Dr. Schunck on Colouring Matters. 213 



time that I thought it probable that alizaric acid might alsobefortned 

 by acting on alizarine with nitric acid. This supposition has since 

 been confirmed. On treating pure crystallized alizarine with boiling 

 nitric acid, it is decomposed with an evolution of nitrous acid, and the 

 liquid on evaporation gives crystals of alizaric acid. It is however 

 not necessary to prepare pure alizarine in order to obtain alizaric 

 acid. 1 have found the following to be the easiest method : — Nitric 

 acid of about sp. gr. 1*20 having been put into a retort, garancine 

 is introduced into the acid, and the liquid is heated until the red 

 fumes have ceased to be evolved, and the colour of the garancine 

 has changed from dark brown to yellow. The reddish-yellow acid 

 liquid which is obtained, is filtered or strained to separate it from 

 the woody fibre, &c. of the garancine, and evaporated to crystalli- 

 zation. A yellow crystalline mass is obtained, which is a mixture 

 of oxalic acid and impure alizaric acid. After being washed with 

 cold water to remove the excess of nitric acid, the mass is dis- 

 solved in boiling water, and chalk is added until all effervescence and 

 acid reaction have ceased. The liquid is filtered, and the oxalate 

 of lime remaining on the filter is washed with boiling water, until 

 no more lime can be detected in the percolating liquid. The liquid 

 is a solution of alizarate of lime. Muriatic acid is added to it, and 

 it is evaporated to crystallization. A yellow mass is again obtained, 

 which may be washed with cold water to remove the chloride of cal- 

 cium, then redissolved in boiling water. It forms a yellow solu- 

 tion, which may be almost decolorized by animal charcoal. On 

 again evaporating, the alizaric acid is obtained in large crystals. 

 Should these crystals still retain a yellow tinge, which is generally 

 the case, they must be redissolved in boiling water. By passing 

 chlorine gas through the boiling solution, until every trace of co- 

 lour has disappeared, perfectly colourless crystals of the acid are 

 obtained on cooling. Prepared in this way, it appears in large flat 

 rhombic plates: it has the properties which I described in my last 

 report. 



The salts of alizaric acid are mostly soluble. Alizarate of potash 

 is formed by neutralizing a watery solution of alizaric acid with 

 carbonate of potash : it is obtained on evaporation as a deliquescent 

 mass. Alizarate of lime is prepared by neutralizing alizaric acid 

 with carbonate of lime, and evaporating to crystallization. It crystal- 

 lizes in prisms, possessing great lustre. Alizarate of baryta, prepared 

 in the same way by means of carbonate of baryta, crystallizes in 

 silky needles. Alizarate of silver, prepared by double decomposi- 

 tion, is soluble in boiling water, from which it crystallizes on the 

 solution cooling. Alizarate of lead is an insoluble white powder, 

 obtained by precipitation of the acid with sugar of lead. With am- 

 monia alizaric acid does not seem to form a neutral salt. On su- 

 persaturating a solution of the acid with ammonia and evaporating, 

 the solution acquires during evaporation an acid reaction, and at 

 length a salt crystallizes out in flat plates, which is no doubt a super- 

 alizarate of ammonia. All the salts of alizaric acid, when strongly 

 heated, are decomposed with an evolution of a fragrant smell similar 



