919 

 TABLE XIV. 



We found the same in § 1^0 for manganese sulphate, and in § 11 

 we came to the conclusion that the decrease of A might be the 

 consequence of an increase in the distance of the paramagnetic 

 constituents of the salt. Finally we drew attention to the fact that 

 the transition of oxygen from the gaseous to the liquid form might 

 be accompanied by a cliange in A. Pekrier and Kaimerlingh Onnes 

 have now demonstrated that A decreases with the dilution of oxygen 

 with nitrogen, and that the change of A with the density, which 

 must be assumed to find for licjuid oxygen at all temperatures [with 

 the help of the ^pUqr corresponding to the liquid density (>/jy 7^] from 



the same number of magnetons as in the gas at ordinary temperature, 



agrees well with the change of A with the distance of the molecules, 



which is found from the dilution of oxygen with nitrogen. Bv this 



it has become evident that if A is the consequence of the existence 



of a molecular field, this field decreases when the molecules are 



brought to a greater distance from each other, and soon, at molecular 



1 

 concentrations ot about , is no longer perceptible. 



In ferric alum, the distance of the i^Vatoms is of the same order 

 as that at which the molecular field of the oxygen molecules in 

 the solution of oxygen and nitrogen disappeared in Kamerlingh Onnrs 

 and Perrier's experiments. That this substance conforms to Curie's 

 law as far down as the freezing-point of hydrogen, may therefore 

 be due to the atoms of iron, at the atomic concentration in this 

 substance, being at a distance which permits them to behave like 



59 



Proceedings Royal Acad. Amsterdam. Vol. XVI. 



