482 Mr. De la Rue on Cochineal, 



again concentrating to dryness, a brown mass was obtained, 

 which on incineration left a greenish- white very hygrometric 

 ash, in which phosphoric acid, soda and copper were found. 

 Burnt with chromate of lead — 



VII. '4020 grm. carminic acid {g) gave '7842 grm. carbonic 

 acid and '1662 grm. water. 



This acid however still retained some impurities : on inci- 

 neration it left 0*4 per cent, of ash ('5489 grm. giving "0022 

 grm. ash), and examined for nitrogen it gave the following 

 numbers : — 



•4731 grm. burnt with soda-lime gave 'OlSOgrm. ammonio- 

 chloride of platinum = 0*2 per cent, of nitrogen. 



h. In order to separate these impurities the greater portion 

 was dissolved in boiling absolute alcohol, and filtered from a 

 slight residue ; the remainder, about an eighth, was converted 

 into carminate of lead and digested with the boiling alcoholic 

 solution for some hours ; the alcoholic tincture filtered off 

 whilst hot and mixed with about six times its volume of an- 

 hydrous aether ; this threw down a bulky precipitate of a fine 

 red colour, which was separated by filtration and the filtrate 

 concentrated in a retort, and finally evaporated to dryness in 

 vacuo {h). 



i. The precipitate retained on the filter was dried in vacuo, 

 then dissolved in as small a quantity of alcohol as possible, 

 and again mixed with a large quantity of aether ; this deter- 

 mined a precipitate which was no longer of a fine red but of 

 a brown colour, and on re-solution and similar treatment it di- 

 minished in quantity and became darker in colour, leaving 

 the colouring matter in solution. From the filtrates a quan- 

 tity of carminic acid {i) was obtained on evaporating to dry- 

 ness in vacuo. It therefore appears that the aether precipi- 

 tates a nitrogenous body which carries down with it variable 

 quantities of carminic acid, according as a larger or smaller 

 relative proportion is present. The carminic acid {h) was 

 found to be free from phosphoric acid as well as nitrogen. 



•3003 grm. burnt with soda-lime gave "001 5 grm. ammonio- 

 chloride of platinum = 0*03 per cent, of nitrogen. 



From this analysis I venture to assert that the colouring 

 principle of cochineal contains no nitrogen, thus fully con- 

 firming the anticipation of Berzelius. We can now under- 

 stand from the preparation of the specimen of carminic acid 

 (e), that the method employed by Pelletier for the prepara- 

 tion of the substance he analysed was calculated to accumu- 

 late all the nitrogenous matter contained originally in his 

 alcoholic decoction ; a fact which fully explains the large 

 amount of nitrogen he obtained in his analysis. 



