1870.] A Recent Triumph of Synthetical Chemistry. 301 



prisms, and when exposed to carefully-regulated heat, suhlimes, con- 

 densing into beautiful tufts of scarlet needles ; it is only sparingly 

 soluble in water, but dissolves in spirit, and in alkaline solutions ; 

 its tinctorial power is at least thirty-five times as great as that of 

 madder itself. Dr. Schunck was the first to point out that Turkey 

 red, madder pink, and all the finer madder colours, are simply com- 

 pounds of alizarine and fatty acids with bases, and he has described 

 a process for preparing pure alizarine from cotton which has been 

 dyed Turkey red. 



The discovery of the method of preparing alizarine artificially 

 is due to two continental chemists, Messrs. Graebe and Liebermann, 

 and their discovery is the more remarkable, since it has not been 

 effected by any haphazard, rule-of-thumb system of experimentation, 

 but is the result of a scientific investigation on the properties and 

 molecular structure of alizarine, and has been conducted, step by 

 step, in accordance with logical deductions from the known laws of 

 synthetical chemistry. The train of reasoning is too complicated, 

 and requires too profound a knowledge of the laws of modern 

 chemistry, to be given in detail here, but a brief outline of their 

 research will perhaps be of interest. 



From an examination of the substances obtained when pure 

 alizarine from madder was submitted to sundry chemical processes, 

 it was ascertained that this principle was connected with the hydro- 

 carbon group containing fourteen atoms of carbon, and by heating it 

 with a body capable of removing oxygen, they obtained from it the 

 hydro-carbon of the group, containing fourteen atoms of carbon and 

 ten of hydrogen. This was seen to be identical with one of the solid 

 crystalline bodies obtained in the distillation of coal, named anthra- 

 cene ; and by a somewhat complicated process they converted this 

 into anthraquinone, then into bibrom-anthraquinone, and lastly, into 

 alizarine ; having by this means added four atoms of oxygen to and 

 removed two atoms of hydrogen from the alizarine. The key to the 

 synthetical formation of alizarine having thus been discovered, it was 

 not long before improvements were effected ; for when a particular 

 series of chemical reactions have to be performed, a clever chemist 

 can always find different ways of effecting them, as the records of 

 many a celebrated patent case will show. There are now four pro- 

 cesses in operation, three of which are patented, whilst one is being 

 worked secretly. All effect the same purpose by somewhat similar 

 means, but by the use of different reagents, and all start from an- 

 thracene. Mr. Perkin's patent is now in operation in this country, 

 and his artificial alizarine is in use amongst the Scotch dyers, where 

 it is competing favourably with madder. Besides alizarine, other 

 colouring matters are formed during these synthetical operations; 

 and unless care is taken in the purification, the tones produced by 

 the artificial colouring matter are liable to be somewhat yellowish ; 



