014 



bilt flie deviations are not much greater tlian the errors of observation, 

 except for the most diluted mixture. Moreover the slight curvature 

 is in the opposite sense to all the pdrahohe for ivhich n ^ 0. The 

 observations at concentrations smaller than 0.1 indicate that the 

 molecular field then begins to change more quickly, but tiiey do 

 not justify the assertion that this is actually the case. It is therefore 

 not probable that the results can be represented by means of a 

 positive n (except for very great dilutions, for which we have not 

 a single indication); in order to elucidate this point we have also 

 constructed the curve 7^ =ƒ(<,-)' which with the same extremities 

 corresponds to » = 1, i.e. to the law that the molecular field would 

 be proportional to the square of the density or lo the inverse sixth 

 power of the mean distance of the molecules; it is obvious that this 

 bears no resemblance to the experimental curve. 



We assume therefore that the molecular field of oxygen changes 

 about proportionallg to the density^). 



This law, in the case of the appearance of a negative field 

 (assuming that this exists) for oxygen, differs totally from that at 

 which Weiss arrived, in the case of the positive molecular field with 

 alloys of ferromagnetic metals, for the dependence of X upon tiie 

 density, and from which he inferred an infiuence according to the 

 inverse sixth power of the distance, which for that reason we have 

 just referred to. fFrom our law, in tiie same way, an intluence 

 according to the inverse third power of the distance would follow). 



At present, we need not see any contradiction between these two 

 results, as the conditions for which the two laws of distance hold 

 good, are quite diiferent. This applies both to the nature of the 

 substances and to the state of aggregation in which they were 

 examined. Moreover it must be particularly borne in mind that the 

 sign for tlie molecular field is different in both cases. The part of 

 the curves referring to the change of X with the concentration, 

 which Weiss makes use of in his theory, lies entirely in positive 

 fields, the transition to negative fields is curved. We are in complete 

 ignorance as to the origin of the mysterious influences which cause 

 the phenomena ascribed to the molecular field. There is no ground 

 therefore to expect that the two fields are subject to the same law. 

 Should it be confirmed that the two kinds of molecular field de[)end 

 upon the distance of the molecules according to different laws, we 



Ï) Gf. the next paper l)y Kamerlingh Onnes and Oosterhuis, in which the 

 idea of the dependence of A on the concentration is extended to the ''atomic 

 concentration" of the paramagnetic component in crystallized compounds, in the 

 first place in those containing water of crystaUization. 



