ANILINE-YELLOW 187 



5. Oxidation of a salt of aniline by the peroxide of lead under the influence of an 

 acid. Price. 



6. Oxidation of a salt of aniline by free chlorine or free hypochlorous acid. Smith. 



7. Oxidation of a salt of aniline by the double chloride of copper and sodium. 

 Dale and Caro. 



The only processes which are employed industrially are those in which bichromate 

 of potash, chloride of lime, and chloride of copper are used. The dyeing of silk or 

 wool by means of aniline-violet is a process of the easiest description. 



Dyeing Silk. An alcoholic solution of the violet purple is diluted with eight times 

 its volume of hot water previously acidulated with tartaric acid. This liquid is 

 poured into the dyeing-bath of cold water slightly acidulated. Through this the silk 

 is passed until the required shade is attained. The tint is rendered bluish by means 

 of indigo-carmine. Sulphuric acid added to the dye-bath causes the violet to assume 

 a greyish shade. This may be increased until a very beautiful grey (gris perle) is 

 obtained. This colour is much used by the silk-dyers of Lyons. 



Dyeing Wool. This is conducted at a temperature of 50 or 60 C., the dye-bath 

 consisting simply of a dilute aqueous solution of colouring-matter, without any acid. 



Printing upon Silk and Wool. The paste of aniline-violet is dissolved in about five 

 times its weight of acetic acid (specific gravity, 1'060), and mixed with enough gum- 

 water to form a printing material. The fabrics when printed are submitted to the 

 action of steam, and then washed. 



Dyeing Cotton Since cotton does not, like silk or wool, present much attraction for 

 the aniline colours, the dyer employs albumen, soluble gluten, or tannin. In some 

 eases the oxides of tin, of aluminium, of lead, or of antimony are used. Sulphuric 

 acid has also the property of fixing the aniline-violet on cotton. The animal or tannin 

 mordants are printed on the cotton, which is steamed so as to fix it, and it is then dyed 

 in an acidulated solution of the colour. 



Vwlet Imperial. This violet, which is essentially different from the mauve, is 

 formed by modifications of the aniline reds and blues. It is produced thus : Equal 

 quantities of aniline and dry hydrochlorate of rosaniline are heated to a temperature 

 of 180 C. for about four hours. MM. Girard and De Laire first patented this colour, 

 and on account of its great beauty it is much used, although not quite so permanent as 

 the mauve. Mr. E. C. Nicholson forms another violet by heating aniline-red in a 

 suitable apparatus to a temperature between 200 and 215 C. This mass is exhausted 

 with acetic acid, and the deep-violet solution diluted with enough alcohol to give to the 

 dye a convenient strength. 



Aniline-violet resists the action of light to a very considerable extent, although 

 Chevreul has- shown that it is inferior in this respect to either madder, cochineal, or 

 indigo. 



-aNTLINE-YEIiIiOW. In the preparation of aniline-red there arises a great 

 number of secondary products. Amongst others, a yellow colouring-matter has been 

 separated by Mr. Nicholson and examined by Dr. Hofmann. The name of Chrysaniline 

 has been given to this very beautiful yellow colour, which has been proved to be a 

 well-defined base. The preparation of chrysaniline is simple. The residue from which 

 the rosaniline has been extracted is submitted for some time to a current of steam, 

 when a quantity of the base passes into solution. Addition of nitric acid to this solu- 

 tion precipitates the chrysaniline in the form of a difficultly soluble nitrate. 



Hofmann has shown that chrysaniline is intimately related to rosaniline and 

 leucaniline, only differing from the first by two equivalents, and from the second by 

 four equivalents of hydrogen : 



Chrysaniline CHN. 

 Kosaniline C 20 H 18 N S . 

 Leucaniline C 2 H 21 N S . 



Chrysaniline forms two series of salts, the greater number of which are well crys- 

 tallised. The most remarkable salt of chrysaniline is the nitrate, which is so insoluble 

 in water that nitric acid may be precipitated, even from a dilute aqueous solution, by 

 means of the more soluble hydrochlorate or acetate of chrysaniline. These, when 

 poured into a nitric solution, rapidly give rise to the formation of an orange-red 

 chrysaniline precipitate of nitrate of chrysaniline. This chrysaniline and its salts dye 

 silks and wools a splendid golden-yellow colour. Such is the general character of the 

 aniline colours. They have been used as printing-inks, which are very permanent. 

 See ' Watts's Dictionary of Chemistry.' 



E. Waller, E.M., in the ' American Chemist,' gives the following list of the names of 

 the various coal-tar colours, both commercial and chemical, together with their 

 chemical formulae, when those could be found. (It should be observed that the old 

 notation has been employed throughout). 'Many of the compounds hero men- 



