330 THE EARL OF BERKELEY, MESSRS. E. G. J. HARTLEY AND C. Y. BURTON: 
faulty manipulation. It must be remembered that the tube has to be weighed as 
quickly as possible. 
Column (8). This column is headed “ tot up ” ; by this we mean that the tabulated 
numbers are the difference in weight between the gain in the last vessel of the 
train (which contains sulphuric acid) and the sum of the losses of solution and water ; 
the weight of water found in the “ dipping ” tube is added to that of the sulphuric 
acid, and a negative sign means that the losses are the greater, whilst the positive 
sign means that they are the smaller. It has been pointed out in a previous 
communication that the closer these numbers approach to zero the greater the 
probability that the experiment is a good one. 
Column (9) gives the number of hours during which the air has passed through 
the vessels. 
Column (10) gives pjp x the value of the ratio l 0 /l x corrected for “Burton’s” 
correction (see p. 316) on the assumption that p x and p 0 of equation (3) are equal to 
one another. 
Column (ll) gives log p 0 /p x corrected to the standard weight concentration* 
printed across the page, and also corrected to the standard temperature of 0° C. or 
30° C., as the case may be. 
The Experiments at 30° C.—Before proceeding to enumerate the experiments on 
sulphuric acid solutions it may be mentioned that since the completion of the work on 
calcium ferrocyanide we have made over 60 special test experiments (they are in 
addition to such as are detailed here) which have taken 287 days to complete. For 
the most part these were directed to testing alterations both in the vessels and in the 
speed of the air stream ; a number were devoted to investigating the influence of ions 
in the air current (for this purpose a special set of vessels furnished with electrodes 
was constructed), but with no definite result; others on “ tot up,” and fall of pressure 
along the vessels were also made. The changes thus suggested are embodied in 
Apparatus D, whilst the final method of causing the air to flow is given on p. 316. 
We give an example of what we consider to be a satisfactory experiment at this 
temperature. 
The experiments on sulphuric acid solutions we made more for the purpose of 
testing the experimental conditions than for the determination of vapour pressures. 
But as they have turned out to be sufficiently concordant we give the details in 
Table X. 
From a study of these figures the following remarks seem justified. 
* This correction is obtained from the equation log,, po/pi = be + dc 2 - ee 3 , where r, is the weight concen¬ 
tration and b, d and e are constants. For cane sugar b = 4 - 881x 10“ 4 , d = 2 - 4655x 10 -6 , and 
e = 4-041 x 10~ 9 ; and for glucoside 6 = 9 - 54xl0 -4 , d = 4‘921 x 10~ 6 , and e— l‘668 xl0~ s . There 
is a maximum at c = 489 for cane sugar and one at c = 204 for the glucoside. 
