SECTION III., 1902 [108 ] Trans. R. $. C. 
XI.— The Specific Heats of Organic Liquids and their Heats of 
Solution in Organic Solvents. 
By J. WALLACE WALKER, M.A., Ph.D. 
AND 
JAMES HENDERSON, B.Sc., Ph.D. 
(Read May 27, 1902.) 
Although the heat of solution has formed the subject of many 
investigations the results obtained have aided very little in the develop- 
ment of our ideas regarding the nature of this phenomenon. One 
reason for this may be that the materials mostly employed as solutes 
have been chosen from the class of substances called electrolytes, whose 
thermal behaviour on solution is known to be greatly complicated by 
ionic dissociation. A second reason is also most probably to be found 
in the nature of the solvent employed, viz., water. Ramsay and 
Shields have shown from surface tension measurements that water in 
the liquid form has not the simple molecular formula H,0, but [H,0], 
where n is about 1-7 at the freezing point and decreases with rise of 
temperature. It is hardly to be imagined, therefore, that the total 
heat change during solution in such a solvent, except at great dilution, 
is due to the solute. Some of it is most likely to be attributed either 
to the splitting up of the complex water molecules into simpler ones, 
or to the condensation of simple into complex molecules. A further 
source of complication is also to be found in the fact that many of the 
substances investigated are crystalline solids, and an unknown amount 
of heat is certainly involved in their passage from the crystalline con- 
dition. It seems, therefore, probable that if a generalization is to 
be derived at all from such observations, substances should be chosen 
for examination whose structure is of the simplest nature, and where 
there is least cause to attribute part of the thermal effect to any kind 
of chemical interaction. The work of Ramsay and Shields has demon- 
strated that water, the alcohols and the liquid aliphatic acids are all 
substances of a considerable degree of molecular complexity, while the 
hydrocarbons and the esters, along with many other liquids, consist 
almost entirely of simple molecules. The latter, therefore, form the 
ideal class to choose as solvents. : - 
Qualitative. The results of a few preliminary experiments con- 
firmed this conclusion and indicated the main lines of the investigation. 
Sec. III., 1902. 7. 
