126 MODERN SCIENCE READER 



One of the first achievements of the nineteenth century, 

 in the field of chemical technology, was the production of 

 illuminating gas from coal. The dry distillation of 

 bituminous coal yielded, in addition to gas, various tarry 

 matters which were collectively named gas tar, or coal tar. 

 This at first was a perfectly useless and annoying waste 

 product. 



In 1834 Runge obtained from coal tar, by distillation, a 

 liquid of basic properties which he called cyanol. Before 

 this, in 1826, Unverdorben had obtained by the dry distil- 

 lation of indigo a basic liquid which he called crystalliri, 

 because it formed, w T ith acids, crystallizable salts, and 

 about the same time Zinin had obtained a basic liquid, 

 which he called benzidam, by treating nitrobenzol with 

 ammonium sulphate. Hofmann proved the identity of 

 these three liquids. The substance is now called aniline, 

 from anil, the Arabic name of indigo, and from it many of 

 the coal-tar colors have been derived. The discoveries of 

 Hofmann and Zinin made it possible to obtain aniline in 

 large quantities. Coal tar contains aniline, but too little 

 to pay for extracting. On the other hand, coal tar contains 

 a large amount of benzol, which can easily be separated. 

 By treatment with nitric acid, benzol can be converted into 

 nitrobenzol, and from this aniline can be obtained by 

 Zinin 's process. 



In 1856 William Henry Perkin, who was attending Hof- 

 mann 's lectures at the Royal College of Chemistry in 

 London, attempted to produce quinine by oxidizing aniline 

 with potassium bichromate, and obtained a black precipi- 

 tate. Others had done the same and gone no further, but 

 Perkin found that the precipitate dissolved in alcohol, 

 forming a violet solution, with which silk could be dyed. 

 In the following year he started a factory for the 

 production of the new dye, which was first called * ' Tyrian 

 purple," and subsequently became known as mauve, aniline 

 violet, or Perkin 's violet. Aniline red, or fuchsine, was 

 discovered also in 1856, by Nathanson, but its commercial 



