290 MAGNETISM 



A series of determinations of % f' or oxygen \\a* made at 

 temperatures rising from 20 C. to 450 C., and it \\as found that 

 if T is the absolute temperature, 



33700 1 



* - To*~ T' 



Hence x is independent of the density, and is constant at constant 

 temperature. 



If KO and p are the susceptibility and density of oxygen, 



33700 ^ 



' T" 



Since the pressure of oxygen in air is 0'2 of the whole, is 

 density is 0'2 of the density of oxygen at atmospheric- pressure. 

 Neglecting the nitrogen, the value of * a , the susceptibility ot air. is 



where p is now the density of oxygen at Atmospheric preun . 

 Dividing by the density of air p^ v 



_6740 1 . 16 

 " 10 ' T 14-43 



_7470 1 



= 10^ ' T 



In convctin^ for air displaced ue require K m . A -sure 



to be 760 mm., then, for oxygen a 



00143x273 

 Po= 



whence /c.=640 . * 



' 



The value of ^ was first determined for a num 

 bodies, and it was found to be constant for each with fields \ a i \ ini; 

 from 50 to 1350. With the exception of bismuth and autiniony 

 the value did not vary when the temperature was raised in M un- 

 cases up to 500 C. 



\Yith bismuth and antimony there was a great decrease as 



* Curie gives 7830 instead of 7470, and 2760 instead of 2640. 



