136 
MESSRS. W. R. BOUSFIELD AND C. ELSPETH BOUSFIELD 
The final values are set out in figs. 2 and 3. Since we are concerned with the 
mean specific heats for intervals of 13° C., it will be seen that the equality of values 
for water at the mean temperatures of 20° C. and 33° C., as shown on the diagram, 
is the result of a minimum value of the actual specific heat at a temperature between 
20° C. and 33° C. In the case of KC1 solutions the minimum disappears with 
solution IV., which is about normal. In the case of NaCl the minimum disappears 
with solution VI., which is about half normal. By the time the most concentrated 
solutions are reached the specific heats in both cases increase regularly with 
temperature according to a simple linear law. 
7° 20° 33“ 
It appears, therefore, that the temperature-specific heat curves like temperature- 
specific volume curves indicate the simplification of the solution with increasing 
concentration. The latter characteristic of aqueous solutions has already been 
discussed in a former communication, where a typical set of density curves are given 
(Bousfield and Lowry, ‘ Phil. Trans.,’ A, vol. 204, pp. 283 and 312, 1905). The 
minimum value which appears in the specific heat curve of water at about 25° C., 
like that which appears in the specific volume curve at about 4° C., is to be attributed 
chiefly to the large proportion of ice molecules which exist in water at such 
temperatures, and, to a lesser extent, to the increasing proportion of steam molecules 
at higher temperatures (see Section 16). With the introduction of the solute the 
