PRESSURES PRODUCED BY GASEOUS MIXTURES. 389 



According to Bunsen's experiments, 1 made by raising a valve 

 loaded with a weight, a mixture of carbonic oxide and oxygen 

 burnt at constant volume only develops 10*3 atm., instead of 

 24 as calculated. The number observed would correspond to the 

 combination of only one-third of the mixture on the hypotheses 

 of dissociation. Such a calculation is, however, based on the 

 employment of far too low a specific 2 heat for the carbonic acid. 



A mixture of hydrogen and oxygen, burnt at constant volume, 

 develops also, according to Bunsen, 9*6 atm. instead of 20 atm. 

 as calculated. The number observed would correspond again 

 to the combination of a third of the mixture on the hypotheses 

 of dissociation, but it is subject to the same objection for the 

 specific heat. 



Mallard and Le Chatelier arrived at approximate experi- 

 mental values by their measurements, based on the employment 

 of a metallic manometer; say 8*6 atm. for the mixture of 

 carbonic oxide and oxygen, 9*2 atm. for the mixture of hydrogen 

 and oxygen, 14 atm. for methane and oxygen, 8 atm. for chlorine 

 and hydrogen, etc. 



The following are the numbers observed by the author and 

 M. Vieille with the principal detonating mixtures, by another 

 method based on the registration of the pressures by means of a 

 movable piston : 



Hydrogen and oxygen : H 2 + ...... 



Hydrogen and nitrogen monoxide : H 2 + N 2 

 nitrogen and oxygen : H 2 + N 2 + 



: H 2 + 2N 3 + 

 Carbonic oxide and oxygen : CO + ...... 



and nitrogen monoxide : CO + N 2 

 nitrogen and oxygen : CO + N 2 + 

 :CO + N + 

 hydrogen and oxygen : CO + H 2 + 2 



atm. 



7'7 atm. to 9 6 3 

 11*1 

 8'2 

 7-4 

 9-4 

 9 -7 

 7'7 

 8-0 

 7-8 



6 5 8-3 



Methane and oxygen : CH 4 + 4 ............ 13-6 



Acetylene and oxygen : C 2 H 2 + 6 ............ 13'7 



Ethylene and oxygen : C 2 H 4 + 6 ............ 13-8 



Ethane and oxygen : C 2 H 6 + 7 ............ 11-9 



Ethylene, hydrogen, and oxygen : C 2 H 4 + H 2 + 7 ...... 13-3 



Cyanogen and oxygen : 2CN + 4 ............ 19*5 



Cyanogen, nitrogen, and oxygen: 2CN + N 2 + 4 ...... 15'6 



Cyanogen gives the maximum pressure according to theory. 

 However, the values observed are only two-fifths of the 

 theoretical values for hydrogen, carbonic oxide, and methane. 

 They are reduced to about a third for the other hydrocarbons 

 and for cyanogen. 



It results from these indications that the real relations of the 



1 " Annales de Chimie et de Physique," 4 e se*rie, torn. xiv. p. 446. 1868. 



2 See the author's remarks on this point (" Annales de Chimie et de Phy- 

 sique," 5' s^rie, torn. xii. p. 306). 



3 According as the experiment was made in a chamber of 300 cc. or 4 litres. 



