Ltjuivalents of Oxygen and Hydrogen. 625 
If these be collected mixed under N.T.P. they occupy a 
volume 
+ *™?L. = 16809-9 c.c, 
0-0014290 0-00008986 
using the best published values for the density of oxygen and 
hydrogen. 
But as the water has a volume of 9 c.c, the increase in 
volume is 16800*9 c.c. 
The experiments with sodium, sulphate and potassium 
bichromate detailed in the appendix — all the experiments to 
which no exception could be taken on account of the electro- 
lyte, or for other reasons, give the following values for the 
gas evolved per coulomb : — 
0-17396 
0-17390 
0-17398 
0-17401 
398 
391 
394 
. 398 
389 
387 
401 
388 
391 
388 
396 
404 
The mean is 0'17394, with a probable error of ±0*00001. 
Hence the value of the faraday 
16800-9H-0-17394 = 96590 coulombs. 
The corresponding value for the electrochemical equivalent 
of silver is 
-q ( .~qo = 0*0011174 gram per coulomb. 
This is lower than the value legally adopted (0*001118) on 
the basis of Kohlrausch and Rayleigh's experiments, but in 
close agreement with the latest work of Richards. 
P.S. — An attempt was made to allow for the deviations 
from the laws of gases. But the deviations for oxvgen 
and hydrogen being of opposite sign, the total effect is too 
small to be worth taking into account. The uncertaintv in 
the* density of the gases is larger. 
The experiments were carried out in the temporary 
phvsical laboratory of the Transvaal University College ; 
and some trials have been made there with a double 
apparatus, which, it is hoped, will avoid some of the 
sources of error. As, further, a well-constructed permanent 
laboratory is in course of erection, it may be possible to get 
still more concordant results. The author wishes to express 
his indebtedness to Miss ^Winifred Judson, B.Sc, for much 
assistance in the work. 
December 1907, 
