Among the several stages which mark the development of the industry of coal-tar colours, the discovery of the transformation of aniliue-red into aniline-blue will always hold a prominent position. This transition, for the first time observed by MM. Girard and De Laire, two young French chemists of M. Pelouze’s Laboratory, and subsequently matured by M. Persoz, De Laynes, and Salvetat, has become the foundation of an enormous industrial production, which, having received a powerful impulse by MM. Renard Brothers and Franc in France, and more recently by Messrs. Simpson, Maule, and Nicholson in this country, has rapidly attained to proportions of colossal magnitude. The transformation of aniline-red into aniline-blue is accomplished by a process of great simplicity, and consists, briefly expressed, in the treatment at a high temperature of rosaniline with an excess of aniline. The mode of this treatment is by no means indifferent. Rosaniline itself cannot in this manner conveniently be converted into the blue colouring matter; the transformation is, however, easily accomplished by heating rosaniline salts with aniline, or,
vice versâ
, rosaniline with salts of aniline. Again, the nature of the acids with which the bases are combined is by no means without influence upon the result of the operation; manufacturers give a decided preference to organic acids, such as acetic or benzoic acids.
Industrial Production of Antibiotics and Organic Acids