IN GASES: HYDROGEN, CARBONIC OXIDE, AND OXYGEN. 
649 
below a certain limit. The lower the pressure below this limit the greater is the 
change produced. The limit varies with different mixtures: when a small percentage of 
oxygen is present the limit is higher than when the mixture is richer in oxygen. With 
pressures in excess of this limit no alteration is produced in the division of the oxygen 
bv changes in the length of the column. 
To determine what is the effect produced by a change of initial pressure alone on 
the proportion of carbonic oxide and oxygen burnt with the same length of column 
and at the same temperature, a series of experiments was made with portions of one 
mixture, starting at the lowest pressure at which the explosion was propagated, and 
increasing the pressure up to 600 millims. 
Composition of mixture. 
Carbonic oxide . 61'64 
Hydrogen. 25‘50 
Oxygen. 12’8 6 
100-00 
This mixture would not explode under 50 millims. or under 60 millims. pressure. 
It exploded under a pressure of 7 5 millims. 
Table XII.—Experiments at different pressures. Length of column =450 millims. 
Reference 
No. 
Pressures. 
„ • CO, 
Katio jj q 
Temperature. 
millims. 
° C. 
22 
75 
1-27 
6'5 
23 
100 
1-21 
5 - 6 
24 
125 
1-01 
6-4 
25 
150 
•95 
6'5 
26 
200 
•92 
5'8 
27 
300 
•85 
6-9 
28 
425 
•81 
7-0 
29 
600 
■82 
6'4 
From this table it appears that, as the pressure is increased, less carbonic oxide and 
more hydrogen is burnt until a pressure of about 400 millims. is reached, after which 
a further increase of pressure makes no difference in the division of the oxj^gen. To 
establish this important point more surely, a second series of experiments was per¬ 
formed in a similar way. Different portions of a mixture were exploded between the 
lines 400 and 500 on the eudiometer, under pressures varying from 75 millims. to 
1000 millims. 
4 o 
MDCCCLXXXIV. 
