428 
certaln deviations and these show disiinct periodicity, the genera t tendency 
being towards increasing atomic heat loith increasing atomic iveight. 
Schimpf (Zeit. Phys. Chem. 1810. 71 , 257) has determined the 
specific heats of many elements at various temperatures (e.g. — 150°, 
— 100\ —50° etc.). ' 
From his work he concludes that the atomic heats diverge in a 
marked way as the temperature falls. whilst conversely a rise of 
temperature produces, as is well known, a marked convergence 
towards a fixed value for all elements. 
Evidently, it is seen from the above investigations, that there are 
distinct indications showing the period nature of atomic heats at 
low temperatures. 
Very recently a decided advance in this direclion was made by 
Dewar [Proc. Roy. Soc. A. Vol. 89 p. 158 (1913)]. He determined 
the specific heats of 53 elements between the boiling points of liquid 
nitrogen and hydrogen at about 50° absolute. 
When the atomic heats are plotted in terms of their atomic 
weights they reveal defmitely a periodic variation resembling gener- 
ally the well-known Lothar Meyer atomic volume curve. 
The author concludes, that if experiments were similarly made 
between the boiling points of hydrogen and helium then in all proba- 
bility the atomic heats would be all very small and nearly constant. 
However interesting these results may be there is a great difticulty 
in these investigations. The temperature range is very high with 
these workers. In the case of Richards of Jackson’s experiments it 
was about 200° and in thé case of Dewar’s it was 57°.5. 
From these works only the mean specific heat between so large 
a range of temperature is available and not the specific heats at a 
fixed temperature. Since there is a marked variation of specific 
heats with temperature, the results obtained in experiments carried 
on with large range of temperature lose much of their significance. 
Nernst and his pupils have determined the specific heats at low 
temperatures (Jour. de Phys. tome IX, 1910, p. 721); E. H. Grif- 
fiths and E. Griffiths have also attacked the same problem (Phil. 
Trans. 1913 A 213 , 119.). These experiments are advantageous, 
since the temperature range is very small. In Nernst’s experiments 
it is only 2°. 7 C. It is well known that the atomic heats of 
lements can be calculated from Einstein’s formula 
C = 3R-dl -ujtI 
