CONSTITUTION AND TEMPEEATUEE ON MAGNETIC SUSCEPTIBILITY. 255 



determine the value of the applied pressure corresponding to the maximum of the closed 

 area on the 3, p diagram. We cannot expect this method to give us anything but an 

 approximate value of IT because the extrapolation beyond laboratory pressures is 

 considerable, but the results of the calculation are suggestive. 



The relations between the temperature of fusion (&) and applied pressure (p) in 

 atmospheres, for the substances* here referred to are taken from ' Kristallisieren und 

 Schmelzen' by G. TAMMANN, Leipzig, 1903, p. 204, et seq. 



For water TAMMANN found 



S--22 = 0'00438 . (p-2200)-77 x lO" 8 . (p-2200) 2 . 



r)y 



Differentiating and equating to zero, 



^ = Q'00438-154 x I 0~ 8 . (?J-2200) = 0, 

 0-00438 + 154 x 2200 xlO- 8 



or 



Benzophenone 



154 xlO- 8 

 = 5000 atmospheres = 5 x 10 9 dynes/square centimetre. 



= 48'11 + 0'02757p-0'00000136 . p\ 



7f\ 

 Differentiating and equating to zero we find the intrinsic pressure 



A cetophenone 



Aniline 



Nitrobenzene 



Xylene 



77 = 10,000 atmospheres. 



9- = 19'2 + 0-0235p-0-00000152. p 2 

 IT = 7700 atmospheres. 



$r = -61 + 0'0203p-0-000001 12. p 2 

 TT == 9000 atmospheres. 



0-02344p-0-00000116.p 1! 

 TT= 10,000 atmospheres. 



3- = 13-2 + 0-03438J9-0-00000171 . p* 

 TT= 10,000 atmospheres. 



TT = 7100 atmospheres. 



* Most of these substances show a change of diamagnetic susceptibility on crystallization. See Part I., 

 pp. 120-131 ; Part III., pp. 96-97. 



VOL. CCXX. A. 2 N 



