Chemical Manufactures. 115 



hundred miles of calico, the solution required for the purpose 

 containing less than a grain of the salt to the gallon. Aniline 

 may be obtained also from naphthaline ; and thus a substance 

 which was so long not only worthless but a cause of consider- 

 able inconvenience, may be made the source of a most valuable 

 material. The method of obtaining it from benzole was dis- 

 covered by Bechamp in 1856. Its most characteristic pro- 

 perty is the blue colour which it strikes with the solution of 

 bleaching powder, or of any alkaline hypochlorite ; and this 

 suggested its use as a means of producing colouring materials. 

 It forms crystallizable salts analogous to those of the metals. 



The aniline colouring matters are generally obtained from 

 its sulphate, which is formed by the addition of dilute sulphuric 

 acid, and, with gentle evaporation, separates as a salt. The 

 sulphate of aniline having been dissolved in boiling alcohol, it 

 crystallizes in colourless plates, which become red by exposure 

 to the air. Mauve dye, or aniline violet, is obtained by preci- 

 pitating the sulphate with bichromate of potash, and digesting 

 the precipitate with coal-tar naphtha ; then dissolving out the 

 colouring matter with alcohol, and removing the alcohol by 

 distillation. Cotton does not take the aniline colours as well 

 as wool or silk ; they may, however, be found to answer better 

 with Indian cotton, which from some cause, yet unknown, is 

 more easily dyed than that from other localities. Among the 

 derivatives of aniline is Rosaniline, which is quite white until 

 some acid is added. Its acetate, dissolved in water, constitutes 

 the magenta dye. Some very splendid and valuable specimens 

 of crystallized acetate of rosaniline, in the form of crowns, are 

 shown at the Exhibition. There is also an aniline yellow, and 

 an aniline blue ; but, in general, the shades derived from ani- 

 line are those varying from pink to purple. No other dyeing 

 material produces more beautiful or more permanent colours. 



The present Exhibition affords abundant proofs of the per- 

 fection to which the dyer has brought his art, with the assist- 

 ance of the chemist. That such valuable and beautiful com- 

 pounds as the aniline dyes should be produced from so mean a 

 substance as coal-tar, presents the most incontestable evidence 

 of the aid which chemistry may furnish to the arts — an aid the 

 more to be prized when, as in this instance, it consists in uti- 

 lizing materials which may be obtained in abundance, and 

 which are otherwise of but little value. 



