Eudiometric Combustions of Gases mixed with Nitrogen. 545 



Experiment IV. 



Vol. obs. Temp. 



Atmospheric air . . 79*2 8*4° C 



AfteradmissionofH. 250*4 8*5 



After admission of O. 391*7 8*5 



After combustion . 200*3 8*6 



Hydrogen used . . 

 calculated 



Barom. 

 773*O mm 



773*7 

 773-7 



773*4 



III. 



104*9 

 106*8 



Height of 



mercury in 



tube over 



that in 



trough. Corr.vol. 

 364*2 mm 30-7 



192*4 

 55*8 

 241*9 

 IV. 

 108*4 

 111-9 



139*1 

 269*4 

 101*5 



According to these experiments, it appears impossible to 

 determine accurately in the usual way, by combustion with 

 oxygen, the quantity of a combustible gas Avhen nitrogen is 

 present, on account of the simultaneous oxidation of the ni- 

 trogen producing from 2 to 3 per cent, more hydrogen, as 

 shown by the last two experiments, and which under more 

 unfavourable circumstances is liable to be still increased. 

 Notwithstanding the dilution with atmospheric air, the eleva- 

 tion of the temperature on combustion was so great, that the 

 inner surface of the eudiometer was covered with sublimed 

 mercury, upon which was deposited a number of microscopic 

 crystals ; they made their appearance as soon as the remaining 

 gas was dried by means of chloride of calcium. 



One of the conditions which in the above case appears to 

 be absolutely necessary for the formation of nitric acid, is the 

 great elevation of temperature of the gas during combustion. 

 The lowering the temperature to a certain point is sufficient 

 entirely to prevent the oxidation of the nitrogen. This is best 

 accomplished by diluting the combustible gas with 1, 2 or 3 

 volumes of atmospheric air, by which means the accuracy of 

 the analysis is not in the least affected. The following ana- 

 lysis, where hydrogen was deflagrated with twice its volume 

 of atmospheric air mixed with the requisite quantity of oxy- 

 gen, will justify this assertion, besides which I have been able 

 to confirm it by a series of other experiments. 



Vol. obs. 

 Atmospheric air . .212*3 

 AfteradmissionofH. 282*7 

 After admission of O. 321*6 

 After combustion 



Hydrogen 



Temp. 

 14*2°C. 

 15*1 

 15*4 

 221*7 14*7 



Used. 

 51*6 



Barom. 

 756*9 mm 

 757*4 



758*3 

 758*5 



Height of 



mercury in 



tube over 



that in 



trough. Corr.vol. 

 244*8 mm 100*9 



175*3 

 137*3 

 234*0 



Calculated. 

 51*6 



152*5 

 185*1 

 107*7 



