410 
MR. W. CROOKES OjST THE VISCOSITY 
Table II. (continued).—Log. dec. of oxygen gas at pressures between 1000 M and 
0'3 M. Temp. 15° C. 
Pressure. 
Log-. 
Repulsive force 
M 
decrement. 
of radiation. 
lOOO'O (—0‘76 m.m.) 
0-1102 
12- 
803*0 
0-1093 
12- 
658"0 
0-1088 
13- 
623-0 
0-1086 
13- 
613-0 
0-1085 
13- 
360-0 
0-1070 
13- 
297-0 
0-1058 
14- 
190-0 
0-1038 
20- 
171-0 
0-1033 
2T 
110-0 
0-0988 
31- 
82-0 
0-0940 
35" 
70-0 
0-0912 
38- 
48-0 
0-0840 
45" 
31-0 
0-0744 
44- 
28-0 
0-0724 
44- 
22-0 
0-0670 
40- 
16-0 
0-0621 
35’ 
12-0 
0-0585 
30- 
4-0 
0-0433 
14- 
1-6 
0-0348 
7" 
0-3 
0-0302 
2" 
668. These figures, plotted as curves on diagrams A, B and C, show a great 
similarity to the air curve. Like it, the viscosity sinks somewhat rapidly between 
pressures from 760 millims. to about 75 millims. It then remains almost steady, not 
varying much till a pressure of 16 millims. is reached. Here, however, it turns in the 
opposite direction, and steadily increases up to 1'5 millim. It then diminishes again, 
and at higher exhaustions it rapidly sinks. This increase of viscosity at pressures of 
a few millimetres has been observed in other gases, but only to so small an extent as 
to be scarcely beyond the limits of experimental error. In the case of oxygen, 
however, the increase is too great to be entirely attributable to this cause. 
669. Oxygen has more viscosity than any gas I have yet examined. The viscosity 
of ah- at 760 millims. being 0T124, the proportion between that of air and oxygen, 
according to these results, is IT 185. Graham* makes it 1T099 (706). I have 
been unable to find viscosity results of oxygen given by any other observers. 
This proportion of IT 185 holds good (allowing for experimental errors) up to a 
pressure of about 20 millims. Between that point and 1 millim. variations occur, 
which I have not been able to trace to any assignable cause : they seem large to be 
*Loe. tit., p. 179. 
