230 
ME. J. ZELENY ON THE VELOCITY OF THE IONS 
These results are represented at III. in fig. 17. 
By finding the difference between these points and the values in the curves above 
them corresponding to the same value of T, the diminution in the velocity is obtained 
that is produced by the addition of 14'4 — 3'4 = 11 per cent, of air. Assuming that 
up to this point the diminution in the ionic velocity is proportional to the amount of 
air present in the gas, the velocity in pure hydrogen is found by adding to the value 
obtained when 3'4 per cent, of air was present yp part of the diminution observed as 
due to 11 per cent, of air. From the above results this correction is found to be '65 
for the negative ions and '50 for the positive ions. Disregarding any minor correc¬ 
tions, the final result for pure dry hydrogen is thus found to be 7'9 5 centims. per 
second for the negative ions, and 6'70 centims. per second for the positive ions at a. 
pressure of 76 centims., and at a temperature of about 20° C. 
A summary of the results obtained with hydrogen saturated with aqueous vapour, 
and containing 1'5 per cent, of air, is given in Table XXI. 
Table XXI.—Moist Hydrogen. Summary of Results. 
Eeference 
number. 
X. 
U. 
A. 
T. 
Tempera¬ 
ture. 
Gas 
pressure. 
Ionic velocity. 
Negative. Positive. 
! 
°C. 
1 
2-95 
43-9 
- 14-6 
•067 
20 
774 
5-26 — 
2 
2-95 
43-7 
- 15-0 
•0671 
20 
774 
5T0 — 
3 
2-95 
43-7 
+ 15-5 
•067 
20 
774 
4-97 
4 
2-95 
43-3 
+ 15-9 
•068 
20 
774 
— 4-80 
5 
2-95 
434 
- 15-0 
•069 
20 
774 
5-03 — 
6 
2-95 
23-8 
- 8-43 
T2 
19-8 
76-9 
4-98 — 
7 
2-95 
23-5 
- 8-76 
•13 
19-8 
76-9 
4-72 — 
8 
2-95 
23-4 
— 8 - 64 
T3 
19-8 
76-9 
4*77 
9 
2-95 
23-3 
+ 8-77 
•13 
19-8 
76-9 
— 4-68 
10 
2-95 
23-3 
+ 8'69 
•13 
19-8 
76-9 
4-73 
11 
2-95 
34-2 
+ 13-3 
'087 
19-8 
77 
453 
12 
2-95 
344 
+ 13-8 
•087 
19-8 
77 
4-37 
13 
2-95 
34 
-12-4 
•087 
19-8 
77 
4-82 
14 
2-98 
> 19-8 
■ 8-74 
•15 
20-4 
76-7 
3-93 — 
15 
2-98 
19-7 
+ 8-97 
•15 
20-7 
76-9 
3-82 
The results 1 to 13 are represented by IV. of fig. 17. 
The results 14 and 15 were obtained with moist hydrogen containing 8 per cent, of 
air. These two were selected out of a number of results of which they represent 
about the average values. They are shown by A", of fig. 17, and by means of them 
the correction for the air present in the above experiments was made in the same 
manner as with dry hydrogen. The points IV. in the figure are so scattered that the 
inclination of the lines drawn through them had to be estimated mainly by 
comparison with those for dry hydrogen, remembering that with the smaller 
