393 



where /? is a gas constant, equal to 1.98 gram calories, for Pb a = 58, 

 6 = 7.8 X 10-^ 



In the following tables (see p. 431) the values of atomic heats 

 of lead and silver at various temperatures are recorded. 



Lead (atomic heat). 



Dewar's value at about 50' abs. = 4.96 



Silver (atomic heat). 



64° 



84° 

 86° 



3.72 

 4.43 

 4.40 



3.61 

 4.44 

 4.50 



Dewar's value at 50° abs. = 2.62. 



Though Nkknst's, Einstein's and Gku'fiths' values agree with each 

 other, Dewar's values are divergent owing to a large range of 

 temperature. 



Griffiths and Griffiths have calculated the following values of 

 the atomic heats at —273° C, Al := 3.54, Fe = 0.73; Cu = 4.73, 

 Zn = 4.294. Ag= 5.378, Od = 4.95, Sn =: 4.997, Pb = 4.527. 



These figures also do not agree with the statement of Dkwar 

 that atomic heats of elements between the boiling points of liquid 

 hydrogen and helium would be all very small and nearly constant. 

 Evidently Dewar's data show the mean atomic heat between his 

 experimental range of temperature. 



Since the product of atomic weight and specific heat at the ordinary 

 temperature is very nearly constant, if we plot the atomic heats at 

 the ordinary temperature against the atomic weights, we shall get a 

 straight line parallel to the axis representing the atomic weights. 

 On the other hand by plotting the specific heats of elements at the 

 ordinary temperature against their atomic weights, very nearly a 

 rectangular hyperbola is obtained, since the product of specific heat 

 and atomic weight is constant. 



This non-periodic curve is quite unique amongst the physical 



