

DYEING. 



Organic 

 structure 

 mill on:i po- 

 sition of 



' .1:!*. 



IMKcTences 

 ,.,: MM 

 fluffs of 

 M.i ual and 

 vegetable 

 origin. 



Animal 

 matters 

 more liable 

 than vege- 

 fa U IT 

 sSectnl by 

 ilici . 

 - 



or archil alone have been employed, the colours arc 

 made rod by the action of a vegetable acid, but if the 

 solution of tin has been used to dye with these substances, 

 the colour which has been prepared in an acid liquor, 

 is not afterwards affected by vegetable aei.U. and in that 

 case a colour may be reckoned good, which has been 

 nun h less i \pcn-i\e, and will prove less durable. So 

 that for silk also the only test we can rely upon with 

 confidence is exposure to the air and light. 



SECTION III. 



Or STUFFS. 

 CHAP. I. Of the Nature of Stuffs in general. 



180. Though a knowledge of the structure of orga- 

 nized bodies, and of the prapotiow in which their ul- 

 timate principles are combined togeth-r, can seldom, 

 without the aid of experiment, afford much informa- 

 tion respecting their relations with other substances. \\c 

 cannot doubt that an intimate acquaintance with their 

 mechanical form anil chemical compositon will throw 

 some light on these relations, and point out the best 

 means of investigating such as cannot be discovered by 

 analogy alone. We shall therefore endeavour to ascer- 

 tain the mechanical and chemical constitution of the 

 various kinds of stuffs, as a knowledge of these may 

 assist us in discovering the circumstances upon which 

 their attractions for colouring matters depend. 



181. The stuffs usually submitted to the operation of 

 dyeing, are wool, silk, cotton, and flax. The two first 

 are of animal origin; the two last are vegetable pro- 

 ducts. These substances disagree with one another in 

 chemical composition, and are characterised by those 

 differences of constitution which usually distinguish the 

 productions of the animal and vegetable kingdom. 

 Animal substances differ from vegetable products, by 

 containing a considerable quantity of nitrogen, all ele- 

 ment which exists but sparingly in vegetables ; and 

 also a larger proportion of hydrogen. This difference 

 of chemical constitution is rendered very obvious, when 

 animal and vegetable products are subjected to distilla- 

 tion. The former yield a large quantity of ammonia, 

 the latter seldom give out that substance, but frequent- 

 ly an acid. The former yield much oil, while, in many 

 cases, vegetable products do not yield the smallest quan- 

 tity. Hence, animal substances, during their combus- 

 tion, afford a bright flame, though of short continuance, 

 s it is soon extinguished by the charcoal which is 

 formed ; they, at the same time, emit a very pungent 

 odour, owing to the extrication of ammonia, and of the 

 empyreumatic oil, which makes its escape without being 

 consumed. Animal substances are very liable to putre- 

 faction, and during the advancement of the process, 

 evolve much ammonia ; while vegetable products suffer 

 more slowly the vinous or acetous fermentation. 



182. As substances are most readily decomposed 

 when the elements which enter into their composition 

 are numerous, animal matters are more liable than ve- 

 getables to be destroyed by the different agents to which 

 they are exposed. The number of elementary princi- 

 ples which they contain, enlarges in an equal degree the 

 sphere of their chemical affinity ; and hence they are 

 also more disposed to combine with colouring matters. 

 Thus the pure alkalies quickly destroy animal substan- 

 ces, because they combine with them, and lose their 

 causticity, while they have little or no effect on vege- 

 table!. The nitric and sulphuric acids also act with 



con-iderahle energy on animal substances ; the former Of Studi 

 decomjxises them, extricates tile nitrogen, separates the ~V~ ' 

 fatty matter, and forms carbonic and oxalic acid ; tin- 

 latter extricates the hydrogen, a small portion of nitro- 

 gen, and leaves a carbonaceous residuum. 



Silk, though an animnl product, partakes a good 

 deal of a vegetable nature. It is K-s disposed to com- 

 bine with colouring matters than wool, and re^iM" bet- 

 ter tile action of acids and alkalies. Cotton and flax 

 withstand the action of acids and alkalies more power- 

 fully than wiM.l and silk, the former being dr.-troycd 

 with difficulty even by the nitric acid. T lit -< diffe- 

 rences are chiefly owing to differences in chemical con- 

 stitution ; but they may be partly ascribed to diii'errn- 

 ccs in the conformation of their fibres, and organic 

 structure. 



CHAP. II. Of Wool 



181. The different kinds of vool vary chiefly in the funeral 

 length and delicacy of the fibre. Its qualities depend propertie*. 

 partly upon the breed of the sheep from which the 

 wool is taken, and partly upon the parts of the animal 

 to which it adhered. The finest wool is brought from 

 Spain ; though Berthollet affirms, on the authority of 

 D'Aubenton, that it might be produced in France'of a 

 quality equally good, by a little attention on the part 

 of the shepherd. Attempts have l>een made of late to 

 introduce the Spanish breed of sheep into this country, 

 with the view of rendering us independent of a supply 

 of wool from abroad ; but it is probable that change of 

 climate may affect the habits of the animal, and produce 

 alterations on the fleece. It is well known that the na- 

 ture of the pasture has a considerable effect on the qua- 

 lity of wool. The manufacturer should be able to judge 

 with accuracy respecting the fineness of it ; and, a 

 simple inspection is insufficient for the purpose, the 

 fibres should be closely examined with a microscope, 

 and compared with those of other wools, selected as 

 standards. v. 



185. In the raw state, wool is covered by a sort of y ik. 

 unctuous matter called yolk, or suinl, which preserves 



it from the attacks of moths, and, on that account, 

 ought not to be prematurely removed. This substance 

 has been examined by Vauquelin, and appears to be a 

 kind of animal soap, having potash for its basis, together 

 with a quantity of fatty matter, >id a portion of lime 

 in combination with the carbonic, acetic, and muriatic 

 acids. The wool of healthy sheep is always more abun- 

 dantly covered with yolk than that of the sickly and 

 diseased. 



1 86. Before wool is submitted to the operation of MC ,I IO( I, o{ 

 dyeing, the yolk is removed by scouring or maceration removing 

 for about a quarter of an hour in water, mixed with a the yolk. 

 fourth part of stale urine, and heated so as the hand 



can just bear the temperature. After being duly stir- 

 red in this mixture, it is taken out and drained ; it is 

 then carried to a stream of running water, and moved 

 about till the greasy matter appears to be completely 

 separated, and ceases to render the water turbid. M. 

 Vauquelin recommends, that the wool, after being 

 cleansed as effectually as possible v ith pure water, 

 should be soaked for a few hours in a tepid solution of 

 soap, one pound of soap l>eing employed for every 

 twenty pounds of wool to be scoured. M. Hoard is of 

 opinion that one pound of Flanders soap, employed in 

 thi- manner, is sufficient for thirty pounds of wool ; he 

 recommends, however, that the water should be heated 

 to 60 of Keaumur, (lC7 of Fahrenheit) He affirms 



