348 THE EARL OF BERKELEY, MESSRS. E. G. J. HARTLEY AND C. V. BURTON: 
might disturb the air stream over the adjacent water sufficiently to upset the steady 
conditions of flow demanded by theory. Testing this hypothesis by an experiment 
in which the sulphuric acid was absent, there was the usual loss in 4. Incidentally 
this experiment strengthens the conclusion come to under (l), and it also shows that 
the heat generated in 5 by the absorption of the water is not the cause of the trouble. 
(3) Nevertheless I am driven to the assumption that a permanent inequality of 
temperature between vessels 3 and 4 is maintained. Unfortunately, when exploring 
the bath by means of thermocouples, as mentioned on p. 318, it was not realized that 
the presence of the train of vessels might make a difference to the free circulation of 
the bath water. A further examination with a Beckman thermometer (reading to 
0°'02 C. and estimating to 0°'002 C.), placed alternately over the last branches of 3 
and 4 respectively (it is only the exit branches that matter), seems to show that the 
latter is 0°'002 C. higher than the former. No stress should be laid on this result, 
for its magnitude only became apparent when the readings had been averaged and 
disentangled from the oscillations in the temperature of the bath as a whole. It is 
noteworthy, however, that a difference of 0°'003 C. between the two vessels is 
sufficient to account for the observed loss. 
Whatever be the cause of the loss of water in vessel 4 of apparatus D, it is obvious 
that a correction should be applied to the experiments with that set of vessels. It 
seems probable that a correction should also be applied to the experiments with the 
other apparatus, but as the method of heating the bath, and the original position of 
the heaters cannot be recovered exactly, I am unable to determine what the correction 
.should be. 
The accompanying table gives, for the experiments with D, the corrected values 
together with the osmotic pressure calculated from the mean log e p 0 /p 1 . 
It will be seen that the percentage difference between the new and old values of 
log, pjp l diminishes as the concentration increases. Taking the values for cane sugar, 
the difference for the weight concentration of 34 gr. per 100 water is about 1 per cent., 
while at 183 it is only 0'14 per cent. ; we may therefore feel confident that for 
higher concentrations the values given in the body of this communication would not 
be modified appreciably even if we were in a position to apply the correction under 
discussion.] 
Sulphuric Acid at 30° C. 
Date. 
Po/Pi • 
l°ge po/Pi- 
Oct. 9, 1915 .... 
1-02502 
0-02472 
„ 20, 1915 .... 
1-02493 
0-02462 
„ 28, 1915 .... 
1-02491 
0-02460 
Nov. 5, 1915 .... 
1-02497 
0-02466 
„ 13, 1915 .... 
1-02482 
0-02451 
„ 24, 1915 .... 
1-02498 
0-02467 
