152 
MESSRS. W. R. BOUSFIELD AND C. ELSPETH BOUSFIELD 
Taking the constant value s s = 2'433 for the specific heat of the liquid solute and 
s w = 4T75 for the specific heat of pure water, we can then at once calculate the 
specific heat of the solution by means of the relation 
Es s + Hs-yy 2 5 7 3 A^ 0 
E + H 
In Table XVIII. are set out the necessary data, together with the observed and 
calculated values and the differences, the values of the constant terms being 
E = 58‘46, Es s = 142'25, s w = 4175. 
Table XVIII.—Specific Heat of NaCl Solutions at 20° C. 
No. of 
solution. 
H. 
A Xo- 
%)> 
observed. 
^20) 
calculated. 
Difference. 
I. 
175-38 
4-04 
3-294 
3-295 
+ 1 
II. 
250-12 
4-82 
3-440 
3-443 
+ 3 
III. 
373-98 
5-67 
3-600 
3-602 
+ 2 
IV. 
525-87 
6-23 
3-726 
3-726 
+ 
V. 
980-83 
6-93 
3-907 
3-905 
_ 2 
VI. 
1980-68 
7-60 
4-030 
4-029 
- 1 
VII. 
3979-91 
8-00 
4-099 
4-099 
+ 
Thus, upon the simple assumptions that 
(1) The specific heat s s of liquid NaCl has a constant value 2'433 ; and 
(2) That the mean specific heat lowering of the water in the solution is 
proportional to the mean specific contraction of the water ; 
we are able to calculate the specific heat of the solution for isothermal dilutions 
with errors less than those shown in Table XIV., thus confirming the conclusion that 
of the various very nearly linear empirical laws which have been examined the relation 
A$yj — L A 
is the true law. 
Furthermore, with the aid of the osmotic data, which furnish the number n of 
combined water molecules, the analysis can, as has been shown, be carried still 
further and the specific heats can be separated into three components instead of two :— 
(1) The specific heat of the liquid solute which by, this method of treatment 
again shows the same constant value; 
(2) The specific heat of the combined water, which can be treated as a constant 
within the limits of experimental error, at all events for the more concentrated 
solutions; 
(3) The specific heat of the free water which is expressible as 
S S\ y 1 ' IP • 
