﻿500 On the Heterodyne Beat Method. 



The values in the Tabellen for K m are 81 x 10' 



101 x 10" 6 , 



and 82 x 10~ 6 c.g.s., while Theodorides* gives 97*9 x 10~ 6 c.g.s. 

 The present result thus indicates that the lower values are 

 the more accurate. 



Summary oj Results. 

 The results obtained are grouped together in Table XL 



Table XI. 



Substance. 



Ferric Chloride, FeCl 2 . 



Ferrous Sulphate, 



FeS0 4 ,7H 2 0. 



Ferrous Ammonium Sul- 

 phate, FeS0 4 . (NH 4 ) 2 

 S0 4 , 6H 2 0. 



Nickel Chloride, NiCl 2 . 



Nickel Sulphate, 



NiS0 4 ,7H 2 0. 



Cobalt Sulphate, 



CoS0 4 ,7H 2 0. 



Cobalt Chloride, CoCl 2 . 



Form in 

 which tested. 



Solution 



Crystals and 

 Powder. 



Crystals 



Solution 



Crystals 



Crystals and 

 Powder. 



Solution 



Mass susceptibility 

 of water-free salt. 



90-7xicr 6 c.g.s. 



74-0xl0 _6 cg.s. 

 41-lxl0- 6c -g- 8 - 



39-5xl0~ bc -g- s - 

 29 9 X10 -6 <-•■£•*• 



619xl0- 6 cg.s. 

 81-3xl0- 6 cgs. 



Temp. C. 



15° 

 16° 



16° 



15° 

 16° 



16° 



20° 



Summary. 



The precautions necessary for steadiness in the heterodyne 

 beat method are described, employing frequencies greater 

 than 10 5 per second, and it is shown that under normal 

 laboratory conditions a beat note can be obtained perfectly 

 steady for large periods. 



Some applications of the method to physical measurements 

 are then considered, the changes in frequency being conse- 

 quent on changes in the inductance of one of the circuits. 

 These latter changes were brought about by inserting a 

 specimen within the coil, and were of two kinds : — 



(i.) An eddy current effect, the nature of which was 

 examined for cylindrical specimens of different materials. 



(ii.) In the case of magnetic substances, a susceptibility 

 effect. This latter variation was employed to measure the 

 magnetic susceptibility of several salts at frequencies ranging 



* Theodorides, he. cit. 



