929 
fact that previous thermal treatment must be taken into account. 
It will be proved below that the metals experimented with by 
Messrs. Grirritas did not correspond to definite states: the values they 
found for the specific heat must therefore be considered as fortuitous 
values. This is the more to be regretted as their measurements were 
carried out with the greatest care. 
8. We shall now consider the experiments concerning sodium. 
The high importance of this research with respect to the question 
which occupies us, may be characterized by the following four points: 
a. The previous thermal history of the pure metal was strictly 
defined. 
b. Each value given for the ¢rwe specific heat is the mean ot 
4 or 6 independent determinations which were carried out under 
varying conditions (change of the quantity of electric energy supplied). 
As the tables (I and II) show, the agreement of the measurements 
is perfect. 
c. The determinations have been carried out with the solid metal 
from 0° up to the melting point. 
d. The authors have exclusively taken the standpoint of ex- 
perimental physicists, giving their quantitative results without any 
commentary. 
9. Concerning the item a the following may be pointed out. The 
authors had found that the true specifie heat of molten sodium can 
be reproduced with great accuracy, even if the previous heat treat- 
ment of the molten metal is changed within wide limits. The contrary 
occurs with the solid metal: discrepancies of 2 per cent at the same 
temperature were found in their early experiments. Referring to this 
result they say: “The importance of this point was not sufficiently 
realised in the early determinations and a large number of otherwise 
excellent experiments have been rendered worthless through lack of 
attention to the precise nature of the previous heat treatment.” 
The metal used in the final experiments was prepared as follows: 
«“ Annealed’. (Table I): The rate of cooling from the liquid state 
was less than 4° per hour, which was the rate of fall of the bath 
from 100° to 86°. 
“Quenched”’ (Table II): The metal was heated in an oil bath to 
130° and then rapidly transferred to a vessel of ice-cold water. 
The metal was enclosed in a case of copper of special form. The 
determinations with the quenched metal were made starting from 
the lowest temperature (0° C.) and progressing in steps up to 95°. 
