486 Mr. De la Rue on Cochineal. 



349-6 100-00 100-00 



Action of Nitric Acid on Carminic Acid. 



Nitrococcusic Acid. — ^When acting with nitric acid on " car- 

 mine" (carminic acid), MM. Pelletier and Caventou obtained 

 white acid crystals resembling oxalic acid, but differing from 

 this acid in several of its properties. M. Arppe found that 

 the acid produced was oxalic acid. In my experiments I ob- 

 tained the following results : — One pound and a half of crude 

 carminic acid was gradually introduced into ten pounds of 

 nitric acid, spec. grav. 1-4, and digested at a moderate heat; 

 a violent evolution of nitrous fumes succeeded each addition 

 of the carminic acid ; after the whole quantity had been in- 

 troduced and the action had somewhat subsided, the mixture 

 was transferred into a smaller vessel and the action continued 

 at the boiling-point for about two hours ; by this time the 

 greater part of the nitric acid had evaporated, and on with- 

 drawing the vessel from the fire and allowing the mixture to 

 cool, a crystalline cake was obtained, which on examination M'as 

 found to consist partly of a new acid and partly of oxalic acid. 

 To separate the oxalic acid, it was dissolved in a large quan- 

 tity of boiling water and treated with nitrate of lead as long 

 as any precipitate formed ; this was collected and decomposed 

 by boiling with dilute sulphuric acid ; the filtrate from the 

 sulphate of lead yielded a large quantity of prismatic crystals 

 of oxalic acid, which were obtained perfectly white and pure 

 after two or three crystallizations with the aid of a little animal 

 charcoal. 



The yellow liquid filtered from the oxalate of lead was con- 

 centrated and separated from a fresh portion of oxalate which 

 deposited on concentration, the evaporation was then continued 

 until a large quantity of crystals formed; the solution on 

 cooling deposited a very bulky mass of yellow rhombic prisms, 

 which were drained and dried, and re-dissolved in a sufficient 

 quantity of boiling water, which on cooling deposited the acid 

 (for which I propose the name of nitrococcusic acid) in 

 beautiful crystals free from any lead salt ; it was recrystal- 

 lized twice more, by which means it was obtained perfectly 

 pure. 



Several preparations were made, sometimes using pure car- 



