472 Mr. De la Rue on Cochineal 



analogy in the chemical properties of a variety of colouring 

 matters with indigo blue. 



Before entering into the detail of my experiments, I think 

 it desirable to give a brief outline of the results obtained by 

 the chemists who have hitherto worked on this subject. 



Dr. Jean Frederic John, in a quarto volume translated 

 from the German and entitled Tableaux Chimiques du liegne 

 Animal, appears to have published the first analysis of cochi- 

 neal : he does not describe his method, but merely states that 

 it contains the following per-centage : — 



Colouring principle (semi- solid, soluble in"\ cn.nn 



water and alcohol) j 



Gelatine 10-50 



Waxy fat 10*00 



Modified mucus 14-00 



Membrane 14-00 



Alkaline phosphates and chlorides, phosO 



phate of lime, phosphate of iron, and > 1'50 



phosphate of ammonia J 



100-00 



Pelletier* and Caventou, in a very long memoir read before 

 the Institut de France in 181S, have gone very elaborately 

 into the examination of cochineal and obtained many interest- 

 ing results. In analysing this substance they employed the 

 following process : — They removed the fatty bodies by boiling 

 aether, in which they found the colouring matter but slightly 

 soluble ; these fatty substances, recovered by distilling off the 

 aether, were considered to consist of stearine, oleine, and an 

 aromatic acid, from which latter substance it was difficult to 

 remove the adhering colouring matter. 



The cochineal, exhausted M'ith aether, M'as treated with al- 

 cohol of 40° Beaume, which dissolved the colouring matter, 

 together with a small quantity of fatty and nitrogenous sub- 

 stances. 



On cooling, and by spontaneous evaporation, they obtained 

 a granular red residue of a semi-crystalline appearance, and 

 which they considered to be the colouring matter contami- 

 nated still with nitrogenous matter {maiiere animalisee) and 

 some fatty bodies, the greater part of which remained undis- 

 solved in strong cold alcohol; by repeating the operation 

 once or twice they considered that the substance was ob- 

 tained almost in a state of purity. To remove the last traces 



* /nnales de Chiniie ef. de Physique, ser. 2, tome viii. p. 250. Journal 

 de Pharmacie, ser. 2, tome iv. p. 193. 



