﻿494 Mr. M. H. Belz on the Heterodyne Beat Method 



The values of p/N show that for the range of frequencies 

 used the susceptibility is constant. This was found to be 

 the case for all the substances examined. 



Formula (iii.) gives 



K* x 3-19 x 10- x (WiXi^L3 6-70 x Q-9873 



LIT 1'oZl 



131600 

 = 19-1 xl0~ 6 c.g.s. X 92430 



The mass susceptibility of the solution K m , is thus 



K m , = 19'lxl0- 6 /l-152 



= 16-53 xlO" 6 c.g.s. 



For a solution of a salt in water, the mass susceptibility is 

 given by 



where p = mass of salt per c.c, 



K m = mass susceptibility of the water-free salt, 

 K mo = susceptibility of water, which may be taken as 

 . — 0-75x 10~ 6 c.g.s. 



We thus obtain 



K w = 90'7xl0- 6 c.g.s. at 15° C. 



The values for K m determined previously by balance 

 methods are* 92 x 10" 6 , 91 x 10" 6 , 83 x 10" 6 , 92 x 10" 6 , 

 38 X LO" 6 , and 103 X 10" 6 c.g.s. with a mean value 91 x 10" 6 

 c.g.s. The present result is in good agreement, and thus 

 shows that up to a frequency of 4'03 X 10 5 per second the 

 susceptibility is not altered. 



II. Ferrous Sulphate. — Tests were made on the salt in 

 forms of crystals and powder. The crystals were good ones 

 of the monoclinic type, and on estimation proved to have 

 the composition, FeS0 4 , 7H 2 almost exactly. Equal masses 

 of crystals and powder were used, the powder being obtained 

 by grinding up the crystals in a glass mortar. The substances 

 were enclosed in glass tubes, the transference after weighing 

 being rapid to avoid absorption of water from the atmosphere. 

 The mass of each specimen was 1*00 gm. at 15° C. At this 

 temperature the density of FeS0 4j 7H 2 crystals is 1'899 gm. 

 per c.c, and hence the volume of each specimen was 0*527 c.c. 

 In the form of powder this volume occupied a length 5*6 cm., 

 while for the crystals the length was about 8 cm. 



* Landolt and Bornstein Tabellen (1912). 



