418 
MR. W. CROOKES OK THE VISCOSITY 
Table IV. (continued).—Log. dec. of carbonic anhydride at pressures between 1000 M 
and 7'6 M. Temp. 15° C. 
Pressure. 
Log. 
Repulsive force 
M 
decrement. 
of radiation. 
1000 ( = 0'76 m.m.) 
0-0809 
1- 
588 
0-0790 
2- 
523 
0"0785 
2- 
389 
0-0780 
2- 
345 
0-0776 
2- 
228 
0-0770 
3- 
177 
0-0758 
5- 
158 
0-0750 
7- 
91 
0*0717 
13- 
66 
0-0697 
15- 
58 
0-0684 
19- 
40 
0-0630 
25- 
32 
0-0600 
25- 
15 
0-0424 
16- 
10 
0-0347 
ll- 
9 
0-0325 
lO- 
7-6 
0-0298 
8- 
679. The curves given in diagrams A, B, and C are plotted from the above observa¬ 
tions. At first the curve seems to follow the same direction as the air curve. But at 
a pressure of about 620 millims. it slopes more rapidly till the pressure is reduced to 
about 50 millims., when the curve again takes the direction of the ah’ curve. The 
total diminution between 760 millims. and 1 millim. is nearly double that of ah. 
The proportion between the viscosity of carbonic anhydride and ah at 760 millims. 
is 0’9208. Graham* found it to be 0'807, and Kundt and Warburg t 0’806. 
Maxwell| ma de it 0’859 (706). 
680. The curve showing the variation in the repulsive force of radiation, shown in 
dots in diagrams B and C, commences late and falls off early, the maximum being very 
inferior to that obtained in the other gases examined. 
OBSERVATIONS ON THE SPECTRUM OP CARBONIC ANHYDRIDE. 
681. Observations have also been taken with the spectroscope during the exhaustion 
of carbonic anhydride. The maximum brilliancy of the spectrum occurs at an exhaus¬ 
tion of about 300 M. After that it gets fainter; at about 75 M the blue band (X 409 
to X 408) disappears; as the exhaustion gets higher the other bands vanish until, at 
* ‘ Chemical and Physical Researches,’ p. 179. 
t Phil. Mag., July, 1875. 
1 Phil. Trans., 1866, Part I., p. 257. 
