3; j. 5 a : , 5 mH^^^H ^■^■HHH Experimental Refearches CONCERNING THE PHILOSOPHY OF PERMANENT COLOURS; AND THE Belt Means of producing them, by Dying, Callico Printing, &c. By E DWA'fiS **fe 'A 'N^CR 6't*T; M.D. FELLOW J7F. T.SB RQY 41^ SCK1I EJty, SsC.^ ■rrrtr-.: : :::••» '< Cet art (de la teinture) eft un des plus utiles et des plus mcrveilleux *' cu'on connoifie ; & ii quelque un peut infpirer un noble orgueil a « l'homme, c'eft celui la: non feulment il a procure le moyen de «« fuivre et d'imiter la nature dans la richeiTe & Teclat des couleurs ; « mais il paroit 1'avoir furpafle en donnant plus d'eclat, plus de fixite " & plus de folidite aux couleurs fugaces & paftageres dont elle a revetu " tous les corps qui compofent ce globe." Ciiaptal, Element dc Cbimic, torn. iii. p. 185. VOL. I. LONDON: PRINTED FOR T. CADELl, JUN. AND W. DAVIES, (SUCCESSORS TO MR. CADELL,) IN THE STRAND. M DCC XCIV. ■BBSSEiSt. 3 PREFACE. AConfiderable part of this Volume was printed early in the year 17925 but vari- ous interruptions have fince concurred in delay- ing its conclufion. A fecond Volume is in- tended to follow, and complete my prefent plan ; the materials of which are nearly all provided, though I cannot expecl: that it wjll be publifhed until near the end of the enfuing year. That and the prefent volume will contain the refults of many thoufands of experiments, and of much obfervation and reflection, during the fpace of twenty-five years, in which this fubjeft has been my principal occupation j and as it will probably continue to occupy a great part of my time, whilft life and health are prolonged to me, I may be allowed to hope, that future dif- coveries will hereafter enable me to publifli at lead one other volume as fupplementary to thefe, which are intended to convey all the knowledge 1 have hitherto acquired on this fubject. The prefent volume comprehends what I have to offer concerning the different animal, veget- A 3 able, 76 7 S^S^ VI PREFACE. able, and mineral colours, and colouring matters of that clafs which I have denominated fubjlan- five, becaufe they do not depend upon any bafis or mordant, either for their permanency or their luftre : and alfo what I have to commu- nicate refpec"ting the colouring matters of an animal nature, belonging to the other clafs or divifion, which I have called adjeclive co- lours, becaufe they are capable of being en- livened and fixed only by being adjected or ap- plied upon a fuitable bafis : and it alfo contains fuch of the vegetable adjective colouring mat- ters as are ufed, or capable of being advanta- geoufly ufed, in producing the various fhades of yellow. The fecond volume is intended to compre- hend all the remaining adjective colours and co- louring matters, particularly thofe very inte- refting ones which are derived from the tribe of madders, the different fpecies of gallium, and Other roots employed in Afia, as well as in Eu- rope, to produce permanent reds j the different red, purple, and other dying woods now in ufe, with many which never were ufed, at leaft in Europe, except by myfeif -, and alio the different vegetable matters which become black by being combined with iron; refpecting which I mail have many new and important facts to communicate. I 8 . (hall PREFACE. vii fhall alfo in the fecond volume refume and pro- fecute, as far as I may be able, fome abftrufe but interefting inquiries relating to the caufes which influence not only the production but the variations and decays of colours, of which in- deed the prefent volume affords many intima- tions, though my final conclufions on this fub- ject have been delayed for the refults of par- ticular experiments, which I have not hitherto been able to profecute fatisfactorily. And in- deed, refpecling fome part of what I have been able to do in this intricate enquiry, I may fay with M. Sennebier, " je ne -puis dijftmuler que fai vu varier mes experiences d'une maniere propre a me confondre ; quoique je Juivijfe confiamment les mimes procedes, du moins en apparence, je dots le dire, j'ai vu des refultats oppofes." (Mems. Phyfico-Chyms. &c.) And perhaps there is none of thofe who have been long en- gaged in chymical purfuits, to whom fimilar difficulties and difappointments have not oc- curred. Nothing but a hope that this work may pro- duce confiderable public benefit could have in- duced me, amidfi: other numerous avocations, thus to employ the time and attention which have been neceffary to produce it. I fed, how- ever, that it will be far, very far from deferving the A 4 character viil PREFACE. character of a perfect work, and, in truth, that chymical fcience is far from having attained that ftate which is neceffary to perfection on this fubject, The .objects, and the knowledge re- quired for a complete treatile on dying and cal- lico printing, are indeed fo various and exten- five, that what Sennebier has faid of fuch a performance will always be true, " Cet ouvrage jeroit immenfe; il ne conjljle pas en falts ifoles, qiCil Juffit d y examiner Jeparement ; c y eft un en- Jemble prodigieux a creer, Joit par la reunion des faits counus et de leurs applications, Joit par la recherche des faits nouveaux" &c. In arranging the objects of my prefent under- taking, I have adopted that plan which would, as I thought, beft enable me to convey my ideas intelligibly, with the feweft repetitions, and without feparating matters efTentially con- nected to each other. In purfuing it, I have endeavoured to avoid minute defcriptions of fuch manual and mechanical operations of dying and callico printing, as are not connected with the principles of the art; becaufe artifls know them already, and, to mere fpeculative readers, a knowledge of them would be ufelefs. IVIy Readers will fee, that I have adopted the terms of the New Chymical Nomenclature, and PREFACE. IX and alfo (with a very few exceptions) the prin- ciples to which it relates : and I have done this, not becaufe Tconfider them as forming a perfect fyftem, or imagine that we are yet acquainted with all the minute and abftrufe caufes of chy- mical effects, but becaufe I confider the new doctrines as according much better with facts than the old ; and as being much better fuited to become parts of a perfect fyftem, when fuc- cefilve difcoveries (hall at length afford the means neceffary to its attainment. And though there are fome truly refpectable chymiils, whofe minds, ftrongly prepoffeffed by ideas and opinions for- merly received, have not yet become acceffible to the fuperior evidence which fupports the new fyftem ; yet their number is continually diminifh- ing, and, in a fliort fpace, the generation itfelf, to which thofe of us belong, who either were, or continue to be, prejudiced on this fubject, will have fajed away ; and, judging by the fen- timents of thofe who are likely to ftand fore- moft among our fucceffors, there can be no difficulty in forefeeing which of thefe fyftems muft prevail. London, Auguji 25th, 1794. The Reader is defired to corredl the following more ma- terial Errors of the Prefs, . Oxygene. Oxygenated muri- atic acid. Oxygenated muri- atic acid gaz. P. Phofphates. Phofphate of tin. Pot-afti. Pruiuaa or PiuCic acid. Frufiiates. Prufliatc of ammo- niac. Prufliate of lime. Prufliate of pot-afh. Pruiliateof foda. Pyrolignecus acid. Pyrolignites. Pyrolignite of iron. Soda. Subtlantive colour- ing matter. Sulphates, Sulphate of alu- mine. Sulphate of barytes. Sulphate of bif- inuth. The bafis of pure or vital air. The ■ aerial acidifying principle. Muriatic acid, with an addition of oxygene; formerly called dc- phlogiflicated marine acid. The oxygenated muriatic acid com- bined with caloric, by which it is raifed into the form of an da (lie fluid. Salts formed by the combination of the phofphoric acid with differ- ent bales. Tin combined with phofphoric acid. Cauflic vegetable alkali. The acid of Pruflian blue. Combinations of the Pruflic acid with different bafes. Ammoniac combined with Pruflic acid, or colouring principle of Prufiian blue. Lime combined with Pruflic acid. Pot-afh combined with Pruflic acid. Soda combined with Pruflic acid. The empyreumatic acid, obtained by diltillation from wood, &c. Combinations of the pyroligneous acid with different bafes. Iron combined with pyroligneous acid. Cauflic fofiil alkali. Colouring matter which requires no> bafis or mordant to give it luf- tre or permanency. Salts formed by the combination of the fulpli uric acid with different bafes. Alumine combined with fulphuric acid. Common alum. Barytes combined with fulphuric acid. Bifmoth combined with fulphuric acid. Sulphate EXPLANATIONS OF NEW TERMS. xvii Sulphate of copper. Sulphate of indigo. Sulphate of iron. Sulphate of lime. Sulphate of mag- nefia. Sulphate of manga- nefe. Sulphate of pot-afh. Sulphate of tin. Sulphate of zinc. Sulphureor fulphu- ret of antimony. Sulphureof arfenic. Sulphure of pot-afh. T. Tartaro-nitrates. Tartaro-nitrate of tin. Tartaro-fulphates. Tartaro-fulphate of tin. Tartrites. Tartrite of alu* mine. Tartrite of tin. Copper combined with fulphuric acid. Blue vitriol. Indigo combined with fulphuric acid. Iron combined with fulphuric acid. Green vitriol, or copperas. Lime combined with fulphuric acid. Selenite. Magncfia combined with falphuric acid. Kpfom fait. Manganefe combined with fulphuric acid. Pot-afh combined with fulphuric acid. Vitriolated tartar. Tin combined with fulphuric acid. Zinc combined with fulphuric acid. Combination of fulphur with anti- mony; formerly called crude antimony. Combination of fulphur wrh arfenic. Sulphur united to pot afh; or liver of fulphur. Combinations of the tartareous and nitric acids with different bafes; the tartareous acid being in the greater proportion. Tin combined with the" tartareous and nitric acids. Combinations of the tartareous and fulphuric acids with different bafes ; the tartareous acid being in the gn-ater proportion. Tin combined with the tartareous and fulphuric acids. Combinations of the tartareous acid with different bafes. Alumine combined with tartareous acid. Tin combined with tartareous acid. E *i* J CONTENTS. Introduction, refpedTmg the origin and progrefs of dying ; and the means, authors, &c. by which it has been improved. CHAP. I. Of the Permanent Colours of Natural Bodies. Account of Sir Ifaac Newton's difcoveries refpe£ting light and colours, p. i — -4. Euler's notion of the propagation of light, 4. Refutation of fome opinions contained in the Second Book of Sir Ifaac Newton's Optics, concerning the changes, &c. of colours, 5—10. Mr. Delaval's dodrine of the agreement between the fpecific gravi- ties of metals and their colours, when united to glafs, refuted j and the permanent colours of bodies fhewn not to arife from their denfities, or the fizes of their particles, 10 — 27. The colours of bodies proved not to depend on their inflamma- bility, 27. The origin and changes of co'ours in moft cafes fhewn to depend on the application or combination of different airs or gazes,- and particu- larly of oxygene in different proportions, 28 — 57. The influence of light in producing changes of colour, proved by experiments upon the nitric acid by itfelf j and alfo when applied to animal fub- ftances, 31. As well as upon muriate of filver, 34. Nitrate of filver, 36. Nitrate of mer- cury, ibid. Upon arfenic and manganefe, 37 ; a 2 and xx CONTENTS. and upon plants, as noticed by Ray, Bonnet, In- genhoutz, and Sennebier, 38 — 44. Alfo by its in- fluence on the human fkin, 44. On the nereis lacuftris and other infects, 45. On the tree frog, and on filk, cotton, and white lead paints, 46. Ideas of the author refpecting the black colour of charcoal, 48. The opinion of M. Berthollet, that the decays of vegetable and animal colouring mat- ters refult from effects fimilar to thofe of com- buftion, fliewn to be not always well founded, 49. Effects of oxygene on the colours of blood, indigo, &c. 52, 53. Colours of bodies depend on certain affinities or attractions, chymical or phyfical, by which they are difpofed to abforb or conceal fomc of the rays of light, and to reflect or tranfmit other * avs > 57- CHAP. II. Of the Compofition and Structure of the Fibres of Wool, Silk, Cotton, Linen, &c. The reafon explained why animal fubftances attract colouring matters more generally, and are mors readily injured by acids, alkalies, and other che- mical agents, than vegetable fubftances, 58. Sir Wm. Petty's account of fulling, 60. Mr. Monge's account of felting and fulling, 61. Conformation of the fibres of wool, and elafticity thereof, ibid. Confequences of this elafticity in dying, 62. Na- tural colours of wool, 63. Introduction of filk into Europe, 64. Manner of freeing filk of its varnifh and yellow colour, 65. Nature of filk, 66. An account of M. Ben's difcovery of a new kind of filk, 67. Of the cotton plants, 68. Of the fibres of cotton, 69. M. le Pileur d'Apligny's opinion, that the durability of colours dyed on ani- m il and vegetable fubftances depends on the fize of their pores, proved to be contrary to fact, 70. CHAP. CONTENTS. XXI CHAP. III. Of the different Kinds and Properties of Colouring Matter employe din Dying, Callico Printings &V. Colouring matter defined, 72. The distribution of colouring matter in mineral, animal, and vegetable fubftances, explained, ibid. Peculiar chymical pro- perties of colouring matters, ibid. Opinions of Sir Ifaac Newton and Mr. Delaval refpecting coloured matters, 73. Of fimple and compound colours, 75. Of the attempts to arrange and clafs colouring matters, 77. Divifion of them by the author into fubfiantive and adjeftive, 78. CHAP. IV. Of Subflantive Animal Colours. Of the purple dye of the ancients, 78. Pliny's ar- rangement of the fhell- fifties giving the purple dye, 79. Places where the feveral fpecies of thefe fhell- fifhes have been found, ibid. Manner of extracting the liquors which afforded the purple colour, and of dying therewith, 80. Varieties in the colour, ibid. Mr. Cole's account of the difcovery of the buccinum on the coafts of Somerfetfhire and South Wales, in 1683; and of the fucceilive changes of colour which took place in the colouring liquor ob- tained from this fhell-fifh, &c. 81 — 84. Of a fmall fpecies of buccinum found on the weftern coafts of France, by Mr. Juffieu, in 1709; and of the fame, with certain fmall eggs or grains, yield- ing a purple dye, found by Mr. Reaumur, in 17 10, 84. Mr. Reaumur's experiments thereon, with re- marks by the author, 84 — 88. Mr. Duhamel's difcovery of the purpura, and experiments with it, ibid. Two ways of accounting for the production of the purple colour from the liquor of thefe fhell- fifhes, 91. Of certain fhell and other fifties and infects which afford particular colours, 93 — 97. a 2 CHAP xxxi CONTENTS. CHAP. V. Of Vegetable Subfiantive Colours. Introduction of the indigo dye into Europ?, 97. Three fpecies of indigo plants, 98. Manner of extracting the indigo from the plant, 99. Chvmi- cal properties of the indigo, and remarks on the preparation of it, 100. The varieties of indigo, 102. Of the effe&s of nitric, fulphuric, and oxygenated muriatic acids on indigo, 103. Of the ifatis or woad, and the ways of preparing it, 106. Manner of employing the woad with indigo for dying, 108. Of the different blue vats, and their ufe in dying wool, filk, and cotton, ibid. Mr. HauiTmann's obfervations on this fubject, with re- marks, 1 10 — 117. Interefting experiments by the author on the folvent powers of different fubftances when combined with indigo ; and of certain im- provements in the preparations of indigo for pen- ciling, &c. 117 — 128. Remarks en the manner of preparing indigo for dying the Saxon blue, 1 29 — 137. Chymical analyfis of indigo, 137. Of the genipa Americana Linn, and its properties, 138 — 142. Other plants affording a fubftantive blue colour, ibid. Of a fuppofed green indigo, 144. Of fubftantive vegetable yellows, 145. Of the berberis vulgaris Linn. 146. Of the xanthoxylum clava herculis Linn, and bixa orellana Linn. 147. Of the lawfonia inermis Linn. 149. And of plants affording fubftantive black and other colours, 150-155. C K A P. VI. Of Mineral Subfiantive Colours. Of iron, diffolved in acetous acid, the acid of tar, and the nitric and muriatic acids, as a fubftantive colour, 157. Of copper, diffolved by ammoniac, fulphu. ric CONTENTS. XXU1 tic acid, &c. as £ fubftantive green, 159. Of the nitro-muriate of £old, as affording a fubftantive purple, 160. Of the nitrate of filver, and its effects, 162. Of the oxide of mercury, 164. Of the nitro-muriate of platina, ibid. Nitrate of co- balt, j 65. Curious effects of oxide of cobalt dif- folved by muriatic acid, ibid. Nitrate of nickle, ibid. Nitrate of manganefe, 166. And oxide of lead, ibid. CHAP. VH. Of Adjeftive Colours generally. Of mordants or bafes, 167. Of their antiquity, 170- Hiftory of the origin and progrefs of callico print- ing, 172 — 176. Remarks on the aluminous mor- dant, or acetite of alumine, 176—184. Experi- ments, &c. tending to illuftrate the differences of colouring matters, as well as the action of the alu- minous bafis when employed in dying, 184 — 189. Of the application of the aluminous bafis to linen and cotton, 190. 'To filk and wool, 192. Of the ufe of iron in fixing colouring matters previ- oufly applied to wool and filk, ibid. Mr. Hauff- mann fhewn to be miftaken in confidering alumine and the oxide of iron as the only mordants or bafes, 193. Remarks on Mr. Berthollet's opinion, that certain colours refult from combuftion, 197. CHAP. VIII. Of Pruffian Blue. Confidered as refulting from an animal adjective co- louring matter, with the bafis of iron, 198. Dif- covery of it, ibid. Manner of preparing it, 199. Of the action of different acids on Pruflian blue, 200. Means of diflblving or decompofing the Pruffian blue, 201. Its analyfis, ibid. Attempts a 4 of XXIV CONTENTS. of various perfons to fix the Pruilian blue equally by dying, &c 202 — 207. Experiments of the author* to {hew that an olive colour produced by weld and iron liquor could not become green bv the applica- tion of Pruflian blue, as Mr. Berthollet mentions, without the aid of alumine or oxide of tin, 207 — 213. Experiments to ascertain whether any affinity exifted between the aluminous bafis and the co- louring matter of Pruflian blue, 213. Experiments made with different folutions of copper, fhewing the effect of that metal in fixing the colouring mat- ter of Pruflian blue, 214. Refults of experiments made wiih folutions of other metals and femi-metals, as bafes of the Pruflian colouring matter, and cf the different colours produced by them, 216. Dif- covery of a very beautiful and durable colour, ob- tained by the author, from the Pruflian colouring matter and the copper bafis, 217. CHAP. IX. Qf Adjetlive Colours from European and Jfatic Infefls. Of the kermes, 220. Manner of preparing wool, &c. for the kermes dye, 223. Of lacca, or gum- lac, with Mr. Kerr's description and hiftory of the infect producing it, 224—227. Dr. Roxburgh's account of the lacca infects, 227. Method of ex- tracting the colouring matter from lacca, 231. Of the coccus tinctorius polomicus, 234. Of the coccus uvx urfi Linn. &c. 235. CHAP. X. Of the Natural Hi/lory cf Cochineal. Defcription of the coccus cacti Linn. 236. Of the plant on which this infect lives, 237. Opinions publifhed by different authors concerning the cochi- neal, CONTENTS. XXV neal, 238 — 244. Of the varieties of the cochineal, 244. Account of M. Thiery de Menonville's ex- pedition in queft of the cochineal infect, and of the eftablifhment he formed at St. Domingo for propa- gating it, 245. Of the fuperior fitnefs of the true and Caftile nopals, for rearing cochineal, 247. Of the generation, &c. of thefe infects, with the me- thods of gathering and drying them, 248. Of the difference between the fine or domefticated, and the wild cochineal infects, 249. Method ufed in Mexico to prevent thefe two kinds of infects from mixing with each other, and of the probability there is, that both kinds had the fame origin, 25Q. Ex- periments of Mr. Berthollet and others, with the wild cochineal, 252. Of the farina adher- ing to the fine cochineal infects, ibid. Of the wild cochineal, 254. The colour of the cochineal not derived from the fruit of the nopal, 255. Of the quantity of cochineal imported into hurope, 257. Of the infect: which Dr. James Anderfon of Madras miftook for the true cochineal infect, 258. CHAP. XL Of the Properties and Ufes cf Cochineal ; with an Account of new Objervations and Experi- ments calculated to improve the Scarlet Dye. Of the bafis formerly employed by the Mexicans for dying with cochineal, 262. Difcovery of the fcarlet dye, 263. Error of the prevailing opinion refpeding the effect of the nitric or nitro-muriatic folutions of tin upon cochineal, in producing the fcarlet dye, 264. Of the manner in which the muriatic acid began to be ufed with the nitric, in order to produce a folution of tin, 265. Method of making the dyer's ordinary folution of tin or (pirit, with an account of the manner of dying the cochineal fcarlet, 266. Remarks on the different boiiin^s commonly employed for dying fcarlet, 268. On ssvi CONTENTS. On the ufe of tartar in that operation, 269. Rea- sons why Mr. Berthollet thinks the nitro-muriatic folution of tin is improved by fal ammoniac, &c. 270. Pure water found not to extract, the whole of the colouring matter of cochineal, 271. Of a very important faving which may be made by employing Quercitron bark with cochineal, in compounding and dying the fcarlet colour, 272. Corrofive na- ture of the muriatic folution of tin upon the fibres of wool, &c. 281. The idea that the natural crimfon colour of cochineal is changed towards a fcarlet hue by the nitric acid, proved to be errone- ous, 285. Effect, of tartar on the colour of cochi- neal in dying fcarlet, 288. Of the good effeds of a murio-fulphuric folution of tin in dying fcarlet, 289. A new method of dying fcarlet, by means of cochineal and Quercitron bark with a murio-ful- phuric folution of tin, 291. Importance and ad- vantages attending this new method, 293. Vari- ous experiments (hewing how much the ufe of the Quercitron bark with cochineal, in compounding and dying fcarlet, is preferable to that of tartar with cochineal, 296. Other experiments (hewing the effecls of different earthy and metallic bafes upon the colouring matter of cochineal, 300—310. Of Mr. Macquer's method of dying a fcarlet upon filk, on. A new method of dying fcarlet on filk, 312. Colours given to filk by cochineal with different earthy and metallic bafes, 312. Of dying fcarlet upon cotton, 313. Of the methods employed for this purpofe by Scheffer and Dr. Berkenhout, 314. Of a new method of dying a fcarlet on cotton, 016. Of an improvement in the red colours given by madder, 317. Of a profubftantive fcarlet co- lour for callico printing, 318. CHAP. XII. Of the Properties and Ufes of Quercitron Bark, Of the tree from which this bark is obtained, &c. 310- Of the manner of preparing the bark for dying, 320, 32©*»?v CONTENTS. xxvii -^20. Of the extract obtained from the baric, 321. Varieties of the quercus nigra, ^22. Effects of various chymical agents on the deco&ion of Quer- citron bark, ibid. Of the application of Quercitron bark for the dying of wool and woollen cloths with an aluminous bafis, •222. Method* ot dying yellows and greens in this way upon wool, 423 — 329. Of the methods of dyinsr all the different fhades of yellow, from the hitiheit orange to the paleft lemon colour, upon wool, with Quercitron bark and a tin bafis, 329 q?^. Method of applying the Quercitron bark topically upon woollen fluffs to produce yellows and greens, 335. Manner of dying Saxon greens with fulphate of indigo and Quercitron bark, &c. 336. Mr. D'Ambourney's remarks on dying greens upon wool with Quercitron bark and indigo, 338. Of the colours obtained from Quercitron bark with different folutions of tin, 339. On the ufe of cop- per with Quercitron bark, 342. Of the ufe of this bark with folutions of iron and other metals in dying wool, 343. Of the properties and ufes of Quercitron bark in dy- ing upon filk, 345. Of the application of Quercitron bark to the fibres of linen or cotton, either woven or fpun, by general dying, 347. Of the neceffity of precipitating the alumine more copioufly for dying upon linen and cotton, than for dying upon wool, ibid. Prepara- tion of linen and cotton, 348. Of the dying yellow upon linen and cotton with the Quercitron bark and an aluminous bafis, 350. Of the effe<5t of an immerfion of cotton into the aluminous mordant and lime-water, 354. Of the efficacy of Myroba- lan's, Aleppo galls, and American fumach, in en- abling cotton to decompofe and imbibe alumine more copioufly, ibid. Of the ufe of a folution of foap with barilla, and of certain other mixtures for improving the Quercitron yellow, 356. The method of (eparating alumine from fulpiiuric acid, 357. Remarks on certain properties of alumine, 357- xxviii CONTENTS. 357. Experiments with alumine when undifFolved, and when diffolved by pot-afh and foda, 358. Alfo with nitrate and muriate of alumine, 3,61. Of an orange colour dyed upon cotton by madder with Quercitron bark, ibid. Of greens dyed on linen and cotton, ibid. Effects of lime, magnefia, and filicious earth in dying with the bark upon linen and cotton, 362. Effects of different prepara- tions of tin, ibid. Effects of zinc, bifmuth, cop- per, lead, manganefe, arfenic, gold, platina, cobalt, nickle, and iron, varioufly combined as mordants or bafes in general dying with bark, 363 — 369. Of the application of Quercitron bark in topical dy- ing or callicQ printing, 3C9. Of the application of mordants, and the removal of their fuperfluous parts by cleaning, &c. ibid. Of the colours ob- tained from the bark by means of different mor- dants in callico printing, 372. Of the disadvantages of ufing brazil wood tor colouring mordants, ibid. Cautions concerning the depth of colour and con- fiftencytobe given to mordants, 373. Of a method of neutralizing the fulphuric acid remaining in the aluminous mordant, 376. Neceffity of thoroughly performing the cleanfing operation, 377. Advan- tages of increafing the warmth very gradually in dying with Quercitron bark on an aluminous bafis, 378. Methods of dying all the different fhades of yellow topically, 380. Ways by which the un- printed parts in callico printing may be preferved from ftains by tartar, &c. 381. Bad effects of ufing weld along with Quercitron bark, 382. Means of dying yellows, dove, olive, and drab colours topically, from the Quercitron bark, 383. Of the ufe of fumach with the bark, and its effi- cacy in keeping the unprinted parts free from ftain, 385. Of a plant cailed D'howah, ufed in Bengal for the like purpofe, 386. Acid berries of the common Pennfylvanian fumach produce a fimilar effect, 387. Method of employing the Quercitron bark for printed velverets, &c. 388. Definition of the term projub/iantive topical colour, 390. Manner of preparing a profubftantive yellow (No. 10 1.) CONTENTS. xxix I.) from the Quercitron bark, for {raining linen and cotton, 391. Method of raifing this yellow, as well as of increafing its durability, 395. Of another profubftantive yellow colour (No. 2.), 396. Of a profubftantive yellowiih green (No. 3.), 397., Of a profubftantive yellow with a murio-fulphate of tin, 398. Cautions refpe&ing its application on the madder blacks or purples, 399. Of a profubftan- tive yellow with the nitro-muriate of tin, ibid. Ef- ficacy of the citric acid in preventing this yellow from becoming brown, ibid. Effects of other folu- tions of tin as profubftantive yellows, ibid. Of a profubftantive green produced by combining the colouring matters of Quercitron bark and logwood, 401. Means of obtaining profubftantive drab and olive colours from Quercitron bark with dif- ferent folutions of iron, 402. Of the effects or colours produced by the bark with folutions of zinc, mercury, platina, filver, lead, bifmuth, and anti- mony, ibid. Concluding obfervations refpecling the Quercitron bark, 404. CHAP. XIU. Of the Properties and Ufes of Juglans Alba or American Hiccory ; of the Weld Plant t Fuftic, and other Vegetables, affording Yellow Adjec- tive Colouring Matters. Parts of the American hiccory yielding colour; in what refpecls it is inferior to the Quercitron bark ; and in what fome of the varieties of it are fuperior, 406. Its general properties and ufes, 407. Of the weld plant, and its ufes, ibid. Inconveniences attending the cultivation and ufe of the weld, 408. Of the green and yellow dyes from weld, for which Dr. Richard Williams obtained a parliamentary reward, 410. Of the rhus cotinus, or young fuftic, 411. Of the morus tincloria, or old fuftic, and its ufes, ibid. Origin of the names, Old and Young Fuftic, 412. XXX CONTENT?. 412. Of the green ebony, 414. Of the Sparrifli fumach, rhus coriaria Linn. ibid. Of the French berries, the ufe of which ought to be profcribed ibid. Of the faw wort, dyer's broom, and heaths growing on this ifland, 415. Of the colours ob- tained from the Lombardy poplar, and from the leaves of the fweet willow, 416. Of the American golden rod, or folidago canadenfis Linn. ibid. Of the three- leaved hellebore, &c. 417. APPENDIX, CONTAINING, I ft. The abflradl of a corrected and enlarged bota- nical defcription of a new fpecies of nerium^ (rofe bay,) the leaves of which yield excellent indigo; with a defcription of the neceflary apparatus and procefs for manufacturing the indigo : to which is now added a fecond part, containing a brief ac- count of the refults of various experiments, made with a view to throw fome additional light on the theory of that beautiful production ; with an appen- dix containing a botanical defcription, &c. of a fecond new indigo plant, addrefled to Sir Charles Oakley, Bart. Governor, &c. at Madras, to be by him tranfmitted to the Hon. Court of Directors of the Eaft India Company, &c. by Dr. William Rox- burgh, 420 — 446. Remarks on Dr. Roxburgh's experiments and opinions, 447, &c. 2d. An account of another fuppofed green indigo from Bengal, and of experiments made by the Author to afcertain its nature and properties, 450 — ASS' 3d. Some mention of a fubftantive yellow from turme- ric employed in ilaining filk, 456. ---r-r-OrKvv*' • * I xx xi ~] INTRODUCTION. THE Great Author of Nature having al- lotted aid employed colours, as means of diftinguifhing and adorning the various pro- ductions of his power, wifdom, and goodnefs, has alfo endowed fome animals, and particularly man, not only with perceptions of the differences of colours, but alfo of the beauty arifing from them and their various combinations : and it is in confequence of thefe perceptions that man- kind, even in the rudeft ftates of human exift- ence, have been found to manifeft great admira- tion and defire for ornaments depending on gaudy and varied colours j which, at firft, naked lavages generally applied to their fkins, and afterwards to their garments, when they had approached fo far towards civilization as to ma- nufacture and wear cloathing. To thefe mo- tives, and to the rude trials induced by them, even in remote ages, the arts of dying and cal- lico printing undoubtedly owe their origin. It will appear in the following chapters, that colouring matters are of two very diftinct clafles; one which requires no bafis or mordant to fix it upon other objects, and which I have therefore denominated Jubfiantive colouring matter; and the other, whofe durability depends chiefly, if not wholly, upon the interpofition of fome bafis, and xxxn INTRODUCTION*. \ and which, for that reafon, I have called adjec- tive colouring matter j and as, among colouring matters, thofe of the adjective clafs would natu- rally preftnt themfelves in the greateft abund- ance, and be applied without any means to ren- der them permanent, (becaufe it would require numerous, trials, and a concurrence of many fortunate accidents to difcover the ufe of any bafis or mordant,) we may reafonably conclude, that mod of the ftains or dyes firft applied to different fubftances would in all countries have been fugitive. Such, according to Pliny, were thofe of the Gauls*, and fuch have been the greateft part of thofe employed by the uncivil- ized inhabitants of all the newly-difcovered countries : and we may therefore confider the difcovery of the effects of bafes or mordants, and particularly of alum, in fixing adjective colour- ing matters, as a moll important event in the hiftory of dying. When or where this difcovery was firft made cannot be afcertained ; there is, however, good reafon to believe, that alum, and probably iron, (which are the principal bafes of modern callico printing,) were employed by the Egyptians in producing thofe effects which are defcribed by Pliny, L. xxxv. § 42 ■, becaufe * { ' 1'ranfalpina Gallia berbis Tyrium atque conchilium tingit, cmnefque alios colores—Sed culpa non ahlui ii/ii." Lib. xxii. § 3. This however was not always the cafe in other countries : Herodotus mentions a people living on the borders of the Caipian fea, who by bruifing the leaves of a particular tree, and mixing them with water, obtained a colour by which they afterwards painted or Itained their garments with the figures of animals, &c. which figures, he adds, water could not efface ; on the contrary, they remained until the cloth was worn out, as if they had been woven therein. Book Clio. c. c. iii. they INTRODUCTION. xxxiii they refemble others which callico printers now obtain by thefe means, and which at this time they cannot obtain by any other, even with all the knowledge fince acquired : and, in the feventh chapter of this volume, fads and reafons are ad- duced, to prove that the Egyptians borrowed this art from Hindoftan, where it appears to have fubfifted for more than two thoufand years, probably with very little if any variation or improvement during that long fpace of time: and if we may judge of the means formerly em- ployed in Hindoftan for dying or ftaining cal- licoes by thofe which were found to be in ufe for that purpofe, when the nations of Europe firft went thither by the Cape of Good Hope, we may fafely conclude, that folutions of alum and of iron muft have been the mordants em- ployed in fixing their adjective colours. Hin- doftan appears alfo to have been the country where that wonderful fubftantive colouring mat- ter called indico, or indigo, was firft produced. The uncivilized inhabitants of other countries indeed have found out ways of obtaining fub- ftantive blue colouring matters., very nearly re- fembling that of indigo, from different plants, particularly from the ifatis tinctoria Linn., or woad, and from the genipa Americana Linn., but they obtained thefe matters in a liquid form only. The people of India however went farther; they precipitated and collected in a dry folid form the colouring matter of indigo, and, what muft have been a matter of much greater difficulty, they afterwards difcovered the means of diffolving it, and rendering it capable of being permanently fixed upon the fubftances intended to be ftained or dyed with it j an effect which the Greeks and b Romans »£&! *xxiv INTRODUCTION. Romans do not appear to have ever produced, though they knew how to powder and apply indigo as a paint. From the fifth volume of that extenfive Work intituled, u Membires concernants l'Hiftoire, les Sciences, les Arts, les Moeurs, &c. des Chinois," it appears that wool was never worn in China but as a fubftitute for fur, and that cotton and filk, be- ing the only fubftances ever dyed by the inha- bitants, received all their colours from vegeta- ble tingent matters ; that thefe colours were principally red, blue, violet, and what is called a woad colour ; and that under the three firft dynafties, the bufinefs of dying was chiefly prac- tifed by the female part of each family, for its own particular ufe : and it probably continued to be practifed without any thing like principle or fcience until near the end of the feventh cen- tury, when the Chinefe, difcarding their own, borrowed the art and means of dying which were then in ufe among the Indians and Perfians : and it is faid, that alum and copperas, which the Chinefe did not ufe before, were among the means fo borrowed ; a fact which renders it pro* bable that there was little, if any thing, in the Chinefe art of dying, of which the iofs need now be regretted. It appears however that, long before this time, a knowledge of the ufes of alum and of iron in dying, had fpread from Hindoftan and Perfia weftward to Egypt, and thence to Greece and Rome. Bergmann indeed, (de Confect. Alum,) and after him Eeckmann, (in the Gottingen Memoirs,) have reprefented the alum of the antients ^^^^_ ~-ZT~'s~ INTRODUCTION. XXXV antients as different from the cryftallized fait fo called by the moderns 5 and have fuppofed, that the varieties of alum mentioned by Diofcorides were ftalactites, containing but little alum, and confiding chiefly of calcareous earth, which, in certain proportions, will hereafter appear to be a very ufeful addition for moft of the colours depending on an aluminous bafis. Nature how- ever does produce fome, though but little cry- ftallized alum, particularly in Egypt and fome parts of Afia ; and it probably was in this ftate that its good effects in dying had been firft ob- ferved, before mankind were led to the means and operations fince employed for feparating and collecting it from the various aluminous ores. Bergmann fays, that " the factitious fak which " is now called alum, was firft difcovered in <{ the Eaftern countries;" and that "among '• the moft early works eftablifhed for the pre- ft paration of alum, we may juftly number that <£ of Rocchoy a city in Syria, now called Edeffa : " hence the appellation of roch alum." See vol. I. p. 239- °f tne Englifh Tranfiation of his Effays. He adds, that " Bartholomew Perdix " or Pernix, a merchant of Genoa, who had tf been at Roccho, difcovered the matrix of <{ alum in the ifland of Ifchia, about the year are nothing but a difpofition to reflect this or that fort of rays, more copioufty than the reft ; in the rays, they are nothing but their difpofitions to propa- gate this or that motion into the fenforium j and in the fenforium, they are fenfations of thofe mo- tions, under the forms of colours.'* That " colours may be produced by compo- fition, which fhall be like to the colours of ho- mogeneal light as to the appearance of colour, but not as to the immutabilitv of colour and conftitution of light ; and thofe colours, by how much they are more compounded, by fo much are they lefs full and intenfe ; and by too much compofition they may be diluted and weakened, till they ceafe, and the mixture becomes grey. There may be alfo colours produced by com- pofition, which are not fully like any of the co- lours of homogeneal light." " For a mixture of PERMANENT COLOURS, &c. 3 of homogeneal red and yellow compounds an orange, like, in appearance of colour, to that orange which, in the feries of unmixed prifmatic colours, lies between them; but the light of one orange is homogeneal as to the refrangibility, and that of the other is heterogeneal j and the colour of the one, if viewed through a prifm, remains unchanged ; that of the other is changed, and refolved into its component colours, red and yellow. And after the fame manner other neigh- bouring homogeneal colours may compound new colours, &x." And if to a colour fo com- pounded other colours be added in fufficient quantities, they will gradually overcome the firft, and produce " whitenefs, or fome other colour." " So if to the colour of any homo- geneal light, the fun's white light, compofed of all forts of rays, be added, that colour will not vanifh or change its fpecies, but be diluted ; and by adding more and more white, it will be di- luted more and more perpetually." " Laftly, if red and violet be mingled, there will be gene- rated, according to their various proportions, various purples, fuch as are not like, in appear- ance, to the colour of any homogeneal light ; and of thefe purples, mixed with yellow and blue, may be made other new colours." " That whitenefs, and all grey colours between white and black, may be compounded of colours, and the whitenefs of the fun's light, is compounded of all the primary colours mixed in due pro- portion." To illuftrate this, he produced white- fiefs, firit by a mixture of the prifmatic colours, and then by mixtures of differently coloured fubftances, in due proportions. B 2 Each HF!^ : I 4 PHILOSOPHY OF Each particular colour being therefore a pro- perty of that particular fort of ray which pro- duces the perception thereof. Sir Ifaac Newton concludes, that the permanent colours of natu- ral bodies arife from hence, that fome of them " reflect fome forts of rays, others other forts, more copioufly than the reft." " Minium re- flects the leaft refrangible, or red making rays moil copioufly, and thence appears red. Violets reflect the moft refrangible moil copioufly, and thence have their colour, and fo of other bo- dies i" and ct whiift bodies become coloured, by reflecting or tranfmitting this or that fort of rays more copioufly than the reft, it is to be con- ceived that they flop and ftifle in themfelves the rays which they do not reflect." Sir Ifaac Newton's demonftrations and illuftra- tions of this doctrine may be feen at large in the firft Book of his Optics, to which I beg leave to refer, without preiuming to offer the fmalleft objection thereto. The celebrated Euler has, indeed, conceived light to be propagated like found, by a vibrating motion, and that the dif- ferent degrees of velocity, or frequency with which thele motions or vibrations fucceffively reach the organs of vifion, occaflon the fenfa- tions or perceptions of the different 1 colours, as thofe of air occaflon the differences of found, and that colours are to the fight, what founds are to the organs of hearing. But this analogy, though it may ferve to illuftrate, will not prove the truth of his opinion ; and as he does not offer any other fatisfactory proof of it, or any means to overcome the difficulties with which it is at- tended. I fliall thus far adhere to Sir Ifaac New- ton's PERMANENT COLOURS, &c. e ton's doctrine. His fecond Book, however, appears to contain matter which is liable to con- fiderable objection. He begins it with " Ob- fervations concerning the reflections, refractions, and colours of thin tranfparent bodies •" and mentions what had been oblerved by others, cc that tranfparent fubftances, as glafs, water, air, &c. when made very thin by being blown into bubbles, or otherwife formed into plates, do exhibit various colours, according to their various thinnefs j although at a greater thick - nefs they appear very clear and colourlefs." And though he confiders thefe colours as " of a more difficult conjideration," yet as «« they may con- duce to farther difcoveries for completing the theory of light, especially as to the conftitution of the ■parts of natural bodies •, on which their co- lours or transparency depend" he delivers his own obfervations on this fubject : Of thefe, the principal was made, by taking tc two object glades, the one a planoconvex, for a fourteen foot telefcope, and the other a large double convex, for one of about fifty foot ; and upon this, laying the other with its plane fide down- wards, I prefled them (lowly together, fays he, to make the colours fucceflively emerge in the middle of the circles, and then (lowly lifted the upper glafs from the lower, to make them fuc- ceflively vanifli again in the fame place. The colour which, by prefling the glades together, emerged lad, in the middle of the other colours would, upon its firfl: appearance, look like a circle of a colour, almoit uniform from the cir- cumference to the center ; and by comprefllng the glafles dill more, grow continually broader, until a new colour emerged in its center, and B 3 thereby 6 PHILOSOPHY OV thereby it became a ring, encompafling that new colour j and by cotnprefling the glaftes ftill morej the diameter of this ring would increafe, and the breadth of its orbit, or perimeter, de- creafe, until another new colour emerged in the center of the laft j and fo on, until a third, a fourth, a fifth, and other following new colours fucceflively emerged there, and became rings, encompafling the innermoft colour ; the laft of which was the black fpot : And on the contrary, by lifting up the upper glafs from the lower, the diameter of the rings would decreafe, and the breadth of their orbit increafe, until their co- lours reached fucceflively to the center ; and then they being of a considerable breadth, I could more ealily difcern and diftinguiih their fpecies than before." And thefe he found to be in fucceflion from the black central fpot as fol- lows, viz. fir ft, blue, white, yellow, and red j then in the next circuit or ov.ier immediately encompafling thcfe, were violet, blue, green, yellow, and red -, in the third circuit or order were purple, blue, green, yellow, and red ; after this fucceeded in the fourth circuit green and red ; then the fifth of greenifh blue and red ; next, the fixth, of greenifh blue and pale red j and laftly, the feventh, of greenifh blue and reddifh white : but the colours in the laft three circuits he defcribes as having been very indiftincl, and ending in perfect whitenefs. " By looking through the two object gUffes," continues he, " I found that the interjacent air exhibited rings of colours, as well by tranfmit- ting light, as by reflecting it. The central fpot was now white, and from it the orders of the colours PERMANENT COLOURS, &c. 7 colours were yellowifh red ; black, violet, blue, white, yellow red j violet, blue, green, yellow, red, &c. But thefe colours were very faint and dilute, unlefs when the light was trajected very obliquely through the glaffes. Comparing the coloured rings made by reflexion, with thofe made by the tranfmifiion of light, I found/' adds he, inflammable matter. But were this extravagant fuppofition to be admitted as a caufe of the changes of co- lour in metals, how can it be reconciled to any hypothefis which makes their colours depend on their refpe&ive denfities ? Indeed, if the effects which Sir Ifaac Newton fuppofes phlogifton to have on colours were real, and if phlogifton really exifted in them, as both he and Mr. De- laval, as well as others, have until lately ima- gined, it would be difficult to conceive why all metals are not red,, or more inclined to rednefs, than their calces or oxyds. But enough, per- haps too much, has been faid, to refute Mr. Delaval's hypothefis, fo far as it relates to the colours of metals. Unfortunately, however, for my readers, as well as for myfelf, he has thought proper, in a larger work*, publifhed ibme time fince, to extend the fame hypothefis to the colours of animal and vegetable lubftan- ces ; and endeavour to confirm and illuftrate Sir Ifaac Newton's ideas on this fubjecl:, by a variety of experiments, which are reprefented as in- ftances of changes of colour produced in thefe lubftances, by an increafe or diminution in the 4 Experimental Enquiry into the Caufc of the permanent Colours of opake Boiks. 410. fizes, PERMANENT COLOURS, &c. 19 fizes of their particles : I am, therefore, com- pelled reluctantly to extend my own obferva- tions a little farther on this matter ; and I muft begin by complaining of a continuance of gratuitous and fallacious fuppoftions, fimilar to thofe which I have before had occafion to no- tice; for when, in operating upon, or with dif- ferent matters, he profeffes either to increafe or diminifh the fizes of their particles, and to do no- thing more, in order to fhew that the changes of colour produced in them, accord with the thick- neffes exprefTed by Sir Ifaac Newton, in the table which I have already mentioned ; inftead of choofing and employing mechanical means, which alone are fuited to produce thofe effects, and only thofe effects, he has recourfe to mere chymical agents, whofe actions in the ways which he fuppofes muft have beenftmoft always doubtful, though their powers of producing other, and very different effects from what he fuppofes, is mod certain. Mr. Delaval, however, adopting Sir Ifaac Newton's fuppofition, that acids always attenuate, and alkalies always in- craffate, prepared what he confidered as a dif- folving or attenuating liquor ; which " confid- ed of water, with about an eightieth part of aquafortis:" and when he wanted^o leffen the diflblving force of this liquor, inftead of weaken- ing it by the addition of water (which would certainly have been the moft obvious and unex- ceptionable expedient), he chofe to do it, as he lays, by adding « a fmall quantity of a folution of potam, or fome other alkaline liquor ;" and thereby produced a new compofuion, the effects of which muft, in many cafes, prove different from thofe of a mere diminution of the fuppofed C z diffolving 20 PHILOSOPHY OF diiiblving power of the former liquor. And on the other hand, when he wanted to increafe the force of his acid liquor, inftead of doing it by a farther addition of aqua fortis (obvioufly the mqft proper expedient), he recurs to an addi- tion of oil of vitriol i an acid poffeffing very different properties, and producing very different effects, on a great variety of fubflances, and particularly on colouring matters ; of which I could eafily allege hundreds of inftances, but ihall content myfelf with only mentioning what is well known, that even the ftrongeft and mod concentrated oil of vitriol (ufed to diffolve indigo for dying the Saxon blue, &c.) does not deftroy, or even weaken, its blue colour, though a very weak nitrous acid, or aqua fortis, will wholly deftroy it, and convert the indigo to a dirty brown mafs, %{ no ufe whatever. Having thus affumed, that acids attenuate., and do nothing but attenuate, the particles of colouring matter; that alkalies incraffate, and do nothing but incraffate, the fame particles $ that by adding an alkali to his mixture of aqua fortis and water, he weakens, and only weakens, its attenuating force on one hand; and that on the other he increafes, and only increafes it, by an addition of vitriolic acid ; he next provides himfelf with fo much of Sir Ifaac Newton's table before mentioned as fuits his purpofe, by tranfcribing the different colours of the three firlt orders, and the different thickneffes of air, water, and glafs, fuppofed to produce each of thefe colours, one after the other; and thus equipped, he proceeds to make experiments upon red infufions of certain vegetables, and generally PERMANENT COLOURS, &c. 21 generally finds, that with his acid liquor (i. e. water with T V °f ac i ua fortis) the colour con- tinues red i that, with the addition of oil of vitriol, to attenuate farther, as he fuppofes, it becomes yellow j and that if, inftead of oil of vitriol, he adds an alkali, to incrajfate, it becomes a purple. Now it fo happens, that though all the other colours are repeated in more than one order, purple is marked but once in Sir Ifaac Newton's table, and then it is placed as the firft colour of what he terms the third order ; and if the red and yellow, from which the purple in queftion had proceeded, were fuppofed to be of the fame order (as might be expected), then the produc- tion of this purple ought, upon Mr. Delaval's theory, to refult not from incraflation, but from attenuation ; fince the particles of it are ftated as near one third lefs in iize, than the particles of the red, and near one fourth fmaller than thofe of the yellow, of the fame order : but fuch is the happy arrangement of this table, and of the feveral orders of colours, that, by fup- pofing the red in this inftance to be the red of the fecond order, he finds a purple below it in the third, with only one intervening colour, and a yellow at the fame dijlance above ; and thefe leaps not being very great, he reconciles the ap- pearances to the theory. Indeed, as the fecond, or middle order in the table, contains all the different colours, and as, excepting one, they are all repeated in the firft order, which is above; and alfo in the third, which is below; hardly any change of colour can happen, which may not be made to accord with Mr. Delaval's hypothefis, he being always allowed to fuppole each original or primitive colour to belong to C 3 that H 22 PHILOSOPHY OF that order which may be found mod convenient; though, in truth, the very admiffion of different orders or repetitions of the fame colours, pro- duced repeatedly by and at different thickneffes, or fizes, either of particles or plates of matter, is of itfelf a proof (as I have before obferved) that fuch colours do not depend on any particu- lar thicknefs of plates or fize of particles 5 . I am far from thinking that Mr. Delaval has always chofen the mod proper matters for fair experiments, or that the experiments themfelves, even on his own principles, were well calcu- lated to afcertain the truth. But fuch as they 5 When Mr. Delaval, on every occafion, allots each par- ticular colour to fome one order, exclusively of the relt, it would feem reafonable to expect, that he mould juflify this allotment by fomcthing belides his own convenience, and particularly that he mould prove that the red, for inftance, which he places in the fecond order, exceeds that of the firft order, in the denfity and fizc cf its particles, exactly in the fame proportion as 18' exceeds 9 ; and that the red which he places in the third order, exceeds that of the fecond exactly in the proportion of 29 to 18 ' : and that the other colours of the feveral orders differ from each other likewife, according to the proportions flated as neceffary for their production in the table which he has adopted from Sir Ifaac Newton. Before this divifion cf colours into orders, arid the hypothefis connected with it, can be admitted to have any other than an imaginary foundation, it ought to be proved, that all the known reds differ from each other in refpect to the denfities and fizes of their particles, exactly according to the before mentioned proportions ; and fo of the oranges, yellows, &c. fince, in every cafe, the flighteft deviation from the thicknefs or fize of particles ftated as eflfential to the production of a particular colour, ought to occafion the appearance of that colour which is next in the feries above or below. But nothing like this is any where attempted, nor is there any thing in nature acceffible to human obfervation, which could in any degree juftify the attempt. are> PERMANENT COLOURS, &c. 23 are, I can readily point out feveral, which, on his own improbable, or rather impoflible fup- pofitions of mechanical attenuation or incraffa- tion, and nothing elfe, from chymical agents, cannot be reconciled to his theory, even by the affiftance of Sir Ifaac Newton's convenient table. The green leaves of the anil and glaftrum, he fays, " being long fteeped in water, their parts are dijjolved into a blue fubftance, which is in- digo and woad." Now the truth is, that the blue arifing from thefe vegetables is not the re- fult of any dijfolution, but of an abforption of air during the fermentation which they undergo; and this colour does not manifeft itfelf until there is a beginning aggregation and concretion of its matter into larger particles, which becoming denfer, as well as larger, fink down to the bot- tom, leaving the water colourlefs. So that here the change from green to blue, is manifeftly ac- companied with an increafe both in the fize and denfity of the coloured particles, which is abfo- lutely incompatible with Mr. Delaval's hypo- thecs ; fince, according to the table in quei- tion, every change of colour from green to blue is the effect of a diminution, not an increafe, in the fize and denfity of its particles. When the indigo itfelf (formed into large dry mafifes) is to be diffolved for dying, by the combined action of tauftic alkalies, and of particular chymical at- tractions, or of vegetable ferments, the folution, though manifeftly attended with a divifion or diminution of the coloured particles (as well as a lofs of the air abforbed during the fir ft procefs) becomes green, contrary to the table and hy- pothecs in queftion ; and in this ftate it is ap- plied by the dyers to wool, and other fubftances, C 4 to 24 PHILOSOPHY OF to be dyed ; and thefe, when firft taken out and expoied to the air, appear green ; but by ab- forbing, and uniting with a portion of it, they immediately become blue, and in doing fo, the divided particles again concrete into larger ones, as mult be evident, among other proofs, from this, that the furface of the indigo liquor on which the air has an immediate action, is from that caufe always blue; and if we fkim off this blue matter from the furface (which is nothing but indigo) it will be found impoffible to make it enter the pores of any fubftance to be dyed, fo as to eye a colour therewith ; becaufe the par- ticles having regained, and recombined with their proper portion of pure air, or its bafis, and with each other, are no longer fufficiently di- vided and difTolved for that purpofe ; fo that in all thefe cafes, the matter of indigo becomes more denfe, and its particles la r g< r, in parting from green, to the more refrangible colour, blue; and the contrary, in palling from blue to the lefs refrangible colour, green. And this too is the cafe, .vhen the infuhons of rhubaib, tur- meric, &c. are made " to defcend (as he ex- prefTes it) from yellow to orange and red," " by the addition of an alkali," which, whatever he may imagine to the contrary, dijfolves thefe co- louring matters more powerfully than any acid. Similar objections occur in oppofition to the in- flances which Mr. Delaval alleges, refpecting " the changes of Colour which animal fubftances undergo." Among thefe, e.g. he obferves, that cows milk, boiled up with an alkali, changes from white to yellow orange and red; and, as ufual, he gratuitoufly fuppofes, that, in pro- ducing thefe changes, it acts by incrajfating or coagulating PERMANENT COLOURS, &c. 2j coagulating the milk ; though if, contrary to all probability, alkalies were able to do this, we have no reafon to conclude that fuch coagulation would render the milk either yellow, orangej or red, becaufe no fuch colours appear when it really is coagulated by acids, &c. as in the" mak- ing of curds and cheefe. But furely it cannot be neceflfary for me ferioufly to combat fuch chi- meras any longer. The common fenfe and experience of mankind, if fairly confulted, will condemn and revolt at the idea of making; the colours of bodies depend on their weight, or the fizes of their particles ; for it certainly never has been obferved that the heavier! fubftances were red, or the lighted: violet-colouied, or that bodies equally heavy were all of the fame co- lour. Different parcels of indigo, for inftance, vary confiderably as to fpecific gravity, without any variation of colour -, and therefore it mud be very eafy to find fome of thefe agreeing in that refpect exactly with the colouring matter of cochineal (carmine), which of all colours is the fartheft removed from that of indigo : and if Mr. Delaval mould allege, that, though agree- ing in weight, they differ as to the fize of their refpective particles, let him correct this differ- ence by the only means fuited to do it, without doing more ; I mean by fimple mechanical di- vifion, trituration, or grinding. Let this be employed upon either of the fubftances in quef- tion as long as he mall think proper, and let us then fee whether he can thereby render the colour of indigo red, or that of cochineal blue or violet. Let h.m alfo make a fimilar trial upon mineral ethiops and vermillion; the one black, and the other of a beautiful red colour, though ■fl 26 PHILOSOPHY OF though both are compofed of mercury and ful- phur j and both are, or may be eafily rendered of exactly the fame fpecific gravity, by a little alteration in the ordinary proportions of their conftituent parts. Should what I have faid on this fubject prove infufHcient to convince any one of my readers, I only beg that he will follow me, with a mind open to conviction, through the various in- stances, which, for other purpofcs, I fhall have occafion to ftate hereafter, of colours produced, or changed by means and in ways that are wholly irreconcileable to the theory in queflion, and I perfuade myfelf that his doubts and difficulties will be effectually removed, fo far as they may relate to the truth or fallacy of Mr. Delaval's hypothefis, of which I mean hereafter to be filent, becaufe I cannot, without pain, fupport even the appearance of contention. And indeed I feel it neceffary to apologize for having fo long detained my readers on this fubject : I have done it not only from a conviction of the truth of what I have written, but from the belief of its being expedient to refute an hypothefis, in- compatible with a confiderable part of what I am about to offer to the public; an hypothefis which the name and authority of Sir Ifaac New- ton had pre-eminently fanctioned ; which the learning and talents of Mr. Delaval had ren- dered plaufible ; and which even at prefent is, I believe, generally confidered as true, in this and other countries. Should there be found any feeming incivility towards Mr. Delaval, I hope it will be confidered as the unguarded effufion of a zeal for truth. Nothing is farther from my willies PERMANENT COLOURS, &c. 27 vvifhes than a perfonal contention with that Gen- tleman, though 1 have thought it necefTary to combat an error, capable of obstructing the pro- grefs of fcience. I have never had the honour of his acquaintance, but 1 have long reflected his character and abilities; and though I think he has erred, I alfo think it may be deemed a matter of excufe and confolation that he has only erred with Newton. Having, as I think, (hewn that the perma- nent colours of different objects do not arife from their denfities, or the fizes of their par- ticles, it becomes me to ftate fuch facts and ob- fervations as feem beft fuited to throw upon this obfeure and very intricate fubjecT:. light Sir Ifaac Newton having found that inflam- mable fubftances pofielTed greater refra<5tive powers than others, in proportion to their den- fities, fays, in his fecond Book of Optics, that " it feems rational to attribute the refrac- tive power of all bodies, chiefly, if not wholly, to the fulphureous parts with which they abound ; for, adds he, it is probable that all bodies abound more or lefs with fulphurs ;" a term by which he intended to diftinguiih inflammable matters generally. And this great man having alfo concluded that the permanent colours of natural bodies were analogous to the colours produced by the refractions of thin, colourlefs, tranfparent plates, &c. chymifls were generally induced to make all colour depend on the prin- ciple of inflammability or phlogifton, which, until very lately, was fuppofed to exift in metals and other fubftances, where there certainly is no evidence 2* PHILOSOPHY OF evidence or appearance of it ; and in thofe cafes where the total want of inflammability was ma- nifeft, they confounded this with the matter of heat and that of light j to both of which they afcribed the power of fhlogijiicating other fub- itances, and of thereby producing or changing their colours : a fpecies of confufion fuited only to cover and perpetuate ignorance j fince every fmgle colour is found to belong both to com- buftible and incombuftible fubftances, and to neither exclufively. The combujlible diamond, which Sir Ifaac Newton conjectured to be " an untluous Jubjiance coagulated," is found to be of almoft all the different colours, whilft other gems, though of fimilar colours, are all incom- buftible. Combuftible indigo, and incombustible fmak, are both blue ; combuftible vermillion and incombuftible minium are both red ; combuf- tible gamboge, orpiment, &c. are yellow; and \'o are certain incombuftible oxyds of lead, iron, and mercury. But fince the exiftence of phlo- gifton in metals, &c. has been denied by the pneumatic chymifts, they have in moft cafes attributed the origin and changes of colours to the application or combination of different airs or gazes, and particularly oxygene in different proportions ; and it has been fuppofed that thefe gazes porTeffed co n fid er able refraBive powers, and were thereby enabled to produce effects on colours like thofe which the followers of Stahl had imputed to phlogifton ; and Mr. Benhollet, in his recent work on the Elements of Dying, intimates, that " many important obfervations ftill remain for thofe who would follow the fleps of that great man (Sir Ifaac Newton), and compare the ref ratling powers of the PERMANENT COLOURS, Sec. 29 the different gazes, and other fubftances, the conftituent principles of which are now known." But from all that I can difcern of this intricate fubject, it feems to me, that, though the prifm, and other tranfparent colourlefs fubftances, in different forms, (hew us the different colours of the feveral rays of light, by Separating them from each other, in confequence of their greater or lefs refrangibility, or difpofition to be " turned out of their way, in palling out of one tranfparent body or medium into another,*' yet I am perfuaded that the permanent colours of different bodies, or fubftances, are not produced by mere refrattion, and that Sir Ifaac Newton was milled by analogy when he extended his difcoveries and conclusions refpecting the tran- fient colours refulting from the refractions of light by pellucid colourlefs fubftances, to the permanent colours of various kinds of matter; iince the latter evidently depend on other pro- perties, which determine, or occafion the reflec- tion or tranfmiffion of fome particular fort or forts of rays, and an abforption or difappear- ance of the reft ; and thefe I conceive to be cer- tain affinities, or elective attractions, exifting in or between the differently coloured matters and the particular forts or rays of light fo abforbed or made latent j and of which many inftances and proofs will, I think, be found in the fubfe- quent parts of this work. Next after the dia- mond and amber, we find that fpirit of turpen- tine, hntfeed oil, olive oil, camphor and a!co hoi, or rectified fpirit of wine, poffefs greatei refracting powers, in proportion to their refpec- tive denfities, than any of the other fubftances contained in Sir Ifaac Newton's table, and yec the/ 3^ PHILOSOPHY OF they are all permanently dejlitute of colour ; & fact which does not feem to indicate any con- nexion between the refractive power of a fub- ftance and its natural permanent colour. Nothing feems to act fo powerfully and extenfivcly in producing and changing thofe affinities, or elec- tive attractions, from which the permanent co- lours of different fubftances arife, as pure vital air, or its bafis, the oxygene ; which indeed feems to owe its elaftic, or aerial form, to a portion of light as well as heat. Scheele demonstrated that gold, filver, &c. were re- vived from their oxyds by the contact of light ; and Mr. Berthollet has proved, that, in pro- ducing this effe£t, the light occasions a feparation of oxygene, in the form of pure vital air. Light alfo, by giving elasticity to oxygene, feparates it from various other fubftances, to which it would otherwife remain united, under, perhaps, the greateft degrees of heat. A bottle filled with oxygenated muriatic acid, improperly called dephlogifticated marine acid, if it be expofed to the light, lets go its oxygene, and becomes com- mon muriatic acid, but if wrapped in black pa- per, and expofed to the fun, it fuffers no change j and if heated in the dark, it will fly off in the form of oxygenated muriatic gas, without any decompofition of its oxygene. We are at this time well acquainted with the constituent parts of the acid of nitre : it undeniably confifts of what the pneumatic chy- mifts term azote (phlogifticated or nitrous air), rendered acid by its combination with a cer- tain portion of oxygene, or the bafis of vital air. When the azote and the oxygene are com- bined PERMANENT COLOURS, & Ci 31 bined in a certain proportion, the acid or com- pound is colourlefs, as we fee it in aqua fortis, or nitric acid: but if this colourlefs acid, in a tranfparent glafs veffel, partly filled, be expofed to the rays of the fun, or the light of a fire, an alteration will take place in the proportion of its ingredients; fince the light will combine with a part of the oxygene, and caufe it to become elaflic and fly off, and the azote will confe- quently predominate in the remainder; which, merely in confequence of this predominance, will affjme firft a yellow, then an orange, and afterwards a high vivid aurora, and even a red colour, intenfeiy affeclmg the fight. But if the glafs veffel containing the colourlefs nitric acid, were filed with it, no fuch change of colour would take place by any degree of expofure to the fun's rays or other light ; becaufe, in this cafe, there would be no fufBcient fpace or room to allow of a feparation and efcape of the oxy- gene. When nitrous acid has been made to aiTume the colours as before mentioned, if the glafs veffel containing it be hermetically fealed and kept for fome time in the dark, the oxygene, by lofing its light, will lofe its elafticity; and being again reabforbed by the nitrous acid, the latter will become colourlefs, as before. Mr. Keir mentions an orange- coloured nitrous acid, which, by long keeping, became green, and afterwards of a deep blue ; and Bergman fays, that if, to a concentrated red nitrous acid, one fourth pert of the quantity or meafure of water be added, the colour will be changed to a fine green, or to a blue, by the addition of an equal meafure of water, and that double its quantity of water will deftroy the colour. Here then 1 1 we ^H 3* PHILOSOPHY OF we have an example of all the various colours produced by the two fpecies of air which com- pote our atmofphere (almoft wholly) when de- prived of their elafticity, and mixed in particu- lar proportions with more or lefs dilution by water. In the Tame manner, colourlefs nitric acid, when applied to wool, filk, fur, or the fkins of animals, their nails, horns, &c. renders them all not only yellow, but orange, and even aurora- coloured. Mr. Bercholiet thinks thefe changes are produced by a kind of combuftion ; but I am perfuaded they are the refult of a combination of the oxygene with the azote, which he has prov- ed to be a conftituent part of all animal fub- ftances; they being exactly fimilar both in their nature and origin, to the changes of colour pro- duced as before mentioned in the nitrous acid. "Were thefe colours the effect of combuftion, why are they not likewifc produced in the fame manner upon linens, cottons, and vegetable fubftances, which contain either little or no azote, but a great portion of the bafis of char- coal, and ought therefore to be more liable to be acted upon in the way of combuftion, than animal fubftances ? Long before the properties of the feveral kinds of air were known, many changes of co- lour had been noticed as produced by the appli- cation or action of light ; and indeed its effects are fo remarkable, in a multitude of cafes, that no one can doubt of its powerful agency in thefe and other refpects. The only thing to be alcer- taincd on this point is, whether the colours which PERMANENT COLOURS, &c. 33 which accompany or require the application of light, refult directly from a combination of it with the coloured fubltance, or indirectly from its particular action in occafioning a feparation of airs, or their bafes (and particularly of the oxygene), or by favouring a combination thereof with the coloured matter. Mr. de Luc maintains, that light enters mediately or imme- diately into the compofition of a confiderabie number of folids, and of all liquids and expan- fible fluids, particularly the triform; and it feems reafonable to conclude, that it mult greatly influence many phyfical and chymicai phenomena. That able chymifl Mr. Chaptal, found that the rays of light directed particularly upon certain parts of glaffes, containing folutions of different falts, caufed them to cryftallize upon thofe fides which were in contact with the light, and no other. Many fubftances abforb and retain large portions of light, as appears by their emitting it in the dark ; this is the cafe of the Bolognian itone, and of many other natural as well as artificial compofitions j among the latter, Mr. Canton's phofphorous (compofed chiefly of calcined oyfter fnells) imbibes and retains the light fo ftrongly, that, after being expoied to it for only a few feconds, it continues to be luminous even at the end of fix months. Almoft all animal and vegetable fubftances are found to emit light in certain ftages of putrefac- tion, or decompofition, and therefore it may be prefumed to have been previoufly combined with fome of their parts; but how it acts, or whether it acts at all immediately, in producing the colours of any object, feems yet uncertain -, though we know that it does contribute greatly D to 3| PHILOSOPHY OF to the production or change of colpurs in a mul- titude of mineral., vegetable, and animal fub- ltances; in fome cafes, by combining with the bafis of vital air (oxygene), and feparating, by rendering it elaftic ; and in others, by promoting the action and union thereof, upon or with par- ticular fubftances. It feems difficult to afcer- tain the particular affinities by which fcmetimes the one, and fometimes the other, of thefe effects is produced : perhaps they depend on caufes to which chymical knowledge, in its pre- fent imperfect (late, cannot reach. From the experiments of Beccari, Meyer, Schulze, Scheele, and Sennebier, it appears that muriate of filver (horned filver), which is nearly of a pearl white, changes to a violet co- lour, and from thence to a black, in the fpace of a very few minutes, when expofed to the fun's rays in a tranfparent glafs ; and this change Sennebier afcribes iblely to the action of light ; fince, as he maintains, the muriate of filver will invariably retain its whitenefs, though ex- pofed either to heat or cold ; and in a moift or a dry air, or in vacuo, if fecured from the ac- cefiion of light, and of what he calls phlogiftic vapours (probably fulphurated, hydrogenous gas), and that it lofes its whitenefs only by the application of" light, and then only in propor- tion to its quantity or intenfity ; fo that when the fun's rays are copioufly applied by a lens, the muriate of filver is rendered violet coloured in a fingle fecond. By covering the muriate of filver with four thickneffes of white paper, its whitenefs was preferved ; one, two, and three thickneffes retarded, but did not prevent its 2 finally PERMANENT COLOURS, &c. 3$ finally becoming violet and black. Mr. Sennebier Found that the different rays of light, under the fame circumftances, coloured the muriate of filver with different degrees of celerity j i.e. the violet rays in 15 feconds, the purple in 23 fe- conds, the blue in 29, the green in 37, the yellow in 5 minutes and 30 feconds, the orange in 12 minutes, and the red in 20 ; but the rays of the three laft colours would not, as he re- lates, produce fuch a dark violet colour in any length of time, as was thus quickly produced by the more refrangible rays. I have alfo wit- neffed mod of thefe, and fome other changes of colour, taking place in muriated or horned fil- ver, and which may, I think, be fatisfactorily explained, by confidering that this preparation is the oxyd or calx of that metal, united only to a very fmall portion fcf either oxygene or muriatic acid, which the light renders elaftic, and thereby feparates fuch a portion of it as to produce an incipient reduction or revival of the: metal, and with it the dark colours which filver always manifefts in that ftate; and in confirma- tion of this, I need only mention what I have feveral times obferved, that though muriated filver, placed at the bottom of a colourlefs glafs veffel, nearly filled with water, was made violet coloured in about two minutes, by the weak light of a room, having a fingle window only, and in a cloudy day j yet a direct application of the fun's rays for many days produced no change of colour, when the muriated filver was covered with muriatic acid inftead of water ; becaufe, in this cafe, nothing like a revival of the filver could take place, whilft fo much uncombined muriatic acid remained in contact with it, and D 2 ready • 36 PHILOSOPHY OF ready to fupply the place of any which might be feparated by the fun's rays. It is curious to obferve the different degrees of force and celerity with which, according to Sen- nebier, the different rays of light change the colour of horned filver, exaftly in proportion to their degrees of refrangibility j an effect which, muft be afcribed to a greater affinity between the leaft refrangible ray and the muriatic acid, in confequence of which the former more readily combine with and extricate or feparate -the latter from the filver to which it was united. A folution of filver in the nitric acid likewife changes colour by the action of light, and be- comes black thereby, as well as by the applica- tion of inflammable»fubftances, of calcareous earth (chalk), and every thing elfe which can feparate a fufficient portion of the oxygene. It alfo gives the fkin a black colour, which cannot be effaced, but by a removal or change of the fkin itfelf: it tinges the hair, nails, and other animal fubftances, in like manner, becaufe they occafion a feparation of fo much of the oxygene as is neceffary for that purpofe. Mercury diflblved in nitric acid, being waflied with water, affords a yellow oxyd, which, when expofed to the light in a tranfparent colourlefs ghfs veflel, will become black on the fide to which the light is applied, even where the veffel is filled with water ; becaufe, as in the cafe of horned filver, the light extricates a part of the oxygene ; this yellow oxyd being a preparation of mercury, with but a very fmall proportion of acid. t^M ^m i."iiC,>ii'i--vc.'^2: PERMANENT COLOURS, &c. 37 acid. The red precipitate, and feveral other preparations of mercury, have their colours changed even under water, by fimilar means. The white or colourlefs folution of mercury, by the nitric acid, when applied to animal and in- flammable fubftances, tinges them purple and black, in the fame way, and from the fame caufe, as they are tinged by the folution of filver. Similar effects happen with the folution and oxyd of bifmuth, which laft is therefore ufed to blacken hair when mixed with pomatum. Almoft all the other metals afford inftances of changes of co- lour more or lefs remarkable, depending upon the acceflion and feparation of oxygene ; and in many of which light has a confiderable influence in promoting one or other of thefe effects. In all the inftances lately mentioned, however, blacknefs was produced by a feparation of air from the metallic bafis ; but there are others in which it refults from the addition or acceflion thereof. Arfenic, as Mr. Chaptal mentions, when firfl fublimed, is of a fliining grey, or fteel colour, but blackens fpeedily in the air (" noir- cit promptement a l'air") ; and he likewife ob- ferves, that " manganefe, precipitated by an alkali from its folution, was found to be a whitifh gelatinous fubftance, which loon chang- ed colour, and became black, by the contact of air; that, having been a witnefs of this pheno- menon, he could only attribute it ro the abibrp- tion of oxygenous gas, and found this to be the caCe, by fhaking the white precipitate in glafles filled with that gas, by which the black manifested itfelf in one or two minutes, and a confiderable part of the gas was found to have been abforb- ed." Elemens de Chymie, torn, ii. p. 260.—* D 3 The 38 PHILOSOPHY OF The preceding inftances relate to mineral and inorganical fubftances, though in the two laft it muft be owned, that the influence of light (the immediate object of confideration) is not very evident j and therefore I fhall proceed to notice fome of the more remarkable effects of that ele- ment, in producing the colours of vegetable and animal fubftances, Ray> in his Hiftoria Planta- rum, printed in 1686, vol. i. p. 15. appears to have difcovered, by feveral experiments and obferva- tions, that the green colour of plants depended chiefly upon the influence of light : he had found that they were green, whilft vegetating under a tranfparent glafsbell expofed to the light, and that when growing in obfcurity under an opaque veiTel, they loft their green, and acquired a pale whitifh yellow i their flalks, at the fame time, becoming long, (lender, and feeble, and their leaves fmall. And thefe effects he afcribed to the want of light, rather than of either air or heat. " Nobis tamen non tarn aer quam lumen, luminifve actio colons in plantarum foliis viridis caufa efTe videtur. " — tf Ad hunc autem colorem inducen- dum non requiritur ccelor," &c. Mr. Bonnet has fince confirmed Ray's conclufions upon this fubject, and added feveral curious facts, refulting from a variety of experiments related in the fourth and fifth volumes of his works: but it is Mr. Sennebier who has done molt, and carried his inquiries fartheft refpecting it, as appears by his fr Memoires Phyfico Chymiques fur l'lnfluence de la Lurruere Solaire,"&:c. in 3 vols, 8yo. It is now well afcertained, that vegetables, growing in the light, give out the oxygenous gas (pure ■ PERMANENT COLOURS, &c. 39 (pure vital air) ; and Dr. Ingenhouz, by a great number of experiments, has proved, or con- ceives himfelf to have proved, that in the dark they give out the carbonic acid gas (fixed air) j though this has been doubted by others, and particularly by Mr. Sennebier, who conceives, that, in thefe cafes, it was the pure air vitiated by fome difeafe or decompofition of the plant itfelf : Dr. Ingenhouz, however, in his lad publication, adheres to his former opinion, and fupports it with new facts and arguments. Be this, however, right or wrong, there is no room to doubt but that healthy plants, growing in the light, decompofe both water and carbonic acid gas; and, appropriating to themfelves the hy- drogene, or inflammable air (which is a consti- tuent part of water), and the carbonaceous mat- ter, or bafis of the carbonic acid, with perhaps a fmall portion of the oxygene, they emit the reft in the form of vital air, which the light feems to feparate, by combining with and ren- dering it elaftic, in the fame manner as it fe- parates the oxygene from the calces or oxyds of metals, &c. But when plants vegetate in ob- fcurity, no fuch feparation can take place : in- deed the water imbibed by the plants feems not to be properly decompofed, unlefs its living powers be aided by the ftimulus of light, and by its affinity for the oxygene. There is, there- fore, an accumulation of this latter fubftance, and a want of inflammable air to compofe the refinous matter, by which the green colour of the plant is produced; and this colouring mat- ter being very fparingly formed, and at the fame time combined with an excefs of oxygene (which generally weakens or deftroys vegetable colours), the plant, inftead of its natural greennefs, exhi- D 4 bits ti:S"7:i.:: 40 PHILOSOPHY OF bits only a pale ftraw colour. Mr. Senncbier found that plants, in this (late, received a deeper green, and in lefs time, by expofure to the vio- let rays of light, than to thofe which were lefs refrangible; as was the cafe in colouring the muriate of filver. He alfo found that plants left to vegetate without light, under veflTels rilled either with azote (phlogifticated air), or with hydrogene (inflammable air), did not lofe their green colour, as when furrounded by com- mon atmofpheric air. In carbonic acid (fixed air) they foon periilied. Dr. Ingenhouz alfo obferved, that on mixing a little inflammable air with either the common or the vital air in which a plant was growing, under a tranfparenc glafs, the green colour of the plant foon became deeper. In thefe cafes there feems to have been an afpiration or abforption of the inflam- mable air, affording an increafe of the refmous colouring matter. Mr. Sennebier alfo found, that the red tinc- tures of orcanette *, fafflower, kermes, gum lac, and cochineal, were made yellow by expofure to the fun's rays j and the tincture of dragon's blood was thereby deprived of all colour : in thefe cafes the alcohol, or fpirits of wine, affifted the action of the fun's rays in decompofing the (cveral colouring matters, probably by combin- ing with their oxygene; becaufe it was found that the aqueous infuiions of orcanette, kermes, and cochineal, fuffered no change by the like expofure ; though indeed the infufions of faf- flower, dragon's blood, and gum lac, were changed by it-, perhaps becaufe they contain a Anchufa tinSloria. L I N . refinous PERMANENT COLOURS, &c. 4I refinous matter which might have co-operated with the rays of light, in the fame way as the fpirit of wine is fuppofed to have done. Mr. Sennebier obferved, that the petals of damafk rofes afforded a kind of brick colour to fpirits of wine, when put into it j and that this, by a few minutes expofure to the common light, became of a fine violet- colour j which, however was foon deftroyed, by a direct application of the fun's light, unlefs when a few drops of fome of the ftrong acids were added; in which' cafe, the colour withftood the fun's rays for feveral months. From thefe inftances I conclude, that the colour of the rofes depends on a certain proportion of oxygene; that the light, aided by the attraction which fpirits of wine, as well as other inflammable matters, have for oxygene, feparates it and de- ftroys the colour ; but that thefe effects are pre- vented, as might be expected, by the addition of acids containing and affording a fupply of oxygene. And that this was the fact, feems evident from this obfervation, made by Mr. Sennebier, that when the petals of the rofes had been rendered white by imparting their colour to the fpirit of wine, they regained it on bein^ taken out, and expofed to the air, even in a dark place ; though they did it much quicker m the light; but not at all in a veflel containing only azote, furrounded by quickfilver, even when aided by an immediate application of the fun's light; which clearly proves, that the refti- tution of oxygene was indiYpenfably neceffary to the reftitution of their colour. In the fame way fulphureous acid whitens rofes, bv abftracting and depriving them of their oxygene ; and the iulphunc acid reftores the colour, by reftoring 7 the 4* PHILOSOPHY OF the oxygene* 5 . Mr. Sennebier alfo found the red fkins of peaches to whiten in fpirits of wine, like the petals of rofes, and, like them, to re- gain their colour by expofure to the air ; as did alfo the red fkins of plumbs. He likewife ob- served, that the water-colours ufed by painters, if covered by a folution of fifh-glue or ifinglafs, and then varniihed, withftood the action of the fun's rays much longer than if varniihed without the fifh-glue; which laft feems to prevent the varnifh from co-operating with the light in ex- tricating the oxygene of the colouring matters, as, from its inflammable nature, it would do, if in immediate contact with them. The pre- ceding are examples of colours produced, chang- ed, or deftroyed by the action or affinity of light, exerted in feparating, by giving elafticity to, the oxygene or bafis of vital air. There are many other cafes, however, in which the affi- nity of light is very differently exerted, and in 6 The fulphureous or volatile vitriolic acid, not being faturated with oxygene, is difpofed to attract it from other matters in contact with it; and by fo doing, it not only whitens rofes, but filk, wool, and other fubftances, ren- dered yellow by being united to a certain portion of oxgene : and thefe fubftances, being fo whitened, may again be made yellow by the application of oxygenated muriatic acid, which will reltore to them that portion of cxygene of which they had been deprived. Hence it ap- pears, that the application of oxygene, which fo power- fully bleaches linen, is equally efficacious in producing a contrary effecl: on filk and wool; I mean that of destroying their whitenefs, and rendering them yellow. And thefe oppofite effedts arife from a difference in the fubftances ailed upon by the fame agent, the whitenefs of wool and filk evidently depending upon the abfence of oxygene, and that of linen and cotton upon its prefence ; perhaps upon their being completely faturated with it. which ,. ■ ^V J 4i ■ -* .•IM- PERMANENT COLOURS, &c. 43 which that element, inftead of decompofing the oxygene, and carrying it off* from particular matters, contributes rather to attract it, and pro- mote its combination with them, probably by uniting itfelf to the fame matters (in confe- quence of fome particular affinity), and forming, together with the oxygene, a triple compound. The green colour of the leaves of plants refides in a refinous fubftance, which being diffblved and extracted by fpirits of wine, produces a green tincture ; and Mr. Sennebier having ex- pofed this to the rays of the fun, in a clear tranfparent glafs, but half filled, he found, upon repeated trials, that the colour was generally deftroyed in about twenty minutes, and a yel-. lowifh fubftance was precipitated to the bottom; which I conceive to have been the colouring matter faturated with oxygene : but if the glafs was completely filled with the green tincture, and clofely (topped, Mr. Sennebier found, that the ftrongeft action of the fun's rays upon it, during four months, was not furHcient even to weaken in any degree the green colour, becaufe all oxygene was excluded, and the rays of light, without it, were unable to effect any change. Jf azote (phlogifticated air) was inclofed in a veflfel partly filled with this green tincture, the latter fuffered little or no change by long expo- fure to the direct action of the fun's light ; but if, inftead of this, he fubflituted pure vital air, the green colour was moft rapidly deftroyed. Mr. Sennebier alfo found, that the dark red juice of black cherries very foon loft irs colour, when ex* pofed to the fun's rays, but that a tincture of thofe cherries in fpirit of wine preferved its colour, in the fame circumftances ; the fpirit of wine, as J conceive, affording a covering and defence to the 44 PHILOSOPHY OF the colouring matter of the cherries againft the action and farther combination of oxygene or vital air. Here the effect was directly oppofite to that of rofes, lately mentioned. There are many other inftances of abforption of oxygene promoted by the action of light : many of thefe I mail have occafion to mention hereafter for other purpofes ; and therefore will content my- feif at prefent with noticing two experiments made by Mr. Berthollet. In the firft, he " in- verted, over mercury, a bottle half full of the green folution (employed by Mr. Sennebier), and expofed it to the light of the fun; when the colour was difcharged, the mercury was found to have rifen in the bottle, and confequently vital air had been abforbed; the oxygene having united with the colouring matter." In the fe- cond experiment, he "placed a tincture of turn- ibl, in contact with vital air, over mercury, both in the dark, and expofed to the light of the fun; the former continued unchanged for a con- fiderable length of time, and the vital air had fuffered no diminution ; but the other loft much of its colour, became red, and the air was in a, great meafure abforbed, &:c. In the fame manner that plants, firft fnooting out of the earth, are white, fo negro children, when firft born, are likewife of that colour, but by ex- pofure to light and air, they in a few days be- come black ; and as far as I can judge from what I have feen of the effect, it feems to refult from a combination of air, with a particular matter or bafis, compofing a part of the reticu- lar membrane under the fkin, and fitted by Na- ture to become black in this way, as that of the European is to remain whitej or that of the aborigines HHHH PERMANENT COLOURS, &c. 4 £ aborigines of North America to be brown, &c. The blacknefs of the negro children is found, by obfervation, to be confiderably haftened by early expofure to ftrong light, which feems to favour the abforption, or combination of oxy- gene j an effect which is not furprizing, fince, by many of Mr. Sennebier's experiments, the light was found to act in this way through coverings of greater thicknefs than thofe which oppofe its accefs to the reticular membrane in negroes. The action of light upon the human Euro- pean (kin, is alfo ltrongly manifefted by the production of tan and freckles ; of which the latter appear likewife to reach as far as the reti- cular membrane. Thefe effects are the mod remarkable in fea voyages, and other fituations where the light is copioufly reflected, efpecially by water, though without any increafe of heat. In like manner the hair of kittens, puppies, &c. though fitted by nature to become black, is, im- mediately after birth, only of a brownifh black colour, which gradually darkens externally, or as far as it is expofed to the air and lights but no farther j for 1 have found the blacked cats and dogs, even in old age, to have that part of their hair which is neareft the fkin, and mod fe- cluded from air, particularly towards its roots, only of a brownifh black colour, very different from what is feen at the ends or points. Mr. Sennebier mentions, upon the authority of Scheele, that the nereis 4acuftris is red whilft living in places acceffible to the fun's rays, and white when living in obfcurity. And M. Dorthes (fee Ann. de Chymie, torn, ii.) affirms, that 46 PHILOSOPHY OF that moft of the larvae of infects inhabiting the* interior cavities of animals, as well as of woods, fruit, the earth, &c. are white, and that having forced many of them to live under tranfparent glaffes, expofed to the light, their whitenefs was gradually changed for brown colours ; and that the tree frog, which generally lives in the (hade, being forced to live in a fituation expofed to the fun-fhine, changed his colour from ayellowifh, to a very dark green. In thefe laft inflances it does not appear certain whether the light produces the changes of colour which have been juft men- tioned, by occasioning an abstraction or an addi- tion of oxygene, but from what we know of its effects, in cafes apparently fimilar, we may at leaft conclude that it acts in one or the other of thefe ways. Tellow filk, according to Mr. Poivre's account, taken from the cocons and expofed to the fun, foon becomes perfectly white; and the fame happens to ivory, if ex- pofed in like manner, after it has become yellow, Thefe effects are fimilar to thofe which occur to white cotton garments, and to white lead paints, which notorioufly become yellow, if deprived of the free accefs of light and air for any length of time, but are again rendered white, by whatever reftores to them the oxygene which is wanting to maintain their whitenefs. I have now noticed the principal facts refpect- ing the action of light in producing or changing the colours of minerals, vegetables, and ani- mals ; and as far as our knowledge extends, it does not appear warrantable to conclude that light contributes to thefe effects, otherwife than by its affinity with oxygene, which, (affinity,) under fome circum- ■H PERMANENT COLOURS, kc. 47 circumftances, and with the aid perhaps of other unknown affinities, fometimes feparates and ren- ders the oxygene elaftic by uniting with it, and at other times occafions the combination of an increafed portion thereof with the coloured fub- ltance. This laft effect is what Mr. Berthollet feems exclufively to infift upon, as occafioning, either with or without the aid of light, all the changes and injuries to which animal and vege- table colouring matters are liable ; and he deems the action and effects of oxygene in thefe cafes to be fimilar to thofe of combuftion. fC In con- fidering the effects of air on colours (fays he), it is neceffary to make a diftinflion between thofe produced by metallic oxyds, and thofe produced by the colouring particles," meaning thofe of a vegetable nature ; the modifications of the for- mer are " entirely owing, continues he, to dif- ferent proportions of oxygene;" but I have been led by observation, he adds, " to form a differ- ent opinion of the latter," with which the oxy- genated muriatic acid had exhibited different phenomena, fometimes difcharging their co- lour, and producing whitenefs, but mod fre- quently rendering them yellow, fawn, or root- coloured, or brown or black, according to the intenfity of its action : and he remarks, that he had found, by comparifon, that when the colouring particles were rendered yellow, root-coloured, or brown, by the oxygenated muriatic acid, effects were produced fimilar to thofe of combuftion ; and that they were (i owing to the destruction of the hydrogene, which, as it combines with oxygene more eafily, and at a lower temperature than charcoal does, leaves the latter predomi- nant j fo that the natural colour of charcoal is more 48 PHILOSOPHY OF more or lefs blended with that which before ex- ifted 7 ;" And as " the light of the fun confi- derabiy accelerates the deftruction of colours," he concludes that it ought, if his theory be well founded, 7 MefT. Lavoifier, Berthollet, and other pneumatic chy- jnifts, feem to coniider the black colour of charcoal as natu- rally belonging to the vegetable maitcr from which it is formed, and not as the refult or effect of combuftion. To me, however, charcoal feems to be a kind of vegetable cxyd, confifting of the carbonaceous bafis, united to a cer- tain portion, of oxygene, enough to render this bafis black (as it occafions the blacknefs of manganefe)* but not enough to faturate and convert it into carbonic acid gas. Hard woods contain fo great a portion of the bafis of charcoal, that if it really exifted therein, with its black colour, previous to combuftion, it is impoflible to conceive how they fhould ever appear white, yellow, red, Sec. fince in dying, &c. we find, that laying other colours upon a black ground, only increafes the blacknefs. Neither do I think that this blacknefs is the only circumftance in which charcoal differs from its bafis, or the flate in which the ve- getable part thereof exifted previous to combuftion : en the contrary, I am perfuaded that its oxydation, or com- bination with oxygene, gives it new and very remarkable properties. Mr. Fourcroy has informed us (fee Ann. tie Chymie, torn, v.), that the aqueous extracts of feveral co- louring matters, by being left for a confiderable time ex- pofed to air, acquired and combined with a confiderable portion of oxygene, and thereby affumed new colours, and at the fame time became themfelves much more fixed and permanent than before; which feems to be the cafe (though in a greater degree) of the vegetable bafis of indigo and that of charcod. This laft is indeed never converted into charcoal, but by fuch a degree of heat as mufl neceffarily occafion its combination with oxygene (which never can be wanting, even in clofe vefiels, becaufe it exifts in the air veffels, and other parts of all vegetables) ; and when this converfion is made, the charcoal is rendered infinitely more indeftruttible than any other vegetable matter, as it will refift the combined aftion of fun, air, moifture, &c. for hundreds of years ; and indeed it can hardly be deftroyed but by fuch farther combuftion as will change it into carbo- nic PERMANENT COLOURS, &c. 49 founded, " to favour the combination of oxy- gene, and the combuftion thereby produced *." In thus afcribing the decays of vegetable and animal colouring matters in general to effects or changes fimilar to thofe of combuftiori) Mr. Ber- thollet, in my opinion, has gone much further than is warrantable by fads. It cannot, I am perfuaded, be his intention that we fhould apply the term of combuftion to alterations which re- fult from a fimple addition of oxygene, to con- touring matters, without a deftruftion or fepara- tion of any of their component parts ; though a great many of the decays and extinctions of thefe colours evidently arife only from fuch fimple addi- tions of oxygene. The nitric, fulphuric, and other acids containing oxygene, have the power not only of weakening, but of extinguifhing, for a time, the colours of many tingent matters -, not however by any effect which can properly be de* nominated a combuftion, but rather by a change in their feveral affinities or attractions, for par- ticular rays of light in preference to other rays j ttic acid gas. This indertructibility, as weli as the black colour of charcoal, feem therefore to refult from the combination of oxygene with its bafis. Were not this the cafe, and did it really exift with its black colour naturally in vegetables, why do we not find it remaining intire after the other parts of vegetables are feparated or deftroyed by fermentation, putrefaction, &c. ? and why does it diftolve and rot with them undiitirfljjuifhed, and contrary to what happens when it exitts feparately. in the form o.f charcoal ? and why, when in this form, will it not reconibine witli matters fimilar to thole feparated from it, and enter with them into fermentation, &c. as it furely ought to do if it had acquired no new property> and only been left in a dif» tincl form, by the fimple abllradtion of thofe mattrrs I * Elements of the Art of Dying, chap. iii. E but 50 PHILOSOPHY OF but none of their parts being deftroyed, or car- ried away, the addition of an alkali, or of cal- careous carbonate, will generally undo fuch al- teration, and reftore the original colour, by de- compofing and neutralizing the acid or oxygene which had caufed the alteration. Of this hun- dreds of inftances might be given, it being the cafe of almoft all vegetable or animal colouring matters j it will however be fufficient to mention, what mod people have feen, that ink, dropped into a glafs of diluted nitric, vitriolic, or other acid, will lofe its colour, and that it may be again reftored by adding a fuitable portion of vegetable or foftil alkali ; and that this may be done feveral times with the fame ink, and therefore the change, or lofs of colour, could not have been the effect of combuftion. If how- ever this ink had been fixed, by dying in the fubftance either of wool, filk, linen, or cotton, and the fubftance fo dyed had been dipped into a glafs of diluted acid, as before mentioned, a confiderable part of the colouring matter would have been diflodged, and feparated from the dyed fubfcance, by its affinity with the oxygene or acid ; and though no combuftion had taken place, the colour fo feparated and loft, could not be again reftored without a fecond dying : and this lofs of colour would be fimilar to what fre- quently happens to colours from expofure to fun and air, by which they are gradually weakened, many of them without any other change of tint than the fimple diminution of their original body, or quantity of colouring matter; and this continuing in the more fugitive colours, parti- cularly that of turmeric, the cloth is foon left as white as before it had been dyed, without any thing like combuftion having ever taken place in it, PERMANENT COLOURS, &c. 51 it, or in the matter with which it was dyed 8 . Mr. Sennebier expofed a great variety of woods to the action of the fun and air, and found all their colours very foon affected. The white woods were generally made brown, and the red and violet changed either to yellow or black. Guaiacum was rendered green ; the oak and the cedar were whitened, as were the brown woods generally ; effects which certainly do not re- femble thofe of combuftion, any more than the bleaching of wax and tallow byexpofure to air. The colour of each particular fubftance evi- dently depends on its peculiar conftitution, pro- ducing in it a particular affinity or attraction for certain rays of light, and a difpofition to reflect- or tranfmit certain other rays ; and in this refpect it may doubtlefs fuffer very confiderable 8 That colours are not generally impaired by any thing like combuftion, as Mr. Berthollct fuppofes, may be pre- fumed from this facl — that there are but few of them, which the common muriatic acid does not injure as much as either the nitric or the fulphuric ; and as there can be no combuftion without oxygene, and as the common muriatic acid either contains none (which is Mr. Berthollet's opinion), or what it does contain is confeffedly combined with it, by an affinity too powerful to be overcome by any known fub- ftance or means, it neceffarily follows, that the oxygene (if it contains any) cannot be liberated fo as to a& in the way of combuftion upon any other matter ; and therefore when the common muriatic acid changes or deftroys the colours in queftion, it changes or deftroys the affinities upon which they depend, by producing effects different from thofe of combuftion; and as the changes which it produces on co- lours are in moft cafes fimilar to thofe produced by ths nitric, fulphuric, and other acids known to contain oxy- gene, it feems reafonable to conclude that thefe alfo aft upon colours, by producing other eflecls than thofe of com* bullion. 1£ 2 changes 5 2 PHILOSOPHY OF changes from the a-5tion or combination of oxy- gene, without any effects fimilar to thofe of com- buftion. And indeed the changes of colour which arife from the accefs of vital or atmofphe- ric air, feldom refemble thofe which the mere predominence of blacknefs (the fuppofed natural colour of charcoal) would produce ; though this may have been the cafe with the colouring mat- ter of brown or unbleached linen, upon which Mr, Berthollet's experiments were principally made. But whether the action of vital air, or its bafis, in promoting the decays of colours, ought to be denominated a combuftion or not, I am confident that, at leaft, fome of them are liable to be impaired, not fo much by an acceflion of oxygene, as by the lofs of it ; an effect, of which I have already enumerated feveral examples, among animal and vegetable, as well as mineral fubftances, deriving their colours from a com- bination with certain portions of oxygene ; and to thefe I might add feveral other examples. Hook and Lower long fince noticed the dif- ference of colour in arterial and venal blood ; and it has been fince proved, by numerous ex- periments, that the fine vermilion colour of the foiincr, is produced folely by vital air, which it is capable of acquiring even through bladders, the coats of blood veffcls, &c. And very re- cently, Mr. Hafienfratz feems to have proved (fee Ann. de Chymic. torn, ix.), that as this fine red colour is gained by a difiblution of oxy- gene in the arterial blood, fo it is loft, and the dark colour of the venal blood reftored, by a feparation PERMANENT COLOURS, &c. 53 reparation of the oxygene, in confluence of its forming a new combination with the hydrogene and carbone thereof. That the blue colour of indigo abfolutely de- pends upon a certain portion of oxygene, has been already mentioned, and J !hall hereafter give fome curious Llluftrations of this fact, from which it will appear that a folution of indigo, by lofing its oxygene, may become as pellucid, and, excepting a very flight yellowifh tinge, as colourlefs as wate:, and afterwards fpeedily re- turn through all the fhades of yellow and green to its original deep blue, by expofure to atmo- fpheric or vital air. Similar to this is the fact long fince obferved by the Abbe Nollet, of the tincture of archil-orchella employed to colour the fpiritofwineufed in thermometers, and which after fome time lofes its colour, but loon recovers it again upon being expoied to atmofpheric air. And this alfo happens to the infufion of turnfol, and to fyrup of violets, which both lofe their colours when fecluded from air, and regain them when placed in contact with it. Many other ex- amples of the like effects might be mentioned here ; but to avoid repetitions, I beg leave to refer my readers to fubiequent parts of tiiis work, in which 1 {hall have occafion to inftance various animal and vegetable colours, produced, lblely by the contact of vital or atmofpheric air ; and fome others, which, when given by dying or callico printing to wool, filk, c >tton, &c. though unable to fuftain a tingle d fs expofure to the fun and air without manifctt injury, were found to receive none from the action of ftrung nitric or fulphuric acids, out, on the contrary, E 3 were « 54 • PHILOSOPHY OF were preferved by being wetted with them, and even with oxygenated muriatic, and fulphu- ric acids. But the fame colours, if covered with lintfeed oil, were found to decay more quickly from expofure to the fun and air, than if uncovered. Thefe colours therefore could not owe their decays to the contact, or combina- tion of oxygene, becaufe they were not only un- hurt, but benefited by its concentrated powers in the nitric, the oxygenated muriatic, and fulphuric acids ; and alfo becaufe they were fooneft impaired when defended from the accefs of oxygene, by being covered with lintfeed oil. Probably the decays of thefe colours were occa- fioned by a lofs of at lead forne part of the oxy- gene which was neceflary to their exifterice, and which the lintfeed oil affifted in depriving them of, by its known affinity with vital air. In forming fy (terns, we are apt to draw gene- ral conclufions from only a partial knowledge or view of facts. And this even Mr. Berthollet feems to have done, not only in afcribing the decays of vegetable and animal colours, exclu- fively to effects fimilar to ihofe of combuftion, but alfo in reprefenting the oxygenated muriatic acid as an accurate teit or meafure for anticipat- ing, in a few minutes, the changes which thefe colours are liable to fuffer, by long expofure to the action of fun and air ; for though it doubt- lefs is true that the oxygenated muriatic acid, in weakening or defLoying colours, gives up to them more or lefs of the oxygene, which it had received by diftillation from manganefe j and that, by this new combination of oxygene, thofe affinities for particular rays of light, upon which their PERMANENT COLOURS, &c. 55 their colours depend, are liable to be deftroyed j it is neverthelefs true, that the changes of co- lour fo produced are no certain indication of thofe which the combined influence of light and air will occafion upon colours in general ; there being, as I have already obferved, and as I (hall more fully explain hereafter, feveral colours which are very fpeedily deftroyed by the latter of thefe caufes, though they refift the ftrongeft action of the oxygenated muriatic acid, without any kind of injury. Mr. Bertholjet well knows, fince nobody has contributed more to afcertain, how much the properties of oxygene are diverfified by each particular bafis to which it unites; and it does not therefore feem warrantable to imagine that its action will not be modified by a bafis fo powerful as that of the common muriatic acid, or that the united properties of both fhould re- prefent or refemble thofe of atmofpheric air upon colours any more than they do in the lungs by refpiration, where, inftead of fupporting life, they would inftantly deftroy it. To afcertain, by well-directed experiments made upon each particular ingredient of the ma- teria tin&oria, in what ways, or by what changes, the colours of each are liable to be injured, would doubtlefs contribute moft effentially to- wards perfecting the art of dying; fince it would not only help us to difcover more clearly by what properties each is fitted to ablbrb or com- bine with particular rays of light, and reflect others, but alfo through what particular defects fome are more fugitive than others : and having E 4 mads : 5$ PHILOSOPHY OF made thefe difcoveries, we might probably ba led to the proper means of obviating or correct- ing fuch defects, fo as to render fugitive colours permanent, and improve thofe which are already confidered as fuch. Under this perfuafion I lately projected vari-. ous experiments upon the colours of different? dying drugs, calculated to afcertain the effects of light upon them, in vacuo, as well as when furrounded or covered by the feveral kinds of air, or by water, or alkohol, or the different acids, oils, or varniihes, both in warm and in frofty weather ; and alfo the effects of the like agents and circumftances upon the fame colours, placed in obfcurity; meaning, as far as might confift with the prefent ftate of chymical know- ledge, and the defects of our fenfes, inftruments and means when applied to fuch intricate and minute fubjects, to difcover what each colour had either loft or gained by the influence or con- tact of thefe feveral agents, and the changes of colour refulting in every inflance from fuch lofs or gain j and flattering myfelf with the hope of being able in thefe ways to contribute greatly towards improving the knowledge and philofo- phy of colours. But having been called abroad during that part of laft Summer .which was mod fuitabie to the greateft pare of thefe experiments, I have found it neceffary to defer moft of them to the next favourable fealon, when they will be undertaken and profecuted with as much care and expedition as may be compatible with my other unavoidable avocations ; and an account of their refults will be publifhed in fome of the iubfequent volumes of this work. The fubject is, PERMANENT COLOURS, &c. 57 is, however, diffidently extenfive and important to merit the attention and exercife the talents of abler philofophers, But until further difcoveries fhall have been made, we are only authorifed to conclude, that the permanent colours of natural bodies do not depend upon their thicknefles, fizes, or the denfi- ties of their feveral parts or particles, but upon certain affinities or attractions (chymical or phy- fical) by which they are difpofed to abforb and conceal fome of the rays of light, and to reflect or tranfmit other rays, giving the fenfations or perceptions of their refpective colours ; that the contact of light greatly contributes towards producing thefe affinities or attractions : but it only does this (as far as we yet know) either by promoting a combination or a ieparation of the bafis of vital air in the different coloured-or co- louring fubftances. But though mod of the changes of colour, in permanently coloured bo- dies, evidently depend on changes in their re- fpective portions of oxygene, 1 am far from thinking that this caufe operates exclufively in all cafes, or that chymical knowledge is yet far enough advanced to jullify even an attempt to- wards a complete hypothecs refpecting thefe jpoft abftrufe and molt interefting phasnomena. Should any one afk how oxygene acts in pro- ducing thefe affinities or attractions for particu- lar rays of light, I mall only anfwer with M. de Buffon, that they who require the reafon of a general effefl, do not confider either the infinite extent of Nature's operations, or the narrow limits of human underflanding. ■HHH 58 PHILOSOPHY OF CHAP. II. Of the Compojilion and Structure of the Fibres of Wool, Silk, Cotton, Linen, &c. " Ubi natura definit nobis incipiendum." T> EFORE I treat of the communication or ■*-* production of colours by dying or callico printing, it will be proper to inquire concerning the particular natures and differences of wool, hair, jfilk, cotton, linen, and hemp, upon which theie operations are ufually performed. The three ftfft are animal, the three lail vegetable fubftances, differing from each other in their constituent parts and chymical properties, as well as in ftructure and organization. Mr. Ber- thollet has done much towards afcertaining the chymical differences and properties of thefe mat- ters ; and the former has been found, by his ex- periments, to contain a large proportion of azote (of which the latter pofiefs but very little), and alfo a much larger proportion of hydrogene, than what belongs to vegetable matters ; and as the azote and hydrogene readily affume an elaf- tic form, the wool, hair, and filk, in which they abound, have lets adhelion between their conftituent parts, or molecules, than what exifts between thofe of cotton, linen, and hemp, and are therefore more ftrongly difpoied, than the latter, to combine with other fubftances, when brought into contact with them ; and it is probably in conference of this difpofition that wool, hair, and I ■ I ■ *£-<*». m vt i ■■■■ PERMANENT COLOURS, &c. 59 and filk, manifeft ftronger affinities or attrac- tions for colouring matters generally, *than cot- ton, linen, or hemp 1 . They are alfo more readily decompofed, or injured by acids, alka- lies, and other chymical agents, which ought therefore to be more fparingly ufed in the dying of animal, than of vegetable fubftances : it being found that the fulphuric, nitric, and even the muriatic acids decompofe wool, hair, and filk (by feparating either their azote or their hydrogene, or both in fome cafes), and at the fame time deftroy, or greatly weaken the texture and connexion of their feveral fibres ; and that alkalies prove equally injurious, by combining with them : though filk is indeed not fo liable to be a£ted upon in thefe ways, becaufe it partakes in fome degree of the vegetable nature. It is from the fuperior chymical affinities, or attractions exifting in wool, hair, and filk, for colouring matters, that the facilities with which thefe fubftances receive, and permanently retain colours, principally refill t ; though fomething is doubtlefs to be afcribed to the differences' of conformation exifting between their fibres and 1 e. g. Cotton and linen will neither of them receive any colour by the fame preparation, and in the fame liquor, which dyes wool or woollen cloth fcarlet. This is every day leen by the cotton edges of long ells, &c. which remain white after the reft of the cloth is become fcarlet. M. Dufay even caufed a piece of cloth to be manufactured, of which the chain was wool, and the woof cotton. This was afterwards fulled, that both might be brought into a fimilar ihte of preparation ; and the cloth being then dyed by the ufual procefs, the woollen threads contained in it received u good fcarlet, whilft the cotton remained white. thofe 6© PHILOSOPHY OF thofe of cotton, linen, and hemp, which I fhall notice under their feveral heads. And, I. Of Wool The value of this fubftance, and its fltnefs for the different kinds of manufacture, depend on the length and finenefs of its fibres j of which ample information may be found in a Memoir written by M. d'Aubenton, and printed among thofe of the Royal Academy of Sciences for the year 1779. The bufinefs of Spinning, and that of weaving, do not properly fall under my con- sideration ; but the operation of fulling deferves to be noticed, as being connected with circum- ftances which feem to have fome influence in the dying of wool and cloth. Fulling, according to Sir William Petty (See Spratt's Hiftory of the Royal Society), " is making the cloth to become thicker, with the diminution of its other dimen- fions, and the covering of its threads, fo as that the cloth fhall feem to be tranflated from the likenefs of a tela (all of whofe threads appear) to that of a hat which has no threads at all ; for, by the way, the making of a hat (continues he) is the making of a tela, without fpinning or weaving, by a kind of fulling." " This thick- ening/' adds he, "Is made by the fhortening of threads ; this fhortening of threads by twilting of them ; this twitting by the heat of the mill (for fuch effecT: vifibly hath heat on hair, &c.) ; this heat of the mill is excited rather by an un- equal motion, than by fire and fcalding water, as in hats; and the conftriftion is furthered by oatmeal, earth, and urine, which are lefe potent than PERMANENT COLOURS, k Ci 61 than the aftringent powders and liquors ufed about hats." M. Monge has, however, lately given a better account of operations of felting and fulling (fee Ann. de Chymie, torn. vi. p. 300, &c), by which it appears, that the f< Shortening of threads" is not the effect of heat, or of any aftringent power whatever, but an effect result- ing from the, external conformation of the fibres of wool, furr, &c. which appear to be formed, either of fmall lamina placed over each other, in a flanting direction, from the root towards the end or point of each fibre, like the fcalesof fifh, lying one over the other, in fucceflion, from the head to the tail ; or of zones, placed one upon another, as in the horns of animals j from which Structure each fibre, if drawn from its root towards the point, will pafs fmoothly through the fingers; but if it be drawn in a contrary direction, from the point towards the root, a fenfible refinance, and tremulous motion will be felt by the fingers. This conformation difpofes the fibres of wool to catch hold of each other, and as they cannot recede, when acted upon by other bodies, they naturally advance, by a progrefTive motion, towards, and befide each other, from the end towards the root ; a difpofition which is very inconvenient to fpin- ning, and therefore the wool is greaied, that the alperities arifing from this Structure of its fibres may be thereby covered, or Sheathed, as a co- vering of oil (heaths thofe of a fine file. But the wool being manufactured, and the greafe no longer ufeful, it is removed by fcoweiing, not only for the lake of cleanlinefs, but that it may not 62 PHILOSOPHY OF not fruftrate the procefs of dying. The cloth is therefore carried to the fulling mill, and there fubjeeted to the action of large beetles, with fullers earth and water, by which the cloth is not only fcowered, but its fibres, in confequence of the ftru&ure juft defcribed, being made to conjoin, and advance toward, and befide each other, become fhorter, and more clofely con- nected, or felted together, the warp and woof lofing in extent, but gaining proportionably in thicknefs. The lamina, or zones, under confideration, afford many interfaces in the fibres of wool, fuited to receive and contain the particles of co- louring matters, when applied to them in the operation of dying j but thefe interftices being fmall, and the fibres of the wool naturally elaf- tic, no colour can be conveyed into thefe cavi- ties, until they are diluted by hot or boiling water; whereas filk, cotton, and linen, are made to receive colours without heat, as per- manently as with it. And this difference mani- feftly arifes from the fmallnefs of the interftices in which the colouring particles are depofited in wool, and the elafticity of its fibres, which make it neceffary to dilate them by hot or boiling water; and as the colouring particles arc only made to enter and depofit them ft Ives by an artificial dilatation, it follows that, when this ceafes, the filaments will again contract to their former fize, upon the colouring matters fo introduced, and hold them much more ftrongly than they are likely to be held in other fub- ftances whofe interftices are large enough to re- ceive colouring particles without being dilated, 3 and mM m PERMANENT COLOURS, Sec. -63 and which, therefore, cannot be fuppofed ever to contract and compreis them in the fame way : and this difference, joined to the fuperiour chy- mical attraction of animal fibres for colouring matters, will fufficientiy explain why many co- lours dyed upon wool and hairs, prove fo much more durable than upon cotton or linen. Wool is naturally covered with a kind of oil, which would obftruct the procefs of dying, and is therefore to be removed, by what is called fcow- ering ; an operation fufficientiy known. "Wool, when dyed in the fleece, takes up much more colouring matter than when fpun, and much more than when wove into cloth. It is alio more or lefs penetrated, according to therinenefs of its own texture, and the particular nature of the colouring matter with which it is dyed. The very coarfe wool taken from the thighs and tails of lome rams and fheep, being never made to receive colours v/ithout difficulty ; and indeed the very fined cloth is never thoroughly dyed fcarlct, it being always found white within when cut. Wool taken from different breeds of fiieep, in various countries, is naturally of different co- lours ; as white, yellow, reddifh, and black. Formerly all the flocks in Spain, excepting thofe ofAndalufia, were of this laft colour, it having been preferred for wearing by the native Spani- ards ; and this natural brownifh black is even at this time manufactured, and worn conftantly by fome religious orders in Roman Catholic coun- tries. The white wool, however, is now almoft univerlally preferred to every other, as being fufceptible of receiving better colouis by dying, than 6 4 PHILOSOPHY OF than any of thofe which are natural. Manufac- tures of wool, though fuperfluous to man in a ftate of nature, feem to be, of all others, the moil important in civilized fociety. II. Of Silk The phalena, bombyx, or (ilk-worm, teems firft to have become an object of human care and attention in China, where it fubfifted natu- rally from the earlieft times. According to the annals of that country, the wife of the emperor Hoang-Ti firft occupied herfelf in collecting the cocons which were found on trees, and in wind- ing off their filk, which was afterwards brought into ufe. Another fpecies of this infect is alfo found in China (the phalena atlas of Linnreus); its co- cons are laid to be larger, and their filk much ftronger, than thofe of the other j but being dif- ficult to wind, it is commonly fpun. From China, filk was carried firft to Hirt- doftan, and afterwards to Perfiaj but it does not feem to have been known in Greece or Rome until about the time of Auguftus, when its nature and origin being but little un- derftood, very confufed ideas were entertained of it ; and during feveral ages it was fo fcarce, as only to be bought by, at leaft, its weight in gold ; and hence the emperor Aurelian, as is related, refufed the prefiing folicitations of the emprefs for a robe of filk, alleging that it would prove too coftly. In the year $$$y however, two monks came from India to Constantinople, 4 bringing ^B Y colouring matter, I underfland a fubftance -*-* which poffefies or acquires a power of acting upon the rays of light, fo as either to abforb them all, and produce the fenfation of black ; or only to abforb particular rays, and tranfmit or reflect the others, and thereby produce the per- ception of that particular colour which belongs tp the ray fo tranfmitted or reflected. Among minerals, the colouring matter of each is diftributed equally to all its parts ; but in animal and in vegetable fubftances, it generally exifts in particular parts, or particles which are capable of being extracted for the purpofes of dying, &c. Colouring matters poflefs peculiar chymical Droperties, which diftirtguiih them from all other kinds of matter ; for befides their feveral affinities with particular rays of light, they have others which render them fufceptible of being acted upon, and modified by a variety of chy- mical agents, as well as of forming permanent combinations with the filaments of wool, filk 3 cotton, ljnen, 6cc. But in refpect of thefe affi- nities^ ij,j;it::-«i -U- ■ ■Ji'^» * J*. ■ PERMANENT COLOURS, &c. 73 nities, colouring matters alfo differ effentially from each other, and muft therefore be applied in different ways, and with very different means, to produce permanent colours in other matters. The art of dying is founded upon a knowledge of the particular properties and affinities of thefe matters, not only as far as they relate to the fub- ftances intended to be dyed, but alio as far as they are connected with the operations of other agents, by which they are liable to be acted upon either during the procefs of dying, or afterwards. Many fpecies of animal and vegetable colour- ing matters fuffer nearly fimilar changes from the action of acids, alkalies, and other chymi- cal agents ; from which it may be prefumed, that there is fomething of a common or fimilar nature in the conftitution of many of them. But though it would be highly ufeful to eftablifh ge- neral principles and conclufions on this fubject, -we are not yet furniffied with the neceifary facts ; and whilft this continues to be the cafe, it will be beft to wait, or rather feek for more knowledge, and avoid fallacious fuppofitions or explanations. Sir Ifaac Newton fuppofed coloured matters to reflect the rays of light ; fome bodies reflect- ing the more, others the lefs refrangible rays mod copioufly j and this he conceived to be the true, and the only reafon of their colours. Mr. Delaval, however, has lately maintained (fee 2d vqI. of the Memoirs of the Philofophical and Literary Society of Manchefter), " that, in tranfparent coloured fubftances, the colouring matter does not reflect any light ; and that when, IBHH 7f PHILOSOPHY OF when, by intercepting the light which was tranfmitted, it is hindered from patting through fubftances, they do not vary from their former colour to any other colour, but become entirely- black :" and he inftances a confiderable number of coloured liquors, none of them endued with, reflective powers, which, when feen by transmit- ted light, appeared feverally in their true co- lours ; but all of them, when feen by incident light, appeared black : which is alfo the cafe of black cherries, black currants, black berries, &c. the juices of which appear red when fpread on a white ground, or otherwife viewed by tranfmitted, inftead of incident light ; and he concludes, that bleached linen, &c. " when dyed or painted with vegetable colours, do not differ in their manner of acting on the rays of light, from natural vegetable bodies ; both yielding their colours by tranfmitting through the tranfparent coloured matter the light which is reflected from the white ground :" it being apparent, from different experiments, " that no reflective power refides in any of their com- ponent parts, except in their white matter only," and that " tranfparent coloured fubftances, placed in fituations by which the tranfmiffion of light through them is intercepted, exhibit no colour, but become entirely black." ff The art of dying, therefore (according to Mr. Delaval), confifts principally in covering white fubftances, from which light is ftrongly reflected, with tranfparent coloured media, which, according to their feveral colours, tranf- mit more or lefs copioufly the feveral rays re- flected from the white fubftances," iince " the tranfparent ^"--«V '-A. t&Jtf ■ itg-iifi PERMANENT COLOURS, he. 75 tranfparent media themfelves reflect no light; and ic is evident that if they yielded their colours by reflecting, inftead of tranfmitting the rays, the whitenefs, or colour of the ground on which they are applied., would not in any wife alter or affect the colours which they exhibit." Having had reafon to differ from Mr. Delaval on fome other points, I am happy in being able to agree with him on this, fo far as relates to tranfparent colouring matters, when applied to wool, filk, &c. without the interpofition of any earthy or metallic bafis. But when any fuch opake bafis is interpofed, the reflection is doubt- lefs made by it, rather than by the fubftance of the dyed wool, filk, &c. and more efpecially when fuch bafis confifts of the white earth of alum, or the white oxyd of tin ; which by their ftrong re- flective powers greatly augment the luftre of co- lours. There are, moreover, fome opake co- louring matters, particularly the acetous, and other folutions of iron, ufed to (lain linen, cot- ton, &c. which muft neceffarily themfelves reflect, inftead of tranfmitting the light by which their colours are made perceptible. It has been already mentioned, that when the rays of light are feparated from each other by the prifm, in confequence of their different degrees of refrangibility, they produce a perception of feven diftinct colours, with all their interme- diate fhades ; and that thefe are ail equally fimple and primitive. There is, however, this pecu- liar property belonging to the red, yellow, and blue colours, whether prifmatic or permanent ; that they are incapable of being produced, like all :'W 76 PHILOSOPHY OF all the reft, by the combination of any other co- lours. Blue and red will compofe a purple ; blue and yellow, a green ; red and yellow, an orange, &c. ; but none of thefe, by any compo- fition, will produce either the blue, yellow, or red : thefe laft, therefore, are in all cafes fimple or uncompounded ; but all the others may be, and in reality are, fometimes fimple and fome- times compounded j not only thofe which are merely prifmatic colours, but thofe which exilt naturally in bodies, or are communicated by painting, dying, &c. Iron, as has been already mentioned, will, by different degrees of oxyda- tion, produce all pofTible varieties of colour j and thefe colours will be all fimple or uncom- pounded j and fo will the purple of gold, the green of copper, and the other colours found in the feveral oxyds of metals. This is alfo the cafe of the violet and purple dyed from log- wood ; of the green colouring matter of the leaves, &c. of vegetables -, of the green inner bark of elder, the green juice of the berries of the rhamnus catharticus, &c. ; and of the orange dyed from the quercitron bark, as will be here- after mentioned. And among animal colours, numerous inftances may be alleged of fimple or uncompounded greens, oranges, purples, and violets : even the yellowifli white liquor of the purpura, murex, and buccinum, from which the celebrated Tyrian purple was produced, pafTes quickly through all the (hades of yellow, green, violet, and purple, upon being expofed to the fun in atmofpheric air ; and thefe muft neceffa- rily be deemed fimple, not compound colours. But on the other hand, dyers, painters, &c. daily produce orange, green, purple, and violet, by •4nf* I ■ ■■ PERMANENT COLOURS, &c. 77 by mixtures of the blue, yellow, and red : nor is it neceflary that thefe fhould be intimately mixed, fince wool dyed of any two of thefe co- lours, if fpun and wove, will uniformly appear like the fimple homogeneous colour which, in the feries of prifmatic colours, lies between them. It has been repeatedly found in dying compound colours, as for inftance, green, that laying a permanent blue over a fugitive yellow, does not defend the latter, or make it in any de- gree more lafting, but that it will decay (leaving the blue in full ftrength) as rapidly as if no blue had been applied ; and therefore we may pre- fume, that the fibres of the dyed {tuff were but partly covered with the yellow colouring matter, and that when the blue came to be afterwards added, its particles found fpaces fufficient to lodge themfelves collaterally, without being placed upon the yellow particles. Several attempts have been mace to arrange and clafs the different fpecies of colouring mat- ters employed for dying and callico printing ; but none feems to accord with, or give any juft ideas of, their feveral natures and properties. Mr. Berthollet indeed alleges fufficient reafons for not dividing thefe matters, as Mr. Mac- quer did, into extractive and refinous, and alfo for not making their effects depend, as Mr. Pcerner has done, upon the mucilaginous, earthy, la- line, refinous, or oily parts of which they were fuppofed to be compounded, but without pro- pofing any fuitable arrangement of his own. To me, however, colouring matters feem to fall naturally under two general claffes ; the firft including m ft PHILOSOPHY OF including thofe matters which, when put into A ftate of folution, may be permanently fixed, and made fully to exhibit their colours in or upon the dyed fubftance, without the interpofition of any earthy or metallic bafis ; and the fecond, com- prehending all thofe matters which are incapable of being fixed, and made to difplay their proper colours without the mediation of fome fuch bafis. The colours of the firft clafs I fhall denominate Jubfiantive ; ufing the term in the fame fenfe in which it was employed by Bacon Lord Verulam, as denoting a thing folid by, or depending only upon, itfelf; and colours of the fecond clafs I fhall call aajeffive, as implying that their luflre and permanency are acquired by adjection upon a fui table bafis. Of fubftantive colours, I fhall firft notice the animal, theo the vegetable, and laftly the mi- neral. CHAP. IV. Of Subfiantive Animal Colo$rs. " Tyn^que ardebat murice lana." Virg. *T* H E moll celebrated and precious of all the A ancient dyes, was the purple, obtained from particular kinds of univalvular fhell-fifh ; of which the beft, and almoft the only accounts, handed down to us, may be found in the writ- ings of Ariftotle and Pliny, and efpecially of the latter, PERMANENT COLOURS, &c. 79 latter, in whofe time the purple dye feems to have attained its greateft perfection. They, in different places, have briefly mentioned the dif- ferent fhell-fiih from which the dye was obtained, how they were caught, and how their colour was prepared and applied to wool ; but thefe ac- counts, from their brevity, were better fuited to excite, than fatisfy, an enlightened curio- fity. Pliny, in the 36th chapter of his (eventh book, ranges the different (hell-fifh, giving the purple, under two genera : the firft comprehended the fmaller fpecies, under the denomination of Buc- cinum j fo called from their refemblance to a hunting horn ; and the fecond included thofe denominated Purpura. Thefe Fabius Columna conceives to have been alio diftinguifhed by the generic name of Murex ; though others fuppofe this to have fignified all the different fpecies ge- nerally. Many fabulous accounts have been given of the firft difcovery of the purple liquor, and its application as a dye, which feems to have been made at Tyre, about fourteen or fifteen centuries before the Chriftian sera ; and the Tynan dye, in confequence thereof, became highly celebrated in different countries. The feveral fpecies of fhell-fiih under confi- deration, were found as well on the European as the African coafts of the Mediterranean ; and they appear to have given colours of different fhades ; and the liquors yielding thefe colours were frequently mixed with each other, in vari- 5 ous H So PHILOSOPHY OF ous proportions, to produce other variations of colour : one, or at moft two drops, of this liquor were obtained from each fim, by ex- tracting and opening a little refervoir, placed in the throat. But to avoid this trouble, the fmalleft fpecies, as we are informed by Ariflotle and Pliny, was generally bruifed whole in a mor- tar; and this, according to Vitruvius, was often done with the larger ; though the other fluids of the fifh muft have neceffarily debafed the colour in fome degree. The liquor, when extracted, was mixed with a confiderable portion of fait, to preferve it from putrefaction, and was then di- luted with five or fix times as much water, and kept moderately hot, in leaden or tin vefTels, for the fpace of ten days, during which the liquor was often fkimmed, to feparate all impurities j after which the wool, being firft well wa(hed> was immerfed and kept therein for five hours, then taken out, carded, and again immerfed, and continued in the liquor until all the colour was exhaufted. To produce particular Ihades of colour, nitre, urine, and a marine plant, called Fucus, were occafionally added. Several of thefe varieties of colour have been particularly mentioned by ancient writers. One of them, which was very dark, feems to have been a vio- let, inclining towards the reddiih hue; " Ni- grantis rofse colore fublucens." Piin. lib. ix. feet. 50. Another, and lefs efteemed, was pro- bably a kind of crimfon ; but the moft efteemed, and that in which the Tynans particularly ex- celled, refembled coagulated blood ; " laus ei fumma in colore fang-uinis concretL" Plin. feet. 62. There was, moreover, a fourth kind, known in later times ; an account of which may be PERMANENT COLOURS, &c. 81 be found in Perrauk's tranflation of Vitruvius. Pliny fays, the Tyrians firft dyed their wool in the liquor of the purpura, and afterwards in that of the buccinum ; the purple mentioned in Ex- odus, chap. xxv. was alfo twice dyed. Wool which had received this double Tyrian dye (dia- bapha), was fo very coftly, that, in the reign of Auguftus, each pound of it fold for iooo Roman denarii (about 36 1. fterling). But left this mould not fufHciently exclude the ufe of it, from all who were not inverted with the higheft digni- ties, laws were made, inflicting {evere penalties, and even that of death, under the later empe- rors, upon all who might prefume to wear it. The art of dying this colour came at length to be practifed only by a few individuals, appointed and maintained by the emperors for that pur- pofe; and it being interrupted about the begin- ning of the 1 2th century, all knowledge of it was foon after loft, except what remained in the more ancient writings ; and during feveral ages this celebrated dye was confidered and lamented as an irrecoverable lofs. It happened, however, that Mr. William Cole of Briftol, being at Minehead about the end of the year 1683, heard, from two ladies there, of a perfon living at a fea-port in Ireland, t( who made confiderable gain by marking, with a delicate durable crimfon colour, the fine linen of ladies and gentlemen, fent him for that pur- pofe 1" and that this colour was " made by lbmc liquid fubftance taken out of a fhell-fifh.'' Mr. Cole being a lover of natural hiftory, and having his curiofity thus excited, went in queft of thele fhell-fifh i and after trying various kinds without G fuccefs, 82 PHILOSOPHY OF fuccefs, he at length found considerable quanti- ties of the buccinum on the fea-coafts of Somer- fetfhire, and the oppofite coafts of South Wales j and after many ineffectual endeavours, he at length found the colour in a u white vein, lying tranfverfely in a little furrow, or cleft, next to the head of the fifth ;" which, fays he, <{ mud be digged out with the fliff point of a horfe-hair pen- cil, made Ihort and tapering, by reafon of the vifcous clamminefs of the white liquor in the vein, that fo by its ftiffnefs it may drive in the matter into the fine linen, or white filk," in- tended to be marked. Letters or marks made in this way, with the white liquor in queftion, " will prefently," adds he, " appear of a plea- fant green colour, and if placed in the fun, will change into the following colours, ;. e. if in the winter, about noon, if in the fummer, an hour or two after fun-rifing, and fo much before fet- ting (for in the heat of the day in fummer the co- lours will come on fo faft, that the fucceffion of each colour will fcarce be diflinguifhable ;) next to the firft light green, will appear a deep green ;" " and in a few minutes this will change into a full fea green ; after which, in a few minutes more, it will alter into a watchet blue; from that, in a little time more, it will be of a purplifh red ; after which, lying an hour or two (fuppof- ing the fun ftili fnining), it will be of a very deep purple red; beyond which the fun can do no more." He remarks, however, " that thele changes are made fafter or flower, according to the degree of the fun's heat;" " but then," adds he, " the laft and mod beautiful colour, after wafliing in fcalding water and foap, will (the matter being again put out into the fun or wind PERMANENT COLOURS, &c. 83 wind to dry) be much a differing colour from all thofe mentioned, L e. a fair bright crimfon, or near to the Prince's colour ; which afterwards, notwithstanding there is no ftyptic to bind the colour, will continue the fame* if well ordered, as I have found in handkerchiefs that have been walhed more than forty times ; only it will be fomewhat allayed from what it was after the firft wafhing." Mr. Cole found, that, when linens marked with the white liquor in queftion were taken out of the fun, when the colours had only reached any one or more of the before men- tioned (hades, and (hut up between the leaves of a book, the colour or colours made no farther progrefs whilft fo fhut up, but remained always of the fame made. He alfo found, that whillt Jinen marked with the white liquor was drying by expofure to the fun, for the firft time, it would always art of the pulp; and fuffering the liquor to ferment too long, would fpoil the whole. When the liquor is all difcharged into the beaters, it is agitated with buckets, or by fuit- able machines, until the tincture begins to gra- nulate, or collect into little floculse ; and to haften this kind of granulation, or feparation, it has long been ufual to add clear lime water, in greater or fmaller quantities, until the liquor, in which the blue flocuke are fufpended, becomes, in other refpects, colourlefs. Great attention and exactnefs are neceffary in this, as well as in H 2 the ' ico PHILOSOPHY OF the former procefs, to render che qualicy of the indigo perfect j it is moreover requifite that the lime water employed fnould be perfectly clear, otherwife it will render the indigo hard, heavy,, and of a greyifh call. The liquor having been fufficiently agitated,, and impregnated with lime water, is left at reft, that the particles of the indigo may quietly fall to the bottom ; and this being done, the clear water is drawn off by a tap, placed juft above the top of the feculence or magma, which is af- terwards difcharged, by an opening below, into another receptacle, and from thence conveyed into linen bags, which arefufpended in order to let the water drain off; and this being done, the indigo is put into little fquare boxes, or formed by hands, into fmall lumps of different fizes and figures, and afterwards dryed in the fhade. Indigo fcems to confiit chiefly of a particular vegetable bafis, united to a large portion of oxygene, to which its colour is principally owing, and for which it has a ftrong attraction. In the firft operation, that of fleeping and fer- menting the plant, this bafis is not only diffolved and ex traded by the water, but a portion of pure air is abforbed (as is the cafe in all fimilar fermentations), foine of which combines with the bafis of indigo, which would indeed abforb fo much as to become black by a kind of com- buftion, if the fermentation were not previoufly flopped. In the fecond operation, by beating and agitating the liquor, a farther addition is made of oxygene, accompanied with a propor- tionate change of colour, through the feveral ihades •" -V "->'•* -S ■ "Je 1 -? ■ AiM -.-'>»->• PERMANENT COLOURS, &c. 101 ihades of green progreffively to thofc of blue; and alfo a collection of the very minute coloured particles into little diftinct mafTes, or flocula?. This is fomewhat analogous to the effects of churning on cream, or of violent fhaking upon ink in a bottle, by which its colouring matter foon forms large granulations, and falls to the bottom, where it continues incapable of being ever afterwards re-diffolved, or fufpended by the water, which it leaves perfectly clear. The addition of lime water farther promotes the fe- paration of the blue particles, by abforbing the carbonic acid produced by the previous fermen- tation of the liquor, and {till contained in it. At that precife ftate when the indigo is of a full deep green, and before any perceptible fe- paration or collection of its coloured particles has taken place, it is, I am perfuaded, in the ftate the beft fuited of all others to dye the mod permanent* if not the molt lively colours. The remaining parts of the procefs ferve only to col- lect the iubftance of the indigo into a dry folid form, in/which it may be more conveniently prefervetf, and transported to diftant countries for after ufe. I have mentioned that too much fermenta- tion, during the firft part of the procefs, would produce a beginning of combuftion, and black- hefs in the pulp of the indigo j and the like effects refult from too much beating, or agita- tion ih the fecond. On the other hand, if the coloured particles were feparated by lime water, before they had acquired a fufficiency of oxygene by agitation, the indigo would have a greenifh H 3 call, ,02 PHILOSOPHY OF caft, which is carefully avoided, as it might feem an unfavourable circumftance to perfons unacquainted with the true caufe ; though I am inclined to believe that fuch indigo would, in fome refpedls, be preferable to the other, espe- cially as it would be more eafily brought into the (tate of folution neceffary for dying. Indigo differs confiderably in colour; though its differences in this refpecT: may be compre- hended under three general divifions j the blue ? the violet, and the copper-coloured ; and each of thefe is the more pure and valuable, in propor- tion as it is more light : the lighted indigo is always blue, and fells for the higheft price ; this is more efpecially employed for dying Saxon blue. It is not yet known (though it has long been a defideratum) how either the blue, the purple, or the copper-coloured indigo may always be certainly produced, at the option of the operator. I fhall hereafter offer fome con- jectures on this circumftance. Of American indigo, that of Guatimala is the rnoft efteemed ; but of this there are three forts, the copper, violet, and blue ; the laft and beft is termed Flora by the Spaniards, and if floats on water. The indigo of Java was for- merly moft efteemed in the Eaft Indies, but the culture of the indigo plant having of late been greatly encouraged within the Englifh Eaft India Company's poffeftions, indigo, fuperior even to that of Guatimala, is now brought from thence in considerable quantities. The whole quantity imported annually into Great Britain, confiderably exceeds one million of pounds weight. ■H PERMANENT COLOURS, &c. 103 weight. One Englifh acre of rich land, by pro- per cultivation and management, may be made to yield five hundred pounds of indigo annually. The lighted and beft indigo burns almoft wholly away, leaving but a very fmall portion of white afhes behind. The fame colours, and ihades of colour, may be given by all the different kinds of indigo ; which feem therefore to differ principally by con- taining more or fewer impurities, and confe- quently more or lefs colouring matter. Water diflblves the mucilaginous, and fome of the ad- ventitious parts of indigo; of which alkohol diflblves others; but neither can diflblve any part of its colouring matter ; and this is alfo true of all the alkalies, whether cauftic or aerated, and of all acids, the nitric and fulphuric excepted. There are, indeed, but two ways in which indigo, when once formed, can be dif- folved : the firft of thefe is by means which attack its bafis, by fuperadding a farther portion of oxygene ; the other is by fubflances which ab- forb and take away from indigo a confiderable part of the oxygene combined with it, fo as thereby to render its bafis liable to be acted upon, and diflblved by the pure or cauftic alkalies. In the firft of thefe ways, fire fpeedily decom- pofes indigo : the nitric acid alfo, when concen- trated, attacks it fo powerfully, as to produce actual ignition ; and even when diluted it not only deftroys the blue colour immediately, but diffipates the greateft part of its fubftance, in the form of vapour, by a flower combuftion, leaving H 4 behind ^^H 104 PHILOSOPHY OF behind a rufty iron-coloured gummo-refinous mafs, foluble in alkohol, and partly fo in water, but of no ufe. Indigo reduced to powder, and mixed with five or fix times its weight of ftrong fulphuric acid (oil of vitriol), will be attacked with confiderable activity and heat; and in about twenty-four hours it will be difiblved. When adted upon by this acid, the colour of the indigo is rendered more lively and beautiful by the addition of a farther portion of oxygene, though it becomes lefs durable, Ipecaufe the bafis is made weaker by the a&ion and further addition of oxygene ; but more of this when treating of the Saxon blue. The muriatic acid, in its mod concentrated ftate, has no fenfible a&ion upon the pure co- louring matter of indigo, though it diflblves fome other parts of it. By an equal mixture of nitric and muriatic acids, indigo was rapidly dif- ibived, and its colour deftroyed, nearly in the lame way as by the nitric acid only. Having produced a mixture of vitriolic and muriatic acids, by pouring a fufFicient quantity of oil of vitriol upon fea fait, I found it diffolve the indigo more Aowly indeed than the fulphuric acid alone ; but the folution feemed to anfwer equally well for the purpofes of dying. It muft be oblerved, however, that neither the fulphu- ric, nor even the nitrous acid, when greatly di- luted, are capable of diflblving the colouring matter of indigo. The ■ PERMANENT COLOURS, & c . 105 The oxygenated muriatic acid acts but very feebly upon indigo, whilft in fubftance -, but when difiblved it deftroys the colour. Mr. Ber- thollet availed himfelf of this circumilance, to obtain a meafure for afcertaining the proportion- ate quantity of colouring matter in different kinds of indigo, by finding how much of the muriatic acid was nccefiTary to deftroy the colour of a given quantity of indigo, previoufly dif- folved by fulphuric acid. I think, however, this might be done with certainty, by feeino- how much wool a given quantity, fo difiblved, would dye of a particular made. 1 have found that, by adding a little manganefe to the folu- tion of indigo, by oil of vitriol, the blue colour was deftroyed as efficacioufiy, and in the fame way, as by oxygenated muriatic acid. The tartarous, acetous, phofphoric, fluoric, and other acids, feem to have no action on the colouring matter of indigo. None of the alkalies, either pot- afh, foda, or ammoniac, whether mild or cauftic, have any action upon the colouring matter of indigo, un- lefs when it has been previoufly difiblved by vi- triolic acid, or deprived of a portion ofoxygcne, as will be hereafter explained; nor has & lime water any power of diilblving it. In the fecond, and only way of difiblving in- digo, without lefiening the durability of its co- lour, there is no one fubftance, or agent in na- ture, capable of producing this effect but it re- mits from the concurrent action of different agents. Previous ■ io6 PHILOSOPHY OF Previous to the ufe of indigo in Europe, the blue dye was obtained folely from the ifatis (glaftum), or woad, of which there are two fpe- cies ; the ifatis tinctoria (commonly cultivated in this kingdom), and the ifatis lufitannica Linn, of which the laft is fomewhat fmaller than the firft. This plant being cut down at matu- rity, warned, and then expeditioufly dryed in the fun, is afterwards ground in a mill, then placed in heaps, fecured (by being covered) from the rain, and left to ferment during four- teen or fifteen days ; the external and internal parts are then well mixed together by (lirring, and the whole is formed into balls, piled upon each other, and expofed to wind and fun, in order that the remaining humidity may evapo- rate : but while this is doing, the balls begin again gradually to ferment, become hot, and exhale a portion of ammoniac, or volatile al- kali ; and if neceflary, the heat and fermenta- tion are promoted, by occafionally wetting the mafs until it afiumes the form in which it is commonly offered for fale. The proper modes of conducting the fermentation, and the exact times at which it ought to be flopped, ftill re- main fo uncertain, that thofe who make it their bufinefs to prepare woad, have no certain facts or indications to govern their management in thefe refpecls i and the goodnefs of any parti- cular quantity, or mafs, can never be afcer- tained otherwife than by the actual ufe which the dyer makes of it. The article is therefore bought and fold under the greateft uncertainties refpeifting its true value and fitnefs to anfwer the purpofes for which it is intended. The PERMANENT COLOURS, &c. 107 The ifatis contains the bafis of a blue colour, very fimilar to that of indigo ; but, by the pro- cefs juft defcribed, this bafis receives the changes which arife from fermentation, without being extracted from the plant, and collected, like indigo, into diftinft maffes. Aftruc, however, ibme years ago, maintained the practicability of obtaining indigo from the ifatis ; and this has been lately done in Germany, by a procefs fo nearly refembling that employed for producing jndigo, as not to merit a particular defcription. Mr. d'Ambourney has alfo done the fame thing lately at Rouen, in fmall quantities. But it feems probable, that, except for afcertaining the practicability of doing this, no benefit will ever refult from it, fince the indigo may doubtlefs be produced in, and imported from, other coun- tries, with much lefs expence than it will coft when obtained in Europe from woad. Mr. d'Ambourney mentions the " lymbe violet," or violet border, as a fign of the maturity of the paftel or woad j that in fermenting it with water to make indigo, the liquor on the third day ap- peared green, but the furface was covered with a kind of blue powder : that on the fourth day the leaves of woad feeming fufficiently macerated, and exhaling an acidofoetid odour, were taken out, and the remaining liquor appeared of an olive colour : that on the fifth day, finding in it no difpofuion to a feparation, and fubfidence of colouring matter, he put into it a portion of cauftic foap lees, and beat it with rods to pro- mote this precipitation ; after which the olive colour became of a duck green, then of a flate- coloured blue, with a bluifh froth. Mr. d'Am- bourney found, in fermenting the leaves of paftel, io8 PHILOSOPHY OF paftel, that the addition of an alkali, before the green colour was formed, wholly prevented it, and that a putrid fermentation took place in its ftead. He concludes, that one hundred pounds of the leaves may yield about one pound and a halfofindigo. Woad alone dyes a blue colour very durable, but lefs vivid and beautiful than that of indigo ; it is therefore, at prefent, never ufed except with indigo, in what is called the woad- vat, in which it is made to ferment with water, by a fuitable degree of warmth, and the addition of bran, with other vegetable matters : to thefe, in- digo and lime are afterwards joined ; and the indigo being deprived of a portion of its oxygene by the fermenting vegetable fubftances, is there- by rendered foluble by the lime ; and being in this way foon combined with the colouring mat- ter of the woad, both form a dying liquor, blue or copper-coloured on the furface, where it can re-abforb the oxygenous gas, but green imme- diately beneath the furface, and throughout the whole mafs. When the liquor becomes, and while it continues, green, it is fit for dying; and cloth or wool dyed with it, though they appear green when taken out, become blue immedi- ately, by attracting and combining with the ox- ygene ; the lofs of which had previoufly ren- dered the liquor of the woad-vat green. The ufe of indigo had fcarcely been introduced into Eu- rope, before it was prohibited in fome countries, from a perfuafion that its colour was fugitive; and in trance, under the enlightened admini- itration of Colbert, the ufe of it v/as only per- mitted in a certain imall proportion, along with woad. PERMANENT COLOURS, &c. 109 woad, in forming the vat juft mentioned j lb very liable are mankind to entertain falfe opinions reflecting the value and properties of dying drugs. There are various other blue vats in which indigo is diffolved, and made fit for dying, without being united to woad. Thefe, how- ever, are generally known, and have, moreover, been fufficiently defcribed by Hellot, Quatre- mere, Le Pileur d'Apligny, Berthollet, and others. They differ confiderably from each other; but in all of them the indigo is firft de- prived of a portion of its oxygene, by the at- traction of vegetable or animal ferments, or of the oxyd of iron (feparated from copperas) ; and then it is diflblved either by lime, or by fome alkali, either vegetable, mineral, or vo- latile. The woad- vat firft mentioned is almoft the only one ufcd for dying wool, and woollen cloths or fluffs. Silk is commonly dyed from a different vat, in which indigo (without any woad) by the aid of a fufEcient degree of warmth and of vegetable alkali, with vegetable ferments, bran and madder, is diffolved, and made to produce a fine green liquor, with a bluifh cop- per-coloured fcum on the furface, &c. Indigo, however, is incapable of dying filk of a deef blue colour, without the help of archil, or fome other colouring matter. Cotton is dyed in a blue vat, into which in- digo, ground either in water, or in a cauftic al- kaline ley, is put, with two or three times its weight of lime, previoufly flacked in a fufficient quantity of water, and about one-fourth lefs of copperas ■H no PHILOSOPHY OF copperas (fulphat of iron) than of lime. When this mixture is made, a part of the lime unites with the acid of the copperas, forming calcare- ous fulphat or felenite, and at the fame time precipitates the oxyd of iron, which, not being Saturated with oxygene, attracts fo much of that which was combined with the indigo, as to render this laft fubftance foluble, by the lime remaining over and above what was employed to faturate the fulphuric acid. The beginning diffolution of the indigo may be perceived by a fhining cop- per-coloured pellicle, which forms itfelf on the furface of the mixture, while the liquor itfelf becomes green, and afterwards gradually in- clines more and more to the yellow, as the fo- lution advances. "When it is completed, and the liquor fettled, the cotton, yarn, or (luffs are, to be dyed in it : at firft they will appear yellow when taken out, but by abforbing the oxygene, they rapidly affume and pafs through the different fhades of green, and in a few mi- nutes become blue, the oxygene regenerating the indigo in the pores of the cotton. Mr. Hauffman, of Colmar in Alface, who, with a good flock of chymical knowledge, daily prac- tifes the arts of dying and callico printing, lately publifhed an excellent " Memoire fur Tlndigo & fes diffolvans," in the Journal de Phyfique, &c. for March 1788, in which he mentions, that the change of colour from yellow to blue, in cottons dyed as before mentioned, may be greatly accelerated, and their colours made deeper than they would otherwife become by plunging the dyed cottons, when firft taken out of the vat, into water foured by vitriolic acid, which haftens the regeneration of the indigo, 5 and PERMANENT COLOURS, &c. m and moreover diflblves and carries off a portion of white calcareous fulphat or felenite, which would weaken the ftrength or intenfity of the blue colour. If the colour of the vat be not all ufed foon after it has been prepared, it will require occa- fional ftirring ; fince the difiblved indigo, by continually abforbing oxygenous gas from the atmofphere, will be conftantly reviving, in con- fiderable quantities, upon the furface of the li- quor ; and the indigo fo revived can only be re- diffblved by being again fubjected to the com- bined action of lime, and oxyd of iron : if by length of time thefe fhould become perfectly fa- turated with oxygene and carbonic acid, before the blue colour is all 'tried, a farther portion of each mull be added, and fomewhat more of lime than of copperas. Mr. HauiTman obferves, that all the precipi- tates of iron, whether obtained from folutions of that metal by the mineral, vegetable, or animal acids, will ferve, with quick lime, to diflblve indigo, as well as that of green vitriol, provided, or fo long as they retain the property of abforb- ing vital air -, but that a nitric folution of iron, or the ruftof it, or any other preparation where it exifts in an ochrous form, not attracted by the magnet, nor capable of attracting pure air, will be wholly ufeleis towards producing a diflblution of indigo, though employed with an excefs of quicklime, or of cauftic alkali. He conceives, that the precipitate of iron, obtained from cop- peras, promotes the diflblution of indigo by its phlogiiton i and that he cannot fatisfactorily ex- plain ii2 PHILOSOPHY OF plain this effect upon the new fyftem, unlefs by iuppofing, that the oxygene only adheres to the integrant molecules of the indigo, without an actual combination (which he thinks impro- bable); and that the oxygene having ftronger affinity to the precipitate of iron than to the in- digo, quits the latter to unite with the former; while the indigo, in giving up the oxygene, unites with the lime, or cauftic alkali, and is difTolved by them ; which indeed ieems to be the true explanation. Mr. Haufiman further obferves, that cauftic alkali, with fine iron filings, inftead of the pre- cipitate from copperas, would not diflblve in- digo; but that (regains of) antimony, brought into the form of a powder, difTolved it perfectly with the cauftic alkali, or quick lime flacked by water ; though the calces, or oxyds of antimony, in^ this way, produced no fuch effect: : nor did any precipitates of copper : on the contrary, they all feemed rather to haften the regeneration of indigo, after it had been difTolved by fome other means : and he adds, that fome dyers avail themfelves of this effect, to obtain, at once, all the colour remaining in a blue van (after it has been too weak to dye properly), by palling cottons through water in which a little iulphat of copper (blue vitriol) has been dif- Tolved, and then dying them in the vat intended to be exhaufted, where the Iblution of copper Jpeedily precipitates, and revives the remaining indigo in the pores of the cotton. I have repeated moft of Mr. Hauffman's ex- periments, with different precipitates, or oxyds 3 of PERMANENT COLOURS, Lc. nj of iron, and with effects nearly fimiiar to thofe he defcribes. I found that neither the ruft of iron, nor the nitric oxyd of it, would aiTift in the diflblution of indigo ; obvioufly becaufe they were both already faturated with oxygene ; I alfo found, that even a precipitate of copperas failed for the fame reafon, when, inftead of leparating it by lime, it was made by diffolving copperas in water, and leaving it for fome weeks expofed to the air in warm weather, where the iron was farther acted upon, and faturated, as well as precipitated, by the oxygene which it gained from the atmofphere. It is nearly in the fame way, and upon the fame principle, that the topical indigo blue, em- ployed by calico printers for penciling, is made : the ingredients of this compofition are employed in different proportions in different places ; and will fucceed with very confiderable latitude in this refpecl: : indeed, the different qualities of indigo neceffarily render it impoflible to prefcribe any exact proportions, which fhall be always equally efficacious and fuitable. Mr. Hauffman mixes twenty-five gallons of water with fixteen pounds of indigo, well ground (or a greater or fmaller quantity, according to the quality of the indigo, and the depth of co- lour wanted), to which he adds thirty pounds of good carbonate of pot-afh, placing the whole over a fire; and as foon as the mixture begins to boil, he adds, by a little at a time, twelve pounds of quick lime, to render the alkali cauf- tic, by abforbing its carbonic acid, or fixed air„ This being done, twelve pounds of red orpiment; I arc »M PHILOSOPHY OF are alfo added to the mixture, which is then ftirred, and left to boil for fome little time, that the indigo may be perfectly diflblved; which may be known by its giving a yellow colour, immediately upon being applied to a piece of white tranfparent glafs. M. Ober- kampf, proprietor of the celebrated manufac- tory at Jouy near Verfailles, ufes a third more of indigo ; and others uie different proportions, not only of indigo, but of lime, pot-afh, and orpiment ; which all feem to anfwer with nearly equal fuccefs : but with the beft copper- coloured Guatemala indigo, it is certain that a good blue may be obtained from only half the quantity prescribed by Mr. Hauflfman, by ufing as much ftone, or oyfter fhell lime, as of indigo, nearly twice as much pot-afh, and a fourth part lefs of orpiment than of indigo. This compofition is greatly defended from air by gum, which (hould be diflblved in it whilft hot ; and it fhould after- wards be kept fecluded as much as pofllble from the contact both of vital air, and carbonic acid gas or fixed air. Indigo diflblved in this way, for penciling or printing, I fhall hereafter call topical blue — its itrong tendency to attract oxygene from the at- mofphere, and to be thereby regenerated, ren- ders its uie fubject to many difficulties ; it being almoft impoffible to pencil, and more fo to print, a piece of cotton throughout of the fame made, with the beft endeavours, to apply it equally, and quickly, by the mod expert and careful hands. It will give a fall colour only lb long as it continues yellow, or, at moft, of a yellowifli green j as foon as it appears blue, the indigo may ~>V<$- -»: >*j.-» PERMANENT COLOURS, &c. 115 may be confidered as revived, and incapabje of fixing on the cotton : in this caie, however, ic may be re-difiblved, by adding more canftic al- kali and orpiment. The clear liquor only 3 when gummed, is to be ufed ; but it is not to be fe- parated from the fediment, which helps to pre- ferve it in aftate of diflblution. In making the before-mentioned compofition, a copper-coloured pellicle appears on the furface of the liquor as foon as the indigo begins to dif- folve; and this pellicle becomes violet, and at laft blue, by longer expofure to the atmofphere. Mr. Hauflman obferves, that the fame pellicle arifes, with the fame appearances, if the folution of indigo be put into contact with either the de- phlogifticated or the vital airs ; but that, under the receiver of a pneumatic machine, it dimi- nifhes in proportion as a vacuum is produced j and that it does not appear at all in the inflam- mable or the phlogifticated airs. Mr. HaufTman farther obferves, that if, inftead of orpiment, fulphur and white arfenic, of which it is formed, be employed, either together or fepa- rately, with quick lime and pot- afn, no folution of indigo will take place ; and this wili alfo be the cafe, even where orpiment is ufed, if quick lime be not employed to render the alkali cauf- tic. That having put indigo, diffolved by or- piment, lime, and pot-afh, into contact with dephlogifticated air (oxygenous gas), obtained by diftillation from nitre, he found in a little time that feven- eighths of it were abfoi bed by the folution of indigo, and the remaining eighth was azote only (phlogifticated air) ; and the blue was rendered unlit for ufe, the indigo being re- I 1 generated, n6 PHILOSOPHY OF generated, as he found it, at other times, from the application of fixed air (carbonic acid) ; but with this difference, that a part of the alkali re- mained cauftic, while another part of it com- bined with the vitriolic (fulphuric) acid (formed by the union of the fulphur to a part of the ab- forbed oxygene), and thereby produced vitrio- lated tartar (fulphat of pot-afh) : another part of the oxygene, fo abforbed, had combined with the arfenic, and changed its metallic form to that of an oxyd, in which ftate it had united to the cauftic alkali ; and the reft of the abforbed oxygene had combined with, and regenerated the diflblved indigo. Mr. Haufiman was indeed inclined to explain the folution of indigo, according to the phlo- giftic fyftem, by confidering it as refultingfrom a greater affinity which phlogifton was fuppofed to have with indigo than with arfenic, and that it was the action of this phlogifton, joined to that of the cauftic alkali, which operated the dif- folution in queftion ; but that the phlogifton, having ftill a greater affinity with dephlogifti- cated air than with indigo, abandoned the latter as foon as the former was prefented to it, leav- ing the indigo in its regenerated form, the alkali alone not being fufficient to preferve it in a ftate of folution. But a much happier, and more na- tural explanation of thefe effects, is afforded by the new doctrine, as already ftated j and it is ftrongly fupported by all that we know of the nature of indigo, and the properties of thofe agents employed to difiblve it. Experiments made by Dr. Prieftley, and others, evidently prove that iron, in the ftate in which it exifts ia copper as 4 ■■ PERMANENT COLOURS, kc. 117 copperas, or when recently precipitated from a folution of copperas, forcibly attracts, and com- bines with, vital air brought into contact with it ; and it is alfo well known, that the fulphuret of arfenic (orpiment) does the fame, when dif- folved by an alkali. Mr. Hauffman found, that the fulphuret of antimony (crude antimony) aflifted in diffolving the indigo, for topical blue, as well as orpi- ment, but that it was unfit for penciling or printing ; becaufe the antimony was precipi- tated, in the form of a mineral kermes or golden fulphur, tarnifhing the blue colour, and adher- ing to the linens or cottons almoft as ftrongly as tiro indigo itfelf. The oxyd of antimony, with fulphur, did not produce a folution of the in- digo, when ufed inftead of the crude antimony ; though antimony, in its metallic ftate (u e. the regulus), reduced to powder, had occasioned the diffolution of indigo in the fame way, and as well as the crude antimony. He found, what is very remarkable, that no fuch effect was produced by the filings of zinc j though when heated it has greataffinity withoxygene. He attempted, in vain, to diffolve indigo, by a combination of fulphur with the other metals (befides antimony and arfenic) ; and he attributes his want of fuccefs to the circumftance of their being diffolved with difficulty, or perhaps not at all " par la voie humide," in the cauftic alkalies. Befides repeating a great part of thefe expe- riments, and with fimilar effects, I have made fume, which, probably, were not attempted I 3 before i n8 PHILOSOPHY OF before ; and feveral of them with effects highly deferving of notice. I boiled, for two hours, the fineft blue Gua- temala indigo in water, with about four times its weight of highly-burnt oyfter-fhell lime, which I took hot from the fire, and put into the water r to fee whether lime had, in this way, any action upon indigo : the better to afcertain this, I put into the boiling liquor a fmail piece of white broad cloth, and another of white ca- lico : in about an hour both were taken out, and the broad cloth was fo far diflblved by the lime, that it crumbled on being prefled between my fingers •, but the calico did not feem hurt ; though neither were in any degree coloured by the indigo. I afterwards added a quantity of pure carbonated pot-afh, equal to that of the lime which had been ufedj and I continued the boiling for two hours more, and then leaving the liquor quiet, I foon found the indigo and lime had fettled to the bottom, and left the water perfectly colourlefs. The next day the mixture was well flirred, and boiled again for two hours j and being left tc fettle, it again gave the fame proof of there having been no dif- folution of the indigo, I had at hand about a pound of an oxyd of tin, prepared fome time before (for a different purpofe), by putting two pounds of common fingle aqua foftis, diluted with as much water, upon a quan- tity of tin, not in very fmall pieces, and leav- ing the former to act: fiowly upon the latter during feveral months, until all its oxygene was exhauited ; after which I found the oxyd, or calx, formed into lumps as large as a walnut, and PERMANENT COLOURS, &c. 119 and fettled at the bottom. The clear liquor being decanted from the oxyd of tin, the latter v/as (lightly rinced with water, and being dried, remained in folid lumps. Some of thefe, weigh- ing about twice as much as the indigo which I had employed, were then put into the cauftic al- kaline liquor, in which I had ineffectually endea- voured to diiTolve the indigo; and in lefs than five minutes I perceived figns of a beginning difTolution, which increafed rapidly ; and in half an hour the liquor had pafled through all the (hades of green, and become yellow, except at its furface, which was covered by a fine cop- per-coloured pellicle, of a mining metallic ap- pearance. Silk and cotton dipped into the li- quor, were taken out yellow, and became green, then aflumed a mining copper- colour, and afterwards changed to violet, and then be- came blue; and were found, by warning, to be permanently dyed. Part of the fame liquor, gummed, and applied topically, anfwered as well for penciling as any topical blue I ever faw. Another part of it, being poured into a white glafs phial, fo as to fill it to the top, with a por- tion of the lime and oxyd of tin, fhakcn all to- gether, but without gum, and being well flop- ped and left at reft, in a few days became as pellucid and colourlef> as clean water, excepting only the fediment at bottom. Upon unftopping the phial, the furface of the liquor, coming into contact,^ ith the atmofphere, and abforbing ox- ygene, inftantly became green and blue; and upon re-ftopping the phial, and making it, the indigo forming this blue furface was difperfed through the mafs of liquor, and tinged it of a beautiful greenifh yellow ; but there being a I 4 fuffieienc t20 PHILOSOPHY OF fufficient quantity of oxyd of tin unfaturated, the oxygcne was foon abforbed, and the liquor again rendered colourlefs : when, inftead of the oxyd of tin, I employed the metal finely gra- nulated, it produced no effect towards diffolvino; indigo ; and on trying tin, which had been cal- cined with faltpetre in a crucible, I found that it not only did not diffolve the indigo itfelf, but prevented it from being diffolved by the oxyd of tin (produced by the aqua fortis, as juft men- tioned), or by crude antimony, or copperas either fingly or combined ; indeed it was with difficulty diffolved, when orpiment, in a large propor- tion, was added to all the above -, this I alfo found to be the cafe of tin, calcined alone in a crucible by ftrong heat: bifmuth calcined in like manner, equally obftructed the folution of indigo. Probably in thefe cafes the metals fo calcined not only do not attract the oxygene of indigo, but let go that which they had imbibed during calcination. In the courfe of my experiments upon in- digo, I was induced to make trial of refined fugar, inftead of orpiment ; and I found that the fugar acted very efficacioufiy in diffolving in- digo, with the ufual appearances, and producing a topical fubftantive blue, as permanent, and every way as good as any in ufe. I afterwards tried coarfe brown fugar, and I found it at lead as effectual as the refined, for this purpofe ; it then occurred to me, that this might be a valu- able fubftitute for orpiment, the ufe of which, as a conftituent part of the topical blue, may, from its poifonous quality, fometimes produce jnifchief, and always gives the compofition an unpleafanc PERMANENT COLOURS, Sec. 121 unpleafant fmell. I moreover conceived, that, by employing a large proportion of brown fugar, it might be practicable to thicken the mixture fufficiently for penciling or printing, and thereby avoid the greater expence of gum for that purpofe ; and upon trial, this alfo proved to be the cafe, the fugar thickening the folution iufficiently, and afterwards drying as expedi- tioufly as when thickened by gum, contrary to what I had apprehended as probable, from recollecting that ink, when thickened by fugar, was difpofed to retain moifture, and dry very fiowly. I think, moreover, that when the folution of indigo is both made and thickened by fugar, in this large proportion, the latter, by being able to abibrb a larger quan- tity of oxygene from time to time, enables the topical blue to bear expofure to the atmofphere fomewhat longer, without a regeneration of the indigo, than when it is diffolved by only the ufual proportion of orpiment. I think, there- fore, that this way of compofing a fubftan- tive topical blue, by employing coarfe brown fugar, inftead of both orpiment and gum, is deferving of particular attention, as forming a compofition free from all poifonous qualities, and at the fame time cheaper and better than that generally ufed. Melaflfes will ferve as well as brown fugar to promote the difiblution of in- digo ; but I think not fo well to fupply the place of gum in thickening the compofition. Sugar ufed in this way, feems to act like or- piment in combining with oxygene ; which it is itrongly difpofed to do in other circumftances. M. Berthollet, in the fecond volume of the An- nates 122 PHILOSOPHY OF nales de Chymie, mentions, that, in diftilling the fulphuric acid upon different animal and vege- table fubftances, he found none of them fo pro- per to form a large quantity of fnlphureous acid j which it could only produce by its great affinity with oxygene. I found, upon different trials, that, with the help of pot-afh and lime, I could not diiTolve indigo, either by fulphur. or white arfenic, or charcoal, or oxyd of bifmuth, or of lead (mi- nium), or of zinc (lapis ca'aminaris), or of manganefe, or the alkaline folution of flints, or of the earth of alum, or by magnefia. I was equally unfuccefsful with copper, as well in its metallic form, as in all the uiual preparations of it: and indeed when indigo was mixed with verdigrife, lime, and pot-afh, as ufual, it not only did not diffolve it, but the verdigrife pre- vented the action of all other agents upon it, in- fomuch that the indigo remained undiffolved, notwithstanding the combined action of crude antimony, orpiment, oxyd of tin, copperas, and fugar in large dofes, any one of which, with the quick lime and pot-afh, would have effectually difiblvcd the indigo, had there been no verdi- grife or copper in contact with it. The fulphat of zinc (white vitriol) was almoft as adverfe to the diffolution of indigo ; for it not onlv did not contribute thereto, with pot-afh and lime, but it prevented any folution from taking place by the oxyd of tin, crude antimony, fugar, and copperas, applied one after the other : though when to all thefe a large portion of orpimenc was added, and the mixture kept fome time in a boiling heat, the indigo did at length diffolve, but PERMANENT COLOURS, &c. 123 but with great difficulty and tardinefs. Vermi- lion I found, on repeated trials, incapable of contributing, in any degree, to diflfolve indigo with lime and pot-afh ; though it did not ob- ftruct the diftblution thereof, when orpiment was added. Camphor appeared to have no effect. The topical blue, when made, is often applied by the pencil upon fpots or figures previoufly dyed yellow, in order to produce, a permanent green; but the cauftic alkali contained in it, efpecially when employed too freely, feems to weaken the yellow on which it is laid. Wifhing to remove this difficulty, I thought of neutra- lizing the alkali, at leaft in fome degree, fo as to make it harmlefs in this refpect, without, an the fame time, rendering the blue lefs effica-* cious. I could not, however, expect to do this, with either the nitric, fulphuric, or acetous acids ; becaufe they are now univerfally allowed to derive their acidity from oxygene 3 which, if applied to indigo, necefiarily would produce the regeneration of it, and make it unfit for pen- ciling or printing. I knew, however, that though Mr. Lavoifier had, from analogy, been induced to conclude that the muriatic acid de- rived its acidity, like mod others, from oxy- gene, yet there was good reafon to doubt its exiftence in muriatic acid ; that this acid, in- ftead of being fixed, was rendered more volatile by oxygene, and that, inftead of becoming more, it was made lefs acid by every addition of oxy- gene ; circumftances which do not feem to in- dicate that this is the acidifying principle of mu- riatic acid. I knew alfo, that Mr. Berthollet was, 124 PHILOSOPHY OF was, at length, nearly convinced that the muri- atic ought to be deemed a radical acid, which, by the means of a certain portion of oxygcne, gained properties fimilar to thofe of the nitrous and fulphureous acids, and, being fuper oxy- genated, acquired relative properties, fimilar to thofe of the nitric and fulphuric acids : I re- fblved, therefore, to try their different effects upon the topical blue, and for this purpofe I mixed the acetous, fulphuric, and nitric acids, each feparately, with a portion of it ; and I found that, even in fmall quantities, they in- ftantly deftroyed the green and yellow colours of thediffolved indigo, and, by reviving it, rendered the mixture uniformly blue ; producing, at the fame time, a confiderable effervefcence. Muriatic acid, however, acted differently ; for, though it produced fome effervefcence, it neither ren- dered the mixture, nor even its eftervefcing fur- face, which was covered with froth, blue, but both remained green, while fecluded from the contact of atmofpheric air, by being inclofed in a veffel well (topped ; and I found it practicable to neutralize the alkali completely, without ren- dering the indigo unfit to produce a faft blue colour, or a green, upon yellows, if applied quickly ; but when the topical blue, thus neu- tralized, was kept fome time, the indigo, being deprived of the alkali which had heki it in foiu- tion, gradually fubfided in a great degree, and became unfit to be applied in this way. There is, however, I think, an intermediate degree to which the alkali may be neutralized, without precipitating the indigo, in any confiderable quantity, for feveral weeks at lead, and which will be fufficient to prevent the alkali from ex- ercifmg ■■■i PERMANENT COLOURS, &c. 125 ercifing any action injurious to the yellow co- lours upon which the blue may be laid. The topical blue made with fugar effervefced but very flightly when mixed with muriatic acid, and therefore it has, in this refpect, an advantage over the blue made with orpiment. The fluoric is another acid, in which the exigence of oxy- gene has never been proved, or made probable, otherwise than by analogy. This circumftance led me to try it alfo with the topical blue ; when I found its effects very fimilar to thofe of the muriatic acid. The eighth part of a phial being filled with the fluoric acid, and fome of the blue prepared with fugar, as before defcribed, being poured upon it, no effervefcence appeared, and the mixture remained of a yellovvim green co- lour ; cotton plunged in it imbibed, and conti- nued of the fame colour, until it was taken out and expofed to the air, when it gradually aflu med a very deep, ftrong, blue colour, which, upon beino- wafhed in warm foap fuds, was found perfectly fixed. The fame experiment, with fome variation of circumftances, was feveral times repeated, and always with fimilar effects ; and upon the whole, the fluoric acid feems even better fuited than the muriatic to neutralize the alkaline part of the to- pical blue, where it may be thought expedient to have it in a neutral ftate -, though, I think, fomething fhort of this is all that can be wanted, or fhould be attempted, in the bufinefs of calico printing. I am fenfible, that, though thefe facts afford new reafon for not believing that oxy- gene is the acidifying principle of the muriatic and fluoric acids, they do not abfolutely prove the contrary j becauie they may contain oxy- gene, fo intimately united to their refpective bafes, 1*6 PHILOSOPHY Of bafes, as that it can neither be feparated, nor left at liberty to manifeft any of its ufual properties j but, allowing this to be poffible, we mull not, I think, fuppofe it to be really the cafe, with- out more probability thereof than yet appears. This indeed was partly thecafewith vitriolic ether, which, being added to topical blue prepared with fugar, did not much change its colour, nor pre- vent it from being fixed in fome degree on cotton. Wifhing to know what effects would refult from a ftronger action of pot-afh, lime, and or- piment upon indigo, I diftblved it with three times the ufual portion of thefe agents, and hav- ing afterwards fhaken the whole mixture well together, 1 filled a large tranfparent glafs phial therewith (but without any gum), and having feeured it from all contact with external air, by a glafs ftopper covered with wax, I left it in that ftate for three months, fhaking the phial occafionally, that the more fluid part of the mixture (which foon became nearly colourlefs) might be acted upon more equally, by the lime, &c. at bottom; after which, the phial being opened, I found that the mixture (which gave a deep permanent blue to cotton, when firft made) had become incapable of manifefting any colour by the contact of atmofpheric air, or by the ad- dition of fulphuric, fluoric, and other acids ; the indigo having been not only deprived of the oxygene neceflfary to its colour, but probably rendered incapable of re- uniting with it as for- merly, in confequence of a decomposition of its vegetable bafis, or a new combination thereof with one or more of the agents in queftion, too 5 intimate PERMANENT COLOURS, &c. 127 intimate to be overcome by any of the ufual means of regenerating indigo. Here we have an inftance of one of the moft permanent of co- louring matters lofing its colour ; not by any thing like, combuftion, which neceffarily re- quires the prefence and combination of vital air, but by means which feclude it from, and de- prive it of, all fuch air. In forming fome of the indigo vats, it has been ufual to employ a considerable quantity of madder and weld, though neither of them, in this way, can pollibly do any good as colouring fubftances, their colours having no permanency without an aluminous, or other bafis, as will be hereafter explained ; they can therefore produce no benefit in any other way than as promoting fermentation ; for which purpole many cheaper matters would prove infinitely more efficacious, particularly melafTes, carrots, parfnips, fhells of green peas, &c. &c. It is to be obferved, that all the preceding means of rendering indigo foluble, by abftracl:- ing a part of its oxygene, ferve only to bring it back to the (tare in which it exifted while retain- ing its green colour in the procefs of fer- mentation, before its minuteit particles had been collected together, in a concrete blue form, by agitation, and the farther applica- tion of oxygene. I have already intimated a perfuafion, that the colouring matter of the indigo plant, in this fluid ftate, is not only fit for dying, but that the blue colour dyed with it, would, like that of the ifatis, or woad, be yet more permanent than that given by the indigo, after 128 PHILOSOPHY OF after it has been made to aflume a concrete form % becaufe its ban's, even by the leaft destructive ways of diflblving it, will, I think, neceffarily be in fome degree weakened, as all other vege- table colours are found to be, by the action of fuch powerful agents as are requifite for that purpofe ; and I conceive that the very durable blues which are known to be given by particular people in fbme parts of Afia and Africa, muft be derived from the colouring matter of the in- digo plant, employed when firft extracted by fteeping and fermentation. The Chinefe are faid to employ the indigo plant for dying in this way ; and it appears that the Africans employ it in a way nearly fimilar, at leaft with refpect to the (late of its colouring matter, applied as a dye. According to Mr. Ciarkfon, " it is well known, at lead in the manufacturing towns, that the African dyes are fuperior to thofe of any other part of the globe." " The blue (conti- nues he) is fo much more beautiful and perma- nent than that which is extracted from the fame plant in other parts, that many have been led to doubt whether the African cloths brought into this country were dyed with indigo or not. They apprehended that the colours in thefe, which became more beautiful upon wafhing, muft have proceeded from another weed, or have been an extraction from fome of the woods which are ce- lebrated for dying there. The matter, how- ever, has been clearly afcertained : a gentleman procured two or three of the balls, which had been juft prepared by the Africans for ufe : he brought them home, and upon examination found PERMANENT COLOURS, &c. 129 found them to be the leaves of indigo rolled up, and in a very fimple ftate. M. Adanfon, mentioning the indigo plant cultivated by the negroes of Senegal, fays, thefe people do not take much pains to draw the dye out of this plant ; they are fatisfied with ga- thering the leaves at any time of the year, with pounding them in a mortar to reduce them to a pafle, and with making them up into loaves, in order to preferve them dry. When they want to make ufe of them, they diflblve them in a kind of lye, made of the afhes of an unctuous plant which grows in their fields, and is by them called rhemi (Portulacca Marina, &c. Plum. Cat. p. 6.). This diflblution, adds he, im- bibes a tincture of the indigo, into which they dip their linen cold, as often as they think ne- cefTury, according to the deepnefs of the co- lour. See his Voyage to Senegal, the Ifle of Goree, and the River Gambia. 8vo. The indigo plant, when ufed in the way which M. Adanfon defcribes (with too much brevity in- deed), feems to be in a ftate refembling that in which the ifatis or woad is commonly employed, as before mentioned ; and unlefs the freight would prove too expenfive, I fhould think it might be advantageoufly imported in balls, like thofe mentioned by him, to affift in forming in- digo vats, though it would not anfwer in this ihape for producing what is called the Saxon blue, by a combination with fulphuric acid. Of Saxon Blue. Indigo difiblved by the fulphuric acid, ac- quires a more lively though a lefs durable co- lt lour hMHi 130 PHILOSOPHY Of jour than it naturally pofTefles, or can be made to receive by any other means ; probably becaufe it thereby acquires an additional portion of oxy- gene. The application of this blue as a dye was firft made by Counfellor Barth at Groffen- hayn in Saxony, about the year 1740. He em- ployed, befides indigo and fulphuric acid, lapis caliminaris and antimony, mixing them with the oil of vitriol firft, and adding the indigo af- terwards. According to fome, he alfo employed allum ; but all thefe additions being found ufe- lefs, were afterwards laid afide. M. Hauflman obferves, that a fmall piece of indigo put into a little fulphuric acid of proper ftrength, becomes very foon coloured upon its external furface, firft of a greenifh yellow, and afterwards of a deep green, and finally of a blue j that in evaporating indigo, which had been diftblved by this acid in a glafs vefifel placed on a fand heat, there efcaped a portion of fulphureous or volatile vitriolic acid, and of hydrogene (inflammable gas), which upon ap- plying to them the flame of a candle, gave flight marks of inflammation ; that the expanfion of the indigo, and feparation of fulphureous in- flammable vapours, during its folution by oil of vitriol, leave no room to doubt of the ftrong action of the latter upon the conftituent parts of indigo; and he therefore concludes, that we mould err in confidering the indigo as having fuffered no alteration by the fulphuric acid, and in comparing a folution of it in this way to thofe other folutions already defcribed, in which the bafis of indigo fuffers little or no injury ; that the blue dyed by thefe fulphuric folutions of in- digo, can hardly be deemed a fail colour, fince it PERMANENT COLOURS, &c. 131 it is eafily extracted by foap in boiling water, and changed by alkali to an olive colour, more or lefs yellow, according as the alkali is more or lefs cauftic ; and fince the adhefion of this blue to linen and cotton is fo feeble, that even cold running water will carry it off. Bergman afcribes the want of greater perma- nency in the Saxon blue to the ufe of fulphuric acid not fufficiently concentrated. He ufed an acid whofe' fpeciftc gravity, compared to that of water, was as 1900 to 1000, and employed eight pounds of this acid to diffolve one pound of indigo. I believe, however, that he has been milled on this fubject, and that Pcerner is much nearer the truth, when he fays, that the beft pro- portion for diflblving indigo is only four times its weight of good pure oil of vitriol; and that where more is ufed, the blue is lefs permanent. I am even inclined to think that the blue will prove more durable, if this laft quantity of acid be diluted with an equal portion of water as foon as the indigo is put to it, and the mix- ture left in a warm fituation 48 inftead of 24 hours for the indigo to diflblve j becaufe, by a flower and more moderate action, I think the bafis of the indigo will be lefs weakened ; at lead I have frequently difTolved indigo in this way, and the colour has appeared to be more durable than when it was difTolved by an undiluted acid. Perhaps even a farther dilution might ftill leave the acid of fufhxient force for diflblving the in- digo perfectly. But this I (hall endeavour to af- certain hereafter by more accurate experiments than I have yet made. The indigo being dif- folved, Mr. Pcerner adds as many ounces of K 2 dried i 3 2 PHILOSOPHY OF dried pot-afh as there were of indigo in the fo- lution, which produces an effervefcence ; and after twenty- four hours, he adds eight pounds and an half of water for each pound of oil of vitriol employed; and puts the whole into a glafs vefTel for ufe. Inftead of pot-ahh, I have ufed clean chalk, and this even in fuch quanti- ties, as to faturate the vitriolic acid. The in- digo was then precipitated with the chalk, and being collected in a folid mafs, it was ftill capa- ble of dying a blue on wood, though it took much more flowly than in the ordinary way of dying Saxon blue, in which the colour applies itfelf fo rapidly to wool or woollen cloth, as to render it difficult, with the utmoft care, to pre- vent its taking unequally ; a defect which might probably be obviated by a fmall portion of chalk. It is to prevent this, that M. d'Ambourney ad- vifes, where deep Saxon blues are wanted, to pafs the cloth at different times through veffels con- taining only what might fufHce for weak colours, in order that the blue may, by thefe partial appli- cations, be made to take with more evennefs. Silk, dyed along with wool, takes a much weaker co- lour, (I mean with the addition of chalk,) becaufe it has lefs affinity with the indigo than wool has. This preparation of indigo, however, would not give a deep blue, becaufe being united with fo laige a portion of white calcareous earth or lime, the blue colouring particles could not be fuffici- ently condenfed for that purpofe. Pcerner con- ceives the Saxon blue to be rendered more durable by previouOy preparing the cloth with allum. The folution of indigo by fulphuric acid, is ufually called by dyers chymical blue. It ought, how- ever, according to the new nomenclature, to be termed ■ ■■■^>^-J PERMANENT COLOURS, &c. 133 termed fulphate of indigo ; a name by which I fhall hereafter diftinguifb it. When applied to wool, the blue colour is much more perma- nent than while in a fluid date j for though a little manganefe, added to the fulphate of in- digo, inftantly changed its blue to a brown co- lour, wool, which had been previously dyed blue with fome of the fame preparation, was not dif- coloured by the action of manganefe difiblvcd in fulphuric acid. I do not know that a black was ever produced by the fulphate of indigo, or by any other preparation of that drug alone. Mr. John Wilfon, who has greatly contributed to improve the art of dying at Manchefter, maintains, that though a redundance of colouring matter will increafe the force and body of a colour, yet that no repeated dyings of blue will become black. I have, however, now before me two pieces of cloth, one of which is the deeped and pureft black per- haps ever feen, and was dyed by me, very lately, from fulphate of indigo, employed alone, though in an unufual quantity ; the other is of a fine Saxon blue, and was cut off from the firft, before it had taken up fo much of the blue colour as to be- come black. I lately found alfo, in making the topical blue, that a fmall piece of cotton, which I had thrown into the mixture, and which, being forgotten, had remained there forty-eight hours, was, when taken out, of a full black, fo perma- nently fixed, that neither lemon juice nor alkalies feemed capable of impairing it. I could not in one or two trials afterwards fucceed in producing a fimilar black on linen or cotton ; and it muft be remarked, that when I produced that which is the laft mentioned, it was in a mixture where I had K 3 at » 3 4 PHILOSOPHY OF atfirftputfome manganefe, to fee whether it would promote the diflblution of indigo ; and finding it did not, I had afterwards added more than the ufual proportion of orpiment, one or both of which additions may have contributed to the black in queftion. The fulphuric acid, or oil of vitriol, as com- monly prepared, contains a fmall portion of the nitric, which, however fmall, neceflfarily does fome harm in forming the fulphate of indigo. Mr. Chaptal obferves, that he has feen the co- lour fail, and the {luffs intended to have been dyed fpoiled by this fault in the fulphuric acic} employed for that purpofe, which ought there- fore to be guarded againft as much as pof- fible. The indigo of all others mod preferred for Saxon blues, is the blue or Flora of Guatamala, which indeed is fcarce ever employed for any other fpecies of blue, at lead in this country. The other kinds, and efpecially the copper, when mixed with oil of vitriol, efiervefce fometimes very ftrongly, in confequence of the extrication of fixed air, the prefence of which may eafily be accounted for, by recollecting that lime is frequently employed to accelerate the feparation and precipitation of the minute par- ticles of indigo, while in the veflels called beaters : and here it will be proper that I mould offer fome conjectures on the caufe of the dif- ferent colours of indigo i and as a foundation for thefe, I muft remark, that the flora or blue indigo of Guatamala is much lighter than the violet* PERMANENT COLOURS, &c. 135 violet, and that this lafr is lighter than the cop- per-coloured. From the lightnefs of this blue in- digo, and from its not effervefcing with acids, when diffolved by oil of vitriol, there is the ftrongeft reafon to conclude that no lime is em- ployed to accelerate the feparation and precipi- tation of its colouring matter in the beaters ; fince if there had been any, it would have in- creafed the fpecific gravity of the indigo, and by abforbing carbonic acid, would neceffarily have caufed an efFervefcence in making the ful- phate of indigo : taking it therefore for granted, that no lime is employed to feparate and preci- pitate the colouring matter, it would neceflarily follow, that, to obtain fuch feparation and preci- pitation, the agitation muft have been continued longer than would otherwife have been neceffary, and the unavoidable confluence would have been the combination of a larger proportion of oxygene with the colouring particles fo expofed to it, than what takes place with thofe feparated by lime : it will therefore follow, that indigo, ob- tained in this way, will contain a greater por- tion of oxygene than the other; and it feems natural to conclude that the blue colour is occa- iloned thereby. To afcertain, however, the juftice of this conclufion as far as I was able, I took fome of the lighted and blueft Guatamala indigo, and diflfolved it by lime, pot afh, and orpiment, as ufual ; one effect of fuch folution we know to be the taking away from the indigo a confiderable part, at leaft, of its oxygene ; and I accordingly found, as I have done in all cafes where indigo was diffolved for the topical blue, that the diffolution was accompanied with a bright mining copper- coloured pellicle upon the K 4 furface Hi '36 PHILOSOPHY OF furface of the liquor, which of itfelf was of a greenifh yellow underneath. The production of this pellicle may be eafiiy explained by re- collecting that the difiblved indigo, which has loft its oxygene, and become thereby of this greenifh yellow, being at its furface in imme- diate contact with the oxygenous gas of the at- mofphere, regains apart of what it had loft, and thereby becomes copper- coloured j but fwim- ining as it does upon a mixture difpofed to at- tract oxygene, it cannot in this ftate acquire and keep fo much thereof as the indigo kfelf for- merly had while it was of a blue colour ; and therefore, fo long as the body of the liquor re- mains yellow or green, the pellicle covering it will be only copper- coloured, though confuting of a colouring matter which was formerly blue, and which would have become fo again, if, be- ing difiblved, it had been thinly applied to lin- nen or cotton, and brought fufficiently into con- tact with the oxygene of the atmofphere. As therefore this blue indigo had apparently become copper- coloured, only by having lefs oxygene than before, is there not from this circumftance an additional reafon to conclude that the copper- coloured indigo, feparated and precipitated by lime, is made of that colour only by its pof- feffing a fmaller proportion of oxygene than the blue indigo? — We might naturally expect, if the difference of colour arifes from this differ- ence in the proportion of oxygene, that the blue indigo would fuit beft for the fulphate of indigo, becaufeit is to be difiblved by a farther application of oxygene contained in the oil of vitriol j and this is found to be the cafe, as was lately obferved : and on the other hand we fhould fuppofe the copper- PERMANENT COLOURS, &c. i 3T copper-coloured indigo to be beft fuited for the indigo vats and for the topical blue, becaufe in thefe the diflblution is effected by taking away oxygene; and the lefs there is of it, the more eafily will this be effected ; and here alfo the choice and practice of the dyers accords with this hypothefis, as they constantly employ the cop- per-coloured indigo for thefe laft purpofes.— But though the blue indigo of Guatamala is the lighted and moil valuable, becaufe its colouring particles are not intermixed with lime, and are but in a fmall degree mixed with other matters which might give it weight and bulk without contributing to its tingent powers, yet this is not the cafe with all blue indigo ; for in mod coun- tries it is now an invariable practice to precipi- tate indigo by lime-water ; and as a defire to ex- tract: as much of it as poflible from the plant, very frequently induces the operator to carry its fermentation in the fteepers too far, by which the colouring matter acquires an undue portion of oxygene, fo as afterwards to appear blue, even when precipitated by lime-water; and as this matter is moreover deb'afed by being mixed with other vegetable fubftances, extracted from the indigo plant by too much fermentation without affording colour, it happens that indigo of very inferior qualities often appears blue. Bergman, Quatrenere, &c. have endeavoured by analyfis to afcertain the component parts of indigo ; and M. Berthollet has given a fufficient account of the refults of their operations j from all which, corrected by more recent difcoveries, jr. appears, that pure indigo confifts of a confi- derable BH H 138 PHILOSOPHY OF derable portion of hydrogene, a little azote, about one-thirtieth of its weight of iron, a very large proportion of the bafis of charcoal, and a confiderable one of oxygene ; which kft, I con- ceive, in theie operations to have become united to the carbonic bafis, and to have converted it into charcoal. M. Berthcllet afcribes the per- manency of the colour of indigo to its abun- dance of charcoal ; and he clearly expofes the error of thofe who have attributed its colour to the very fmall portion of iron contained in it. The ftability and difficult folubility which the colouring matter of indigo acquires by com- bining with oxygene, feem to refemble, though in a lefs degree, what the bafis of charcoal ac- quires by a like combination j but in this laft the oxygene is fo much more intimately com- bined, that it cannot be feparated by the means which feparate the oxygene from indigo, in mak- ing the topical blue, as I have found by re- peated trials upon charcoal, and therefore it can only beaded upon in the laft of the two ways of diflblving indigo 5 I mean by the farther ap- plication of vital air, fo as to convert it into, carbonic acid gas. The firft mention of indigo, as known in this country, which I have obferved, is in the aft of the 23d of Queen Elizabeth, cap. ix. where it is called " Ancle^ alias Blue Inde." The Genipa Americana, Linn, is a very wide- ly-branching lofty tree, growing fpontaneoufly in different parts of Guiana and Brafil, where it is known by different names ; in Surinam by that of tapouripa ; in Demerary by the name of launaj r PERMANENT COLOURS, &c. i 3<) launa; and in Brafil, according to Marcgrave and Pifo, by the names of janipha, janipaba, &c. It bears a fruit nearly oval, of the fize of a large lemon, covered with a greenifh afh-co- loured fkin. This fruir, when ripe, afTumes very nearly the appearance and texture of a ripe medlar or a baked apple ■, and being replete with a moderately acid juice, is fometimes eaten to quench thirft. The fubftance of this fruit, while unripe, is hard, colourlefs, and fomewhat bit- ter ; and when cut open there is found in the centre of it a number of feeds in a fmall cavity, furrounded by a foft pulp, the furface of which has a flight blue tinge, probably occafioned by air collected in the cavity where the feeds are placed. Being at Surinam in the year 1770, I took fome of this pulp, and prefiing the clear colourlefs juice upon pieces of white linen and cotton, I found that, though the fpots wetted therewith at firft (hewed no colour, yet being hung up to dry, in lefs than twenty-four hours they had acquired a deep ftrong blue, very much refembling that dyed with the ifatis or woad. This blue I tried in vain to difcharge, or even weaken, by a multitude of wa(hings with foap and water, by the application of lemon juice, and by long expofure to fun, air, rain, &c. in a climate where at leaft the firft of thefe agents exerts the mod powerful action upon colours ; and by repeated trials I convinced myfelf that the blue obtained from this fruit, even by the moft fimple topical application of it, was as per- manent as any obtained from the indigo plant. This blue has long been ufed by the favages of Guiana, Brafil, &c. for painting their fkins of 140 PHILOSOPHY OF of a dark blue or violet colour, as (according to Csefar) the woad was ufed by the ancient Gauls and Britons for the fame purpofe. Dur- ing my firft refidence in Guiana, in the years 1-763, 4, 5, and 6, I had often obferved the native inhabitants of that country ftaining their bodies with this colour, which was ufually con- tained in calabaihes or gourds, in which they had previoufly macerated the fruit of the genipa, or its pulp, with water for Tome days before. I had myfelf ftained my fingers with it, and found that I could not remove the colour in any de- gree by warning, though after nine or ten days it gradually difappeared, doubtlefs by an abra- fion or wearing away of the fubflance of the cuticle to which it adhered ; but at that time I did not attend much to the manner in which this happened, and fuffered myfelf to adopt an opinion generally prevailing in that country, that this colour would in all cafes fpontaneoufly dif- appear at the end of eight or nine days j an opinion which had been propagated by Clufius, Pifo, Marcgrave, Hernandez, Rochfort, and others ; and which muft, as I am now per- fuaded, have originated from the circumftance of its ufual difappearance at thofe periods when applied to the human fkin, by an abrafion thereof. It was not until my fecond vifit to Guiana that I firft thought of the application of this blue to the purpofes of dying and callico printing ; and though I did not then remain long in that coun- try, and had no opportunity of feeing this blue prepared or applied by the favages, who have much lefs intercourfe with the inhabitants of Surinam (where I alone refided) than with any PERMANENT COLOURS, &c. 14s of the neighbouring colonies, I made a fuffi- cient number of experiments to afcertain, be- yond all pofiibility of miftake, that the fruit of the genipa affords, not a fugitive colour, as had been and probably now is univerfally believed, but a ftrong permanent blue fimilar to that of indigo, both in its nature and in the means by which it becomes vifible ; I mean by the ab- forption of oxygene : and when I confider the magnitude of the genipa tree, together with the quantity and fize of its fruit, I cannot help think- ing that plantations of it would prove highly beneficial, on account of the blue dye which the fruit would afford, either in the form of indigo by maceration, &c. or when gathered, cut, and dried, fo as to prevent putrefaction, and admit of their conveyance to Europe. A gentleman of character and fortune, who refided lome time in Bengal, and was the proprietor of a large eftablifhment for callico printing in that coun- try, being returned from thence about three years fmce, favoured me with a piece of indigo of a very good quality, which he afiured me was obtained from an Eaft Indian tree, one of the leaves of which he at the fame time (hewed me j and from its appearance, as well as from other circumftances, I have very little doubt but it is of the fame fpecies as the Genipa Americana -, more efpecially, as there is a tree growing plen- tifully on the coaftof Malabar, and defcribed in the Hort. Malabar, by the name of panitsjica- maram, which appears in every refpecl to re- femble the genipa, excepting that the authors of that work have omitted the mention of any co- jourjng property in tiie fruit of the Malabar tree, an Ui PFIILOSOPHY OF an omiflion which may have proceeded from fe- veral caufes. During my lad fhort vifit to Guiana, I did not find any of the fruit of the genipa perfectly ripe, and my experiments were neceffarily made only upon thofe which, though they had nearly attained their full growth, were hard and appa- rently colourlefs. Whether the foft juicy pulp of the ripe fruit is more or lefs effectual than the pulp of the unripe fruit for giving colour, I know not ; nor do I recoiled whether the ra- vages of Demerary and Eflequebo, in prepar- ing this colour, macerated the pulp of the ripe or the unripe fruit for that purpofe. I have, iince my return to Europe, been informed that the bark and leaves of the genipa tree, by ma- ceration, afford a blue like that of the fruit. Should this prove true (which feems probable), it would doubtlefs render the cultivation thereof very profitable. Hogs and other animals, feeding upon the fruit of this tree when it falls fpontaneoufly on the ground, are faid to have their bones ftained with its colour, as happens to animals feeding upon madder, and fome other colouring mat- ters. Mr. Martin Lifter (in the Vlth Vol. of the Philofophical Tranfactions, page 2132,) men- tions that " the feed hulks of glaftum fylveftre, tc old gathered and dry, being diluted with wa- " ter, (lain a blue, which upon the affufion of " lye ftrikes a green, which green or blue,- be- 8 « ing ,v*- : <:-.-« : -*J *<.jk.>/. -,•»■£-, PERMANENT COLOURS, &c. 143 Cf ing touched with the oil of vitriol, dyes a pur- ;.,^'i:Ju-^, ; PERMANENT COLOURS, &c. 147 fllrub indeed furnifhes a remarkable inftance, to (hew how little can be difcovered refpecting the colouring properties of plants from their external appearances. A fimilar inftance lately occurred to me in the wood, bark, and root, of the Zan- toxylum clava Herculis, Lin. (the tooth-ach tree, or japan pepper tree,) every part of which is ftrongly coloured of a mod beautiful yellow ; but having procured fome of it for trial, I could extract but little colour from it, notwithstanding its feeming abundance of tingent matter; and the little which I did extract, was like that of the Berberis, utterly incapable of forming the lead union with any bafis, or of refilling the action of air, or of foap, in any degree. The feeds of the BixaOrellana, (growing fpon- taneoufly in different parts of Guiana,) are co- vered with a reddilh pulp, which is collected and fent to Europe in different forms, under the names of annotta, arnotta, and roucou. It is princi- pally employed for dying filk, and fometimes for cotton ; though its colour, by all the ways and means of applying it hitherto difcovered, is fo fugitive, that perhaps it would be better if it were never employed even for dying filk. It partakes fo much of a refinous nature, as to diffolve but very imperfectly in water; and therefore at leafi an unequal weight of pot-afh. is employed to render it loluble in that vehicle, and afterwards the filk or cotton is dyed therein without any aluminous or other bafis*. The * The liquid fold in different parts of the town, under the name of '* Scott's Nankin Dye," appears to be nothing but annotta diffolved by pot-am in water. L 2 colour i 4 8 PHILOSOPHY OF colour of annotta becomes lefs red, and more inclined to the orange, when feparated from the feeds by maceration, in water, as is ufually prac- tifed; and by the addition of pot-afh, it is made to incline ftill more to the yellow hue. This laft change may, however, be readily overcome by adding any of the different acids to the dy- ing liquor, after fufficient colour has been taken up by the filk or cotton dyed therein ; though argol or tartar is generally preferred for this purpofe, becaufe it not only raifes the colour, but leems to render it a little more fixed. It is remarkable, that though the colour dyed with annotta fades very fall by expofure to air, it pow- erfully refills foap, and the action of the ftrong- eft acids. And it certainly affords one, among feveral inftances, of colours which decay by caufes very different from combuftion; becaufe linens and cottons dyed in the ufual ways with annotta, and afterwards wetted with oxygenated muriatic acid, inftead of fuffering a diminution of colour, were enabled by it to bear expofure to the weather longer, and with lefs injury than pieces of the fame dyed linens and cottons, to which none of the oxygenated acid had been applied, as I ebferved on repeated trials : and when we fee that the colours of indigo and madder, the molt durable of all thofe given by the art of dying, are ipeedily deftroyed by this oxygenated acid, and that it has no fuch de- ih'uctivc action upon fome of the mod fugitive of all dyed colours, (fuch as that of annotta,) we certainly mult conclude, that the colouring mat- ter of this Iaft.'fubftanee is conftituted very dif- ferently from that of madder and of indigo^ and iuiceptible of being preferved as well as de- ftroyed PERMANENT COLOURS, &c. 149 ftroyed by very different means. The deftruc- tion, therefore, of all dyed colours, cannot juftly be imputed to any fingle caufe, be it com- buflion or any other ; nor ought we to confi- der the oxygenated muriatic acid as acting on colours in the fame way as air, when one pre- ferves what the other deftroys. The frefli pulp of the Bixa Orellana taken immediately from the fhrub whilft growing, and applied to cotton without the addition of any alkali, feemed to afford a colour more laftingand higher, or more approaching to the red, than what can be dyed from the pulp feparated by maceration, as is done in producing the common annotta. The greateft confumption of this article, at lead in Great Britain, is, in giving a kind of yellowifh orange to cheefe, for which it is very iuitable, becaufe it is harmleis, and nearly taftelefs. TheLawfonia inermis of Linn, has long been tffed throughout India, Perfia, Arabia, Egypt, and in many other parts of Africa, for giving a reddifh (lain to the nails, lips, &c. It is the Liguftrum iEgyptiacum of Profper Alpinus, and the Hinna of the Arabians. Sir William Jones relates, that being at the iQand of Hinzuan or Johanna, and obferving a very elegant fhrub, about fix feet high, not then in bloffom, he learned that it was the " Hinna," of which he had read fo much in Arabian Poems. 11 Mufa (one of the inhabitants, fays he) « c bruifed fome of the leaves, and having " moiftened them with water, applied them to . PERMANENT COLOURS, &c. 159 linen or cotton, and combining with the foap, which it curdles, feems to form with it a kind of green paint. In this refpect, however, the folution of cop- per by ammoniac, (volatile alkali,) differs I be- lieve from all the other folutions of that metal ; for when it is applied to linen or cotton, though, by abforbing oxygene it foon lofes its fine blue colour and becomes green, yet foap in warning does not feparate or difcharge the ammoniated calx, except by very flow degrees ; fo that, with care, it will refift a great number of warnings without much diminution of its colour; and as it fuffers nothing from the action of air, I think it might be advantageouily employed, particu- larly on fine muflins, as affording a very delicate though pale fubftantive green, and efpecially fince in this way it may be applied fo very rea- dily and conveniently. Water fllould be made todiffolve as much ammoniac as it can for this purpofe, and the folution mould be fully fatu- rated with copper; after which it mud be fuffi- ciently thickened with gum, and kept in bottles, clofely (topped, pouring it out by a little at a time when wanted for penciling. I have fome- times thought the colour fomewhat improved, when, inftead of diflblving copper in its me- tallic ftate, I diflblved the nitric calx of that metal by volatile alkali ; but' at other times this fuppofed improvement has appeared doubtful. Subftantivc copper- greens have fometimes been dyed from fulphate of copper with lime and foap fuds, employed fo as to precipitate the particles of copper upon the ftuffs intended to be dyed ; but the colour given by thefe means is i6o PHILOSOPHY OF is fo fugitive, that it deferves no farther no- tice. There are feveral of the other metals and femimetals which, when precipitated or depofed upon animal and vegetable fubftances, in a kind of middle ftate between the metallic and the oxidated, combine therewith, and produce very durable fubftantive colours. To effect this pre- cipitation, it is neceflary that the feveral me- tallic oxids Ihould be deprived of a confiderable part of their oxygene j and this happens to them more readily, when applied to wool, (from its animal nature,) than when applied to filkj and when applied to the latter, (from its mixed na- ture,) more readily than if applied to linen and cotton. But vegetable fubftances are eafily ren- dered capable of producing this effect, by firlt impregnating them with either animal, alkaline,. or inflammable matters ; for which reafons will readily occur, after what has been heretofore fo often explained. In thefe cafes, light frequently concurs with the matters lad mentioned, to haften a feparation of the oxygene. Hailot. qblerves % that characters traced on writing-paper with a diluted nitro- muriate of gold, began after a few hours expofure to the air, (he probably fhoukl have laid light,) to manifelt colour, and ioon after became of a veiy dark viulet — £C violet " force prefcjiie noir." But when (hut up in a dole box, he fays, the writing did not become vifible during feveral months. And he adds> that the like happened to characters written with a diluted nitrate of filver, though they became very vifible in the fpace of an hour when e^~ * Mem. de TAcad. R. i-c. 1-37; 3 3 poled PERMANENT COLOURS, kc. 161 pofed to the fun's rays. See Mem. de l'Acad. R c desScien. de Paris, 1737. Dr. Brugnatelli (Ann. de Chymic, torn, iii.) alfo mentions, that characters written with a fo- lution of gold become of a fine purple when ex- pofed to the vapour of fpirit of wine (which de- prives them of oxygene), and of a deep red co- lour in the hepatic or fulphureous inflammable air. Every one who has had much occafion to han- dle the nitro-muriatic folution of gold, will pro- bably have found his fingers fometimes ftained with it of a fine reddifh purple colour. This has happened to mine very often, and nothing " but the wearing off or abrafion of the fkin would ever remove it. By impregnating linens, cot- tons, and filk, with animal, inflammable, alka- line, and fome other matters, they are enabled to receive fine durable purples by the like fo- lution. The yolk, as well as the white of egg, having been beat up with water and a little fugar, I (baked fome muflin therein, and when dry, applied a diluted nitro-muriate of gold to it, to- pically, which produced a very fine ftrong pur- ple. Cotton, impregnated with lintfeed oil, re- ceived from the like application a ftrong violet colour, as it did when impregnated with foda, and acidulous arfeniate of pot-afh (Macquer's arfenical neutral fait) : being impregnated with foda, fulphure of pot- alii, and fugar, the cotton received an olive brown by the fame applica- tion ; and a blackifh brown, when impregnated with alcohol and liver of fulphur. Having foaked cotton and filk in a diluted muriate of M tin, l62 PHILOSOPHY OF I tin, I plunged them into water which contained a little powdered chalk, and preffing out the wa- ter, dried them ; this being done, I applied to them topically, by the pencil, a diluted nitro- muriate of gold, which produced, wherever it was applied, a ftrong lively purple colour, ap- parently of a very durable nature. This effect is fimilar to that which takes place when the fo- lutions of gold and tin are mixed together, and the metallic oxides having a ftronger attraction for each other than for their acid folvents, unite, and, by reafon of their gravity, precipitate toge- ther in the form of a purple powder, which con- fills of both of thefe oxides, though the colour is wholly owing to that of the gold. Leeuwenhoek mentions (Philofoph. Tranfach Vol. xxiv.), that by touching nitrate of filver, his fingers were ftained black ; and that finding it impoffible otherwife to remove the ftain, he cut off and burnt the fkin, and then examining it by a microfcope, he found the filver revived in a multitude of little globules. — " I have ly- ** ing on my defk (continues he), a linen hand- " kerchief, which was ftained with aqua-fortis, fC impregnated with filver, with a large black " fpot about as large as a fhilling •" and he adds, that having ineffectually tried to difcharge the colour by fix warnings, and by laying the handkerchief out to bleach, he cut out the ftained part, burnt it to coal, and viewing it by a microfcope, law thoufands of fine filver glo- bules therein. The effect here mentioned to have been produced upon the fkin, accords with that which folutions of filver are known to pro- duce in blackening hair, and other animal fub- ftances ; PERMANENT COLOURS, &c 163 fiances ; but in reading this account, I thought it extraordinary that clean linen, impregnated with no animal, inflammable, or alkaiine mat- ter, fhould fo far deprive nitrate of filver of its acid, as to produce the effect defcribed; and I repeated the experiment feveral times without luccefs. At length, however, I took a filver tea-fpoon, which had flood half filled with aqua- fortis for feveral weeks, and which on the hol- low infide was become almoft black by it, and by the oxygene of atmofphere which it had at- tracted, and having poured out the more fluid part of the folution, I rubbed a bit of cambric againft the wet oxidated hollow furface, and hanging it up for a few days in the open air, on the funny fide of a wall, I found the cambric permanently ftained of a very dark violet co- lour. A fine piece of cotton, however, by the fame means received but a very flight difco- joration. Though cotton, when impregnated with foda and the acidulous arfeniate of pot-afh, received a ftrong durable (late colour by being touched with diluted nitrate of filver ; a drab colour by the fame means when impregnated with foda and fugar; a dark olive brown, with fulphure of pot-afh (liver of fulphur), and fpirit of wine; the fame with foda, liver of fulphur, and fugar; and being impregnated with white of egg, beat up in water with fugar, the cotton received from the nitrate of filver a very ftrong brownifh black; and when cauftic vegetable al- kali was added, it became a little blacker. The yolk, inftead of the white of egg, produced nearly the fame effect. All thefe colours were often wafhed, and expofed for a long time to the weather, without being changed. M 2 The ^^ HHBBH I^ HHHBI ^^ H 164 PHILOSOPHY OF The oxides of mercury very eafily give up their oxygene, and therefore they are readily precipitated by the means before mentioned upon vegetable as well as animal fubftances, af- fording generally either black or dark colours., though of but little permanency, becaufe the refidue of their oxygene foon feparates, and the mercury recovers its fluid metallic form. Ni- trate of mercury applied to cotton, which had been impregnated with foda, produced at firft a yellow, which foon changed to an olive, and being wafhed with foap, to a full black colour; but after a few days expofure in the open air, it almoft entirely difappeared. On cotton, im- pregnated with foda and fulphure of pot-afh, it immediately produced a black, which, by warn- ing and expofure in open air, changed in about ten days to an olive, and foon after difappeared. On cotton, impregnated with fulphure of pot- afh and fpirit of wine, it alfo produced a black, which difappeared like the former; and with cauftic vegetable alkali it produced nearly the lame effect. With orpiment, diflblved by pot- afh, it produced a very deep black, which flood two or three weeks expofure to the weather ; af- ter which the mercury began to revive, and the colour to dilappear in fpots. Nitfo- muriate of Platina, applied to cotton and filk, impregnated with foda ; with foda and liver of fulphur; with foda and the acidulous arfeniate of pot-afh; with orpiment diffblved in pot-afh ; with liver of fulphur and alcohol; and with lintfeed oil, feverally, produced various purples, olives, dark and reddifh browns, moll of which appeared fufrkiently durable. Nitrate PERMANENT COLOURS, &c. 165 Nitrate of cobalt applied to cotton, impreg- nated with foda ; with foda and acidulous arfe- niate of pot-afh ; and with cauftic vegetable al- kali, produced lively pink and rofe colours, which ftood warning and expofure to weather for a confiderable time. The oxide of cobalt, diffolved by muriatic acid, and applied to cotton impregnated with foda, when held to the fire exhibited the molt beautiful green, which, as the cotton cooled, changed to an apple- green j then pafied through all the fhades of yellow, and became a kind of pale buff colour, which the oxide retained after the cotton had been wafhed with foap; but then on being heated, it was found to have loft the property of becoming green, though on dipping it into a diluted muriatic acid, it immediately regained and exhibited the fame property. Thefe effects are connected with thofe which fimilar fo- lutions of cobalt produce as fympathetic inks ; though I confefs myfelf difiatisfied with all the explanations hitherto given of them. Perhaps I may offer another hereafter. The prefence of muriatic acid is effential to their exiftence, the nitrate of cobalt producing no fuch phenome- non ; nor did I find that the prefence or abfence of light had any effect in retarding or promoting any of the changes of colour here mentioned. The nitrate of nickle applied to cotton im- pregnated with foda and fugar, produced a green, but not fufficiently durable to be of any jjfe in. this way. M Nitrate i66 PHILOSOPHY OF Nitrate of manganefe by fome of thefe im- pregnations produced different browns, which kerned to poffefs confiderable permanency. I could add the refults of feveral other ap- plications of this fort, but at beft they would only prove to be what Bacon Lord Verulum has termed Experiments of light rather than of fruit ; and indeed this may be the cafe with many of thofe which I have juft related. It would not, however, be the cafe of thofe which regard the application of gold as a fubftantive colour, if the dearnefs of that metal were not an obftacle to its ufe in this way ; fince the beauty of its purples and violets, and the facility of applying them topically and permanently by the pencil to fine muffins, filks, &c. would otherwise render them very defirable and ornamental. It is doubtlefs on principles fimilar to thofe before mentioned, that fome ccmpofitions which afford very durable black colours for marking on linen, &c. are now made and fold in London. Soda, diifolved and thickened by a little ifinglafs, or fome animal mucilage or glutinous matter, is probably firft applied, and, when dried, names or letters are written thereon, with a pen dipped in particular metallic folutions. In the firft Volume of Ann. de Chymie, Mr. Berthollet obferves, that the fimple mixture of oxide of lead with lime, blackens wool, hair, nails of animals, and white of egg, but not lilk, nor fkin, nor the yolk of egg, nor animal oil; and that fome perfons ufe this mixture to render white or grey hairs black, firft flackening the lime. To try PERMANENT COLOURS, &c. 167 try Its effects in dying, I boiled flannel in lime- water with litharge, and found that it took a pretty full black, which flood wafhing with foap and expofure to the weather. Strong acids dif- iblved the lead, and changed the colour ; but the application of vinegar did not feem to do fo. The lime, however, weakened the texture of the wool considerably, as he has alfo obferved. Whe- ther this evil can be avoided by ufing it more fparingly, I have not yet afcertained. I found the mifchief greatly increafed by adding orpi- ment, which feems to produce a fimilar effect in thofe depilatory compofitions firft brought to Europe from Turkey. CHAP. VII. O/ ddjeffive Colours generally. *' Les faits font de tous les temps, ils font immuables, " comme la nature dont ils font le langage ; mais ** les confequences doivent varier felon l'etat des '* connoifTances acquifes." C H a p t a l Ekmens de Chimie-. ALL adjective colours owe their durability, and frequently their particular complec- tions, as well as their luftre, to the interposition of fome earthy or metallic bafis ; which, having a confiderable attraction both for the colouring matter, and the fibres of the ftuff about to be dyed, combines with and ferves as a bond of union between them. Thefe earthy and me- tallic fubftances, having been ufually employed M 4, in 1 68 PHILOSOPHY OF in a ftate of folution or combination with acids, were from that circumftance denominated mor- dants (biters or corroders) by the French, who indeed began to employ the term long before any thing like a true theory of dying had been conceived j whilft even allum was fuppofed to act by its fulphuric acid, and not by the pure clay upon which its ufefulnefs depends, and whilft in truth all the other matters called mor- dants were fuppofed to be ufeful only by their folvent or corroding powers ; and the term hav- ing been thus introduced, has been fince adopt- ed in other countries. The ingenious Mr. Henry of Manchefter has, however, lately ob- jected to it, with great reafon *, and propofed in its (lead to employ the term bafis, a term which feems defective only in as much as it does not exprefs that particular affinity, or power of attraffion, which manifeflly fubfifts between thefe earthy and metallic fubftances, and the feveral adjective colouring matters, as well as between the former and the fibres of wool, filk, cotton, &c. I con fe Is, however, that no other lefs objectionable term has occurred to me; and being unwilling to propofe new terms, without ibme cogent reafon, I fhall employ both the term of mordant and that of bafis; though not indifcriminately, in all cafes at leaft, fince I fhall generally ufe the former to fignify thefe earthy and metallic fubftances, when actually diftblved by fome acid, alkaline, or other folvent, and when of courfe they will commonly prove more * See his '< Confiderations relative to the Nature of « Wool, Silk, and Cotton, as Objefts of the Art of Dy- << ing, &c." in the third Vol, of the Memoirs of the Man- chefter Society. or ■ ,.v ■ ■ MHHHi PERMANENT COLOURS, Sec. 169 or lefs corroding or biting, according to the original meaning of the term. But the deno- mination of bafis will mod frequently be em- ployed to defignate the fame earthy and metallic fubftances, difti nelly and feparately from any acid or other folvent, either in relation to their proper- ties, when actually fixed in the pores or fibres of wool, filk, &c. or when it is not intended to no- tice any property which may more immediately refult from their combinations with any particular menftruum. Mr. Berthollet indeed gives the term mordant a much more extenfive fignifi- cation, as meaning all the different chymical agents capable of ferving as intermedia, be- tween the feveral colouring particles, and the fluffs to be dyed with them, either for the pur- pofe of affifting their union, or of modifying it *. This laft effect (of modification) may, however, be produced by a variety of matters befides thofe which are of the earthy or metallic kinds, and indeed by every thing capable, not of fixing, but of varying only, the fhades of ad- jective colouring matters. Thefe, therefore, I think it more proper to defignate, not as mor- dants or bafes, but as alterants , whofe ufe and application may in this refpect be extended to fubflantive as well as to adjective colours. The true natures and ufes of mordants or bafes for the purpofes under confideration, can, * " L'on donne le nom de mordant aux fubftances qui f fervent d'intermedes entre les parties colorantes & les " ctoftes que l'onteint foit pour faciliter leur combinaifon, " foit pour la modifier," Ek/ncns de V Art de Li Teinture, torn. i. p. ?6. I be- s 7 o PHILOSOPHY OF I believe, in no way be lb diftinflly manifefted, or fo clearly illuftrated, as by their effects in ■what I ihall call topical dying, or that fpecies of it by which different colours are communicated to particular fpots or figures, on the fame piece of cotton or linen, according to the feveral bafes previoufly applied thereto, and which prin- cipally conftitutes that truly wonderful art, the art of callico-printing. I mall therefore in this place bring under my reader's notice lbme of the more important operations of that art, re- verting at the fame time, as far as we can, to- wards its remote origin, in order to fee how and by what means it has attained its molt important improvements. Pliny defcribes the Egyptians as praclifing a fpecies of topical dying, or callico-printing, which, as far as can be difecvered from his ge- neral terms, appears to have been fimilar to that which, many ages after, was found to exift in Hindoftan and other parts of India, and was from thence introduced into this and other coun- tries of Europe. He fays, the Egyptians be- gan by painting or drawing on white cloths, (doubtlefs linen or cotton,) with certain drugs, which in themfelves poffeffed no colour, but had the property of attracting or abforbing colour- ing matters. After which, x\it\t cloths were immerfed in a heated dying liquor, and though they were colourleis before, and though this dy- ing liquor was of one uniform colour, yet when taken out of it foon after, they were found to be wonderfully tinged of different colours, ac- cording to the different natures of the feveral drugs ■ PERMANENT COLOURS, Sec. 171 drugs which had been applied to their different parts ; that thefe colours could not be afterwards difcharged by walhing, &c* Whether the Egyptians borrowed this won- derful art from the Hindoos and other inhabit- ants of India, or whether the latter borrowed it from the Egyptians, is a queftion which proba- bly may be anfwered without much difficulty, if we confider the many reafons which there are for believing that this art has been practifed over the greatefl part of India during a long fuc- cefTion of ages ; that not only the art itfelf fub- fifted there, but that the colouring, and other materials for exercifing ir, were the natural and peculiar productions of that country rather than of Egypt ; that the Indians were highly civilized at leaft twenty-two centuries ago, during which fpace of time their manners, fanftified (if I may fo exprefs myfelf ) by being connected to their religion, fuffered little, perhaps no change ; and their trades were carefully perpetuated in parti- cular families ; and alfo that among thefe their manufactures were undoubtedly of very great antiquity, whilft obvious ways, by which they * " Pingunt et vcftes JEgypto inter pauca mlrabili ge- " nerc, Candida vela poftequam attrivcre illinentes nort " coloribus, fed colorem forbentibus medicamentis. Hoc *' cum fecere non apparet in velis fed in cortinem pigmenti " ferventis merfa, poll momentum extrahuntur pifta. Mi- " rumque cum fit unus in cortina colos, ex illo alius atque " alius fit in vefte accipientis medicamenti qualitate mu- " tatus. Nee poftea ablui poteft. Ita cortina non dubia " confufura colores fi piclos acciperet, digeret ex uno, pin- " gitquc dum coquit. Et adufta? vefles firmiores fiunt " quam fi non urerentur." Pi in 11, 1. xxxv. fed. 42. fol. 789. might 172 PHILOSOPHY OF might have been eafily extended to Egypt, and other countries, undoubtedly exifted long before the time when Pliny wrote. Major Rennell obferves, that " a pafiion for " Indian manufactures and products has actuated " the people of every age, in lower Afia, as well 5£ as in the civilized parts of Europe : The deli- " cate and unrivalled, as well as the coarfer and * c more uleful fabrics of cotton of that country " particularly fuiting the inhabitants of the tem- ■* perate regions along the Mediterranean and " Euxine feas. To this trade (continues he) tc the Perfian and Arabian Gulfs opened an eafy " paflagej the latter particularly, as the land cc carriage between the Red Sea and the Nile, •* and between the Red Sea and the Mediterra- one ounce of it for every pound of alum. Af- terwards the calico-printers, without any fyftem or reafonable motive, appear in different in- flances to have* added verdigrife, arfenic, cor- rofive fublimate, blue vitriol, litharge, and zvhite lead. By {tumbling upon the two lafh (which alone were of any ufe), it happened, where vinegar had been alfo employed, as it commonly was in fome fhape, that after a va- riety of decompofitions and recompofitions, fome portion of acetite of alumine was formed, the good effects of which were experienced, though without any true knowledge of the ways and means by which they had been produced. By degrees, however, the printers feem to have in- creased the quantity of fugar of lead, and feve- ral of them to have fufpected that many of the other ingredients ufually employed for making their mordants were ufelefs. Some of them, therefore, began to omit one, and fome another of thefe ingredients, until at length all the ufe- lefs ones were laid afide, though without the aid of any chymical reafoning on the fubje£t, and without any one ever fufpe&ing, as indeed few of them do at this day, that the lead which they continued to employ occafioned any decompo- fition of the alum, or that the mordant fo pro- duced did not really contain all the ingredients ufed in preparing it. Among the ufelefs ingre- dients before mentioned, corrofive fublimate fcems to have been retained the longed, fince Mr. Wilfon includes it in his recipe, which was N j publifhed 182 PHILOSOPHY OF publifhed fo lately as the year 1786. (See his EiTay on Light and Colours, &c.) It is not wonderful, therefore, that no parti- cular perfon or period has been noted, or re- membered as diftinguifhable for the firft in- vention of the acetated aluminous mordant ; fince the fugar of lead, or other means of form- ing it, were at firft ufed by chance fo fparingly, as to have fcarcely produced any better effect than would have refulted from the mere folution of alum, and the alterations and improvements by which the mordant afterwards acquired its pre- sent form, I had almoft faid perfection, were made by fuch imperceptible gradations, and re- fulted fo much from the random additions and omifiions of different individuals, (no one of whom feems to have been guided by any thing approaching to a juft theory,) that neither the difcovery, nor any confiderable Hep towards it, can properly be referred to any one perfon or period. Mr. Henry, juftly fenfible of the fuperior ad- vantages of the acetated aluminous mordant in calico-printing, and conceiving it to have really been very anciently known and employed in thofe countries where the art was firft practifed, concludes from thence, that it muft have re- fulted from a very advanced ftate of chymical knowledge in thofe countries at fome very re- mote period, which was afterwards loft, whilft the improvements arifing from it in this refpect, continued to be practifed and handed down, through a long fucceftion of ages to the prefent time. p PERMANENT COLOURS, Sec. 183 time. " To have invented (fays he) the pro- < f cefs of printing, in the manner defcribed by however, did not weaken the colour in any degree, nor was it injured by acids. A little time before this, M. le Pileur d'A- pligny announced to the world that he had dif- covered the means of dying a blue, as far ex- ceeding all other blues in beauty and luftre, as the cochineal fcarlec exceeds the common reds. He, however, kept his procefs fecret, until the offer of a premium induced him to make it public. He began it by impregnating the fluffs to be dyed with an iron bafis, which he prepared by deflagrating equal parts of old iron and falt- petre in a crucible, afterwards wafhing the re- iiduum and diffblving it in vinegar and bran- water. This being fufficiently diluted, was ap- plied as a mordant in the ufual ways to the ituffs, which were afterwards well rinced, and dyed in a preparation of Pruffian blue, made by difTolving two pounds thereof (in the moift flate in which it is firft precipitated) by half a pound of pot-afh, in boiling water, and afterwards adding three ounces of common oil of vitriol, or an equivalent portion of nitric acid, fo as to neutralize the alkali, without precipitating the colour. A fufEcient quantity of this put into a dying vefleli with hot water, and the fluffs, pre- vioufly impregnared with the iron mordant, be- ing dyed therein, they became at firft green, and afterwards of a beautiful blue colour j which was, however, flill liable to take unequally, and there- fore M. d'Apligny's procefs, as far as I can learn, has never been carried into any confider- able ufe. In PERMANENT COLOURS, &c. 203 In the thirteenth Volume of the « Annalcs de Chymie," (for April lad,) Mr. Berthollec gives an account of certain ideas which had oc- curred to him reflecting the defects of all the means ufed for dying with Pruffian blue, and of fome experiments made at his defire by Mr. Vidmer, of the celebrated calico-printing efta- blifhment at Jouy, tor correcting thefe defects. It was found by thefe experiments, that pieces of cotcon, impregnated with the acetite of aiu- mine or iron liquor, notwithstanding all poffible endeavours to apply it equally, took up the co- lour of Pruffian blue (firft diflblved by pot-afh, and then mixed with either fulphuric or muriatic acid) fo very unequally, as to leave no hope of fuccefs in this way. Mr. Berthollet accounts for this inequality of colour, by fuppofing that one part of iron is fufficient for fix of the Pruffian colour j and that therefore the flighted differ- ence in the diftribution of the particles of that metal in the mordant, becomes very fenfible when the Pruffian colouring matter is after- wards fuperadded thereto. Mr. Vidmer was particularly flruck with the greens which were produced with the Pruffian blue, upon patterns previously dyed olive in the ufual way by the iron liquor and weld, which greens greatly furpaffed in beauty all thofe given by any other means. Mr. Berthollet, by experiments which were afterwards made feparately from Mr. Vidmer, difcovered that the folution of Pruffian blue bf lime water (pruffiate of lime) fucceeded as well io6 PHILOSOPHY OF well as that by pot-afh, and that it required left care refpectir.g the proportions : but he thinks the alcaline folution will have the advantage of being afforded cheaper, becaufe when animal matters have been calcined with pot-afh, no- thing more will be necefiary than to faturate the excefs of alkali, by adding .to it a little Pruflian blue, Mr. Berthollet's method was to dilute the pruffiate of lime with three or four times as much water, or to dilute with a large quantity of water, a lmall one of the pruffiate of pot-afh, and then to mix with it a little fulphuric acid, and keeping the liquor at a heat of between twenty and thirty degrees of Reaumur's ther- mometer, to immerfe the cotton, linen, or filk therein, (having ftrft foaked it in warm water,) and turn it over a winch, &c. as ufual, in order that the colour might be equally applied. The dye was found to take fufficiently in a few mi- nutes, and then the fluffs were taken out and warned in cold water. He found the fulphuric acid preferable to the muriatic. Cotton and filk previoufiy dyed gray or brown, with galls or other nigrefcent vegetable colouring matters, applied to a ferruginous bans, acquired by the procefs juft mentioned a blue colour, proportioned to the depth of the former brown or gray ; and thofe which had been previoufiy dyed olive, by the application of weld, or other adjective vegetable yellows, took alfo a beautiful green, proportionate to fuch olive colour. He fays nothing of the ef- fect PERMANENT COLOURS, &c 207 feds of this method of dying on wool, having made fcarce any trials therewith. Cotton and filk dyed black by the ordinary- means, were found, by fuperadding a blue la Mr. Berthollet's method, to become more per- fectly black, as well where the original colour had faded, as where it had been but imperfectly produced at firit. He cautions againft ufing too much acid, as well as againft making the dying liquor too hot, and keeping the fluffs too long therein, efpecially the filk, which would thereby lofe fome of its luftre and foftnefs. One great defect, however, attending this me- thod of dying, efpecially upon cotton, is, that the fluffs, to which the PrufTian blue has been applied, will not bear waffling, becaufe, though the colour refills air extremely well, the alkali contained in foap readily dilTolves and feparates the Prufiian colouring matter. As a remedy for this defect, Mr. Berthollet recommends waffl- ing the cottons, dyed by his procefs, with bran and water, inftead of ioap, which, he fays, will likewife have the advantage of preferving the other colours of printed cottons ; or rather of not injuring them, as waffling with foap gene- rally does in fome degree. Among the effects mentioned by Mr. Berthollet, that which I thought the mod furprifing was, the change of what he (improperly) calls an olive colour, pro- duced by weld and iron liquor ', to a very beau- tiful green, by the application of Pruffian blue in the way before defcribed. The green in this inflance could not be produced without a mix- ture of yellow with the blue ; and weld, the only colouring. 20$ PHILOSOPHY OF colouring fubftance from which it could in this cafe be obtained, never would afford any fuch colour without the aluminous or fome other bafis very different from iron. I determined therefore, as foon as poffible, to afcertain the truth reflecting this point j and for this pur- pofe I took a large piece of cotton, which had been printed in parallel longitudinal ftripes, firft with a mixture of iron liquor and galls, next with iron liquor only 3 then with a mixture of iron liquor and the aluminous mordant (acetite of alumine) ; and laftly with the aluminous mordant only j then followed a white ftripe to which nothing had been applied, and thefe were repeated fo as to cover the piece. This I dyed in the ufual way with a deco&ion of Quercitron bark, and thereby the firft ftripe became black, the fecond of a dark drab colour, the third of an olive, and the fourth yellow. I then took a fo- lution of pot- afh, fully faturated with the Prufllan colouring matter, and poured fome of it into a large vefiel nearly filled with moderately warm water, to which I added a large proportion of oil of vitriol (fulphuric acid) : this, from its weight, funk to the bottom. I took care, how- ever, by ftirring, to mix it thoroughly with the Jiquor ; which became uniformly blue, and had a four tafte. I then tore off a ftrip of the dyed cotton of the whole breadth of the piece, and immerfed it for a fingle minute only in the li- quor; when, on taking it out, I found that every particle of the colouring matter of the galls and Quercitron bark had been difcharged, and re- placed by the Prufllan colouring matter upon the ftripes where an iron bafis had been at firft applied, nearly according to the quantum of that bafis. PERMANENT COLOURS, &c. 209 bfcfis* The firft flripe, therefore, inftead of be- ing black, was of a very full., deep* ftrOng blue colour ; the fecond was fufficientiy full, though very fenfibly weaker; and the third was *(tili weaker ; the fourth, to which the aluminous bafis only had been applied, was of a very pale bluifli colour, almofl: as flight as the fifth, which had not been impregnated with any bafis or mordant. To diminifh the excefs of fulphuric acid in the liquor, as well as to replenifh it with colouring matter, I added thereto a farther por- j» tion of prufliate of pot-aih, which being pro- perly mixed, I immerfed another ftrip torn from the fame piece of cotton, and taking it out alfo, after a fingle minute, I found that in this in- ftance the excefs of fulphuric acid had not been great enough to difcharge the colouring matter of the galls, though it had totally dilcharged that of the Quercitron bark. I had, therefore, inftead of a very dark blue on the firlt flripe, a very full black, greatly fuperior to what it had been originally, the black from galls and iron having become much more intenie by an additional body of blue colour. All the other ftripes were very fimilar to thofe of the preced- ing trial. I then perfectly neutralized the ex- cefs of acid in the dying liquor, by adding to it a fufficient quantity of prufliate of pot-am ; and a third ftrip of the fame cotton being put into it for the fame fpace of time, I found that none of the colouring matter of the Quercitron bark was difcharged in thofe parts where it had been united to the aluminous bafis, though- it ap- peared to have been decompofed and il-parated from the ferruginous, and its place lupplied by the colouring matter of the Pruffian blue. I P had 2IO PHILOSOPHY OF had therefore on the fecond itripe a blue colour, inftead of the drab which the Quercitron bark had produced with the iron liquor j and on the third (tripe, inftead of an olive, I had a very beautiful green, compofed partly of the yellow from the Quercitron bark and the aluminous bafis, and partly of the blue which the Pruffian colouring matter had produced on the fame ftripe, by uniting with the ferruginous particles of the iron liquor, originally mixed with the acetite of alumine, and applied as a mordant upon that ftripe. '1 he yellow upon the fourth ftripe remained in full perfection ; and the fifth ftripe was perfectly white, having been quite freed from a flight difcolouration which the Quercitron bark had produced on it in the dy- ing veftel. By this, and many fimilar experi- ments, made lome of them with weld inftead of Quercitron bark, I clearly perceived that Mr. Berthollet muft have been miftaken, when he fuppofed that the olives which were changed into beautiful greens in the manner before men- tioned, had been given by the weld and iron li- quor cnly y becaufe no fuch effect; can be produced either from that or any ether adjective vegetable colouring matter, without the aid of alumine, or of oxide of tin, to produce a yellow, whilft the ferruginous bafis, by attracting the Pruffian colour, produces a blue, the other component part of the green. I afcertained this fact more completely by extending my experiments to woollen cloth, of which Mr. Berthollet fays no- thing in this refpect. I began by dying pieces of white broad cloth, fome with weld and cop- peras, others with Quercitron bark and cop- peras, which in both cafes produced nearly the fame PERMANENT COLOURS, &c. 211 fame drab colours ; and the pieces being fa dyed, I immerfed diem in different portions of diluted pruffiate of pot-afli neutralized, with fulphuric acid, a little more than blood-warm, in which they all, after ten or fifteen minutes, became blue, the Pruflian colouring matter having decompofed and feparated that of the weld and Quercitron bark, which by fui table experiments I afterwards found to be contained^ in the feveral liquors where the PrufTian colour- 1 ing matter had before been fufpended. If in- flead of dying the cloth with weld or Quercitron bark and copperas only, I ufed alum along with copperas, an olive was produced ; and this being foaked as before mentioned in warm di- luted pruffiate of pot-afh, neutralized with ful- phuric acid, produced a green ; the alum and Quercitron bark or weld furnifhing a fufficient quantity of yellow for that purpofe. In all thefe and many other experiments I found, that though the Pruffian colour in this way readily decompofed and feparated moft of the adjective colours united to a ferruginous bafis, for which it has a ftrong attraction, it had not any fufrl- ciently ftrong for the aluminous bafis to feparate the colouring matters combined therewith : and hence in all cafes where a portion of alumine had been united with iron, to form the bafis or mordant, and an olive colour had been thus pro- duced by weld or Quercitron bark either upon cottons, filk, or wool, a green invariably re- fulted, from an application of the Pruffian al- kali with fulphuric acid, unlefs where this acid was made to predominate fo greatly as to decompofe, even that part of the vegetable co- louririg matter which adhered to the aluminous P 2 pare r n 2i2 PHILOSOPHY OF part of the bafis. By reflecting upon thefe fads, I was led to a method of applying the Prufllan blue for dying upon woollen, (ilk, and cotton, which feems to me capable of obviating every difficulty hitherto attending its ufe for thefe pur- pofes. I have already mentioned Mr. Bcrthol- Jet's opinion, that the inequality of colour to which the dying with Pruflian blue is liable, „arifes from the difficulty of applying the ferru- ginous particles alone equally to all the fibres of the cloth; though this may be eafily done, when the particles of the iron are combined with thole of different adjective vegetable colours ; i there- fore boiled up what I conceived to be fuitable proportions of copperas, with Quercitron bark, fuftic, and logwood feparately, and then dyed a piece of woollen cloth in each of thefe mix- tures, by boiling it therein for ten or fifteen mi- nutes ; I chofe thefe vegetable dying drugs, without any regard to their particular colours, only becaufe they were cheaper than any others, regard being had to their proportions of co- louring matter, and becaufe they do not con- tain any mixture of that particular fubftantive colouring matter found in galls, fumach, &c. which the Pruffian colour would be lefs capa- ble of decompofing and difcharging. The pieces fo dyed being afterwards feparately immeried in warm diluted prulfiate of pot-afh, neutralized by fulphuric acid, became all equally and beau- tifully blue. It muft, however, be obferved, that this does not always happen, becaufe when too much copperas is employed in the dying with Quercitron bark, &c. there will be an excefs of calx of iron applied to the fibres ot the wool, which, from its rulty yellow colour, 1 2 will PERMANENT COLOURS, &c. 213 will give the PufTian blue a greenifh tinge. This, however, may be readily difcharged, by patting the cloth through warm water, flightly Toured by muriatic acid ; tliough a few expe- riments would be fufficient to afcertain exactly the quantity of copperas neceffary for produc- ing any particular ihade of blue in this way up- on any given quantity of cloth, and thereby ob- viate all difficulty on this point. It is neceffary always to apply the PrulTian colouring matter in a moderate heat, otheiwife it will be preci- pitated by the lulphuric acid, and rendered unfit for this purpofe, unleft diiiblved again by pot- afh, lime, &c. I fhall offer fomething more reflecting the ufe of Pruffian blue for dying green upon wool- lens, when I come to treat of the properties of Quercitron bark. To afcertain whether any affinity exifted be- tween the aluminous baf;s and the colouring matter of Prufiian blue, I took a piece of cot- ton which had been printed with the aluminous mordant, and cleanfed as ufual for topical dy- ing, and immerfed it in warm diluted pruffiate of pot-afh j feeing, however, at the end of fif- teen minutes that it had acquired no colour, I put into the liquor a fmall proportion of a folu- tion of iron by muriatic acid, which rendered it blue, and the cotton foon became of that co- lour pretty equally, without any manifeft dif- ference of colour in the places to which the aluminous mordant had been previoufly applied. Taking the cotton out of this dying liquor, I tore off a bit of it, and warned it with foap, P 3 which ?I4 PHILOSOPHY OF which foon difcharged .ill the colour, excepting where the cotton had been impregnated with alumine, and there it was considerably weak- ened, though enough remained to (how that it was attracted and rendered more fixed by the aluminous bads. Another bit of the fame cot- ton was immerfed in a folution of ammoniac, (vol-alkali,) which having a power of de- compofmg the Prufilan blue, I fuppofed it would weaken, if not wholly difcharge the co- lour. To my furprize, however, I found it greatly augment the blue, which before had been rather pale, and give it almoft the appear- ance of what is called garter blue; an effect which will perhaps be the lefs furprizing, if we confider that volatile alkali, like the Prufilan colouring matter, is an animal production, and compofed of the fame principles, excepting only the carbone, which it wants, and which exifts in the latter. Another bit of the fame cotton being put into water, very (lightly tinctured with a folu- tion of copper by volatile alkali, the blue co- lour in a very fudden and furprizing degree aug- mented to an intenfely deep garter blue or vio- let, much exceeding that produced by the am- moniac alone ; and this being afterwards wafhed with foap, the colour of thofe parts where the aluminous mordant had been at (nit. applied, was Hill better fixed than it had been on the like parts by the volatile alkali alone in the preced- ing trial. Another piece of the fame cotton being im- merfed in water, with which a very little mu- riate of copper had been previoufly mixed, foon became PERMANENT COLOURS, &c. 215 became of a deeper blue, but without any of the purple or violet hue which had been pro- duced in the two preceding inftances. This piece being afterwards wafhed with foap, I perceived that the colour where the aluminous mordant had been applied was ftill much more firmly fixed than it had been by any other means. Indeed after a fevere warning, which completely difcharged the colour every where elfe, the fpots or parts impregnated with alumine retained a full ftrong blue, which the ibao had indeed turned a little towards a violet colour ; but after being well rinced in clean wa- ter, it returned again to its proper complexion, and flood a long expofure to weather unaltered, and afterwards two or three fevere wafhings with foap, without much diminution of colour*. It mud, however, be remembered, that if copper thus manifeftly fixed the Pruffian blue, it was only in thole parts where the aluminous mor- dant had been at fir ft applied ; fince the other parts of the cotton were warned white as foon as they were on the bit, to which nothing had been applied after it became blue ; fo that there can be no doubt but what both alumine and copper together greatly contribute to fix the colouring matter of Pruffian blue. The copper indeed, as we fhall prefently fee, pofTeiTes a power of uniting therewith, and producing one of the * In this and the other pieces the blue upon the fpots impregnated with alumine, after it had been weakened by warning, was rendered nearly as ftrong a.s ever, by dipping them in o water /lightly foured with fulphuric acid, fo as to decompofe and neutralize the alkali which had been im- bibed from the foap in wafhing. P 4 mod 2l6 PHILOSOPHY OF moft permanent of colours even upon linen and cotton j a fact which I believe never was ima- gined by any one, .until it very lately fell under my obfervation. From thefe proofs of the utility of an aluminous bafis in fixing the Pruffian blue, it probably would prove advantageous to prepare woollens by the ufual boiling with alum, or alum and tartar, before they are dyed with copperas and Quercitron bark, fuftic, or log- wood, for a Pruffian blue. But in this cafe it will be necelfrry to mix a greater proportion of oil of vitriol in the pruffiate of pot-am, or of lime, in order that there may be an excels of acid to aftift in dikharging thefe vegetable co- louring matters, otherwife inftead of a blue they would produce a green, or a black, where log- wood had been employed with the copperas. Having foaked pieces of filk and of cotton in the diluted prufTiatcs of pot-afh, foda, lime, and ammoniac, or volatile alkali, feparately, and afterwards dried them, I applied to each, by the pencil, a little of the folutions of all the metals and femi- metals in moft of the different acids and alkalies, where they were foluble in the lat- ter, in order to fee the -effects of all thefe feve- ral bales upon the Pruffian colouring matter. I fhould tire the patience of my readers, were I particularly to defcribc the i elults of thefe dif- ferent combinations, efpecially as no words can convey adequate ideas of the great variety of fhades and degrees of colour, and particularly of the blue produced by them, and which varied prodigioufly in its degrees of fullnefs and bright- fiefs, as well as in its inclination towards the purple and violet on one hand, and green on the other i PERMANENT COLOURS, &c. .217 other; and indeed the diversities of blue only, (which was the colour produced by much the greateft number' of metallic folutions,) would alone conliitute a very plealing variety of co- lour in the way of printing upon filk.or cotton. There were, however, feveral other colours pro- duced at the fame time; e.g. The nicro- mu- riate of gold produced very beautiful green, in- clining a iittle to the yellow, which, by warning, changed fomewhat to the olive, whilft the nitro- muriate of platina produced a green inclining to the blue. The muriate of tin, and the ni- trate of mercury, produced greenifh yellows, and the nitrate of nickle an olive brown. But the mole remarkable, and probably the moft ufeful effect of thefe applications, was, a very- full, finking, lively colour, of which I cannot by words give my readers a perfect idea, be- caufe I do not remember to have ever before ieen any colour exactly like it, and there is I believe no name in any language fuited to it. It approaches neareft, however, to the higheft and brighteft colour of new copper, but inclines more to the red, and is accompanied with a kind of metallic mining luftre, which in my eyes appeared very agreeable. This colour (which I (hall call the red copper colour, until a better name be given it) was produced by the different folutions of copper in the fulphuric, the nitric, the muriatic, and the acetous acids fe- paratelyj and particularly well by that in volatile alkali. Copper, however, was not the only metallic bafis which produced this colour, though it was the cheapen 1 , and therefore the moft fuitable for this purpofe. The nitrates of iiiver and of cobalt produced exactly the fame colour 2l8 PHILOSOPHY OF colour as the foiutions of copper, and they all equally poffeffed the lingular property of fixing the Pruflian colouring matter fo firmly to this red coppery hue, that, befides refitting acids, no number of wafhings with foap, nor expofure to weather for the longeft fpace of time, feem capable in the leaft degree of diminifhing either its body or its luftre, and therefore 1 cannot help thinking that it may prove highly ufeful, and more efpecially for calico-printing, by way of topical application upon cottons, and perhaps in dying cotton-yarn for (tripes of mufiins, bor- ders of handkerchiefs, &c. I have not expe- rienced the fame effect from a dire ft mixture of the Pruflian colouring matter with a folution of copper, not even when I put the prufliate of ammoniac into a foiution of copper by ammo- niac (which I thought mod likely to anfwer) ; but have always found it neceffary either to ap- ply the Pruflian colouring matter (diffolved by pot-afh, foda, ammoniac, or lime) firft to the linen, cotton, or filk, and after fuffering it to dry, to apply fome one of the before mentioned iblutions of copper, filver, or cobalt ; or elfe to apply the metallic folution fir ft, and then the Pruflian ; but in this laft method, I have not found any folution of copper anfwer fo well, ex- celling that by the ammoniac, or volatile al- kali, Many of the other colours (befides the cop- pery red lad mentioned) which were produced on filk and cotton from the Pruflian colour, and the different metallic foiutions, flood feveral wafhings with foap, and particularly the blues, of different lhades and complexions. They all perfectly •■*f,^-f. -.#-*'-;*- PERMANENT COLOURS, &c. 219 perfectly refilled the impreffions of air; and it ieems to me that they are capable of very ufeful applications in this way, and particularly fuited for a kind of printing or painting upon filk, which for this purpofe might be impregnated with a diluted colourlefs prufTiate of pot-alh, foda, or ammoniac, or with a pruffiate of lime, and made to receive a pleafing variety of co- lours from the different metallic folutions, ap- plied either by the pencil or the block; and after d ying, a farther addition of colours might be made, by rincing the filk in clean water, to carry off the Prufiian colour from the parts where it was not wanted, and make room for the application of many different fubftantive colours, which either have been or will be mentioned in the courfe of this work. Similar applications might alfo be made to muflins ; but in that cafe, as fome of the Prufiian colours would be liable to injury from ibap, it would be proper to wafh them with bran or oat- meal in water. I ought farther to mention, that in fome inftances the fame metal diffolved by different acids does not produce the fame colour with the Pruffiate of pot-afh, Sec. Thus, e.g. though the nitrates of filver and cobalt produce the red copper colour before defcribed, the mu- riates of thefe metals produce a blue, and though the nitrate of lead produces a itrong lively blue, the muriate of that metal produces no colour with the pruffiates of lime, ammoniac, &c. To conclude this iubjeft, I fhall only add, that when I fir ft obferved the red copper colour produced as before mentioned, and experienced its fixed unalterable nature^ I ftrongly fufpected that the oxyd wmmm 220 PHILOSOPHY OF oxyd of iron made a part of it, more efpecially as it had firft occurred to me, when applying the ammoniate of copper to the prufliate of pot-afh ; but I always found the fame effect from the pruffiates of ammoniac and lime, in which, by Suitable means, I fatisfied myfelf that no iron was held in folution ; and I moreover found, that no folution of iron would produce any iuch effect with any of the folutions of copper. C HA P. IX. Of Adjcttive Colours from European and Afiath lnfefts. *' La laine & la foie qui montreroient plutot dans Ieur " couleur naturclle la rufticite de I'age que l'efprit " de l'homme & la politefle du fiecle n'auroient " qu'un mediocre commerce fi la teinture ne leur •* donnoit des agrements qui les font rechcrcher & " defircr meme par les nations les plus barbares." Colbert, /«< terate p«ur la Teinture, &c. 1672. Art. I. THE kermes (Coccus Ilicis, Lin.) is an in- fect which the Greeks and Romans diftin- guifhed by i\\t names of Coccus B.ificus, Coc- cus Infe&orius, Coccum Squarlatinum, Gra- num Tinctorrum, &c. and which is found on a fmall fpecies of oak (the Quercus Coccifera of Lin.) trowing in molt of the fouthern parts of Europe, as well as in many parts ofAfia. Recording to Father Plumier, the Arabian name of this infect kermen, or kermes y fignifies a little PERMANENT COLOURS, &c. 221 a little worm ; and Plin\ . ^ough-he confidered it as the excrefcence of a tree, mentions it as fpeedily becoming a worm: " Coccum Ilicis " celerirne in vermiculum fe mutatis *." This infect appears to have been one of the molt ancient of all dying drugs, and that which produced the colour originally known by the name of fcarler. in Enghnd, as it had been by that of coccus among the Romans. Pliny in- deed inaccurately defcribes it as a kind of rofe colour, (coccus, qui in rofis micat,) whereas it is in fact a red, approaching nearly to that of florid arterial blood. Ctefias and iElian alfo mention a crimfon colour produced from in- fects, which probably were either the kermes or lacca infects. Sir John Chardin, in an account of Perfia, (publifhed in Harris's Voyages,) re- marks, that in certain parts of Media " they - ff verging hairs longer than the antennas." The tail is " a little white point, fending off C( two horizontal hairs, as long as the body." The infect had three pair of limbs half of its own length, but no wings were feen by Mr. Kerr. As foon as they are brought forth, the infects begin to g PERMANENT COLOURS, &c. 233 colouring matter of dried lac ; but it probably did not fucceed according to their expectations, fince it does not I believe now fubfift. An ex- tract, anfwering tolerably well, may be made from this drug, by merely boiling it in water, {training off the coloured liquor, and evaporat- ing it to a folid confidence. The cells which contain the lacca infects, and the matter of which they are compofed, as well as the ufes to which they are fubfei vient, feem analogous in many refpects to the honey-comb, &c. of bees. The fine red-coloured liquor contained in the cells of the lac is alfo defcribed by fomc authors as being fvveet to the tafte, at the fame time that it readily mixes with water. Great ufe is made of it as a dye by the natives of Affam. The colours dyed by (tick lac approach very nearly to thofe of cochineal. They are indeed not quite fo lively and beautiful, but this defect is in fome degree compeniated by their being more durable, efpecially on cottons, where I have employed it with fome fuccefs topically, with different bafes. It has been fometimes a practice to employ a mixture of the colouring matter of lac, with that of cochineal, in pro- ducing fcarlets, &c. Both require the fame bafis, and nearly the fame treatment, which will be fully defcribed in the chapter reflecting the ufes of cochineal. At prefent, however, almoft all the lacca brought to Europe is afterwards fent to Portugal, Barbary, &c. and employed in ilaining goat fkins to produce what is called red Morocco leather. Art. m 234 PHILOSOPHY OF Art. III. The Coccus tinctorius Polonicus is a fmall round infect very much refembling the kermes in many refpects. It ufed to be collected, in confiderable quantities, in the Ukraine and other provinces of Poland, as well as in the Great Dutchy of Lithuania, from about the roots of the German knot-grafs or knawel (Scleranthus perennis, Lin.). The male only, by a transformation fimilar to that of the male kermes, becomes a fly, though with but two wings, which are white, edged with red. The females, being impregnated by the male, enlarge their fize, and become ready to bring forth their young foon after the fummer folftice, at which time they abound mod in a crimfon juice, which was formerly very much ufed by the Turks and Armenians in dying wool, filk, and hair, as well as in ftaining the nails of women's fingers. But the ufe of thefe infects, like that of kermes, has been nearly laid afide every where, fince the cheaper and more beautiful colours of cochineal have become generally known. This dye was fixed on wool and filk by the ufual mordant or preparation of alum and tartar. Very fimilar to the Coccus Polonicus is an infecl, which in many parts of Europe was for- merly taken from the roots of the burnet, (Po- terium Sanguiforba, Lin.) and which was ufed in different countries, and particularly by the Moors, for dying wool and filk of a crimfon or rofe colour. Ray, defcribing this plant, fays, '* Hujus radicis adnafcitur quibufdam in locis r - Garden,) I catched a male cochineal fly, and examined it in your aquatic microfcope. It is feldom a male is met with. I imagine there may be one hundred and fifty or two hundred females for one male. The male is a very active creature, and well made, but (lender in com- parifon of the females, who are much larger and more fhapelefs, and feemingly lazy, tor- pid, and inactive. They appear generally fp overgrown, that their eyes and mouth are quite funk in their rugas or wrinkles; nay their antenns and legs are almoft covered by them, and are fo impeded in their motions from thefe fwellings about the infertions of their legs, that they can fcarce move them, much lefs move themfelves. " The male's head is very diftinct from the IC neck: the neck is much fmaller than the head, " and much more fo than the body. The thorax '? is elliptical, and fomething larger than the; li head and neck together, and flattifh under^ ". neath ; from the front there arife two anten-- " na?, (much longer than thofe of the females,) " which the infect moves every way very brifk- " lv. m PERMANENT COLOURS, &c. 243 * s ly. Thefe antennae arc all jointed, and from tf every joint there come out four fhort fetse, *• placed two on each fide. " It has three jointed legs on each fide, and u moves very brifkly and with great fpeed. c< From the extremity of the tail there arife twd K< long fetse or hairs four or five times the length u of the infect. They diverge as they lengthen, Ki are very (lender, and of a pure (how white" c< colour. It has two wings, which take their M rife from the back part of their moulders or lt thorax, and lie down horizontally, like the 2 PHILOSOPHY OF After the death of Mr. Thiery de Menon- ville, the ftock of fine or domefticated cochi- neal, which iie had multiplied in the garden at Port au Prince, was fuffered to perifh by ne- glect ; but the hardier wild fort, having found means to fubfift, though neglected, was after- wards taken under the care of Mr. Bruley, (fub- ftitute of the attorney-general of that province,) who, from the remains of Mr. de Menonville's eftablifhment, formed a plantation for propa- gating and multiplying thefe infects, of which he fent a confiderable quantity, in the year 1787, to the minifter of the French marine at Paris, at whofe requeft the Royal Academy of Sci- ences -commifiloned Mr. Berthollet, and three others of its members, to caufe proper experi- ments to be made therewith, which they accord- ingly did, under their own inflection, at the celebrated eftablifhment (for fcarlet dying) of the Gobelines near Paris j and from thefe expe- riments it appeared, that the grana fylveftra of St. Domingo afforded colours by dying exactly fimilar to thofe of the Spanifh fine cochineal, allowing only after the rate of twelve ounces of the former for five of the latter. Mr. Bruley fome time after lent to France a fecond parcel of the fame cochineal, produced from his plan- tation in the year 1788 j and this being tried by the fame commiffarics of the Royal Academy, though in different ways, produced nearly the fame effects* Very confiderable differences of external co- Jour or appearance occur in different parcels of the fine cochineal ; probably becaufe the white farina- PERMANENT COLOURS, &e. ig$ fariiiaceous powder, with which thefe infects are naturally covered, is more or lefs warned off by the hot water in which they are killed by im- merfion, as well as by other circumftances which occur in the drying and packing. When this powder has been intirely removed, the infects appear of a chocolate colour, inclining a little to the purple, and are then called renigrida. Generally, however, fo much of the white pow- der remains, efpecially in the little furrows which crofs the infect's back, as occafions a grayifh appearance, called jafpeada ; and fometimes in- deed this powder lo perfectly covers the cochi- neal, as to render them all over white. This I remember to have been particularly the cafe of a parcel which a friend of mine had purchafed, and which was refufed by feveral dyers to whom it had been fent, from a perfuafion of its hav- ing been fraudulently covered by white lead, or ibme other metallic calx intermixed with it, to increafe the weight ; and one very eminent dyer alleged, that he had formerly feen and tried a Gmilar parcel, and that the white powder had been found to confift principally of a preparation of mercury. That I might be enabled to as- certain whether an opinion fo unlikely had any foundation, my friend caufed feveral ounces of this powder to be feparated from the infects by fifting; and having tried it Sufficiently, I found it to be intirely of an animal nature, and appa- rently nothing but the farina which naturally covers thefe infects. It even yielded a confider- able portion of the true cochineal colour, and dyed good fcarlets in the ufual way, though it probably was affifced by fome of the limbs or ether parts of the bodies of the infects, fepa- rated 2^4 PHILOSOPHY OF rated by rubbing in the lieve : though I am per- fuaded that a part of the colour in queftion na- turally exifted in the farina or white powder ic- felf; and if this be the cafe, it would be highly advantageous to contrive means for killing the cochineal, without wafhing off any part of the powder in queftion, which might, I think, be done by putting them into tinned vefTels, made (o as to fhut clofely, which might be plunged into boiling water, and withdrawn at a proper time, without letting a (ingle drop of it come into contact with the infects, or carrying off any of the powder in queftion* And perhaps this method might be ufed with advantage, even if it fhould be found that no colouring matter re- fides in the white powder, finCe it is difficult rcf conceive that the cochineal can be plunged into boiling water, fo as to wafh away the powder in- tirely, (as is frequently done,) without a lofs of fome part of the colouring matter contained in the bodies of the infects themfelves. The true original grana fylveftra feem to have been very different from what is at prefent fold under that denomination in this kingdom, and which has the appearance of a dry powder, with many fmall lumps or fragments of fomething which had been previously formed into a cake cr a dried uniform mafs. It affords indeed nearly the fame fpecies of colour as cochineal, but in a much fmaller proportion j fix pounds being neceffary, according to my experiments, to dye as much cloth as one pound of the fine cochineal; whereas the true grana fyl- veftra are reprefented as yielding at leaft half as much as the fine, and they fell for at leaft half the price Ml ■■■■ i-'* 2 3^ PERMANENT COLOURS, &c. price in fome parts of Europe j whilft here the fub- ftancefo called, and which has not the lead appear- ance of any infect, fells at prefent for lefs than an eighth of the price of fine cochineal. Pro- bably it is compofed of the white downy fub- ftance which the wild infects are reprefented as leaving in great abundance on the nopals, and of other excrementitious matters depofited by them, joined to fragments, broken limbs, duft, &c. of the infects themfelves, and perhaps with an addition of fome vegetable matters, all beat up into one uniform mafs. Something of this fort was formerly practifed even with the true cochineal, according to Dr. Brown, who fays, " the cochineal infects ufed to be prepared by < c pounding them, and fteeping the pulp in the " decoction of the texuatla, (a fpecies of me- fome of the true nopal plants, two of which were fent out by the Bridgwater, during that feafon, to Madras, and put under the care of Dr. Anderfon, where they have fince been mul- tiplied to feveral thoufands, and been trans- planted from thence to Bengal and St. Helena, in order that a fufficient ftock might be in rea- dinefs to receive any cochineal infects which fhould ■ ■ ^^^B h PERMANENT COLOURS, &c. 261 fhould arrive ; a committee of the Directors having previoufly reported as and retain them permanently when thus mixed. I think, how- ever, that in this way the cloth does not exhauft the colour of the dying liquor quite fo perfectly as in the other ; which feems alio to be the cafe, where, inftead of emptying out the boiling li- quor after the firft preparation, the remainder of the folution of tin and the cochineal are added to it, and the cloth is dyed therein ; and as far as I can judge, there is no other reafon for in- curring fo much expence of fuel, labour, and time, than this, which indeed is not a fufficient reafon, where there are other eloths to be dyed of fimilar colours immediately afterwards ; be- caufe what may have been left by the firft, will naturally be gained by thofe which are afterwards dyed in the lame veflel. I have moreover often dyed very beautiful fear- lets, by preparing or boiling the cloth with the whole quantity of folution of tin and tartar at once, (as is commonly done with alum and tartar,) and afterwards dying it unrinced with the ; whole of the cochineal in clean water only ; and in this way I have found the colouring particles fo completely taken up by the cloth, that the li- quor became as clear as the pureft water, and the colour was generally very perfect. Some dyers, befides the tartar ufed in the firft boiling, employ as much of it as of cochineal in the fecond or dying part of the procefs ; and certainly f 270 PHILOSOPHY OF certainly the doing fo will be advantageous, whenever the colour is wanted to approach nearer than ordinary to the aurora completion, though this is not the effect which would be generally ex- pected to refult from thence. Pcerner ufes no co- chineal in the firft boiling, nor indeed is any necef- fary, though a little may probably help to decom- pose the oxide of tin, and fix it more copioufly in the fibres of the cloth. For fcarlet, many dyers prefer the red argol or crudered tartar ; but the matter to which it owes this colour is wholly in- capable of adding any colour to that which the wool may otherways acquire, and therefore at bed it will only prove ufelefs. Wool is feldom dyed fcarlet until it has been fpun, wove, and fulled*S becaufe the yellowifh tendency which the co- chineal colour acquires from tartar in the dying procefs, is nearly all taken away in the full- ing, and a rofe produced inftead of* a fcarlet colour. Mr. Berthollet thinks the folution of tin, be- fore defcribed, does not affect the cochineal co- lours, merely by the proportion of that metal, which it contains; and that when either fal am- moniac, falt-petre, or common fait, enter the compofition of an aqua regia, the compound will be lefs acid than when it confifts of the ni- tric and muriatic acids folely j and that the former deferves therefore to be preferred, as having a lefs violent action upon the fibres of woollen cloths, and upon colouring matters. It is remarkable, that during the prefent cen- tury, no confiderable improvement has been made in the procefs or means of dying fcarlet j a cir- 271 PERMANENT COLOURS, &c. 2. circumftance which is the more extraordinary, fince the pre-eminent luftre, as well as the coftly nature of this dye, have rendered it an object of particular attention, not only to dyers, but to eminent chymifts, by whofe refearches we might have expected, that at lead every obvious im- provement therein would have been long fince attained. That this, however, has not been done, will, I think, manifeftly appear, by the following ftatement of my own particular ob- fervations and experiments on this fubject, which began in the year 1786. Having been led to pour boiling water repeatedly upon powdered cochineal in a china bafon, and to decant it as often from the fubfiding infoluble parts, until they would yield no more colour, I found that by adding a little pot-afh to this feemingly ex- haufted fediment, and pouring frefh boiling wa- ter thereon, a farther copious extraction of co- lour inftantly difplayed itfelf, equal, as far as I could judge, to about one- eighth of the whole of that which had been originally contained in the powdered infects; and having by repeated trials conftantly found this effect, I too haftily concluded that the colour thus obtained by the help of pot-afh was fo far of a refinous nature, or fo intermixed with a refinous matter, as to have always been incapable of being extracted by the means ufually employed for dying with cochineal ; and that if it mould be found capa- ble of yielding colours as beautiful and perma- nent as thofe dyed with the more foluble co- louring particles of thefe infects, an acquifition might be made of fo much new colouring mat- ter, which till then had, as I conceived, been 5 alwavs 272 PHILOSOPHY OF always thrown away. That it was capable of yielding fuch colours, I foon afcertained, by re- peatedly extracting this particular colouring matter by the help of pot-afh, and afterwards dying fmall pieces of cloth fcarlet with it, (in the ways ufually employed tor dying that co- lour,) and by comparing and expofing them to the weather with other pieces dyed from the more foluble colouring matter of cochineal. Continuing my inquiries on this fubjecl:, I loon perceived that the colour, denominated fcarlet, muft in facl be a compound colour, (like green, purple, and orange,) confiding probably of about three-fourths of a moft lively pure crimfon or rofe colour, and about one- fourth of a pure bright yellow ; and that there- fore when the natural crimfon of the cochineal is made fcarlet by the means always hitherto employed for dying that colour, there muft be a change produced equivalent to a converfion of one- fourth of the cochineal colouring mat- ter from its natural crimfon to the yellow co- lour ; and as a better yellow might be obtained from other drugs, where it naturally exifts, and for a fiftieth part of what it cofts when obtained in this way, from the moji coftly of all dying drugs, (cochineal,) it neceflarily followed, that this the univerfal and only known method of producing a fcarlet, muft be highly injudicious, becaufe unnecefTarily expenfive. Convinced of this important truth, and at the fame time believing too eafily, on the authority of Hellot, Macquer, and others, that the na- tural PERMANENT COLOURS, &c. 273 tural crimfon of cochineal was rendered fcarlet only by the nitric acid employed to diffolve the tin ufed in dying that colour, I began a feries of experiments for producing it, without any fuch iv aft e of the cochineal colouring matter. For this purpofe it feemed neceflfary to difcover a mordant or bafis, capable of permanently fix- ing and ftrongly reflecting the pure vivid co- chineal crimfon, without giving it any tendency towards the yellowifli hue. I concluded, and found by experiments, that the neceffary purity and vivacity of colour could not be obtained from an aluminous bafis, however diflblvedj though it doubtlefs fixes the colouring particles of cochineal more durably than any other mor- dant j and the like defect was found to accom- pany the folutions of all the other earths, as well as of the metals and femi-metals, tin alone excepted ; and with this farther difadvantage, that moft of them either degraded or altered the natural colour of cochineal very considerably. It followed therefore that a bafis to fuit my pur- pofe muft be fought for in the pure white calx of tin, fo diflblved or combined as to reflect the cochineal crimfon unchanged, and with the greateft poflible luftre. Milled by what thofe eminent writers Dufay, Hellot, Macquer, Schef- fer, le Pileur d'Apligny, &c. had advanced, as well as by the opinions of others, with whom I had converfed on this fubject, I erroneoufly con- cluded, that all folutions of tin, in which the nitric acid predominated, would neceflarily in- cline the cochineal crimfon towards the yellowifli hue, and that therefore fuch folutions ought to be excluded from my experiments. In this T perfuafion, w 274 PHILOSOPHY OF perfuafion, I difiblved parcels of that metal in almoft every other acid, and tried them fepa- rately for dying with cochineal. Their feveral effects will hereafter be more particularly ftated : at prefent I need only mention, that of all others the muriatic folution feemed the belt fuited to anfwer my purpofe, as it both fixed and reflected the pure crimfon or rofe colour of the cochi- neal unchanged, and with the utmoft bright- nefs. To produce a fcarlct, therefore, it was only necelTary to fuperadd, and intimately com- bine with this crimfon or rofe colour, a fuitable portion of a lively golden yellow, capable of being properly fixed and reflected by the fame bafis. Such a yellow I had previoufly difco- vered in the Quercitron bark, (which will be the fubject of my next chapter,) and alfo in what is here called young fuftic, (Rhus Cotinus, Lin.) though its colour was much lefs bright, and much lefs durable, than that of the Quercitron bark ; for famples of each, dyed by the fame- means, having been alike expofed to the wea- ther at the fame time, the fuftic colour was nearly deftroyed, before that of the bark had fen- fibly faded. This laft had alfo the advantage of being not only the brighteft, but the cheapen: of all yellows, fince one pound of the bark in powder, which coft but three- pence farthing, dyed, with a iufficient quantity of muriate of tin, between thirty and forty pounds weight of woollen cloth of a full bright golden yellow; and this being afterwards dyed in the fame li- quor, with one-fourth lefs of cochineal than what is ufually employed, acquired a fcarlet equal in beauty and durability to any which is 7 ufually PERMANENT COLOURS, &c. 275 ufually given by the ordinary means, with a full proportion of cochineal; and fuch were the general refults of a great number of expe- riments. The quantity of muriatic folution of tin ne- cefifary to dye a given quantity of fcarlet in this way, feemed to me at that time to depend on the proportion of metal contained in it, and this laft to depend on the ftrength of the acid ufed for that purpofe. That which I employed, and which I bought at the price of 38 s. per 11 2lb. or about four-pence per pound, dif- folved in a ftrong fand heat, one-third of its weight of granulated tin j and this folution would, with the proportions of cochineal and bark before mentioned, dye about ten times its weight of cloth, of a good fcarlet colour. I have faid that three pounds of muriatic acid, which coft but one milling, might be made to diflblve a pound of tin, which would require eight pounds of fingle aqua-fortis to diflblve it; and this quantity of aqua-fortis, at the rate of 8d. per lb. would coft 5 s. 4d., fo that on each pound of tin diflblved by muriatic acid, inftead of the nitric, I calculated a faving of 4s. 4d. The muriatic acid, therefore, which M. Beaume had ftiled the true diflblvent of tin, ( cc Le vrai ■ at leaft none has appeared in fome which I have kept for more than three years. It will produce full twice as much effect as the dyers' fpirit, or ni- tro*muriaticfolution of tin, with lefs than a third of the expence. It has moreover the property of raifing the colours of, I believe, all adjective dyes, more than the dyers' fpirit, and full as much as the tartrite of tin, without changing; the natural crimfon of cochineal towards the yellow- i(h hue j and therefore, after having made a great number of experiments with it, I think myfelf warranted in ftrongly recommending this murio- fulphate of tin for dying the compound fcarlet colour already defcribed, (with the cochineal crimfon and Quercitron yellow,) for which it will be found highly effectual and cecono- mical. For this fpecies of fcarlet nothing is neceffary but to put the cloth, fuppofe 100 lb. weight, into a proper tin veflel, nearly filled with water, in which about eight pounds of the murio-ful- phuric folution of tin have been previoufiy mix- ed, to make the liquor boil, turning the cloth as ufual through it, by the winch, for a quarter of an hour ; then turning the cloth out of the liqugr, to put into it about four pounds of co- chineal, and two pounds and a half of Quer- citron bark in powder, and having mixed them well, to return the cloth again into the liquor, U 2 making 1X)Z PHILOSOPHY OF making it boil, and continue the operation is ufual until the colour be duly raifed, and tie dying liquor exhaufted, which will be the cab in about fifteen or twenty minutes j after which the cloth may be taken out and rinced as ufual. In this way the time, labour, and fuel, necefifary for filling and heating the dying veflel a fecor.d time, will be faved ; the operation finifhed much more fpeediiy than in the common way ; ar.d there will be a faving of all the tartar, as well is of two-thirds of the coftof fpirit, or nitro-rm- riatic folution of tin, which for dying ioob. of wool, commonly amounts to ios. ; whereas, S lb. of the murio-fulphuric folution will only coft about 3 s. There will be moreover a fav- ing of at leaft one- fourth of the cochineal ufually employed, (which is generally computed at the rate of one ounce for every pound of cloth,) and the colour produced will certainly not prove in- ferior in any refpect to that dyed with much more expence and trouble in the ordinary way. When a rofe- colour is wanted, it may be readily and cheaply dyed in this way, only omitting the Quercitron bark, inftead of the complex me- thod now practifed of firft producing a fcarlet, and then changing it to a rofe by the volatile alkali contained in dale urine, fet free or de- compofed by pot-afh or by lime : and even if any one fhould ftill unwijely choofe to continue the practice of dying fcarlet without Quercitron bark, he need only employ the ufual propor- tions of tartar and cochineal, with a fuitabje quantity of the murio-fulphate of tin, which, whiht it cofts fo much lefs, will be more effec- tual than the dyers' fpirit. Several PERMANENT COLOURS, See. 293 Several hundreds of experiments warrant my affertion, that at leaft a fourth part of the co- chineal generally employed in dying fcarlet, may be faved by obtaining fo much yellow as is necef- fary to compofe this colour from the Querci- tron bark ; and indeed nothing can be more felf- evident, than that fuch an effect, ceteris paribus, ought neceflarily to refult from this combina- tion of different colouring matters, fuited to produce the compound colour in queftion. Let it be recollected that the cochineal crimfon, though capable of being changed by tartar to- wards the yellow hue on one hand, is alfo ca- pable by other means of being changed towards a blue on the other, and of thereby producing a purple without indigo or any other blue colour- ing matter: yet I am confident that nobody would believe a pound of cochineal fo employed capable alone of dying as much cloth, of any particular fhade of purple, as might be dyed with it, if the whole of its colouring matter were employed folely in furnifhing the crimfon part of the purple, whilft the other (blue) part thereof was obtained from indigo. To fay that a pound of cochineal alone could produce as much effecl: or colour as a pound of cochineal and a pound of indigo together-, would be an improbability much too obvious and palpable for human belief; and there certainly would be a fnnilar improbability in alleging, that a pound of cochineal, employed in giving another com- pound colour (fcarlet), could alone produce as much effecl: as a pound of cochineal and a pound of Quercitron bark, when the colour of this laft was employed only in furnifhing one of the component parts of the fcarlet, for which a con- U 3 fiderable 294 PHILOSOPHY OF fiderable portion of the* colouring matter of th? cochineal mud otherwife have been expendec, which certainly happens in the new mode of dy- ing fcarlet, becaufe the colour produced win an addition of the Quercitron yellow inclines n<3 more towards a yellow, than the fcarlet pro- duced by yellowing a part of the cochineal u- lour in the ufual method with tartar. I retain, therefore, at this moment, as much confidence as I ever had in the reality and importance of my propofed improvements in this refpect*. The fcarlet compofed of cochineal crimfon and Quercitron yellow, is moreover attended with this advantage, that it may be dyed upon wool and woollen-yarn without any danger of its being changed to a rofe or crimfon, by the procefs of fulling, as always happens to fcarlet dyed by the ufual means. This laft being in fact nothing but a crimfon or rofe colour, yel- lowed by fome particular action or effect of the tartar, is liable to be made crimfon again by the application of many chymical agents, (which readily overcome the changeable yellow pro- duced by the tartar,) and particularly by calca- * Of the benefit which I formerly expe£led to obtain by employing pot-afh to extract a part of the cochint-al co- lour, which water alone did not apnear capable of cxtmft-r ing, it mull be remarked that I have fometime fince con- vinced m)fc-!f of its being an iilufion ; for, by repeated tri- als, 1 have found that the iblid parts of powdered cochineal remaining afte; it has been boiled with the folution of tin, as in the common dying procefs, yield no colour worth notice, upon the application of pot-afh, the folution of tin enabling the water to extract the colour fufficiently ; fo that in truth there is no fuch waile of cochineal colour as I had loppofed in the ufual way of employing that drug. reous PERMANENT COLOURS, &c. 295 reous earths, foap, alkaline faks, &c. But where the cochineal colouring matter is applied and fixed merely as a crimfon or rofe colour, and is rendered fcarlet by fuperadding a very perma- nent Quercitron yellow, capable of refilling the ftrongeft acids and alkalies, (which it does when dyed with folutions of tin,) no fuch change can take place, becaufe the cochineal colour having never ceafed to be crimfon, cannot be rendered more fo, and therefore cannot fufFer by thofe impreffions or applications which frequently change or fpot fcarlets dyed according to the prefent practice. There is alfo a lingular property attending the compound fcarlet dyed with cochineal and Quer- citron bark -, which is, that if it be compared with another piece of fcarlet dyed in the ufual way, and both appear by day- light exaclly of the fame Jhade> the former, if they be afterwards compared by candle-light, will appear to be at lead feveral fhades higher and fuller than the latter; a circumftance of fome importance, when it is confidered how much this and other gay colours are generally worn and exhibited by candle-light during a confiderable part of the year. To illuftrate more clearly the effects of the murio-fulphuric folution of tin with cochineal in dying, I mall ftate a very few of my numerous experiments therewith ; obferving, however, that they were all feveral times repeated, and always with fimilar effects. u 4 tft. 296 PHILOSOPHY OF 1 ft, I boiled one hundred parts of woollen cloth in water, with eight parts of the murio- fulphuric folution of tin, during the fpace of ten or fifteen minutes ; I then added to tlhe fame water four parts of cochineal, and two parts and a half of Quercitron bark in powder, and boiled the cloth fifteen or twenty minutes longer ; at the end of which it had nearly imbibed all the co- lour of the dying liquor, and received a very good, even, and bright fcarlet. Similar cloth dyed of that colour at the fame time in the ufual way, and with a fourth part more of cochineal, was found upon comparifon to have fomewhat lefs body than the former; the effect of the Quer- citron bark in the firft cafe having been more than equal to the additional portion of cochineal employed in the latter, and made yellow by the action of tartar. 2d, To fee whether the tartrite of tin would, befides yellowing the cochineal crimfon, contri- bute to raife and exalt its colour more than the murio-fulphate of that metal, I boiled one hun- dred parts of cloth with eight parts of the mu- rio fulphuric folution, and fix parts of tartar, for the fpace of one hour ; I then dyed the cloth, unrincedy in clean water, with four parts of co- chineal, and two parts and a half of Quercitron bark, which produced a bright aurora colour, becaufe a double portion of yellow had been here produced, firft by the Quercitron bark, and then by the action of tartar upon the cochineal colouring matter. To bring back this aurora to the fcarlet colour, by taking away or chang- ing the yellow produced by the tartar, I divided PERMANENT COLOURS, &c. 297 the cloth whilft unrinced into three equal p?.rts, and boiled one of them a few minutes in water (lightly impregnated with pot-afh ; another in water with a little ammoniac ; and the third in water containing a very little powdered chalk, by which all the pieces became fcarlet ; but the two laft appeared fomevvhat brighter than the firft, the ammoniac and chalk having each rofed the cochineal colour rather more advantageoufly than the pot-afh. The beft of thefe, however, by comparifon, did not feem preferable to the com- pound fcarlet dyed without tartar, as in the pre- ceding experiment j conlequently this did not feem to exalt the cochineal colour more than the murio-fulphate of tin ; had it done fo, the ufe of it in this way would have been eafy without relinquishing the advantages of the Quercitron yellow, 3d, I boiled one hundred parts of woollen cloth with eight parts of the murio-fulphuric folution of tin, for about ten minutes, when I added four parts of cochineal in powder, which by ten or fifteen minutes more or boiling, pro- duced a fine crimfon. This I divided into two equal parts, one of which I yellowed or made fcarlet by boiling it for fifteen minutes with a tenth of its weight of tartar in clean water j and the other, by boiling it with a fortieth of its weight of Quercitron bark, and the fame weight of murio-fulphuric folution of tin ■, fo that in this laft cafe there was an addition of yellow co- louring matter from the bark, whilft in the former no fuch addition took place, the yellow neceftary for producing the fcarlet having been wholly gained hy a change and diminution of 1 o the 29 S PHILOSOPHY OF the cochineal crimfon ; and the two pieces be- ing compared with each other, that which had been rendered fcarlet by an addition of Quer- citron yellow, was, as might have been expect- ed, feveral fhades fuller than the other. 4th, I dyed one hundred parts of woollen cloth fcarlet, by boiling it firft in water with eight parts of murio-fulphate of tin, and twelve parts of tartar, for ten minutes, and then add- ing five parts of cochineal, and continuing the boiling for fifteen minutes. This fcarlet cloth I divided equally, and made one part crimfon, by boiling it with a little ammoniac in clean wa- ter ; after which I again rendered it fcarlet, by boiling it in clean water, with a fortieth of its weight of Quercitron bark, and the fame weight of murio-fulphate of tin ; and this laft, being compared with the other half, to which no Quer- citron yellow had been applied, was found to poflefs much more colour, as might have been expected. A piece of the cloth, which had been dyed fcarlet by cochineal and Quercitron bark, as in the firft experiment, being at the fame time boiled in the fame water with ammoniac, did not become crimfon, like that dyed fcarlet, with- out the bark. In this way of compounding a fcarlet from cochineal and Quercitron bark, the dyer will at all times be able, with the utmoft certainty, to produce every poffible fhade between the crim- fon and yellow colours, by only increafing or diminishing the proportion of bark. It has in- deed been ufual at times when fcarlets, approach- ing nearly to the aurora colour, were in fafliion, to PERMANENT COLOURS, &c. 299 to fuperadd a fugitive yellow either from turmeric, or from what is called young fuftic (Rhus Coti- nus) ; but this was only when the cochineal colour had been previously yellowed as much as foffible by the life of tartar, as in the common way of dying fcarlet ; and therefore tb.3t prac- tice ought not to be confounded with my im- provement, which has for its object to preclude thelofs of any part of the cochineal crimfon, by its converfion towards a yellow colour, which may be fo much more cheaply obtained than the Quercitron bark. By fufficient trials, I have fatisfied myfelf that the cochineal colours, dyed with the murio-ful- phuric folution of tin, are in every refpect at Jeafl as durable as any which can be dyed with any other preparation of that metal 5 and they even feem to withftand the action of boiling foap fuds fomewhat longer, and therefore I cannot avoid earneftly recommending its ufe for dying rofe and other cochineal colours, as well as for compounding a fcarlet with the Quercitron/ bark. I have thus freely given the refults of a mul- titude of experiments, which have coft me fome money, with not a little time and meditation; and I have given them without the leaft idea of ever claiming any kind of remuneration from the public - s and though it may be fome time before the truth and importance of what I here offer are fully recognized, I am confident this will happen fooner or later ; and by putting it into every one's power to bring my ideas to the tcft * 3 oo PHILOSOPHY OF teft of experience, I mall have at lead done my duty. It remains, however, yet for me to commu- nicate the effects of a confiderable number of earthy and metallic bafes upon the colouring matter of cochineal, which I fhall ftate as briefly as pofiible, omitting all detail reflecting propor- tions and modes of conducting the dying ope- rations, which are to be underftood as having been conformable to the common practice where nothing is mentioned to the contrary. Woollen cloth, dyed with cochineal and ni- trate of tin, produced a fine crimfon, and this, boiled in the fame liquor with tartar, was changed to a good fcarlet. A fimilar, but rather better effect was produced by tin diflblved immedi- ately in a mixture of aqua-fortis and tartar. The fcarlet given by this tartaro- nitrate of tin ap- peared highly beautiful. Tin put into aqua-fortis, with a confiderable portion of refined fugar, afforded a very thick adhefive folution, which afiumed a blackifh brown colour, like that of burnt fugar, and be- ing tried as a mordant in dying, it was found in- capable of fixing the cochineal or any other co- lours. The tin in this ftate did not feem fitted to combine with the fibres of the cloth, and the fugar had manifeftly fuffercd a kind of com- buftion. Spirit of wine, put with tin into aqua- fortis, alfo rendered the folution unfit to combine with wool, or fcrve as a mordant. Tin, PERMANENT COLOURS, &c. 301 Tin, calcined with an equal quantity of falt- petre in a red-hot crucible, being thrown into water, afforded a milky folution, tafting very fenfibly of the alkaline part of the falt-petre, and evidently fufpending a confiderable portion of the metallic calx. Cloth boiled in water with fome of this folution, thenrinced, and dyed with cochineal, took a crimfon, inclining to the purple ; and this, boiled in the fame liquor with tartar, was changed to fcarlet. I poured two pounds of aqua-fortis, with an equal weight of water, upon a large quantity of granulated tin, and leaving them together dur- ing the three fummer months of 1790, I after- wards found near a pound of the calx of tin col- lected in lumps at the bottom of the glafs velTel. This being feparated. and dried, fome of it was finely powdered and thoroughly wajhed; then putting it with an equal weight of cochineal into water, I boiled cloth therein, which took a full equal crimfon, fomewhat deficient in brightneis. Tartar being added to the liquor, and the cloth farther boiled therein, it became of a good fcar- let. Lemon juice, ufed inftead of tartar, pro- duced the like effect. By fubftituting cauftic volatile alkali for tartar and lemon juice, a crim- fon, greatly inclining to purple, was produced. The oxide of tin, therefore, does not act in all cafes merely as Juch> but its effects often depend on triple, quadruple, and fometimes even more complex combinations, in which different faline and other parts of the compound remain perma- nently united, at leaft where the fhades of co- lour depending on them are found permanent. ,Jt is thus that fea-falt, and other purely faline matters, T 302 fHILOSOPHY OF matters, which having no earthy or metallic bafts, cannot become the balls of any adjec- tive colour, produce lafiing effects in modi- fying and varying the complexions of different colours. It muft, however, be obferved, that though the calx of tin, after being thoroughly warned and dried, was capable of dying a crimlon en woollens with cochineal, and a fcarlec, where either tartar, lemon juice, or Quercitron bark were added, it would not permanently combine with or become the bafis of thefe colours upon cotton; and indeed on woollen it was only the finer particles of the calx which really combined with the colouring matter and the wool, the groffer being always diftinclly found at the bot- tom of the dying vefiel ; and when I attempted to impregnate woollen cloth with the oxide of tin feparately, by boiling them together, I al- ways found, on rincing the cloth, and endea- vouring to dye it with cochineal in a different veffel, that the oxide had not penetrated or united with the wool, fo as to afford a bafis for raifing and fixing the colour, it being neceffary for this purpofe that both the oxide and the colouring matter fhould be mixed together in the dying vefiel, and exert their mutual attractions for and upon each other, before rhey could be properly- taken up by the cloth •, and this was done better after they had been previoufly mixed and left to- gether for feveral hours. One ounce of the calx of tin before men- tioned, unwarned, being diflblved in three ounces of muriatic acid, and woollen cloth being dyed 9 with PERMANENT COLOURS, &c. joj with a tenth of its weight of this folution, and a twentieth of cochineal, it took but a very lan- guid pale red colour. The calx of tin, which was immediately decompofed upon its intermix- ture with, water, manifested very little difpofition to penetrate or combine with the fibres of the wool ; and after long boiling the greater part of it, and of the colouring matter, remained fuf- pended in the dying liquor. Nearly fimilar ef- fects refulted from a folution of tin by the oxy- genated muriatic acid. Cochineal with a folution of tin by muriatic acid, dyed a beautiful crimfon j and with a fo- lution of that metal, by a mixture of tartar and muriatic acid, a beautiful fcarlet. Cochineal with tin diflblved by muriatic acid and the acid of tar mixed, produced a dark crimfon ; and with tin, and a little manganefe diflblved in muriatic acid, it produced a very bluifli crimfon. Cochineal with tin diflblved by muriatic acid and borax mixed, dyed a very good crimfon. Cochineal with tin calcined by the long con- tinued action of fulphuric acid, dyed a falmon colour j and with a recent folution of tin it pro- duced a reddifh falmon colour, inclining a little to the crimfon. A like colour was produced witli tin diflblved by equal parts of fulphuric and ni- tric acids mixed. Oil of vitriol having been poured upon tartar and granulated tin, the mixture immediately be- came ■SEE 3°4 PHILOSOPHY OF came black, by the aftion of the fulphuric acid upon the carbonic bafis, which, with hydrogenc and oxygene, are the conftituents of tartar. Cloth dyed with a tartaro- fulphuric folution of tin thus made, and cochineal, took an aurora colour. Tin diffolved by the pure acid of tartar, fepa- rated from its alkaline bafis, (by the means ufually employed for that purpoie,) dyed with cochineal on cloth a very beautiful fcarlet, in- clining a little to the aurora. A fimilar colour was produced by water faturated with cream of tartar, in which granulated tin had been kept fix weeks. Tin very readily diiTolves by pure citric acid, and even by lemon juice ; and the folution newly made, dyes with cochineal a moll beautiful fcar- let, inclining, like the preceding, a little to the aurora. Indeed, I have repeatedly found that the citric acid with tin, a£ls at leaft as efficaci- oufly as that of tartar in yellowing the cochi- neal crimfon. Nothing can exceed the beauty of fcarlet dyed with the citrate of tin. Granulated tin, diffolved by ftrong vinegar, acquired a very particular, and fomewhat of an vmpleafant fmell j and with cochineal it dyed cloth of a fcarlet, inclining a little to the crim- fon colour. Tin diffolved by acid of tar produced with cochineal a colour between the fcarlet and crim- fon fhades. Phof- PERMANENT COLOURS, &c. 305 Phofphoric acid produced a permanently tranfparent and colourlefs folution of tin ; and this (phofphate of tin) with cochineal dyed an aurora colour. Tin diflblved by fluoric acid, produced with cochineal a very good fcarlet. Such were the effects produced on woollen cloths by different preparations of tin, as bafes for dying with cochineal. With other bafes, cochineal gave the following colours to wool, viz. With nitro-muriate of platina, a red ; which, by the addition of chalk, became a chefnut co- lour. With nitro-muriate of gold, a reddifh brown. With nitrate of filver, a dull red; and with muriate of filver, a lively reddifh orange. With the acetite of lead, a purple, inclining to the violet ; and with nitrate of lead, a deli- cate lively colour, between the red and cinna- mon, but inclining mod to the former. A lit- tle murio-fulphate of tin, added to the liquor in which this lad was dyed, foon changed it to a good crimfom With either the fulphate, nitrate, muriate, or aCetite of iron, cochineal produces a dark vio let, and even a full black colour, when employed in lufricient quantity. All the preparations of copper appear to fad>- den and debafe the colouring matter of cochi- neal ; and all thofe of mercury, which I have tried, do this in much greater degrees ; mod of X. them, 3 o<5 PHILOSOPHY OF them, whilft they debafe the colour, feem to an- nihilate a confiderable part of it. With nitrate of zinc, cochineal dyed a lively ftrong lilac colour ; and, With muriate of zinc, a colour like the pre- ceding, but inclining a little more to the pur- ple. Probably the iron ufually contained in zinc may have contributed in thefe inftances to incline the cochineal crimfon fo much to the blue or violet fhades, fince a purer oxide of zinc, the lapis caliminaris, being diffolved in muriatic acid, dyed (with cochineal) a fcarlet but very little inferior to that commonly pro- duced with the nitro-muriate of tin and tartar ; and upon adding a little murio-tartrite of tin to the dying liquor, it foon produced a very beau- tiful fcarlet. The pure oxide of zinc there- fore feems to approach neareft to that of tin, in exalting the colouring matter of cochineal. With different folutions of bifmuth, cochineal produced various {hades of lilac ; fome of them very lively and delicate ; but all preparations of this femi-metal, inftead of difplaying and exalt- ing the cochineal colour, tended to render a part of it latent. The oxide of bifmuth, dif- folved in ftrong vinegar, did this lefs than moll of the other preparations ; it dyed with cochi- neal a pretty good purple, and the murio-ful- phate of bifmuth, a falmon colour. With nitrate of cobalt, cochineal dyed a good purple. With nitrate of nickle, a dark lilac, inclining to the violet. With m PERMANENT COLOURS, &c. 307 With fulphate of manganefe, an orange j and With the nitrate of manganefe, a colour re- femblino; the madder red. With crude antimony, diflblved by nitric acid, cochineal dyed aCcarlet very much like that dyed with lapis caliminaris diflblved by muriatic acid, and very little inferior to the bed fcarlets given with the tin bafis ; and With Macquer's arfenical neutral fait, or the acidulous arfeniate of pot-afh, cochineal dyed a lively good purple. Such were the effects of different metallic bafes in dying with cochineal on woollens. It remains for me fhortly to offer a few obferva- tions on the effects of the feveral kinds of earths, as bafes for the cochineal colouring matter upon wool. The ufe of fulphate of alnmine, or common alum, for this purpofe, is well known. The alumine, or earth of alum, (obtained by decom- pofing and precipitating it by pot-afh from wa- ter, faturated with alum,) when thoroughly wafhed, dried, and finely powdered, did not feem capable, in repeated trials, of fixing or ferving as a bafis of the cochineal colour on wool. In this refpecl: it differed materially from the powdered calx of tin. The fame powdered alumine, however, be- ing boiled up with cream of tartar, was fo far diflblved by its acid, that with cochineal it dyed a good crimfon, though not much better than X 2 what 3 o8 PHILOSOPHY OF what may be produced with the fulphate of alumine. The fame powdered earth of alum, diflblved by lemon juice, dyed with cochjpeal a very good rich full crimfon. The fame powdered earth of alum, diflblved by nitric acid, (and forming nitrate of alum- ine,) produced a good red, inclining to the crimfon. The fame diflblved in muriatic acid (mu- riate of alumine) dyed a crimfon, differing but little from that produced with common alum. Lime water, with cochineal, dyed a purple, which took but flowly,and required long boiling. Sulphate of lime, or lime diflblved by ful- phuric acid, dyed a full dark red. Nitrate of lime, or lime diflblved by nitric acid, dyed a lively red, approaching to icarlet. Muriate of lime, with cochineal, dyed a purple. Cloth boiled in water with nitrate of lime, and then dyed in ciean water with cochineal and tin, diflblved by aqua-fortis and tartar mixed, re- ceived a good fcarlet. Cloth boiled with chalk and alum, and then dyed in clean water with cochineal, took a good crimfon, inclining to the bluifti fhade. Sulphate PERMANENT COLOURS, &c. 309 Sulphate of barytes, or ponderous fpar, not be\n<* foluble in water, could not be tried. o * Muriate of barytes, or the earth of ponderous fpar combined with muriatic acid, as a bafis for the cochineal colour, dyed a good lively pur?* pie; and Nitrate of barytes dyed a colour nearly fimi- lar, but inclining a little more to the crimfon. Magnefia alone did not combine fufficienrly with the fibres of cloth, and with the colouring matter of cochineal, to ferve as a bafis for dying. But magnefia difiblved by fulphuric acid, (forming Epfom fait,) dyed a lively purple with cochineal, though it took but flowly, and required long boiling ; and acetite of magnefia dyed a lilac colour. The filiceous earth, or powdered flints dif- folved by a violent heat in a crucible with pure cauftic alkali or pot-afh, was tried as a bafis for the cochineal colour. At firft the fibres of the cloth did not feem to have fufikient attraction for the filiceous bafis and the colouring matter, to attach and fix them properly ; but on adding a little fulphuric acid, fo as to decompofe and neutralize a part of the alkali, which had dif- jfolved and was combined with the filiceous earth, the colour took freely, and rofe to a full rich pleafing purple, in which the red or crimfon pre- dominated confiderably i and this colour after- wards proved fufficiently durable. x 3 u ¥ 3 io PHILOSOPHY OF It appears, therefore, that befides the me- tallic oxides and folutions, all the different khds of earth, i. e. the aluminous, calcareous, md filiceous, together with thofe of magnefia, ind of barytes or ponderous fpar, are capable of ix- ing and ferving as bafes of the cochineal colour- ing matter ; and we (hall hereafter find, that tiey are capable of doing the fame to other adjec- tive colours ; a fact never before afcertained, though of great importance, as well in reipect of the practical improvements which it may produce, as of the general principles and con- clufions to which it may lead us on this fubject. I have repeated nearly all the foregoing ex- periments with filk, inftead of wool, and gene- rally with effects lefs advantageous. Cochineal in- deed, with the aluminous bafis, dyes the crimfon colour as well and as durably on filk as on wool, and the modes of producing a very lafting crim- fon by thefe means are well known. The ox- ides or folutions of tin, however, do not fix and reflect the cochineal colour on filk with the fame degree of fullnefs and luftre as upon wool j pro- bably becaufe the former of thefe fubftances has lefs attraction than the latter, for the calx of tin and the colouring matter of cochineal combined together j and it has therefore been found im- poffible to dye a good lively fcarlet on filk by the means which communicate that colour to wool. The late Monf. Macquer indeed, about the year 1768, pretended to have difcovered the means of dying a fcarlet upon filk by a procefs which PERMANENT COLOURS, &c. 3 n which he publilhed in the Memoirs of the Royal Academy of Sciences for that year. Accord- ing to that procefs, he began by dying the filk firft of ?. yeliowifh orange colour, with annotta applied in the ufual way ; then he foaked it for half an hour in a diluted folution of tin, made by a mixture of two parts of the nitric, with one of the muriatic acid ; after which the filk was taken out, moderately preffed, and rinced in clean water, though he afterwards found it bet- ter to omit the rincing. To dye the filk, when thus impregnated with nitro-muriate of tin, he prepared a bath, by boiling from two to four ounces of cochineal, and a quarter of an ounce of cream of tartar, for each pound of filk, fome minutes in water; after which he added cold water, until the heat of the liquor was reduced to what the hand could bear, and then put in the filk, and dyed it as ufual, gradually raifing the heat of the dying liquor, ,fo as at laft to make it boil for a Gngle minute. I have feveral times repeated this procefs, but always found the co- lour produced by it very inferior to the fcarlets ufually dyed on woollen cloth -, and Mr. Ber- thollet hi forms us, that this was alfo the cafe at the trials which JMr. Macquer himfelf made of his procefs at the dye-houfe of the Gobelines; and in truth there was nothing of any import- ance in Mr. Macquer's fuppofed difcovery. It &ems indeed to have been chiefly borrowed from a procefs publifhed by Scheie in 1751, except- ing fofar as relates, to the colour firfi: given with annotta, and excepting a difference in the pro- portion of muriatic acid for diffolving the tin; a difference, however, which did not render the iolution in any refpeft more efficacious. X 4 If 3 i2 PHILOSOPHY OF If the murio fulphuric folution of tin, herein before defcribed, be dilutrd with about five times its weight of water, and filk be foaked in it for the fpace of two hours, then taken out, moderately fqueezed or prefTed, afterwards partly dried, and then dyed as ufual in a bath prepared with cochineal and Quercitron bark, in the pro- portion of four parts of the former to three of the latter, it will receive a colour approaching very much to a fcarlet ; and this may be made to receive more body by a farther flight immer- fion into the diluted murio-fulphate of tin, and a fecond dying in the bath from cochineal and Quercitron bark ; and if afterwards a little of the red colouring matter of fafflower be fuper- added by the ufual mode of applying it, a good fcarlet may be produced. By omitting the Quercitron bark, and dying the filk (prepared as before mentioned) with cochineal only, a very lively rofe colour will be produced ; and this may be yellowed fo as nearly to approach the fcarlet, by adding a large proportion of tar- tar to the cochineal in the dying veflel, With lime water as a mordant, cochineal gave to filk a very agreeable purple j with muriate of barytes, a lively delicate lilac colour ; with mu- rio-fulphate of bifmuth, a falmon colour j and with nitrate of cobalt, a very lively and beautiful purple; with nearly all the other metallic and earthy bafes, cochineal produced fimilar but paler colours on filk than on wool, Refpecling cotton, my readers will recoiled that I have already (at page 195) noticed the little attraction which this fubftance exerts upon the PERMANENT COLOURS, &c. 313 the cochineal colouring matter, united with the folutions or oxides of tin. To illuftrate this, Monf. du Fay caufed a piece of cloth to be ma- nufactured from a mixture of wool and of cot- ton, which having undergone the ufual procefs for dying fcarlet, became, as he defcribes it, " marbree de couleur de feu & de blanc," (marbled with white and fire colours,) the cot- ton remaining perfectly white, though the wooJ was dyed fcarlet ; and he found a like want of attraction between cotton and the colouring mat- ters of kermes, gum lacca, &c. He moreover found that a fkain of white woollen yarn, and another of cotton, being at the fame time, and in an equal degree, fubmitted to the action of the fame preparation and dying liquors which are commonly employed for fcarlet, the woollen yarn received the mod beautiful fcarlet, or, as he terms it, "fire colour" whilft the cotton re- mained as white as at firft *. Similar effects have frequently occurred to me, and I have clearly perceived them to arife, not becaufe the cotton is not capable of imbibing the fcarlet dye, but becaufe, having a weaker attraction for it than that which wool exerts on the particles of that dye, the latter draws and exclufively ap- propriates to it/elf all the colour contained in the dying liquor; though when cotton is fubjedted to the fame procefs by itfelf, freed from the inter- ference of a fuperior attraction from wool, it takes a fcarlet colour, as I know by repeated trials, more (lowly indeed, and paler, than that which is ufually imbibed by woollen cloth. It %s t perhaps, owing to this weaker attraction be- * See Mem. de l'Acad. R« des Sciences, &c. 1737. tween 3 i4 PHILOSOPHY OF tv/een the fibres of cotton and the fcarlet dye, that the latter is fo much lei's permanent 01 cotton than on wool; and it is alio from this want of fufficient attraction, that the cochi- neal colour is found to take molt beneficially on cotton, when the bafis has been firfi applied Separately. Scheffer, in 175 r, recommended the dying of fcarlet on cotton in this way, by firft foaking it in a diluted nitro-muriate of tin, and after- wards dying it with cochineal ; but the colour being fugitive, little or no ufe was ever made of the procefs ; though the late Dr. Berkenhout probably availed himfelf of it fome years after- wards, when he pretended to have difcovered the means of dying " fcarlet, crimfon, and i> cither by the indigo vat, or by the compofnion for Saxon blue, i. e. fulphate of indigo. And having applied this latter by the common mode of dying, to cloth which had previoufly received the I PERMANENT COLOURS, &c. 339 V)c Quercitron yellow, and alfo to cloth dyed yeltow with the Lombardy poplar, (which in tther refpe&s he greatly commends,) he found that the former which had received the bark yellow, took a fine dragon green, (" un beau « vert dragon,") and the latter nothing better than a greenifh olive. It is true that Mr. Dam - bournay computes the expence of dying with the Quercitron bark as greatly furpaffing that of dy- ing with the Lombardy poplar. But his com- pulation was founded on very erroneous fuppo- fitions, joined to the circumftance of his calcu- lating the muriatic acid to coft near two fhil- lings and fixpence fterling the pound weight, which is more than fix times its real coft; tho' this may probably have been nearly the price which it bore in France, whiift the Co.belle fub- fifted there. The nitro muriate of tin, (dyer's fpirit,) tho* it produces good yellows with Quercitron bark, produces them in a much weaker degree than the murio fulphatc of that metal ; which is realty the cheapeft, and moft efBcacious, of all the fo- lutions or preparations of tin, for dying the Quercitron as well as the cochineal colours. The fulphuric acid by itfelf diftblves, or ra- ther calcines, a large portion of tin, if allowed to act upon it for any confiderable time ; and this folution joined to the bark, with alum and tartar, produces bright ftrong yellows on cloth, though 1 think they appear lefs foft and beautiful, than thofe dyed either with the muriate, or murio fulphate of tin. This metal diflblved, or rather calcined, bv a mixture of the nitric and fulphu- Z % ric 346 PHILOSOPHY OF ric acids, is (till lefs fuitable for dying with the bark. Tin diflfolved by muriatic acicf, to which one third of its weight of clean white tartar had beert previoufly added, produced a very bright and delicate yellow with the bark, upon cloth, and •this, by longer boiling, was raifed to a full and beautiful orange. Tin diffblved in ftrong nitric acid, (double aqua fortis,) with an addition of one third of its weight of tartar, alfo pro- duced a very good yellow, though fomewhat inferior to the laft. Upon putting tartar, with a portion of tin, into a glafs veffel with ftrong colourlefs fulphuric acid, the latter, or rather its oxygenous part, by combining with the inflammable part of the tartar, immediately rendered the mixture as black as ink; and the folution of tin produced by it, was found of but very little ufe as a mordant for dying with the bark. A folution of tin, by the oxygenated muriatic acid, whilft fecluded from light, retains its oxy- genous part, and with it the power of weaken- ing a great number of adjective colours ; a power which depends neither upon the oxygene, nor the muriatic acid feparately,. but upon the new properties which they acquire by com- bination. The oxyd of tin, produced by the. action of the nitric acid upon that metal, con- tains a large portion of oxygene; and yet ic raifes, inftead of weakening the Quercitron yeU low: but when this oxyd is diffolved in muri- atic acid, it produces only a very feeble lifelefc yellow wsra PERMANENT COLOURS, &c. 341 yellow with bark ; though tin not previously oxy- genated will, when dhTolved by the fame (mu- riatic) acid, act mod powerfully in exalting the Quercitron yellow : which proves, that this de- fect of colour does not refult from the prefence of oxygene alone, but from its combination with muriatic acid. The defect in this cafe is exactly fimilar to that which occurs when tin, diffolved by oxygenated muriatic acid, is em- ployed with the bark ; and in both cafes, the very feeble yellows produced, refemble that which I have defcribed in the laft chapter, as refulting from the ufe of tin, diflblved by muriatic acid, oxygenated by the addition of about one third of its weight of nitric acid : a fimilar effect was alfo produced by employing tin calcined by ful- phuric acid, and then diiloived in the muriatic, as a mordant widi the bark. Cloth boiled in water with the muriate of tin and tartar, has fometimes been made yellow, and fometimes of a chefnut brown, only from the action of this mordant, unaffifted by any colouring drug. Thefe difcolorations feem to de- pend upon the particular ftate of the cloth, as be- ing more or lefs freed, either from the natural fwint of the wool, or the greafe commonly applied to it for particular purpofes. Difcolorations of this kind are not eafily removed; they vvithftand the action of fun and air for a confiderable time, and if cloth lb difcoloured be dyed with either bark, or with cochineal, the colour will appear tarnifhed ; for which reafon the application of muriate of tin, with tartar only, as a mordant, ought to be avoided, unlefs the dyer be very Z 3 certain r 342 PHILOSOPHY OF certain that the cloth has previoufly been per* fectly well fcoured. A few lumps of the dry oxyd of tin men- tioned at page n8, having been finely powdered and mixed with a fuitable quantity of decoct ion of Quercitron bark, the mixture was found capable of dying a very full and bright yellow upon wool- Jen cloth. The colour however being expofed to the action of fun and air, very foon acquired a brownifh complexion. Some of the fame oxyd of tin reduced to powder, having been wafhed in warm water, to remove the adhering acid, as far as water could"' remove it, was found to be ftill capable of combining with the colouring matter of the bark, fo as to dye cloth yellow ; efpecially when the oxyd had been previoufly fufFered to remain mixed with the decoction of bark, for fome hours, in a warm fituation. Cotton alfo took a yellow colour by dying in this mix- ture ; but it was eafily removed by wafhing with, foap, and therefore was I think only applied fu- perficially, I have but little to offer refpefting the life of copper, or rather of the oxyd and folutions of that metal alone, as mordants or bafes for dying with Quercitron bark on wool or cloth. Their general effect; is to raife and fix the Quercitron yellow ; but at the fame time to give it a greenifh or rather an olive complect ion. Wool dyed with a tenth of its weight of bark, and half as much fulphate of copper, received an agreeable colour, between the yellow and the olive. The bark, with muriate of copper, feemed to im- part but little colour to wool for fome time 3 but a little PERMANENT COLOURS, &c. 343 little chalk being added, a full yellowifh olive was produced. This alfo proved to be the cafe, when nitrate of copper was employed with the bark, until chalk had been added ; and then the wool fpeedily imbibed a yellow, delicately inclin- ing to the olive hue. Verdigrife with the bark produced a yellowifh olive on wool; which, by the addition of chalk, was brightened, and made to approach nearer to the yellow. Thefe colours appeared to be fufticiently lafting. Drab colours of various fhades may be mod expeditioufly and cheaply dyed by the Querci- tron bark, and an iron bafis. For this purpofe the bark may be boiled a few minutes in a cop- per veffel, with one half, one third, or one fourth of its weight of fulphate of iron, (copperas,) ac- cording to the (hade required, and the liquor having been well mixed, and a little cooled, the cloth may be dyed therein as ufual; but with- out any other preparation than that of fcouring and moiftening. To fadden and darken the co- lour Hill farther, a little fumach, (thus coriaria,) may be added with the bark ; and on the other hand, the colour may be inclined to the olive and yellow, by diminishing the quantity of ful- phate of iron, and employing with it a little alum and chalk; or (which is better) a little fulphate of copper, with or without a fmail pro- portion of chalk. Or the cloth may be firfb turned a few times through a veffel, with boiling bark liquor, then taken out, and turned brifkly through a veffel with hot water, in which a fuitable proportion of fulphate of iron has been difibived, with or without either alum and chalk, or fulphate of copper and chalk, as the particular colour Z 4 intended 344 PHILOSOPHY OF Intended to be given may require. In eider 1 way the colours will prove lading, and the tx- Eence very fmall ; four or five pounds of bark eing generally fufficient to dye one hundied pounds weight of cloth, of the colours in qutftion. Cloth prepared by previous boiling, with aie twentieth of its weight of fulphate of iron, and one fourth of that quantity of chalk, and then dyed in bark liquor, became of a ftrong durable chocolate colour; but in this way great care is neceiTary to render the colour even. Cloth prepared by boiling with a twentieth of its weight of fulphate of iron, half as much Tea fait, and one fourth of that quantity of chalk, and then dyed with bark, received a very lading dark brown colour. Cloth dyed with Quercitron bark, fulphate of iron, and fulphate of manganefc, in fmall pro- portions, became of a light but pleafing drab colour; which, by the addition of a little chalk, was afterwards changed to the cinnamon. Cloth prepared with nitro muriate of gold, and dyed with bark, became of a delicate olive tinged yellow. Thefolutions of bilmuth, zinc, antimony, filver, mercury, lead, and platina, by different acids, produced various fhades of brown, yellowifh brown, brownifh yellow, cin- namon, drab and olive colours; of which it is not expedient to give my readers a particular de- fcription; becaufe they either may be all more cheaply obtained by other mordants, or are not likely to be brought into ufe, Cloth mm PERMANENT COLOURS, Sec. 345 Cloth boiled in water, with one twentieth of its weight of fulphate of lime, and dyed with Bark, received a ftrong nankeen colour. Ni- trate of lime in this way, produced a nutmeg brown ; and the muriate of lime produced a very full and lading drab colour, which in fome re- fpedb may be preferable to the drabs given by an iron bafis, and especially as being lefs likely than the latter to injure the texture of the cloth. Of the Properties and Ufes of Quercitron Btrk in dying upon Silk. ALL the different fhades of yellow, com- monly dyed upon filk from weld, may be ob- tained with equal facility and beauty, and more cheaply, by employing the bark in its Head, af- ter the rate of from one to two pounds for every twelve pounds of filk, according to the particu- lar made of colour wanted. For this purpofe the bark, powdered and tied up in a bag, fhould be put into the dying veflel whilft the water is cold, and as foon as it becomes a little more than blood warm, the filk, previoufly alumed, mould alfo be put in and dyed as ufual ; and where the higher yellows are wanted, a little chalk or pearl allies may be added towards the end of the ope- ration, as mentioned for the dying of wool. Where fhades of yellow more lively than any which can be given either by weld or bark with the aluminous bafis only, are wanted, it will be advantageous to employ a little of the murio ful- phate of tin j and but a little of it, becaufe the 1 1 calx 54^ PHILOSOPHY OF :alx of tin, unlefs fparingly ufed, always dim:- nilhes the gloffinefs of filk. To produce the fhades in queftion, it will he fufficient to boil after the rate of four pounds of bark, with three pounds of alum and two pouncs of murio fulphate of tin, with a fuitable quantity of water, for ten or fifteen minutes, and the heit of the liquor being afterwards reduced fo that the hand can bear it, the filk is to be put in and dyej as ufuai, until it has acquired the proper (hade, (which it will do fpeedily,) taking care, however, to agitate the liquor conftantly, that the colour- ing matter, which would otherwife fubfide in a considerable degree, may be kept equally dif- perfed through the liquor. By adding fuitable proportions of fulphate of indigo to this yellow liquor and keeping it well ftirred, various and beautiful fhades of Saxon green may be dyed in the fame way very equally and cheaply. The Shades intended to incline mod to the yellow mould be firfl: dyed, and afterwards, by adding more fulphate of indigo, thofe partaking more of the blue may be readily produced ; and indeed nothing can be more commodious or certain than this way of dying the moft beautiful Saxon greens upon filk. By difiblving different proportions of copperas or copperas and alum, in the warm decoction of bark, filk may in the fame way be dyed of all the different (hades of olive and drab colours; and other varieties may be produced with the bark generally, by employing the fame means which are ufed to pioducc the like variations with weld. Of PERMANENT COLOURS, fcc. 347 Of the Application of Quercitron Bark to the Fibres of Linen or Cotton, either woven or Jpun y by general Dying. I here ufe the term general dying as oppofed to that partial or topical application of colours on which callico-printing chiefly depends. At pages 62 and 62 of this volume I have endea- . youred to explain the caufes which render adjec- tive colours lefs durable on linen and cotton than they are on wool or (ilk, fo far, at lead, as thefe caufes depend on differences in the ftructure and chymical properties of the fubflances in quellion ; but whether my explanation be well founded or not, this at lead is certain, that the attraction between the aluminous bafis, and the fibres of linen and cotton is much weaker than that which fubfifts between the fame bafis, and the fibres of wool or of filk ; and this want of a fufficienc attraction or affinity has made it neceflary toem- ploy extrordinary means for precipitating the alu- mine more copioufly, and fixing it more firmly than it otherwife would be precipitated and fixed upon the fibres of linen or cotton, in order to enable them to receive permanent adjective co- lours by dying. The principal of thefe means are certain oily and animal mattersjoined to fome vegetable aftringents, particularly galls; all of which, I mean the former, as well as the latter, evidently poffefs a ftrong attraction for alumine, and when united to linen or cotton, produce yery beneficial effects, as is manifeftly feen by the procels for dying the Adrianople or Turkey fed, concerning which both Mr. Henry and Mr. Berthollet 348 PHILOSOPHY OF Berthollet have publifhed feveral very ingenious as well as highly interefting obfervations ; and perhaps I may be able to add fomething to thefe when treating of this fabjedt in my next volume; atprefent, however, I ih ill onlv notice thefe ex- traordinary means fo far as they feem likely to im- prove the beauty and durability of the colours, capable of being communicated to linen or cot- ton from Quercitron bark. The fibres of linen or cotton when fpun or wo- ven are prepared for the dyer by being firft boiled in water with a fuitable portion of potafh, (which for linen fhould be made caulVic, in order that it may act more ftrongly upon the oily and refi- nous matters abounding in flax,) and afterwards bleached by expofure upon the grafs to fun and air. But as this operation commonly leaves a portion of earthy matter in the linen or cotton, which, by being unequally diftributed, would ren- der any colour given by dying unequal; the cot- ton or linen ought to be foaked or fteeped in wa- ter, foured by fulphuric acid, to diffblve and re- move this earthy matter, taking care afterwards to wafh or rince ofF the acid, left, being con- centrated in the cloth or yarn when drying, it fhould injure the texture. The method prefcribed by the French regula- tions, and adopted in moft European countries, for dying yellow upon linen or cotton from the weld plant is, by foaking the cloth or yarn in a liquor made by diflblvingone fourth of its weight of alum in as much water as is neceffary for that purpofe ; to which it will be highly advantageous to add after the rate of onepound of clean potafh, or - PERMANENT COLOURS, &c. 349 or ten ounces of chalk, for every fix or (even pounds of alum (1) to neutralize the excefs of acid contained in the alum, and promote a fepa- ration of its earthy bafis. The cloth or yarn hav- ing been thus foaked, is taken out of the alum liquor, and well dried ; and being afterwards rinced, it is to be dyed in weld liquor made by boiling about one pound and a quarter of the plant for each pound of cloth or yarn ; which, after having received a fufficient body of colour, is to be taken out of the dying liquor, and foaked for an hour and more in a folution offulphateof copper (blue vitriol) containing after the rate of three or four ounces of the latter for each pound of cloth or yarn ; it is then to be removed, and without being wafhcd, put into a boiling folution of hard foap, containing in like manner three or four ounces of foap for each pound of cloth or yarn, in which it is to be well ftirred and boiled for about three quarters of an hour or more, then wafhed and dryed. I have found by repeated trials that this mode of precipitating the calx of copper upon the yellow previoufiy dyed from weld with an aluminous bafis, renders the colour more durable, but at the fame time gives it a, darker complexion. And I have found fimilar effects where bark was ufed inftead of weld ; the colour dyed with the bark in this way having proved in every refpect as good as that obtained from (1) HaufFman fays, that when English alum is diffolved in five times its weight of water, and one eighth of its weight of chalk is added to faturate the excefs of acid, a folution will be produced which does not cryftalize in Sum- mer, and bu: little in Winter ; though without chalk it re- quires fixteen times as much water as cf alum to make a permanent folution. 3 So PHILOSOPHY OF from weld : but I am convinced, that vvhetfietf the colouring matter be taken from the former or the latter of thefe vegetables, the yellow dyed in this way never is either fo beautiful or fo lad- ing as that partially given by callico-printers from the fame vegetables, and which the dyers might readily give with equal perfection, by only em- ploying the acetite of alurnine, or aluminous mordant, defcribed at pages 176, 177, and 178 of this volume; and this more cheaply as well as more expeditioufty than that produced by fol-^ lowing the French regulations ; confidering the expence of fo much bine vitriol and foapas they require, and which may be rendered unnecefiai y by adopting the calico-printer's aluminous mor- dant. The beft method of applying the alu mi nous mor- dant for general dying with Quercitron bark (which I moft earneftly recommend whenever bright and durable yellows are wanted,) is as follows, viz* Take a fufficient quantity of the acetite of alurnine, which for this purpofe may be made by diffolving aftef the rate of only one pound of in ^ gar of lead and three pounds of alum, as at p 177, excepting only that it need not be thickened > and mix this liquor with an equal quantity of warm water, then let the linen or cotton (pro- perly cleanfed as before mentioned) be thorough- ly wetted and foaked in the mixture, which ough t to be about blood warm, for the (pace of two hours, then taken out and moderately preffed oir fqueezed over a proper veffel to collect wha t might otherwife drop or run off, and prevent an unncceilary wade of the aluminous liquor ; and thiss PERMANENT COLOURS, &c. 3*1 this being done, let the linen or cotton be well dried in a ftove heat, where it can be conveniently applied, and then foaked again in the aluminous mordant, and again preffed or fqueezed and dried as before ; afcer which, without having been rinced, let it be thoroughly wetted in as much, and only as much lime water as will convenient- ly fuffice for that purpofe, and afterwards dried j and where a very full, bright, and durable yellow is wanted, it may be well to foak the linen or cot- ton a third time in the diluted aluminous mor- dant, and after drying, wet it a fecond time with lime water, and dry it again : but in either cafe, the linen or cotton after its laft dying, fhould be well rinced in clean water, in order to feparate any loofe or unfixed particles of the mordant or bafis, which otherwife might do harm in the dy- ing vefifel. The lime-water employed in this way, anfwers the purpofe of producing a more copious depofition of thealumine in the fibres of the linen or cotton, and it moreover fuperadds a portion of calcarious to the aluminous bafis ; an effect which is not without confiderable utility. I have found, that when the aluminous liquor has been employed at a fcalding heat, the colour afterwards produced was not fo good as what re- fults from liquor only made blood warm ; the pores of linen and cotton being fo open as not to require any diftenfion by a gt eater degree of heat. The cotton or linen being prepared and rinced as before mentioned, a fmall fire is to be lighted under the dying pan or veffel, previoufly fupplied with the ufual quantity of water, and the pow- dered 35* PHILOSOPHY OF dered Quercitron bark tied up in a bag, after th<* rate of from twelve to eighteen pounds for every hundred pounds weight of linen or cotton where full bodied yellows are wanted, is to be put in, whilft the water is cold, and immediately after it the linen or cotton is alfo to be put in, upon ftick9 if it be thread or yarn, or, if piece-work, on the winch, agitating or turning it in either cafe as ufual for the fpnee of an hour or an hour and a half, during which the water fhould gradually become warm, but not warmer than the hand can bear. When this time has elapfed, the fire may be increafed, and the dying liquor brought to a fcakiing and thence to a bo;ling heat; in which it will be fufficient to lee the cotton or linen remain a few minutes only, when a bright lively yellow is wanted, becaufe longer boiling always gives the yellow a brownifh caft, what- ever vegetable may be employed in dying ir. The linen or cotton having thus acquired fufficienc colour, is to be taken out, rinced and dried as ufuai. When the colour of Quercitron bark is flowly raifed in this manner by a very moderate hear, the colouring particles feem to adjuft themfelves more accurately and unite more intimately to thofe of the bafis, and thereby to produce a co- lour more fixed and durable than it is when they* are haftily accumulated by a boiling heat, and perhaps chiefly upon the fui face of the iubftance dyed and of the bafis combined therewith. All the different (hades of yellow may in this way be dyed from Quercitron bark j if it be u fed fparingly, with a very moderate heat, and the operation PERMANENT COLOURS, &c. 353 operation continued only for about half an hour, a pale though lively yellow will refult ; if ufed more copioufly, and the operation continued fomewhat longer, a fuller Colour will be pro- duced ; and this may be raifed higher and higher according as the heat and proportion of bark are increafed and the dying operation prolonged, fo as indeed to produce a very dark brownim yel- low if the liquor be made to boil for half an hour. Pieces of cotton having been prepared with the printers' aluminous mordant and lime water, as already defcribed, were dyed one with bark and another with weld, and being taken out of the dying liquors, a bit was cut off from each and the remainder put back again into its liquor, in which a fmall quantity of fulphate of copper had, in the mean time, been diffolved, after the rate of one ounce to five pounds of cotton ; and the liquors being nearly of a fcalding heat, in about ten minutes the pieces were again taken out and found to have acquired a brownim com- plexion j but being expofed to the fun and air along with the bits which had been cut off before the fulphate of copper was added to the dying liquors, the brownim complexion of the former foon drfappeared, and their remaining colour at the end of four weeks proved to be rather better than that of the bits dyed without the fulphate of copper. It feems therefore probable, that a fp.iring ufe of the latter in this way, may contri- bute fomething at lead to the durability, if not to the beauty of yellows dyed upon linen or cotton, after the application of acetile of alumine and of lime as before directed. Aa When w 354 PHILOSOPHY OF . When the aluminous mordant is employed without any addition of water, it may be fuffi- cient to fbak the cotton therein once only, and after dying to immerfe it once in lime water, then dry, rince, and dye it as before mentioned. I think, however, that better effects refult from the application of a more diluted mordant, at two different times -, and indeed I have found, that by immerfing the cotton a greater number of times alternately in the diluted aluminous mordant and in lime water, and drying it after each immerfion, the colour always acquired ftill more body and durability. At page 183 I have remarked, that by the Eaft Indian method of callico-printing, the want of acetile of alumine is fupplied by impregnating cotton with the aftringent matter of yellow my- robalans, and with certain oily and animal fub- ftances, which enable the cotton, when a folu- tion of alum is afterwards applyed to it, to de- compofe and imbibe a larger portion of alumine: ^nd this practice may be imitated in dying the Quercitron yellow upon cotton, with fo much advantage as to render the acetile of alumine in a great degree unnecefTary, at lead where the yellow is not required to be very clear and bright. Inftead of myrobalans, (which are, however, to be found here,) the Alleppo galls may be em- ployed, choofing always the whitell for this ufe, becaufe the browner might (lain the cotton, fo as to render it incapable afterwards of receiving a bright, clear yellow ; and perhaps in this refpect the roots of at leaft two or three fpecies of North American PERMANENT COLOURS, Sec. 355 American fumach, particularly the Rhus Gla- bra Lin. might be preferable even to the whiteft galls, by communicating lefs (lain and producing equally good effects, as I have found them to do in repeated trials. The beft method of employing galls for this purpofe is, I believe, to boil after the rate of one pound of them coarfely powdered, with half a pound of Barilla, for the fpace of one hour, in two or three gallons of foft water, and then {training off the decoction to macerate the cotton an hour or two therein : barilla, or rather the foda which it contains, enables the water to extract the af- tringent matter of the galls much more copiouf- ly than it otherwife could do ; and being itfelf imbibed by the cotton, it alfo occafions a more plentiful depofition of alumine, when the cotton is afterwards put into a folution of alum, which, for this ufe may be made by diffolving eight pounds of alum and one pound of chalk in fix gallons of water. In this calcarious folution of alum, the cotton, after being taken out of the decoction of galls and dried, is to be foaked for two hours, then taken out and dried; then foaked a few minutes in lime water, and having been again dried, it is to be immerfed a fe- cond time in the calcarious folution of alum j af- ter which, being again dried and well rinced, the cotton is to be dyed flowly with the Querci- tron bark, as before directed. In this way very full bodied and lading yellows may be obtained, which will bear repeated wafhings with foap, as well as expofure to fun and air; and the 'ac- tion not only of ftrong vinegar, but of the oxyge- nated muriatic acid. A a 2 By 356 PHILOSOPHY OF By difiblving after the rate of one pound of hard white foap and half a pound of barilla in three gallons of water, and macerating the cot- ton therein, as directed to be done wrth the de- coction of galls and fumach, then drying and im- merfing it in the calcarious folution of alum, and afterwards proceeding, as juft directed to be done after fuch immerfion, I obtained a colour (with the bark) nearly as durable as when the decoction of galls had been ufed, and with the advantage of its not being thereby darkened. A pound of the yolks and whites of eggs hav- ing been firft beat up with an equal quantity of brown fugar, and then with two gallons of water, and cotton having been foaked therein, inftead of the folution of foap and barilla, then dryed and immerfed in the calcarious folution of a- lum -, dried again and immerfed in lime wa- ter, and then in the folution of alum, and afterwards rinced and dyed with bark, as al- ready defcribed, it received a very full and lad- ing though darkifh yellow colour. The animal mucilages in general, and fomeof the vegetable, being diflblved in water and applied to cotton in the fame way as the yolks and whites of eggs juft mentioned, produce the like good effects, and more efpecially the animal glues, which appear to unite both with the cotton and the aluminous bafis when ufed in this way. A considerable time has now elapfed fince I was induced to try the effects of alumine com- bined with other acids befides the fulphuric and acetous, and alfo with potafh, foda and ammoniac, both in their mild and their cauftic dates, as a bafis or mordant for the Quercitron colouring matter. ^■^r PERMANENT COLOURS, &c. 257 matter. To feparate alumine from the fulphuric acid with which it forms common alum, this laft compound may be diflblved in about eight times its weight of clean boiling water, and mixed with a filtered lixivium of clean potafh, which fhould be added to the folution of alum gradually, until it no longer makes the liquor turbid, or occafions any farther precipitation ofalumine. The whole of the mixture may then be put into a canvafs drainer to feparate the fluid part, and this hav- ing been done, boiling water may be poured re- peatedly upon the remaining moid alumine, and differed to run through the drainer until the fa- line part of the mixture fhall have been wafhed away, as far as it is capable of being wafhed. away by water j the alumine being then taken out and dried, will generally be found to weigh about one fifth part of the weight of the alum employed to produce it : when thoroughly dried, the alumine contracts or Ihrinks greatly, and be- comes at length fo hard, that neither drong ful- phuric or nitric acids can diflblve it, except with great difficulty and very dowly ; and for this rea- fon it ought always to be employed in a moid date when intended to be again diflblved by any acid or alkaline mendruum. Perhaps the great difpofition of this earth to contract or fhrink by drying, may be one reafon why it is generally mod advantageous to convey and fix the particles thereof as a bafis in the pores of linen or cotton, Jirft feparately, and afterwards when they have flirunk by drying, to fuperadd the adjective co- louring matter, which may then find more fpace, and combine with the alumine in greater propor- tion than it could do when both previoufly united, were applied together, whild the particles of alu-^- mine were enlarged by moidure, A 33 If 358 PHILOSOPHY OF If moid alumine obtained in the manner jufV defcribed, be diflblved in either the nitric or mu- riatic acids, it will by evaporation afford cryftais j and thofe obtained with the nitric acid, by at- tracting moifture from the atmofphere, will prove deliquefcent, unlefs kept in a veflel clofely flopped. M. Berthollet found, that in thefe cafes, the cryftais depended on a remnant of ful- phuric acid, which always adheres to alumine when feparated in the way juft defaibed; and that by afterwards digefting it for fome time in a folution of potato, or of ammoniac, this adher- ing fulphuric acid might be decompofed ; and that the alumine being then diflblved either in the nitric or the muriatic acid, no cryftais were pro- duced. It muft, however, be remarked, that the alumine mentioned to have been employed in the fucceeding trials, was obtained in the way firft defcribed, and therefore was not completely divefted of fulphuric acid. Having boiled a fuitable portion of moift alumine with a decoction of Quercitron bark during the fpace of half an hour, I attempted to dye both wool and cotton therewith, in order to fee whether the undiflblved particles of alumine, fo united to the colouring matter of the bar k, would become the bafis of a lafting colour. I found, however, by repeated trials, that cottion in this way could only be made to imbibe a p;ale yellow, which probably adhered to the furfaice only of its fibres, becaufe it was nearly deftroyed by a fingle week's expofure to the fun and aiir. Wool, however, in this way received a browniifh yellow of fufficient body and confiderable dura- bility. Ammoniiac, PERMANENT COLOURS, &c. 35^ Ammoniac, or volatile alkali, whether mild Of cauftic, appears to difiblve alumine fo very fparingly, that hitherto I have found no confide- rable benefit from any folution of this kind as a mordant. Nor have I fucceeded much better with either the carbonated (mild) potafh, or that of foda, their action not being confiderable upon the earth of alum. But if this earth, obtained by precipitation and wafhing as before men- tioned, be digefted whilft moid with a ftrong lixivium either of potafh or of foda, in its pure or cauftic ftate, in a mattrefs placed on a fand heat, nearly approaching that of boiling water, it diflblves very copioufly, and may afterwards, by evaporation, be made to cryftalize. The celebrated Macquer appears to have believed that very beneficial effects might be obtained in dying by thefe combinations, and more efpecially when ufed as mordants for the madder red on cotton. It feems evident, however, that he was greatly miftaken reflecting the true nature of thoie ope- rations upon which this belief was founded ; and that in the procefs for Turkey reds, where he fuppofed the durability of colour to refult prin- cipally from a combination of this kind, no fo- lution of aluminous earth by any alkaline men- ftruum could have taken place; and though Mr. Hauffman appears alfo to have formed confide- rable expectations of advantage from the appli- cation of thefe folutions of alumine by potafh or foda, I have been led by the refulcs of many trials, to concur in opinion with Mr. Berthollet, that but little good is to be expected from them, un- lefs it be under the circumftances which I (hall prefently explain, becaufe the alkaline men- firuum evidently has too much affinity to the A a 4 particles 3 6 ° PHILOSOPHY OF particles of alumine to allow of their being de-» pofited and fixed in the fubftance, to be dyed fo copioufly as is neceflary ; and I have repeatedly found, that after having foaked cotton a fufHcient time in the diluted folution of alumine by either potafh or foda, the bafis was almoft wholly car- ried off or removed by only rincing the cotton in water to fit it for being dyed, and that only very feeble colours could be raifed upon what remain- ed of the alumine as a bafis. This was more efpecially the cafe where the folution of alumine had been made by potafh, which by attracting moifture from the atmofphere, rendered ic diffi- cult to dry the cotton fufficiently when impreg- nated therewith, ar leaft without artificial heat. Thefe defects were, however, removed, and a •very excellent durable yellow produced by putting the cotton which had bo.tnfirfi foaked in a dilu- ted folution of alumine by potafh, inro water which had difTolved as much common alum as it could retain, whilft blood warm, macerating and turning it therein for the fpace of half an hour, (during which the potafh and fulphuric acid com- bining, each precipitates the alumine of the other,) then drying the cotton, and afterwards immerfing it in lime-water; then drying again, rincing and dying it with the bark as before di- rected. The yellow given in this way faded but very little by two months expofure to fun and air in the midft of the Summer -, nor was it fenfibly weakened by the action of (bong French vinegar, or of the oxygenated muriatic acid. The folution of alumine by foda produced equal- ly good effects in this way. i Nitrate PERMANENT COLOURS, &c. 361 Nitrate of alumine (made by faturating the nitric acid with moift alumine as before men- tioned,) being diflblved in eight times its weight of water, and ufed infteadof the folution of com- mon alum lafc mentioned, produced a yellow rather better and more durable even than the laft. Cotton which had received no impregnation, be- ino- macerated in a like folution of the nitrate of alumine, then dried, immerfed in lime water, rinced and dyed with the bark, received a yellow confiderably better than I could obtain with a fo- Jution of common alum in the fame way. Muriate of alumine generally produced with the bark, effects as good, but not materially better than thofe refulting from common alum ufed in the fame ways. In dying any of the yellows before mentioned with bark, the colour may be railed to an orange by employing a fuitable proportion of madder along with the bark. It can hardly be neceflfary for me to mention, that linen or cotton, either fpun or wove, when previoufly dyed blue of a fuitable made in the nfual ways, will be rendered green by fuperad- ding the Quercitron yellow in the ways, and by the means already directed for dying this yellow upon linens and cottons not previoufly made blue, taking care to proportion the quantum or body of each of the component blue and yellow colours to the particular (hade of green which they are intended to compofe or produce. Linen and cotton foaked four hours in a mor- idant made by diflbjving lime in muriatic acid, and 362 PHILOSOPHY OF and mixing the folution with fix times its weight of water, afterwards dryed, rinced, and dyed with Quercitron bark, took a full drab colour which refilled the action of fun and air for acon- fiderable time: but neither the fulphate nor the nitrate of lime employed in this way with the bark, gave any thing more than buff or flight pankeen colours of little durability. Magnefia dilTolved by the fulphuric, the ni- tric, muriatic, and acetous acids, and ufed in this way as a mordant, produced, with bark upon linen and cotton, weak drab, cinnamon, and nankeen colours, which, however, proved too fugitive to be of any ufe. Cotton foaked in a diluted folution of flints, made as mentioned in a former part of this vo- lume, and afterwards rinced and dyed with the bark, became of a nankeen colour fomewbat lading. Among the metallic bafes, that of tin might naturally be expected to produce the molt benefi- cial effects by general dying upon linen and cot- ton with the Quercitron bark ; but hitherto my experiments therewith, though they have been very numerous and greatly diverfified, afford no fuccefsful refuks : for though different folutions of tin, (particularly the nitro-muriatic and the murio-fulphuric,) when diluted and applied as mordants to linen and cotton, enable thefe fub- ftances aftei wards.to imbibe yellows exceeding all others in brighmefs, luftre, and beauty j and though thefe yellows are capable of refilling the action of boiling foap fuds, as well as of ftrong acids. PERMANENT COLOURS, &c. 363 acids, not excepting the oxygenated muriatic acid, yet they decay very fpcedily when expofed to the fun and air, fo as even to fuffer more in a Tingle week than the Quercitron yellows dyed upon an aluminous bafis commonly fuffer in a month. The tin bafis is, moreover, accom- panied with this ftngular circumftance, that when applied feparately to the linen or cotton intend- ed to be dyed, and when thefe fubftances, after the ufual drying and rincing, are dyed with the bark, the colour, (contrary to what happens with the aluminous bafis,) proves much more fugitive than itdoes when the folution of tin and decoction of bark are firft mixed together, and afterwards applied to the linen or cotton profub- ftantively ; nor have I ever been able to apply any of the folutions of tin even in fmall quantities mixed with an aluminous mordant upon linen or cotton, without perceiving that the colour after- wards obtained thereby from bark was much kfs durable in refpect to fun and air, than it would have been with an aluminous bafis only. I fhall, however, abftain from giving any opinion re- flecting the cauie of thefe defects, until the re- fults of fome nice and difficult experiments, which fucceffive interruptions have hindered me from bringing to a fatisfactory conclufion, fhall enable me to do fo on better grounds than I pof- fefs at prefent. Zinc diffolved by different acids, and em- ployed as a bafis for dying with Quercitron bark on linen and cotton produces brownifh yellows, inclining more or lels to the olive and drab co- lours ; they feem, however, lefs durable than the like colours, which may be more conveniently and BED 3 6 4 PHILOSOPHY OF and cheaply given by fubftituting folutions of alum and of iron, mixed in different proportions, as mordants. Bifmuth being diiTolved in nitro muriatic acid, and the folution afterwards fufficiently diluted by water, and cotton being foaked therein for two hours, then immerfed in lime water, dried, rinced, and dyed with Quercitron bark, it took a very high and full, but at the fame time a very brownifh yellow, of confiderable durability. Copper diffolved in the fulphuric, the nitric, muriatic, and acetous acids, and afterwards fuf- ficiently diluted with water, being applied to linen and cotton as a mordant, enables them to obtain from Quercitron bark by dying, different ihades of full but brownilh yellow, which, how- ever, does not long bear warning with foap, or expofure to rain, funfhine, and air; the oxyd of copper, on which the colouring matter is ap- plied, being readily aded upon by all thefe agents. Soaking the linen or cotton in lime water when impregnated with the oxyd or folution of copper, previous to the dying with bark, renders theco^ jour more durable. Cotton having been foaked two hours in a di- luted ammoniate of copper, and then hung out to dry, appeared at firft of a fine blue colour, but afterwards became of a very beautiful bluifh green. A bit of this cotton being dyed for a few minutes in a decoction of Quercitron bark, be- came of a fine yellowifh green : another bit dyed in the fame decoction for a longer time became of a dark brownifh yellow colour $ this was, how- ever, H PERMANENT COLOURS, Sec. $*$ ever, changed to a lively yellowim green, by wafhing with foap, and fuffered but little dur- ing three weeks expofure to funfhine, air, and p rain. Linen or cotton foaked in a diluted nitrate of lead, then in lime water, and afterwards rinced and dyed with Quercitron bark, took a kind of nankeen brown colour fomewhat, though not very, durable. The other folutions of lead appear to be (till lefs ufeful as mordants upon cotton for dying with the bark. Manganefe being diffolved by a very weak or diluted fulphuric acid, and the folution after- wards mixed with an additional portion of water cotton was foaked therein for two hours, and afterwards immerfed in lime water, then rinced and dyed with the bark, from which it obtained a nutmeg brown colour inclining (lightly to the olive, which proved fomewhat lafting. The oxyd of arfenic is capable of ferving as a mordant for the Quercitron colouring matter but as the (hades produced by it may be ob- tained by cheaper and much lefs dangerous means, I cannot recommend its ufefor this pur- pofe. Cotton foaked in a diluted nitro muriate of gold, afterwards rinced and dyed with Querci- tron bark, received a delicate olive tinged yel- low of confiderable durability ; but this mordant is 356 PFIILOSOPHY OF is much too expenfive to be ufed in this or in almoft any other way. Cotton firfi dipped in a weak folution of foda, became of a yellowifh brown by being foaked in a diluted folution ofplatinaby the nitro- muriatic acid, and being afterwards dyed with the bark, it became of an olive colour. Cotton dipped in a weak folution of foda, and then in a diluted folution of the grey ore of Co- balt, (Cobaltum Galena.) in the muriatic acid, became firft green and then yellow ; and this being afterwards dyed with Quercitron bark, the colour changed to a lading black. The pure Cobalt, diffolved either by the muriatic or the nitric acids, and appiyed in this way to cotton, produced a cinnamon brown colour, with the Quercitron bark. Cotton wetted with a folution of foda, and then with a diluted nitrate of nickle, became green, and being afterwards dyed with the bark, it be- came of a full cinnamon brown. Irony though I mention it laft, feems to be the mod ufeful of the metallic bafes for dying on cotton and linen with the Quercitron bark, and more efpecially for producing the drab, mud, dove, and olive colours, with the great variety of fhades which refult from a mixture of thefe upon cotton velvets, velverets, fuftians, &c. Thefe co- lours have hitherto been commonly dyed from what is called the old fuftic, (morus tinfforia,) though they may be given more cheaply and conveniently with the Quercitron bark in the fame a PERMANENT COLOURS, &c. 3S7 fame ways, and when fo given, are more lading than thofe given by fuftic, as I have repeatedly found by expofing famples of each to rain, fun, and air, for the fpace of fix months together. The cheapeft form in which iron can be em- ployed in this way, is that wherein it is diffolved by fulphuric acid, as in the common fulphate of iron or green copperas ; and after many trials I have not found any other combinations of this me- tal capable of producing effects fo much better in dying as to compenfate for the increafed expence attending their ufe. Copperas and Quercitron bark, in different proportions, produce all the different fhades of the drab colour, from the deepeft to the lighted; and for this purpofe, the copperas may be either diffolved in a decodion of the bark, and the pieces of cotton velvet, vel- veret, or fuftian turned through the liquor (of a fuitable heat) by the winch, or the bark may be boiled with water in one veffel and the copperas diffolved by warm water in another, and the pieces paffed as ufual, firft through the latter and then through the former, and fo alternately from one to the other, until the proper fhade is acquired ; and by adding after the rate of one pound of chalk to eight pounds of copperas in the veffel wherein this laft is diffolved, the colour will be rendered more durable, and at the fame time changed a little to the chocolate brown. To produce the olive fhades, fulphate of cop- per (blue vitriol) with about one-eighth part of its weight of chalk, or alum with a like proportion of chalk, may be employed along with the cop- peras, 3 68 PHILOSOPHY Of* peras, To as to give the drab colour a fufiicient in- clination towards the yellow hue; and for this pur- pofethe blue vitriol is, I think, preferable to alum. For the drab colours^ one or two pounds of copperas, according to the fullnefs of colour 4 wanted, with about three times as much bark as of copperas, and a little chalk, will fuffice to dye ioolb. weight of velvet, velveret, or fuftian : and for the olives, it will only be neceffary to dimi- nish the quantity of Copperas according as the fhade is wanted to incline more or lefs to the yel- low, and add as much or a little more blue vi- triol in its ftead : and for this purpofe the blue vitriol may be either diffolved in the fame veffel with the copperas (and chalk,) or it may be dif- folved with chalk in a feparate (third) veffel, and the velvets or fuftians, after they have been turned or worked fufficiently, in the two firft vef- iels, containing, one the copperas liquor, and the other the bark liquor, may be turned or worked in the folution of blue vitriol in the third veffel, until it inclines fufficiently to xhe yellow hue; and perhaps this method will generally be found molt convenient to fuftian dyers, who are frequently required at the fame time to dye a great variety of different (hades. But other- wife it probably would be moll advantageous to turn and fb?.k the pieces for a little time in the folution of copperas and chalk, or of cop- peras, chalk, and blue vitriol, (or alum inftead of blue vitriol,) then immerfe them for a few minutes in lime water, and afterwards rince and dye them in a decoc~tion of bark, by which, co- lours much more lading and much lefs liable to fpot than thofe commonly obtained, might be dyed; it would, hosvever, be more difficult in this •.i::~.n: iifLt PERMANENT COLOURS, &c. 369 this way to produce that great variety of (hades, which in the other are eafily attained by any dyer accuftomed to the ufe of old fuftic for the like purpofes, as I well know by my own expe- riments and by thofe of other?. One pound of bark will commonly produce as much effect as four pounds of old fuftic* When darker colours are wanted, than can be conveniently given with the Quercitron bark and copperas, a portion of Spanilh fumach may be added to obtain them, as is done for fadefcning the colours given with old fuftic and copperas j though it is pofiible to produce a durable colour, approaching very nearly to a pcrfecl black, by the Quercitron bark and the iron bafis, by firfl: (baking the cotton in a weak folution of barilla and liver of fulphur, then drying and immerfing it in a diluted folution of iron, by the nitro mu- riatic acid> and afterwards dying it with the bark. Of the Application, of Quercitron Bark in Topical Dying or Callico Printing. Between the 170th and 179th pages of this volume, I have given a general though fum- mary account of the art of callico printing, as pra&ifed during many ages by the inhabitants of India; and alfo of the improvements which have followed the introduction of this art into Europe. I have alfo particularly defcribed the two principal mordants or bafes employed to fix and raife the different adjective colours, by topi- cal or partial dying; I mean the printers' alu^ minous mordant or acetite of alumine, and what is called iron liquor (acetite of iron), made by B b diffolving ■BBBSB 370 PHILOSOPHY OF diffblving that metal in vinegar, four beer, Sec. Thefe mordants the callico printers have very improperly named colour or colours, though they only afford the bafis or bafes of colour, to be afterwards obtained from madder, weld, Quer- citron bark, &c. For an account of the pre- paration of acetite or fugar of lead, and of the iubftitutes for it, in making the aluminous mor- dant, I cannot do better than refer my readers to Mr. Berthollet's chapter on that fubjecT, and to the writers therein mentioned ; and, for an account of the true nature and advantage of this aluminous mordant, my readers will be pleafed to recur to pages 176, 177, 178, 179 and 180 of this volume. Of the iron liquor, it may be proper to obferve, that, when made with vinegar, that which has been longed kept is moft ef- teemed. But of late much is confumed, which has been prepared by diffblving iron more expe- ditioufly in the pyro ligneous acid obtained by diftillation from wood and from tar; and it is probable that, in fome cafes, the action of this acid has been ftrengthened by an addition of the muriatic, though this laft muft have a ten- dency to render the folution corrofive. Linens or cottons, before they are printed, require to be bleached j and the more perfectly this operation is performed either by the old or new method, the lefs will the parts intended to remain white be afterwards ftained by the madder, weld, or bark liquors in dying; and the more eafily will any difcolouration from thefe liquors be afterwards difcharged. After bleaching, the pieces will need to be calendered, in order to produce a fmooth furface, and render 14 the* ■ "V:»riSji PERMANENT COLOURS, Sec. 371 the woof and fhoot as even and fquare as pofiible, and thereby favour a due application of the mordants; which, being firft properly thickened by (larch, flour, or gum, as formerly men- tioned, are to be applied by blocks, plates, cy- linders, &c. as thofe employed in this part of the bufinefs fufficiently underftand. This being done, the pieces are to be well dried in a ftove heat, fo as to evaporate the acetous acid, holding the bafis in a date of folution, and caufe the latter to be more copioufly depofited and fixed in the pores of the cloth. After drying, the cleanfing operation follows ; and this is performed in a ciftern with water, nearly as warm as the hand can well bear, and a quantity of frefh cow- dung; in which the pieces are to be brilkly worked, fo as to diflfolve the thick- ening of the mordant or mordants, and feparate all the unfixed fuperfluous particles of alumine or of iron, which the cow-dung ferves to en- tangle, fo as to hinder them from fpreading and attaching themfelves to the parts intended to be kept white, and there becoming the bafis of a future (lain or difcolouration, which it might be difficult to remove ; after this the pieces, being thoroughly foaked and well rinced in clean wa- ter, will be fitted for dying with the bark. In many cafes, madder colours are to be mixed in the fame piece with thofe of the bark ; but in thefe the madder ought to be firft dyed on a fe- parate courfe of work, in which the mordant or mordants are printed only fo far as the madder colours are intended to extend ; and the pieces being then dried, cleanfed, and dyed with the B b 2 madder, 3/2 PHILOSOPHY OF madder, and afterwards whitened by braning and bleaching, are to be calendered, and made ready to receive a fecond courfe of mordants for the bark, in which the pieces are to be printed, dried, cleanfed, &c. as juft mentioned. My readers have been already informed, that the bark produces a good bright yellow with the aluminous mordant, and a drab colour with the iron liquor ; and that both together mixed irt different proportions, produce different Ihade3 of olive and olive-brown colours. And that if a ftrong decoction of galls be added to the iron liquor, and the mixture applied in the fame way to linen or cotton, it will, by dying with the bark, produce a black fufficiently fixed, though inclining a little to a brownifh hue. By means, therefore, of the aluminous mordant and the iron liquor, three very diftinct colours befides the black are obtained from Quercitron bark : and moreover, by applying the aluminous mordant upon a madder red and an Indigo blue, an orange in the fir ft cafe, and a green in the fe- cond, will be produced when the piece come3 to be dyed with the bark. I have already noticed (at page 1 86) the practice of colouring the fotution of alum, in the Kaft Indies, with fampfan or fappan (red) wood ; a practice ( which the caliico printers of Europe have imitated, by colouring* the aluminous mor- dant with Brafil wood, (and thence calling it red colour,) not only when it is intended to ferve as a bafis for the madder red, but alfo for the Quercitron or weld yellows j though in the latter cafe at leaft, the practice ought to be laid afide. It ■^M^^^Hj PERMANENT COLOURS, &c. 373 It is indeed neceflary that fome tinge fhould be given to mordants in callico printing, in order that the printer may readily difcern the exact progrefs and extent of his work : but it is much better to give this tinge, from Quercitron bark, to figures or parts intended afterwards to receive the bark or the weld colours by dying, than to give it from Brafil wood ; the colour of which, were it to remain, would hurt the true yellow in- tended to be afterwards fixed upon the alumi- nous bafis : but the falfe Brafil colour, not having fo much affinity with the bafis as to be able to maintain its fituation, is always diflodged by the fuperior affinity of the bark or weld. This diflodg- ment, however, of one colouring matter by the application of another, takes up fome time, and unneceiTarily prolongs the dying procefs (the yellow in this cafe rifing more (lowly); and the parts intended to be kept white are alfo rendered liable to a greater degree of (lain or difcoloura- tion. But, where the mordant has been tinged with the Quercitron bark, a portion of the co- lour intended to be given is already applied to the bafis ; and, though at firft not perfectly fixed upon the linen or cotton, it foon becomes fo in the dying vefTel ; whilft the additional colouring matter of the bark, having no faife Brafil wood colour to diflodge, applies itfelf without impe- diment to the aluminous bafis, and produces the requifite degree of colour much more quickly, as may be eafily feen upon a proper trial. I do not indeed think that any degree of tinge ought to be thus given, even from the bark, beyond what is neceflfary to enable the workman to fee his work with fufficient clearnefsj becfaufe B b 3 the 374 PHILOSOPHY OF the particles of alumine or of iron, when pre- vioufly united to any fpecies of colouring matter, do not feem by cold application to fix them- felves either fo intimately or fo copioufly in the fibres of linen or cotton, as they do when ap- plied without any fuch union or incumbrance: and I have repeatedly found that yellow co- louring matter, dyed upon an aluminous bads untinged, produced a more lafting colour than it does upon a bafis previoufly tinged even by Quercitron bark, and much more lafting than where the tinge had been given with Brafil wood. And this fad will enable us to conceive one at leaft of the reafons why it is mod advantageous, in dying upon linen or cotton, to apply the aluminous bafis firft by itfelf alone. But, in topical dying with the Quercitron bark or with weld, wherever it is neceffary to give a moderate degree of tinge to the mordant, whether alu- minous or ferruginous, (i. e. iron liquor,) or a mixture of thefe, I muft ftrongly advife it to be given by a decoction of the bark made very ftrong, that it may not too much weaken the mordant, and at the fame time employed as fparingly as the nature of the cafe will permit. The effect of mordants topically applied, often depends greatly upon their being either too much or too little thickened with gum, ftarch, or flour, which are ufually employed for this purpofe. When the liquor has been too much thickened, it does not fufficiently penetrate the fibres or fubftance of the linen or cotton, and therefore the colour raifed upon it proves weaker and lefs durable than it otherwife would do: but on the contrary, if the liquor be not fufficiently thickened, it runs or fpreads too far upon the fur- face PERMANENT COLOURS, &c. 375 face of the piece, and produces figures or im- prefllons which prove confufed and undefined. In general the liquor for this kind of application fhould be made fo thick, and only fo thick, as barely to prevent its fpreading beyond the pro- per limits ; and it feems more necefiary to catch exactly this point of thicknefs or fluidity with the iron liquor than with the aluminous mor- dant, becaufe the oxyd of iron does not com- bine fo intimately as the alumine does with the acetous acid ; but, on the contrary, it remains fufpended in a lefs divided flate, and neither penetrates fo freely nor unites fo intimately as the particles of alumine with the linen or cotton to which it is applied ; and therefore the iron liquor in particular ought never to be thickened any more than is necefiary to hinder it from fpreading too far. When the mordant has been applied, and has had fufficient time to penetrate the fubftance of the cloth, it mould be thoroughly dried in air artificially heated as before mentioned, fo as to evaporate not only the water, but as much as pofilble of the acetous acid united to the alumine, or to the oxyd of iron, in order than nothing may remain to oppofe their intimate union with the fibres of the linen or cotton, which the water, and more efpecially the acid* necefiarily would do, by exerting their own par- ticular affinities upon the fubftances intended to be thus intimately united. It will however be impofiible in this way to evaporate the/ulpburic acid, of which the aluminous mordant, made with the ufual proportions of alum and iugar of lead, alway contains a little j and which, when the pieces B b 4 are 37<> PHILOSOPHY OF are brought under the cleaning operation, enables the warm water to re-difTolve and feparate a part of the alumine, wanted for raifing and fixing the colours intended to be afterwards given by dying; which alumine, being fo re T di(Tolved and feparated, is apt, even in fpite of the viicidiLy and entanglement of the cow-dung, to fix itfelf again upon thofe parts of the linen or cotton in- tended to remain white, and occauon a much greater and more lafting degree of (lain or dif- colouration than would otherwife take place in the dying veffcl. Thefe eftecls might indeed be obviated, by mixing a little lime or chalk with the cow-dung and water employed for the cleanfing, fo as to neutralize the fulphuric acid j but, by fo doing, a fulphate of lime woul ! be pro- duced ; and this, by fixing itfelf on the parts in- tended to be kept white, would give them a calcareous bafis, and occafion another kind of ftain or difcolouration as bad as that intended to be thus prevented. But carbonate of pot-afh or mild vegetable alkali, ufed in this way inftead of lime, will anfwer the purpofe of neutralizing the fulphuric acid, without communicating any improper bafis of colour, fo as to occafion that kind of ftain or difcolouration which it is fo de- firableto avoid ; though if any more of it be ufed than what is fufficient barely to neutralize the acid in queftion, it will exert a mifchievous ac- tion, by difiblving a portion of the aluminous bafis fixed upon the linen or cotton, and render the yellow afterwards communicated by dying more feebie than it otherwife would have been. A very little of the mild vegetable alkali may however be ufed in this way with advantage, fo as to leave the pieces capable of receiving full PERMANENT COLOURS, $cc. 377 full ftrong colours, vvhilft the parts intended to remain white will be but very {lightly difcoloured by the dying procefs, and afterwards eafily whitened. The mild vegetable alkali does not difTolve the oxyd of iron, and therefore may be ufed in this way with lefs caution to pieces printed only with the iron liquor. It is in all cafes of great importance, that the cleanfing operation mould be well conducted, and thoroughly performed 3 but more efpccially where a large proportion of drab, dove, and olive colours are to be inrermixed with yellows j becaufe the oxyd of iron, which ferves as a bafis to the former, is very apt to attach itfelf too copioufly to the linens or cottons on which the iron liquor is printed ; and unlefs the redundant part be carefully removed in the cleanfing ope- ration, (which is a work of fome difficulty,) it will remain, and be afterwards attracted and Separated by the colouring matter of the bark in the dying vefTelj and, uniting therewith, it will give the dying liquor an olive or drab colour tinge, and greatly tarnim the yellow figures or defigns, as well as ftain the parts intended to be kept white: and, therefore, whenever the iron liquor is to be printed upon the fame piece with the aluminous mordant, the former mould be diluted as much as it will bear, without making the liquor too weak to afford a fufficient bafis for the colour intended to be afterwards dyed upon it. By fuch dilution, joined to proper care in cleanfing, the yellows may be made to come out of the dying liquor perfectly untarnifhed ; which other- wife they will not do, at leaft when accompanied yikh any confiderable proportion of figures or defigns ssEnas^H 378 PHILOSOPHY OF defigns which have been printed with iron liquor. Having premifed thus much concerning the operations of printing and cleanfing, I now pro- ceed to that of dying with the Quercitron bark. For this, a fuitable portion of the bark, previ- oufly ground, is fir ft to be put into a dying pan or veftel with cold water, and the pieces to be dyed immediately after; a fmall fire is then to be lighted under the pan, fo as gradually to warm the water j and, while this is doing, the pieces are to be flowly turned by the winch, in order that the colouring mat- ter may apply itfelf equally : when the liquor becomes a little more than blood warm, the co- lours will take fufficiently quick, and prove more lading than they do when raifed more haftily; becaufe in a moderate warmth the co- louring particles (as was before obferved) have time, and are enabled to adjuft themfelves more accurately, and unite themfelves more clofely to the particles of alumine, than they can do when haftily thrown and accumulated by a greater heat upon the printed figures or defigns. And I have repeatedly found, that iamples flowly dyed with the bark in this way, being expofed to the fun and air along with others dyed more expeditioufiy in a boiling heat, proved much the moft lading. And if the Quercitron yellow has at any time been found leis durable than that of the weld, it can only have been fo through fome defect in the mode of dying, at lead if there was none in the mordant. Hitherto the bark has generally been ufed with too much beat at jirft. I fay at firft i becaufe after the colour • PERMANENT COLOURS, &c. 379 colour has been (lowly raifed, by liquor mode- rately warm, to nearly the proper height, a boiling heat will do no harm, excepting that of occafioning a little more ftain or difcolouration upon the parts intended to remain white; and though the avoiding of this is an additional motive for applying the bark in water of a moderate warmth only ; yet this of itfelf might not be a very powerful motive, becaufe fuch ftains from the bark are much more eafily removed than thofe refulting from weld. But the mod efTential dif- ference between thefe vegetables, refpects the de- gree of heat by which their feveral colours are moft permanently fixed upon linen or cotton ; that of weld requiring at leaft a fcalding if not a boiling heat to render it lading, whilft the bark colour, as has been already obferved, proves moft durable when applied in water but little more than blood warm. And indeed I have found, during the Summer months, that cottons printed with the aluminous mordant were able to imbibe a good, though not a very high yellow, by only remaining a few hours with bark in water of the heat of the open air, (in which it was placed,) and without any perceptible ftain or difcoloura- tion upon the parts not printed. A piece of the callico fo dyed in the heat of the atmofphere on- ly, being cut off and farther dyed with the bark in boiling water, it imbibed a greater body of colour j but a fample of this and of the former or paler yellow being equally expofed to the fun and air, I found at the end of three weeks, that the latter, which had been the deepeft, retained no more body than the other ; the additional co- louring matter, which in a boiling heat had been enabled to apply itfelf upon the aluminous bafis, having 380 PHILOSOPHY Of having been all difcharged during this expofure to the weather. A fact which feems to indicate, that when the alumine has attracted to itfclf a certain portion of colouring matter, any addi- tion made to it afterwards by the aid of heat, will be lefs permanently fixed, and therefore lia- ble to be more fpeedily removed by any of the caufes which ufually contribute to the decay of colours. All the different fhades of yellow may be ob- tained from the Quercitron bark by varying the quantity, and applying it with greater or lefter degpees of heat during a longer or fhorter time. By ufing the bark fparingly in water only blood warm, pale delicate yellows may be raifed in about fifteen or twenty minutes, and the parts intended to be kept white will receive fcarcely any difcolouration ; by a larger proportion of bark, and by keeping the pieces for a longer time in the dying liquor, though without increas- ing its "eat, a full and clear lively yellow may be produced j and by a ftill greater proportion of the bark, and a prolongation of the dying ope- ration in a fcalding heat during the latter part of it, the colour may be raifed firft to a high gojden, and afterwards to a very full brownifli yellow. The quantity, therefore, of bark to be employed muft always depend upon the nature and clofe- nefs of the figures or impreffions which are to be dyed, and the height or fullnefs of colours in- tended to be produced. Commonly, however, one or two pounds of bark will fuftice for each piece ; but, where too little has been employed at firft, a farther quantity may be afterwards add- ed without inconvenience j and, when the dying is PERMANENT COLOURS, &c, 381 is to be performed in a very moderate heat, it will always be moil advantageous to employ a little more bark than is neceffary ; which may be done without any lofs of colouring matter, becaufe other pieces may be afterwards dyed, with a farther fupply of bark, in the fame li- quor; and I have found that yellows, whether dyed from bark or weld, commonly prove mod durable when the dying liquor has been fome- what plentifully ftored with colouring matter ; and in general I think it bed to employ the bark fo freely, as that the liquor may be ftrong enough without being made more than blood warm, to produce full bright yellows in the fpace of half or three quarters of an hour ; the tinge or difcolou- ration which the parts not printed imbibe from the bark in this way not being half fo great as that produced by weld, and it being afterwards difcharged with lefs than half the time and trou- ble which even an equal degree of (lain from the latter would require. Indeed, where the pieces have been at lirft well cleanfed from all loofdy adhering and fuperfluous particles of the alumi- nous or ferruginous bafes, thedifcolouration from bark generally proves fo inconfiderable, that by rincing or warning them in cold, and more es- pecially in warm water, it may be fufficiently re- moved without either braning or bleaching, ex- cepting where the unprinted parts arc required to be uncommonly clear and white : and when this is the cafe, I think it bed to add after the rate of one pound of cream of tartar, in powder, for every twelve or fourteen pounds of bark, put- ting the tartar into the water immediately after the bark, and then dying the pieces, as I have already explained. The tartar ufed in this way 1 will 1^"" wmw 182 PHILOSOPHY OF will contribute much towards keeping the white or unprinted parts free from (lain or difcoloura- tion ; and it will, moreover, give the Querci- tron yellow that bright, clean, and delicately greenifh hue which is fought for in the weld, fo as to make the former refemble the latter. But, as the tartar tends to keep the Quercitron yellow from taking fo fall or rifmg fo high as it would otherwife do, the liquor may, in this cafe, be made hotter in the latter part of the operation. On the contrary, if, inftead of tartar, one pound of clean white pot-afh be added for every thirty pounds of bark, a very high, and at the fame time a very bright yellow will take fo quickly, that the liquor mould never be more than blood warm : and, though the unprinted parts may feem a little more ftained than they are when no pot-afh is ufed, the ftain will be dis- charged by thoroughly rincing and warning the pieces as ufual. Some callico printers, not acquainted with the beft methods of employing the bark, have thought proper to join with it a little of the decoction of weld : I cannot, however, recommend this prac- tice, becaufe in truth the bark, when properly ufed, wants no fuch afiiftance, and becaufe the colouring matter of the weld does not take per- manently without a greater degree of heat than ought to be employed with the bark. It more- over occafions a much greater ftain upon the un- printed parts, and at the fame time degrades the madder reds and purples, (where thefe colours have been previoufly dyed,) much more than the bark. It PERMANENT COLOURS, kc. 383 It is to be obferved, that the very moderate warmth, which bed fuits this kind of dying with the bark, does not, in general, completely ex- tract its colouring matter, at lead from fuch parts thereof as are not finely ground j but, being tied up in a bag, it may be afterwards boiled feparately in water, and the decoclion fo made may be employed for dying olive and drab co- lours, where they are not intermixed with yel- lows, or reds. Some callico printers have, in- deed, thought it beft, in all cafes, to begin by boiling the bark in a fmall quantity of water, fo as fully to extract the colouring matter, and then, for yellow as well as drab and other bark colours, to put a fuitable proportion of the de- coclion into the dying vefTel, with clean warm water, and dye the pieces therein, adding more of the decoction as wanted from time to time. I do not, however, think this practice (o conve- nient as what I have recommended. A very ingenious printer in a diftant country and warm climate, fome time fince favoured me with an account of his method of ufing the bark, which he confiders as one of the belt : " I pound (fays he) the bark, and boil it in a good quan- tity of water, fay twenty- five gallons to (even pounds of bark ; after which I let it fettle, and pour off" the clean decoction j of which I add a portion to a tub full of clean cold water, and im- mediately, with the hand, pafs a quantity of clean rinced (printed) cloths through the water j they tafke on colour very quickly, and it appears frefh and beautiful : I then add another portion of the decoction, and bring out a pretty full yel- low i meanwhile I have my large copper ready with $8 4 PHILOSOPHY OF with clean water as warm as the hand can well bear, and to this I add alfo a portion of the de- coction ; and then remove the cloths from the tub into the copper, and torn them quickly round 5 by which method I obtain the bell and moft du- rable yellows: ten or fifteen minutes will belong, enough to keep the cloths in warm water, where a delicate yellow is required." "I found it eafy," continues the writer, -->>>>-- H 404 PHILOSOPHY OF metal a yellow; but neither of thefe are tailing upon linen or cotton. The nitro-muriate of antimony produces with the bark, a kind of fnuff colour of fome dura- bility on linen and cotton ; and different (hades of brown were produced in this way by the nitrate and the muriate of cobalt with the bark, which however foon faded by expofure to furi and air. In giving this account of the properties and ufes of Quercitron bark, I have had before me notes of feveral thoufands of experiments made there- with, in almoft all poffible ways, and with almoft all poffible chymical agents. But as a detail of their effects would more than exhauft the patience of any reader, I fhall content my- felf with dating as I have here done, the refults of thofe which feem molt likely to prove ufe- fulj and probably what I have already flated is more than enough on this fubjecl:. I have; however thought it incumbent on me to omit nothirig in any degree likely to afford ufeful information respecting a new dying drug, firft brought into ufe by my exertions, and which without them would probably have remained unknown as a dying drug for ages to come: — a drug which has already produced im- portant benefits, efpecially to the art of cal- lico-printing in Great Britain ; and is likely hereafter to benefit other European nations, as well as the United States of America, in an eminent degree. The confumption has indeed hitherto been fmall, compared to the probable future increafej but it has been large confidering PERMANENT COLOURS, &c. 40; confidering the fhort time fince its properties were firit made known, and the immenfe diffi- culties which attend the introduction of all new dying drugs : it appearing by the aft of the 13th and 14th of Charles II. ch. 2., that nearly one hundred years had elapfed before " the ino-eni- M ous induftry of modern times had taught the " dyers of England the art of fixing the colours for befides the cmiflion of parts which appeared to me of lefs importance, I have frequently changed his modes of ex- preffion for the fake of perfpicuity and brevity. " I have feen," fays Dr. Roxburgh, "afhort " r TWMH 432 APPENDIX. feme of which remain on the furface, and gradually collect into patches of froth ; a thin violet, or copper coloured pellicle or cream makes its appearance between the patches of froth, and foon after, the thin film which forms the covering of the bubbles compofing the froth, begins to be deeply tinged with a fine blue : The liquor from the beginning will have been acquiring a green colour, and now it will appear, when viewed falling from one vefiel into ano- ther, of a bright yellowiili green, and will readily pafs the clofeft filter, until the action of the air makes it turbid, a proof that the (bafe of the) colour is now perfectly diflblved in the watry menftruum. This is the time for letting off the vat j if fuffered to remain, the bulk be- gins to diminifh, and will return to its original dimenfions; the fermentation however conti- nues j there is dill much inteftine motion through the vat ; large quantities of froth are formed j hitherto the peculiar fmell of the plant will have prevailed, but now it becomes very oiTenfive, fomewhat refembling animal matter beginning to putrefy i as the fermenta- tion goes on, the fmell becomes more and more ofTenlive, and the quantity of air difcharged is lefs and Ids, till an abforption takes place." When in the early part of the procefs 1 held a glafs tube to the mouth of a fixty gallon cafk, which ferved as a fermenting or fteeping var> that I might collect the airs, if any had been difcharged, I found the wet bladder which had been tied over the upper end of the tube " ftrongly preffed in by the external air, a fure proof that the vat in this ftate abforbed air; but as foon as the bulk of the mafs begins to foe APPENDIX. 433 be enlarged, a difengagement of airs takes place, and thefe are the fixed, pure, and impure: about the time when the bulk, of the vat or li- quor has attained its greateft increafe, the fixed air is difcharged in greater purity and in larger quantity than at any more early period ; and it even continues to predominate until the 9th day, which I call the laft flage. When the fer- mentation had advanced beyond the ftage at which the vat ought to be drawn off, I found that a little agitation was neceflary .to promote a difcharge of airs fufficient to fill a bladder." I could detect no volatile alkali in any part of the procefs : " During the agitating procefs, fixed air continues to be difcharged, and in im- menfe quantities, mixed with pure and impure airs; but ftill nothing like volatile alkali ap- pears." As foon as the grain fhews itfelf dif- tinctly, the precipitant (alkaline or calcareous) is to be added; from that inftant, an abforp- tion of air takes place, and after the liquor has fettled a little, a candle will burn freely clofe to its furface, as long as it would have done in the fame quantity of atmofpheric air ; though, be- fore, it had been conftantly extinguished at the mo- ment of its entering the mouth of the veffel. With nerium leaves the fermentation never be- came fo perfect as with the common indigo plant ; yet the airs difcharged from it were the fame, though lefs in quantity. " By fcalding either the common indigo plant (i. e. young twigs and leaves) or the leaves (only) of nerium in bottles containing four gallons, nearly the fame efTedts were produced, viz. firft, an ab- forption of air, then an increafe in the bulk of the mafs, with a difcharge of pure air at firft, F f and HI 434 APPENDIX. and afterwards of pure air mixed with fixed air, though in a proportion fmaller than in the fer- menting mixtures; here alfo during the agita- tion immenfe quantities of fixed air are difcharged till the grain is formed and the precipitant added, when, as in the other cafe, an abforption takes place. Here alfo a lighted candle burnt freely near the furface of the liquor, after the precipi- tant was added, and once I obferved diftin&ly fome explofions of inflammable air. But the liquor being agitated, and a candle immediately' after let down into the velTel (bottle), it was inftantly extinguifhed upon entering its mouth/' I took fome of the green coloured liquor, be- fore it had furTered any agitation, and with it filled the globe of Dr. Nooth's apparatus for impregnating water with fixed air, into which (liquor) I continued throwing that fluid (fixed air) from a mixture of powdered lime-ftone, and diluted vitriolic acid for fome hours, but no change took place. After {landing till next morning, a very few grains of a greenifh precipi- tate were found in the bottom of the velTel, which I impute to the communication which the liquor had had with the open air before it was put into the globe; for when the leaves had been fcalded in bottles of water, inverted in a large veiTel of water, or in the globe itfelf, and committed to the, fame trial, no grain was found; the liquor continuing uniformly of a pale yel- lowifh green, which is the colour it always, in my experiments, acquired when fcalded in the above manner. I kept fome full bottles of it inverted in water for a month, and no change Took place j nor does the liquor in thefe circum- flances APPENDIX. 43 5 ftances ever acquire the copper-coloured film on the furface, but as foon as the air is admitted to it, greenifh blue veins are obferved to defcend from the furface, in various directions, until the whole becomes blue. This phcenomenon is conftant, but the colour is more or lefs deep according to circumftances : foon after a preci- pitation of blue grains takes place, and the cop- per-coloured pellicle appears on the furface j but no change appears in the colour of the liquor, nor is any grain formed while the external air is perfectly excluded ; neither do the leaves ac- quire that ofYenfive fmell which they do when expofed to the action of the air. " I may there- " fore, I think, fafely conclude, that fixed air is 5 THfc GETTY CENTER LIBRARY r * \ ?i"JH r 1 \&xW, •" «j«g ^jj BANCROFT PHILOSOPHY OF COLOURS H .".V : ": mm mmm ;i : ; -:^k":">:->:-:->: <:>^S^: ggggg^ ---. mmz?m