Mr. De la Rue on Cochineal. 473 



of foreign matter it was dissolved in strong alcohol, and 

 an equal volume of aether added, which precipitated the 

 colouring matter and retained the fat, which was still ad- 

 hering to it. The colouring matter thus purified they named 

 carmine {carminium), and described as being very soluble in 

 water, from which it did not crystallize, more or less soluble 

 in alcohol, according to its strength, and quite insoluble in 

 aether and the fixed and volatile oils. Acids did not precipi- 

 tate it from its aqueous solution if free from animal matter. 

 They found hydrochloric and sulphuric acid to decompose 

 it; the latter with elimination of carbon. By the action of 

 nitric acid they obtained an acid in prismatic crystals resem- 

 bling oxalic acid, but differing in some of its properties. 



On heating the " carmine" it intumesced and gave off carbu- 

 retted hydrogen, a considerable quantity of oily substances, 

 a little acid water, but no trace of ammonia. Chlorine and 

 iodine decomposed it; the alkalies in the commencement 

 produced merely a change in colour, turning it violet, but by 

 the assistance of time or heat they effected a complete altera- 

 tion. They found an aqueous solution of " carmine " to exhibit 

 the following comportment with reagents. 



Of the alkaline earths, lime only produced a precipitate ; 

 hydrate of alumina showed a marked affinity, absorbing the 

 whole of the colouring matter from an aqueous as well as an 

 alcoholic solution ; the presence of alum prevented this reac- 

 tion : iron, copper, and silver salts were without reactions ; 

 terchloride of gold destroyed the colour ; neutral salts of lead 

 merely changed it to violet, except the neutral acetate, which 

 precipitated it, the free acetic acid retaining a little of the 

 compound in solution; the colouring matter could be re- 

 covered by decomposing the lead compound with hydrosul- 

 phuric acid. The nitrate of mercury gave a purple, and the 

 pernitrate a scarlet-red precipitate; the bichloride no pre- 

 cipitate ; chloride of tin gave a violet precipitate ; the bichlo- 

 ride changed the colour to scarlet without causing a precipi- 

 tate. Albumen and gelatine had no marked action, but if 

 precipitated by reagents the colouring matter was carried 

 down. 



In a later communication (1832), Pelletier* gave the com- 

 position of the colouring matter as prepared by himself and 

 Caventou. In a previous qualitative examination they had 

 failed to exhibit the presence of nitrogen which M. Pelletier 

 now detected. The substance was dried in vacuo at a gentle 

 heat to remove every trace of alcohol and aether, and burnt 

 with oxide of copper it yielded — 



* Annales de Chimie et de Physique, sir. 2, tome li. p. 194. 



