Nature of Solutions. 433 



tractions also are well -worth attention. They are deduced 

 from the densities, but form a figure totally unlike the density - 

 curve (fig. 1) ; and the first differential obtained from them 

 is also totally unlike that from the densities. Yet the second 

 differential figures in the two cases exhibit a similarity of the 

 closest description, not only in general appearance, but in 

 the inclination of almost every line constituting them, as well 

 as in the position of the changes which they show. 



Prof. Arrhenius attempts to dismiss the argument based on 

 the concordance of my results from independent sources, by 

 stating " that Mr. Pickering with his multitudinous arbitrary 

 constants can fix the points 'where the breaks occur' just where 

 he chooses." Had Prof. Arrhenius waited to see my results 

 before he attacked them he would have found that, so far from 

 working with " multitudinous arbitrary constants," I worked 

 with no constants at all*; and he would also have found that 

 an attempt to place the breaks by means of constants, or drawn 

 curves, at points otber than those at which they really occur 

 led to a signal failure, even when the attempt was made on a 

 portion of the density-curve where the true breaks or changes 

 of curvature were but feebly marked (see p. 78, loc. cit.). 



The multiplicity of the hydrates as well as the complexity 

 of the highest ones (containing as much as 5000 H 2 0) may 

 no doubt prove a stumbling block to others as well as to Prof. 

 Arrhenius. But till we have gained some slight knowledge 

 of the constitution of solutions, it is surely well not to turn 

 our backs on any evidence which may be forthcoming, and 

 brand it as a reductio ad absurdum before it is produced. 

 Organic chemistry would be non-existent had it met with 

 such a reception. 



Prof. Arrhenius's attack reaches a climax when he states 

 that u Mr. Pickering has deduced from the specific gravity 

 quite different hydrates from Mendeleeff, and from the elec- 

 tric conductivity quite different hydrates from Crompton." 

 This statement is certainly a most unfortunate one ; for, 

 though I altogether disagree with Mendeleeff's views as to 

 the nature of the density first differential, and though I think 

 that Crompton's conclusions were scarcely justified by the 



elevation, with definite changes of curvature (p. 34). It is obvious that 

 the highest or lowest point in a curvilinear figure may occur in the middle 

 of the most regular portion of it, and such points have nothing to do with 

 the changes of curvature here dealt with. 



* I prefer imagining that Prof. Arrhenius really did think that I 

 worked by fitting equations with arbitrary constants on to my curves; 

 but it is rather difficult to reconcile such a view with his previous 

 remarks. 



