903 



tioiis again raised tlie idea that the distance of" the molecules in a 

 paramagnetic substance certainly has an influence upon the deviations 

 from Curik's law. Theii- investigation of oxygen of more than 10(» 

 times the normal density (Coram. N". 134r/ April 1913) demonstrated 

 more specially that the susceptibility foi' gaseous oxygen can be 

 represented down to — 130° C. with Curie's constant, which holds 

 for the ordinary temperature, which indicated the possibility that 

 this might still be the case at — 183° C. This gave fresh support 

 to what they added at the end of tiieir paper of Jan. 1913 (Comm. 

 N". 132g), showing the desirability of experiments upon the question, 

 whether the bringing of the molecules (or atoms) of a paramagnetic 

 substance to a greater distance from each other, influences in itself 

 the deviations from Curie's law, and pointing out the importance 

 of the continuation of our experiments with li(|ui(l mixtures of oxygen 

 and nitrogen. ^) 



Before we could at last begin these experiments in 1913 the 

 importance of them was increased by yet another circumstance. 

 Besides the hypotheses considered in the above mentioned article, 

 hypotheses of- another kind arose '"). 



With the former hypotheses, we do not interfere with the law of 

 equi partition, but assume either polymerisation, as in the above case, 

 or a subsiduary potential energy, a '•molecular" lield, the magnitude 

 of which is determined, not only by the lield, but also by the amount 

 of one-sidedness of the direction of the molecular magnetic axes 

 (Weiss and Foï;x, Kamerlingh Onnes and Oosterhuis) ''). In the new 

 type (Oosterhuis, Kehisom) on the other hand a distribution of energy 



^) Recently, Weiss {0. R. Dec. 1913) in deducing the distance law for the 

 molecular field in feiromagnelic substances (comp. § 4 this Comm.) points out the 

 importance of investigations of the same miterial at different densities. See also 

 G. FoËx, Arch. d. Sc. phys. et natur. Geneve (4) XXXV. 1913. 



~) As had been partly the case with tlie hypotheses of tfie first l\ind, so also 

 those of tlic new Icind were partly suggested by our former magnetic investigations. 



3) The tiypotliesis, that tlie resultant magnetic moment of the molecufe changes, 

 can be introduced in two different ways. In the first place, by assuming polyme- 

 risation, as mentioned above. In the second place by supposing that the change 

 takes place exclusively within the molecule itself. By continuous change of this 

 sort of course every deviation from Curie's law may be explained, in that case 

 there can be no question of decision between the above mentioned types of theory. 

 The supposition referred to seems less acceptable also for this reason that in the 

 cases in which Weiss was led to assume a change in the molecular moment, this 

 was always a discontinuous alteration (l)y changes in the number of magnetons) 

 and one wliich took place in all the molecules at once, while for the rest the 

 moment within a definite temperature zone did not undergo any change. 



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I'roctHd.i.gs Royal Acad. AiLsleruaui Vol. XVI 



