467 



think, it may be still regarded as a confirmation of' the principal 

 features of the considerations of this paper. The divergences may 

 then be attributed to the approximating character of some of the 

 special assumptions of §§ 2 and 3. 



If the assumptions made in this paper concerning the molecular 

 rotational energy are adopted as being in the main right, the results 

 obtained here may be regarded at the same time as a valuable 

 confirmation of Weiss's theory regarding the molecular field. 



It deserves notice that in the assumption of a zero-point energy 

 the spontaneous magnetization at the absolute zero, (7„ , does not 

 coincide with the "absolute saturation magnetization'' »fi, for which 

 all magnetic moments are imagined to be directed parallel to each 

 other. With the values of <9„ given above one finds 



for magnetite — = 0.906 



„ nickel — = 0.346. 



If these assumptions correspond to reality, this fact has to be 

 taken into account in calculating the molecular magnetic moments 

 from the saturation magnetization at low temperatures. With the 

 above data one finds, taking the values for the saturation magne- 

 tisation ^) at low temperatures from Weiss and Kamerlingh Onnes, 

 Comm. N". 114, and applying the correction for dilatation as indicated 

 there, for the magnetic moment of a gramme-molecule, resp. a 

 gramme-atom : for magnetite 24402, for nickel ') 9734. Neither of 

 these is approximately a whole multiple of the gramme-magneton 

 1123.5 adopted by Weiss. However, before somewhat definite results 

 can be obtained regarding this point the further data concerning 

 the absolute values of the saturation magnetization, particularly for 

 magnetite, which Weiss has announced -), must be awaited, and also 

 calculations such as have been made for magnetite and nickel in 

 this communication, have to be carried out for other substances 

 (particularly for iron and cobalt). 



1) It is assumed that nothing particular occurs in the saturation magnetization 

 between the temperatures of liquid hydrogen and the absolute zero (cf. Comm. 

 N». 114 § lb). 



2) This number is less -reliable in consequence of the agreement between 

 observation and calculation being less close for nickel, particularly on the side 

 of the low temperatures (cf. also this Communication 11 p. 470 note 2). 



■i) For instance Comm. N». 114 (Febr. 191 0\ p 769 note 1. 



30" 



