480 Mr. De la Rue on Cochineal. 



Burnt with chromate of lead, — 



I. '4647 grm. gave '9096 grm. carbonic acid and '2175 grm. 

 water. 



JI. •4630 grm. gave '9105 grm. carbonic acid and '2140 

 grm. water. 



For the latter analysis I am indebted to my friend Mr. Ni- 

 cholson. 



b. A second preparation of carminic acid was made by 

 operating on the crude carminate of lead (C) and treating the 

 resulting crude carminic acid in the manner just described for 

 the preparation a. It left on incineration 0*2 per cent, of ash 

 (•1609 grm. giving '0003 grm. ash), which was neglected in 

 the following analyses : — 



III. '3710 grm. gave '7316 grm. carbonic acid and '1710 

 grm. water. 



IV. '3685 grm. gave '7235 grm. carbonic acid and '1722 

 grm. water. 



c. To effect the purification of the carminic acid (D) ob- 

 tained by digesting cochineal in alcohol, it was dissolved in 

 water and precipitated by acetate of lead; the filtrate was found 

 to contain nitrogenous matter,' and the carminate of lead to 

 be contaminated wath phosphate of lead; it was therefore 

 treated in the manner already detailed. 



V. "3925 grm. of this substance gave "7658 grm. carbonic 

 acid and •1780 grm. water. 



d. A fourth preparation of carminic acid was obtained by 

 substituting phosphoric acid for hydrosulphuric in the de- 

 composition of the crude carminate of lead (C), and evapo- 

 rating the carminic acid to dryness in contact with a fresh 

 portion of carminate of lead ; this did not however separate 

 entirely the phosphoric acid, it was therefore redissolved in 

 boiling absolute alcohol, and maintained some time at that 

 temperature with more carminate of lead. On analysis — 



VI. ^3805 grm. gave "7530 grm. carbonic acid and •1848 

 grm. water. 



Pelletier having obtained in his analysis of " carmine" 

 (carminic acid) as much as 3*56 per cent, of nitrogen, all the 

 before-cited preparations of carminic acid were carefully exa- 

 mined qualitatively for nitrogen by heating with soda-lime, 

 and without exception gave indications of its presence; in 

 most cases but a mere trace was found, but I thought it ne- 

 cessary notwithstanding to make a few quantitative determi- 

 nations, especially as M. Berzelius* had pointed out the im- 

 probability of it being an essential constituent. 



* Traite de Chim. t. iii. p. 808. Brussels, edit. 1839. 



