OSMOTIC PRESSURES DERIVED FROM VAPOUR-PRESSURE MEASUREMENTS. 335 
If we neglect the experiment of November 22, 1913, where the soda-lime tube was 
found to be nearly blocked up, the first two sets of experiments, as judged by the 
figures in column (11), show very good agreement. It is probable that the experi¬ 
ment of January 8, 1914, is slightly too high, on account of air pulses, a gale blowing 
during the run. 
The experiments of October 26, November 11 and 25, in 1914, are only included to 
show the kind of results obtained when moisture condenses on the connecting tubes 
and in other parts, the magnitude of this is seen from the numbers in columns (7) and 
(8); but the last three experiments are in excellent agreement. In the first three of 
the next set, approximate buoyancy corrections for the specific volume of the 
sulphuric acid are applied, whilst the last three are properly corrected. 
Two important deductions may be drawn :— 
(l) The method, even with a liquid having a vapour pressure as high as 31 mm. 
mercury, is susceptible of considerable accuracy. (2) Confirmation is obtained of the 
view that the losses on the solution and solvent should be equal to the gain of the 
sulphuric acid. 
Experiments with Cane Sugar and a-Methyl Glucoside. —These are given in 
Tables (XI.) and (XII.) and the columns have the same signification as before. 
The numbers in column (12) for both cane sugar and a-methyl glucoside are derived 
from the equation log e p 0 /p 1 = bc + dc 2 —ec 3 where, for cane sugar, h = 5'136xl0 -4 . 
d - l'866x 10 -li , e = 2'335 x 10~ 9 , with a maximum at c = 647 ; and for a-methyl 
glucoside h = 9'088 x 10~ 4 , d = 3'891 x 1CU 6 , and e — 1*511 x 10~ 8 , with a maximum 
at c = 252. The correction for temperature, which in all cases is very small, is 
assumed to be proportional to the temperature interval. 
The numbers in the column headed “jump” (the jump was not determined for the 
a-methyl glucoside solution) were obtained as follows :—When the vessels had been 
weighed at the end of the experiment they were again set up in the bath and a 
Threlfall oil manometer was connected to the air-stream, so that the fall in the 
pressure along the vessels coidd be measured. It was found that at a certain point 
in the oscillation, there was frequently a distinct and rapid throttling action ; the 
numbers in the column record the change of pressure due to this. # We would point 
out that a “jump" taking place at the end of an experiment, when water has 
already been transferred from one vessel to another, is no proof that the obstruction 
has been there during the whole run, and conversely, no “jump ” does not necessarily 
mean that there has not been one during part of the run. 
The “new sugar” mentioned in the sugar column is some specially pure, which 
Messrs. Tate, to whom our thanks are due, kindly gave us. 
* The “ jump ” seems to be connected with the great viscosity of sugar solutions. 
2 Y 
VOL. CCXVIII. 
A. 
