488 Mr. De la Rue on Cochineal. 



bustion, the gas is transferred into a graduated jar over mer- 

 cury and its volume noted ; the carbonic acid being absorbed 

 by a potash ball, the volume is again read off. This analysis 

 gave the following numbers : — 



Vol. Temp. Diff. of level. Barom. 

 Carbonic acid -f nitrogen (moist) 123 20°'7 C. 0"'-0640 0'"-7543 

 Nitrogen 22-2 20°-0 O^-IGSO 0-"7529 



The height of the column of mercury in the eudiometer 

 above the level in the trough and the barometric column are 

 corrected for temperature. 



Carbonic acid -\- nitrogen corrected to 0° C. and barom. 1™ := 76-84 



Nitrogen 0° ... 1°' = 12-16 



Carbonic acid 0° ... l'" = 64-68 



■ - ., - = 5-32, which is the ratio of carbon equivalents to one 



I2"lb 



nitrogen equivalent. 



The preceding analyses of nitrococcusic acid agree with the 

 following formula, confirmed by the analyses of several of its 



By analysis VII., in which the precaution was taken of 

 using a very long layer of copper turnings, there was ob- 

 tained, carbon 33-44, hydrogen 1-89 ; these numbers agree 

 as closely as possible with the theoretical quantities, as does 

 likewise the nitrogen determination (X.) by Bunsen's method ; 

 in this experiment the ratio of carbon equivalents to nitrogen 

 equivalents was found to be as 5*32 to 1, or as 16 equivs. of 

 carbon to 3-007 equivs. of nitrogen ; taking analysis VII. as 

 the basis of calculation, it gives 14'67 per cent, of nitrogen, 

 the theoretical number being 14-63. 



The acid, as it separates from its aqueous solution, contains 

 water of crystallization, which it loses at 100° C. ; four expe- 

 riments gave the following results : — 



•4800 grm. lost -0289 grm. = 6-02 per cent. 



-6613 -0395 ... =5-97 



•6586 -0385 ... =5-84 



•4804 -0289 ... =6-01 



Mean . . =5*96 



