COLOURING MATTERS OF MADDER. 
vegetable substances, viz. alizarine, rubiacine, alpha-resin, 
beta-resin, rubian, pectic acid and oxidized extractive. The 
examination of the fluid was next made; it was found to 
contain xanthic acid, madder-yellow and sugar. The con- 
tinued investigation of the subject has led to the conclusion 
that there is but one colouring matter in madder, L e. the 
alizarine ; and that the substance which was thought to be 
a colouring matter, viz. rubiacine, is not so. 
It is known that after madder has been employed for 
dying, it still contains colouring matter, and that the article 
garancine is manufactured from this. By treating this sub- 
stance with boiling muriatic acid, it was found to contain 
lime, magnesia, oxalate of lime, phosphate of lime, alumina 
and peroxide of iron. After these salts were separated, 
boiling water extracted a large quantity of colouring mat- 
ter, which would dye mordanted cloth quite full, and of the 
same colour as madder itself, thus showing that it contains 
alizarine. Alizarine is found to be composed of — 
or, in fact, of carbonic acid and water. Alizaric acid is form- 
ed by treating alizarine with concentrated persalts ofironor 
nitric acid. The salts of this acid are mostly soluble. Ali- 
zarate of lime is prepared by neutralizing alizaric acid with 
carbonate of lime, and evaporating to crystallization. It 
crystallizes in prisms possessing great brilliancy. Alizarate 
of baryta, prepared in the same way by means of carbonate 
of baryta, crystallizes in silky needles. Alizarate of silver, 
prepared by double decomposition, is soluble in boiling wa- 
ter, from which it crystallizes as the solution cools. Aliza- 
rate of lead is insoluble. By subjecting alizaric acid to 
heat, it is volatilized, and forms a sublimate in the shape of 
long white needles, to which the name of pyro-alizaric acid 
is given. By solution in water, pyro-alizaric acid appears 
to be again converted into alizaric acid. Rubiacine was 
Carbon 
Hydrogen 
Oxygen 
56.97 
4.19 
3S.S4 
