252 



MAJOR A. E. OXLEY ON THE INFLUENCE OF MOLECULAR 



isotropic mass (i.e., as viewed in bulk) whereas in a crystalline medium the mass will 

 be seolotropic. 



In Part III. evidence was brought forward showing that in the case of 

 diamagnetic media the local intensity of magnetizatio.n I is of the order 100, while the 

 local molecular field H c between the molecules is of the order 10 7 gauss. The energy 

 of the molecular configuration of the crystalline medium (over and above that due to 



Fig. IA. 



the molecular configuration in the liquid state) or of the gel at low temperatures, will 

 therefore be of the order J. H c . I = 10 9 ergs per unit volume* and the internal stress 

 10 9 dynes per square centimetre, or 1000 atmospheres approximately. For wrought 

 iron the energy per unit volume will be 



.H C .I = xG'5xl0 6 xl700 = 5'5 x 10 9 ergs 



and the internal stress about 5500 atmospheres. 



In nickel the intrinsic pressure is I'4xl0 9 dynes per square centimetre or 1400 

 atmospheres; in cobalt 4'4x 10 9 dynes per square centimetre or 4400 atmospheres, in 

 cast iron 4 x 10 9 dynes per square centimetre or 4000 atmospheres. These internal 

 stresses are a measure of the forces binding the molecules together and should give 

 an estimate of the ultimate tensile strength or tenacity of the medium. Moreover 

 the tenacities of ferro-magnetic, paramagnetic and diamagnetic media should be 

 roughly of the same order. That this is so is seen from the following values! : 



Material. Tenacit ^ 



(dynes per square centimetre). 



5-0-G'O xlO 9 



Ferro-magnetic 



Iron, (wire) 



Iron, wrought 



Iron, cast 



Nickel (wire) 



Mild steel (0"2 per cent, carbon) 



High carbon steel 



-Nickel steel (5 per cent.) .... 



* This,' as we have seen in Part III., p. 93, is compatible with the values of the latent heat of fusion of 

 diamagnetic crystalline media. See also infra, pp. 253-4, p. 256. 

 t KAYE and LABY, ' Physical and Chemical Constants,' 1918, p. 28. 



2-9-4-5 x 10* 

 l'2-r9xlO 

 5'3 xlO 9 

 4-3-4-9 xlO 9 

 7-0-77 xlO 9 

 6'2 xlO 9 



