most common iron ores of this country are the clay iron-stones, of which there are several varieties, and in which the iron exists as a carbonate along with silica, alumina, carbon, and a little sulphur. The ore is first calcined at a red heat, which expels the carbonic acid and sulphur ; it is then mixed up with limestone and coal, and put into a blast-furnace, and subjected to intense heat, the ciU'ct of which is, that the silica and alu- mina combine with the lime, and form a glass ; the coal takes the o.xygen from the iron, and passes off" with it as carbonic acid ; the metal meantuue fuses, and, in consequence of its superior gravity, sinks to the bottom of the furnace, while the glass and scoria) float above it, and are run off" separately when the furnace is tapped. Iron combines with oxygen in two proportions — Protoxide of iron ,. Fe O. Peroxide of iron FCi O3. IJoth of these oxides unite with acids, and form with them two classes of salts, distinguished from each other by affixing pro and per to their names. Both salts are extensively used in the dye-house. M. Freiny gives the following statement of what he called a third oxide of iron, which he had obtained in combination : " This oxide is obtained by igniting a mixtiu'e of potash and peroxide of iron ; a jjrown mass is the result, which, by digestion in water, gives a beautiful violet-red coloured solu- tion. The compound is very solulile in water. A large quantity of water decomposes it in course of time. But it becomes insoluble in very alkaline water, forming a brown precipitate, which readily dissolves in pure water, and atlbrds a fine purple-coloured solution. A teuqierature of 212" 1">2 SULPHATE OF IRON. dissolves it immediately ; all organic substances decom- pose it ; and hence it is impossible to filter the solution. It is impossible to isolate this compound, for when the red solution is treated by an acid, as soon as the potash is saturated, oxygen is disengaged, and peroxide of iron precipi- tated. If the acid be in excess, it dissolves the peroxide, and gives rise to the formation of a persalt of iron. It is stated to possess a powerful dyeing principle." Protoxide of iron is very difficult to be obtained in an iso- lated state, on account of its great affinity for oxygen, which causes it to pass into the state of peroxide very rapidly. When an alkali is added to a protosalt of iron, the protoxide is precipitated as a hydrate of a grey colour, which, by expo- sure to the air, soon becomes peroxide of an ochery-red colour, as is seen almost daily in the dye-house during the dyeing of nankeen or buffs by a protosalt of iron or copperas. The goods are dipped into the sulphate of iron solution, and then passed through lime water; the lime combines with the acid, and leaves the hydrated protoxide precipitated within or upon the fibre ; the shade is then greenish, but a shght exposure peroxidizes the iron, and produces the nan- keen or buff. This property of the protoxide of iron of pass- ing into the peroxide, by its strong attraction for more oxygen- is beautifidly appUed in some of the operations of dyeing besides the one referred to, and which will be more fully described when treating of the blue vat. Sulphate of Iron, {green vitriol or cojyjyeras.) — Tliis salt is very easily prepared, merely by adding metalUc ii'on to sul- phuric acid, which has been diluted by 3 or 4 parts of water. The iron quickly dissolves, with rapid evolution of hydrogen gas. The reaction taking place may be thus represented : — Sulphuric acid -IqA"" ^ logen gas. Iron Fe ~"~ — — Sulphate of iron. When as much iron is dissolved as the acid will take, the solution is evaporated by heat, until a peUcle or thin skin appears on the surface. It is then set aside in a cool place,, and in a short time there is formed a quantity of green- coloured crystals of sulphate of iron. These crystals contain 7 propor- tions of water of crystallization, or in 100 parts g^ - SULPHATE OF IRON. 153 Sulphate of iron, Fe SO4 54*5 Water 455 100-0 If these crystals are heated a little above the boiling point of water, to 238° Fah., they part with all this water except one proportion or about 10 per cent. The salt also loses its green colour, and becomes white. The crystals of sulphate of iron require the following quantities of water to dissolve them : — gallon water at 50"* Fah. dissolves 6 lbs. crystals. dd" 7 75- Hi 109* 15 115° 22| 140° 26i 183° 27 194° 37 212° 33i- This table, which is of a similar character to tables of many other substances dissolving at a certain temperature, is inte- resting, and accounts for many of the circumstances occasionally observed in the dye-house — that sometimes the same stuff seems much more difficult to dissolve than at other times. It also shows why crystallization may occur much more rapidly at one time than at another. If we note the increase of heat and solubility, we will see how irregular they are : — 1st, an increase of 9° dissolves 2 16° .. 3 34° 4 6° 5 25° 6 43° 7 11° 8 18° 1 lb. 44 more than at 50° 59° 4 75° 7f 1 09° 3-V 1 1 5° 04 140° 183° H LESS than 194° Ten gallons water, at 194°, will dissolve 100 lbs. more copperas than the same quantity of water only 11° colder — a fact quite sufficient to account for many of the phenomena which exist in the practical operations of the dye-house. The sulphate of iron of commerce is not made by dissolving H 2 154 SULPHATE OF IROX. metallic iron in acid, which would be too expensive a process ; but from the sulphuretted ores of iron, (iron pyrites.) We have alread}', in treating of alum, given an account of the manufacture of a great quantity of the copperas of com- merce ; but there are numerous and extensive places for manufacturing this salt alone, where no alum is made. The operations are, however, nearly the same as those described for alum. Iron pyrites is a blsulphuret of iron, Fe S2; in 100 parts it has 52 of sulphur and 48 of iron. This compound, when obtained from the older geological formations, undergoes spontaneous decomposition by exposure to the air and mois- ture ; the sulphur combines with the oxygen of the air, and forms sulphiu'ous acid, which again, in the presence of water and oxide of iron, takes more oxygen, and becomes sul- phuric acid, which in turn combines with the iron. Gene- rally these pyrites ai'e made into large heaps, and set on fire, in the same manner as the alum-shale is treated in the pre- paratory process of the alum manufacture. This roasting causes the rapid oxidation of the sulphur, and consequent foiTnation of the sulphate of iron, which is aU dissolved out, by passing water through the heaps, and collecting it into tanks. Owing to the excess of sulphur over the iron, there is generally in the solution an excess of acid, with also some persalt of iron, and often small quantities of copper, which would be deleterious. To get rid of this, a quantity of old iron is put into the solution, which takes up the excess of acid at the same time that it precipitates the copper from the solution. Thus, Old iron Fe . —-__::==_- Sulphate of iron. Sulphate of copper.. Vr * P It reduces all the persulphate of iron to the state of protosul- phate: — Thus, ' Fe _=.-Protosulphate. Fe. ^^ Persulphate of iron ■{ SO4..- SO4.. SO4.. Old iron Fe... ^-Protosulphate. -Protosulphate. % SULPHATE OF IRON. 155 The solution is then evaporated to a proper density and crys- tallized. This method of adding old iron to produce the changes described, not being in all cases adopted, gives rise to some of the varieties of copperas found in the markets, concerning which there is much prejudice in the minds of dyers. M. Dumas describes the variations to the formation of a double salt of the proto and per sulphate, during the decom- position of the pyrites. M. Bansdorff {Becords of General Science) states, that there are three varieties of the protosul- phate of iron ; the first, greenish-blue, formed from an acid solution free from peroxide ; the second, dirty-green, from a neutral solution without peroxide ; and the last, emerald- green, from a solution impregnated with peroxide salt. This we know is consistent with experience, — that answering the description of his second variety being the best for general use ; but the selection of tliis particular quality of copperas has led dyers into a fatal prejudice. Sulphate of iron crystallized from a neutral solution, if kept any time, assumes a rusty appearance by absorbing oxygen, and forming a film of peroxide of iron. Now, good copperas having generally this appearance, especially on the surface of the cask when opened, dyers pretty generally entertain the opinion that it is to this redness it owes its superior quality. This, we need hardly say, is an erroneous opinion, concerning which, Mr. Parkes mentions in his " Chemical Essays," that some unprincipled dealers take the advantage to sprinkle lime on the top of the cask to peroxidize the surface, and make the dyers believe that they have got a lot of excellent old copperas. As copperas is generally judged of by the colovir, the worst coloured copperas has sometimes a solution of common salt or of lime sprinkled upon it to give it a dark tint ; but although this may deceive the eye, it does not improve its bad qualities. Copperas, crystallized from solutions of sulphate of alumina, will also have an acid reaction when used for some of the purposes of the dye-house, such as the blue vat, and may be the origin of the light-green coloured copperas, by giving much more water of crystallization than the other. The difference of value between tlie light-green watery-coloured crystal and the dark-green, is, by experience, about 14 per cent, in favour 156 SULPHATE OF IRON. of the latter. The effects of this will be noticed more fiilly under the blue vat. But these results, we believe, to be the reason why a practical dyer, in an excellent treatise upon his trade, states that there is a bisulphate of iron, and warns the trade against its use.* As this watery-looking blueish-green copperas, according to Bansdorff, crystallizes from an acid solution, it is pro- bable that the extra proportion of acid which is found in it, is owing to a portion of the mother liquor being mechani- cally combined with the crystals, but not forming an essential ingredient in the composition of the salt. And if the salt has been crystallized from sulphate of alumina, the excess of acid will be more apparent. The result of experience upon the relative value of the light-green watery-coloured copperas over the dark-green, or what are generally termed new and old, is as 21 to 24, or 100 lbs. of best old copperas is worth 114 lbs. of new light- green. In testing, there is always an excess of acid, but not in quantity anything like this difference. As the colour of the crystals of sulphate of iron depends upon the presence of water, may it not therefore be inferred that the difference of colour depends upon the proportion of water present in the crystals, which, if this be the case, wiU account for the different proportions of iron which we have often found in the same weight of the salt. It has been already noticed, that of the seven proportions of water which copperas contains, it loses six at 238°. We took 20 grains of each of the good and bad qualities of copperas, reduced them to coarse powder, and submitted them to a heat of between 305° and -100°, and taking the mean of several experiments, the bad copperas lost 1^ grains more than the other, or 7-^ per cent., a result Avhich agrees with the experience of the dyer. It being well known that copperas, being exposed to the air in a dry place, loses water. English copperas is considered superior to Scotch. The furmer is mostly made from pyrites, while the latter is made from alum shale, and is therefore very liable to contain small portions of sulphate of alumina ; and, being ci-ystallized from a strong solution of the sulphate of a salt of another metal, has every chance of being inferior. • Cooper's Treatise on Practical Dyeing. CHLORIDE OF IRON. 157 The presence of alumina may be detected by dissolving some of the salt in water, and boiling the solution, during which a few drops of nitric acid are added to peroxide the iron, which is known l^y the solution becoming a clear amber colour. Caustic potash is then added in considerable excess vmtil the solution is allcaline, and the whole is then boiled for some time, and passed through a filter upon which the peroxide of iron is retained. The solution con tarns the alu- mina. The potash is neutralized by sulphuric acid, and on adding ammonia to this solution, if alumina be present, a flocculent white precipitate is obtained. Other tests for alumina are given under that element. If ammonia be added to the iron precipitate retained upon the filter, the solution passing through wUl become blue, if copper be present. It is best to test for the presence of copper separately : this is done by dissolving the copperas, as described, peroxidizing with ^acid, adding ammonia instead of potash, and filtering: the slightest trace of copper will tinge the solution blue. Or it may be detected by dissolving a little of the crystals, and put- ting into the solution a piece of clean polished iron, such as the blade of a knife : when if any copper be present it will be preci- pitated upon the iron in a metallic state. The presence of zinc may be detected in copperas, by taking the ammoniacal solu- tion which has passed through the iron in testing for copper, and, if no copper be present, pass a stream of sulphuretted hy- drogen gas through the solution ; the zinc, if there be any present, will give a white precipitate. This metal is however very seldom found in copperas. The effects of the presence of these salts, in some of the operations where copperas is used, will be considered when treating of the blue vat. Magnesia is occasionally found in copperas, but its reactions are not deleterious. Chloride of Irou Iron is easUy dissolved in hydrochloric acid when treated in tlie same way as was described for dissolving the metal in sulphuric acid, and the product is chloride of irou. Hydrochloric (H Hydrogen gas. acid, (^1— --,_^ Iron, Fe T TT^^^^" — Chloride of iron. This salt crystallizes in green coloured crystals, but with difli- 158 ACETATE OF IRON. culty. The crystals are very soluble in water, and pass rapidly into the perslate. For some purposes of dyeing this salt could be used equally with copperas., but for others, such as the blue vat, it would not do so well. Moreover, the expense of making it, precludes its extensive use in the arts. Carbonate of Iron.— This salt, as we have already said, exists as an ore ; but it is easily prepared, by adding to a solution of copperas, a solution of carbonate of potash or soda. It is a whitish green coloured precipitate, and is obtained by double decomposition. Carbonate of (K ... --^^^ Sulphate of potash potash. (COg..--^^^,-'-^'''^ (solution.) Sulphate of iron. -, t^ *" --^ ^ , . c- '■ (i e. . . ■ ■ Carbonate of iron (precipitate.) This precipitate cannot be dried in the air without losing its carbonic acid and passing into the state of peroxide; but it is soluble in water impregnated with carbonic acid. This is the state in which iron is generally held in solution in spring waters. Acetate of Iron.— Acetic acid or A'inegar acts readily upon iron, dissolving it, and forming the acetate, which crystallizes in small green crystals, very rapidly acted upon by the air. This salt is much used in dyeing in the hquid state : it is knoA\Ti as iron hquor, and pyrohgnite of iron, from its being prepared on the large scale with crude wood vinegar. The acetate of iron may be prepared by mixing together acetate of lead and protosulphate of iron. The sulphate of lead is formed and falls to the bottom ; the acetate of iron remains in solu- tion. The pyrohgnite of iron is in general preferable. It is prepared by allo^ving iron to steep in pyroligneous acid (im- pure acetic acid) for several weeks. As this acid contains a quantity of pyrogenous oils and other impurities, it preserves the iron for a longer time in a state of protoxide than almost any other solvent available in the arts ; hence the decided preference given to it by practical men. We shall often have occasion to refer to this subject, as it is one which is too much neglected, and which produces many serious evils. It may, however, be in the mean time observed, that pyrohgnite of iron, used instead of copperas in dyeing black, gives a prefer- able shade of colour. NITKATE OF 1R0». 159 Tlie value of this solution may be taken hy eA^aporating a known weight to dryness, and burning the residue until ail organic matters are consumed, when there remains only the iron as a peroxide : every forty grains of the peroxide will be equal to ninety-six of the acetate of iron in the solution. The operation is very simple, and the per centage of acetate of iron in the solution known. The average of good iron liquor ranges about 13"5 per cent, of pure protoacetate of iron, the specific gravity being about 1-085 = 17^ Twaddell. The state of oxidation in which a metal exists, when used as a mordant, ought to be strictly attended to. Iron combines in the px'otostate with oxalic acid, tartaric acid, and indeed with all the acids, but these salts possess no peculiar advantages over those before described to warrant any extra expense in pi-eparing them. Persulphate of Iron.— Persalts of iron are also extensively used in the dye-house. The persulphate of iron may be easily prepared, by boiling a solution of copperas, to which a few drops of sulphuric acid have been added, and, while boiling, adding a very small portion of nitric acid, or any nitrate : red fumes are given oiF, and the solution becomes of a beautiful amber colour. It is then in the state of a persalt. Chlorate of pot- ash may be used instead of nitric acid or nitrates. The per- sulphate of iron might be advantageously used for many operations, and be cheaper than the nitrate of iron. Nitrate of Iron — This is the persalt of iron generally used in the dye-house. It is made by putting clean iron into nitric acid, by which it is very quickly dissolved. The iron ought to be added as long as the acid continues to dissolve it ; but cautiously, otherwise the action will be so violent as to cause it to boil over. When engaged in this process, care ought to be taken not to bi-eathe any of the fumes which come off, as they are very destructive to health. The reaction Avhich takes place between the acid and the iron may be expressed as in the table below — which we introduce by remarking, that in dissolving iron in sulphuric or hydrochloric acid, there is merely a substitution of the iron for the hydrogen (see page 32) ; but with nitric acid a different range of affini- ties takes place : the elements of the acid are not held to- gether so powerfully as those of sulphuric acid ; so that one 160 XITRATE OF IRON. proportion of the nitric acid is broken up, producing the fol- lowing arrangement : — One nitric NObH Binoxide of nitrogen. Two proportions iron 2 Fe. Water. 3 Water. Nitrate of iron. The binoxide of nitrogen is the gas passing off; but it in- stantly combines ■with more oxygen, and forms peroxide of nitrogen. The nitrate of iron alone dyes a buff or nankeen colour, which is probably the easiest dyed of any of the colours, and is, at the same time, very permanent. The process only re- quires that a little of this salt be put into water, and that the goods be immersed in the solution for a few minutes, then washed in clean water and dried. Passing them through a weak soap solution softens the goods, and gives clearness to the tint. But the particular use of this salt is for Prussian blue. The goods arc first dyed buif by the salt of iron, then thoroughly washed, and put into a very dilute solution of ferroprussiate of potash, made acid by a few drops of sulphuric acid ; they are washed from this in clean water, to which a little alum has been added. (This is only for light blues on cloth: but for dark blues, and for yarn, the proper methods will be given hereafter.) We have known many attempts made to substi- tute copperas for nitrate of iron in dyeing Prussian blue, but need hardly say they were unsuccessful. A A'ery little know- ledge of the nature of these salts would have told the experi- menters that protosalts of iron give only a greyish colour with yeUow prussiate of potash ; but, with red prnssiate of potash, copperas is a better mordant than nitrate of iron, as the red prussiate gives a dark blue with the protosalts, and only a greenish grey with the'persalts of iron. NITRATE OF IRON. 161 The preparation of rritrate of iron (killing iron) is ap- parently one of the most simple operations of the dye-house, as all that is required is to place metallic iron into nitric acid ; but the practical dyer often experiences difficulties which he cannot account for, and which alter materially his shades and colours. Sometimes, as we have already noticed, the iron seems not to be acted upon ; at another time the action is so rapid that theie is a difficulty in preventing the liquid boiling over. When the acid is a little diluted, and the iron is added in small pieces, the action is violent, and there is formed a brown turbid clay-looking solution. Co- lours dyed liy the iron in this state are never brilliant. We have seen solutions of this sort diluted largely with Avater, the brown mass allowed to settle, and the clear only used, but this is tedious, and not good after all. The best means of im- proving this mordant is to remove all metallic iron, add a little nitric acid, and apply heat. When the nitric acid is not diluted, and the iron dissolves freely, and when the acid is saturated with iron, if the re- maining metallic iron is not removed, it continues to dissolve by the reaction of the nitrate of iron upon it thus — f Fe .. — ^- Protonitrate. I Fe... ^ ^^"^ Protonitrate. . One part nitrate j -^^ «^^^°" I no':; lNOo____^ One part iron Fe... — — ^^^^~~^=^-~Protonitrate. This protonitrate rapidly imbibes oxygen, passes into the pernitrate, and, in so doing, liberates a portion of oxide of iron which collects at the bottom of the vessel, and accumu- lates so rapidly that the iron solution is soon converted into a brown paste. This can be avoided by taking out the iron when the acid is saturated, and before this deposit begins. The addition of a little acid and heat re-dissolve this oxide ; or a little sulphuric or hydrochloric acid also dissolves it, and with it forms an excellent mordant. A still more remarkable circumstance often occurs: the iron being placed in the acid, and action going on favourably, after a few hours, particularly if the weather be cold, the solution is observed to have a greenish yellow colour, and the vessel is 162 KITRATE OF IRON*. found to be half filled with crj-stals of a light yellow tint. Although these crystals, when dissolved in water, or the solu- tion above the crystals, may be used for dyeing, they give varieties of quality from the usual iron solution, which often seriously destroy the method of the dye-house. The true na- ture of the crystals is not well understood, and it is difficult to get at their examination, as they are very deliquescent, dissolve easily in water, and even in their own water of crystallization, by a slight elevation of temperature above summer heat. Wlien put upon blotting paper they are decomposed, and the paper imbibes much of the iron. We long thought that they were caused by the formation of ammonia in dissolving the ii'on, but experiments have failed to show the slightest trace of am- monia. The analysis of these crystals, by J. M. Ordway, gave 3 nitric acid, 1 peroxide iron, and 18 water = 3 NO5 + Fes O3 4- 18 HO. The same author has examined nitrates of iron of different qualities, and states that nitric acid combines de- finitely with various proportions of peroxide of iron and water, forming what he terms basic nitrates, varying from 3 acid, and 1 peroxide iron, to 3 acid, and 2, 3, 6, 8, 12, 15, 18, and 24 peroxide of iron, with various definite quantities of water, giving an interest to this salt of the highest sort, and amply accounting for the great difference experienced in its use for dyeing; and also for the ease with which peroxide of iron is fixed upon the fabric when put into this salt: the basic salt being decomposed, and a portion of the oxide of iron left upon or \snthin the fibre. There are many other phenomena observed in working with these salts, which we will yet have occasion to notice. Any other persalt of iron may be formed by adding am- monia, soda, or potash, to the nitrate of iron solution, so long as a precipitate is formed, washing the precipitate, by repeat- edly filhng the vessel which contains it with water, allowing it to settle, and decanting off the clear, then adding to the pre- cipitate the acid of which the salt is wanted. The application of heat assists the solution of the precipitate in the acid. By these means per acetate, per oxalate, per tartrate, ikc, may be obtained either for practical use or experiments. The following is the reaction of different substances upon the pro and jter salts of iron. Protosalis — Potash, soda, and ammonia give at first a grey- COBALT. 1{)3 white precipitate, passing into green, then bluish, and which, by exposure, finally becomes brown. Carbonates of these alkalis produce precipitates, which pass through the same changes as the alkalis themselves. Yellow prussiate of potash.... A grey-white precipitate, which, by exposure, becomes blue. Ked prussiate of potash An immediate dark-blue precipi- tate. Solution of galls A blue-black, not changed by standing. Per Salts* of Iron.— Alkalis, and carbonates of the alkalis, all produce dark-brown precipitates. Yellow prussiate of potash.... An immediate dark-blue precipi- tate. Red prussiate of potash No precipitate, but Ike solution becomes green. Solution of galls Black, passing to brown by standing. The difference between the action of red and yellow prus- siates will be remarked. Cobalt. (Co 29-5.) Cobalt generally occurs in nature in combination with ar- senic and sulphur, and accompanied by other metals. The mineral in which it occurs was long known to miners, and was called by them kobalds, or evil spirit of the mines, because its appearance often deceived them by giving a favourable im- pression of mines which turned out erroneous, the cobalt being taken for something else. Its distinct character as a metal was discovered in 1733. Its oxide has long been extensively used for giving a blue colour to glass and porcelain. As a metal it is brittle, of a reddish grey colour, and little more flexible than iron. Its has two oxides similar to iron. Protoxide, Co O Pex'oxide, Coj O;, But there is no persalt of cobalt known equivalent to the per- oxide. . . Cobalt is easily dissolved in either hydrochloric or nitnc 164 COBALT. acids, aud forms pink-coloured solutions which produce crys- tals of a beautiful red colour. Solutions of these salts form sympathetic inks. By writing upon clean paper with one of these solutions, the writing is invisible when dry; but by heating the paper before a fire, the writing becomes blue, and disappears again on cooling. If the heat applied be too strong, the writing becomes black and permanent, a significant fact to the dyer. Cobalt does not dissolve easily in sulphuric acid ; but a sulphate may be prepared by adding sulphuric acid to the oxide or carbonate, which is formed by adding a carbonate or caustic alkaU to the nitrate or hydrochlorate of cobalt. The suljjhate salt has also a pink colour, but is not so gene- rally used as the others. Salts of any of the acids may be pre- pared by dissolving the oxide or carbonate. They are all affected by heat in the manner described. Some of these salts might be very usefully employed in dyeing, were they obtained at a sufficiently low cost; but they are progressively becoming cheaper, and may therefore ere long be made available in the dye-house. A preparation of cobalt is used in bleaching, as sinalt blue. It is a compound of oxide of cobalt aud alumina, prepared by mixing a solution of salt of cobalt and alum, and precipitating them together by an alkaUne carbonate, as carbonate of soda, drying the precipitate, and subjecting it to a red heat. The process gives a beautiful blue mass, which is ground to an im- palpable powder, and mixed commonly with some carbonate of lime (chalk). Salts of cobalt give the following reactions with other substances: — Potash, soda, and ammonia... A green colour by a little exposure. Carbonates of the alkalis Reddish precipitates, which become blue by boiling. Phosphate of soda Blue precipitate. Yellow prussiate of potash ....Green precipitate, which changes to grey. Red prussiate of pota.sh Reddish-brown precipitate. Sulphurets of the alkalis Black precipitates. The slightest trace of cobalt may be detected by the bloAv- pipe, by fusing a little borax, and adding a little of the sub- stance suspected to contain cobalt: if it be really present, it com- municates to the borax a blue colour, more or less intense. NICKEL. 1 Go Nickel. (Ni 29-6.) Nickel occurs in nature combined witJi arsenic, iron, cobalt, and sulphur. It was discovered in 1751. Isolated, it is a silver-white metal, ductile and malleable, and requires a heat nearly equal to that of iron to melt it. It is much used in the arts for alloying with other metals. It is the principal constituent of German silver. Nickel combines with oxygen in two proportions. Protoxide Ni O. Peroxide Nij O3. There are no per salts of nickel equivalent to the peroxide known. Sulphate of Nickel.— Sulphuric acid dissolves nickel with difficulty. Wlien the sulphate is required, the acid is applied to the carbonate or oxide of the metal ; in this state it is easily dissolved, and forms a beautiful green-coloui-ed solution. Chloride of ixicitei.— HydrochloHc acid when dilute, dissolves nickel, and forms a chloride ; the solution is emerald green. Nitrate of Nickel — ^Nitric acid dissolves nickel easily, and may be called its true solvent : the product is the nitrate, of which the solution is also emerald green. All these salts crystallize. Carbonate of Nickel.— This salt is prepared by precipitating the nitrate by a carbonated alkali, as carbonate of soda or potash. It is a greenish coloured precipitate. The common means of preparing the salts of nickel is by dissolving in nitric acid, then precipitating and washing the precipitate; by adding the required acid the precipitate is dissolved. The acetate, or oxalate, or any of the other salts, may easily be prepared in this way. The use of any of these salts in the dye-house is very limited. Their solutions are precipitated as follows : — Alkalis An apple-green precipitate of hydrated oxide, insoluble in excess. Ammonia, in excess Blue solution. Carbonate of the alkalis Green precipitate. Yellow prussiate of potash... Greenish-white precipitate. Red prussiate of potash Yellow-green precipitate. Solution of galls No precipitate. Phosphate of soda White precipitate. Sulphuret of the alkalis Black precipitate. 166 ZINC. Zinc. (Zn 32-6.) Zinc was discovered in the sixteenth century. It is very abundant in nature, in combination with sulphur, and with carbonic acid. With the former, it is the ore called blende, or black jack ; with the latter, it is calamine. Zinc is a white metal with a shade of blue, brittle, and of a crystalline struc- ture. When heated from the boUing point of water to 300'', it is ductile, and admits of being rolled into sheets, in which state it has become a most useful metal in the arts. At a red heat it rises into vapour, and takes fire in air, burning with a white flame. It is much used along with copper for making the common alloy, known as brass. Zinc combines with oxygen in several proportions ; but the only one of its oxides which has been studied is the pro- toxide = Zn O. The salts found are the protosalts, equivalent to this oxide. Protoxide of zinc may be obtained either by burning the metal, or by precipitating it by an alkali from its acid solu- tions. It forms a white powder, which is soluble in all the caustic alkalis. Chloride of Zinc— Hydrochloric acid acts rapidly upon zinc, evolving hydrogen gas — thus Hydrochloric (H . Hydrogen aas. acid (Cl^_.^_^^ Zinc Zn ~~'~~--^- Chloride of zinc. It crystallizes in white crystals, which are vei-y deliquescent, and often used on account of this property for keeping sub- stances damp. It is even said to be employed by tobacconists for keeping snuff and tobacco moist, a dangerous and most reprehensible practice, if true. It is now very extensively used for soldering instead of rosin. Sulphate of Zinc — This Salt is easily prepared by acting upon zinc with sulphiiric acid slightly dUuted : the action is Sulphuric acid |H- ^Hydrogen gas. Zinc Zn... ' .Snlphntp of zinc. It crystallizes in white-coloured crystals, which contain seven proportions of water of crystallization, and dissolve in two CADMIUM. 1G7 and a-half times their weight of cold water. It is known in commerce as wldte vitriol, ivhite co2'>peras, and is produced in great quantities in the soldering of platinum vessels. Articles of this kind are soldered by the flame of the oxyhydrogen blowpipe, for which the hydrogen required, is prepared by zinc and sulphuric acid, and thus the sulphate becomes a product. Nitrate of Zinc. — This salt is easily prepared by acting upon the metal with nitric acid ; it is a crystalline salt, very deliquescent, but not much used. Acetates, oxalates, and salts of such milder acids, may be prepared either by digesting the metal in the acids, or by acting upon the oxide or carbonate found as a precipitate. The salts of zinc are not much used in the dye-house ; the precipitates formed from them are nearly all white ; but the sulphate is used in several operations, where its elements may act an important part without affecting the tint, as in the operations of dyeing chrome yellows, &c. It is also used by calico-printers in some of the operations of discharging. The salts of zinc act towards other substances as foUows : — Potash, soda, and ammonia... White precipitate, easily dis- solved in an excess of the alkali. Carbonates of the alkalis White precipitate, not soluble in excess, but soluble in caustic alkalis. Yellow prussiate of potash White precipitate. Red prussiate of potash Yellowish-red precipitate; fades in the air. Solution of galls No precipitate. Sulphurets of alkalis White precipitate. Chromic acid A purple-brown precipitate. Cadmidm. (Cd 56.) This metal was discovered in 1818 ; it is very rare, found only in small quantities, and sometimes combined with zinc. The metal somewhat resembles tin in coloxu- ; it is also soft and flexible, and makes a crackling noise when bent. It melts easily, and passes off as a gas at a heat of about 600°. It combines with oxygen in equal proportions, forming the 168 COPPER. protoxide, (Cd 0,) which has an orange colour, and is easily obtained by burning the metal in air, or by precipitation from acid solution by a caustic alkali. Prepared in this way, it is a white hydrate, and has one proportion of water combined with it. This oxide is soluble in ammonia, but not in soda or potash. Cadmium is acted upon like zinc, both by sulphuric and hydrochloric acids ; and forms crystallizable salts. Nitric acid acts readily upon the metal to form the nitrate, which is crj'Stallized with difficulty. All these salts give white- coloured crystals. The salts of the milder acids, as the acetate, the oxalate, &c., may be obtained by dissolving the precipitated oxide or carbonate in the particular acid. Potash and soda, and their carbonates, give white preci- pitates, not soluble in excess. Ammonia — white precipitate, soluble in excess. (The oxide and carbonate, precipitated by the fixed alkalis, are all soluble in ammonia.) Yellow prussiate of potash... "^AHiite precipitate. Red prussiate of potash Yellow precipitate. Solution of galls No precipitate. Sulphurets of the alkaUs Beautiful yellow precipitate. Copper. (Cu 317.) This is a very abundant and useful metal, and was known in the earliest times. It is found in nature in great quanti- ties, in combination with sulphur, oxygen, and carbonic acid ; and is separated from these combinations by various processes of roasting and fusing. Copper is of a red colour ; is very malleable and ductile, and only inferior to iron in tenacity. It requires a heat of about 1900° to fu.-^e it. It combines with oxygen in two proportions, namely — Suboxide or dinoxide Ciio 0. Protoxide Cu 0. The suboxide is of a reddish brown colour, which is not changed by the air. If acted upon by dilute acids, a proto- salt is formed, and in strong hydrochloric acid there is formed a subchloride = Cu2 CI. This is a greenish or nearly colour- SULPHATE OF COPPER. 169 less solution, which undergoes deccmposition by dilution ; and if precipitated by an alkali, oxygen is absorbed, and protoxide is formed. If a portion of suboxide be put into a stoppered bottle with ammonia, it is dissolved, and the solution is colourless at first, but by admitting air it is oxidised, and the solution becomes blue. Protoxide of Copper is black, and is formed upon the sur- face of metallic copper when brought to a red heat and ex- posed to the air ; or it may be obtained by exposing the car- bonate, acetate, or nitrate, to a red heat. Alkalis added to solutions of copper precipitate the oxide as a hydrate of a blue colour, which becomes black by boiling. Oxide of copper dissolves readily in ammonia, and gives a deep blue-coloured solution. Copper <;ombmes with nearly all the acids, and the salts produced are generally blue or green. Sulphuric acid, when cold, does not dissolve copper, but at a boiling heat it acts upon it readily, a portion of the acid suffering decomposition, as under : — Sulphurous acid gas. One proportion of sulphuric acid decomposed ,... -AYater. One proportion of suliihuricacid... ^ H... — '^ ■ .-^.,^^^ ^^ Water. One prop, of copper ...Cu _rii- Sulphate of copper. Saiphnte of Copper yields deep blue crystals, containing five proportions of water, four of which are given off by heating the crystals to 212", at which temperature they become white. They are soluble in four times their weight of cold water, and in twice their weight of boiling water. The salt is prepared on the large scale, in the same manner as the sulphate of iron ; that is, from the sulphurets of the metal. Great quantities of it are produced by the metal workers in Birming- ham and elsewhere, in their cleaning and bronzing operations, which are effected by the action of acids upon copper or its alloys. As obtained in commerce, it is very impure, and is often contaminated with ii-on, a very injurious ingredient for I 170 CHLORIDE OF COPPER. most of the purposes to which this salt is applied in the dye- house. This impurity can be detected by dissolving a little of the salt in pure water, and adding ammonia in excess, on filtering through paper, and washing the filter, the iron will be obtained as a brown precipitate of peroxide. K the salt con- tains much iron, it ought to be rejected. Zinc is often present, but it has no deleterious efiects further than in lessening the value of the salt. Sulphate of copper is known in com- merce and in the dye-house as blue vitriol, Roman vitriol, and blue-stone. Nitrate of Copper.— Nitric acid dissolves copper easily, form- ing the nitrate ; the action is similar to that by which the nitrate of iron is produced. N O O 1 proportion of nit- J O ric acid ] O O 3 proportions of nitric acid ( 3 H proportions of copper Binoxide of nitrogen. O H (3X0 Water. 3 Water. 3 Nitrate of copper. Nitrate of copper crystallizes in deep blue crystals, which dehquesce in the air, and are accordingly very soluble in water. The salt acts rapidly upon tia ; if a small crystal be crushed, slightly moistened, and wrapped in tinfoil, combustion takes place by the rapid oxidation of the tin. The salts of copper are very useful for oxidizing vegetable matters in solution, and are often used for that purpose in the dye-house. Chloride of Copper is made by digesting oxide of copper in hydrochloric acid, by which a double decomposition t^es place as follows : — fH Hydrochloric acid -< p. Oxide of copper ■< p Water. Chloride of copper. LEAD. 171 Tho solution of this salt is green, but it crystallizes from this solution in blue-coloured crystals. Acetate of Copper (verdigris) is prepared by exposing sheets of copper to the action of acetic acid {vinegar^') sometimes in solution, but more commonly in vapour. The salt is obtained in beautifiil dark- green crystals ; in this state it is a subace- tate, having one acetic acid to two of copper. Acetic acid combines with copper in various proportions, and the verdigris of commerce is often composed of several salts, not by adul- teration, but formed in the process of manufacture. Oxalate of Copper is of a light-green colour, and is pre- pared by digestmg oxide of copper in oxalic acid. Arseniate and the Arsenite of Copper are salts of a light- green colour, formed during the dyeing of arsenic greens — blue-stone sages or Scheele's green — for which the goods are passed through strong solutions of arsenic and copper, and alkalis. That these greens are still dyed argues little for mercantile morality. This process of dyeing is dangerous, and the >vinding of the yarns, and other operations that follow, are more so, and produce much serious mischief to the operatives. Copper salts produce the following reactions : — Potash and soda Greenish -blue precipitates, be- come black mth boiling. Ammonia Deep-blue liquid. Carbonate of alkalis Green precipitate. Yellow prussiate of potash. ..Dark-brown precipitate. Red prussjate of potash Yellow-green precipitate. Solution of galls Brown precipitate, Sulphurets of alkalis Black precipitates. Lead. (Pb 103-7.) This metal exists abundantly in nature, mostly in combina- tion with sulphur, from which it is separated by exposing the ore to a gentle heat; the sulphur becomes oxidized, and passes off as sulphurous acid, and the lead melts, and runs off by a channel prepared for it. Lead has a blueish-grey colour, is soft, and very malleable ; 172 LEAD. it does not oxidate readily in the air, except at the water line, when it is partially immersed in that fluid, and more rapidly still when the water is soft and pure. Hence lead vessels should not be used to hold water for domestic use, as the oxides of lead are all very poisonous. Lead combines with oxygen in various proportions. Suboxide of L.ead is the greyish-blue crust, formed upon the surface of lead exposed to the air, and consists of two equivalents of lead and one of oxygen, Pb, O. It may be prepared artificially, by burning oxalate of lead in a retort ; the suboxide remains as a dark-grey powder. Protoxide of l.ead consists of lead and oxygen in equal pro- portions, = Pb O. It may be obtained by exposing metallic lead at a red heat to a current of air : the oxygen of the air combines with the lead, and forms with it a semi-fluid mass. As it cools, it crystallizes in concretions of a greenish-yellow colour. It is obtained on the large scale by cupellation — a process effusion to which lead is subjected in the process of extracting the small admixture of silver it commonly contains. The process is conducted as follows : — A quantity of lead is put upon a fiat vessel made of bone ashes (burned bones) placed in a furnace ; when the lead is melted, a strong current of air is blown upon the surface, which rapidly oxidates the metal ; at the same time, the force of the current blows the oxide oflT, which runs over the side of the vessel like water. The silver, not being capable of oxidation, by this means is ultimately left pure upon the bottom of the vessel. Lead is continually added, until the silver remaining nearly fills this bone-ash vessel, which is technically termed a cupel. When the protoxide of lead is kept for some time, it falls into a brick-red scaly crystalline powder, known in commerce as litharge. This is the principal oxide from which the salts of lead are prepared for the dye-house ; but it is generally to some extent contaminated with iron, copper, and red lead, and is also subject to much intentional adulteration. Litharge, of good quality, possesses a crystalline lustre, and is completely soluble by digestion in nitric acid. The amount of advdtera- tion, if it be brick-dust, may thus be ascertained, as it remains insoluble, and by adding ammonia to the solution, the lead is precipitated; if iron be present, the precipitate will have a brown colour ; if copper, the solution will be blue, but none of these ACETATE OF LEAD. 173 are deleterious to the dye. The protoxide of lead is also obtained by adding a caustic alkali to a solution of a salt of lead ; the oxide is precipitated as a white powder, soluble in un excess of caustic alkali, and also in solutions of the alkaline earths, as lime, with which it forms compounds more or less soluble. Peroxide of L.ead coDsists of two equivalents of oxygen and one of lead = Pb O^. It may be obtained by digesting litharge in a boihng solution of chloride of lime, {bleaching powder.) It is a powder of a dark-brown colour, and is not used for preparing any salts of lead. What is termed the fourth oxide of lead, consists of Pbg O4 ; but this is not generally considered to be a direct combination of oxygen and lead in these proportions, but a mixture of the second and third oxide just described, in the proportion of two of the protoxide to one of the peroxide, 2 Pb O + Pb Oj, which may be separated by digestion in dilute nitric acid : the acid combining with the protoxide, and liberating the per- oxide which remains undissolved. Whether the view we have stated of its constitution be correct or not, is not very important, as this oxide is not much used in the dye-house. It is known in commerce as red lead or minium. Carbouate of f/ead ( WMte Lead) is prepared on the large scale by exposing thin sheets of lead to the vapours of vinegar : the acid is decomposed and forms carbonic acid, which com- bines with the lead. This salt is sometimes used for preparing salts of lead, by dissolving it in the acid the salt of which is required. ivitraie of Lead is prepared by dissolving litharge or metallic lead, in nitric acid, and evaporating the solution, which leaves a crystalline mass, the crystals of which are white and generally opaque, and soluble in ~^ parts of cold water. The nitrate of lead, when prepared in this way, con- tains one proportion of oxide, and one of nitric acid ; but by boiling the salt for some time over litharge, the acid combines with two, three, or even sLx proportions of lead, forming what are termed basic salts. This fact has been known to practical dyers for many years, and is made available for the purpose of dyeing orange colour and dark shades of yellow. Acetate of Lead {Sugar of Lead) may be obtained by ex- posing metaUic lead to the action of acetic acid, either as a 174 ACETATE OF LEAD. liquid or as a vapour, and to the air ; a portion of the acid is decomposed, and carbonate of lead is formed, which is then easily decomposed by another portion of the acid ; the latter combining with the lead, forms acetate of lead, and the car- bonic acid is evolved. Acetate of lead is prepared extensively by a variety of modes. The first is by immersing a number of sheets of lead in vinegar, so arranged that the ixppermost sheets are exposed to the action of the air. When they become covered with the crust of carbonate, they are shifted to the bottom of the vat, where the acid decomposes the carbonate and forms acetate, while the succeeding sheets are being exposed to the same course of action. Another process is to expose sheets of lead to the vapour of vinegar : the carbonate formed is collected and immersed in strong vinegar. In both these processes, when the acid appears to be saturated, or when it ceases to decompose the carbonate, the solution is drawn into proper vessels and allowed to crystallize. Another process is to dissolve htharge in strong vinegar to saturation. This is done by gradually sprinkling the litharge in a vessel of vinegar subjected to a boihng heat ; the \T.negar is constantly stirred, to prevent the adhesion of the Utharge to the bottom and sides of the boiler. When a sufficient quantity is dissolved, a moderate quantity of cold water is poured into the solution, reducing it a httle below the boihng point, and it is allowed to settle ; the clear fluid is then drawn off into a separate vessel and allowed to crystaUize. If the solution be coloured, it is whitened by filtration through bone black. Common unrectified wood vinegeir or pyroUgneous acid, is much used for the preparation of acetate of lead for the dye- work. It is known in the dye-house by the appellation of brown sugar. Basic salts, or subacetates, are made by boiling common acetate of lead vfith litharge. The tribasic acetate, a com- bination of three of lead to one of acid, is the best salt for dyeing orange, deep yellow, and amber. It is prepared in the dye-house by boiling a solution of sugar of lead with litharge, and adding to this a httle lime. The proportions, however, vary in different dye-houses. Those which ought to be employed to produce the tribasic acetate, are six parts of crystallized ACETATE OF LEAD. 175 acetate of lead, eight of litharge, and thirty of water, boiled till the litharge is dissolved. The addition of small quantities of lime causes a loss, as the lime combines with part of the acetic acid forming acetate of lime, which, if these proportions have been used, would prevent some of the litharge from being dissolved. If the mixture be not long enough boiled, or if the proportion of litharge be too small, the addition of lime insures the conversion of the acetate of lead into the tribasic state, though it is to be observed, that this will be at the expense of a portion of the lead intended for producing the colour. We have experienced much annoyance from this source ; and it is well known in the trade, that when the lead is hastily prepared for orange, it is a cause of great anxiety, and the colour obtained is frequently defective. As this is rather an important point in the economy of the dye-house, we shall explain our view of the matter. If the proportions, recommended above, be used, the following is the result : and we must bear in mind that while the oxide of lead forms the basis of the dye, the acid merely holds the lead in solution. Tlie six pounds of acetate of lead are composed of 4 lbs. oxide of lead, and 2 lbs. acetic acid ; but when the 8 lbs. of litharge are dissolved, or, as dyers say, taken up, the tribasic salt will consist of 12 lbs. of oxide of lead and 2 lbs. of acetic acid; that is, every ounce of acid holds in solution 12 ounces of oxide of lead. Now, if a little lime, as we have often remarked, be put in along with the litharge, the result will be as fol- lows : Suppose that 50 lbs. of cotton are to be dyed orange, and that it consumed the 6 lbs. acetate of lead prepared as now stated, to give it a good colour. If 1^ ounces of lime be mixed in, they will combine with 3 ounces of acid: in this way 36 ounces of oxide of lead are not taken up, and are therefore ineffective in the production of the colour ; while at the end of the process, the dyer is surprised to find his colour poor. We may notice that lead in the basic state is not held in combination by a very great affinity, and thus a very Uttle counteractive influence precipitates it. The presence of sulphates or carbonates in the water, which almost all water contains, precipitates the lead ; lience the reason that often, when the clear acetate solution is poured into a tub of water, the contents become milk-white by the fonnation of an insoluble carbonate or sulphate. The lead is all lost for the time, as it is rendered insoluble and 176 TESTING SALTS OF LEAD. useless as a dye. Every ounce of carbonate renders useless five ounces of lead. The softest water should be used for the lead solution, as, for example, the condensed steam from an engine. When much lime is added, it dissolves the lead, and forms a mordant quite as good, if not superior, to that described, as we will have occasion more fully to indicate when we come to treat of the processes for dyeing oranges and yellows. Alka- line salts of lead and oxide of lead dissolved in alkalis, are now becoming more generally used than the acid salts, and are su- perior for most purposes. Sulphate of licad. — Sulphuric acid, when hot and concen- trated, dissolves lead ; but the sulphate is precipitated by dilution. It is an insoluble white powder, easily formed by adding a solution of a soluble sulphate, as that of an alkali, to any salt of lead. Chloride of liead. — Lead dissolves slowly in hydrochloric acid, forming a chloride which requires 135 times its weight of cold water to dissolve it. Several sub-chlorides of lead are also capable of being foriped, but they are nearly all insoluble in water. All the soluble salts of lead are poisonous, and have a sweetish taste, except the sulphate, which is inert. Their re- actions with other substances are as follows : — Soda and potash, give White precipitates, soluble in excess. Lime White precipitate, soluble in excess. Ammonia Wliite precipitate, insoluble in excess. Carbonates of alkalis White precipitates, insoluble in ex- cess, but soluble in caustic alkali. Oxalic acid White precipitate. YeUowprussiate of potash. ^Vhite precipitate. Red prussiate of potash... No precipitate. Solution of galls White precipitate. Chromates of potash Yellow precipitates. Iodide of potassium Yellow precipitate. Sulphurets of the alkalis.. Black precipitates. Testing the Talue of JLcad Salts — A very simple method of testing the value of salts of lead, that is, of ascertaining the quantity of lead in a solution, is to dissolve say 10 grains of bichromate of potash (rec? chrome) in hot water, and put BISMDTH. 177 the solution into a tall glass jar ; then take a given weight, say 100 grains of the lead salt, whether acetate or nitrate, and dissolve in one measui-e (by the alkaliraeter) of water ; add this gradually to the chrome solution until the liquor above the precipitate becomes colourless, or imtil a drop of the liquor added to a drop of the lead solution on a glass plate is not turned yellow. The number of graduations taken to ertect this is noted ; then, as every 148-6 of bichromate of potash is equal to 379 J: acetate of lead, or 330 nitrate of lead, the quantity required by the 10 grains chrome is easily calculated — being for acetate 25-6, and for nitrate 23 grains. All the solution required above these measures will indicate imp'orities. The average of Commercial nitrate requires 24- grains. " white sugar, 27' " " brown sugar, 28" " The quantity of lead in a solution is tested in the same way. Bismuth (Bi 213.) This metal occurs in nature in the metallic state, and also in combination with other substances. When found in the metaUic state, it is separated from the earths, through which it is diffused, by a melting heat — the metal sinking to the bot- tom of the crucible, and the earthy matters floating on the surface. It is a white metal, with a reddish hue, very crystalline in structure, volatilizes at a red heat, and burns in the air with a pale blue flame, forming oxide of bismuth. The metal does not tarnish by exposure to the air. It coni- bines with oxygen in several proportions. The protox- ide ^ Bi O is tbrmed by combustion, as stated, and is of a straw-yellow colour. There is also a suboxide = B'u O, and a peroxide = Bi., O3, but these oxides liave no corresponding salts. Sulphate of bismuth may be prepared by dissolving the oxide in concentrated sulphuric acid. Chloride of bismuth by dissolving in hydrochloric acid ; these salts are decomposed by dilution. Nitrate of Bismnth. — Nitric acid dissolves bismuth easily, i2 178 inr. forming the nitrat€, ■which crystallizes in beatitiftil white crys- tals. This salt is also decomposed by water ; indeed, all the neutral salts of bismuth are precipitated by adding water to their solutions, there being formed salts with the oxides. The action of re-agents upon the solutions of bismuth is as follows : — Potash, soda, and ammonia... "White precipitates, not soluble in excess. Carbonates of the alkalis White precipitates, not soluble in pxcess. excess. Yellow prussiate of potash ...White precipitate. Red prussiate of potash Pale yellow precipitate. Solution of galls Orange-yellow precipitate. Iodide of potassium Brown precipitate. Chromates of potash Yellow precipitates. Sulphurets of the alkalis Black precipitates. Tin (Sn 59.) This metal has nearly the colour and lustre of silver ; it is one of the few metals which were known to man at a yery early period of his history, and was extensively used in all countries, both east and west, having any pretensions to civil- ization. This was probably owing to the ores of the metal being easily reduced to the metaUic state, these being in general oxides; so that by merely fusing them with carbonaceous mat- ter, such as wood or coal, which combines with the oxygen, the metal is fused, and sinks in the melted state to the bottom of the fiimace. The principal localities for obtaining tin, are Cornwall in England, Bohemia, Mexico, and the East Indies ; in the former coxmtry, the metal has been wrought for many ages, and may almost be said to be the first nucleus of civilization in this country, as it formed the great mart where the civilized and commercial Phoenicians obtained the tin which was so abundantly used by them. The ore is found in Cornwall both in veins traversing the primary rocks, and in small rounded grains in the neigh- bourhood of these rocks, imbedded in what geologists term the alluvial deposit, signifying the deposit formed by the washing Tix. 179 away of the fragments of the primary rocks with water. This gives the purest tin, and is distinguished by the name of stream tin. The ore obtained from the veins is gene- rally contaminated with other metals, such as iron, copper, arsenic, and the hke, but is partially piarified by liquation, that is, by heating the mass to the melting point of tin, which melts out and leaves the others. Several other operations of refining follow this, which need not be detailed; but there are always some few of the impurities remaining in a portion of the tin. That portion which contains these impurities, is termed block tin. The pure grain tin is heated till it becomes brittle, and is then let fall from a height, which splits it into small bars or prisms, and in this state it is found in commerce. These bars in bending, make a peculiar crackling noise, and become heated ; phenomena probably owing to the separating of their parts, and the sudden fracture caused by bending. Tin is very extensively used in dyeing and printing both cotton and woollen. Its introduction as a mordant may be considered as forming an era in the art of dyeing, and like many other important improvements in this art, was the result of accident, an account of which is given by BerthoUet as follows: — "A little while after the cochineal became known in Europe, the scarlet process by means of the solution of tin was discovered. It is stated that about the year 1630, Cor- nelius Drebbel observed by an accidental mixture, the bril- liancy which the solution of tin gave to the infusion of cochi- neal. He communicated his observation to his son-in-law, Kuffelar, who was a dyer at Leyden. He soon improved the process, kept it a secret in his workshop, and brought into vogue the colour which bore his name." Soon afterwards, a German chemist found out the pro- cess of dyeing scarlet by means of the solution of tin. He brought his secret to London in 1643; it became known to others, was soon afterwards diffused over Europe, and its applications became more extended, as whenever a new dye drug was introduced into the art, the solution of tin was uni- versally appUed, by which means it became a standard mor- dant for the various dyewoods, such as logwood, Brazil wood, and the like. Copper boilers used for dyeing woollen and silks, have generally a part covered with or made of tin, which is in- 180 PROTOCHLORIDE OF TIN. tended to prevent the acid mordant from acting upon the copper, and this it does, by a galvanic action, the tin being slowly acted upon, while the copper is protected. Tin combines with oxygen in three different proportions — Protoxide Sn O. Sesquioxide Sn2 Og. Peroxide Sn O2. There are salts of tin corresponding to these oxides, all more or less useful in dyeing. Protoxide of Tin is formed by precipitation from a solu- tion of the protochloride of tin by carbonate of potash or soda. It is obtained as a white powder, which is a hydrate of the oxide, and which, if heated to 176°, loses its water of com- bination and becomes black, and may be kept in this state ; but if brought to a red heat, or into contact with a red hot body, it takes fire, and in burning passes into the state of peroxide. The white hydrated oxide is easily dissolved in acids, and also in solutions of the alkalis, but these alka- line solutions are not permanent: for if diluted with water, a portion of the tin is precipitated, and another portion passes into the state of peroxide. Also, when brought into contact with other oxides which yield their oxygen freely, such as perox- ide of iron, a reaction takes place : the iron is reduced to a lower state of oxidation, and the tin is raised to a higher. These reactions and properties are taken advantage of in many of the operations in dyeing. The protoxide of tin and its protosalts all come under the denomination of stanous salts: and it may be remarked of them, as a general characteristic, that they all absorb oxygen from the air by exposure. Protochloride of Tin, {Salts of Tin.) — This salt is prepared by dissolving tin in strong hydrochloric acid, with the assist- ance of heat, the solution evaporating and crystallizing in the ordinary way. The crystals were formerly said to con- tain three proportions of water, about 22 per cent. ; but according to a recent investigation by Dr. Penney, they contain only two proportions. The crystals dissolve in a small portion of water ; but if put into a large quantity, the whole becomes milky, and a white powder separates, which is an oxychloride of tin. A complete and clear TARTRATE OF POTASH AND TIN. 181 solution of salts of tin in water cannot be retained for any length of time on account of the great attraction which this salt has for oxygen. A little hydrochloric acid put into the water, however, has the effect of greatly retard- ing, and, indeed, of almost wholly preventing this decompo- sition. In establishments where the dyers prepare their own salts of tin, they do not crystallize it, and as there is nearly always an excess of acid, some of the phenomena mentioned may not have been observed. On adding potash to salts of protochloride of tin, a double salt is formed of chloride of tin and chloride of potassium, which may be crystallized. Protosuipbatc of Tin. — Sulphuric acid dissolves tin slowly, and forms a thin pasty-looking mass, which, by evaporation, yields crystals. This salt is not used in the dye-house ; it is, indeed, immediately decomposed by aqueous dilution. Protoiiiii-aie of Tin— Protoxide of tin dissolves easily in dilute nitric acid, but it cannot be concentrated, from its Ua- bility to pass into the state of peroxide. When nitric acid, of specific gravity 1"114 = 23 of Twaddell, Ls poured upon the metal, it dissolves it rapidly, and much heat is evolved, which ought to be kept down by placing the vessel containing the acid in cold water. If this be properly done, a protonitrate of tin is formed, the action being Nitric acid... /Hv -^^Hydrogen gas. \NOe. Tin ..- Sn.. Nitrate of tin. But should the heat be fdlowed to rise too high, the nitric acid is also decomposed, and the tin passes into a higher state of oxidation. Also, if the action is very rapid, ammonia is formed between the hydrogen and nitrogen, and consequently a double salt of tin and ammonia ; but the greater proportion of the tin is precipitated as a white pasty mass of peroxide. Tartrate of Potasii and Tin is prepared by dissolving pro- toxide of tin in bitartrate of potash, {tartar, or cream of tartar.) This forms a very soluble salt, occasionally used in dyeing wooUens; but in this case the tartar is added to the salts of tin. A combination of the protoxide of tin, arsenic, and soda 182 PEROXIDE OF TIN. has recently been patented as a salt in calico-printing, under the name of Stand- Arsenite of Soda. Dentoxide, or Sesqaioxide of Tin = Sn2 O3, Can be prepared by adding to a saturated solution of protochloride of tin some newly-precipitated peroxide of iron : a double decomposition takes place as follows : — 2 proportions proto- T 2 CI . —-^ 2 Protochloride of chloride of tin.... \ 2 Sn _ ^-"""^ iron in solution. 1 proportion of per- J 2 Fe "^~~~~--~~.^^^^^ Sesquioxide of tin oxide of iron \3 O.. — — — ^ precipitated. Strong hydrochloric acid dissolves this oxide, and forms with it a sesquichloride, thus : — 1 Sesquioxide of tin |^ ^^- ~^::^^ ^ ^''*^^'" 3 Hydrochloric acid \\ JJ" " '^^^'^^IlZ:^^ Sesquichloride of "^ (3 C/1..- — ■ tm. The other salts corresponding to this oxide have not been examined ; but the distinctive character of the oxide itself may be made evident by the two following reactions : — Ammonia dissolves this oxide, but does not dissolve the protoxide ; and hydrochloric acid dissolves this oxide, but does not dissolve the peroxide. There can be little doubt but that an investigation into the sesquioxide and its salts would explain many of the hitherto unexplained phenomeoa of dyeing ; and that it is higlily probable the formation of salts of this class play a considerable part in many dyeing operations ; such as those processes in which chloride of tin is mixed with pernitrate of iron, as for royal blues, 244 VEGETABLE SUBSTANCES. the nature of the dyeing agent, which will be explained in its proper place. Speaking of vegetable green, Berthollet says, " the green of plants is undoubtedly produced by a homoge- neous substance, in the same way as the greater number of hues which exist in nature. This coloxir owes, then, its origin sometimes to simple rays, and sometimes to a union of differ- ent rays ; and some other colours are in the same predica- ment. Were the gi'een of plants due to two substances, one of which is yellow and the other blue, it would be extraordi- nary if we could not separate them, or at least change their proportions by some solvent." This idea of Berthollet, that the green of plants is a distinct substance, existing in the plant, has since been verified. It is obtained by bruising green leaves into a pulp with water, pressing out all the liquid, and boiling the dry pulp in alcohol : when the alcohol is evapo- rated, there remains a deep green matter, which, by digesting in water, is dissolved, and freed from a little brown-colouring matter with Avhich it was mixed. This substance has been named chlorojyhyllite. The formation of the chlorophyllite seems to depend entirely upon the action of the solar rays. " It is known that the function of the leaves, and other green parts of plants, is to absorb carbonic acid, and, with the aid of light and moisture, to appropriate its carbon. These processes are continually in operation : they commence with the forma- tion of the leaves, and do not cease with their perfect develop- ment." But when light is absent, or, during the night, the decomposition of carbonic acid does not proceed : it is evident then that a plant kept always excluded from the light, must have a difference in its composition. " No one can have failed to observe the difference between vegetables thriving in the full enjoyment of light, and those which grow in obscure situations, or which are entirely deprived of its agency: the former are of brilliant tints; the latter dingy and white. Nu- merous familiar instances might be cited, especially among our esculent vegetables: the shoots of a potato produced in a dark cellar are white, straggUng, and differently formed from those which the plant exhibits under its usual circumstances of growth. Celery is cultivated for the table by carefiilly ex- cluding the influence of hght upon its stem : this is effected by heaping the soil upon it, so as entu-ely to screen it from the solar rays ; but if suffered to grow in the ordinary way, it soon COLOURING MATTERS. 245 alters its aspect, throws out abundant shoots and leaves, and, instead of remaining white and of little taste, acquires a deep- green colour, and a peculiarly bitter and nauseous flavour. The heart of the common cabbage is another illustration, and the rosy-coloured aspect of the sides of fruit is referable to the same cause. Changes yet more remarkable have been dis- covered in plants vegetating entirely without exposure to light. In visiting a coal-pit. Professor Robinson found a plant with a large white foUage, the form and appearance of which were quite new to him : it was left at the mouth of the pit, when the subterranean leaves died away, and common tansy sprung from the root-s." * Some very curious and interesting results have been ob- tained by Mr. Hunt, and others, respecting the effects of the different rays of light upon vegetable substances, all going to prove the great influence exerted by that agent over the vege- table kingdom, and that to it we are indebted for the beauty of our fields and gardens. From these facts we see that the green colour of vegetables is owing to a peculiar approximate element existing in the vegetable, not invariably, nor altogether essential to the plant, but depending upon circumstances ; these circumstances being at the same time the best for the health and existence of the plant. This colour differs from the other colours of vegetables in the time of its appearing. Flowers of plants do not appear till the plant has reached a certain state of matiu-ity ; but whenever a plant rises above the soil, it immediately begins to assume the green hue, and this hue is continued till the object of the leaves is completed. When a chemical change takes place, the green passes away, and another colour, red- dish-yellow, takes its place. These changes are effected in different degrees, and in different lengths of time, just accord- ing as the leaves have the property of absorbing oxygen gas. Those leaves which continue longest green absorb oxygen slowest. The leaves of the holly will only absorb a small fraction of oxygen, in the same time that the leaves of the poplar and beech will absorb eight or nine times their bulk. These last are remarkable for the rapidity and ease with which the colour of their leaves changes. That leaves do absorb oxygen gas when they change colour in autumn, and * Brande's Manual of Chemistn-. 246 VEGETABLE SUBSTANCES. that it is owing to the absorption of this gas, may be verified by placing some green leaves of the poplar, the beech, and the holly under the receiver of an air-pump, and dry them thoroughly, keeping them excluded from light ; when taken out, wet them with water, and place them immediately under a glass globe ftdl of oxygen gas, when they will change colour ; and it will be found that the change of colour is just in proportion to the quantity of oxygen each absorbs. The consequence of this absorption is the formation of an acid, in accordance with the law mentioned before. This acid changes the chlorophyllite, or green principle, from green to yellow, and then to a reddish hue. If we treat green leaves with an acid, the same changes of colour take place, and if we macerate a red leaf in potash it becomes green. The green of leaves, and the colours of flowers, are common to all vegetables under the influence of light ; but there are a number of colouring substances in vegetables which are pecu- liar to certain orders, and which exist as proximate elements sometimes in the leaves, in the woody part, in the juice, in the bark, in the flower, ia the seeds, and in the roots. Several of these have been made subservient to our use in the art of dyeing, and will be noticed separately. Tlie various and beautiful colours of flowers are produced by a somewhat different process from that of the green of the leaves, in so far as they do not appear until the plant has attained a certain state of maturity. " The leaves of the plant being fully developed, they take in more nourishment from the atmosphere than what is necessary for the existence of the plant. This extra nourishment takes a new direction ; a pecuhar transformation takes place ; new compounds are formed, which furnish constituents of the blossoms, fruit, and seed."* Many attempts have been made to transfer the colouring matter of flowers to cloth, but without success. In general they are so fugitive as to change the moment they are brought into contact with the atmosphere, and such of them as can be extracted have no aflinity for the cloth. If a third substance be used to give this affinity, it destroys the ori- ginal colour of the vegetable. It is very probable that all the colours of flowers depend * Liebig's Agricultural Chemistry. COLOURING MATTERS. 247 upon only a few proximate elements formed in the vege- table, in the manner already described, and that their various hues are the consequence of the presence of acids affecting more or less this colouring substance. This is the most pro- bable hypothesis that has been framed, and with which we must rest satisfied till more accurate experiments verify its truth, or give us a better. The following summary of experi- ments will give some idea of the views held upon this subject : " The expressed juice of most red flowers is blue ; hence it is probable that the colouring matter in the flower is reddened by an acid, which makes its escape when the juice is exposed to the air. The violet is well known to be coloured by a blue matter, which acids change to red ; and alkalis and their car- bonates first to green and then to yellow. The colouring matter of the violet exists in the petals of red clover, the red tips of the common daisy of the field, of the blue hyacinth, the hollyhock, lavender, in the inner leaves of the artichoke, and numerous other flowers. The same substance made red by an acid, colours the skin of several plums ; probably, also, gives the red colour to the petals of the scarlet geranium, and of the pomegranate tree. The leaves of the red cabbage, and the rind of the long radish, are also coloured by this principle. It is remarkable that these, on being merely bruised, become blue, and give a blue infusion with water. It is probable that the reddening acid in these cases is the carbonic, which, on the rupture of the vessel which encloses it, (being a gas,) escapes into the atmosphere. If the petals of the red rose be triturated \vith a little water and chalk, a blue liquid is ob- tained. Alkalis render this blue liquid green, and acids restore its red colour."* We need hardly mention that the influence of light in pro- ducing colours, and changing them when produced, is regu- lated to a great extent by the vitality of the plant; so that the effects vary in intensity according to the season of the year. When leaves or flowers are taken from a plant, they are both very soon affected by light ; but it has been observed by Sir John Herschel, that flowers plucked at an eai'ly period, as when newly formed, are much more sensitive to light than at a later period of flowering, showing that flowers have a period of maturity ; and if pulled at that time, the colouring com- • Thomson's ^'egetable Chemistry. 248 VEGETABLE SUBSTANCES. pound is much more stable, and resists the action of light much more powerfully than when pulled before they are matured. This law of development and maturity is uni- versal, and may be the cause of many of the varieties — the superiority or inferiority of many vegetable dyes even of the same kind. The vegetable substances used in dyeing may be divided into two classes : first, those which are used not on account of their possessing colouring properties, but because they possess matters that have a strong attraction for the fibre, which they fill, and also form insoluble compounds with the bases, and so enabling them to act the part of mordants to the substances which are afterwards to be applied ; and, second, those sub- stances that are applied or used for the colouring matter they contain. The substances comprised in the first class of these are termed astringent, from their producing a roughening or cor- rugating effect upon the mouth, when tasted. All the vege- tables that produce these effects are found to contain certain acids, to which this property of astringency is referable ; and the presence of these acids gives them their vakie in the dye- house. These acids are gallic acid and tannic acid or tannin. It has been found, from the extensive researches of Dr. Sten- house on the vegetables containing these acids, that the tannin exists in them in a great variety of modified forms, or rather that they give certain modified reactions with chemical agents, the cause of which, analysis has not yet been able to define. For our purpose, we will divide these substances thus acted upon into two : — 1st. Those which give a black precipitate with the salts of iron — for a proper type of which may be cited galls and sumach ; and, 2d. Those which give a dark-olive precipitate with iron — the type of which is catechu. The latter is much more stable in its composition, and less liable to change by standing. Galls. Upon certain species of oak there grow excrescences which originate in punctures, made by a peculiar insect, for the purpose of depositing her eggs. A kind of juice exudes GALLS. 24y from this puncture, and gradually forms round these ova hard round bodies, varying in size from one-fourth of an inch to an inch in diameter. These substances, from their resem- blance to nuts, and from their bitter taste, are called gall-nuts.* By the repeated experiments of many excellent chemists upon this substance, it is considered to contain two peculiar prin- ciples. One of these, a crystallizable substance, is ob- tained from a macerated solution of galls, after standing in the air for a long time. This, from its possessing many acid properties, is termed gallic acid. The other is that sub- stance which combines with skins during the process of tan- ning, changing them into leather, and is termed tannin, or, from its having some acid properties, tannic acid. The best galls, according to Sir H. Davy, contain 26 per cent, tannin and 6 '2 of gallic acid, but from the circum- stance of these two compounds being generally found together in the same vegetable, and in variable proportions, it was thought probable that the one produced the other. This sup- position was verified to a great extent by M. Pelouze, par- ticularly as respects the tannin of galls. The method for extracting tannin from galls is as follows : — To a vessel, such as that re- presented in the annexed figure, is fitted by means of a cork g, a funnel-shaped tube, and the neck c is kept corked, air-tight, dur- ing the process. At the bottom of the tube is placed a little clean cotton, as shown at/ Above the cotton is placed a quantity of nut- galls in fine powder, as shown at e. Over this is poured a quantity of common sulphuric ether, sufficient to fill the rest of the tubf/, as seen at d. A cork is then fitted tightly to the opening at the top of the tube, and the whole set aside. Next day, two layers of liquor are found in the vessel a, one very light and limpid, occupying the upper part, the other having a light-amber colour, * The excrescences are produced by the cynips (gall-wasp) upon the ten- der shoots of the quercus infectoria, a species of oak which is common in Asia Minor. AVTien the maggot is hatched, it eats its way out of the nidus. The best galls are those brought from Aleppo and Smyrna. m2 250 GALLS. and the consistence of a syrup, occupying the lower part. These liquids are poured into a dropping tube, upon which the finger is kept, and after remaining at rest for a few minutes, they again separate ; the heavy liquid is then allowed to fall out into a capsule, and the hght liquid retained, so that it may be distilled for the sake of recovering the ether. The dense liquid which is in the capsule is next to be washed two or three times with sulphuric ether, and afterwards dried by a very gentle heat ; the matter left has a spongy appearance, is very brilliant, and generally of a yellow tint. This is tannin in a state of purity. By this process, from 35 to 40 per cent, can be extracted from nut- galls. M. Pelouze fovmd that if a solution of tannin be kept closely corked from the atmosphere, no change takes place ; but if left in contact with oxygen, the tannin undergoes a change, and gallic acid is formed. Hence he concludes that gallic acid does not exist except in very minute quantity in vegetables, and that the error of supposing that these two acids existed together in vegetables, arose from the method adopted to pro- cure gallic acid, which was by allowing the macerated vege- table matter to stand in contact with the air, till the gallic acid crystallized from the solution, this being nothing more than a process for converting tannin into gallic acid by the absorp- tion of oxygen. This discovey is of great importance to the dyer, as it poiniyS out the evil of allowing liquids, which contain tannin, to stand exposed to the air for any length of time ; for although gallic acid and tannin act in a somewhat simiku' manner with metallic oxides, yet the gallates are much more fugitive than the tanuates. For example, if we precipitate tannic acid and gallic acid by a persulphate of iron, they are both dark blue, bordering on black ; excepting a slight change of shade, the tannate remains permanent ; but if the gallate be allowed to stand a few hours, it is dissolved in the supernatant liquid, and becomes almost colourless ; the sulphuric acid resumes its attraction for the iron, and crystallizes as a protosulphate, (copperas,) and the gallic acid is partly decomposed and partly crystallized. These changes take place in a few minutes, if the liquor containing the precipitate be boiled. GALLS. 25 1 Now, if galls, or what is now more commonly used instead, sumach, be allowed to stand till after fermentation takes place, which is very soon, a great portion of the tannin is converted into gallic acid ; and although the cloth dyed in sumach that is thus altered should be, as some dyers affirm, equally dark, it will not be equally fast ; but from personal experience, we can say that it is neither equally dark nor equally beautiful. It cannot be so dark, for gallic acid being much more insoluble than tannin, falls to the bottom whenever it is formed, and consequently leaves the supernatant liquid much weaker in its dyeing properties. More recent discoveries have shown that tannin is conver- tible into gallic acid by other and much more rapid means than being left; to absorb oxygen : these are by the common processes of inducing fermentation. It is well known that fermentation is simply a derangement of the elements of certain complex compounds, and the re-arrangement of these elements in different positions and proportions, giving rise to new and altogether different compounds of a more simple nature, that is, having a smaller number of elements. The primary compounds are formed under the unknown influ- ence of the vital principle ; but Avhenever this is withdrawn, they seem but passively to retain their chemical conditions. The attraction of their elements seems too weak to enable them to resist any marked change of circumstances. Even a slight elevation of temperature is sufficient to overpower their affinities and induce change. As in the case of fermentation, if they are brought into contact with a body which is in the act of derangement, that body excites the same derangement in them, and the equilibrium being disturbed, the elements are left to arrange themselves according to their different attractions. If, for example, we dissolve a little sugar of grapes, which is composed of 12 carbon, 12 hydrogen, and 12 oxygen, in a little water, and raise the solution to a tem- perature of about 80° Fab. ; and if to this we add a little yeast, which is a substance whose atoms are in the act of transposition, the yeast does not combine chemically with the sugar, but it communicates to it by contact the action of transposition, and thereby deranges the arrangement which the atoms had assumed to form sugar ; and the atomic ele- 252 GALLS. ments being thus set at liberty, begin to arrange themselves differently : every three atoms of the hydrogen combine with two of the carbon and one of the oxygen, forming four atoms of alcohol. The remaining eight atoms of oxygen unite with the remaining four of carbon in the relation of one to two, forming four atoms of carbonic acid gas. Thus the whole sugar is converted into two different substances, of which the yeast forms no part. It only acts the part of a bold revolu- tionizer, breaking up existing combinations, that new ones may be formed from their elements. Now tannin is found to undergo the same sort of change as the sugar, when brought into contact with certain substances ; and one of the new com- pounds formed from this transposition is gallic acid. M. An- toine has indeed directly sho^vn, that a very small quantity of nut-galls is capable of converting a large quantity of tannin into gallic acid, and that galls contain a substance capable of producing fermentation amongst the elements of the tannin. The composition of tannin, as compared with that of gaUic acid, is as follows : — TANNIN, 18 Carbon. 12 Oxygen. 8 Hydrogen. GALLIC ACID. 7 Carbon. 5 Oxygen. 3 Hydrogen. The action which is considered to take place during the fer- mentation of tannin by exposiu-e to the air is, that it absorbs or combines with 8 proportions of oxygen from the atmos- phere — One proportion f i q p of tannin | ^» *- -j 12 O equal tx) ■< . ?qualto ■< : 2 Proportions Gallic acid. 2 Water. Oxygen im- bibed I (■ fi/ / 8H = equalto -^ ^ /( {« {«— ^ ,4 Carbonic acid. Now, in proportion as gaUic acid is inferior to tannin in its dyeing properties, will be the extent of the evil of allowing GALLS. 253 liquors which contain tannin, and which depend upon it for their dyeing properties, to stand till fermentation begins. In some liquors this commences in the course of three or four days ; much, however, depends upon the temperature. But although galls thus contain within them the property of a ferment, it may justly be asked whether sumach, which has in many operations of the dye-house superseded the use of galls, possesses the same property ? The affirmative — that it does possess the property of exciting fermentation in other substances — has not yet been determined ; but from a number of experiments upon the action of various substances on tannin, it would seem either to induce or facilitate fermentation ; and further, we venture to say, that the tannin in sumach is more readily converted into gallic acid than the tannin of gall- nuts. If the liquor of galls be allowed to stand exposed to the air, it requires a considerable time before its tannin is converted into gallic acid, but there are a n\imber of sub- stances which, if put into it, cause the formation of gallic acid to proceed much more quickly. Among others, the tartaric and maUic acids possess this property in a high degree. Now, sumach, according to some recent analyses, contains a great quantity of mallic acid, which, were we allowed to reason from analogy in chemical science, places it under very favour- able circumstances for fermentation. Indeed, in certain sea- sons of the year, we have known it to ferment in forty-eight hours. Whether this fermentation was induced first by the tannin or by the colouring matter which it contains — for sumach contains a distinct colouring matter — we cannot cer- tainly in the meantime determine. But this we weU know, that a very short exposure to the air makes it lose its colour- ing matter. It was found by the author quoted above, that a little sul- phuric, hydrochloric, or nitric acid, added to a solution of galls, makes it less liable to ferment by exposure. The following table abridged from Brande's Manual of Chemistry, will give some idea of the action of some metallic salts upon a solution of galls or sumach : — 154 GALLS. Names of Salts used. Colour of PrecipHatcs. Protochloride of manganese Dirty yellow. Protosulphate of iron (copperas)... Purple tint. Persulphate of iron Black. Chloride of zinc (muriate of zinc).. Dirty yellow. Protochloride of tin Straw colour. Perchloride of tin Fawn colour. Sulphate of copper (blue-stone) . . . YelloAv l>rown. Nitrate of copper Grass green. Xitrate of lead Dingy yellow. Tartrate of antimony and potash.. .Straw colour. Tartrate of bismuth and potash ...Copious yellow or orange. Sulphate of uranium Blue black. Sulphate of nickel Green. Protonitrate of mercury YelloAv. In attempting to draw a practical inference from some of these results, we would, for example, conclude that persul- phate of iron is much better adapted for dyeing blacks than protosulphate, as the former is mentioned as producing a deep black, whUe the latter gives only a purple tint. It is much to be regretted that in making out these tables, care is not taken to give the results in all their bearings. What is mentioned of these two salts is correct, at the instant the mixtures are made ; but in the course of twenty minutes the black from the persulphate becomes a brownish shite, whereas the purple tint of the protosulphate changes dui-ing the same time to a deep black ; and these changes continue till the former has become a light yellowish slate^ and the latter a perfect ink black. When trying the diffei-ence of effect produced by the per- sulphate and protosulphate of iron upon pure tannin and gallic acid, it may further be observed, that the changes pro- duced with tannin are somewhat similar to those which occur in a solution of galls. With galUc acid the persulphate gives at first a black precipitate, not so dark as the tannate, but in a few minutes it changes to an olive, and continues changing till it becomes almost coloui'less. With the protosulphate, at first the colour is scarcely visible, but after an hour's expo- sure, it assumes a rich violet. From these facts, it may be concluded, that tannin is superior to gallic acid as a dyeing GALLS. 255 agent for black ; moreover, the compound fonned is more insoluble. Another circumstance which modifies the results of these experiments in their application to dyeing, is the quality of the water used. If the experiments be performed with distilled water, it will be found on repeating them with common spring water, that one-half of the quantity of stufls will give the same depth of colour ; and that the colours, in this instance, have more of a purple hue, and are much more per- manent. This may be illustrated by a very simple experi- ment. Take two glass jars of equal size, fill them half full with distilled water, and add an equal quantity of a solu- tion of galls, or sumach ; put into each an equal number of drops of a solution of protosulphate of iron (copperas); the change of colour is scarcely perceptible. But fill up one to the brim with spring water, and it almost instantly becomes a dark reddish black. Allow both jars to stand for an hour, the solution with the dbtilled water will have become a deep violet, while the other, nowithstanding the double quantity of water, is so dark that no light is transmitted ; and it wiU require one-half more water to reduce it to the same shade as the other, but still retaining more of the reddish hue — which, by the way, makes it superior for black, it will also be found to be much more insoluble, and to require a greater proportion of acid to decompose it. If soft or filtered river water be used instead of distilled water, the distinction is nut so great, but still, the diflference is equal to one-half. The best water which we have experienced for dyeing black, and other saddened colours* gave by analysis, sulphuric, muriatic, and carbonic acids, lime, a trace of silica, and iron. The whole solid contents did not exceed one grain in a fluid ounce, or 160 grains per gallon, which, we may remark, is a large quantity, (see page 40.) These ingredients probably existed in the water as sulphate, carbonate, and muriate of lime, and carbonate of ii-on. The iron was in very small pro- portion ; the carbonic acid and lime greatest. Now a dyer, learning his trade in a work where such water was used, could not fail to become a successful dyer of all saddened colours ; but were he taken from this work to * A technical name for colours that arc darkened by sulphate of iron, which includes drabs, fawns, slates, gray, some kinds of browns, blacks, &c. 256 GALLS. another where soft filtered water was used, what would be the result ? When he attempted to dye a black with the same quantity of dyestuff he formerly used, he would only produce a dark-slate colour; and if he wished to obtain a slate colour, he would produce a gray. In this dilemma, the dyer adds stuff tiU he comes to the desired shade ; but fancy- dyes, bolstered up with stuffs, are not so pretty ; besides, the employer, in consequence of this extra stuff, must either sub- mit to a loss, or discharge the dyer ; who, no doubt, consider- ing himself iU-used, talks loudly of his ability in dyeing such colours, and offers to prove that the fault is not in him but the water. Were this whoUy a supposed case, we would pause here, and make an apolog)' to oiir brethren for these remarks ; but not being so, we wiU rather endeavour to show that the fault is the dyer's. Dyeing being an art whoUy dependent upon chemistry for its development and successful practice, he who practises it, without studying chemistry, is like a boy learning to repeat a number of choice sentences from an author, ^\■ithout knowing his letters. Had the dyer, aUuded to, kno>vn the principles of chemistry, so far as they are applicable to his trade, he would, on finding that the same quantity of stuffs did not yield the same results, have examined the water to discover where lay the difference, and in this particular case he would find, that instead of adding an extra quantity of sumach, copperas, and logwood, to get a good black, a Uttle chalk and hydrous gypsum (sulphate of lime) added to the water, would so qualify it as to render it equally effective with that to which he had been accustomed. There are several kinds of galls, but the following three kinds occur in commerce — Aleppo galls, Sm}-ma galls, and East Indian galls. These three kinds consist, according to the ripeness of the apples, of black, green, and white galls, "When the galls occur in commerce mixed, they are termed "natural;" and are sorted into the following kinds : — picked black, natu- ral black, (consisting of black and dark-green galls), dark green, Ught green, natural white (hght green and white galls), and picked white. Aleppo galls are the best; but under this name must be reckoned not only such as come from Aleppo, but also those derived from Mosul in Nataha, and which are therefore called in Constantinople and Smyrna lists, not Aleppo, but Mosul galls. This gaU recom- GALLS. 257 mends itself by its heaviness, and the lighter-coloured kinds (white and light-green galls) are frequently remarkable from their large size ; but the best distinguishing character between the Mosul and Smyrna galls, is the darker kind of the Mosul galls having as it were a blueish bloom, while the Smyrna are of a grayish colour. The Mosul gall, moreover, has not so many tubercules as the Smyrna kind. The first is exported from Constantinople and Smyrna, the latter principally from Smyrna. The chief markets are Trieste, Leghorn, Mar- seilles, and London. The fourth kind of nut-gall is the mar- raorated one, which is brought from Puglia ; the chief staple places are Naples and Trieste. It consists generally of large, apples, which have fewer tixbercules, and these not acute. They are generally of a whitish-red and greenish colour, sometimes also darker. Istria produces a very inferior kind of galls ; they are small, commonly of a reddish colour, and are much tuberculated. Place of export, Trieste. These are the principal kinds, not to mention others of rare occur- rence ; for instance, a kind of gall is brought from Asia Minor and Dalmatia, which is hollow, not heavy, and of a reddish colour. Analysis of galls by ^L Guibourt : — Woody fibre 10-5 Water 11-5 Tannm 650 Gallic acid 2-0 Ellagin acid and luteo gaUic acid 2-0 Extractive matter 2*5 Gum 2-5 Starch 2- Clorophylle 0-7 Sugar 1-3 100-0 The luteo gallic acid applied to the yel- low colouring matter of the galls. Sometimes white galls are dyed by a little iron water being ► put upon them, which darkens them, and makes them appear of a better quality. 258 Sumach. Called by botanists rhus coriaria, is a native of Syria. It is diligently cultivated in Spain, Portugal, and in some parts of Italy and Sicily, and known in the market as Sicily, Malaga, Trieste, and Verona : the first is the best quahty. A quantity of about 60,000 tons of this dye is used annually in this country. The sumach tree, or rather shrub, grows to a height of about eight or ten feet ; the stems are ligneous, and divide at the bottom into many irregular .branches ; the bark is hairy and of a brown colour. The leaves are \vinged, have seven or eight pair of jagged lobes, and terminate in an odd one. The leaves are placed alter- nately upon the branches, which are surmounted by flowers of a greenish-white colour. The shoots of the shrub are cut down every year close to the roots, and after being dried, are reduced to powder by means of a mill ; the very fine stems are often cut into small pieces, and put amongst the powder. We have already referred to the use of sumach in the dye- house ; we speak of it simply as a fit substitute for galls, pos- sessing similar properties, and seemingly passing through similar decompositions by exposure. A httle sulphuric acid added to sumach retards fermentation, but it is not a good addition when dark shades are required, and should only be used for sumach which is to stand for some time, or which is to be used for very light drabs. In this case the colour obtained is more pleasant — technically more sweet; but either the addition of acid, or by standing exposed to the air, very soon destroys the colouring matter which sumach contains, and also the depth of shade of dye obtained from it. It is, therefore, always advisable to use the sumach newly boiled. The com- parative advantages of using it newly boiled and after it has been kept for some time, can easily be ascertained by taking a given quantity, boiling it, and allowing it to stand over a few days ; then taking the same quantity, boiling it the same length of time, heating the old solution to the same tempera- ture as the new, and adding to each the same weight of cot- ton; the effects produced will be very different, and will, more than any written description, show the importance of attend- ing to this circumstance. SUMACH. 259 Sumach is generally used when the metallic base, or mor- dant, is iron or tin, and is therefore the bottom * of blacks, reds, &c. Sicilian sumach has a greenish-yellow colour. When bright colours of red are to be dyed it is best ; also for barwood, and all colours that require clearness. Verona sumach when compared with Sicily has a fawn tint ; it is best tor deep reds, browns, and blacks. When used for barwood reds the colour is heavy, and to use Sicilian sumach for the purposes that Veronian is most suitable, would require about one-hah' more in quantity for the same weight of cloth. The following process for dyeing black will enable us to illustrate some of the reactions of this substance in connection with the metallic bases : — The goods are allowed to steep in a decoction of sumach for twelve hours ; they are then wrought through lime-water, which gives them a beautiful blueish-green colour, becoming very dark with a short exposure to the air. If allowed to stand for half-an-hour, the green colour passes off, and the goods assume a greenish-dun shade. When they are at the darkest shade of green, they are put through a solution of copperas ; after working some time in this, and allowing them to stand exposed to the air, they become a black. But if dried from this, it is only a slate or dark gray. They are there- fore again put through lime-water, which renders them brown, and then wrought through a decoction of logwood till the colour of the wood has nearly disappeared. A little copperas is added, which throws off the reddish hue of the wood, giving them a blue shade. This is termed raising the colour. The goods are washed from this in cold water, and dried in the shade. When a deep blue-black is wanted, the goods are dyed blue previous to steeping in the sumach. The passing of the goods from the sumach through lune, be- foi'e introducing them into the iron solution, is not essentially necessary for producing the colour, but is very useful in facihtating the operation, and in giving depth of hue by the iron. This metal is held by the strong affinity of the acid, but the goods, impregnated with lime, being put into the copperas, the lime takes the acid, and the iron, Uberated im- mediately and in greater quantity, takes to the tannin of the • Bottom is a technical term applied to the preparation of cotton by sumach and the like, for colours. 260 SUMACH. sumach. The passing through lime-water from the copperas solution, is for the purpose, also, of neutralising the acid 'of the iron upon the goods, which, as a salt, would act upon the logwood, and injure the operation. Washing out of the cop- peras answers equally well, and for fine goods, where a soft tint of black is necessary, is even preferable. When the goods are passed through the hme, the presence of the alkali is hurtful to the logwood ; therefore it is best to pass the goods through water before entering them into the logwood. The action of the iron upon this substance is the same as we have described for galls ; a persalt of iron added or used, gives an immediate black, but not permanent ; the oxygen seeming to affect the decomposition of the colour in some way. TV'Tien a protosalt of iron, as copperas, is used, the blackening is slower, but more permanent ; showing that it is the most suitable salt to use. It is, however, to be remarked, that the combination of iron and tannin, forming the black colour, seems to depend on a state of oxidation of the iron a little higher than the protoxide, and much lower than the peroxide ; that the peroxide when used, is reduced in oxidation, and causes change and loss in reduction, and that the protoxide imbibes oxygen as required.* Upon this im- portant inquiry we quote the folloAving from an article by M. Barreswil in the Chemical Gazette, translated from the Comptes Rendus :~^ " When a solution of gallic or of tannic acid, which are colourless, and generally form colourless salts or of the colour of the bases, is poured into a solution of the persulphate of iron, an intense blue precipitate is formed, which remains suspended in the liquid. This anomalous fact has frequently excited the attention of chemists, MM. Berzelius and Chevreul have even expressed some doubts respecting the simplicity of the reaction. " It has long been known that tannin and galhc acid do not precipitate the protosalts of iron when protected from contact with the atmosphere. Berzelius, Chevreul, and Per- soz, have, moreover, observed that when gallic acid or tannin is conveyed into a salt of the peroxide of iron, it is always reduced to the state of a protosalt. This fact is easily proved • An opinion urged several years ago by the author in the Practical Mechanics' and Engineers^ Magazine. SUMACH. 261 by adding to the blue solution produced by the persulphate of iron in a solution of gallic acid, an excess of acetate of lead or of carbonate of lime, which precipitates the blue combina- tion, and at the same time the sulphuric acid. A colourless liquid is separated by filtration, in which the presence of iron may be demonstrated in the state of protoxide. " These experiments are insufficient to explain this curious reaction. It is not improbable to admit, as MM. Berzelius and Chevreul have done a priori^ that the Oxygen combining with the gallic acid or the tannin converts them into a new acid of a blue colour ; but positive experiments were wanting to decide the point. " When a solution of tannin or of gallic acid is poured by drops into a solution of persulphate of iron in excess, no blue colouring is obtained ; if there is one produced it is only momentary. Nor is there one formed with the same salt in minimum in presence of chlorhie, nor with a protosalt of iron and gallic acid oxidized in various degrees by chlorine, by a salt of silver, or lastly, by the atmosphere in an alkahne solution. " When a solution of gaUic acid in excess is conveyed into persulphate of iron, and the liquid thrown do^vn by acetate of lead, a blue paste is obtained, which treated with oxaUc acid forms soluble oxalate of iron ; the blue colour disappears entirely, and is restored by acetate of soda. The solution of the oxalate, diluted very much with water, treated cautiously with the two prussiates and sulphuretted hydrogen, presents all the characters of the salts of iron in the state of peroxide and protoxide. " It appears to me that we may conclude from the above facts, that if we start with a protosalt of iron, it is requisite to add oxygen, and if we set out with a persalt, some oxygen must be removed, in order to produce the blue compound, and that this compound contains the two oxides. In the first case the protoxide of iron combines with the oxygen of the atmos- phere ; in the second, a portion of the oxygen of the peroxide destroys a corresponding portion of the gaUic acid or of the tannin, converting it into a brown substance. This substance does not enter into the constitution of the new compound, which must be considered as a salt formed of tannin or gallic acid and of an intermediate oxide of iron, probably of a blue 262 SUMACH. colour, tlie tint of which is slightly altered by this brown substance. " To prove in the most evident manner that the blue colouring is not to be ascribed to a blue acid, but to a particu- lar oxide, I endeavoured to obtain other blue salts with mineral acids, for instance with sulphuric acid. For this pur- pose I prepared some mixtures in variable proportions of the protosulphate of iron and of the persulphate, and to aA-oid an inevitable separation of the two salts from their different degrees of solubility, I removed immediately the water by adding to the solution concentrated sulphuric acid in large excess, taking care to produce as little heat as possible. In this manner I obtained a thick paste of a deep blue, the tint of which was more or less pure according to the proportions of the two salts of iron : I Hkewise produced a blue sulphate, but of very ephemerous existence, by evaporating rapidly a mixture of the two scdts of iron ; the blue tint appeared at the moment Avhen the mass was nearly dry. On substituting phosphate of soda for the sulphuric acid, I obtained a deep- blue phosphate of iron and some sulphate of soda, which removed the water immediately. 1 endeavoured, but Avithout success, to prepare combinations with other salts ; the hypo- sulphite of soda alone afforded an intense blue colouring, but of remarkable instability. This is not surprising ; there are many instances in chemistry of bases which prefer combining with certain acids and refuse to unite with others ; such for instance, among others, is the protoxide of copper. "I made niunerous experiments to obtain the blue oxide in a free state ; I succeeded several times, biit under circum- stances which I was not able to produce at will. It is, how- ever, a well-known fact, that when a protosalt of iron is pre- cipitated with ammonia in contact with the atmosphere, the white precipitate of the protoxide soon becomes green, passing first, however, through blue. " The impossibility of obtaining the blue sulphate of iron in a crystalline state, and of isolating the acid of the blue gal- late compound, prevented me from having recourse to analysis in order to arrive at the formula for these intermediate salts : I was forced to proceed by synthesis, which I confess is far from being accurate ; and it is with some doubts that I pubUsh the results. CATECHU, 263 " Of all the mixtures of protosulphate and persulphate which I experimented on, that which afforded the most pure blue with sulphuric and gallic acids and with the phosphate of soda, contained precisely 3 equivalents of protosalt to 2 of the persalt — proportions which correspond to the cyanide Fe? O9, Prussian blue. " If, as I hope, I have rendered probable the existence of two intermediate oxides of iron, capable of fonning salts and of entering into the salts with their peculiar colour, I shall have thrown some light on the various tints produced by the different kinds of astringent substances, morphine, salicylic acid, and some other organic principles ; and likewise on the production of violet, black, brown, and green tints, with red and yellow-colouring principles, in presence of salts of per- oxide of iron. I have convinced myself that all the yellow- colouring substances (for instance ciu-cuma) do not produce green ; that the red-colouring principles (among others aloetic acid) do not give a violet ; and that when there is a produc- tion of green, (as with the Persian berries and the Quercitron,) or of violet, (as with madder, logwood, &c.,) the phenomena are identical with those which occur with tannin and ■ galhc acid. These observations agree, moreover, perfectly with the suppositions of M. Thenard, with the facts published by M. Kochlin-Schouch, and by M. Schlumberger, and which M. Stackler informs me he has found confirmed in his establish- ment, that the iron mordants should be at a fixed degree of oxidation to produce beautiful dyes." — Comixes Rendus. Catechu. This is another substance containing much tannin. We have already noticed some of its peculiarities, but may state further that it is a dry extract prepared from the wood of a species of sensitive plant, named acacia catechu. It was long considered an earthy substance, and termed terra Japanica. The plant is indigenous to Hindostan, and floiir- ishes abundantly in mountainous districts. It grows to about twelve feet in height ; the trunk is about a foot in diameter, and covered with a thick dark-brown bark. The extract which is obtained from the tree is made from a decoction of 264 CATECHU. the wood. As soon as the trees are felled, all the exterior white wood is carefully cut away, the interior, or coloured wood, is then cut into chips ; narrow-mouthed unglazed pots are nearly filled with these, and water is added to cover them. Heat is appHed, and when half the water is evaporated, the decoction, without straining, is poured into a shallow earthen vessel, and further reduced two-thirds by boUing. It is then set in a cool place for a day, and is afterwards evaporated by the heat of the sim, care being taken to stir it occasionally during that process. When it is reduced to considerable thickness it is spread upon a mat or cloth, which has been previously covered with the ashes of cow dung, and this mass divided by a string into quadrangular pieces, is completely dried in the sun, and is then fit for sale. It is a brittle compact substance, of a dark-brown or choco- late colour ; has no smell, but a very stringent taste ; is soluble in water ; contains a great amount of tannin, and a pecuUar acid, which has been named catechuic acid. It is the reactions of these ingredients with oxygen and other chemical agents, that constitute its dyeing properties. A solution of catechu in water is a beautiful reddish- brown colour, which ought to be kept in mind in perusing the following summary of the reactions of other substances upon it : — Acids brighten the colour of the solution ; alkalis darken it, and the shade deepens by standing ; protosalts of iron give olive-brown precipitates ; persalts of iron also give ohve- brown precipitates, but with more green than those of the protosalts ; salts of tin give yellow-brownish precipitates ; nitrate and sulphate of copper, yello^nsh-brown ; acetate of copper, a brown precipitate; salts of lead, brick-coloured pre- cipitates ; bichromate of potash, a deep red-broNvn. These reactions alone indicate how very important an agent cate- chu may be in the hands of the dyer, and how very exten- sive its apphcations in the processes of his art. There are various quahties of catechu in the market, dif- fering considerably in their value as a dye. The Bombay catechu is met with in square masses, of a reddish- brown colour, and which, when broke, exhibit a imiform texture. Its composition is as follows : — CATECHU. 265 Tannin 52 Gum 7 Extractive matter 34 Impurities 7 100 " Extractive matter " is a sort of indefinite term, applied to designate a brown matter extracted from vegetables when boiled ; its true nature is not known, but the part it may play in the reactions of catechu is probably important, and is at least not to be overlooked. Bengal catechu is met with in flattish round lumps, of a light-brown colour outside, but dark internally. It gives : Tannin 49.5 Gum 7.Q Extractive matter 36-5 Impurities 7-0 1000 Malabar catechu is imported in large masses, of a light- brown colour outside, dai-k within, and covered with leaves. It gives : — Tannin 45.3 Gum.... ■"//. 3-0 Extractive matter 39-9 Impurities g-3 1000 There is a sort of catechu brought to this country from India m small cubical masses, about an inch in size. This is a very inferior quality, and, as imported, is easily known from genume catechu. Sometimes, however, means are resorted to, to alter the colour of this spurious article, and make it more difficult to be detected. It is said often to contain a great quantity of roasted starch, or British gum, termed dex- trine. Catechu is often adulterated by other vegetable extracts, and also by sand, clay, and ochre. These last impurities may be readily detected by dissolving a portion of the catechu in N 266 CATEcnu. water, when any of them contained in it will be pre- cipitated ; or by burning a little of it in a crucible until all organic matter is consumed, when the latter adulterants ■N^'ill remain. We have examined samples of catechu of good colour, ha'i'ing 8^ per cent, of clay and sand mixed with them. Good catechu is all soluble in cold water, and gives a clear solution. The tannin which is in catechu is not converted into galhc acid by exposure so easily as that in galls ; but it is subject to oxidation. Wlien a portion is dissolved in water, the solution has a gummy character, and goods put into it would be affected as by a weak solution of gum ; the threads of yarn, for example, adhere when dried out of it. The addi- tion of a metallic salt destroys this viscous quality, and those salts answer best, or are most effectual for that purpose, which yield their oxygen most easily. Accordingly, the salts of copper are most commonly used, and they are added to the dissolved catechu before putting in the cotton. The chemi- cal changes which catechu undergoes in the operations of dyeing, are not yet well understood. The action ha.s been explained in this way : — The copper salt oxidizes a portion of the catechu, which, although insoluble in water, is soluble in deoxidized catechu ; therefore, the whole is held in solu- tion in the bath ; the goods become impregnated with this solution, and as the Avhole of the catechu upon the cloth becomes oxidized, it becomes also dark. This explanation does not account for all the phenomena occurring during the dyeing of browns, &c., with this substance; for if we take two portions of a solution of catechu, and to the one add a salt of copper, to the other a salt of zinc, pass the cloth from these through a solution of lime, and expose to the air, the piece treated with the zinc will become dark brown, but not that treated with the copper. The above explanation would lead us to expect the opposite, as copper yields its oxygen more easily than zinc. When catechu is oxidized, there is formed an acid nearly of the composition of gallic acid, which has a deep-brown colour. This is formed when catechu in so- lution is treated with alkahne matters. The hme, therefore, in the above experiment, may have acted the principal part ; but cotton from catechu solution, put through acetate of lead, also gives a deep-brown colour witliout alkali. When VALONIA NUT3. 2 67 goods impregnated with catechu are passed through bichro- mate of potash, there is obtained a deep blown : an oxidation of tlie catechu takes place at the expense of the chromic acid. Whether the oxide of chromium may act as a base on any part of the dye, we cannot positively affirm ; but on burning cotton dyed brown by this means, there is obtained in the ash the oxides both of chrome and of copper ; showing that both the copper and chrome used, play a part in form- ing the dye: and that the dye by this method is something more than mere oxidation of the catechu, as in passing the cloth from the catechu through bleaching liquor. The reactions of catechu are so varied, that it is now used for almost all compound colours, blacks, browns, greens, drabs, and fawns ; and its permanency renders it of high estimation in the market. The following is the analysis of a sample of catechu by Mr. Cooper, giving a wider range to the matters contained in it, and which will serve to give some better idea of the varie- ties of this substance ; for, from its mode of preparation, pro- bably no two samples will give the same proportions : — Tannin 62-8 Extractive, or colouring matter 8"2 Eesinous matter 2*0 Giunmy matter 8"5 Insolulable matter 4'4 Water 12-3 98-2 Fnlonia Nuts.— These are the cups of the acorn from the valonia oak, which grows in the Dardanelles and the islands of the Archipelago, and throughout all the maritime ports of Asia Minor. They are imported in great quantities from Smyrna and its neighbourhood. These contain a great quantity of tannin, and also gallic acid ; but they are inferior to sumach or galls for dyeing cotton, and for giving depth of coloiu- with the salts of iron. For silk, however, they possess some peculiarities exceedingly valuable for blacks, giving a permanency not obtained with the ordinary galls ; and more- over, the production of the proper black with valonia nuts upon silk requires a certain treatment which few dyers have attained. 268 VEGETABLE SUBSTANCES CONTAINING TANNIN. particularly in Scotland. We cannot, for instance, furnish a black upon silk which will withstand unchanged all the operations which a hat undergoes in the process of manufac- ture — a purpose for which we understand the valonia black is applied. Uivi Divi— Or Libi Dart, is the pod of a leguminous shrub, a native of South America ; it has been tried as a dye instead of galls or sumach, but is not much used now, if at all. MjTobalans.— This is the fruit of a tree which gi-ows in India ; it is imported into this country in various forms, has a pale-yellow colour when new, but becomes darker by age, and then resembles dried plums. It contains tannin, and is sometimes used on that account for the operations of dyeing. Its reactions with iron, tin, and alum, are similar to those of sumach, but of less value. Oak bark contains a great quantity of tannin, and is used on that account for tanning skins, but it is not much employed in the dye-house, although it may be used for similar pur- poses as sumach. The bark of the mangrove tree also contains tannin in considerable quantity ; there are, indeed, very few vegetables which have not in their composition more or less of tannin, and which may not be used in virtue of this pro- perty instead of galls or sumach ; but the quantity in them being much less than in sumach, they are not cultivated for that purpose. The bark of the ash, willow, hazel, birch, broom, &c., are often used for dyeing woollens by country people ; and some of these substances possess peculiar dyeing proper- ties. The husks of several nuts also contain much tannin. The walnut, for instance, has been long used and much esteemed by the French dyers for woollen stuffs ; it gives very fast shades, without previous mordanting, although alum is sometimes used to give variety. The outer peel of this nut is collected for the dyers ; they are put into large casks, with water poured over them, and kept for a year or more, as they improve while this process of maceration is prolonged. The roots of the walnut tree are also used for dyeing browns. The husks of the horse-chesnut likewise possess dyeing qualities, and might be applied advantageously for some purposes. Mahogany saw-dust, although not affected much by mordants, possesses dyeing properties of considerable value, yielding with iron a variety of shades of great permanence and beauty. TEST FOB TANNIN. 269 ^fany of the dye-woods which are used for their colouring matter contain tannin, the action of which upon the mor- dants is often very injurious to the tint. Many varieties of the diflferent woods, giving the same colour, depend much upon the presence of tannin. The whole woody matter being boiled to extract the colouring matter, the tannin is also dissolved, and it is sure to act upon the mordant in the pro- cess of dyeing, producing an effect very similiar to that of adding a little sumach to the colouring matter. In many cases this is done beneficially, but in other cases it would deteriorate the tint required. In such cases the presence of tannin in the colouring matter obtained from the wood does not suit. Mr. Warrington proposed as a practical means of ascertaining the quantity of tannin in any matter, the following test : — Pre- mising that a solution of gelatine, isinglass, or glue, precipi- tates tannin : making a given quantity of this solution by adding dmp by drop to a given quantity of the substance to be tested for tannin, also in solution, as long as a precipitate is formed, and marking in the alkalimeter the quantity of gelatine used ; every three grains of pure gelatine is equal to two grains tannin, and accordingly it is easy to arrive at a near approximation of the quality of these dyestuffs. This operation will, no doubt, require a little experience, but it is easily performed, and well deserves attention. INDIGO. In the few introductory remarks we made upon vegetable colours, we mentioned that, besides the green of leaves and the colours of flowers, which we considered common to all vegetables, there were other colouring matters, which existed only in certain kinds of vegetables, and in particular parts of the vegetable. Indigo is one of these : it belongs to a genus of leguminous plants found in India, Africa, and America, named indigofera. Botanists have described about sixty species of this genus. These all yield indigo ; but the species from which it is usually extracted are the /. anil., the /. ar- gentea, and the /. tinctoria. It is also extracted from a tree very common in Hindostan, (the nerium tinctoi^imn of botanists,) and from the woad plant, {isatis tinctoria,) which is a native of Great Britain, and of other parts of Europe. The colour- ing matter of these plants is wholly in the cellular tissue of the leaves, as a secretion, or juice — not, however, in the blue state in which we are accustomed to see indigo, but as a white substance, which as we shall presently see, remains ■white, so long as the tissue of the leaf remains perfect. "When this tissue is by any means destroyed, the indigo absorbs oxygen from the atmosphere, and becomes blue. Of the early history of indigo little is known ; neither is it known when it was first used as a dyestuff. The Greeks and Romans used it as a paint, under the name of indicum. Its value as a dyestuff was not known in Europe till nearly the close of the sixteenth century, when it was importe"d from India by the Dutch ; but our legislators, for a long time, pro- hibited its use in England under severe penalties. These pro- hibitions continued in force till the reign of Charles II., and the reason assigned was, that it is a corrosive substance, de- structive of the fibres of the cloth, and therefore calculated to injure the character of the dyers of this covintry. This opi- nion, no doubt, sprung from the strong and interested opposi- MANUFACTDRE OF INDIGO. 271 tion to its use by tlie cultivators of the woad, which was then i-ogarded as an important branch of national industry. " When indigo Was first introduced, only a small quantity was added to the woad, by which the latter was much im- proved ; more was afterwards gradually used, and, at last, the quantity became so Ihrge, that the small admixture of woad served only to revive the fermentation of the indigo. Ger- many thus lost a production by which farmers, merchants, carriers, and others, acquired great riches. In consequence of the sales of woad being so much injured, a prohibition was issued against the use of indigo in Saxony, in the year 1650 ; and in the year 1G52, Duke Ernest the Pious caused a proposal to be made to the diet by his envoy, that indigo should be entirely banished from the empire, and that an exclusive pri- vilege should be granted to those who dyed with woad. This was followed by an imperial prohibition of indigo on tlie 21st of April, 1 654, which was enforced with the greatest severity in his dominions. The same was done in France ; but in the well-known edict of 1669, in which Colbert separated the fine from the common dyers, it was stated, that indigo should be used without woad, and in 1737, dyers were left at liberty to use indigo alone, or to employ a mixture of indigo and woad." — Barlow's Manufactures and Machinery of Great Britain. The plant which yields the indigo in Bengal is a small straight plant, furnished with thin branches, which spread out and form a sort of tuft ; the average height is four feet, but on good ground it sometimes attains a height of even seven feet. The leaves are soft, and somewhat like those of the common clover, and the blossoms ai'e of a light-reddish colour. The plant is at its greatest perfection, and yields the greatest quantity of indigo, when in full blossom. There are two methods of extracting the coloui'ing matter from the leaves : the first is by fermentation and beating. This process is conducted in two large brick cisterns or vats, built in relation to one another, like two steps of a stair. The upper one is termed the steeper, because in it the fermenta- tion is conducted. At the bottom of this cistern there is a plug-hole through which, when the process of fermentation is finished, the fiuid is run off into the lower cistern, denomi- nated the beater, because in it the process of beating the fluid 272 MANCFACTLRE OF INDIGO. by paddles, to separate the feculoe from the water, is per- formed. The plant, when cut, is tied up in bundles about five feet in circumference, and conveyed as quickly as possible to the vat ; for, were it kept but a short time in heaps, the indigo in the plant would be destroyed. The upper vat is filled to about five or six inches from the top with these bundles laid in regular tiers. To prevent the throwing up of the, herb by the swelling and agitation caused by the fermen- tation, there are irons built in the two side walls, opposite to one another, to which are fastened beams of wood, which tra- verse the Avhole length and breadth of the vats. When the vat is sufficiently filled with the vegetable, a strong grating of bamboo, large enough to cover the whole surface, is laid over the plant, and fastened down by the cross beams. Tliese pre- cautions being completed, cold water is poured as quickly as possible into the vat, till the surface rises within three or four inches of the upper edges. In a short time fermentation commences, and is completed in from nine to twelve hours. Towards the end, the action is very brisk, swelling and throw- ing up frothy bubbles, which sometimes rise like pyramids. These bubbles are white at first, but after a little exposure to the air, they become blue, and then purple. This part of the operation requires great skill. If the fermentation be too long, the indigo will be much damaged ; and, if too short, the quantity is much diminished. When the liquor ceases to swell, it is let out into the second or beating vat, and is then of a light-green colour. The liquor being now in the lower or beating vat, a num- ber of men enter it, furnished with oar-shaped paddles, about four feet in length ; they continue to walk backwards and forwards, agitating or beating the liquor with these paddles. At the commencement of this agitation, the Hquor begins to froth ; but this is prevented, provided the fermentation has not gone on too long, by a few drops of oil. In the course of an hour and a-half, the liquor begins to granulate, and assume the appearance of agitated water, full of wood grounds or sawdust. This part of the process also requires consider- able care and management ; for, if the beating be stopped too soon, the indigo will not be all separated from the liquor, occasioning a proportionate loss ; if continued too long, the granulated particles are broken, and disposed through the MANUFACTURE OF INDIGO. 273 liijiior, and do not readily fall to the bottom. When the beating is completed, the vat is allowed to settle ; the grains which constitute the indigo fliU to the bottom, and the super- natant liquor is let off by plug-holes in the side of the vat. The precipitate is then removed to a copper boiler, to which there is a fire kept till the liquor becomes as thick as oil. Some manufacturers bring it to this state by causing the liquor to boil ; others by keeping it at a moderate tempera- ture. The former process produces lighter indigo than the latter. In this state it is put into a large flat vessel, furnished at the one end with a cloth filter. After most of the liquor has filtered through, the indigo remains in the vessel about the consistence of butter. It is then put on proper frames, and subjected to considerable pressure by a sort of screw- press ; and is now ready to be cut into small cakes, which are placed upon boards in a drying stove ; when dry, these cakes are packed up, and in this state form the indigo of com- merce. The other method of extracting the indigo from the plant diflfei-s from that described, only in the first operations. In- stead of putting the plant into the vat when newly cut, it is spread out, to dry in the sun for two days, and then thrashed to separate the leaves from the stems. The leaves are then kept until they have changed from a green to a blueish-gray, or lavender colour ; they are then put into the first vat with warm Avater, and kept stirring till the leaves are so completely wetted as to sink. The liquor is then instantly let off into the beating vat, where it is treated as already described. The chemical changes which take place during these opera- tions are not well understood, and the various opinions ex- pressed by chemists concerning them are not very easily reconciled. Berthollet in his Elements of D3'eing, while de- .scribing the process of the first or fermenting vat, says, " In the first a fermentation is excited, in which the action of the atmospheric air does not intervene, since an inflammable gas is evolved. There probably results from it some change in the composition of the colouring particles themselves, but especially the separation or destruction of a yellowish substance, which gave to the indigo a greenish tint, and rendered it sus- ceptible of suffering the chemical action of other substances. This species of fermentation passes into a destructive putre- n2 274 MANUFACTURE OF INDIGO. faction, because the indigo, as we shall see, has a composition analogous to that of animal substances." Dr. Ure, in his Dictionary of the Arts and Manufactures, says, that from some experiments made upon the gases given off dui'ing fermentation, they were found to be composed, when taken about the middle of the operation, of 27"5 of car- bonic acid gas, 5 '8 of oxygen, and 66 "7 of nitrogen, in the 100 parts; and towards the end of the operation, they con- sisted of 40-5 of carbonic acid gas, 4-5 of oxygen, and 55 of nitrogen. No carburetted hydrogen is disengaged. " The fermenting leaves," using the Doctor's w^ords, "appar- ently convert the oxygen of the air into carbonic acid, and leave its nitrogen free." They also evolve a quantity of car- bonic acid spontaneously. It will be observed that these two opinions are decidedly contradictory ; the one saj^s that the action of the atmosphere does not intervene, and that an inflammable gas is evolved ; the other, that there is no inflam- mable gas evolved, and that the air is apparently the principal agent in effecting the various changes. But when we recollect that the leaves are all under the liquor, and kept so by the fixed position of the beams, there can be little contact between the fermenting leaves and the air, except that held by the water, and among the leaves, and of the plants themselves ; hence the conversion of its oxygen into carbonic acid gas must be very limited. Sir Robert Kane says of this process : — "After some time a kind of mucous fermentation sets in ; carbonic acid, ammonia, and hydrogen gases are evolved, and a yellow liquor is obtained, which holds the indigo dissolved. The theory of this action is, that by the putrefaction of the vegeto-animal matter of the leaves, the indigo is kept in the same white soluble condition in which it exists in the plant." Dr. Thomson, in his Vegetable Chemistry, supposes that the indigo exists in the plant in union with another substance, and during fermentation that substance is decomposed, and car- bonic acid gas consequently evolved. But we will give his own words: — "The leaves of the indigofera yield a green in- fusion to hot water, and a green powder may be precipitated from it; but unless a fermentation has taken place, neither the colour nor the properties have any resemblance to those of indigo. There is little doubt that in the leaves it exists in MANDFACTURE OF INDIGO. 275 the state of ivhite or deoxygenated indigo, and that during the fermentation, it combines Avith the requisite quantity of oxy- gen to convert it into blue indigo. The evolution of car- bonic acid gas renders it not unlikely that the ivhite indigo was in combination -with some principle (probably of an alkaline nature) which was decomposed during the fermenta- tion." These discrepancies of opinion relative to the nature of the changes which take place during fermentation, show that pro- per investigations have not yet been niade into this part of the process : and it is obvious that until this be done, any hypo- thesis founded upon statements concerning the gases evolved, must be unsatisfactory. The supposition hazarded by Dr. Thomson certainly appears to us the most consistent ; for as deoxidized indigo combines readily with alkaline substances, and as the vegetable alkalis almost always contain nitrogen, we can easily conceive of that gas being evolved either free or in combination with hydrogen, forming ammonia. It may yet be found that indigo, like gallic acid, does not exist in the living vegetable, but is the result of a decomposition of some more complicated compound. The chemical action which takes place in the second vat in which the beating process is conducted, is apparently much more easily explained, and therefore the discrepancies among writers on the subject are not so great. We shall give only two quotations. Berthollet says, " Hitherto the colouring particles have preserved their liquidity. In the second opera- tion the action of the air is brought into play, which, by com- bining with the colouring particles, deprives them of their solubility, and gives them the blue colour. The beating serves at the same time to dissipate the carbonic acid formed in the first operation, which action is an obstacle to the com- bination of the oxygen." Dr. Ure's opinion is thus expressed : — " The object of the beating is threefold ; first, it tends to disengage a great quantity of carbonic acid present in the fer- mented liquor ; secondly, to give the newly-developed indigo its requisite dose of oxygen by the most extensive exposure of its particles to the atmosphere ; and, thu'dly, to agglomerate the indigo in distinct flocks or granulations. In order to hasten the precipitation, lime water is occasionally added to 276 MANUFACTURE OF INDIGO. the fermented liquor iu the progress of beating ; but it is not indispensable, and has been supposed to be capable of deterio- rating the indigo." That the liquor in the beating vat absorbs oxygen from the air, as the indigo separates from it, has, we believe, been as- certained by du'ect experiment ; and it is also known to manu- Jacturers, that the sunshine assists in the separation of the indigo from the liquor. But, though these facts may have been ascertained, it does not give us any positive information respecting the nature of the change which takes place in the vat ; neither can we expect such information till it be ascer- tained what keeps the indigo in solution previous to the opera- tion of beating. Both oxygenized and deoxygenized indigo are insoluble in water ; there must therefore be some sub- stance in the liquor capable of holding the indigo in solution previous to being beat. According to our present knowledge of the nature of white or deoxidized indigo, there is no other substance can hold it in solution except the alkalies and alka- line earths. But during such a generation and emission of carbonic acid gas, the existence of any known alkali capable of holding the indigo in solution in those vats is next to im- possible, and the results prove the contrary; for while the acid is liberated, the indigo becomes more insoluble — a result which is just the opposite of what we conceive would take place were an alkali present — except we suppose that the carbonic acid is the result of the decomposition of the alkali, or alkaloid, or is evolved as already hinted, from the decom- position of a substance which is resolving itself into indigo. Having given the opinions of several chemists upon the chemical nature of the manufacture of indigo, and hinted at the difficulties which some of these theories involve, we shall now consider the nature of indigo; and, whatever be the che- mical changes which take place in the beating operation, we are certain that the indigo is precipitated in union with vari- ous other substances, rendering it very impure. The best indigo of commerce, according to several analyses, contains only 75 per cent, of pure indigo, while some of the inferior kinds do not contain above 29 or 30 per cent. Part of these impurities may be dissolved in water, by alcohol, by dilute acids, and by alkaline leys. Berzeliiis found those impurities TESTIKG INDIGO. 277 to consist, besides a little iron, of clay, lime, magnesia, and silica, of a substance resembling vegetable gluten,* which may be obtained by digesting indigo in dilute sulphuric acid (vitriol); also a brown matter which he terms indigo brown, and which he obtained by digesting the indigo in strong pot- ash ley after the gluten had been extracted. He found like- wise a red resinous substance, which he termed indigo red ; it was obtained by boiling the indigo in alcohol, after digestion in the acid and alkali. Several experiments have been made upon the colouring properties of these substances, but the re- sults have sliown that they are incapable of being used as a dye. On the contrary, as we shall afterwards have occasion to remark, some of them being more soluble than the pure indigo, and much more easily decomposed, their presence is very hurtful, especially when the indigo is to be used as sul- phate of indigo. From the great differences in the quality of indigo, itwould be of the utmost importance to the dyer to have an easy method of ascertaining its true value. This, so far as we are aware, has not yet been obtained ; the various methods proposed generally imply formal analyses, which, however important they may be to the dyer, are too delicate and tedious to be generally adopted. The method universally practised in the dye-house is that of comparison — putting several samples to- gether, and breaking and comparing their clean surfaces. The best indigo generally is of the deepest violet blue, and the finest grain, and if scratched by the nail, it presents a copper hue ; but n*otwithstanding great care and long practice in judging of the value of indigo in this way, it often happens that the lot chosen turns out to be of inferior quality — a fact which is not discovered until it is in the vats. The process of Berzelius, just alluded to, is to take a weighed quantity of the indigo of commerce in very fine powder, and after digesting it in dilute sulphuric acid, to filter and wash it ; then digest what remains on the filter in strong potash or ammonia ; filter and wash again ; then boil the re- mainder in strong alcohol ; what remains is pure indigo, and, * Gluten is the substance which gives wheat, flour, starch, &c., the property of paste. It is a distinct vegetable substance composed of oxy- gen, hydrogen, nitrogen, and carbon, and it is the most nutritive of all vegetable compounds. 278 TESTING INDIGO. by weighing it, we find tlie per centage of real indigo in the sample. Another process, somewhat similar, was recommended by Chevreul. He treated the powdered indigo first with water, then with alcohol, and afterwards with muriatic acid. The following is the result of his experiment, taking a hundred parts : — ( Green matter united to ammonia "^ Treated with J A little deoxidized indigo f ,„ ^tq water. j Extractive C " (Gum ) m ^ J •.!- TGreen matter 1 Treated with I ^ed resin [ 30 - alcohol. \a little indigo j / Red resin 6 — Treated with J Carbonate of lime 2 — muriatic acid, j Red oxide of iron 2 — (^Alumina 3 — There fSilica 3 — remained, \ Pure indigo 45 — 103 — Although these processes give a much nearer and more certain approximation to the true value of indigo than the mere comparison of samples by the eye, still they are not direct enough, and require too much nice management to be resorted to generally in the dye-house. Those, indeed, who are most affected by a bad bargain, and ought to be most interested in any process that would enable them to avoid loss, and who have the requisite time and means to try such experiments, do not seem impressed with the importance of such inquiries. Another method has been proposed by Dr. Dana of Lowell, United States, for ascertaining the real value of commercial indigo. He directs that ten grains of indigo, reduced to a very fine powder, be put into a small glass flask, with two- and-a-half ounces, by measure, of a solution of carbonate of soda, of from oO*^ to 35° of strength by Twaddell's hydrome- ter ; after boiling for a few minutes, 8 grains of crystals of chloride of tin are to be added, and the whole boiled for TESTING INDIGO. 279 half an hour. By this means the indigo is dissolved, and the liquor appears of a yellow colour. Six grains of bichromate of potash, (red chrome,) are dissolved in G ounces of water ; and, when the flask is withdrawn from the lamp, this solution of chrome is added, which precipitates the indigo blue, along with a trace of the indigo red, leaving the other ingredients in solution. The whole is next to be poured upon a double (weighed) filter, and the precipitate washed with 1 ounce of muriatic acid diluted with o ounces of boiling water, and afterwards with hot water, till nothing but water returns. Then separate, dry, and weigh the filters, and make a note of the weight of the precipitate ; burn one filter paper against the other, and their difl'erence in weight is the quantity of silica contained in the indigo. This, deducted from the weight of the precipitate, gives the quantity of pure indigo. Mr. Walter Crum, who communicated the above to the British Association, in 1841, added that carbonate of soda with pro- toxide of tin, dissolves indigo, and forms a yellow solution, but so slowly, that he doubts if all the 10 grains are acted upon. He thinks Dr. Dana must mean soda-ash, which con- tains a notable quantity of caustic soda, but a much weaker solution of caustic soda would answer the purpose. Pure indigo, besides its great importance as a dye-drug, possesses some most important and interesting chemical pro- perties, but which are as yet not A^ery well understood. Some of these we shall notice before entering upon its practical value. If pure indigo be heated to about 550° Fah. it sub- limes, producing a beautiful transparent vapour of a reddish- violet colour, which adheres to the sides of the vessel in which it is sublimed, or on the top of the cinder left, in long needle-shaped crystals. Mr. Crum, whose investigations have thrown great light upon the chemical nature and pro- perties of indigo, employed for its sublimation the covers of two platinum crucibles, about three inches diameter, and of such a form that, when placed with their concave sides inwards, they were about three-eighths of an inch distant in the mid- dle. About the centre of the lower lid were placed thinly about ten grains of indigo, precipitated from the dyer's vat, in small lumps about a grain each ; then, having put on the cover, the flame of a spirit lamp was applied beneath the cover containing the indigo. The indigo immediately began 280 TESTING INDIGO. to melt with a hissing noise, which, when it had nearly ceased, the lamp was withdrawn, and the whole allowed to cool. On removing the cover, the sublimed indigo was found planted on its inner surface, and a little remained upon the charred mat- ter, and was easily removed. In this way he obtained from 18 to 20 per cent, of the indigo employed.* As few working men have access to platinum crucible covers to repeat this experiment, we may state, that it may be suc- cessfully repeated by taking a thin porcelain plate, or a sheet of iron or copper, with the indigo placed upon it, and covering it with a pretty large watch-glass ; when the plate under the indigo is heated by a lamp, the vapours very soon make their appearance ; and, towards the close, the glass appears bla'jk, owing to the coating of indigo which adheres to its inner sur- fiice. To obtain pure indigo for this experiment, the easiest method is to take a little of the yellow solution of the indigo vat. On adding to this a few drops of muriatic acid, to dissolve the salts of lime, the blue indigo falls to the bottom, and may readily be collected upon a filter, then washed and dried. Another method has been described by T. Taylor, Esq., which is as follows : — " Any quantity of indigo is to be reduced to powder, and mixed with about half its weight of plaster of Paris. To these materials so much water is to be added, as ^vill bring the whole to a thin paste. This is to be spread evenly upon an iron plate to the depth of the eighth of an inch, and allowed to remain exposed to the air, or to a gentle heat, until it is tolerably dry. If the heat of a large spirit-lamp be now applied to the under surface of the plate, the indigo begins to smoke, emits a disgusting odour, and in a few minutes is covered over with a dense purple-red A'apour, which condenses into brilliant flattened prisms, or plates of an intense copper colour, forming a thick velvety coating over the surface immediately exposed to heat. When this ceases to appear, the heat is of course to be withdrawn ; and when cold, the subhmed crystals may be readily lifted or swept off, without in the slightest disturbing the subjacent mass. The operation is exceedingly beautiful to look at, is effected in a few minutes, and any quantity of materials might be acted upon. For ultimate analysis, the sublimed indigo must be previously * Annals of Philosophy for Januarj-, 1823. TESTING INDIGO. 281 washed with alcohol or ether. The object of the plaster is to prevent the indigo from cracking during drying." * We have tried this experiment repeatedly, but the results did not promise favourably for the process being of practical value in the dye-house. Another method, and of much easier practice in the dye- house than any of these given, is by Henry Schlumberger : — " This test consists in dissolving the indigo in fuming sul- phuric acid, and decolourizing the solution, which has been diluted with much water, by means of chloride of lime. As this acts only on the blue-colouring substance, and not at the same time on the various other bodies which indigo contains, the quantity of chloride of lime requisite to produce decolour- ization agrees, as will be subsequently seen, accurately with the amount of colouring matter. " The operations in this experiment are as follows : — I pre- pare, in the first place, a portion of pure indigo or indigo blue by removing the scum which is continually formed on the blue vat, treating it with an excess of dilute hydrochloric acid, washing the deposit until all soluble parts have been removed, then drying it and preserving the indigo in well-closed bottles, in order to protect it from all changes in the moist state. In all my experiments this pure indigo serves as a standard, and for comparison with the results which the various kinds of indigo submitted to the test afford. Suppose the quantity of colouring matter in the pure indigo to be 100", I express the value of the tested indigo by numbers which indicate the per centage of pure colouring matter. In each experiment I employ the standard indigo for comparison with that of com- merce, as it is then not requisite to determine previously the amount of chloride of lime in solution ; besides which, the experiment is more accurate. In this case the causes of the differences in the results depend on circumstances, which always remain the same whether the standard indigo is employed, or the indigo the degree of purity of which is to be ascertained. Twenty grains of each kind of indigo is weighed off, which must be pulveinzed and finely ground ; half-an-ounce of fuming sulphuric acid is added, and the mixture is now rubbed together, the dish containing it being placed for four hours at a temperature of from 122° to 140°. • Chemical Gazette, vol. i., page 115. 282 TESTING INDIGO. " Meantime as many glasses, containing about a quart, are filled with distilled water as there are sulphate solutions, and to each solution of indigo is added its equal volume of water from the glass. The liquid becomes warm, upon which they are rubbed again ; water is then gradually added until the dish is full, when the whole is poured into the glass, and the dish washed with a portion of the water. Hereupon a solu- tion of chloride of lime is prepared of 2° Twad. in strength, and a given quantity taken, say 10 graduations of an alkaliraeter. " The well-stirred blue solution of the sulphate of indigo is now measured in an alkalimeter, a tube divided into 100°, and a portion poured into a dish, well stirred, and the entire quantity of the chloride of lime contained in the measure added at once. If the liquid immediately assumes a yellow colour, it is a sign of an excess of chloride of lime, and now sul- phate of indigo is added by degrees untU a faint olive-green colouring has been obtained. The experiment is now repeated, and the quantity of chloride of lime which had been found necessary in the fii'st case, added to the quantity of sulphate of indigo ; so that with one single mixing, there being neither an excess of chloride of lime or of sulphate of indigo, the Uquid acquires that tint at once. But when, after the first mixture, the liquid has retained a blue colour, which is a sign of an excess of the sulphate of indigo, fewer degrees of it are taken until the requisite tint has likewise been attained with a single mixing. " When the several indigoes have been treated in this man- ner, the following calculation is made to obtain the true value of the indigo which has been examined ; the goodness of the indigo is in inverse ratio to the quantity of sulphate of indigo employed in decolourizing. " Suppose, for instance, it were found that pure indigo required 54 parts of its sulphate solution to be decolourized by the fixed quantity of chloride of lime, and that, on the other hand, the indigo under examination required 64 parts of its sulphate solution, then according to the proportion — 100 X 64 64 : 54=100 : x, = x, or equal to 84"5, w'hich 64 ' ^ ' indicates the quantity of indigo blue contained in 100 parta of the iudiffo examined. TESTING INDIGO, 283 " It is important for the accuracy of the experiment that the pure indigo, and the kinds of indigo submitted to the test, should be equally moist, and it is therefore requisite to enclose all the samples as soon as they are taken out of the chests in glass phials, to prevent any attraction of moisture or desiccation previous to weighing. When a chest contains several kinds of indigo which exhibit slight differences in their tints, some pieces are selected which are separated into several lots, these are then powdered together, and the mean result taken as the correct one. But when, as often happens, a chest contains pieces of indigo of entirely different tints, it is best to examine the mixed sorts separately. " I also dilute the solution both of the sulphate of indigo and of that of the chloride of lime, since the experiment in this manner is less exposed to error than with concentrated solutions. Besides, it is easier when the liquid is only faint blue to distinguish the degree of decolourizatiun, when it must be discontinued. " Impure water, or such as contains salts of lime, produces a more or less considerable precipitate of the blue-colouring substance mixed with s\;lphate of indigo; it is therefore neces- sary to employ rain or distilled water. " The last stage of decolourization, or the point at which it is best to discontinue it, is the more easily ascertained, the purer the indigo, and the more complete its solution ; and in this case it is evident how sensitive the reaction of the chloride of lime is on the indigo; for a yellow solution of indigo, to which chloride of lime has been added, in which, therefore, there is an excess of chloride of lime, is rendered blue by a single degree of the indigo solution, a proof that this method will indicate a half per cent. In the commercial kinds of indigo it is less easy to fix the point at which decolourization must be discontinued, for in this case the decolourized liquid assumes an olive colour, and from 2° to 3° of the indigo solution must be added to change the yellow colour into the blue. " I have preferred the method of taking a fixed quantity of the chloride of lime and varying that of the sulphate of indigo, to that of making the sulphate of indigo a fixed quantity, and allowing the decolourizing agent to be diminished or increased, from its being possible to dilute the indigo solution with 284 TESTING INDIGO. much water, which has the advantage of rendering the degrees greater. ' ' Another method, and of much easier practice in the dye- house, is thus given by M. Reinsch : — Reinsch tried various modes of determining the goodness of indigo — such as the external appearance: the intensity of colour imparted to yarn by the cold vat; the quantity of indigo Wue obtained by subUmation ; the quantity of indigo blue deposited from the cold vat : and the specific weight. Not one of these methods, however, gave results to be relied on. " At last," he says, " I resorted to fuming sulphuric acid, and obtained the most satisfactory results. It is necessary, however, that the indigo should be pounded very fine, and the acid should be as concentrated as possible. I must also observe, that the solution of the Java indigo, and of that indigo which I prepared in a chemical way, by treating it with acid, caustic potash, spirit of wine and water, did not possess that pure blue colour like that of the Bengal sort, although I repeated the experiments several times, and could not,- therefore, determine anything with regard to the purified indigo. A dyer of great experience informed me, that for solution in sulphuric acid he prefers Bengal to the Java sort, as the latter is burnt by the acid, which is always the case when the indigo does not dissolve with a pure blue colour, but assumes a ci'imson hue on the sulphuric solution being poured in water. "The mode in which I proceed is as follows: — 2 grains of each sample of indigo are well pounded, mixed with four or five drops of fuming sulphuric acid, and rubbed with it until the whole forms a brown uniform mass. To this, 15 grains ot sulphuric acid are added, and triturated till it produces a clear green solution, whereupon other 15 grains of fuming sulphuric acid are added ; lastly, this solution is gradually mixed with 150 grains of water. Two glass cylinders of equal length and width are now divided each into twenty equal parts, and 15 grains of the sulphuric solution (which is best measured by a glass tube closed at one end) poured into one and mixed with water, till the solution is of a light-blue colour and trans- parent ; if 15 grains of the solution do not produce sufficient colouration, a small quantity more of it is added, till the cylin- TESTING INDIGO. 285 der is filled with the light-blue solution. I generally com- mence with the apparently best indigo. After this the second cylinder is filled in the same way with an equal quantity of sulphuric solution of the same indigo sample and water, in order to see whether the two solutions are equal in colour. If this be the case, one of the cylinders is emptied, and an equal quantity of sulphuric solution of an inferior sample poured into it and gradually diluted with water, till the solu- lutions in both cylinders are perfectly alike in colour. Care is to be taken that the colouration be not too intense nor too light, it being in either case difficult to obtain both solutions of the same hue. For discovering this equality the eye will also be much assisted if the relative position of the cylinders is changed from the right to the left, or by placing them alternately before or behind one another. As soon as the colour of both is thus found to be equal, the quantity of water is examined which has been poured into the second cylinder. Supposing now that 15 grains of sulphuric solution have been employed in either of the cylinders, but the quantity of water which produced the equal colour was in the first or standard cylinder 20 parts, and in the second only 15 parts, then the sample of which the latter solution was made will contain TsV^is, or one quarter less of colouring matter. "This method is so easy and convenient, that everybody can avail himself of it. All that is required is to keep ready a certain quantity of indigo solution of a known quality as standard solution, and then to prepare a sulphuric solution of the indigo to be tested. "The above-described method may even be made more accurate if longer glass cylinders are used, so that the per centage quantities may be indicated. The glasses must then be divided in 100 parts. The larger the degrees are, the more accurate will the results be. " I have yet to add some observations with regard to an adulteration practised on the indigo, and which is of impor- tance to the druggist. Each large indigo-chest contains a quantity of dust, which is said to amount sometimes to 8 or 10 pounds. This dust is an artificial product, composed of starch or white lead and powdered indigo, and is put in the chest in order to increase its weight." Another process of testing the value of indigo has been 286 TESTING INDIGO. recommended by Dr. Bolley, depending also upon the deco- lourizing by chlorine, by a method which insures the con- stancy of the chlorine, this is done by using hydrochloric acid and chlorate of potash. A given quantity of indigo, say 200 grains, is ground into powder, and converted into sul- phate of indigo by adding to the 100 grains about 2^ ounces of the strongest sulphuric acid, and allowing it to stand for six or eight hours. The whole is now put into an evaporating basin or flask, with about one pint of water, and one quarter of an ounce, by measure, of hydrochloric acid, and brought to boil. A solution of chlorate of potash is now made in 100 measures of water by alkalimeter, (which is added to the indigo solution), the blue liquor passes into green, brownish-green, and lastly into red, when the operation is finished. A little experience will show the exact time to stop. The amount of chlorate solu- tion taken to effect this is noted, and a standard solution being made, the relative value of indigo will be easily ascertained. Another method of testing the value of indigo has been recently recommended by Dr. Penney of the Andersonian Uni- versity, Glasgow, based upon the circumstance that indigo blue, in presence of hydrochloric acid, is decolourized by bichromate of potash. Ten grains of the sample, in very fine powder, are dissolved in 2 drachms, by measure, of fuming sulphuric acid, forming sulphate of indigo. After standing several hours, to insure complete solution, it is diluted with a pint of water, and the whole well stirred, after which there ia added f of a volume ounce of hydrochloric acid. Seven and a-half grains of dry and pure bichromate of potash are now dis- solved in water — the whole solution to be equal to 100 measiu-es of an alkalimeter ; this is added drop by drop to the sulphate of indigo, until the blue colour disappears, and the colour of a drop of the solution put on a white plate or paper be orange-brown, having no green or blue tint. The number of graduations required to effect this is noted. Dr. Penney found that 7J grains bichromate of potash were equal to 10 grains pure indigo, so that every 10 graduations of the solution taken to decolour the sulphate, are equal to 1 grain of pure indigo, or 1 gra- duation to a per cent, of indigo. Commercial indigoes.— The following description of Com- mercial indigoes is taken from Dumas' Lectures upon Agriculture : — COMMERCIAL INDIGOES. 287 '^ Indigoes of Commerce. — The indigoes of commerce have been described ia a very able manner by M. Chevreul. The following details are extracted from his work : — They are sometimes in small, light pieces, of a violet-brown colour, and sometimes in cubical loaves. These loaves may be considered good, when they assume a copper-coloured aspect on friction with any hard and smooth body — when there are no cavities found in their interior, presenting a series of brown or whitish- coloured streaks — and, lastly, when they are free from fissures externally. If they are of a blue instead of a violet colour, it is a proof that they contain more or less of the yellow matter. The presence of this matter in large proportions, tends by its admixture to convert the blue into a green, and also neutral- izes the colour of the red matter of indigo. An obscure dark brown or dirty-green colour indicates, in general, that the indigoes have undergone some deterioration in their prepara- tion or during their transport. Indigo is destitute of odour, provided it has undergone no alteration by heat and moisture. Indigoes are classified into different kinds, according to the country in which they are prepared, or according to their colour. " First, Indigoes prepared in Asia — they are from Bengal, Coromandel, Madras, Manilla, and Java : — ^'■Berjgal Indigoes. — The trade in this indigo is chiefly carried on in Calcutta, and through the medium of the East India Company ; its varieties are very numerous. The principal, commencing with those of the best quality are: — 1** The superfine or light blue. This is in a cubical form, light and friable, soft to the touch, of a clean fracture, and giving a beautiful copper colour on being rubbed with the nail. 2° Superfine violet. 3° Superfine purple. 4° Fine violet, in colour a little less brillant than the superfine, and rather hea\'ier. 5° Fine purple violet. 6° Good violet, somewhat heavier than the fine violet. T Violet red. 8° Common violet. 9° Fine and good red, heavier than the preceding, colour bordering decidedly on red. 10° Good red, of a firmer and more compact structure. 11° Fine copper- coloui'ed, redder and more compact still. 12° Middling copper-coloured. 13° Ordinary and low copper-coloured ; this is of a copper- coloured blue or red, somewhat difiicult to break. " Coromandel. — Those of the best quality correspond to the 288 COMlklERCIAL INDIGOES. middling Bengal indigoes, and are met with in square masses, having an even fracture, but are more difficult to break. The inferior indigoes are heavy, of a sandy feel, having a blue colour bordering on green or gray, or even black ; often in very large squares, and covered with a slight crust or rind of a greenish-gray colovir. These are the most difficult to break of all the indigoes of commerce. " Madras. — They have a grained rough fracture, and are of a cubical figure. The superior qualities have no rind; in figure they somewhat resemble a hat, and are more light and friable than those of Coromandel. These indigoes, when of the best quality, have great lightness, but are not equal to the superfine blue of Bengal. The middling qualities have a verj' shght copper colour. The colour of the inferior quahties is a dark or muddy blue, black, or even gray, and greenish. ^'■Manilla. — These present the mark of the rushes upon which they have been dried. They are of a finer consistence and hghter colour than are the indigoes of Madras, but not so fine as the indigoes of Bengal. The better quahties are often in flat and elongated masses, somewhat porous, and conse- quently light. The middling quahties are of a violet colour, but they are inferior to the violet of Bengal. " Java. — In flat, square masses, sometimes of a lozenge shape. The superior quahties appear to the sight as fine as the blue, violet, or red indigoes of Bengal ; but they are not so in reality. " 2°. Indigoes prepared in Aftica. They are firom Egypt and Senegal : — ^^ Egypt. — The superior qualities of Egyptian indigo are superfine and fine violet blues. They are light, but their structure is not very fine, and they often contain sand. The squares are rather flatter than those of Bengal. " Senegal. — They are of good quahty, but they contain more earthy matter than any other indigoes in the trade. " 3°. Indigoes from America ; those of Guatimala, Caraccas, Mexico, Brazil, Carolina, and the Antilles : — "The indigoes of Guatimala, of the Caraccas, and of Mexico, are of various kinds. The best are of a bright blue colour, remai-kably light and fine. These indigoes are esteemed equal to the best Bengal. The inferior quahties are of a violet colour, but, in general, are more mixed than the Bengal kinds. CHARACTERISTICS OF INDIGO. 289 " Brazil. — These indigoes are in small rectangular paral- lelepiped masses, or in irregular lumps, of a greenish-gray colour externally, and having a smooth fracture, a firm con- sistence, and a copper- coloured tint of greater or less bril- liancy. " Carolina. — In small square masses, having a gray exterita-. The best qualities have a dull copper colour, bordering on violet or blue. The common qualities are almost always of a green- ish-blue ; they are rarely found of a copper colour. "The principal varieties of indigo in commerce are the Bengal, the Caraccas, the Guatimala, the Madras, and the Manilla. " Besides the numerous shades already described, we should also be on our guard against certain defects, of greater or less consequence, and which depend on causes acting either on the indigo when already prepared, or else occurring during its preparation. The following are some of the characters to be borne in mind : — The large or small fracture : squares of indigo reduced, by accident, into lumps of variable size. Fragments : squares reduced into irregular pieces, and fine enough to be passed through a sieve. Sometimes, also, we meet with squares which are readily broken, and which pre- sent a whitish kind of mouldiness in their interior. Gritty lumps, throughout which are points presenting the appearance of granite. Streaky masses, in which are layers of various shades of blue, placed one above the other, in the same square. Pieces of a scorched appearance, which, on being sharply rubbed between the hands, are ground into small fragments, nearly black in colour. Sandy lumps, in the interior of which the eye can detect shining specks, which are nothing more than sand." Pure indigo, whether obtained by sublimation, or other chemical means, is of a deep blue, approaching to violet. If scratched or rubbed, it has a strong copper hue, and a metallic lustre. It has neither taste nor smell, and is remarkable for its neutral properties. It is insoluble in water, alcohol, ether, alkalis, and dilute acids. Strong sulphiu-ic acid dissolves indigo readily, and forms Avith it a purple-blue solution. Its chemical composition is, according to Mr. Crum and M. Dumas : — 290 INDIGO. 16 Carbon. \ /■ 32 Carbon. 5 Hydrogen. ( ^^ ^^^^^^^ J 10 Hydrogen. 2 Oxygen. C ' ) '^ Oxygen. 1 Nitrogen. ) (^2 Nitrogen. The double proportion is preferred, as it agrees better with some of the reactions to be afterwards explained. The chemical qualities, and some of its reactions, have been extensively studied. If blue indigo be brought into contact with substances having a strong attraction for oxygen in the presence of an alkali, the indigo is reduced to the white state, and becomes soluble in the alkali ; this, as is well known, is the principle of the blue vat. The following matters all reduce blue indigo to white : — Protoxide of tin. The sulphurets of potassium. Protoxide of iron. Sodium, Sulphuret of arsenic. Calcium, Phosphorus, Sugar, The phosphites. Starch, Sulphites, Tannin. Salts, which yield oxygen, as those of copper, tiirn white indigo to blue, and the copper is reduced to the suboxide. Water having carbonic acid, also oxidizes white indigo. Indigo white is a crystalline solid, having a fibrous silky lustre, tasteless, without smell, and heavier than water ; it is insolu- ble in water, but soluble in alcohol and ether. White indigo, well dried, may be kept in the air for several days without change, but if moist it soon becomes blue ; when heated it becomes purplish-blue. The composition of white indigo is still, to some extent, an unsettled question. Accord- ing to the most generally received opinion, white indigo is blue indigo with less oxygen, sometimes called deoxidized indigo, but Dumas considers it as blue indigo, with an equi- valent more of hydrogen : — thus we have By the Common Theor>'. By Dumas's Theory. Carbon 16 Nitrogen 1 Hydrogen 5 Oxygen .... 1 Carbon 16 Nitrogen 1 Hydrogen 6 Oxygen 2 Dumas supports his view of the matter by reference to INDIGO. 291 many vegetable organic substances which he thinks comport themselves in a similar manner, and gives a series of formulae of compounds, which by analogy he connects with indigo. Thus : — c. H. 0. H. N. Blue indigo (double atom) 32 10 2 2 White indigo 32 10 2 2 2 Acetyle 8 6 2 Aldehyde 8 6 2 2 Benzule 28 10 2 Oil of Bitter Almonds 28 12 2 2 Cinnamule 36 14 2 OilofCassia 36 14 2 2 Here we observe a series of compounds differing more widely from each other than white and blue indigo, and only caused by having 2 proportions more of hydrogen. A like analogy is carried out between compounds of indigo with other bodies, and compounds of other organic vegetables, which, however, we must pass over. Liebig's view of the reaction of indigo, and its relations to other bodies, differs from that of Dumas. He considers, as the result of careful and extensive investigation, that indigo contains a salt radical (page 33) which he terms anyle, and which is composed of Cjo H^ N. This, it will be observed, is indigo without any oxygen. He then considers that white indigo is the hydrated protoxide of this base or radical, and that blue indigo is the peroxide. Thus : — C. H. N. 0. Water. Anyle 16 5 1 White indigo 16 5 1 1 1 Blue indigo 16 5 1 2 Taking double proportions for comparison : — Anyle 32 10 2 White indigo 32 10 2 2 2 Blue indigo 32 10 2 4 This view of the matter, which we think most consistent with fact, and to which we may have occasion to return in describing the vat, can be supported by analogies in the same manner as the other view. Indeed, most of the colouring: 292 INDIGO. principles of vegetables, such as madder, annotta, archil, &c., exist in the plants as colourless bases, and become coloured by the absorption of oxygen. M. Pressier, who has been very fortunate in his researches into vegetable colouring mattei's and bases, thinks that he has found a decisive argument in favour of Liebig's view, in the fact that blue indigo, sugar, and potash react together, and form white indigo. He therefore considers it very improbable that indigo should extract hydrogen from water, at the same time that the oxygen of the water would combine with the hydrogen of the sugar to reproduce water. Dumas, however, observes upon this, that there is no necessity for supposing water to be decomposed, as the hydrogen of the sugar may combine directly with the indigo blvie and form indigo white. These views of the question show that the svibject is still one of difficulty, and is fuU of interest ; and that the daily experi- ence of the dyer, were the results carefully observed, might afford important aid towards the solution of some of those vexed questions of chemical science. If indigo be thrown into fused hydrate of potash, its blue colour disappears; it dissolves, and is partly decomposed along with the water of the alkaline hydrate ; hydrogen, and am- moniacal gases are evolved, while carbonic acid, and another acid, named valerianic acid, having properties similar to acetic acid, are formed, and combine with the potash. By digesting this mixture with a little sulphuric acid, the alkali combines with it, and the new acid crystallizes. This acid combines with alkalis, and other bases, and forms a very interesting series of salts. If indigo, in fine powder, be added to nitric acid, diluted with seven or eight times its weight of water, and a gentle heat be applied, it dissolves with effervescence, forming a yel- low liquid. After standing a little, this liquid may be decanted from any resinous matter formed during the process, and con- centrated by evaporation, and speedily there will be found deposited a quantity of yellowish-white crystals, having a sourish-bitter taste, and requiring about 100 parts of cold water for their solution. This was formerly termed indigotic acid, but is now called anilic acid, from the species and name of one of the plants which yield indigo. It combines with all known bases, forming salts, which have generally a yelloAV PICRIC ACID. 293 colour. It ^ves a blood-red colour to solutions of the per- salts of iron. If indigo be added to strong nitric acid, and heat be applied, it quickly dissolves, evolving a great quantity of nitrous gas. On allowing the liquid to cool, a large quantity of semi-ti'ans- parent yellow crystals are formed, having a very bitter taste. This is what was, till lately, called carbazotic acid ; but this name has been changed to picric acid. To procure it in a purer state, the crystals obtained by the above operation are to be washed in cold water, and then boiled in water sufficient to dissolve them ; next filtering the liquid and allowing it to cool. The acid again crystallizes in brilliant yellow prisms. The acid may also be obtained by the action of nitric acid upon anilic acid. Picric acid is very permanent in its constitution. When fused in chlorine or with iodine, it is not decomposed, nor does a solution of chlorine affect it. Cold sulphuric acid has no action upon it, but dissolves it when hot. Boiling hydrochloric acid does not act upon it, but nitro-muriatic acid {aqua regia) dissolves it with difficulty. It acts like a strong acid upon metallic oxides, dissolving them, and forming peculiar crystal- lizable salts. These are yellow ; they detonate strongly when sharply heated, and also by percussion, particularly the salt formed with potash. "N^lien a little of it is gradually heated in a glass tube, it first fuses, and then suddenly explodes, breaking the tube to pieces. Care is necessary in making this experiment, as the fragments of glass may injure the face. This acid is an excellent test for the presence of potash in any fiuid, a solution of it in alcohol producing a bright yellow crystalline precipitate, even in a diluted solution of the alkali. It is thus more sensible than the chloride of platinum, commonly employed for the detection of potash ; for that re-agent does not produce a precipitate in dilute solutions. When indigo is acted upon by very diluted fuming nitric acid, it unites with two atoms more of oxygen, and is conse- quently converted into a new substance, which has received the name of isatine. This substance under the influence of alkalis, absorbs one equivalent more of water, and assumes an acid character, and is termed isatinic acid. This acid combines with other substances forming a series of compounds, the nature of which is not yet veiy well known. 294 INDIGO. Chromic acid has a similar action upon indigo as nitric acid. When indigo in the dry state is brought into contact with dry chlorine, no chemical action is observed ; but when indigo, suspended in water, is subjected to the action of chlorine, several new products are formed. When the fluid thus acted upon is distilled, a fluid product in minute quantity passes over with the distilled water, and collects under it in the receiver in the form of white scales, which has been termed chlo7'indoptin. It is sparingly soluble in water, but copiously in alcohol. The substance which remains in the retort is found to be a mixture of several new products. On being dissolved in boiling alcohol, it yields, on cooling, red prismatic crystals of a bitter taste, and very insoluble in water ; this has been named chlorisatin. It dissolves in a solution of caustic potash, producing a red colour. The salts of lead give with this solution a yellow precipitate, which becomes a fine scarlet by standing. The salts of copper, (blue-stone,) &c. give a brown, which becomes blood-red by exposure to the air. In the alcoholic solution, another substance is found having an equivalent more of chlorine than that named above ; this is termed hichlorisatin. Its properties, however, are analogous to those of chlorisatin ; its solution in potash gives a yellow precipitate with the salts of lead, but does not alter by expo- sure to the air ; and with the copper salts it gives a yellowish- brown, which passes to blood red. When chlorine is passed through a solution of chlorisatin, another substance named chloronile is formed. This crystallizes in scales of a brass- yellow colour, and when dissolved by potash gives a beautiful purple colour. If indigo in powder be added to a solution of caustic potash of specific gravity 1'35 (70 Twaddell) and boiled, an orange- yellow salt is formed. Tlie solution of the boiled mass becomes blue in the air from absorption of oxygen, like a solution of white indigo, and blue indigo precipitates. Besides the compounds resulting from the action of nitric acid and chlorine upon indigo, there are several others which from their true characters being still little known, we have not thought it necessary to enumerate. Some practical dyer may indeed be inclined to ask, what those already noticed have to do with dyeing? We are sorry that with respect to some of them, we cannot give any satisfactory answer to the INDIGO DYEING. 295 question ; but the same question was asked, when chemists first intimated that chromic acid produced yellow salts when combined with lead ; yet this simple hint has completely revolutionized various departments of dyeing ; and the action of chromic acid upon indigo, as already observed, has been both a source of annoyance and advantage to the dyer. Pre- vious to the use of alkaline solutions of lead, dyers seldom could get an evenly chrome green ; the chromic acid being set at liberty acted upon the indigo which was upon the yarn, destroying in part the blue colour, after which the green was all light-yellow hlains. These annoyances are still felt where the new process of working the lead solution with an alkali is not practised. But this same action of chromic acid upon indigo has been taken advantage of by calico printers, when they want a white pattern on a blue ground. Previous to the introduction of bichromate of potash for this purpose, the calico printers were, to a certain extent, limited. Thus : — The pattern is printed upon the cloth with the oxide of a metal which yields its oxygen easily to other substances, such as copper and zinc ; the goods are afterwards dyed blue by passing them through the vat; but the parts upon which these metallic salts are printed, resist the dye, by yielding their oxygen to the indigo, a process which will afterwards be described, so that the piece when finished is a blue ground with a white pattern. But after the blue vats have been wrought for some time, they cannot be used for this purpose, owing to the weakness of the dye, and the consequent length of time necessary to produce the required shade. So that these resist pastes are in a manner washed off, and the pattern spoiled. Now, in place of throwing out as useless, vats thus exhausted, as was formerly done, the cloth is dyed blue without resists, and after being slightly scoured and washed, it is passed through a strong solution of chro- mate of potash, and dried in the shade ; the required pattern is then printed on the cloth with a mixture of oxa- lic and tartaric acids made into a paste by gum or clay. The potash in union with the chromic acid is taken up by these acids, and the chromic acid being set at liberty, acts on the indigo, and a white pattern is produced. This ingenious pro- cess was discovered by a German chemist. 296 INDIGO. The following table exhibits the composition of those sub- stances which we have briefly described as resulting from the action of nitric acid and chlorine upon indigo. It may be required for reference : — Xame. C. H. 0. X. C. Water. Indigo 16 5 2 10 Isatine 16 5 4 10 Isatinic acid 16 5 4 10 1 Anilic, or indigotic acid 14 4 9 10 1 Picric, or carbazotic acid... 12 2 13 3 1 Chlorindoptin 16 4 2 4 Chlorisatin 16 4 3 110 Bichlorisatin 16 4 3 12 Chloranile 6 2 2 Valerianic 10 9 3 1 The only substance which dissolves indigo, without destroy- ing its colour and composition, is highly concentrated siil- phuric acid. For this purpose the ftiming acid of Xordhausen is preferable, (page 92,) as when otlier acid is used, a greater quantity of it is required. The substance formed is popularly known by the names of sulphate of indigo, Saxon blue, China blue, and extract of indigo. The action of sulphuric acid upon indigo is found to be something more than a mere solu- tion : a chemical combination, in definite proportions, residts, forming two distinct substances, differing considerably from each other in their properties. These two compounds were discovered and described by Mr. Crum, and called by him cerulin and phinacin, from their colours — the former blue, and the latter pui-ple. They have been since named sulph-indyUc acid, and sulpho-purpuric acid. The former, which consti- tutes the blue principle of Saxon blue, is formed most abun- dantly when the sulphuric acid is sutficiently strong and abundant, and other proper means attended to. Its composi- tion is found to be one atom of indigo combined with two of sulphuric acid. The other is the principal product when the indigo preponderates. It is of a purple colour ; and when the solution is diluted with water, it precipitates. Its composition is found to be equal to one atom indigo to one of sulphuric acid. From the nature and properties of these two substances, it is evident that every care shovdd be taken to convert the SULPHO-PURPURIC ACID. 297 indigo into sulph-indylic acid, and to avoid the formation of sul- pho-pui'puric acid. The circumstances under which this latter acid is formed are — first, too little acid in proportion to the indigo, and secondly, too little time allowed for digestion. The general proportions used by dyers vary from three to five pounds of acid to the pound of indigo. This is by far too little, and occasions a considerable loss of indigo by the preci- pitation of the sulpho-purpuric acid, when the solution is diluted with water. Close observation shows that it requires from six to eight pounds of concentrated sulphuric acid to convert a pound of indigo into blue sulph-indylic acid. From some investigations lately made by M. Dumas, indigo requires even a larger proportion of acid to convert it into sulph- indylic acid. He recommends no less than fifteen parts of acid to one of indigo. This quantity, however, we have found to be of no advantage in practice, but rather the opposite, particularly when the acid is to be neutralised before the indigo solution is used, which is the general custom in dyeing cotton. We have said that the second circumstance under which sulpho-purpuric acid is formed is that of too short time being given for the indigo and acid to digest. When indigo is first put into the sulphuric acid, there seems to be an immediate solution ; but if a drop be spread upon a window pane, it appears of a dirty-green colour ; and if allowed to stand for a little upon the glass, a yellowish-coloured liquid begins to run from the blue mass, occasioned, no doubt, by the acid absorb- ing moisture, and separating itself from the indigo, and clearly showing that the change upon the indigo by the acid is not an immediate effect. The more impure the indigo, the darker and greener appears the substance when put upon the glass. After the mixture has stood two or three hours, and tried in the same manner, it appears of a reddish-purple colour — the principal compound existing now in the solution being sulpho- purpuric acid. As the liquid stands, it begins to assume a violet shade, and finally passes to a deep rich blue. But dyers seldom obtain it in this state : in their hands it gene- rally has a reddish tinge. Mr. Crum found that when the solution is diluted with water, after the colour has become of a bottle-green, the action of the acid is stopped, and sulpho- purpuric acid only is formed. But there are other meaas by o2 298 INDIGO. which the action of sulphuric acid upon indigo may be stopped, than by directly diluting the solution with water. As already intimated, it is only the highly concentrated sulphuric acid wliich converts indigo into sulph-indyhc acid. Now, dyers not unfrequently alter the strength of their acid by the pro- cess of mixing and preparing theii- chemic, (the technical name for sulphate of indigo.) This is very generally done in an open -wide-mouthed vessel, which is allowed to stand un- covered, probably in the midst of the steam and vapours of the d3'e-house ; or, in some cases, the vessel is put into a boiler, or tub with boiling water. By these injudicious means, the sulphuric acid, which absorbs water very rapidly, is diluted below the necessary strength for dissolving indigo ; and the result is, the formation of sulpho-purpuric acid, instead of sulph-indyhc acid, which is the real substance wanted. Another caiise of the stopping of the action of the acid by dilution is, from the indigo. Ground indigo absorbs a quan- tity of moisture ; and if it be not thoroughly dried previous to putting it in the acid, the acid is too much weakened to effect the formation of the substance required. There ai-e other causes by which the preparation of chemic is injured. Sometimes the acid and indigo are mixed together at once, and by this means the heat evolved is sufficient to decompose the impurities of the indigo. Part of the acid also suffers decomposition, and a great quantity of sulphurous acid gas is given off — so much, indeed, that the head cannot be held above the vessel for any length of time without injury. Another practice is, for the sake of quickening the operation, to place the vessel upon the flue in the stove, and keep the solution for hours at a heat upwards of 300° Fah. The gas given off in these cases is sometimes so great as to destroy the colours of goods hanging in the stove. Indigo submitted to such treatment is seldom found good : often its appearance on white paper or glass (which is a general method of testing the quality of sulphate of indigo) is a blackish -green — sometimes a dirty pui'ple — seldom the fine blue violet — scarcely ever the beautiful blue. Although the sulpho-purpuric acid is precipitated when water is mixed with the solution of sulphate of indigo, and is insoluble in dilute acids, it is, when freed from the sulphuric acid, soluble in distUled water ; but if any substance be in SULPHATE OF INDIGO. 299 the water — and common spring water is never pure — it is less soluble. It dissolves in alkalis, and in solutions of the alkaline earths, giving a blue colour, of greater or less purity, according to the nature of the solvent. We have found the following method of preparing sulphate of indigo, in quantities for use, very satisfactory: — The indigo is reduced to an impalpable powder, either by grinding in a mortar or a mill, and completely dried, by placing it upon a sandbath or flue for some hours, at a temperature of about 140° or 150° Fah. For each pound of indigo, six pounds of highly concentrated sulphuric acid are put into a large jar, or earthen pot, furnished with a cover. This is kept in as dry a part as possible, and the indigo is added gradually, in small quantities. The vessel is kept closely covered, and care taken that the heat of the solution does not exceed 212° Fah. When the indigo is all added, the vessel is placed in such a situation, that the heat may be kept at about 150° Fah., and allowed to stand, stirring occasionally, for forty-eight hours. These pre- cautions being attended to, we have uniformly found that any failure occurring was clearly traceable to impurity of the indigo, or weakness of the acid used. The dyer now very seldom prepares his own sulphate of indigo ; it is manufactured for him, and sold in the market as indigo extract^ which, when properly prepared, is a superior article to that prepared by himself The following is the process of its manufacture : — The indigo is dissolved in the sulphuric acid as described ; it is then diluted with hot water — distilled water is best ; the whole is put upon a filter of woollen cloth, by which means the insoluble impurities of the indigo are separated. The blue solution which has passed through the filter is transferred to a leaden vessel, and evaporated till reduced to about three gallons for every pound of indigo used. There is then added about 4 lbs. of common salt to the pound of indigo, and the whole is well stirred. The sulpho-indylic acid is thus precipitated, and the whole is again thrown upon a similar filter of woollen cloth ; the extract remains upon the filter, and, when suiliciently drained, is ready for the market. Some makers add a little potash or soda, which may be advantageous, and a little ammonia gives the extract a beautiful bloom. A pound weight of good indigo should yield 14 lbs. of extract. The adulterations in this solution are various. 300 INDIGO. Some of the insoluble matter is occasionally added, but not often, as it deteriorates tlie appearance of the extract. The addition of a little lime or barytes, gives an insoluble precipi- tate, which adds weight to the extract ; but all practices of that kind react upon the maker ; for, although the dyer may not have methods of testing his stuff, he very soon ascertains its working value by experience. The extract of indigo is used in the dye-house in the same Avay as the sulphate was used before this method of prepara- tion was adopted. The general term of chemic is applied to both, and chemic blue is used in various operations. For dyeing silks and woollens blue, the extract is simply diluted, and the goods merely passed through it ; but this method cannot be adopted with cotton, as its fibres have no affinity for sulphate of indigo. But although not used for dyeing blue upon cotton, it is extensively used for dyeing green upon hght goods of that material. When the cloth is dried from the sulphate of indigo solution, the acid of the chemic must be neutralized : for this purpose the chemic is prepared dif- ferently. The extract is put into hot water — the exact quan- tity is not material — and well stirred; to this solution a quantity of pounded chalk or whiting is added gradually, vmtil the acid is exactly neutralized ; this is a nice operation, and requires great care on the part of the operator ; for, were the acid property to prevail in the least, it would destroy the yellow upon the cloth to be dyed green ; and were the alka- line matter predominant, it would brown the yellow, and the green would assume a blackish-oUve shade. Thus the beauty of the colours depends upon the dyer being careful to stop just at the turning point. The only method employed by dyers for determining the point of neutrality is the taste; and this, from many circumstances which we need not enumerate, is liable to error ; and when the dyer is deceived, the results are very anno}dng, and also expensive. Were very deUcately prepared blue and red htmus-papers used, the results would be much more certain. However, the reader may be astonished when we inform him, that failui*es from this source are very seldom. Some dyers use carbonated alkalis, such as soda and potash, to neutralize their acid ; and no doubt when any of these are used, the sediment at the bottom is much less; but we have always thought that owing to the salts formed by these THE BLUE VAT. 301 alkalis being dissolved in the blue solution, the green colour is not so good, especially when hark is the yellowing substance. The process of dyeing greens by this sort ' of prepared chemic is as follows: — The goods, after being well boiled and washed, are put through a dilute solution of pyrolignite of alumina of specific gravity 1-035, that is 7 of Twaddell, and washed from this through hot water ; they are then wrought through a decoction of quercitron bark, ovflavine. When suf- ficiently yellow for the shade of green required, they are then wrought through a quantity of chemic mixed with cold water ; wrung from this and dried. If fustic is the yellowing substance used, alum is a better mordant. The greatest portion of the indigo imported is used for dye- ing blue by means of the blue vat. A\'e have already men- tioned that indigo is insoluble, except in strong sulphuric acid ; but if it be by any means deprived of an atom of oxygen, (ac- cording to the common theory,) it is soluble in alkalis. It may be said, that, according to the law of definite proportions described in our first article, it cannot be indigo with an atom less of oxygen. Neither is it ; and we see that it has different properties from common indigo, for it is soluble even in weak alkalis ; has a powerful attraction for oxygen ; and is of a white colour. This substance has been termed tndigogen, and it may be observed, that the nature of the blue vat depends upon the introduction of substances capable of extracting oxygen from the indigo, and converting it into indigogen. The substances generally used for this conversion are the protoxides of iron and tin, orpimeut (sulphuret of arsenic,) and organic sub- stances. These last produce the desired effect by their decom- position, such as in the woad vat, where, by the fermentation of the woad and madder, the oxygen is extracted from the indigo, which is thus converted into indigogen. The indi- gogen is dissolved, as it forms, by the potash put into the vat. What is termed the common blue vat, or lime vat, is made up with indigo, lime, and sulphate of iron (copperas). But before describing the nature of this vat, it will be necessary, at the risk of a little repetition, to refer to the properties of oxide of iron (page 152.) The protoxide of iron, especially when in contact with mois- ture, has a strong attraction for more oxygen so as to pass into the peroxide. When the sulphuric acid of copperas is neutra- 302 IXDIGO. lized by au alkali, the iron is left in the state of a protoxide. The blue vat is made up by putting lime, copperas, and indigo into a vessel filled with water, and stirring occasionally for a day or two, when the indigo is dissolved. Thus : — When finely ground indigo is put into a vat with a mixture of lime and sulphate of iron, the first action which takes place is the decomposition of the metalhc salt; the acid, which is in union with the iron, combining with a portion of the lime, forms sulphate of lime and oxide of ii'on. The detached oxide of iron extracts more oxj'gen from the indigo, converting it into indigogen, (white indigo,) and the peroxide of iron and the sulphate of lime thus formed are precipitated, forming what is technically termed sludge. The remaining portion of lime dis- solves the indigogen, and forms with it the solution required. The following diagram represents this action and the results more clearly, and gives one view of the theory of the blue vat : Indigo, com- r Indigogen _Dyeing solution. posed of... \Oxygen / Oxide of iron.. _^^ .^ fy ) Oxide of iron y^^i:::===.Peroxide of iron. 2 Copperas.. < o i i • -j ^^ \ bulphuric acid \ Sulphuric acid , / Lime 3 Lime < Lime ^. Sulphate of lime. ( Lime _ ^ Sulphate of lime. It wiU be observed that this theory of the vat is founded on blue indigo being an oxide, but, according to the view which Dumas takes of the constitution of indigo, the action which takes place in the vat mil be somewhat different from that given above. When the lime combines with the acid of the copperas, the iron decomposes a portion of water combin- ing with the oxygen, and the hydrogen combines with the indigo forming indigogen, which may be represented as fol- lows : — THEORY OF THE BLUE VAT. 303 < ludigo Water /Hydrogen \ Oxygen ( Lime ,< Lime (^Lime Oxide of iron Oxide of iron Sulphuric acid Sulphuric acid Indigo . 3 Lime. 2 Copperas. Indigogen, forming dyeing solution. Peroxide of iron. Sulphate of lime. Sulphate of lime. This theory is equally, if not more beautiful, than the former, but in some cases it is scarcely reconcileable with our chemical experience. Wlien the goods are put into the vat, the dissolved indigogen combines with them, and when brought into contact with the air, according to the former theory, the indigogen combines with oxygen, for which it has a strong disposition, and blue indigo is formed, and remains combined with the cloth, but according to the latter theory, the blue indigo is left in combination with the cloth by the hydrogen combining with the oxygen of the atmosphere, and forming water. The supposition that hydrogen should combine with the free oxygen of the air, and form water so rapidly under such circumstances as mere exposure, is somewhat anomalous, but this is no reason for rejecting it. If a mixture of copperas and lime be put into a bottle with distilled water, the water is not decomposed ; the lime combines with the acid, which, along with the iron, is precipitated, and if the air be com- pletely excluded, the iron remains as a protoxide for days ; indeed, the change from a protoxide to a peroxide, is so slow, that a long time elapses before it is appreciable ; but if indigo be added, even after the mixture has stood for some time, the action of the common vat proceeds. This, according to Dumas's theory, gives a beautiful illustration of relative affini- ties. Before the indigo is introduced, the attraction of the iron for oxygen is about equal to that of the hydrogen, which holds it in combination as water, but when the indigo is introduced, although its attraction for hydrogen must be very weak, as it requires the nicest management to get that compound isolated, still it is sufficient to disturb the equilibrium with which the 304 INDIGO. oxygen was held by the iron and hydrogen, giving the former the mastery. Whether the presence of an alkaUne substance has any effect of inducing, if We be allowed the term, the for- mation of indigogen, we cannot pretend to determine; but it is never formed in the vat -without the presence of some alkaline substance to dissolve it the moment it is formed. This circumstance also explains that the alkali having also an affinity for indigogen, may assist the reaction in the vat. We would recommend the reader to re-pei'use the re- marks upon the salts of iron, in connection with these on the blue vat, in order that he may be better able to appreciate them, and especially to understand what ought to be the pro- perties of good copperas from the part it is required to play in the vat ; also why it is that the quality of the copperas makes so great a difference in the working of a blue vat. There is one serious annoyance often experienced in work- ing the vat, technically called swimming; that is the precipitate not settling down, the goods come in contact with it to the serious injury of the colour. This may be occasioned by several circumstances. Should the copperas have an excess of acid, either from its being crystallized out of an acid solu- tion, or from its having sulphate of alumina in it, (as described at page 155,) it will form a sulphate of lime, which will not precipitate so quickly as that formed by the decomposition of the copperas ; but the prevailing cause of a floating vat is excess of iron and lime. Let the dyer take a solution of copperas or protosulphate of iron, and one of persulphate, and add to each a sufficient quantity of lime to precipitate the iron, he will find that the peroxide of iron will precipitate rapidly and completely, and that the protoxide will precipitate slowly and incompletely. The same phenomenon takes place in the vat when lime and copperas are added ; sulphate of lime and protoxide of iron are formed, and if there be not enough of indigo to convert the protoxide of iron to the state of peroxide — in which state it precipitates easily — the pro- toxide will remain floating for a long time. Hence the floating vat — the only cure for which is the addition of a little indigo, or of a substance that will peroxidize the iron. When vats be- come weak, great care should be taken not to add an excess of copperas. We have seen a little soda added to a floating vat as a cure, and if the evil consisted in the quantity of the THE BLUE VAT. 305 copperas, this mode of cure might be successful, but not otherwise. A floating vat is sometimes caused by using improper lime. When slaked lime lies exposed for a short time to the air, and more especially in a work such as a dye- work, it absorbs carbonic acid, and becomes converted into chalk, and this put into the vat is very deleterious in other respects, besides causing swimming. The lime used for the vat should always be newly slaked. This is a necessary precaution, as the practice is too often otherwise than is here recom- mended. When the paucity of indigo in the last stages of a vat causes floating, a small portion of a copper salt may be of service, as this oxide will give up a part of its oxygen to the iron, \)ecoming a suboxide ; or it will oxidate a portion of the indigo in solution, and this would react in turn upon the iron. The property of this and some other metals for neutralizing the effects of iron in the vat has already been noticed ; but it may be more apparent by thus referring to it here, and it may be still further enforced in connection with that branch of calico printing called resist-work, indicated at page 295, and which may be thus further described : — A certain preparation, the best we believe is the sulphate of copper or zinc, is mixed either with flour paste, with gum, or with pipe-clay and gum, and printed on the calico, of any pattern that may Idc desired ; when this is suflSciently dry, the goods are dyed in the blue vat ; those parts of the piece which are printed with the copper or zinc will not be dyed blue, because the deoxodized indigo becomes oxygenated the moment it touches the copper, which yields its oxygen to the indigo, and occasions it to become insoluble, and consequently incapable of forming a dye. According to Dumas's theory, the hydrogen, in com- bination with the indigo, miites with the oxygen of the copper and forms water — the results are ahke in both. Before concluding this article, we may inform the general reader that, in print-works and dye-houses, where piece-goods are dyed blue, the vats are necessarily large, being generally about three feet wide by five feet long, and eight feet deep, made of iron, but sometimes of stone ; and are sunk into the ground about half their depth. The goods to be dyed are stretched upon a frame, when the whole is lowered into the vat. Sometimes these frames are furnished with rollers, when, instead of fixing the piece on hooks, it -is passed over these 306 INDIGO. rollers while in the vat, by which means long pieces are dyed perfectly regular in colour. The vats for yarn or skein are small, being generally old wine or oil pipes ; these are also sunk about half their depth into the ground. Wooden pins are put through the skein, and rest upon the edge of the vat, the skein is then turned over, the one half dipping in the liquor, the other half over the pins. The time of this operation varies according to the strength of the vat. The operation being continued some time, the skein is taken out, wrung, and exposed to the air, dipped again, and so on, alternately dipping and exposing, till the requisite shade is obtained. To prepare the vat, it is filled to within a few inches of the mouth with water, the dyeing ingredients are then added — the proportions given in most chemical books, are 1 part (by weight) indigo, 2 parts sulphate of iron, and 3 parts lime; but this proportion of lime is too much ; the practical dyer does not consider his vats in good condition when this proportion is used. The following proportions are considered proper for pre- paring one of these small vats — assuming all the ingredients good: — 8 pounds of indigo, 14 pounds of copperas, and from 18 to 20 (not above 20) of lime. If the copperas be bad, a pound or even 2 pounds more of it may be required, along with 2 or 3 additional pounds of lime, to have the same results. These ingredients being put in, the whole is well stirred every two or three hours during the day, and, after settling for twelve hours, the vat is ready for use. The chemical equivalents of lime may be calculated from the table of elements, and also the I'ate of combination. Thus, slaked lime is the hydrated oxide of calcium, — J. rCa =20 "^^'^' {o = 8 37 And again we have — p rFe =28 C°PP^^^^ |S0, =48 Water of crystallization 7 HO = 63 139 WOAD AND PASTEL. 307 Thus, by equivalents, 37 lbs. of slaked lime should neu- tralize 139 lbs. of crystals of copperas ; but as 77 gallons of water, at 60'', can dissolve only one pound of lime, it is easy to see how few pounds are required above the equivalent for copperas to form the lime solution of the vat to dissolve the indigogen. How it is that practice dictates such a quantity of lime to be used, is deserving of inquiry ; we merely hint that it may be that the compound of indigogen and lime is more soluble than lime alone. ■Woad and Pastel.— We have already alluded to these vegetables as yielding a variety of indigo, which has been long used for dyeing woollen goods. It is still extensively used for that purpose, especially on the continent ; and as a description of the process, as it is there followed out, may be interesting to many of our readers, we extract the following from Dumas's Lectures on Dyeing, slightly altered from the trans- lation, in the Pharmaceutical Times : — "indJKo Blue— We give a solid dye of indigo blue to wool by plunging it into an alkaline solution of indigo white, and then exposing it to contact with the air. The solution of indigo white is prepared in a vessel usually from eight to nine feet in depth, and six to seven feet in diameter. This size is very convenient for the requisite manipulations, and pre- sents a large volume of water, which, when once heated, is capable of preserving a high temperature for a long time. This vessel should be made of wood or copper. It always bears the name of vat. These vats are covered with a wooden lid, divided into two or three equal segments. Over this Ud are spread some thick blankets. Without this precaution the bath would come in contact with the atmos- pheric air ; a portion of the indigo would absorb oxygen, and become precipitated. There would also be a great waste of heat. " A most necessary operation, and one which has to be frequently repeated, consists in stirring up the deposit of vegetable and colouring matter which is formed in the vat, and intimately mixing it in the bath. For this purpose we employ a utensil called a rake, which is formed of a strong square piece of wood set on a long handle. Tlie workman takes hold of this with both hands, and, dipping the flat sur- face into the deposit at the bottom of the vessel, he quickly 308 IXDIGO. draws it up until it nearly reaches the surface, when, giving it a gentle shake, he discharges the matter again through the liquor of the bath. This manoeuvre is repeated until the whole of the deposit seems to be removed from the bottom of the vessel. Before the tissue is dipped into the dye-bath, it should be soaked in a copper full of tepid water ; it is then to be hung up and beaten with sticks. In this state it is plunged into the vat ; it thus introduces less air into the bath, while it is more uniformly penetrated by the indigo solution. The cloth is now kept at a depth of from two to three feet below the surface of the liquid, by means of an open bag or piece of network fixed in the interior of an iron ling, which is sus- pended by cords, and fixed to the outside of the vat by means of two small iron hooks ; the bag is thus drawn backwards and forwards without permitting it to come in contact -n-ith the air. When this operation has been continued for a suffi- cient length of time, the cloth is wrung and hung up to dry. " Flock wool is also, for the purpose of dyeing, enclosed in a fine net, which prevents the least particle from escaping, and which is fixed in the bath in the same way as in the forego- ing case. " The many inconveniences attending the use of wooden baths, which necessitate the pouring of the Uquor into a cop- per for the purpose of giving it the necessary degree of heat, have led to the general employment of copper vessels. These are fixed in brickwork, which extends half way up their sur- face, whilst a stove is so constructed at this elevation that the flame shall play aroiind their upper part. By this means the bath is heated and kept at a favourable temperature without the liquor being obliged to be removed. " The potash vats are usually formed of conical-shaped cop- pers, surrounded by a suitable furnace. These juay be con- structed with less depth, inasmuch as there is less precipitation induced in the liquor. By using steam for heating the vats, we might dispense with the emplo}Tnent of copper vessels, and so return to those of wood. " The vats employed for dyeing wool are known under the names of the pastel vat, the woad vat, the potash vat, the tartar lee vat, and the german vat. " The pastel is cultivated in France, Piedmont, England, and Saxony. It is distinguished into several varieties, ac- THE PASTEL VAT. 309 cording to the localities in which it is grown. We have already stated that the pastel contains a blue-colouring matter, identical with indigo, and a fawn-coloured yellow matter, which may easily be separated by treating the pastel-balls by hot water, before the fermentative process is established. The woad is cultivated in Normandy ; it contains less colouring matter, whether blue or yellow, than the pastel; its dura- bihty is also inferior to that of the last-named substance. M. Chevi-eul has given an analysis of the pastel, which will tend to throw some light upon its use. " When the leaves are subjected to the action of the press, we obtain, on the one hand, a residue of a ligneous nature, and, on the other, a juice which holds in suspension sundry matters which give it a cloudy appearance. Thrown on a filter, it leaves a greenish matter or fecula, which is formed of chlorophylle, wax, indigo blue, and an azotized substance. The clear liquid, after passing through the filter, contains an azotized substance, coagulable by heat ; an azotized substance, noncoagulable by heat; a red matter, resulting from the union of the blue-colouring principle with an acid ; a yellow principle ; gummy matter ; some liquid sugar ; a fixed orga- nic acid ; free acetic acid and acetate of ammonia ; the oderous principle of the crucifertc ; a volatile principle, having the odour of osmazome ; citrate of lime ; sulphates of lime and potash ; phosphates of lime ; magnesia, ii-on, and man- ganese ; nitre, and chloride of potassium. " M. Chevreul has not discovered in these products any body possessed of the power of seizing upon oxygen in an energetic manner, and which would explain the action of the pastel in the indigo vat. Still we cannot doubt that the prin- ciples furnished by this matter intervene, to -a certain extent, as combustibles, and that we must refer at least a part of their eflect to this mode of action. The indigo shoiild itself be selected with care. The Guatimala variety is preferred for the urinary or Indian vat, and the Bengal indigo for the pas- tel vat. " Pastel Vai.— The first care of the dyer in preparing the vat should be to furnish the bath with matters capable of combin- ing with the oxygen, whether directly or indirectly, and of giving hydrogen to the indigo. We must, however, be care- ful to employ those substances only which are incapable of 310 INDIGO. imparting to tlie bath a colour whicli might prove injurious to the indigo. These advantages are found in the pastel, the woad, and madder. This latter substance furnishes a violet tint when brought into contact with an alkali, and by the addition of indigo it yields a still deeper shade. " In preparing the Indian vat we ordinarily employ one pound of fine madder to two pounds of indigo. The madder is here especially useful, by reason of the avidity of some of its principles for oxygen. " The pastel vat, when prepared on a large scale, ordinarily contains from 18 to 22 lbs. of indigo ; 11 lbs. of madder would suffice for this proportion, but we must also bear in mind the large quantity of water which we have to charge with oxidiz- able matters. I have invariably seen the best results from employing 22 lbs. to a vat of this size. Bran is apt to excite the lactic fermentation in the bath, and should, therefore, not be employed in too large a quantity : 7 to 9 lbs. will be found amply sufficient. " The weld is rich in oxidizable principles ; it turns sour, and passes into the putrid fermentation with facility. Some dyers use it very freely ; but ordinarily we employ in this bath an equal quantity of it to that of the bran. Sometimes weld is not added at all. " In most dye-houses the pastel is pounded before intro- ducing it into the vat. Some practical men, however, main- tain that this operation is injurious, and that it interferes with its durability. This is an opinion which deserves atten- tion. The effect of the pastel, when reduced to a coarse powder, is more uniform ; but this state of division must ren- der its alterations more rapid. When the bath has under- gone the necessary ebullition, the pastel should be introduced into the vat, the liquor decanted, and, at the same time, 7 or 8 lbs. of lime added, so as to form an alkaline ley, which shall hold the indigo in solution. Having well stirred the vat, it should be set aside for four hours, so that the little pellets shall have time to become thoroughly soaked, both inside and out, and thus be prepared for fermentation. Some thick coverings are to be spread over the vat, so as to preserve it from contact with the atmosphere. After this lapse of time, it is to be again stirred. The bath at this moment presents no decided character; it has the peculiar odour of the vege- THE PASTEL VAT. 311 tables vvhicli it holds in digestion ; its colour is of a yeUowish- brown. " Ordinarily, at the end of twenty-four hours, sometimes even after fifteen or sixteen, the fermentive process is well marked. The odour becomes amnioniacal, at the same time that it retains the peculiar smell of the pastel. The bath, hitherto of a brown colour, now assumes a decided yellow- ish-red tint. A blue froth, which results from the newly liberated indigo of the pastel, floats on the liquor as a thick scum, being composed of small blue bubbles, which are closely agglomerated together. A brilliant pellicle covers the bath, and beneath we may perceive some blue or almost black veins, owing to the indigo of the pastel which rises tOAvards the sur- face. If the liquor be now agitated with a switch, the small quantity of indigo which is evolved floats to the top of the bath. On exposing a few drops of this mixture to the air, the golden yellow colour quickly disappears, and is replaced by the blue tint of the indigo. This phenomenon is due to the absorption of the oxygen of the air by the indigogen from the pastel ; in this state we might even dye wool with it without any further addition of indigo ; but the colours which it furnishes are devoid of brilliancy and vivacity of tone, at the same time that the bath becomes quickly ex- hausted. " The signs above described announce, in a most indubitable manner, that fermentation is established, and that the vat has now the power of furnishing to the indigo the hydrogen which is required to render it soluble, — that contained in the pastel having been already taken up ; this, then, is the proper moment for adding the indigo, which should be previously ground in a mill. " We stated above that the liquor of the vat should be pre- viously charged with a certain quantity of lime ; we also find in it ammonia generated by the pastel ; but a part of these alkalis become saturated by the carbonic acid gas along with the proper acids of the madder and of the weld, as well as by the lactic acid produced by the bran during fermentation. The ordinary guide of the dyer is the odour which, according to circumstances, becomes more or less amnioniacal. The vat is said to be either soft or harsh ; if soft, a little more lime should be added to it. The fresh vat is always soft ; it 312 IXDIGO. exhales a feeble ammoniacal odour, accompanied with the pecuhar smell of the pastel ; we must, therefore, add Ume to it along with the indigo; we usually employ from five to six pounds, and, after having stirred the vat, it is to be covered over. The indigo, being incapable of solution except by its combmation \\-ith hydrogen, gives no sign of being dis- solved until it has remained a certain time in the bath. We may remark that the hard indigoes, as those of Java, require at least eight or nine hours, whilst those of Bengal do not need more than six hours, for their solution. We should examine the vat again three hours after adding the indigo. We ordi- narily remark that the odour is by this time weakened ; we must now add a further quantity of lime, sometimes less, but generally about equal in amount to the first portion ; it is then to be covered over again, and set aside for three hours. " After this lapse of time the bat"h will be found covered with an abundant froth and a very marked copper-coloured pellicle ; the veins which float upon its surface are larger and more marked than they were previously ; the liquor becomes of a deep yellowish-red colour. On dipping the rake into the bath, and allowing the liquid to run off at the edge, its colour, if viewed against the light, is of a strongly-marked emerald- green, which gradually disappears, in proportion as the indigo absorbs oxygen, and leaves in its place a mere drop rendered opaque by the blue colour of the indigo. The odour of the vat at this instant is strongly ammoniacal ; we also find in it the pecuhar scent of the pastel. When we discover a marked character of this kind in the newly-formed vat, we may without fear plunge in the stuff intended to be dyed; but the tints given during the first working of the vat are never so brilliant as those subsequently formed ; this is omng to the yellow-col oiuring matters of the pastel, which, aided by the heat, become fixed on the wool at the same time as the indigo, and thus give to it a greenish tint. This accident is common both -with the pastel and the woad vats ; it is, however, less marked in the latter. " When the stuff or cloth has been immersed for an hour in the vat it should be ■withdrawn ; it would, in fact, be useless to leave it there for a longer time, inasmuch as it could absorb no more of the colouring pi'inciple. It is, therefore, to be taken from the bath and hung up to dry, when the indigo, by WOAD VAT. 313 attracting oxygen, will Ijocome insoluble and acquii'c a blue colour. Then we may replunge the stuff in the vat, and the shade will immediately assume a deeper tint, owing to renewed absorption of indigo by the wool. By repeating these opera- tions we succeed in giving very deep shades. We must not, however, imagine that the cloth seizes only on that portion of indigo contained in the liquor required to soak it. Far from such being the case, experience shows that, during its stay in the bath, it appropriates to itself, within certain limits, a gra- dually increasing quantity of indigo. We have here, then, an action of athnity, or, perhaps, a consequence of porosity on the part of the wool itself. " «"oad Vai. — These vats are extensively employed at Louviers, and in the manufactories of the north of France. The bath is prepared in the same manner as in the foregoing case : the finely-cut root is introduced into the copper along with 2 lbs. of pounded indigo, 9 lbs. of madder, and 15^ lbs. of slaked lime. The liquor is, after the necessary ebullition, poured upon the woad. This substance contains 'but a very small quantity of colouring principle ; we must, therefore, add some indigo when preparing the vat, so as to indicate the pre- cise instant when the mixture arrives at the point of fermen- tation so necessary for imparting hydrogen to the colouring principle, and for rendering it soluble. We must also use a larger quantity of lime, since the woad contains no ammonia resulting from previous decomposition, such as we find to be the case with the pastel of the south. When the vat is in a suitable state of fermentation, a rusty colour becomes manifest, in addition to the signs already described in speak- ing of the pastel vat; besides the ammoniacal odour, the bath always retains the peculiar smell of the woad. The pounded indigo is now added, and we proceed, in the manner already detailed, to reduce it to a state of solution fit for dyeing. " The vats prepared by means of pastel have greater dura- bility than those made with the woad ; but it is thought that the colours given by the latter are more brilliant than those obtained from the former dye. '• iTiodified PaHtel Tai. — This vat is about 7 feet in depth, and 6^ feet in diameter. It is made of copper, and heated by steam. The lid is composed of three segments, each of which 314 DfDIGO. is formed of two planks, about an inch thick, and strongly secured together by bolts. " The beating is performed in the usual way, with sticks, before the first dipping, after having moistened the cloth in tepid water. This operation is not subsequently re- peated. "This vat is prepared >vith 13 lbs. of indigo, 17^ lbs. of madder, 4^ lbs. of bran. 9 lbs. of lime, and 4h lbs. of potash. HaA-ing filled the vat, we heat it to about 200" Fab., and, as soon as the water is tepid, introduce 4.41 lbs. of pastel. The Uquor becomes of a yellowish-brown colour : small bubbles appear upon its surface, ordinarily at the end of four hours if the vat be heated by steam, but not untU after eight or twelve hours where heat is applied by the common fire ; in the latter case the mixture shoidd be stirred every three hours. When the liquor displays the signs of fermentation, we add the above- mentioned ingredients, and cover the vat over ; it is then to be set aside, stirring it every three hours, or oftener if the fer- mentative action be ver}' rapid. Each time that it is stirred we are to add fi-om 2 to 4 lbs. of lime ; if fermentation pro- ceed quickly we even use more, but in the contrarj' case less. After about eighteen hours we plunge into the vat three pieces of common cloth, measuring twenty to twenty-five ells in length each : when they have received sis or seven turns they are to be taken out again. The object of this is to remove the excos; of lime from the bath. The vat is then set aside for three hours, when it is to be stirred,, and 13 lbs. of indigo, ■with 2 lbs. of madder, added to it. "NVe now again apply heat to the mixture. " If the vat contains a superabundance of lime, it will be imnecessary to add more : othenvise we throw in a further quantity. During the night it should be covered with a cloth, and a workman left to watch it. It is usually stirred once before the morning; but if it be deficient in lime, it will require this manipulation to be more frequently repeated, and also fresh lime added to it. On the following day the stirring should be continued ever)'^ three hours, and so on for the next thirty hours, taking care to heat the vat from time to time. On the morning of the fourth day the dyeing may be com- menced. ''The temperature should be maintained at a pretty vmiform INDIAN VAT. 315 point ; if it be too hot the blue takes a red reflection, by rea- son of the madder contained in the hquid. A vat thus pre- pared will last three months ; we may even work it for double that period, but alter the third month it appears to lose some of its indigo. " We maintain the power of the vat by introducing every niixht 2t lbs. of madder. Some indi2;o is also added twice or three times a-week. These additions are made in the evening. After the former, the vat is left at rest for forty-two hours ; with the latter, only for twenty-four, at the same time observ- ing the precautious already indicated. At the end of three months, or sooner, when we wish to stop the working of the vat, we exhaust the indigo ; for this purpose we continue to charge it every night, for the space of a month, with madder, and dip into it white cloths, or more particularly woollen tissues, which become more or less loaded with the indigo. We must continue this plan until these matters take up no further colour. The dippings are to be performed twice a-day at first, but once only towards the termination. Many dyers make use of this bath for preparing a new vat ; but it is better to throw this away and make it up afresh with common water. " Indian Vai. — These vats are of more simple and of more ready construction than the pastel or woad vats. We are to boil in water a quantity of madder and of bran, proportioned to the weight of indigo which we wish to employ. After two hours' ebullition, we turn into this bath some tartar-lees, which are also to be boiled for an hour and a-half or two hours, so as to charge the bath with whatever soluble matter they may contain ; after this ebullition, the bath should be allowed to cool, and the indigo, which has been previously ground, is then to be introduced. Supposing that we wish to employ 21 lbs. of indigo, the following would be the propor- tions used in preparing this vat : — 41 lbs. of tartar-lees, 13 lbs. of madder, and o lbs. of bran. These vats are usually mounted in coppers of a conical shape ; a small fire should be kept up around them, so as to maintain a moderate and uniform heat. The indigo will usually be found dissolved at the end of twenty- four hovirs, often even after twelve or fifteen hours. The liquor has a reddish colour in the new vats, and a green tint iu those which are in a working state. The frothy surface, 316 INDIGO. as well as the brilliant-coloured pellicle, become manifested iu this as in all other preparations of a like kind. " This species of vat has to be renewed much more fre- quently than the woad and pastel vats, from the indigo being more difficult to dissolve, after a certain lapse of time. A mo- derate heat should be maintained in all these vats. " Potash Vai — This species of vat is extensively employed at Elbeuf for the dyeing of wool in the flock. It presents in all respects a perfect analogy with the Indian vat ; in fact, the action of the tartar-lee, in the latter preparation, depends entirely on the carbonate of potash which it contains. The ingredients used in the preparation of the potash vat are — bran, madder, and the subcarbonate of potash of commerce. " We obtain the deep shades in this species of vat with greater celerity than in all others, a fact which undoubtedly depends on the greater power which potash has of dissolving indigo than is possessed by lime. Experience proves that the potash vat has the advantage iu point of celerity of nearly a third ; but this is balanced by the inconvenience resulting fi'om the darker shade, which we must attribute to the large quantity of colouring matter of the madder dissolved by the alkaline lee, and which becomes fixed on the stuff with the indigo. " To render this vat iu its most favoiu-able state, the indigo should be made to undergo a commencement of hydrogena- tion, before turning it into the mixture ; for this purpose we prepare, in a small copper, a bath analogous to that in the vat, to which the pounded indigo is added. This bath is maintained, for twenty-four hours, at a moderate heat, taking care to stir it from time to time. The indigo assumes a yel- lowish colour, becomes dissolved, and in this state is turned into the vat ; we thus avoid many delays and losses in its pre- paration ; and, indeed, it would be desirable if a similar plan were adopted with all these compounds. " Cerman Vat. — This vut is of nearly similar dimensions to that used for the woad, being three times the size of the potash vat. Its diameter is about G^ feet, and its depth 8^ feet. Having filled the copper with water, we are to heat it to 200° Fah. ; we then add 20 pailsful bran, 22 lbs. of carbonate of soda, 11 lbs. of indigo, and 5^ lbs. of lime, thoroughly slaked, in powder. The mixture is to be well stirred, and then set aside GERMAN TAT. 317 fur two hours; the workman should continually Avatch the progress of the fermentation, moderating it more or less by means of lime or carbonate of soda, so as to render the vat in a working state at the end of twelve, fifteen, or, at the most, eighteen hours. The odour is the only criterion by which the workman is enabled to judge of the good state of the vat; he must, therefore, possess considerable tact and experience. " In the process of dipping we introduce 84 lbs., 106 lbs., or even 130 lbs. of wool, in a net bag, similar to that used in the woad vat, taking care that the bag is not allowed to rest against the sides of the copper. When the wool has sufh- ciently imbibed the colour, we remove the bag containing it, and allow it to drain for a short time over the vessel. We operate in this way on two or three quantities in succession ; we then remove the vat, and set it aside for two hours ; we must be careful, from time to time, to replace the indigo absorbed by the wool, as also to add fresh quantities of bran, lime, and crystallized carbonate of soda, so as constantly to maintain the fermentation at a suitable point. " The German vat differs, then, from the potash vat by the fact that the potash is replaced by crystallized carbonate of soda and caustic lime, which latter substance also gives to the carbonate of soda a caustic character. It presents a remark- able saving as compared to the potash vat; hence the fre- quency of its employment ; but it requires great care, and is more dillicult to manage. It also offers considerable economy of labour: one man is amply suihcient for each vat. "The army cloth is usually dyed by means of the pastel vat, which gives the most advantageous resists. We here make use of vats about 8^ feet in depth, and 5 feet in diameter, into which we introduce from 361 lbs. to 405 lbs. of pastel or of woad, after previous maceration. The vat is to be filled with boiling water, and we then add to the bath 22 lbs. of madder, 17^ lbs. of weld, and 13 lbs. of bran. The mixture is to be maintained in a state of ebullition for about half an hour ; we next add a few pailsful of cold water, taking care, how- ever, not to lower the temperature beyond 130" Fah. ; during the whole of this time a workman, provided with a rake, keeps incessantly stirring the materials of the bath. The vat is then accurately closed by means of a wooden lid, and surrounded by blankets, so as to keep up the heat. It is now put aside 318 INDIGO. for six hours; after this time it is again stirred, by means of a rake, for the space of half an hour ; and this operation should be repeated every three hours until the surface of the bath becomes marked with blue veins ; we then add from six to eight pounds of slaked lime. " The colour of the vat now borders on a blackish-blue. We immediately add the indigo in a quantity proportioned to the shade which we wish to obtain. Tiie pastel in the fore- going mixture may last for several months ; but we must renew the indigo in proportion as it becomes exhausted, at the same time adding both bran and madder. In general we employ — "11 to 13 lbs. of good indigo for 100 lbs. of fine wool. "9 to 11 lbs. of good indigo for 100 lbs, of common wool. "9 to 11 lbs. of good indigo for 131 yards of cloth dyed in the piece. '* JTianagemcnt of the Vai8. — A good condition of the vat is recognized by the following characters : — The tint of the bath is of a fine golden-yellow, and its surface is covered with a blueish froth and a copper-coloured pellicle. On dipping the rake into the bath, there escape bubbles of air, which should burst very slowly; when they vanish quickly, it becomes an indication that we must add more lime. The paste which is found at the bottom of the vat, green at the moment of its being drawn up, should become brown in the air ; if, however, it remain green, this is a further sign that more lime is required. Lastly, the vat should exhale the odour of indigo. We usually complete the assurance of the vat being in a good state by plunging into it, after two hours' respite, a skein of wool, which, on being withdrawn after the lapse of half an hour, should present a green colour, but change directly to blue. We then once more mix the materials of the vat, and, two hours after, it may be considered ready for dyeing. "These vats, like those already described, are provided with a large wooden ring, the interior of which is armed with a kind of network, for the purpose of preventing the objects which are intended to be dyed coming in contact with the materials at the bottom of the vat ; we, moreover, take the precaution of enclosing the wool or cloth in bags. These tissues, when plunged into the bath, should remain there for MANAGEMENT OF THE VATS. 310 a longer or shorter time, according to the shade Avhich we wish to obtain ; one dipping, however, will never suthce for this object ; usually we leave in the stuff for half an hour only; it is then to be taken from the bath, wrung, and exposed to the air. This operation is repeated until we have succeeded in procuring the desired shade ; we ordinarily suffer three liours to elapse between each dipping. The heat of the vat should never be allowed to fall below 130° Fah. After each operation the bath must be well stu-red, and fresh lime added; generally speaking, a pound a-day will suffice ; we re-establish the mdigo about every second day. When once this vat is well mounted, and we arc careful to examine its working, we may dye from two to four batches a-day with it.- " When the stuffs have acquired the desired shade, they arc first to be washed in common water, and then in a very weak solution of hydrochloric acid (about one part in a thousand ;) after this they are again rinsed in pure water. " The Indian vat is nuxch more easily managed than tin- foregoing ; it presents less danger of failure, from the fact that it is quickly exhausted, and also from the fermentative pro- cess, which is so difficult to govern in the pastel vat, here nlumb spirits, sufficient to raise the specific gravity to about 1-4° of Twaddell. After standing twenty-four hours, it is fit for use — which consists simply in immersing the goods for a short time, then taking them out and washing them. As this com- pound of tin and logwood is held in solution by the free acid of the spirits, whenever the cotton impregnated with it is put into water, the dye is rendered insoluble ; the repeated wash- ing is necessary to carry off all free acid. Occasionally in preparing the plumb tub, it happens from some cause, as want of care in making the spirits or the decoction, that the log- wood gets all precipitated. This precipitate may all, or the greater part of it, be dissolved by adding hydrochloric acid ; but then the tint of colour produced upon the goods will not be so blue : it will be more red, with a tendency to brown. Hydro- chloric or nitric acid added to a cold solution of logwood, will make a plumb tub without tin ; but there being no base, and the solution being soluble in water, it does not form a good dye, being nearly all removed by washing. But if the goods be previously prepared with a base, colours of various tints may be obtained by this means — which may be resorted to when a plumb tub is not at hand. brazil-woods. 331 Brazil-Woods. The Bois de Pcrnamhouc of the French, and the Brazilienholz of the German dyers. There are several varieties of this wood, which are distinguished from each other by the name of the locaUty where they are obtained, such as Pernambuco, Japan, &c. In the dye-house they are often all named peach-wood, from an inferior sort often used, and obtained from Campeachy. The Brazil-wood tree, called by botanists Ccesalpinia crista, is an American production, and, according to some authori- ties, gave the name to the country in which it grows,* Brazil. The Portuguese government discovered the value of the wood, and made it an object of royal monopoly ; hence it came by the nearly forgotten name of Queen-wood. It grows mostly in dry places, and amongst rocks ; its trunk is large, crooked, and full of knots. The following paragraph upon these woods is taken from Bell's Geography : — " The ibiripitanga, or Brazil-wood, called in Pernambuco the pao da rainha (Queen's-wood,) on account of its being a government monopoly, is now rarely to be seen within many leagues of the coast, owing to the improvident manner in which it has been cut down by the government agents, without any regard being paid to the size of the tree or its. cultivation. It is not a lofty tree. At a short dis- tance from the ground, innumerable branches spring forth, and extend in every direction in a straggling, irregular, and unpleasing manner. The leaves are small and not luxuriant ; the wood is very hard and heavy, takes a high polish, and sinks in water ; the only valuable portion of it is the heart, as the outward coat of wood has not any peculiarity. The name of this wood is derived from brasas, a glowing fire or coal — • its botanical name is Ccesalpinia brasileto. The leaves are pinnated ; the flowers white and papilionaceous, growing in a pyramidal spike ; one species has flowers variegated with red. The branches are slender, and full of small prickles. There are nine species." Tlie species brasileto is inferior to the crista; it grows in great abundance in the West Indies. The demand for this wood a few years ago was so great, owing to its being a little * Southev's History of Brazil, vol. i. 332 BRAZIL-WOODS. cheaper than the other, that nearly the whole of the trees in the British possessions were cut down, and sent home — which Mr. Bell very justly terms improvidence. It is not now so much used, and is consequently scarcer in the market. The wood known in commerce as Pernarabuco is most esteemed, and has the greatest quantity of colouring matter. It is hard, has a yellow colour when newly cut, but turns red by exposure to the air. That kind termed Lima-wood is the same in quality. Sapan-wood grows in Japan, and in quality is next to the two named above. It is not plentiful, but is much valued in the dye-house for reds of a certain tint : it gives a very clear and superior colour. The quantity of ash that these two qualities of wood contain is worthy of remark. Lima- wood as imported gives the average of 21 per cent., while Sapan-wood gives only 1"5 per cent.: in both the prevailing earth is hrae. The quantity of moisture in the wood averages about 10 per cent. That in the ground wood in the market about 20 per cent. Peach-wood, or Nicaragua, and sometimes termed Santa Martha-wood, is inferior to the other two named, but is much used in the dye-house, and for many shades of red is preferred, although the colouring matter is not so great. It gives a bright dye. The means of testing the quality of these woods by the dyer is similar to that described for logwood, with the same recommendations aud precautions. The world is much indebted to the French chemists for their valuable researches into the colouring matters of the dye- woods. M. Chevreul long since obtained the colovuiug mat- ter from Brazil-wood by the following process : — " Digest the raspings of the wood in water till all the colouring matter is dissolved, and evaporate the infusion to dryness, to get rid of a little acetic acid which it contains. Dissolve the residue in water, and agitate the solution with htharge, to get rid of a little fixed acid which it contains. Evaporate again to dry- ness, digest the residue in alcohol, filter and evaporate to drive ofi" the alcohol. Dilute the residual matter with water, and add to the hquid a solution of glue, till all the tannin which it contains is thrown down ; filter again and evaporate to dry- ness, and digest the re.sidue in alcohol, which will leave undissolved any excess of glue which may have been added. This last alcoholic solution being evaporated to dryness, leaves BREZILIN. 333 brezilin, the colouring matter of the wood, in a state of con- siderable purity." Brezilin is very soluble both in water and alcohol, but from the hardness of the wood the colouring matter is not com- pletely extracted except by boiling ; even the method recom- mended for logwood does not dissolve all the brezilin. The decoction when boiled has a deep-red colour, but passes into a rich yellow-red by standing. Acids give this solution a yellowish colour, but render it unfit for dyeing operations. Alktilis communicate a violet colour which is very fugitive: — Protosulphate of iron Dark purple, not changed by standing. Persulphate of iron Blackish-brown, permanent. Chloride of tin Changes to a deep crimson. Chloride of tin > With warmed liquor, a deep- red precipitate. Acetate of copper Dark purple. Since these researches by Chevreul, M. Preisser has inves- tigated these substances with great minuteness, and gives it as his opinion that the colouring matter of these, as well as of the other woods, are oxides of a colourless base. Thus brezilin is the oxide of a base which is without colour, and which he terms brezilein. Their compositions are — Brezilein — Colourless base Brezilin — Coloured substance. c. H. 0. = 36 14 12 = 36 14 14 It will thus appear that the one is converted into the other by absorbing two proportions of oxygen, and that the reac- tions are allied to those of indigo and logwood already de- scribed. The action of chromic acid, and of the chromates upon brezilin, is remarkable : they decompose each other, and pro- duce a beautiful reddish-brown. The action of bichromate of potash with the decoction of Brazil-wood has been long taken advantage of in calico printing, and, by proper modifi- cations, may also be applied in the dye-house. The remarks upon the pure colouring matter are applicable to the de- coction of the wood ; but the wood contains other mat- 334 SANTAL OB SANDAL- WOOD. ters, (small portions of astringent substance,) which are also soluble in the water, and which, accordingly, modify to a great extent the results produced by the combined action of the decoction and the pure colouring principle — a circum- stance which should be constantly borne in mind by the dyer. It is known that decoctions of Brazil-wood improve by stand- ing, often to the extent of giving a-half more effect as a dye ; which is supposed to be owing to the oxidation and deposi- tion of the tannin, and other foreign matters, injurious to the colour. The nitrates of the metals almost all destroy the red colour of Brazil-wood, turning it into a dirty yellow. The salts of potash, soda, and ammonia, change the decoction into a rose colour, which soon passes away by standing. Alum throws down a bulky red precipitate. This substance, and the chloride of tin, are considered the proper mordants for Brazil- wood ; but all the colours obtained by this wood are exceed- ingly fugitive, losing their brilliancy on a short exposure to air. The sun has a very powerful influence upon colours dyed by this wood. By a short exposure, the red colour assumes a blackish tint, passes into a brown, and fades away into a light-dun coloui'. These changes are supposed to be from the colouring matter being decomposed into water and some other volatile substance, leaving a part of the carbon free, which produces the black ; heat is also very destructive to this colour; nevertheless, the consumption of this species of wood is very great, especially for dyeing what are termed fancy reds. Santal or Sandal- Wood, Commonly called saunders-wood, is a native of the East Indies. It differs from Brazil-wood in many of its properties ; it is very hard, and gives but a weak decoction in water. The colouring matter of this wood is different from that of Brazil-wood : its composition is — Carbon. Hydrogen. Oxygen. 16 8 32 and is termed santaline. It reacts with the salts of alumina, and gives red precipitates, which have more of a violet tint BAR WOOD. 335 than those of brezilia; but it does not react in the same manner with the chromates. SantaUne is much more soluble ia solutions of the astringent substances than in water ; it is, therefore, boiled along with sumach, and is frequently used for woollens in dyeing browns and other mixed colours containing red. According to the investigations of the French chemists, this wood is a variety of barwood, at least the colouring matter is of the same composition. Bakwood. This wood is brought principally from Sierra Leone. Its colouring matter has been examined by MM. Girardin and Preisser, who considered it the same as suntaline. MacCuUoch in his Commercial Dictionary makes a distinction between barwood and camwood ; but they are found to be the same in chemical composition, only coming from two different places. The following is MM. Girardin and Preisser's description of this wood: — " This wood, in the state of a coarse powder, is of a bright- red colour, w^ithout any odour or smell. It imparts scarcely any colour to the saliva. " Cold water, in contact with this powder, only acquires a fawn tint after five days' maceration ; 100 parts of water only dissolve 2 '21 of substances consisting of 0'85 colouring matter and of 1'36 saline compounds. Boiling water becomes more strongly coloured of a reddish-yellow, but on cooling it deposits a part of the colouring principle in the form of a red powder. 100 parts of water at 212" dissolve 8"86 of sub- stances consisting of 7'24 colouring principle and 1'62 salts, especially sulphates and chlorides. On macerating the powder in strong alcohol, the liquid almost immediately acquires a very dark vinous-red colour. To remove the whole of the colour from fifteen grains of this powder, it wiis necessary to treat it several times with boiling alcohol. The alcoholic liquid contained 0'23 of colouring principle and 0'004 salt; bar- wood contains, therefore, 23 per cent, of red colouring matter, whilst saunders-wood, according to Pelletier, only con- tains 16"75. 336 BAR WOOD. " The alcoholic solution behaves in the following manner towards re-agents : — Distilled water, added in } great quantity ^ Produces a considerable yel- low opalescence. The pre- cipitate is re-dissolved by the fixed alkalis, and the liquor acquires a dark vinous colour. Fixed alkalis Turn it dark criinson or dark violet. Lime-water Ditto. Sulphuric acid Darkens the colour to a co- chineal red. Sulphuretted hydrogen Acts Hke water. Salt of tin Blood-red precipitate. Chloride of tin Brick-red precipitate. Acetate of lead Dark violet gelatinous pre- cipitate. Salts of the protoxide of ^ Very abundant violet pre- iron J cipitates. Copper salts Violet-bro wn gelatinous pre- cipitates. Chloride of mercury An abundant precipitate of a brick-red colour. Nitrate of bismuth Gives a light and brilliant crimson red. Sulphate of zinc Bright red flocculent pre- cipitate. Tartar-emetic Abundant precipitate of a dark cherry colour. Neutral salts of potash Act like pure water. Water of barytes Dark violet-brown precipitate. Gelatine Brownish -yellow ochreous pre- cipitate. Chlorine Brings back the liquor to a light yellow, with a slight yellowish-broAvn precipitate, resembling hydrated per- oxide of iron. BARWOOD, 337 " Pyroxylic spirit acts on barvvood like alcohol, and the strongly-coloured solution behaves similarly towards re-agents. Hydratcd ether almost immediately acquires an orange-red tint, rather paler than that with alcohol. It dissolves 19-47 per cent, colouring principle. Ammonia, potash, and soda, in contact with powdered barwood, assume an extremely dark violet-red colour. These solutions, neutralized with hydro- chloric acid, deposit the colouring matter in the form of a dark reddish-brown powder. Acetic acid becomes of a dark- red colour, as with saunders-wood." The difficulty of its slight solubiUty in water is overcome by a very ingenious arrangement. The colouring matter, while hot, combines easily with the proto-compounds of tin, form- ing an insoluble rich red colour ; the goods to be dyed are impregnated with protocbloride of tin combined with sumach ; the proper proportion of barwood for the colour wanted is put into a boiler with water and brought to boil ; the goods thus impregnated are put into this boiUng water containing the rasped wood, and the small portion of colouring matter dissolved in the water is immediately taken up by the goods. The water thus exhausted dissolves a new portion of colour- ing matter, which is again taken up by the goods, and so on, till the tin upon the cloth has become, if we may so term it, saturated ; the colour is then at its brightest and richest phase. A good deal of attention and skill is necessary to know the exact point to take the goods out of the bath, otherwise the dyer may either have the colour poor, or by being in too long, give it a brown colour. It is not, therefore, every dyer who can dye good barwood red. In dyeing with this wood it must be in contact with the goods : the particles of the wood must mix with the fibre. To have the wood in a bag, even, does not answer; and therefore great care is necessary in putting the mordanted goods into the dyeing bath, that there be no loose mordant upon them; for if there is, the wood (being in the bath) will take up this mordant and become dyed, and so retain a correspond- ing portion of the colouring matter, and to tliat extent cause loss. Inattention to this precaution is, moreover, frequentl}' the cause of great irregularity in the shades ; and even with the greatest care, the tvood-grounds come out of the bath richly dyed. Barwood is not used along with other matters Q 338 CAMWOOD. for compound colours, in the same way as the other red woods are for dyeing cotton ; but it is occasionally so used in dyeing woollens. The dyer has no means of testing the value of this dyewood, owing to its insolubility in water. In a piece of wood as imported, we found moisture 11 per cent, and only O'O per cent, of ash. In ground samples the mois- ture ranges about 20 per cent, and the ash 1-2. The colour- ing matter is very soluble in dilute ammonia. By passing ammonia water through a weighed quantity upon a filter, until all soluble matters are dissolved out, then drying the residue, the average of good barwoods gives — Wood remains 73"4 Water at 212° 18-2 Coloiuring matter 8*4 100-0 By neutralizing the ammonia the colour is precipitated as a la^e. It is recommended in some works upon dyeing as a general rule, that as all colours that are dyed in boilers begin to take on the dye when the solution is lukewarm, the goods should be put in at that heat, and kept in till boiling. This may be best in the case of woollen, and even with some colours, such as barwood and madder, upon cotton ; but it is not good as a rule for cotton. Generally, indeed, the quicker cotton is dyed the better, and when there is a mixture of colouring matters used, long working causes that colour, which has the greatest attraction for the mordant, to prevail at the expense of the others, even although the attraction when the goods were newly put into the mixture may have been simul- taneously equal and mutual. Camwood Is another species of red wood sometimes used in the dye- house, imported from Sierra Leone. The colour obtained from it is more permanent, and in many instances much more beautiful than those termed Brazil-woods. The precipitates from a decoction of the wood are more yellow than those FUSTIC OK YELLOW-WOOD. 339 afforded by the Brazil-woods — which explains why the colours dyed by it have a certain degree of richness not obtained with the other woods. It is not so easily affected by alkaline substances, and appears to contain more tannin than the Brazil-woods. With it — Protosulphate of iron Gives a brownish -black preci- pitate. Persulphate A reddish-brown. Protosalts of tin Give the solution a very bright carmine - red colour, but little precipitate. Lead salts A rich orange precipitate after standing some time. Acetate of copper A Ught reddish-brown. Nitrate of silver A reddish -yellow precipitate. Perchloride of mercury Light orange by standing. Alum Gives the solution a beautiful red colovir. Tliis wood may also be \ised for browns and other composi- tion colours where Brazil-wood is commonly used ; it is more soluble in water, has other advantageous properties, and may be used as a substitute for many other purposes in which the best Brazil-woods are employed. Fustic or Yellow-Wood. This dyestuff has been long known. It is imcertain when it was introduced as a dye-drug, but mention is made of it in a book published in 1692. The botanical name of the tree which produces this drug is Moms tinctoria. It grows spon- taneously in Brazil, and in several of the West Indian islands, where it attains to a great height. The wood is of a sulphur colour, with orange veins, and contains two colouring matters ; the one resinous, and not soluble in Avater ; the other very soluble in this menstruum, producing a deep-yellow colour, having a light orange cast. This substance has been long used for dyeing yellow, is still extensively employed for pro- ducing that colour upon woollen and sUk, i.nd is the principal 340 FUSTIC OB TELLOW-WOOD. ingredient in dyeing greens upon these substances ; but it is seldom used for cotton. The colouring matter of this wood has been studied by M. Chevreul, who has given it the name of morin. If we take one poimd of ground fustic and boU it for a short time in a gallon of distilled water, and then pass the solution rapidly through a filter, to separate the woody particles ; as the solution cools it becomes turbid, and a quantity of the coloming matter is precipitated. If allowed to stand for several days, a goodly quantity of morin may be obtained in a crystalline form. Every practical dyer who has used fustic, knows that if his decoction of this wood stand over, it loses its colouring properties, and that therefore it shoidd be used immediately after boUing. The yellow decoction of this wood gives with the following re-agents : — Alkalis An orange colour with a green tint. Protochloride of tin... A reddish-yellow. Percldoride of tin A rich yellow. Alum A canary yellow. Acetate of lead An orange-yeUow, but dirty. Acetate of copper A brown tint. Protosalts of iron A greenish - olive tint, which darkens by standing. Persalts of iron The same. Sulphuric acid A red precipitate by standing. Nitric acid A red precipitate. The morin precipitated from the solution, is soluble in water with difficulty, but dissolves freely in a weak alkah, from which it may be precipitated. The colouring matter is often found crystallized in veins of the wood. The base of this colouring substance is also considered to exist in the white state ; but it passes into yellow by absorbing oxygen. This dyewood was partially superseded for the dyeing of yellows upon cotton by quercitron bark, and both are now almost totally displaced by bichromate of potash and lead. There are still, however, some greens dyed by fustic upon cottcn yam. Tlie yam is first dyed blue by the blue vat, and then passed through a little pyrolignite of alumina ; it is next BARK OR QUERCITRON, 341 wrought in a hot decoction of fustic, which communicates a beautiful rich shade of green. Light cotton fabrics, as gauzes and muslins, are also occa- sionally dyed green by fustic. For this purpose the wood is used in the same manner as the quercitron bai'k. Fustic is also used with other woods for compound shades, as drabs, fawns, olives, «&;c., and is much used with logwood in dyeing black, as well on cotton as upon silks and woollens. Young Fustic, Called also Veneticm Sumach, was long used in France under the name o( fiistet, for giving a yellow dye. These names caused a good deal of confusion, which is to some extent obviated by the prefix young to this wood, the yellow- wood being old fustic. Young fustic is a shrub {rhus cotinus) which grows principally in Italy and the south of France, where it is cultivated for the purposes of dyeing. When cut down it is stripped of its bark, and broken into small pieces, in which state it is met with in commerce. This wood contains a large quantity of yellow-colouring matter namei^fusteric. It is soluble in water, and in that state gives the following reac- tions with other substances : namely, with — Tin salts An orange-yellow precipitate. Iron salts An olive-green colour. Acetate of lead A yellowish-white. Alkalis in solution.... Change the colour to red. This colouring matter has a strong attraction for oxygen, a property which affects its use as a dye. The colours being fugitive, it is seldom used alone as a dye, but as an assistant to strike some particular tint. It is not used in cotton dyeing. Bark or Quercitron Is the inner bark of a tree (the quercus nigra of botanists) which grows spontaneously in North America. Its dyeing properties were first made known to the public by Dr. 342 BARK OR QUERCITRON. Bancroft, in 1784, and were very soon appreciated. Two years after he obtained an act of parliament, vesting in him the exclusive use and application of it for a certain term of years. A decoction of quercitron bark has a yellow-orange colour. If the decoction be made very strong, it deposits a portion of the colouring matter in cooling. It contains a great quantity of tannin, which is always dissolved in the decoction, and which gives the solution of bark a greater variety of uses. A decoction of the bark gives the following reactions with other matters : — Alkalis Deepen the colour of the solution. Lime A precipitate of a yellowish-red colour. Protchloride of tin A yellowish-red precipitate. Alum A slight precipitate cold, but more when hot. Acetate of alumina A bulky reddish -yellow precipitate. Acetate of lead A reddish yellow precipitate. Acetate of copper A greenish-yellow precipitate. Salts of iron Dark olive - green precipitates, passing into brown. Hydrochloric acid) Reddish-yellow precipitates, and mtric acid....) •' r r The pure colouring matter of bark has been extracted and investigated by Chevreul and Bolley. It is termed quercitrine, is a crystalline substance of a sulphur-yellow colour, and like the other extractive colouring matters, is considered to be the oxide of a colo\irless base. The composition of quer- citrine is given as follows : — Carbon. Hydrogen. Oxygen. Water. 16 8 9 1 A decoction of bark standing until it becomes stale, loses much of its dyeing properties. The yellow matter is deposited, and what remains in solution is of a darker hue, and gives a dull colour when used for dyeing. Bark was extensively used in the dye-house for many years for the purpose of dyeing yellow, and almost completely superseded the use of fustic, both from its beauty and also its BARK OR QUERCITRON. 343 cheapness ; but its use for that purpose has been superseded by the bichromate of potash. Its principal use now in the cotton dye-house is to form the ground for certain browns, and for dyeing green upon Ught muslin cloth ; but catechu has now nearly superseded it for browns. The quantity of tiinnin combined mth it makes it very useful for olives ; goods impregnated with iron, and passed through a decoction of bark, take a beautiful olive. When used for dyeing green, the mordant employed is acetate of alumina ; but for yellow, which is now only dyed upon yarn for particular purposes, the mordant used is chloride of tin (spirits). When bark is used for brown upon yams, it is done thus : — The goods are dyed a deep yellow by being steeped in sumach, and then passed through the spirits, out of which they are wrought in a boUing decoction of bark, raised with spirits; that is, having a quantity of spirits put into the bark solution. The goods are washed from this, and afterwards passed through a mixture of logwood and Brazil-wood, according to the shade of bro\vn required. And we would here draw attention to a very interesting fact, observed first by Mr. Thom of Manchester, namely, that amongst the colouring mat- ters and bases there is an elective affinity, which if not studied, will lead to several errors. We quote on this subject from " Parnell's Applied Chemistry :" — " But the combinations of alumina, «&c., with soluble colouring matters seem to be cases of true chemical combina- tion, taking place in definite proportions, and under the in- fluence of different degrees of attractive force for different coloiiring principles. Thvis, alumina has a stronger attraction for the coloiuring principle of madder than for that of log^vood, and a stronger attraction for that of logwood than for that of quercitron. When a piece of cloth impregnated with alumina is immersed in a decoction of quercitron bark, it acquires a fast yeUow colour ; if the same cloth is washed for some time and kept in a hot decoction of logwood, the alumina parts with the colouring principle of quercitron to combine with that of logwood, and the colour of the cloth becomes changed from yeUow to purple. If the same cloth is next immersed for a few hours in a hot infusion of madder, the alumina parts with the colouring principle of logwood to unite witli that of madder, the colour of the cloth changing from purple to red. 344 FLA VINE, The quantity of alumina on .the cloth does not appear to diminish while these substitutions are taking place. These interesting facts were communicated to me by Mr. John Thom of the Mayfield print works." Now the same law is applicable when the mordant is tin ; so that a quantity of goods being dyed yellow as described, and then put into a hot solution of logwood, a quantity of the yellow is displaced by the colouring matters of the logwood and Brazil-wood. Every dyer knows when he has browns of a deep shade, how difficult it is to bring them up, should he fail to strike the proper tint at the first dip ; if be is neces- sitated to continue working in the logwood and Brazil-wood, he is very apt to run his colour poor in j'ellow by dissolving it off; and to remedy this evil he next adds fustic or bark, with very questionable success. We have often experienced these difficulties when dyeing browns by the process described above, with an aluminous mordant upon the cloth instead of tin. Flavine. Withiia these few years a vegetable extract bearing thi.s name has been mtroduced into the art. It is brought from America in the state of an impalpably fine powder, very light, and of a dun colour It is used in the dye-house as a sub- stitute for quercitron bark, to Avhich, for some purposes, it is superior. The mode of preparing it, is by dissolving it in hot water, with which it gives a sort of turbid solution. It should be used when newly dissolved ; for if allowed to stand, it deposits a brownish-yellow mass, in consequence of its not being all completely soluble in water. If boiled in distilled water until all the soluble matter is taken up, and the clear solution decanted, it soon yields a deposit. The colour produced by flavine is never good until raised. A colour dyed by it weakens gradually when a little sul- phuric acid has been added ; but what remains retains its brilliancy by raising, and in respect of this property it differs from bark. The quantity of colouring matter in flavine is very great : its value as compared with bark is as 16 to 1, or one ounce WELD OR "WOLD. 345 flavine is equal to one pound of bark. A portion burned left 4*4 per cent, of ash; and a solution of it gives the following reactions with salts : — Persalts of iron Olive-black precipitates. Protosalts of iron Deep greenish-black precipitates. Protosalts of tin Lemon-yellow precipitates. Persalts of tin Orange-yellow precipitates. Alumina A rich yellow precipitate. Acids lighten the colour of the solution, and alkalis deepen it, rendering it redder. Weld or Wold. This vegetable is extensively cultivated in France, and many other parts of Europe, for the purposes of dyeing yellow. It is found in commerce in snaall dried bundles. The more slender the stem is, the better is it considered for dyeing. Both the seeds and the stems are used, as they both contain the colouring matter ; but the seeds are considered to contain it in greatest quantity. The colouring matter approaches very nearly to that of quercitron in chemical properties ; and of all the vegetable dyes, it is least acted upon by acids and alkalis ; which gives to the dye, so far as these substances are con- cerned, great permanence. But it has this counteracting disadvantage, that the colour rapidly fades or passes away when exposed to the action of air and light ; it then becomes oxidized, and in consequence has been abandoned for almost all purposes where bark can be used. It is still, however, occasionally used as a yellow dye for silks and woollens ; and also for some mixed colours. A decoction from weld is made in the same way as that of most other vegetable dyes : the wood, whether in bunches or chipped, is merely put into a boiler with water and boiled. Sometimes the bunches are put into a bag of coarse cloth. This decoction is of a yellow colour with a reddish tint, and has a bitter taste and a pecuhar odour : — q2 34G WELD OR WOLD. Alkalis Change it to a brighter yellow. Acids Darken the yellow. Alum A yellow precipitate. Protochloride of tin.. A yeUow precipitate. Acetate of lead A yellow precipitate. Sulphate of iron A yellowish-olive precipitate. The colouring matter of this dye has been obtained in needle-shaped crystals by sublimation, and is then termed luteoleine. We have referred to a use to which weld is applied in the making up of pastel and woad vats, (page 313.) The weld was long used as a dye for woollen and silk before it was used for cotton ; its introduction as a dye for this sub- stance is connected with a clever fraud. " In the year 1773, the sum of £2,000 was granted by act of parliament to a Dr. Williams, as a reward for his discovery of a fast green and yellow dye upon cotton yarn and thread. This supposed fast dye was given by the combination of weld witli a certain mordant, the composition of which the patentee was per- mitted to conceal, that foreigners might not enjoy the benefit of his discovery, while he on his part engaged to supply the cotton and thread dyers with his dye at a certain fixed price. The mordant used was supposed by chemists to be a solution of tin alone, or of tin and bismuth, which gives to weld yellow the power of resisting the action of acids and of boiling soap- suds ; although it is not proof against the continued action of the sun and air. This defect, however, was not easily discern- ible, in consequence of the ingenious method which, accord- ing to Dr. Bancroft, the inventor employed to obtain a favourable testimony of the dyers upon the subject. He caused his specimens of dyed yarn to be woven into pocket- handkerchiefs, and gave them to be worn in the pockets of those who were afterwards to attest to the goodness of his dye, and as handkerchiefs worn in pockets were not exposed to the action of the sun and air, this want of per- manence was not discovered until some time after the reward had been paid for an invention which proved of little or no value." sapflower or oarthamus. 347 Turmeric. This is another substance formerly used in dyeing. It is principally brought from the East Indies and from China. It is the roots of a plant named curcuma langa, and resembling ginger ; it is reduced to powder, and in this state is met •with in the market. The colouring matter is extracted by boiling in water; and decoctions of it have a peculiar smell and bitter taste. The colour is very fugitive, fading rapidly in the air; and there is no proper mordant for it. We have occasionally seen it used for giving a peculiar tint to greens and light browns ; but this only could serve for a short time. The colouring principle of this vegetable has also been extracted, and is known in chemistry under the name of curcumine. A decoction of turmeric, or paper dyed with it and kept from exposure, is much used in testing for the presence of alkalis, which give to the dye a red-brown colour. Persian Berries. These berries are the root of the rhamnus tinctoria, a plant growing in the Levant and south of France, &c. They yield a bright-yellow colour, used by artists and occasionally by dyers; but the dye is very fugitive. There are two kinds of Persian berries ; one large, plump, and clear in colour, the other small, wrinkled, and brown. The colouring matter of each kind has also certain distinctive properties, caused, it is believed, by the one being in full maturity, the other unripe. The large and mature berries are the best, giving a greater quantity of dye, and of superior quality of colour. The colouring matters extracted from the two varieties are named chryso - rhamnine and xantho - rhamnine. These have some interesting reactions with bichromate of potash, and other oxidizing agents. Safflower or Carthamus. This is an annual plant, cultivated in Spain, Egypt, and the Levant. There are two varieties of it, one liaving large leaves, and the other smaller ones ; the hist is the best. 34!^ SAFFLOWEE OR CARTUAMCS. It is only tbe flcwer of tlii: plant that is used for dyeing. Wlien the flowers are gathered, they are squeezed between two stones to express their juice ; they are afterwards washed with spring water ; next taken in small quantities and pressed between the hands and laid out upon mats to dry. These cakes are covered up during the day to prevent the sun from shining upon them — which would not only destroy the colour, but dry the cakes too much, and thereby cause further deterioration. They are kept exposed to the dews of night, and turaed over occasionally, till dried to the proper point, when they are packed up for the market. It is in this state they are procured by the dyer. Safflower contains two colouring substances. The one is yellow, very soluble in water, and of no tise to the dyer. To free the safflower from this yellow-colouring substance is a panicular part in the manipulation of this dyestuff. The other colouiing substance is red, and is extracted from the vegetable after the yellow substance has been washed away, by means of alkahne carbonates. This substance is used very exten- sively for dyeing the various shades of pinks, crimsons, roses, &c., upon silk, and also for the same colours upon cotton, with lavender, lUac, pearl-white. The mode of preparing saf- flower for the purpose of extracting the red matter from it, was for a long time that recommended by BerthoUet, and fol- lowed by all other writers upon the subject ; namely, putting a quantity into a fine bag, "tramping" it with the feet in water until the yellow colour was dissolved and washed away; the mass left was then treated with an alkali to extract the red matter. But although this red- colouring matter is insoluble in water, it wUl be fovmd that the bag in which it Ls tramped becomes a deep crimson-red, which can only be pro- duced by its imbibing this red matter. It proceeds, we think, from a very fine powder, probably carthamttie, adhering to the stuflFlike the pollen of the flower, and which floats away in the water. It is much heavier than the ordinary carthamine, and collects as a sediment at the bottom of the vessels used to hold the safflower ; but when tramped in bags, this powder is ex- pressed and imbibed by the bag, which becomes strongly dyed, thereby causing a loss of the dye. To avoid this, the saf- flower is now put into a tub without any bag, with as much water as will cause the whole to float freely. A very Utile SAFFLOWER OR CARTHAMUS. 349 tramping or agitation is sufficient to reduce the cakes to a soft flocculent mass, which is the sole use of tramping. It is next removed to a cask or tub, provided with a false bottom, covered with fine haircloth. In the lower or true bottom, is a plug-tap. This vessel is filled with clean water, which is let out by the plug at the bottom ; it is filled again, and so on, until the water passing through is not coloured yellow. After this, there is put into it a measured quantity of pure water — about three gallons to the pound of safflower — in which is dissolved a little carbonate of soda, or carbonate of potash, (pearlash does well,) about an ounce to the pound of safflower. Some kinds require less than others ; but care ought to be taken that too much is not used, as it destroys the brightness of the colour. This, being dissolved in water, is put into the tub containing the safflower, well stirred, and allowed to stand for about seven hours ; the plug is then taken out, and the clear liquor drawn into a proper vessel. This liquor contains the red dye which has been extracted by the alkali. The remaining safflower is afterwards washed by pouring upon it a little more water made slightly alkaline, and allowed to steep a short time; but if fine light colours are to be dyed directly from the solution, this second extract does not answer so well, as the shade is not so pure. This second extract is commonly kept and used instead of clear water for the next parcel of safflower ; or if it is wanted for this purpose, a little acid is added to the liquor, and a piece of old cotton is allowed to steep in it until it has extracted all colouring matter, and which is afterwards re- covered for use, as will presently be described. The liquor extracted from the safflower contains both red and yellow-colouring matter. For this reason silk goods are not dyed directly by this extract, as the silk takes up a por- tion of the yellow, which renders the colour more of a brick hue than is due to the rose and pink. To dye sUks, any old cotton yarn is dyed first by the safflower extract ; the cotton takes up nothing except the red. This cotton is then tho- roughly washed in cold water till the water coming from it is perfectly clear ; it is then steeped for a little in water made slightly alkaline by carbonate of soda or potash, which ex- tracts the red from the cotton, and forms the dyeing solution for silk. The silk to be dyed pink, generally receives a bot- tom or ground by passing it through a weak solution of cudbear 350 SAFFLOWER OB CAETHAilUS. or archil, so as to form a flesh or Ught lavender colour — the depth being regulated according to the shade of pink wanted. It is then put tlirough the saf&ower solution, which must pre- viously be rendered acid by a little lemon-juice, vinegar, or sulphuric acid, "When the safflower Kquor is exhausted, the silk is washed in cold water, and finished by passing through a little water made acid by lemon-juice or tartar ; neither vine- gar nor sulphuric acid should be \ised in the finishing process. To dye cotton pink, the liquor is used as extracted from the vegetable ; the goods require no previous preparation, except to be well bleached. The quantity of liquor used varies according to the shade required ; one pound of safflower to the pound of cotton gives a dark rose ; and the other shades in proportion, according to the tint required. The goods are first wrought in the alkaline solution for five or six minutes and then taken out, and vitriol added to the solution xintil it tastes decidedly sour ; the goods are again immersed and kept working in this tiU the solution is per- fectly exhausted. The ascertaining of this point requires a little experience, as exhaustion is known by the operator holding a Httle between him and the light ; when, if there is no tinge of red, the solution is spent. The goods are now to be well washed by passing them through three or four tubsful of clear cold water ; they are then finished by passing them through a little water, with just sufficient tartar to make the liquid taste sour. It must be borne in mind that, in dyeing with safflower, the water ought to be pure and always cold ; a very little heat destroys the beauty of the colour ; the goods ought also to be dried cold, and preserved carefully from sunshine. The colours obtained by safflower are the prettiest that can be had upon cotton, but they are fugitive. The most beautiful lilacs, puces, and lavenders, are obtained by safflower and prussian blue ; but it is one of the most diffi- cult colours to produce of equal shade. The goods are gene- rally first dyed a blue by nitrate of iron and prussiate of potash, (see page 160,) and then put through the safflower solution, previously made acid ; but the rapidity with which the cloth takes up the red, renders it almost impossible to get a perfectly even dye. Another method is to dye the cloth in the first instance pink, and then to dye it blue. This method SAFFLOWER OR CARTHAMUS. 351 gives a more equal dye, but it is liable to serious objections. The nitrate of iron used acts upon the colouring matter, oxi- dizing and destroying its beauty and depth, thus causing loss, and making this colour exceedingly expensive. Persulphate of iron may be used instead of the nitrate, as it is not so corro- sive, and will preserve the tint of the safflower much better. We mentioned in our introductory remarks that one essen- tial condition in all dye-drugs, before they could be used as such, was that they should be in solution ; but carthamus is an exception to this rule : when it is in a soluble state, it is not a dye, and must be rendered insoluble before it mil act as such. Although the cotton is generally passed through the alkaline solution before acid is added, still this will not pro- duce the dye, but merely secures an equalized colour under the rapid action with which the fibres imbibe the solid colour- ing matter after acid is applied. Tliis fact favours the opinion that the cotton imbibes the colouring matters in the same way as they arc imbibed by charcoal — the fibres of the cotton, like those of silk and wool, being hollow. This action is not merely a capillary attraction, such as shown with glass tubes. When very small glass tubes are placed with their ends dipping into a solution, the fiuid is observed to rise in them to a great height inversely as the hol- low diameters of the tubes, and then remain stationary ; but if such tubes are placed in a vessel containing the carthamus in suspension, although they become filled vnth. the liquor they do not exhaust the liquor of the suspended colouring mat- ter ; whereas the fibres of the cotton, placed into this fluid, extract all the colouring matter from the water, and become hterally filled with it. Thus, if we take a vessel filled with water, having in it carthamus rendered in- soluble by an acid, and suspend a skein of cotton in it for a few hours, the cotton will absorb the whole co- louring matter, and leave the solution clear — indicating thereby a distinct power of attraction exercised between the fibre and coloui-iug particles, and also a circulation of the 352 SAFFLOWER OR CARTHAMUS. fluid through the fibre or tubes of the cotton, which, indeed, is true, more or less, of any solid substance so finely divided as the carthamus, and diffused in water along with fibres of cotton. In the case of precipitates, the more dense they are the smaller is the quantity of solid matter imbibed by the fibre. When a little safflower solution has an acid put into it, and is allowed to stand for a time, the red carthamiue precipitates as a fine red lake, and is sold as such adhering to saucers for dyeing ribbons, &c. An extract of safflower has also been recently introduced into the market for the use of dyers, but we have, as yet, had too Uttle experience of its use to speak of it with confidence. Although safflower colours may be the most simple and easily dyed of all others, still, from their deUcate reactions with other matters, there are few substances subject to so much risk of being destroyed. If the water is not pure they will dry brown. A httle acetic acid, cream of tartar, or tartaric acid, is generally added to the last water from which they are finished to preserve the tint ; but too much or too Uttle of these will produce perceptible efiects upon the shades. Great care has to be taken in the drying : it should be done in a perfectly dry stove, not hot, and having ample space between each parcel, as a very little steam produces a yellow surface. The goods are generally dried in the cold ; but care is neces- sary that no sun-rays touch them ; also that they are not injured by steam or smoke entering the sheds where they are drying. If all necessary precautions are not taken, the dyer has the mortification, as well as expense, of putting the goods through at least the last acid solution, and if they are much touched, he is obliged to re- dye them. The view that carthamine, or the red-colouring matter of safflower, is the oxide of a colourless base, as in the case of the woods we have referred to, has been objected to by many in- vestigators, whose experiments and reasoning bear evidence of care and judgment; thus adding an interest to the subject of vegetable colouring matters, and showing the practical man that there is yet before him much to be discovered, and that a careful observation of all the reactions and circumstances connected with his operations will stand a fair chance of being rewarded with success. 353 Madder. This vegetable rivals indigo as a dye-drug, both from the beauty and permanence of the colours it produces, and also from the variety of shades which it is capable of furnishing by the combinations of its colouring matters. It is the root of a plant or shrub called rubia tmctonu7n, cultivated in the Levant, and in several western countries of Europe, especially in France and Holland. The East Indies also furnish a quantity of it, and within these few years a large importation has taken place of a species termed nibia 7nemsr/ista, which contains mxxch more colour- ing matter than the best madders of Europe. Its culture has been often attempted in England, but without success. In the Levant the madder is collected only once in five years ; but in France it is gathered every three years. It is only the root of the plant that is used for dyeing. In removing the root from the ground, it is carefully cleaned, and, when the season is favourable, it is spread out in the air to dry. French madder is generally more imperfectly dried than that from the Levant, and consequently contains more water of vegetation, and to that extent it is comparatively less valuable. It is sometimes dried in a stove, to allow it to pulverize. The dryness of the article is judged of by the fracture when a piece of the root is broken transversely by bending it. When the roots are perfectly dry, if they are broken or cut with a knife, they present to the eye a reddish-yellow colour, which passes to a dense brownish-red when the piece is mois- tened'; but the more yellow the root appears when dry, the more coloui'ing matter does it yield. Madder, when fresh, and after being cut or ground to powder, (in which state it is generally used by the dyer,) has a heavy sweet smell, with a somewhat earthy flavour. The product of grinding is generally of three kinds. The first is formed of the epidermis, or skin of the roots, and comes off in fine filaments by slight pressure. This is collected separately, and forms what is termed the mull — which is of very inferior quality. The second consists of the annular portion of the root ; and the third of the Ugneous or centre portion ; but generally these two qualities are mixed. The varieties of madder in commerce arc distinguished by 354 MADDER. the name of the country from whence they are brought, and by the appearance they receive in the preparatory process through which they pass previous to their reception at the dye-house. JLevant Madder is in the form of shoots or fibres, of greater or less length, and very slender ; brown externally, and pale orange-red internally. It is merely cleaned of earth and dried, and is imported from Smyrna, Cyprus, &c. Dutch iriadder is ground, but so very coarsely as to en- able the buyer to judge of the nature of the root from which it is prepared. It has a greasy feel, and a strong nauseous odour. Its colour varies from a brown to an orange-red ; the brown is inferior. It becomes damp when exposed to the air, a property which can be taken advantage of to judge of its quaUty : if a little of it is exposed in a damp place, when good, its colour passes from the brownish-orange tint to a deep red. The madder of Holland is said to be cropjyed or uncropped, according as the barky matter of the root is separated or not, from the ligneous part in the process of pounding through which it passes. This madder is never employed fresh, but is kept at least a year, and it is better to be kept three years before it is used. It may be kept several years longer without being impaired. During the first years it is kept it undergoes some internal change, and becomes much brighter in colour ; the powder adheres together, forming a mass very difficult to remove from the cask, and swells so, that the bottom of the cask often assumes a convex form. If kept for too long a time it becomes deteriorated : the portion in contact with the cask loses its brilliancy, and becomes brown, and this change gradually extends through the whole mass. After this change has taken place, it is unfit for dyeing fine reds or light tints, and can be used only for dark colours. The marks of Dutch madder are — MullO ■> rMuU. Superfine >- or < Fine pulverized. Cropped or uncropped) (Superfine pulverized. Alcasc Madder.— This madder is met with in commerce in a state very similiar to that of Dutch madder ; but although the operation of cropping is generally performed upon it, that term is not used in designating it. It readily absorbs mois- VARIETIES OF MADDER. 355 ture from the air, and also acquires a deep-red tint when exposed in a damp atmosphere, as that of a cellar. Like Dutch madder, it is not employed fresh : it is in its best con- dition when about two years kept, but it deteriorates much sooner by keeping, and also agglomerates into a mass, and swells. It is inferior to the madder of Holland ; its odour is more penetrating, and its taste less sweet, but with an equal degree of bitter; its colour is more yellow, passing into brown, with much less of the orange tint. A little experience in comparing the two sorts soon enables the dyer to distinguish the one sort from the other. madder of Arignoa. — This madder is deservedly much esteemed. There are several varieties of it, some due merely to the modes of preparation, and others to the soil on which the plant grows. It is ground into a fine powder, which feels dry to the touch, and does not absorb moisture so readily as the other kinds of madder ; but when exposed to a humid atmosphere, it also undergoes a change. Its odovu- is very agreeable ; the taste a mixed sweet and bitter, the last predo- minating ; and its colour varies from a pink or rose hue to a deep red, or reddish-brown. The best qualities ai-e obtained from those roots which grow in marshy or swampy ground, and places enriched by admixture of animal or vegetable matters. The roots from such a soil are generally of a deep- red colour, while those from less favourable grounds are of a rose or pink tint. It is by mixing these kinds in different proportions that the variety of madders from this locality are obtained. The several qualities have various marks, besides the ordinary marks, as — P. to signify Palus, (marshy.) R. — Roseate. P.P. — Pure joa/iis, (marshy.) R. P. P. — Purest red palus, (marshy. ) The actual commercial marks, according to the order of their quality, are — S. F. for superfine — containing all the matter of the root. S. F. F. for fine superfine — containing all the hgneous matter of the root, the mull or bark, or out- side portion being separated. 356 MADDER. E. S. F. F. for extra fine tine — containing the heart or centre of the root, and the internal part of the oily ring which surrounds it ; being also t^vice sifted so as to separate completely from the mull, &c. These three varieties may themselves vary according to the nature of the roots, and the manner in which they are dried, and otherwise prepared ; but it is from these that all the various mixtures are made ; and the tact of the manufacturers con- sists in mixing them so as to produce the quaUties required by the consumer. Avignon madder can be used fresh, although it is better to be kept for twelve months. It does not cake or agglomerate in the cask, but when kept too long it becomes deteriorated in quality, undergoing the same kind of decomposition as the other madders. ^Madder is often adulterated by mixing with it brick- dust, red or yeUow ochres, sand, and clay, or by adding sawdust of certain woods, as mahogany, logwood, sandal- wood, &c. &c. The mineral adulterations may be detected by putting some of the suspected madder in a large glass ves- sel, and adding to it a quantity of pure water : the madder floats, and the mineral adulterations sink to the bottom. We thus readily obtain an approximate idea of the quantity of adul- terating matters present, and by carefully removing the float- ing madder, and then filtering the Uquor, the mineral sub- stances may be separated and weighed. We may also proceed by burning a small portion of the madder and seeing the ash that remains ; we have in this way tried various samples, having 8-g- per cent, of ash. When the adulterants consist of sawdust or other ground vegetable matters, their detection is much more difficult; in- deed, the only means likely to be at all successful, is to weigh a portion of the suspected madder, and to try its colouring powers by a piece of prepared cotton : except where chemical skill can be applied, the coloiuing matter of the madder can be extracted, and compared with other known quahties. Some of the French dyers use a colorimeter for judging of the quaUty of their madder. It depends upon a principle similar to that of Mr. Crum's chlorimeter for testing the ALIZARIN. 357 strength of bleaching powder, (see page 81.) A weighed quantity of madder, of known quaUty, is boiled, and the de- coction is put into a glass vessel ; similar quantities of the madders to be tried are treated in the same manner, and placed in a glass vessel of similar size and form, and the tint of colour is judged by comparison. Of course, the test solu- tion may be diluted by a measured quantity of water, and by using a graduated glass, their comparative values, estimated by the rate of dilution, &c., may be easily ascertained. But this method is subject to many errors, as when any adultera- tion has been practised on the madder, by addition of other vegetable colouring matters, such as sapan-wood, «fec. Madder has been the subject of a great many chemical in- vestigations, the study of which is highly useful to those who use this dye-drug in their operations.* The first investigation into the chemical properties of madder led to the discovery of two distinct colouring matters — one yellow, which is very soluble in cold water, and named xanihin; the other red, moderately soluble in hot water, is called alizarin. Several methods of extracting alizarin by sulphuric acid have been proposed, but the following is probably the most simple in practice : — " One pound weight of madder is mixed up with an equal weight of concentrated sulphuric acid, the vessel so closed up that no heat is evolved, and allowed to stand in a cool place for three or four days: by this pro- cess all the constituents of the madder are converted into charcoal, except the alizarin. AVhen this charring pro- cess is completed, the mixture is carefully dried, and then digested in alcohol, which dissolves the alizarin and leaves the charcoal. The solution may now be diluted with water, and put into a retort, and kept at a heat of 170" Fah. : the beak of the retort being connected to a receiver, the alcohol distils over, and is recovered. Water and alizarin remain in the retort, which being poured out and filtered, the alizarin remains upon the filter in a state of great purity. It is of a beautiful red colour, and gives the same colour to boiUng water. Alizarin is soluble in turpentine, naphtha, and fat oils ; chlorine turns it into a yellow-brown ; sulphuric acid dis- • See 2d, 5th, and 6th vols. Chemical Gazette ; 1st vol. of Pharmaceutical Times ; 33d vol. Phil. Magazine, &c. ; Thomson's Vegetable Chemistry. 358 MADDER. solves it, and, at the same time, enlivens the colour ; miiriatic and nitric acids both dissolve it, changing the colour from red to yellow. Alkalis A violet colour. Alumina A deep red-brown precipitate. Oxides of tin Precipitates of the same appearance. Phosphates have a very powerful attraction for ahzarin, so much so, that when animals take any madder into their sys- tem, the bones, which contain a considerable quantity of phos- phates, become coloured red. This fact is well known to dyers who are in the habit of using madder in their opera- tions, and necessarily often tasting it. When taken in quan- tity, the urine is coloured by it. From the above reactions of alizarin with other substances, it was supposed that it constituted the true colouring of mad- der ; and means were soon adopted to separate this coloiuring matter from the vegetable, and use it pure ; but it was after- wards found that a fixed dye coxild not be obtained by pure alizarin, and therefore it did not constitute all that was required in giving the dye. This led to further investigations, produc- tive of further discoveries respecting these colouring matters. It finally appeared that madder has five different colouring matters, which have been named — Madder purple, I Madder orange. Madder red, | Madder yellow, ^Madder brown ; each of which may be obtained by the following opera- tions: — nadd<>r Purple .—The madder is washed in water at about summer heat, then boiled in a strong solution of alum for an hour ; the clear liquor is afterwards decanted, and sulphuric acid added, which precipitates the madder purple along with a number of impurities. These are removed by washing with boiling water, then with pure muriatic acid, and afterwards dissolving in alcohol. Madder purple is soluble in hot water; and if pure it gives the water a dark-pink colour. If the water contains lime, a great part of the colouring matter is precipitated as a reddish- brown substance. Cotton, saturated with the acetate of alumina, is dyed a bright red, provided COLOURING MATTERS. 359 the quantity of madder purple be not too great for the alumi- nous base, but if so, the colour will have more of a purple tint. A boiling solution of alum forms with the madder purple a cherry-red solution ; caustic potash forms with it a fine yellowish-red colour ; the carbonate of potash and soda have a similar effect ; and sulphuric acid produces a bright red or rose colour. madder Red is separated from madder purple in conse- quence of its not being soluble in a strong solution of alum. It is obtained by boiling madder in a weak solution of alum, by which a reddish-brown precipitate is obtained. This pre- cipitate is repeated, and boiled in pure muriatic acid, then washed carefiilly with water and boiled in alcohol. This dis- solves both madder red and madder purple ; but by gently evaporating the alcoholic solution until it is very much con- centrated, and then allowing it to cool, an orange-coloured precipitate is formed, which is collected and repeatedly boiled in a strong solution of alum, as long as the alum solution comes off coloured : the insoluble portion is madder red. It is a yellowish-brown powder, and imparts to cotton, impregnated with acetate of alumina, a dark-red colour, when in excess ; but if the mordanted cotton be in excess, a brick-red colour is produced. Caiostic potash gives a violet, carbonate of soda a red, and svilphuric acid a brick-red solution. Madder Orange is distinguished from the two former colours by its shght solubility in alcohol. It is prepared by macerating madder for twenty-four hours in distilled water, the infusion being strained off and allowed to repose a few hours. The liquor is carefully decanted and filtered through a paper filter, upon which the madder orange remains. It may be washed with cold water, and afterwards purified by spirits of wine, in which it is not soluble. It is a yellow powder, soluble in boiling water, and imparts to cotton impreg- nated with an aluminous mordant a bright-orange colour, when in excess. A boiUng solution of alum forms with mad- der orange a yellow solution; caustic potash gives a dark rose, carbonate of soda an orange, and sulphuric acid an orange-yellow colour. madder iTellow is characterised by its great solubility in water. It is a yellow gummy mass ; communicates to mor- danted cotton a pale-nankeen colour, but does not of itself 360 SIADDER. form a true dye. Madder which contains much of this ingre- dient is of inferior quality, as the yellow becomes so incor- porated with the other colours, as materially to deteriorate them, and to require several operations to free the goods from it afterwards. Madder Brown is a brownish-black dry mass, obtained in the preparation of the other colouring matters. It is neither soluble in water nor alcohol, is of no importance as a dye- drug, and does not enter into any of the colours dyed by madder. madder Acids.— Besides these five colouring matters, mad- der contains two acid substances, named viadderic and ruhiacic acids. They have no known dyeing properties, and are only mentioned here to show the intimate knowledge which chemists possess of this agent ; indeed, so important were any investigations in madder considered, that the Societe Industrielle de Mulhouse for several years offered 2,000 francs as a pre- mium for the best analytical investigation of this substance. Usefnl Products.— It will be observed in this brief outline of the colouring matters of madder, that only three of them are of importance to the dyer, viz., the red, purple, and orange. It will also be observed that these three colouring substances have a similarity of action towards mordanted cottons. Taken singly, not one of them forms a good dye ; but they constitute the elements which together produce the richest and most permanent reds which the modern dyer possesses. Indeed, practically it is only necessary to consider madder as containing no more than two coloui'iiig matters, as was formerly supposed, viz., — the dun or yellow, which consti- tutes the impurity of the madder, and which the dyer endeavours to get rid of, and the red-colouring matter. The former, or yellow, does not combine with the cloth alone, and probably not at all, but it has a strong affinity for the other colouring matters, and combines with them when they are upon the cloth, and has to be separated from them by afler processes. The latter, or red, which is a combination of all the three, the red, the purple, and the orange, unites with the cotton as one, and is known to the dyer only in the aggregate state. This colouring matter is difficultly soluble in water, and therefore no strong decoction of it can be obtained by boiling, so that it is not very apphcable for compound MADDER PREPARATIONS. 361 colours, and therefore of little avail in the fancy dye-house. Many extensive fancy dyers, indeed, do not consider madder as even belonging to tlieir province. They use it very seldom, except to give a peculiar tint to some light compound colours, and for fast salmon colours, pinks, «S:c. When deep colours are to be dyed by madder, the goods must be put into the dye-bath or boiler along with the madder, in a way nearly similar to that described for barwood. Madder in the hands of the skilful operator can be made to produce a vast variety of colours and tints, by corresponding changes of his mordants, and the colours are all characterised by a degree of permanency which no other vegetable dye- wood produces. The operations, however, are generally much more tedious than those for ordinary fancy colours ; and much skill is also required in preparing and applying the pro- per mordants for madder colours, and also in the preparation of the cloths for the different mordants. Madder Preparations There are two colouring substances prepared from madder, which are now being much used in dyeing and calico printing, and which seem to embrace all those different colouring principles we have been describing ; these are garancine and colorine. The former was first formed and described by MM. Robiquet and Colin, as far back as 1828 ; but it was long before it was introduced generally to the trade. Gai-ancine is a chocolate-coloured powder, having no taste or smell ; but from differences in the modes of pre- paration, and also in the qualities of the madders from which it is prepared, it varies very much in quahty, which is pro- bably the reason why it has been repeatedly taken up and abandoned by dyers. Ultimately, however, means of testing its quality, «&c. were devised, and have proved favourable to its more constant employment. The manner of forming garan- cine, as given by MM. Robiquet and Colin, is to take one part of madder, and five or six parts of cold water, and allow the mixture to macerate till the following day ; the whole is then thrown upon a cloth -filter, and when drained is subjected to pressure. It is then to be steeped again in cold water and pressed, and so on for the third time. When these operations are completed, almost half as much sulphuric acid (by weight) as there was of the madder in its first state, is to be diluted with water, so as to raise the temperature as much as possible, and R 362 JIADDER. this is added to the pressed madder while hot, and stirred as rapidly as possible : the temperature is then raised and kept at 212° for about an hour. A quantity of water is then added, and the whole is thrown upon a filter ; water is poured over the residue until it passes through the filter without taste of acid, and the matter collected is then pressed and dried, and passed through a sieve. This constitutes garancine. The sulphuric acid used is not altered in character, but seems only to have carbonized some of the impurities in the roots, with- out affecting the red-colouring matter. There are several other methods of preparing this substance, but not differing essentially from that described ; as throwing the rough mad- der into water, and heating it to the boiling point, then adding the sulphuric acid, after which the whole is filtered, washed and dried, and reduced to powder, &c. During these few years the consumpt, and consequently the manufacture of garancine, has greatly increased. The mode of testing garancine is similar to that described for madders ; either by the depth of dye produced on mordanted cotton, or by means of the colorimeter. In 1843 a patent was taken for extracting garancine from the waste madders of the dye-house, and we believe has been productive of great saving and advantage. The substance of the process thus patented is : — •'The invention consists in manufacturing a certain colour- ing matter called garancine from refuse madder, or madder which has been previously used in dyeing, such madder having ordinarily been thrown away as spent and of no value, and the said colouring matter called garancine having been produced heretofore from fresh or unused madder. A large filter is constructed outside the building in which the dye- vessels are situated, formed by sinking a hole in the ground, and lining it at the bottom and sides with bricks without any mortar to unite them. A quantity of stones or gravel is placed upon the bricks, and over the stones or gravel com- mon wrappering, such as is used for sacks. Below the bricks is a drain to take off the water which passes through the filter. In a tub adjoining the filter is kept a quantity of dilute sulphuric acid, of about the specific gravity of 105, w^ater being 100. Hydrochloric acid will answer the several purposes, but sulphuric acid is preferred as more economi- cal. A channel is made from the dye-vessels to the filter. GARANCINE. 363 The madder which has been employed in dyeing is run from the dye-vessels to the filter ; and while it is so running, such a portion of the dilute sulphuric acid is run in and mixed with it as changes the colour of the solution and the undis- solved madder to an orange tint or hue. This acid pre- cipitates the colouring matter which is held in solution, and prevents the undissolved madder from fermenting or other- wise decomposing. When the water has drained from the madder through the filter, the residuum is taken from oflf the filter and put into bags. The bags are then placed in a hydraulic press to have as much water as possible expressed from their contents. In order to break the lumps which have been formed by compression, the madder or residuum is passed through a sieve. To 5 cwt. of madder in this state, placed in a wood or lead cistern, 1 cwt. of sulphuric acid of commerce is sprinked on the madder through a lead vessel similar in form to the ordinary watering-can used by gardeners. An instrument like a garden spade or rake is next used, to work the madder about so as to mix it intimately with the acid. In this stage the madder is placed upon a per- forated lead plate, which is fixed about five or six inches above the bottom of the vessel. Between this plate and the bottom of the vessel is introduced a current of steam by a pipe, so that it passes through the perforated plate and the madder which is upon it. During this process, which occupies from one to two hours, a substance is produced of a dark- brown colour approaching to black. This substance is garan- cine and insoluble carbonized matter. When cool, it is placed upon a filter and washed with clear cold water until the water passes from it without an acid taste. It is then put into bags and pressed with a hydraulic press. The substance is dried in a stove and ground to a fine powder under ordinary madder stones, and afterwards passed through a sieve. In order to neutralize any acid that may remain, from 4 to 5 lbs. of dry carbonate of soda for every hundredweight of tlUs sub- stance is added and intimately mixed. The garancine in this state is ready for use." — Sealed August 8, 1843. The following is the action of garancine when put into different qualities of water and mth re- agents : — 364 BIADDEE. Distilled water, cold A pale yellow in about 24 hours. Distilled water, boiling ...A pale reddish-yellow tint. Spring water, cold Less coloured than ■with cold distilled water. Boiling spring water Less coloured than with boil- ing distilled water. Cold lime water Paler than with either cold distilled or spring water, "Water with a Uttle sul-) Greenish - yellow tint after phuric acid J some hovirs. Water with H CI The same, but darker in tint. Water with NOj Still darker tint, passing into a brownish-blue. "Water with acetic acid... Faintly yellow. Strong acetic acid Acquires a beautiftd reddish- yellow colour, /^Becomes red immediately, and Ammonia < after a few hours so deep as (^ not to be transparent. "Water with ammonia Beautiftil red colour. A solution of caustic^ ,-. , , •, J > Dark red-brown, soda J Water with carbonate^ -d • i.^. jj- u i - J > Bright reddish colovir. 01 soda J = Cold alum water Chrome-red colour. Boiling alum water A dark-red colour. The mordants used for dyeing with garancine are the same as for dyeing with madder. It only yields its colour to the mordanted cloth at a boiling temperature, and the water of the bath or boiler does not become coloured. A Uttle sumach is often \ised along with the garancine for reds. If the water used in dyeing be a calcareous spring, a little sulphuric acid, just enough to give the water a sour taste, should be added, but when sumach is used, the acid is not reqiiired. The dye obtained by garancine is generally more brilliant and Uvely than fi"om madder. In printing the colour is not so liable to run upon the white, and the goods are consequently more easily cleared than when madder is used. Coiorine is the residue left by distilling the alcohohc tinc- ture made by treating garancine with spirits of wine. It is ANNOTTA, OR ARXOTTO. 365 considered to be impure alizarine. When this product is taken from the retort, it is in the form of an extract ; but diluted with water, separated, subjected to pressure, and then dried and pulverized, it resembles yellow ochre. It leaves a deep stain on the fingers if moistened by it. It is prepared in France at a cheap rate, and used in calico printing by being dissolved in ammonia, thickened with gum, and applied to the cloth previously mordanted. The mordants used for madder and the colouring prepara- tions obtained from it, are the acetate of alumina, acetate of iron, and mixtures of these ; the chlorides of tin, acetate of lead, and acetate of copper, and sometimes ammoniuret of copper. The last two are often used as alterants. In using Lron mor- dants it is of the utmost consequence that they be the proto- salts ; hence iron liquor is more frequently used than sulphate of iron, which salt is more apt to become peroxidized. In dyeing with madder there are many operations not prac- tised in the fancy dye-house, such as dunging, &c. MUNJEET Has been tried as a substitute for madder. It con- tains more colouring matter, and is found in commerce in bundles consisting generally of thick and thin stalks ; the thin stalked variety contains less colouring matter than the thick, and has the bark on ; whereas the thick stalks are barked. The stalks of the munjeet are very dry, light, and porous ; the fracture exhibits a congeries of empty tubes. The powdered munjeet is composed of the thin and thick stalks mixed. Reds dyed with munjeet are very briUiant, but fugitive, being destroyed by a short exposure to light and air. This vegetable cannot, therefore, be a proper substitute for mad- der. Annotta, or Arnotto. This substance, the Roucou of the French dyers, is ob- tained from a shrub originally a native of South America, and now cultivated in Guiana, St. Domingo, and the East 366 ANNOTTA, OR ARNOTTO. Indies. It is termed the annotta tree, or hixa orelhvia, and seldom exceeds twelve feet ia height. The leaA'es are divided by fibres of a reddish-brown colour, and are four inches long, broad at the base, and tending to a sharp point. The stem has likewise fibres, which in Jamaica are converted into ser- viceable ropes. "The tree produces oblong bristled pods, somewhat resem- bling those of a chesuut. These are at first of a beautiful rose colour, but, as they ripen, change to a dark-brown, and bursting open, display a splendid crimson farina or pulp, iu which are contained from thirty to forty seeds, somewhat resembling raisin stones. As soon as they arrive at maturity these pods are gathered, divested of their husks, and bruised. Their pulpy substance, which seems to be the only part which constitutes the dye, is then put into a cistern, with just enough water to cover it, and in this situation it remains for seven or eight days, or until the liquor begins to ferment, which, how- ever, may require as many weeks, according to circumstances. It is then strongly agitated with wooden paddles or beaters to promote the separation of the pulp from the seeds. This operation is continued until these have no longer any of the colouring matter adhering to them ; it is then passed through a sieve, and afterwards boiled, the colouring matter being thrown to the surface in the form of scum, or otherwise allowed to subside : in either case it is boiled in coppers till reduced to a paste, when it is made up into cakes and dried." * Another and more preferable mode of extracting the colour- ing matter from these seeds, is by rubbing them one against another under water, so that the mucilaginous and other im- pure matters contained in the interior of the seed are not mixed in it. The colouring matter is allowed to settle, the water drawn off, and the annotta left to dry. When prepared in this manner, it has a fatty feel, is very homogeneoxis, and of a deep-red colour, which changes to dark-brown by drying. It has no taste, but generally a disagreeable smell, when brought into commerce. This smell, however, is not natural, but is owing to stale urine having been added to it, in order to improve its colour, and keep it moist. * Annales de Chemie, tome 47. ANNOTTA, OR ARNOTTO. 367 The Carribee Indians prepare the aunotta, which they em- ploy for painting their bodies, by smearing their hands with oil, and then rubbing the seeds until the pulp is separated under the form of a paste, which adheres to their fingers, and which they remove with a knife and dry in the sun. Annotta of good quality is of a lively red colour when just taken from the seeds, and before it has undergone any change. It was found by Mr. John to contain the following ingredients : — Colouring and resinous matters 28*0 Vegetable gluten 26*5 Lignine 20-0 Extractive colouring matter 20*0 Matter resembling gluten and extrac- tive 40 Aromatic and acidulous matters 1.5 100-0 Boiling water dissolves annotta, giving a thick decoction of a yellow colour. Alkalis form with it a white precipitate, giving the liquor a clear orange colour, which acids make redder. Muriatic acid has no action upon annotta ; chlorine destroys its colour. Nitric acid completely decomposes it, forming several compounds, which have not yet been sufficiently ex- amined. Sulphuric acid poured upon solid annotta gives it a deep-blue colour, not unlilce indigo, but it soon changes to a dark dirty-green, and then to a blackish-purple. The colouring matters of annotta are easily soluble in alka- lis, and in this condition they are generally used in the dye- house. The alkali used is either carbonate of soda or potash ; and when light shades upon silks and fine cottons are wanted, soft soap is used. Sometimes a quantity of annotta is pre- pared and kept as a stock liquor ; but the practice is bad, as the liquor soon becomes stale, and loses a great portion of its dyeing properties. It is best when newly prepared. A good method of preparation is the following : — Into a boiler, capable of containing 10 to 12 gallons of water, are put 10 pounds weight of annotta, 2 lbs. of carbonate of soda, and 2 lbs. of 368 ANNOTTA, OR ARNOTTO. soft soap, and the mixture is boiled until the annotta is all dis- solved. Cloth put into this solution is dyed a dark orange, but every shade, from an orange to a cream colour, can be dyed with it by merely using it in a proper state of dilution with water. The cloth requires no previous preparation ; but for fine hght shades the colour is improved by dissolving a little white soap in the water used for diluting it. The goods are merely passed through the solution, and dried from it ; but where the colour is strong, the cloth must be washed in water containing a little soap, to free it from the strong alkali in the colouring solution. The addition of acids turns the colours of cloths dyed by annotta to a yellowish-red, so that by pass- ing a piece of cloth dyed orange through water, slightly acidulated, it assumes a scarlet cr salmon colour, according to the quantit}' of colouring matter used. But all the colours dyed by annotta are exceedingly fugitive, and although neither acids nor alkalis can completely remove the colours dyed by it, still they are constantly changing and fading by exposure to the air and hght. On this accoimt annotta is now very seldom used in the cotton dye-house, and then it is used only as an auxiliary. It is, however, still used for silks and wooUens, as the objections to its use for cotton do not apply so strongly in its relations to those substances. It may also be used with propriety for mixed fabrics, such as sUk and cotton, sUk and woollen, &c. Annotta was considered to contain two distinct colouring matters, a yellow and red, till it was shown by M. Preisser that the one is the oxide of the other, and that they may be obtained by adding a salt of lead to a solution of annotta, which pre- cipitates the colouring matter. The lead is separated by sul- phuretted hydrogen ; and the substance being filtered and evaporated, the colouring matter is deposited in small crystals of a yellow-white colour. These crystals consist of bixine :■ they become yellow by exposvu-e to the air, but by dissolving them in water this change is prevented. Sulphuric acid gives... A yellow, which does not turn blue as it does with annotta. Nitric acid A yellow shade. Chromic acid A deep-orange tint. ALKANET ROOT. 3G9 When ammonia is added to bixine with free contact of air, there is formed a fine deep-red colour, like annotta, and a new substance is produced, termed bixeine, which does not crystaUize, but may be obtained as a red powder ; this is coloured blue by sulphuric acid, and combines with alkalis, and is bixine with addition of oxygen. When annotta, in the form of paste, is mixed from time to time with stale urine for its improve- ment, it is more than probable that this improvement consists in the formation of bixeine from the bixine, by the ammonia of the urine. This is rendered the more probable by finding the interior of the annotta yellow, while the red colour is much more developed upon the surface where the air has free access to it. This naturally suggests the mixing of annotta with a little ammonia, and exposing it to the air as much as possible pre- vious to its being prepared for dyeing, as a much richer colour is thereby obtained. The adulterations of annotta are oxide of lead and ochre. These may be detected by burning a small quantity of it in a china crucible : if pure, no residue will be left; but if oxide of lead be the adulterant, by keeping the crucible at a red heat, a small button of lead will be obtained ; and if ochre be present, a red powder will be left. The liquid sold in shops under the name of Scott's nankeen dye, is a solution of annotta and potash in water. Annotta is often used for colouring butter and cheese. Ai.KANET Root. This is the root of a plant (Lithos permum tinctorium) which grows in the Levant and several other warm countries. It was introduced as a dye a few years ago, but with little success. The colouring matter is slightly soluble in water, but is rendered soluble by alkalis, to which it gives a blue colour, also by oils and fatty substances, which it colours red. It has the following reactions : — Salts of lead Blue precipitates. Salts of tin Crimson precipitates. Salts of iron Violet-colour precipitates. Salts of alumina Violet precipitates. H 2 370 ARCHIL. A variety of shades of lavender, lilac, violet, &c. are dyed by this colouring matter, but caution and experience are neces- sary to ensure success, and the colours obtained are easily affected by light — which, in our opinion, is the greatest barrier to its use. Colours formerly -were generally dyed with it by giving the cloth an oil or soap preparation, the soap being combined with alumuaa to serve as the base. Archil. This colouring matter is prepared from lichens, a species of sea-weed. The most esteemed is that denominated Lichen rocella. The best sort comes from the Canary and Cape de Verde islands ; but it is also found abundantly on the coast of Sweden, Scotland, Ireland, and Wales, and the people have from time immemorial used it for dyeing cloths. The colouring matters prepared from these lichens have been long known in commerce in the following forms : — 1st. As a pasty matter, called archil. 2d. A mass of a drier character, called persis ; and, 3d. As a red powder, called cudbear. The details of the mode of preparing archil have been kept a secret, and are but imperfectly known even yet. The fol- lowing is what is known: — The lichens are first ground between two stones to a pulp, with the addition of water, and afterwards put into a wooden trough, having a tightly- fitted cover ; upon the moist pulp is sprinkled a mixture of urine and ammonia, and the vessel being then covered, fermentation soon begins. The whole is occasionally stirred, and more ammonia and lu'ine are added from time to time. After a few days, the colour begins to develop itself, but about six weeks are required to complete the operation. The whole is then removed from the trovigh and placed in casks, and may be kept for years. The keeping is considered to im- prove the intensity of the colour, which should be of a deep reddish-violet. Acids change the colour to Bright red, and Alkalis to A blue. ARCHIL. 371 Sea-salt gives it A crimson tint. Salammoniac A ruby-red tint. Alum throws down A brownish-red precipitate. Salts of tin Red precipitates. Salts of iron Red-brown precipitates. Salts of copper Cherry-brown precipitates. There are no mordants required for dyeing with archil. It is not used for cotton dyeing, but extensively for silk and wool- len, imparting very beautiful tints, which, however, are not permanent. It is often used as a bottom colour for reds which are to be dyed by safflower, cochineal, &c. and gives depth and a beautiful rich tint to the colours so dyed. The colouring principle of these lichens, and especially that producing the archil, has been the subject of extensive inves- tigation with some of the first chemists both in this and other countries. The results of these researches are, that the colouring matter of these lichens depends upon the oxidation of a colourless base, or compound existing in the plant. That of archil is termed orceine, and the oxidized colour is known as orcine. Dr. Stenhouse has given very simple methods of obtaining these matters from the lichens. Could this colour be obtained of a permanent character, and fixed upon cotton, its value would be inestimable. PROPOSED NEW VEGETABLE DYES. There are occasionally papers, of great value to the dyer, appearing in periodicals and the reports of scientific societies, that ai-e not seen by practical men, and their value to a great extent is consequently lost. We have selected a few in proof of this statement, and trust it ■will stimulate to a more active research after such articles, which cannot fail to be productive of good results. SOORANJEE, This substance was investigated lately by Professor Ander- son, from whose paper we give the following account : — " The subject of these experiments was imported into Glas- gow, some time since, under the name of Sooranjee, with the intention of introducing it as a substitute for madder in the art of dyeing. For this purpose it was, on its arrival, sub- mitted for trial to some of the most experienced and skilful calico printers in Glasgow, all of whom concurred in declar- ing it not to be a dye at all, and to be totally destitute of useful applications. My friend. Professor Balfour, happening to hear of this circumstance, was so good as to obtain for me a quantity of the root, which has enabled me to submit it to a chemical investigation. " Sooranjee is the root of the plant, and is imported cut up into pieces from one to four inches in length, and varying in diameter from half down to nearly an eighth of an inch. On the small pieces the bark is thick, and forms a large propor- tion of the whole root, but on the larger fragments it is much thinner. Its external colour is pale grayish-brown; but when broken across, it presents colours varying from fine yel- low to brownish-red, and confined principally to the bark. The wood itself has only a slight yellowish shade, deepest in SOOKANJEE. 373 the centre, and scarcely apparent close to the bark ; but it is coloured dark red by alkalis, indicating the presence of a cer- tain quantity of colouring matter in it. The bark is readily detached, and its inner surface, as well as that of the wood, has a peculiar silvery appearance, most apparent on the large pieces and almost entirely absent in the smaller. Boiled with water, it gives a wine-yellow decoction, and with alcohol a deep-red tincture. " Solution of morindine gives with subacetate of lead a pre- cipitate depositing itself in ci'imson flocks, which is extremely unstable, and cannot be washed without losing colouring matter. With solutions of baryta, strontia, and lime, it gives bulky-red precipitates, sparingly soluble in water. Perchloride of iron produces a dark-brown colour, but no precipitate. When its ammoniacal solution is added to that of alum, the alumina precipitated carries down with it the morindine as a reddish-lake ; and when added to perchloride of iron, a brown precipitate is thrown down, which cannot be distinguished trom pure peroxide of iron, but which contains morindine, as the supernatant fluid is colourless. " The formula thus ascertained brings out an interesting relation between morindine and the colouring matters of mad- der, and more especially that one which is obtained by the sublimation of madder purple. From his analysis of this sub- stance, Schiel * deduces the formula C^ H4 O4. As this, how- ever, is no more than the simplest expression of the analytical results, and as all the other madder-colouring matters examined contained 28 equivs. of carbon, we are justified in supposing its real constitution to be represented by quadruple of that formula, or H28 Hjg O],,, which differs from that of morin- dine by a single equivalent of water only. The unsublimed madder purple is also connected, though more remotely, with morindine, and differs only by containing 5 equivs. of hydro- gen less, its formuhx according to Schiel being C28 Hjo 0^. "This similarity, however, does not extend itself to their properties, as dyes, in which respect they differ in a very remarkable manner. I have already mentioned that the calico printers had entirely failed in producing a coloiur by means of sooranjee ; and this I have fully confirmed as regards the common mordants. I digested morindine for a long time, " Chemical Gazette, vol. v. p. 77. 374 SOOKANJEE, in a gradually increasing heat, with small pieces of cloth mor- danted with alumina and iron ; but nothing attached itselJ', and the mordants, after boiling for a minute or two with soap, were found to be unchanged. Even with the root itself alum mordant only acquired a slight reddish -gray shade, and iron became scarcely appreciably darker in coloui". The case was different, however, when cloth mordanted for Turkey red was employed. I obtained from Glasgow pieces of calico prepared for Turkey red both by the old and new processes ; and I found that both acquired with morindine, in the course of a couple of hours, or even less, a dark brownish-red colour, devoid of beauty, but perfectly fixed. These observations agree with the account given by Mr. Hunter of the method of dyeing with the M. citrifolia employed by the Hindoos. The cloth is first soaked in an imperfect soap, made by mix- ing the oil of the Sesamum orientale with soda-ley. After rinsing and drying, it is treated with an infusion of myro- balans, (the astringent fruit of the Terminalia chehula,) and exposed for four or five days in the sun. It is then steeped in solution of alum, squeezed, and again exposed for fom* or five days. On the other hand the powdered roots of the Ilorinda are well rubbed with oil of sesamum, and mixed with the flowers of the Lythrum fmticosum (Eoxburgh) or a corresponding quantity of pu7-icas, (the nut-gall of a species of Mimosa.) The whole is introduced along with the cotton into a large quantity of water, and kept over a gentle fire for three hours, when the temperature is brought to the boiling point. The red colour so obtained is, according to Mr. Hunter, more prized for its durabihty than its beauty. This is simply a rude process of Turkey red dyeing. He also mentions that, by means of iron mordant, a lasting purple or chocolate is obtained ; but in this case the colour is probably affected by the tannine of the astringent matters employed in the process. " Morindine is a true colouring matter, and is capable of attaching itself to common mordants. It gives with alumina a deep rose-red, and with iron violet and black; but the colours are not very stable, and it has a strong tendency to attach itself to the unmordanted parts of the cloth and to degrade the white. jNIorindine, after treatment with sulphuric acid, is capable of attaching itself to ordinary mordants. " The discovery of a peculiar colouring matter capable of SOORANJEE. 375 fixing itself exclusively on Turkey red mox'dant, is of interest as establishing the existence of a peculiar class of dyes hitherto totally unsuspected, a class which may be extensive, and may yield important substances. It may serve also in some respects to clear up the rationale of the process of Tui'key red dyeing, which has long been a sort of opprobrium of chemistry. Although that process has been practised for a century in Europe, and has undergone a variety of improve- ments, no clear explanation of it was for a long time given ; but it was supposed that, by the action of the dung, of which large quantities are employed, the cloth underwent a species of animalisation, as it was called, by which it acquired the property of receiving a finer and more brilliant colour than could be attached to it by purely mineral mordants. Eecent experiments have, however, shown that the oil, which is largely employed in the process, undergoes decomposition by long exposure to the air in contact wdth decomposing animal matter, and is converted into a sort of resinous matter, which constitutes the real mordant for Turkey red. This has been pretty clearly made out by the experiments of Weissgerber.* He foimd that when cloth had been treated with oil, so as to give when dyed a fine rose-red colour, he could, by digestion with acetone, extract from it the altered oil ; and as it was removed the cloth gradually lost the power of attracting the colouring matter of madder, until, when it was entirely separated, the cloth passed through the dye without acquiring any colour. On the other hand, he found that, by applying the substance extracted by acetone in sufi3cient quantity to cloth, he could obtain the richest and deepest colours with madder, without the addition of any other substance whatso- ever. These observations receive additional confirmation from the experiments detailed in the present paper, as it must be sufficiently obvious that the dark-red colour obtained on Turkey red mordant with morindine must be entirely irre- spective of the alumina, on which that substance is incapable of fixing. " I fully agree with the opinion expressed by Persoz, that the use of alum mordant, which is at present always employed in Turkey red dyeing, will be entirely abandoned as soon as calico printers have learned the method of modifying at will * Persoz, sur I'lmpression des Tissus. vol. iii. p. 176. 376 CAKAJUItU OR CHICA. the oil whicli they employ, so as to bring it at once into the state in which it acts as a mordant. Some steps have been made in this direction by making use of some chemical agents, as nitric acid and chloride of lime, for the purpose of acting on the oil ; but the improvements which have been eflfected stop far short of what I believe will eventually be effected when the system of pure empiricism, which has been all along employed in this particular process of dyeing, is abandoned, and the subject submitted to really scientific investigation. It is understood that M. Chevreul has entered upon the inquiry, and in his hands there is little doubt but that it will meet with a satisfactory solution." — From the Transactions of the Boyal Society of Edinburgh. Carajcru or Chica Is a vegetable substance known by these names, and is obtained from America, where it is used by the natives as a dye. The following short extracts from a paper by J. J. Virey, will show its character and properties : — "AL de Humboldt has described in the 'Annales de Chemie et Physique,' (vol. xxvii. p. 315,) under the name of Chica, a vegetable product of a brick-red colour, obtained by macerating in water the leaves of Bignonia chica, a shrub of the family of the Bignoniacece from equinoctial America. " As we have obtained from Para in Brazil, under the denomination Crajuru or Carajurv, a substance not only analogous in its physical and chemical characters to the Chica, but of a red -brown violet tint, much more beautiful and rich, and like vermilion, whilst the otlier appeared duller and much inferior, it may be useful to give fresh details about this product, which has been imported to be tried in dyeing. "The Crajuru or Carajuru (Carucuru according to others) is a kind of powder or fecula, in pieces somewhat light, inodor- ous, insipid or slightly bitter, not soluble in water, but soluble in alcohol, ether, and the oils and fats, without being com- pletely resinous, burning with a flame, but leaving a quantity of gray cinders. It is wholly dissolved by alkalis, and acids precipitate it without greatly altering its colour, if they are not concentrated. WONGSHT. 377 '* The Crajuru now brought into Europe must furnisli a rather strong and beautiful dye, the brilliancy of which appears quite superior to that of Orleans." * WoNGsnY Is another vegetable substance. An investigation of its properties was made by W. Stein, from whose paper we ex- tract the following account : — " Towards the end of last year, a new material for dyeing yellow, called tuongshy, was exported on experiment from Batavia to Hamburg, for a sample of which I am indebted to the kindness of M. Yollsack, merchant. Whether it has hitherto been applied as a dyeing material, and with what results, could not be ascertained. The following notice, there- fore, will probably not be without interest : — " The new dyeing material consists of the seed-vessels of a plant, which, according to the information from M. Keichen- bach, belongs to the family of the Gentianea). The form ot the unilocular capsules is longish-ovate, drawn out to a point next the end of the peduncle, and crowned upon the opposite and more obtuse one with the dried six-lobed calyx. They vary in size ; but on an average their length is 1 "5 to 2 inches, and the diameter at the thickest part 0"5 ; the colour is not uniformly reddish-yellow, but at some places darker, at others lighter. The surface is more or less irregularly waved with six to eight longitudinal ribs. The odour re- sembles saffron, and subsequently honey. The shell is pretty hard and brittle, but becomes quickly mucilaginous when chewed, imparting a yellow colour to the saliva, with a sHghtly bitter taste ; it swells up considerably in water. In- side the capsules there are a number of dark reddish-yellow seeds (in one specimen I counted 108) ; they are not attached • " The drink called chica, which is so much used among the people of South America, must not be confouuded with the subject of the present notice. This drink, in fact, is prepared with pods of algaroba, (^Mimosa altjaroba,) which are nearly as sweet as the carouba of the Ceratonia Siliqua, and ^^•ith the bitter stalks of the Schinus molle. It is said that old women are employed to chew these Ahjaroha; and the Schimis, and then to spit them into a vessel ; water is added ; the whole soon ferments, and affords a kind of intoxicatins; beer." 378 WONGSHY. to the sides, but are imbedded in a hardened pulp, and so connected one with the other. These seeds are tolerably hard, soften but slowly when chewed, have no particular taste, but after some time produce at the point of the tongue a slight but pecuhar sourish-sweet pungency, resembling the action of Paraguay rue. The pulp, on the other hand, cementing them together has a strong bitter taste, which is particularly perceptible at the back part of the palate. '•The wongshy, especially when pounded, readily gives up to water, both at the usual temperature as well as on boihng, a colouring principle which possesses such an enormous divi- sibility, that two parts of the pounded capsules furnish 128 parts of a liquid, which, placed in a cyhndrical vessel of white glass ■ft'ith a diameter of three inches, still appears of a bright w,ine-yellow colour. The concentrated extract is very muci- laginous, and has a fiery-red colour, which, on large dilution, passes into a golden-yeUow, the red disappearing. " Protochloride of tin produces no change at the ordinary temperature, or after a long time ; on boiling, a dark orange- coloured precipitate results. " Acetate of lead produces no change. " Basic acetate of lead causes a turbidness at the ordinary temperature, and an orange-coloured precipitate on boUing. " Protosulphate of iron changes the colour into a dark brownish-yellow, without, however, a precipitate resulting either in the cold or on ebullition. '* Alum, acetate of alumina, and acetate of zinc, produce yellow precipitates only on boiling. " Barytic water causes a yellow precipitate at the ordinary temperature, which on boihng acquires a reddish tint. " Lime-water gave a pure yellow precipitate ; solutions of gypsum and chloride of calcium are not precipitated by it even on boiling ; well water, with a considerable amount of carbonate of lime, does not precipitate the colom-ing principle even -svith the assistance of heat ; it is consequently not able to decompose the combinations of lime with acids. " To ascertain the value of the wongshy colouring matter for the purposes of dyeing, ] part of the pounded capsules was digested for twelve hours with 20 parts of lukewarm water, being frequently stirred, and the hquid then strained. The colouring matter is most quickly extracted in this manner WONGSHY. 3 79 without its becoming gelatinous from the formation of paste, as would happen were the liquid boiled. Properly prepared samples of woollen cloth, some without any mordant, others mordanted with alum, protochloride of tin, acetate of alumina, and basic acetate of lead, were dyed with this extract at a temperature of about lO-i" Fah. ; the colour does not turn out so pure at a higher temperature. The unmordanted cloth was dyed a beautiftil and uniform orange colour by one im- mersion ; of the mordanted samples, those with alum and acetate of alumina were better than those wath protochloride of tin ; the least satisfactory was that in which basic acetate of lead had been used as mordant. The tone of the colour was uot altered by the three first mordants, but it was less intense, and the stuffs were not uniformly penetrated by the colouring matter. However, the samples with alum mordant gave perfectly satisfactoiy results after a second immersion. The colouring matter likewise combines readily and uniformly with silk, communicating to it a very glowing golden colour, so that in this case I also prefer not having recourse to mor- dants. Cotton, as was to be expected, can only be dyed with the assistance of mordants, and the best results appeared to be obtained with tin mordants ; the colour was orange, of a very agreeable tint. " The colour, both upon wool, silk, and cotton, resists soap perfectly ; but alkalis give it a yellow, acids and tin salt a red tint. By this behaiaour it differs from the colour of annotta, with ^Yhich, as will subsequently be seen, it possesses in other respects great resemblance, a resemblance which un- fortunately exists as regards the action of light. When exposed to light, the colour very soon fades upon cotton, less quickly upon wool ; and in this case it is more permanent upon the unmordanted samples. It resists the light longest upon silk ; and, in this respect, when compared with the other known yellow colours, may be reckoned among the best. " I obtained a beautiful yellow, with a faint tint of red, by mordanting the Avoollen cloth with lime-water, and immersion in the boiling vat ; it resists the soap perfectly, and the action of light much better than the orange. It is altered in a similar manner to the orange by alkalis, acids, and tin salt, only less. Several very beautiftil diades of yellow may be obtained by 380 WONGSHY. adding pearlash or caustic potash to the dye, and immersing the unraordanted fabric at the ordinary temperature. The union of the colour with the fibre takes place very quickly and very uniformly. By the addition of 1 part pearlash to 30 parts dye Hquor, a yellow was obtained with a remarkable glow from a slight admixture of red. By the addition of twice the quantity of pearlash, a lively yellow, with a faint tint of green, was obtained. A still larger amount of peai'lash cannot be used, as it renders the colour dull and impure. With caustic potash, instead of pearlash, I obtained, in the first place, a pure brilliant yellow, with less red than with the pearlash ; in the latter case, a beautiful canary-yellow with a shade of green. Ammonia acts in the same manner, but the colour, under all circumstances, contains more red. The colour also appears of a somewhat different shade Avhen the fabrics are first immersed in the dye liquor, and then, after being washed, placed in an alkaline bath. " In the case of silk and cotton, the effect of alkalis is simi- lar, but less apparent, because the silk and cotton fibres im- bibe less of the colouring substance than those of wool. " That this colour resists the soap is self-evident, but it also suffers less from the action of light than the orange ; and when fabrics so dyed are passed through a vinegar or muriatic acid bath, a brilliant aurora colour is obtained. This interesting behaviour, which the wongshy colouring matter has in com- mon with that of annotta, is explained by the chemical character of the former, which is a weak acid ; it combines with the alkalis and with the alkaline earths, as evident by the pre- cipitation with baryta and lime-water. Its combinations with the former possess a pure yellow coloiir, and are decomposed by stronger acids, when the hberated colouring matter sepa- rates of a brilliant vermiUon colour. But the colouring matter thus separated is no longer the same as that which was originally contained in the aqueous solution, for it is now perfectly insoluble in water, and is only dissolved in small quantity, and of a golden-yellow colour, by absolute alcohol, ether, and spirit of 0'863 spec, grav. In the moist state it has a vermilion colour ; when dry and in the purest state, it is brown-red, like Ratanhia extract, and is easily reduced to powder ; but if it stiU contains sugar and fat, it has a beauti- ful yellowish-red colour, in thick layers, whilst in thin layers ALOES. 381 it is yellow and transparent, and becomes moist in the air. On beating the pure substance upon platinum, at first yellow vapour is given off, and at some spots the colour becomes pure yellow ; it subsequently turns black, fuses, and chars. The residual cinder is difficult to burn ; the yellow vapours condense, when the experiment is made in a glass tube, into yellow oily drops. Concentrated sulphuric acid renders it scarcely perceptibly blue, and the acid acquires the same colour, which quickly passes into violet and brownish-red, whilst the colouring matter slowly dissolves. Water sepa- rates from this solution a dirty yellowish-gray flocculent sub- stance. " The reaction of the wongshy colouring matter which has just been mentioned, has no resemblance with the reaction of sulphuric acid upon annatto, for the hquid never acquires a pure blue colour, as is the case with annatto, but is violet from the first, and only for a minute. " It dissolves readily in caustic ammonia and caustic soda, with a golden-yellow colour." Aloes. Dr. Bancroft in his work on the Philosophy of Per- manent Colours, recommended this substance as a dyeing agent. He proposed to digest it in nitric acid, by which means he obtained aloetic acid, a substance capable of being used as a dye. This matter has been the subject of extensive investigation by many chemists, and has been occasionally more or less used as a dyeing agent. A patent, however, has recently been taken out for certain applications of aloes to dyeing. The following is the proposed method of prepara- tion : — " The mode of preparing the colouring matter from aloes is as follows : — Into a boiler or vessel, capable of holding about 100 gallons, the patentee puts 10 gallons of water, and 132 lbs. of aloes, and heats the same until the aloes are dissolved ; he then adds 80 lbs. of nitric or nitrous acid, in small portions at a time, to prevent the disengagement of such a quantity of nitrous gas as would throw part of the contents out of the boiler. When the whole of the acid has been introduced, 382 PITTACAL. and the disengagement of gas has ceased, 1 lbs. of liquid caustic soda, or potash of commerce, of about 30° are added, to neutrahze any undecomposed acid remaining in the mix- ture, and to facihtate the vise of the mixture in dyeing and printing. If the colouring matter is required to be in a dry state, the mixtiure may be incorporated with 100 lbs. of China clay, and dried in stoves, or by means of a current of air. In preparing the colouring matter from extract of logwood, the materials are used in the manner and proportions above de- scribed ; the only difference being, that the extract of logwood is substituted for the aloes. •'The colouring matter is used in dyeing by dissolving a sufficient quantity in water, according to the shade required, and adding as much hydrochloric acid or tartar of commerce as will neutrahze the altali contained in the mixture, and leave the dye-bath slightly acidulated. The article to be dyed is introduced into the bath, which is kept,(boiling until the de- sired shade is obtained. '' When the colouring matter is to be used in printing, a sufficient quantity is to be dissolved in water, according to the shade requii'ed to be produced ; this solution is to be thickened with gum, or other common thickening agent ; and hydro- chloric acid, or tartar of commerce, or any other suitable supersalt is to be added thereto, for the purpose before men- tioned. After the fabrics have been printed with the colo'ur- ing matter, they should be subjected to the ordinary process of steaming, to fix the colour." — Sealed Jan. 27, 1847. is ppt i. ' PiTTACAL. This substance is pptained from beech tar. It is dry and hard, very brittle, andVesembles indigo in appearance. It has no taste or smell, and does not dissolve in water. Sulphuric acid dissolves it, producing a violet- coloured solution. Muriatic acid gives a red-purple solution, from which alkalis precipitate the pittacal. Acetate of lead, salts of tin, sulphate of copper, acetate of alumina, all give deep-blue precipitates, not readily changed. This colour is fixed easily upon cotton by tin and alumina.* * Records of Ueneral Science. 383 Barbary Root. The plant from which this is obtained grows in almost eA-ery part of the world ; great quantities of it are obtained from India, where it grows in great abundance and per- fection. The colouring matter is found in the whole of the root. In the stem it is found round the pith and near the bark. This colouring substance is much used in dyeing or staining leather; but it is not much used in dyeing of cotton. Mr. Edward Solly has made some investigations of this root. See Journal of the Royal Asiatic Society. ANIMAL MATTERS USED IN DYEING. The colouring substances remaining to be noticed belong to the animal kingdom. They are but few in number, and none of them as yet made suitable for dyeing on cotton. Cochineal. This is a small insect called the coccus cacti, and is much sought after for its tinctorial qualities. It furnishes the finest known shades of crimson, red, purple, scarlet, &c. for woollen and silk. The insects are reared in great abundance in Mexico. They feed upon a cactus plant, which the natives cultivate round their dwellings for that purpose. The insects attach themselves to the leaves of the plant, and increase rapidly in number. The females live about two months, and the males only about one month. The season of rearing and gathering lasts about seven months : during this period the insects are gathered three times. After each gathering some of the branches and leaves containing females and their young, are preserved under shelter, and on the return of the proper season they are distributed over the plantation. A few females are put into a small nest made of some downy substance, and the young insects quickly spread themselves out upon the leaves, to which they attach themselves. They are gathered by brushing them off the leaves with the feather end of a quill into boiling hot water, in which they are kept a few seconds. This not only kills them instantly, but causes them to swell to twice their natural size. When taken out the hot water, they are spread out and dried, and then packed for the market. Some cultivators instead of hot water use steam, and others again place them in an oven or upon a hot plate. The difference in the appearance of the cochineal, is caused by these different modes of killing the insects and CAR3I1NE. 385 heating them. They shrivel ia drying, and assume the appearance of irregular formed grains, fluted and concave. The best sort seem as if dusted with a white powder, and are of a slate-gray colour ; but these appearances are often imparted by means of powdered talc, to deceive the purchaser. There are three kinds of cochineal in commerce. The finest is known by the name of mistic^ from the name of the place in which the insects are reared. La Mistica, in the province of Honduras. Another is called wild, because they are col- lected from plants growing in a state of nature; but this variety is inferior to the former. The third is a mixture of these two, or rather the debris or fragments, and varies in quality according to the proportion of the mixture. Cochineal has been the subject of several chemical investi- gations, the results of which are not very satisfactory. The following are instances of these. The cochineal contains — 1. Carmine, which may be termed the colouring matter. 2. A peculiar animal matter. 3. A fatty matter, composed (1^,^?^^°^' , of .... . 1 ^^6111^5 aiid t Volatile fatty acids, f Phosphate of lime, j Carbonate of hme. 4. Saline matters, as \ CJiloride potassium. } Phosphate of potash. I Combination of potash (^ with organic acids. Mr. John gives the following as the result of his analysis:— Red-colouring matter 50-0 Gelatine 20*5 Wax '.'.*.'.*.".".'."."!.'.'.".".".'.'.'." 100 Debris of skin, &c 14-0 Gummy matter 13-0 Phosphate of hme, of potash, and iron, and) ^. ^ chloride potassium | ^^'^ Carmine, or the colouring matter of cochineal, may be °^^fi^ed by macerating finely ground cochineal with ether, which dissolves out the fatty matter, and then dissolving the s 386 COCHINtAL. carmine by the application of hot alcohol, and leaving the solution to cool : by evaporating, the carmine is deposited as a beautifiil red crystalline substance, which dissolves freely in water. It is affected by the following re-agents as under : — Tannin Gives no precipitate. Most acids Change its colour from a bright to a yeUowish-red. Boracic acid Does not change the colour, but rather reddens it more. Potash, soda, and ammonia Change it to a crimson- violet. Baryta and strontia Produce the same effect. Lime Gives a crimson-violet pre- cipitate. Alumina.... Combines with it and pre- cipitates it as a beautiful red ; but if boiled it passes to violet-red. A little potash, soda, or am- monia added prevents this change, and preserves the stability of the red. Protoxides of tin Change it to crimson- violet. Peroxide of tin Changes it to yellowish-red. Salts of iron Turn it brown; no precipi- tate. Salts of lead Change it to violet ; no pre- cipitate. Salts of copper Change it to violet; no pre- cipitate. Nitrate of mercury Gives a scarlet-red precipi- tate. Nitrate of silver Has no action upon it. Chlorine Turns it yellow, "As may be supposed, the result of all these contrary opinions is, that it is perfectly impossible to judge of the goodness of a cochineal by its physical charact^^^-rin order to ascertain its value, we must have recourse to comparative experiments. We are indebted to I^IM. Kobiquet and Anthon for two methods of determining the quality of cochineals, according to METHOD OF TESTING. 387 the quantity of carmine they contain. The process of M. Robi- quet consists in decolourizing equal volumes of decoction of dif- ferent cochineals by chlorine. By using a graduated tube, the quality of the cochineal is judged of by the quantity of chlorine employed for decolourizing the decoction. The process of M. Anthon is founded on the property which the hydrate of alumina possesses of precipitating the carmine from the de- coction so as to decolourize it entirely. The first process, which is very good in the hands of a skilful chemist, does not appear to us to be a convenient method for the consumer : in the first place, it is difficult to procure perfectly identical solutions ; in the next place, it is impossible to keep them a long time without alteration. "We know that chlorine dis- solved in water reacts, even in diffused fight, on this liquid, decomposes it, appropriates its elements, and gives rise to some compounds which possess an action quite different from that of the chlorine solution in its primitive state. The second process seems to us to be preferable, as the proof Uquor may be kept a long while without alteration. A gra- duated tube is also used ; each division represents one-hun- dredth of the colouring matter. Thus, the quantity of proof liquor added exactly represents the quantity in hundredths of colouring matter contained in the decoction of cochineal which has been submitted to examination. " The colouring matter of cochineal being soluble in water, I have used this solvent for exhausting the different kinds which I have submitted to examination in the colourimeter. I operated in the following manner: — I took a grain of each of the cochineals to be tried, dried at 122° Fah.; I submitted them five consecutive times to the action of 200 grains of dis- tilled water at water-bath heat, each time for an hour ; for every 200 grains of distUled water I added two drops of a concentrated solution of acid sulphate of alumina and of pot- ash. This addition is necessary to obtain the decoctions of the different cochineals exactly of the same tint in order to be able to compare the intensity of the tints in the colouri- meter.* * Care must be taken not to add to the water, which serves to extract the colouring matter from the diflerent cochineals, more than the requisite quantity of acid sulphate of alumina and solution of potash, because a stronger dose would precipitate a part of the colouring matter in the state of lake. 38^ COCHINEAL. " In order to estimate a cocliineal in the colourimeter, two solutions obtained, as described above, are taken ; some of these solutions are introduced into the colourimetric tubes aa far as zero of the scale, which is equivalent to 100 parts of the superior scale; these tubes are placed in the box, and the tint of the liquids enclosed is compared by looking at the two tubes through the eye-hole, the box being placed so that the light falls exactly on the extremity where the tubes are. If a difference of tint is observed between the two hquors, water is added to the darkest (which is always that of the cochineal taken as type) until the tubes appear of the same tint.* The number of parts of Hquor which are contained in the tube to which water has been added is then read off; this number, compared -with the volume of the Hquor contained in the other tube, a volume which has not been changed, and is equal to 100, indicates the relation between the colouring power and the relative quahty of the two cochineals. And if, for example, 60 parts of water must be added to the hquor of good cochineal, to bring it to the same tint as the other, the relation of volume of the liquids contained in the tubes will be in this case as 160 is to 100, and the relative quahty of the cochineals will be represented by the same relation, since the quahty of the samples tried is in proportion to their colouring power." Some of the German chemists, supposing that the plant upon wliich the insect feeds, might be the source of the colouring matter, instituted a series of experiments to determine that point, but without success. The conclusions they came to are, that the animal economy plays a prominent part in the formation of the colouring matter. Carmine is manufactured extensively in France, and is used for superior red inks, paints, and for colouruig artificial flowers. It is prepared on the large scale by boiling a quan- tity of cochineal in water with soda, and then adding to it a little alum, cream of tartar, and the white of eggs, or ismglass — which separates the carmine as a fine flaky precipitate. This precipitate is carefully collected. * For diluting the liquors the same water must always be used which has served to extract the colouring matter of the cochineals under examination, otherwise the darkest decoction would pass into violet as water was added to it to bring back the tint to the same degree of intensity as that of the decoction to which it is compared. LAKE LAKE, OR LAC. i 389 There is sometliing in the production of good carmine which is not yet fully understood. It has not yet been prepared in this country in the same perfection as in France, (page 16.) It is found also, that, with a coal fire, a smaller quantity of it is produced than when a wood fire is employed ; and there are many other little points which show the delicacy of its preparation. The residue of the carmine, and some portions of the pre- cipitate from the cochineal, when first taken from the fire, are collected and boiled in water ; to this mixture is added a solution of alum and chloride of tin, by which a beautiful red-coloured precipitate or lake is formed. This constitutes the beautiful pigment known as carmine lake. Lake Lake, or Lac, Is a concrete juice which distils from several kinds of plants. It appears, however, to be determined that it is caused by an insect named coccus Jicus, or caucus loco, and may there- fore be regarded as of animal origin. There are several varieties of this product under the names of stick lac, seed lac, and sltell lac. There is also brought from India two other products distingviished as lac lac and lac dye — which are the kinds mostly used in dyeing, but their composition is not very well known. They, however, contain a goodly quantity of resinous matter, which must be destroyed before they are put to use as a dye. Lac lac is obtained fit to use as a dye by boiling the gum lac with alkaUne water, which dissolves the colouring matter along with some of the resinous. To this is added some alum, which precipitates the whole as an alu- minous product, in which state it is used. Dr. Bancroil discovered that acids destroyed the resinous matter of lac dye, and rendered the colouring matter soluble, and this is the mode generally adopted in working with this substance. The following may.be taken as the ordinary means of pro- ducing this colour : — Add to four pounds of lac dye, three pounds of strong sulphuric acid, and set the mixture aside for two days ; pour over it half-a-gallon of boihng water ; stir the whole well, and leave it to settle for twenty-four hours ; the 390 KEMIS. clear liquor is then to be decanted into a leaden vessel, and the residue washed with water until all the colouring matter is dissolved. The washings may be added to the liquor in the leaden vessel. There is then added to this liquor a quantity of lime-water, until the solution barely tastes acid, which pre- cipitates the sulphuric acid ; the whole is then thrown upon a filter, and the cleai' liquor passing through the filter forms the dye. Some dyers take about 32 parts of lac dye, and rub it down fine in 10 parts of strong sulphuric acid ; then add three times the quantity of the mixture of water, and set aside for two days; it is then ready for use, requiring merely to be diluted as required. The French dyers generally take 32 parts of lac dye, rubbed down in 1 2 parts of hydrochloric acid of 30° Twaddell ; when well mixed, it is diluted with about an equal quantity of water, set aside for twenty-four hours, and stirred from time to time ; it is then ready for use. Many dyers treat the lac lac in the same way as the lac dye, using one pound of sulphuric acid to two pounds of lac lac ; in other respects the process is the same. The mordants employed for dyeing with the lacs are termed lac spirits; the lac and spirits are mixed previous to using. Lacs are employed as substitutes for cochineal, and most of the colours obtained by the one are producible by the other ; but for fine reds the lac is much inferior. This dye is only used for silk and woollen. Kekms. This is also an animal substance — the dried bodies of another species of the coccus insect. This insect is sup- posed to have been known as a dye so early as the time of j\Ioses ; it was used in India at a very early age, and was highly valued both by the Romans and Spaniards for dyeing purples ; but after the cochineal dye was discovered, it was used in preference, on account of the superior beauty of the colours. Accordingly, in many coimtries where the kerms insect was reared and enriched the people, the remembrance of it is lost. KERMS. 391 Good kerms is of a fall deep-red colour, having a pleasant smell, and sharp sour taste ; the red-colouring matter is soluble in water and in alcohol. It possesses properties similar to cochineal. Acids render it YeUo wish-brown. Alkalis Crimson- violet. Iron salts turn it Black. Alum renders it Blood-red. Salts of tin A bright red. A mixture of iron Siilts and tartar 'i r« i ■ ^ ^ > Gray colour, turns It to J ■' Sulphate of copper and tartar OUve-green. Tin salts and tartar Cinnamon -brown. For a red with tin it requires about 12 times the quantity of kerms as of cochineal, and the colour is a Uttle inferior. As a dye, it is not much used, and only for silk or woollen. There is no affinity between cotton and the colouring matters of cochineal, lacs, and kerms. D. H. HILL LFBRARY North Carolina State College 'GLOSSARY OF TECHNICAL TERMS' USED IN THE DYE-HOUSE WITH THE CHEMICAL. NAMES: A FULL EXPLANATION OF WHICH MAY BE OBTAINED IN THE VOLUME. Adjective. A term applied to a colour depending on a base for its pro- duction. Aqua-fortis. Nitric acid. Aqua-regia. A mixture of hydrochloric and nitric acids, generally in the proportion of 2 of the former to 1 of tlie latter. Alkali root. Alkanet root. Alterant. A substance added to a colour to give it brightness, same as " raising." Argol. Bitartrate of potash, formed by deposite on wine casks. Arnotto. Anuotta. Barilla. The name of an impure soda imported from Spain and the Levant. Black ash. Carbonate of potash in fused masses, as imported. Black lead. Carburet of iron. Black iron liquor. Acetate of iron, or pyrolignite of iron. Bleed. To extract the colouring matter from a dye drug. Bleaching powder. Chloride of lime. Block tin. Commercial tin cast into ingots or blocks, not so pure sis grain tin. Borax. Borate of soda. Bhie copperas. Sulphate of copper. Blue-stone. Sulphate of copper. Blue vitriol. Sulphate of copper. Bottom. Applied to the base of a colour such as sumach, galli*, &c. Brimstone. Sulphur. Brown sugar. Acetate of lead, or pyrolignite of lead. s2 394 GLOSSARY. Bucking. Boiling goods in alkalis. Bundle. Ten pounds of cotton yarn. Calomel. Protochloride of mercury. Carmine. Colouring matter of cochineal, extracted and dried. Chamher ley. Urine. Ckemic, or cliemic blue. Sulphate of indigo. Chrome. Bichromate of potash. Common salt. Chloride of sodium. Copperas. Protosulphate of iron. Corrosive sublimate. Bichloride of mercury. Cream of tartar. Bitartrate of potash, purified. See Axgoi. Crofting. Exposing goods upon the grass for bleaching. Crude tartar. See argol. Dip. Generally applied to immersing goods in the blue vat. Doctored. To adulterate, generally applied to giving an appearance of strong colom- to dyewoods, by adding water to them. Double muriate of tin. Bichloride of tin. Epsom salts. Sulphate of magnesia. Essential salt of lemons. Binoxalate of potash. Extract of indigo. Sulphate of indigo. Fast colour. Permanent colour. Fancy colour. Colours subject to fade, fugitive. Feathering. To granulate a metal. Firing spirits. Wlien tin by dissolving too rapidly or by heat, becomes converted into a bichloride. Fluery of a vat. The froth of oxidized indigo floating on the surface of a blue vat. Floivers of zinc. Oxide of zinc. French tub. Protochloride of tin and logwood, plumb tub. Glauber salts. Sulphate of soda. Grain tin. Metallic tin in prismatic pieces. Green vitriol. Sulphate of iron, copperas. Hartshorn. Ammonia. Kelp, Ashes left on burning sea weed. Killing. Dissolving any substance in an acid, as iron in nitric acid, killing iron. King's yellow, Sulphuret of arsenic. Lactine, A curd of milk used for animalizing cotton. Lemon juice. Citric acid. Ley. Solution of an alkali, as potash or soda. Lime shell. Caustic lime. Lime stone. Carbonate of lime. Litharge. Protoxide of lead. lAinar caustic. Nitrate of silver. Magnesia nigra. Manganese. Marine acid. Hydrochloric acid. GLOSSARY. 395 Mineral alkali. Soda. Mordant. Generally applied only to acetate of alumina. Muriatic acid. Hydrochloric acid. Muriates. Chlorides. Nitromuriate of tin. A solution of tin in nitric and hydrochloric acids, forming a persalt. Nitre. Nitrate of potash. Oxymiiriate of tin. Perchloride of tin. Oxymuriate of potash. Chlorate of potash. Oxymnriatic acid. Chlorine. Oil of vitriol. Sulphuric acid. Orpiinent. Sulphuret of arsenic. Oxygen of the bleachers. Chlorine, chloride of lime, bleaching powder. Pearlash. Carbonate of potash. Permuriate of tin. Perchloride of tin. Prussiate of potash, Ferrocyanide of potassium. Queen-wood. Brazil-wood. Quicksilver. Mercury. Raising. See alterant. Realgar. Sulphuret of arsenic. Red chrome. Bichromate of potash. Red liquor. Acetate of alumina. Rot steep. Steeping cloth in old leys to soften the paste, fermentation takes place, hence the name. Roman vitriol. Sulphate of copper. Saddening. Making a colour darker by means of a salt of iron. Salammoniac. Chloride of ammonium. Sali nixon. Bisulphate of potash. Sal prunella. Fused nitrate of potash cast into balls, or cakes. Sal volatile. Sesquicarbonate of ammonia. Salt of lemons. Citric acid. Salt of Saturn. Acetate of lead. Salt of soda. Carbonate of soda. Salt of sorrel. Binoxalate of potash. Salt of tartar. Carbonate of potash. Salt of vitriol. Sulphate of zinc. Salt perlate. Phosphate of soda. Saltpetre. Nitrate of potash. Salt sedative. Boracic acid. Salts of tin. Crystallized protochloride of tin. Salt cake. Sulphate of soda. Saxon blue. Sulphate of indigo. Scalding. Extracting a colouring matter by boiling water. Smalt blue. Gromid glass, made of alumina, silica, potash, or soda, coloured blue by oxide of cobalt. Slaked lime. Hydrate of lime. 396 GLOSSAEY. Sludge- Sediment of the blue vat. Single muriate of tin. Protochloride of tin. Sour. Water made acid by sulphuric acid. Soda ash. Carbonate of soda. Spirits. Solutions of chlorides of tin. Spirits of salt. Hydrochloric acid. Spirits of hartshorn. Ammonia. Spirits of wine. Alcohol. Spent. Exhausted of colour. Stoveing. Hanging goods in the stove to dry. Stock tub. Vessel filled vnth strong solution of a substance to be kept for use. Sugar of lead. Acetate of lead. Substantive colour. A colour fixed in the fibre without base or com- pound. Supertartrate of potash. See argol. Sweeten. To pour water upon goods, from a sour, as a partial wash. Tartar. See argol. Test blue. Sulphate of indigo. Tincal. Borate of soda, borax. TurnbulVs blue. Ferrocyanide of iron, Prussian blue. Vegetable alkali. Potash. Verdigris. Acetate of copper. Verditer. Acetate of copper. Vinegar. Acetic acid. Vitriol. Sulphuric acid. Volatile alkali. Ammonia. White vitriol. Sulphate of zinc. White copperas. Sulphate of zinc. White lead. Carbonate of lead. Whiting. Carbonate of lime.] White zinc. Oxide of zinc. INDEX. Acetate of alumina, 140 as a mordant, 144, 233 testing of, 144 of barytes, 133 of chromium, 191 of copper, 171, 234 of iron, 158 of iron and alumina, 233 of lead, 173 Acetj'Ie, 291 Acid, acetic, 243 antimonious, 206 antimonic, 206 arsenious, 202 arsenic, 203 boracic, 102 carbonic, 104 chloric, 61 chlorous, 61 chromic, 191 citric, 243 gallic, 243, 249 hydrochloric, 62 hypochlorous, 60 hyperchloric, 62 hyposulphuric, 96 hyposulphurous, 95 hydrofluosilicic, 101 isatinic, 296 molybdic, 200 nitnc, 62 nitrous, 51 osmic, 216 oxalic, 105 p\Toligneous, 143 picric, 293, 296 prussic, 33 sulphurous, 88 bleacliing by, 87, 89 sulphuric, 90 sulphuric fuming, 92 action of, upon indigo, 297 sulpho-indilic, 297 Acid, sulpho-purpuric, 297 tannic, 243, 249 tartaric, 243 telluric, 201 tcllurous, 201 valerianic, 296 Acids of bromine, 101 of iodine, 100 of phosphorus, 99 Adjective colours, 225 Aflinitv, table of, 28 law of, 29 application of the law of, 29 regulated by circumstances, 30 Alcase, madder, 354 Alcohol, 242 Aldehyde, 291 Alkalis carried off by steam in boil- ing, 6 Alkalimetry, 123 Alkaline leys in bleaching, 71 Alkanet root, 369 action of salts, &c. upon, :-t(j9 Alizarin, 357 action of salts, &c. upon, 358 Aloes as a dye, 381 Alterants, 221 Alum, 136 solubility of, 139 as a mordant, 139 Alumina, 136 acetate of, 140 qualities of, as a mordant, 144. 233 pyroUgnite of, 233 Aluminous salts and their reactions, 147 Amber colour dyed, 195 Ammonia, 58 Analysis of water, 52 Animalizing cotton for dyeing, 227 Antidote for arsenic, 202 Anyle, 291 398 INDEX. Annotta, 365 chemical constitution of, 367 action of acids upon, 368 how prepared for dyeing, 367 adulterations of, 369 Antimony, 204 salts' of, 205 Aqua-fortis, 58 Archil, 370 action of salts upon, 370 Arsenic, 202 a test for bleaching powder, 75 sulphurets of, 204 Arseniate and arsenite of copper, 171 Astringent matters as mordants, 226 Atmosphere, composition of, 49 Avignon madder, 355 Barbary root, 383 Barium, 133 chloride of, 133 Bark, 341 yellows, effects of heat upon, 8 Barwood, 335 how to test, 338 spirits, 186, 231 Barytes, nitrate of, 133 acetate of, 1 33 Basic salts, 27 Bees' wax, 242 Bengal indigo, 287 catechu, 265 Benzule, 291 BerthoUet's theory of the manufac- ture of indigo, 273 theory of bleaching, 69 Berj'llium, 135 Bichlorasatin, 296 Bichromate of potash, 192 Binoxide of hydrogen, a bleaching agent, 48 Birch, as a dye, 268 Bismuth, 177 its melting point, 2 salts of, 177 Bisulphate of potash, 114 Bisulphuret of hydrogen, 98 Bixa orellana, from annotta, 366 Bixeine, colouring matter of annotta, 369 Black ash, 110 iron liquor, testing of, 158, 233 Bleaching, facilitated by light, 1 chlorine as an agent in, 67 sketch of processes, 68 Bleaching, theories of croft, 69 modem process of, 71 theories of modern process of, 85 Bleaching-powder,mode of testing, 73 solutions, testing the strength of, 81 Blue, Prussian, how dved, 117 royal, 118 stone, 170 vat, copperas best suited for, 155 vitriol, 170 vat, the, 301 how prepared, 306 theory of the, 302 swimming of the, 304 BoU water, quantity of steam required to, 7 Boiling of liquids, 2 of leys, alkalis carried off in, 6 Boiling pbint,circumstances affecting, 6 Boiling point of potash solutions, 112 Borate of soda, 128 Borax, 102 Boron, and its compounds, 102 Brazil-wood, 331 action of salts upon, 333 how tested, 332 BraziUn, 333 Bromine, and salts of, 100 Broom as a dye, 268 Browns, manganese, 150 Cadmium, and its salts, 167 Calcium, 134 Cameleon, mineral, 150 Campeachy logwood, 321 Camwood, 338 Caoutchouc, 242 Carajuru, a new dye, 376 Carbon, 102 property of absorbing gases, 103 ditto, colours, 103 compounds with oxygen, 104 Carbonate of iron, 158 of lead, 173 of lime, 135 of nickel, 165 Carbonic acid, 104 Carmine, 16, 385 Carthamine, from safflower. 348 Carthamus, 347 Caseine, for animalizing cotton, 228 Cast iron, its melting point, 2 Catalysis, definition of, 30 INDEX. 399 Catechu, 263 effects of reactions upon, 264 analyses of, 265 Centigrade thermometer, 4 Cerium, and its salts, 207 Cerulin, 296 Charcoal, different kinds of, 103 Chemic, a name given to bleachin powder, 72 blue, 222, 300 Chevreul on pastel, indigo, &c. 309 Chica, a new dye, 376 Chloranile, 290 Chlorate of potash, 114 Chloric acid and chlorates, 61 Chloride of calcium, 74, 135 of chromium, 190 of copper, 170 of gold, 212 of iron, 157 of lead, 176 of nickel, 165 of nitrogen, 66 of platmum, 213 of sodium, 128 of tin, 180 of zinc, 166 Chlorides, definition of, 63 Chlorindoptin, 296 Chlorine, 59 as a bleaching agent, 67 first introduced, 70 compounds of, 59 action of light upon, 14 action of, on indigo, 294 Chlorisatin, 296 Chlorous acid, 61 Chromate of lead, 194 red, of potash, 192 affected by light. 15 as a mordant, 197 test for, 198 Chrome greens, 196, 295 orange, 196 yellow, 194 Chromic acid, 191 acid on indigo, 294 Chromium, oxides of, 189 salts of, 190 Chryso-rharanine, from Persian ber- ries, 347 Cinnamule, 291 Citric acid, 243 . Coal, quantity to boil a given weight of water, 7 Cobalt, and its salts, 1G3 Cochineal, 385 action of salts upon, 386 Colours, ai-rangement of, 1 7 harmony, law of, 18 changed by heat and moisture, 8 produced by light, 244 permanence affected by fabric, 9 of flowers, 246 Colorinc, 361, 364 Commercial uidigoes, 286 Compounds, niles for naming of, 24 Constitution of salts, 31 Copper and its salts, 168 sulphate of, 169 Copperas, manufacture of, 152 different qualities of, 165 testing of, 157 Coromandel indigo, 287 Cream of tartar, 236 Croft bleaching, definition of, &c. 68 Crum, W., method of testing bleach- ing solutions, 81 on testing of indigo, 279 on composition of indigo, 289 on sulphate of indigo, 296 Cudbear, 370 Curcumine, colouring matter of tur- meric, 347 Cyanide of potassium, 120 Cyanides, 107 Cyanogen, preparation of, 106 Dalton's, Dr. table of strength ol' potash leys, 112 Dana's, Dr. method of testing indigo, 278 Davy, Sir W. on constitution of salts, 32 Didymium, 217 Divi divi, 268 Double salts, definition of, 29 Dumas on composition of indigo, 289 theory of blue vat, 303 Dung bath, 147 Dutch madder, 354 Egyptian indigo, 288 Electricity in stove-dried goods, 145 Elements' of matter, 20 table of, 21 symbols and equivalents of, 22 Epsom salts, 135 Erbium, 217 Expansion of air and water by neat, 3 400 INDEX. Extract of indigo, 299 Exti-active matter, 265 Fabric, affecting permanence of colour, 9 relation to colour, 1 1 Fahrenheit thermometer, 4 Ferrocyanide of potassium, 115 Flavine, and action of salts, &c. upon, 344 Flowers, colours of, 246 Fluidity depending on heat, 2 Fluorine and its compounds, 101 French method of dveing wools blue, 307 Fustic, action of re-agents upon, 340 Fustic, young, 340 Gallic acid, 243, 249 GaUs, 248 effects of salts on solutions of, 254 several sorts of, 256 analysis of, 257 Gambouge, 242 Garancine, 361 how prepared, 362 pi'operties of, 362 Gaseous condition of matter, 2 Gases absorbed by carbon, table of,47 German blue vat, 316 Glucinum, 135 Gold and its salts, 211 ornaments of cloth injured, 113, 127 J . ' Green dyed by chemic, 301 of vegetables, 244 chrome, 196 vitriol, 152 Gregory's and Liebig's theoiy of bleaching, 85 Guatimala indigo, 288 Gum, 241 Harmony of colours, principle of, 17 Hartshorn, 59 Hazel as a dj'e, 268 Heat the cause of condition of mat- ter, 1 absorbed bj' steam, 7 effects of upon colour, 8 in mixing vitriol and water, 92 Hematoxylin, colouring principle of logwood, 323 Herschel, Sir John, on colour of flowers, 247 Horse chesnut as a dye, 268 Hunt's experiments on light and colour, 245 Hydrates, meaning of term, 27 Hydrogen. 38 properties of, 39 binoxide, bleaching properties of, 48 Hydi-ochlorates, 63 Hydrochloric acid, 62 testing of, 63 Hyperchloric acid, 62 Hypochlorites, 61 Hypochlorous acid, 60 Hyposulphuric acid, 96 Hyposulphurous acid, 95 Indian vat, 315 Indigo, 270 affected by heat, 9 test for bleaching solution, 79 theories of its manufacture, 273 testing of, 277 analysis of, 278 commercial, 286 varieties of, 289 chemical composition, 289 theory of wliite and blue, 290 action of fused potash upon, 292 of nitric acid upon, 292 of chromic acid upon, 293 of chlomie upon, 294 sulphate of, 296 Crum upon, 296 Dumas upon, 297 extract, 299 Indigogen, 301 Influence of circumstances on affinitv, 30 Iodine and its compounds, 99 tests for, 100 Iron and compounds, 151 affected by sun's rays upon, 1 5 dissolving in rfitric acid, 57 its passive state, 58 chloride test of bleaching solu- tions, 81 liquor, 158, 233 nitrate, 16 sulphate, 152 solubility of, 153 different qualities of, 155 testing of, 157 salts of, 157 and tin for royal blue, 234 INDEX. 401 Isatine, 293, 296 Isomeric bodies, 241 Jamaica logwood, 321 Java indigo, 288 Kane's, Sir Robert, theory of bleach- ing, 85 theory of indigo manufacture,274 Kerms, and its reactions, 390 Killing iron, 161 Lac dye, 389 Lake lake, 389 Lanthanium, 217 Lead, 171 melting point of, 2 salts of, testing their value, 176 acetate of, 173 ch rem ate of, 194 nitrate of, 173 Levant madder, 354 Ley potash, 1 1 1 Libi davi, 268 Liebig on indigo, 291 on bleaching, 85 on vegetables, 246 Light, its nature and properties, 10 aiffected by chemical changes, 1 2 effects of different rays of, 13 effects upon colours, 13 nitrate of iron, 16 bleaching, 87 Lime, caustic, 134 solubility of, 134 sulphate, 135 carbonate, 135 chloride, 74 testing solutions of, 74 hypochlorite, 74 Litharge, 174 Lithium, 129 Logwood, 321 chemical composition of, 322 testing value of, 323, 329 decoctions of, how to prepare,327 Luteoline, colouring principle of weld, 346 Madder, 353 different sorts of, 354 impurities of, 356 pui-ple, 358 red, 359 orange, 359 yellow, 359 Madder, brown, 360 acids, 3G0 useful products from, 360 action of salts, &c. upon, 364 Madras indigo, 288 Magnesia, 135 Mahogany saw-dust as a dye, 268 Malabar catechu, 265 Management of blue vats, 318 Manganese, 148 browns, 150 Mangi'ove tree as a dye, 268 Manilla indigo, 288 Matter, properties of, 1 Measure of heat, 4 Mellon and mellonides, 107 Mercury, and its salts, 208 freezing point of, 2 Metals, 148 Milk, S01U-, used in bleaching, 68 Mineral camcleon, 150 Molybdenum, and salts of, 200 Molybdic acid, 200 Mordants, aflected by heat, 9 affected by light, 15 their uses, &c. 218 acids of, 222 oxidation of, 223 astringent matters as, 2*26 cream of tartar as, 235 theory of, 235 Morin, colouring principle of fustic, 340 Munjeet, 365 Muriate of tin, 183 Muriates, 63 Muriatic acid, 62 Myrobalaus, 268 New dyes, 372 Nickei; 165 salts of, 165 Niobium, 217 Nitrate of iron, 57, 159, 233 effects of light upon, 16 of bismuth, 177 of copper, 170 of lead, 173 of silver, 210 of tin, 181 of zinc, 167 of potash, 114 of barvtes, 133 ofsodii, 128 Nitric acid, 52 402 INDEX. Nitric acid, efifects of light upon, 54 impurities in, 55 table of strength, 56 Nitrogen, 48 compounds of, 50 Nitrous acid, 51, 54 Nomenclature, rules for, 24 of salts, 26 Norium, 217 Oak bark, 268 Oil of bitter almonds, 291 cassia, 291 cloves, 242 potatoes, 242 turpentine, 242 Orange dye, 175 chrome, 196 Orpiment, 204 Orseine, from archil, 371 Osmic acid, 216 Osmium, 216 Oxalate of chromium, 191 of copper, 171 of potash, 115 OxaUc acid, 105 impurities in, 105 curious salt of, 106 Oxides of carbon, 104 copper, 169 iron, 151 manganese, 149 Oxidation of mordants, 223 Oxygen, its nature and properties, 36 identified with chlorine, 71 Oxymiuiatic acid, 72 Ozone, 87 Palladium, and its compounds, 214 Pastel, 307 vats, how made up, 309 Peach-wood, 332 Pearlash, 110 Penney's, Dr. test for tin salts, 184 for indigo, 286 Pelopium, 217 Persalts of iron, 163 Persian berries, 347 Persis, 370 Persulphate of iron, 159 Phinacm, 296 Phosphate of potash, 115 soda, 128 Phosphorus and its compounds, 98 Picric acid, 293 Pittacal, a new dye, 382 Platinum, and its salts, 213 Plumb spirits, 186, 232 tub, 330 Potash, manufactvu-e of, 110 ley, table of strengths. 112 value of commercial, 113 salts of, 114 vat, how made up, 316 action of, upon indigo, 292 chlorate, 61 nitrate, in nature, 53 cyanate, 120 red prussiate, 119 yellow prussiate, 115 Potassium, 109 cyanide, 120 iodide, 100 Pressier, M. on indigo, 292 Prism, the, and what it is, 11 Properties of oxygen, 37 Ught, 10 Protosalts of iron, 163 Prussian blue, how dyed, 117, 160 effects of hght upon, 8, 13 Prussiate of potash, 115 Prussic acid, 33 Pyrolignite of iron, 233 PjToxilic spirit, 242 Queen-wood, 331 Quercitrine, colouring matter of bai-k, 342 Quercitron bark, 341 effects of heat upon solutions of, 8 its solubility in solutions of other woods, 343 method of dyeing by, 343 Raising, 221 Realgar, 204 Red chromate of potash, 192 prussiate of potash, 119 Red spirits, 185 Resin of gambouge, 242 Resist pastes, 146, 292 Rhodium, and its salts, 216 Roman alum, 137 vitriol, 170 Rot steep, 84 Royal bhie, 118,234 Rules for naming compounds, 24 Ruthenium, 217 403 Safflower, 347 how prepared, 348 to dye with, 351 peculiarity in dyeiug with, 351 Safflower reds, action of heat and moisture upon, 8 Salammoniac, 58 Salts, nature and nomenclature of, 26 double, 27 basic, 27 constitution of, 31 making solutions of, 45 rates of solubility of, 45 of bismuth, 178 of cadmium, 168 of chromium, 198 of cobalt, 164 of copper, 168 of gold, 213 of iron, 151 of manganese, 150 of mercurj', 209 of nickel, 165 of palladium, 215 of platinum, 214 of silver, 210 of tin, 180 testing of, 181. 184, 230 of yanaddum, 199 of zinc, 167 Salt radicals, 33 Sandal-wood, 334 Santa martha-wood, 332 Saunders-wood, 334 Scheele's green, 203 Schcinbein, Prof, on ozone, 87 Seed lac, 389 Selenium, 98 Senegal indigo, 288 Shell lac, 389 Sihcium, 101 Silk, bleaching of, 87 composition of, 227 SDver, melting point of, 2 salts effected by light, 15 and compounds of, 209 Smalt blue, 164 Soap, testing of, 129 Soda, 121 ash, 123 value of, how tested, 123 table of the value of solutions of, 127 borate, 102 nitrate of, 53 Soda, salts of, 128 Sodium, 120 chloride of, 128 Solidity an effect of heat, 2 Solubihtj' of soda in water, 127 Sooranjee, a new dye, 372 Souring goods, 83 Specific gravity of hydrochloric acid, 64 of nitric acid, 56 of sulphuric acid, 94 Spirits, variety of, 185, 230 Stano-arsenite of soda, 182, Starch, 241 Steam, heat of, water boiled bj', 8 Stenhouse, Dr., researches on, 248 Stick-potash, 113 Stove for drying, 9 Strontium, 133 Substantive colours, 226 Sugar, 241 Sugar of lead, 173 Sulphate of antimony, 205 of chromium, 190 of copper, 169 of indigo, 297 of iron, 154 of lead, 176 of lime, 135 of nickel, 165 of potash, 114 of silver, 210 of soda, 127 of tin, 181 of zinc, 167 Sulpho-indilic acid, 297 Sulpbo-purpuric acid, 297 Sulphur, 88 Sulphurets of arsenic, 204 of iron, 154 Sulphuretted hydrogen, 96 a test for metals, 97 effects of upon colours, 98 Sulphuric acid, 90 fuming, 92 and water, heat evolved by, 92 testing impurities in, 94 Sulphurous acid, 2, 88 as a bleaching agent, 89 Sumach, 258 different sorts of, 258 effects of iron salts upon, 260 Sim's rays, effects of, on salts, 15 Swimming of a blue vat, 304 Symbols, their uses, 22 404 ixnEx. Table of fluid and gaseous points of matter, 2 of elements, 21 of solubility of salts, 46 of different thermometers, 5 of hydrochloric acid, 64 of sulphuric acid, 94 of nitric acid, 56 of relative values, bleaching- powder, 77 of heat, by mixing water aud sulphuric acid, 92 of gases absorbed by carbon, 103 of solubility of gases, 47 of strength of potash solutions. 112 ofvalue of commercial potash, 113 of strength of soda solutions, 127 of compounds between indigo and chlorine, 296 Tartaric acid, 235 Tai-trate of chromium, 191 potash and tin, 181 Tannic acid, 243 Tannin, 249 tests for, 265 Tellurate salts, 202 Telluric acid, 201 Tellurium, 201 Temperature of water boiling by steam, 8 Terbium, 217 Testing, method of, for water, 40 bleaching powder, 74 vitriol, 93 by sulphuretted hydrogen, 97 for oxaUc acid, 105 for soda-ash, 1 23 soap, 130 acetate of alumina, 144 lead salts, 176 value of indigo, 278 Tests used for water, 44 for hj-drochloric acid, 63 for chromium, 198 for tannin, 265 Theory of blue vat, 302 Thermometer, diflerent sorts of, 4 Thomson's, Dr. theory of indigo manufacture, 274 Thorium, 135 Tin, 178 first introduced in dyeing, 179 protochloride, 180 protosulphate, 181 Tin, protonitrate, 181 tartrate of potash and, 181 perchloride of, 183 salts, testing value of, 184 spirits, 185 acetate, 187 oxalate, 187 Titanium, 188 Tungstenum, 189 Turmeric, 347 Uranium, 206 Ure's, Dr. theory of manufacture of indigo, 274 Use of symbols, 22 Valerianic acid, 296 Valouia nuts, 267 Value of potash solutions, 112 comparative of commercial pot- ash, 113 of soda-ash, 123 solutions, 127 of copperas, 155 Vanadium and its salts, 198 Vats, management of, 318 Vegetable matters used in dyeing, 240 Venetian sumach, 341 Verdigi'is, 17) Vitriol, Roman, 170 ■\Valnuts, as a dye, 268 Water, its freezing and boiling poiuts,2 expansion by heat, 3 steam and coal to boil, 7 boiling bv steam, temperature of, 8 composition of, discovered, 39 properties and uses of, 40 testing and purifying of, 42 analysis of, how made, 42 to make solutions in, 44 absorbing of gases by, 47 Weld or wold, 345 action of salts, &c. upon. 346 White, produced by combuiation of colom-s, 12 spots on d3'ed goods, 84 copperas, 167 lead, 173 indigo, 290 Willows, as a dj^e, 268 Woad, 307 vat, to make up and keep, 313 Wolfram, 199 405 Wongshy, a new dye, 377 action of salts, &c. upon, 378 Woody fibre, 241 Wool," bleaching, 87 dyeing, 308 Xantho-rliamnine, colouring matter of Persian berries, 347 Xanthin, 357 Yellow prussiate of potash, 1)5 spirits, 187, 232 chromate of potash, 192 wood, 239 Young fustic. 341 action of salts, &c. on, 341 Yttrium, 135 Zinc and its salts, 166 c L A ? o ^^• ; rBISTf.l> BY BELI. 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