600 Mr. E. Vanstone on the 



and M will be the mass of the system in grams multiplied 

 by 10 21 , the square o£ the velocity o£ light. 



For one mol of a monatomic gas we should have in ergs 



H = 12-4xl0 7 T+^10- 6 T 2 . 



In the case of the electron, which may be looked upon as 

 the lightest of monatomic molecules, M may be taken as 

 approximately 1/1700. At room temperature the second 

 term of our equation would be entirely negligible, being 

 only 3*9 X 10" 6 per cent, of the first, and still be only 

 3*9 x 10 " 4 per cent, in a fixed star having a temperature of 

 30,000°. Hence at all ordinary temperatures we may expect 

 the law of the equipartition of energy to be substantially 

 exact for particles of masses as great as the electron*. 



Berkeley, Cal., 

 September 19, 1913. 



LX. The Unit-Steve Theory of Molecular Volume, A 

 Criticism. By Ernest Vanstone, M.Sc. ( Wales), Lecturer 

 in Chemistry , University of Birmingham^. 



IN 1907 a paper was published (Trans. Chem. Soc. xci. 

 p. 112, 1907) by Gervaise Le Bas, in which it was 

 shown that the ratio Molecular volume/Sum of valencies, for 

 the higher members of the homologous series of paraffin 

 hydrocarbons, was a constant, viz. 2*97. It was also stated 

 that this quantity represented the atomic volume of hydrogen 

 in this class of compound, and that the carbon atom had 

 a volume four times as large, i. e. 2*97 X 4 = 11*88. The 

 quantity 2' 9 7 was termed the unit-stere. 



Since 1907 several papers have been written by the same 

 author, the same ratio or unit-stere being used to trace con- 

 stitutive volume changes in olefines, acetylenes, esters, ethers, 

 and cyclic compounds (Phil. Mag. |~6] xiv. p. 324, 1907; 

 xvi. p. 60, 1908. Chem. News, xcviii. p. 85, 1908 ; xcix. 

 p. 206, 1909. Phil. Mag. xxvii. p. 740, 1914). An examina- 

 tion of this ratio Molecular volume/Sum of valencies reveals 

 interesting facts. 



If V = molecular volume, VV = sum of valencies, M = mole- 

 cular weight, v = specific volume, then 



Molecular volume V _ M 

 Sum of valencies "~ W ' W ' 



The ratio is thus the product of two factors, one of which is 

 the specific volume. For any homologous series of compounds 



* Compare Jiittner, loc. cit. 



f Communicated by Sir W. Ramsay, K.C.B. 



