PHYSICS: K.-L. YEN 
109 
TABLE 7 
Ethyl Acetate (C 4 H 8 0 2 ) 
p 
u+ 
U- 
K+ 
K - 
R 
50 
3.309 
3.648 
0.219 
0.240 
1.09 
60 
2.567 
3.167 
0.229 
0.250 
1.09 
65 
2.701 
2.900 
0.231 
0.248 
1.07 
70 
2.421 
2.663 
0.223 
0.245 
1.09 
75 
2.290 
2.533 
0.226 
0.250 
1.10 
80 
2.172 
2.334 
0.230 
0.246 
1.07 
Mean 
0.226 
0.247 
1.09 
TABLE 8 
Ethyl Iodide (C 2 H 5 I) 
p 
u+ 
U- 
K+ 
K — 
R 
30 
5.166 
4.833 
0.203 
0.191 
0.94 
35 
4.104 
4.161 
0.189 
0.192 
1.01 
50 
2.466 
2.512 
0.162 
0.169 
1.04 
60 
2.336 
2.296 
0.184 
0.181 
0.98 
60 
2.141 
2.166 
0.169 
0.171 
1.01 
Mean 
0.181 
0.181 
1.00 
TABLE 10 
Comparison 
TABLE 9 
Methyl Iodide (CH 3 I) 
p 
u+ 
U- 
K+ 
K- 
R 
50 
3.222 
3.390 
0.212 
0.223 
1.05 
60 
2.607 
2.926 
0.219 
0.231 
1.06 
65 
2.572 
2.959 
0.220 
0.236 
1.07 
70 
2.296 
2.421 
0.212 
0.223 
1.05 
75 
2.230 
2.270 
0.220 
0.224 
1.02 
80 
2.043 
2.090 
0.215 
0.220 
1.02 
Mean 
0.216 
0.226 
1.05 
VAPOR 
WELLISCH 
K.-L 
YEN 
19091 
19152 
1917 
K+ 
K- 
K+ 
K- 
K+ 
K - 
C 2 H 4 0 
0.31 
0.30 
0.307 
0.331 
C 2 H 6 0 
0.34 
0.27 
0.39 
0.412 
0.363 
0.373 
C 3 H 6 0 
0.31 
0:29 
0.236 
0.247 
S0 2 
0.44 
0.41 
0.415 
0.414 
0.412 
0.414 
C 2 H 5 C1 
0.33 
0.31 
0.304 
0.317 
C5Hi 2 
0.36 
0.35 
0.370 
0.440 
0.385 
0.451 
C 4 H 8 0 2 
0.31 
0.28 
0.226 
0.247 
C 2 H 5 I 
0.17 
0.16 
0.181 
0.181 
CH 3 I 
0.21 
0.22 
0.24 
0.233 
0.216 
0.226 
Conclusion. — From the results of the present experiment, it is evident that 
the apparent difficulty with the explanation proposed for the difference be- 
tween the positive and negative mobilities does not really exist at all. It 
only remains for the exponents of the small-ion theory to deduce an exact 
formula for the mobility of ions on the basis of the Rutherford-Bohr theory 
from which we should expect that the peripheral negative electrons in the 
molecules and the ions would play the dominant if not indeed the only role in 
collisions. 
I wish it to go on record that the present experiment was undertaken at 
the suggestion of Prof, R. A. Millikan, and under his direction; and also 
to thank Mr. W. R. Westhafer for his assistance in taking some of the 
measurements and computing some of the results. 
1 Phil. Trans. R. Soc, London, (A), 209, 1909, (249). 
2 Phil. Mag., London, 34, 1917, (59). 
