Mr. De la Rue on Cochineal, 4A% 



minic acid, at other times carminate of lead, with similar re- 

 sults. 



The analyses of four different preparations dried at 100° 

 C. gave, on burning with chromate of lead (unless otherwise 

 stated), the following numbers : — 



I. '3152 grm. {a) gave '3892 grm. carbonic acid and '0561 

 grm. water. 



II. "2500 grm. (a) gave '3080 grm, carbonic acid and '0445 

 grm. water. 



(For this analysis I am indebted to Mr. Nicholson.) 



III. '3068 grm. (a) gave '3820 grm. carbonic acid and 

 •0502 grm. water. 



IV. '4498 grm. {b) gave '5626 grm. carbonic acid and 

 •0757 grm. water. 



V. '4461 grm. (c) gave '5515 grm. carbonic acid and '0777 

 grm. water. 



VI. '4503 grm. (c?) gave, on being burnt with oxide of 

 copper, '5585 grm. carbonic acid and '0757 grm. water. 



VII. '4796 grm. (c) gave, on being burnt with oxide of 

 copper, and a layer of copper twelve inches long used so as 

 to completely decompose the binoxide of nitrogen, '5882 grm. 

 carbonic acid and '0815 grm. water. 



The foregoing analyses lead to the following per-centage 

 quantities : — 



I. II. III. IV. V. VI. VII. 



Carbon . 33-67 33*60 33-95 34-11 33-72 33-82 33-44 

 Hydrogen 1-98 1-98 1-82 1-87 1-93 1-87 1*89 



In the following experiments the nitrogen of the nitrococ- 

 cusic acid was ascertained by burning with oxide of copper 

 in an atmosphere of carbonic acid. 



VIII. -6808 grm. {h) dried at 100° C. gave 84 cub. cent, of 

 moist nitrogen at 6°-5 C. and 0*7585 m., barometer corrected. 



IX. '7162 grm. (c) dried at 100° C. gave 91-5 cub. cent, of 

 moist nitrogen at 17°*5 C. and 0*7641 m., barometer corrected. 



These numbers correspond to the following per-centage 

 quantities : — 



VIII. IX. Mean. 



Nitrogen . . 15-03 14-92 14-97 



X. In this experiment the nitrogen was determined accord- 

 ing to Bunsen's* method, which consists inhuming the sub- 

 stance mixed with oxide of copper in the presence of copper 

 turnings in a hard glass tube. The tube being freed from air 

 by a stream of hydrogen, is then exhausted, sealed hermetically, 

 and placed in an iron mould filled with plaster of Paris ; it is 

 then heated to redness and allowed to cool. After the com- 



* Liebig's ^nnalen, vol. xxxvii. p. 27. 



