SECTION III, 1902 [121 ] Trans. R. 8. C. 
XIV.— On the Specific Heat of Water of Crystallization. 
By Neviz Norton Evans, M.Sc. 
(Presented by Dr. Walker, and read May 27, 1902.) 
Some time ago Prof. Walker called the attention of the writer to 
the fact that the specific heat of water of crystallization in inorganic 
compounds, as calculated from the figures given in Landolt and Born- 
stein’s tables, was very nearly that of ice, 1.e., water in the solid state; 
and a careful calculation of the data showed that this was generally the 
case, although in certain instances there were very extraordinary and 
apparently anomalous exceptions. ‘The number of such substances 
which have been examined in the hydrated and dehydrated condition 
is very limited, but in nine cases the specific heat of the water of 
crystallization only varies from 0-496 for NiSO,-7H.,O to 0:638 for 
BaCl,-2H,O. Sulphates have been chiefly investigated, but even borax 
and tartaric acid give values which lie close to 0:5. The intention is 
to redetermine with as great a degree of accuracy as possible the specific 
heats of these compounds and to extend the investigation to salts of 
organic acids, etc. 
In experimentally investigating the subject the first step was to 
decide upon some method of determining as accurately as possible the 
specific heat of solids. The work so far has consisted in the elabora- 
tion and testing of a method for doing this, the determination of the 
conditions necessary for accurate results being the main object in view 
up to the present time. 
From the first it appeared advisable not to employ the method of 
mixtures as this gives the specific heat over too large a range (1.¢., 
between the temperature to which the solid is heated or cooled and 
the final temperature in the calorimeter), while it is much more desir- 
able to get the specific heat over as small a range as possible, about eight 
degrees being adopted in the present work. As it has been pretty well 
established that electrical methods, wherever applicable, yield much 
more accurate results than other methods, and as this has been amply 
verified in the case of liquid calorimetry by the work of Callendar and 
Barnes on the specific heat of water, it was decided to elaborate such 
a method for the intended investigation. The solid to be experimented 
upon is more or less finely divided and kept suspended in the liquid 
(in which it is insoluble) in the calorimeter by suitable vigorous stir- 
Sec. III., 1902. 8. 
