The Romance of Modern Chemistry

VALUABLE SUBSTANCES demand soon arose for this, the first artificial dye, and Perkin, with the assistance of his father and brother, started a small factory for its production at Greenford, near London. The importance of Perkin’s discovery in relation to the utilisation of tar lies in this, that although aniline, the raw material for the manufacture of mauve and other dyes, occurs only in traces in coal tar, it is very easily produced from benzene, which, as we have seen, is one of the regular constituents. For this purpose benzene is first treated with nitric acid, which converts it into nitro-benzene—a substance which in smell closely resembles oil of bitter almonds, and which is used in scenting soaps. Nitro-benzene, when treated with iron filings and hydro- chloric acid, is converted into aniline. This liquid is a basic substance, which contains the elements carbon, hydrogen, and nitrogen, and unites readily with acids to form salts. Perkin’s discovery, therefore, that aniline was the parent substance of artificial colouring matters meant that there was a new outlet for the benzene from coal tar. Mauve was only the first of a long series of artificial dyes which chemists have succeeded in building up out of the constituents of coal tar. Some of these, such as alizarin and indigo, have competed successfully with the naturally occurring dye, while others, so far as we know, do not occur in Nature at all, but are of purely laboratory origin, such as magenta and Bismarck brown. The phenomenal growth of the artificial colour industry can best be realised by contrasting the modest works at Greenford, where Perkin began the manufacture of mauve, with the extensive dye-works of Germany at the present time. The manufacture of artificial colouring 286