RESEARCH AND THE COAL-TAR DYE INDUSTRY 249 



an investigation on anthracene at the Royal College of Chemistry 

 without, however, achieving any definite results. 



Alizarine itself (from alizari, the Levant name for madder) 

 had been obtained from madder-roots by Colin and Robiquet 

 in 1827 by sublimation, and was also separated later by Dr. 

 Schunck by extraction. Madder is, next to indigo, one of 

 the oldest known dyes and is chiefly used for dyeing the fast 

 scarlet shade known as " Turkey red." 



The madder industry was one of very large dimensions, 

 some idea of which may be gathered from the fact that in 

 France (the chief producer of the natural dye) 20,466 hectares 

 were planted with madder in 1862 ; the dye was chiefly 

 exported in two forms, either as crude madder-root, or as 

 the partially purified dye-stuff known as garancine. Great 

 Britain was the chief importer of the dye, the average annual 

 imports from various sources for the period 1 859-1 868 being 

 305,850 cwt. of madder, worth 45s. to 50s. per cwt., and 

 45,560 cwt. of garancine at 150s. per cwt., the total annual 

 imports averaging about £1,000,000. In 1868 the world's 

 production of madder was estimated at about 70,000 metric 

 tons and worth £3,000,000 to £3,500,000. 



Having regard to the magnitude of the industry, it is hardly 

 surprising that great efforts were made to synthesise the dye 

 from coal-tar. For a long time, owing to a wrong formula 

 having been given to alizarine, it was regarded as a derivative 

 of naphthalene, and Perkin himself undertook research with 

 a view to obtaining the dye from this source, but, of course, 

 without success ; alizarine was believed to have the formula 

 C 10 H 6 O 3 , so that it was assumed to be related to the body 

 known as " chloro-oxynaphthalic acid," Ci H 5 ClO 3 and Martius 

 and Griess, by replacing the chlorine atom by hydrogen, 

 obtained a substance Ci H 6 O 3 which was not identical with 

 alizarine and was assumed to be an isomer. 



Graebe and Liebermann, however, showed that by distilling 

 alizarine with zinc-dust the hydrocarbon anthracene was 

 obtained, and the formulae were therefore given : 



C 14 H 10 CuHgO, C u H 6 2 (OH) 3 



Anthracene. Anthraquinone. Alizarine. 



They further showed that the dye-stuff could be obtained con- 

 versely by oxidising anthracene to anthraquinone, treating the 



