422 
DR. F. P. BURT AND DR, E. C. EDGAR ON 
Table VI. 
1. 
Oxygen 
excess. 
2 
Oxygen 
residue. 
3. 
Difference. 
4. 
Ratio of 
combining 
volumes. 
5. 
Atomic weight 1 
of 
hydrogen. 
c.c. 
c.c. 
c.c. 
1 
0 
0-428 
0-428 
2-00279 
1-00768 
2 
1 -533 
2-021 
0-488 
2-00318 
1-00788 
3 
1-084 
1 - 551 
0-467 
2•00305 
1-00781 
4 
0-508 
0-933 
0 - 425 
2-00277 
1-00767 
Mean .... 
2-00295 
1-00776 
Maximum deviation, 1 in 5000. 
Omitting experiment 2, mean . . 
2-00287 
1-00772 
Maximum deviation, 1 in 7000. 
The ratio may be calculated from compressibility measurements. If the com¬ 
pressibility coefficient of hydrogen at 0° C., between 0 and 1 atmospheres, is 
taken as +0'00054 (the mean of the values obtained by Rayleigh, Jaquerod 
and Scheuer, and Chappuis) and the corresponding coefficient of oxygen as 
— 0'000964 (Gray and Burt), then the ratio of the volumes containing equal 
numbers of molecules at N.T.P.is 
1 + Q-Q0054 
1-0-000964 
and the ratio of the combining volumes 
2 ( 1+Q . Q(jQo f) = 2-00303 
t-0’000964 
Purity of the Gases. 
Provided that the source of the gas and the methods of purification are varied, the 
best criterion of purity is afforded by the concordance of the results. 
Neither of the gases, in the condition in which they left the trains, yielded any 
residue when pumped through a spiral cooled in liquid air. 
The liquefied oxygen left no residue on evaporation, and the results did not vary 
according to the fraction taken. Nitrogen might occur as an impurity owing to 
incomplete exhaustion of the trains, or to a faulty tap. In the first case the quantity 
would diminish throughout a series and, since the resulting error would not be 
constant, it could hardly escape detection. The taps on the apparatus were selected 
