286 
Proceedings of the Koyal Society of Edinburgh. [Sess. 
To get the figures denoted by /3 F in the table on pp. 287 and 288 we 
proceed as follows : — 
Take the values of P, 279 and 390, with the corresponding values of 
v, ’544 and *750 ; then we have a change of pressure of 111 giving a change 
of volume of '206. Hence 
Av _ -206 
~Ap~ TIT 
and 
1 Av _ 1 
V 0 ' A p 4640 
^ = •0000402. 
Hence /3 F = *0000402 -f ’0000022 = *0000424, where 22 x 10 -7 is the com- 
pressibility of glass, and this is the number given in column 3 in the tables 
as corresponding to the pressure 335, viz. J(279 + 390). 
It will be clear from what follows how the value "0000022 for the 
compressibility of glass was obtained. 
According to Tait,* for water, compressibility and pressure are connected 
by the following formula : 
• • • ( 1 ) 
As Tammann j- 
_1_ dv_ 
v 0 dp B+p 
where A and B are constants for a given temperature, 
states, this formula is satisfied by the results of Amagat’s J observations on 
the compressibility of water from 0 to 3000 atmospheres. He gives the 
values of A and B for various temperatures. Interpolating, we get for 15° 
A = *1238. 
B = 2540. 
I took a series of observations on the compressibility of water with the 
same piezometer as was used for the solutions. I then used equation (1) 
with the values for A and B just mentioned, and found that it was satisfied 
if the compressibility of glass was taken to have the mean value 22 x 10 -7 . 
This value for the compressibility of glass was used in calculating the 
compressibilities of the various solutions. 
Further, as indicated by Tait, and developed theoretically by 
Tammann, when a solution of a salt is made in water, the compressibility 
of the solution can be expressed by the formula 
1 dv 1 A 
v 0 dp~v AK ' B+ AK +p 
In formula (2), A and B are the same constants as before; AK has the 
dimensions of a pressure, and may be taken as a measure of the increase 
of internal pressure due to the solute ; v AK is the volume which unit 
* Proc. Roy. Soc. Edin ., 1893. 
t Ueber die Beziehungen zwischen den inneren Krdften und Eigenschaften der Losungen 
(1907). 
f Com'ptes Rendus , 1893. 
