Januart 14, 1910] 



SCIENCE 



43 



ready mentioned. It is quite unnecessary 

 to rehearse here the great activity that has 

 resulted in the study of dilute solutions 

 during the last two decades as a direct 

 consequence of the theories of van't Hoff 

 and Arrhenius. The pages of the history 

 of chemistry that record this experimental 

 work on dilute solutions will ever main- 

 tain their brilliant luster, for they reflect 

 the enthusiastic efforts of scores of active 

 young hands and minds that were urged on 

 by a most inspiring leader, an able teacher 

 and experimenter, and a most lovable man 

 — Wilhelm Ostwald. Without him the 

 theories of van 't Hoff and Arrhenius would 

 scarcely have gained a foothold. 



But excellent as were many of the ex- 

 perimental acquisitions that were thus ob- 

 tained as a result of these working hy- 

 potheses, time has shown that the latter 

 have long since served their purpose, and 

 that mere phj'^sical conceptions of solutions 

 are untenable as an explanation of the 

 phenomena actually observed. Further- 

 more, a theory which applies merely to 

 very dilute solutions, and then only in an 

 imperfect way, is quite untenable in the 

 long run, even as a working hypothesis. 

 It is not my purpose to enter upon a dis- 

 cussion of the numerous experimental re- 

 searches which have made the theories of 

 van't Hoff and Arrhenius untenable. 

 These investigations have been published 

 at various times during the last decade, 

 and I have dwelt upon them in detail on 

 previous occasions. It is quite safe to as- 

 sume that they are sufficiently well known 

 to all. Moreover, I frankly confess that I 

 am glad to escape the task of recounting 

 again the weaknesses of these views of so- 

 lutions as exhibited by experimental facts, 

 for in my younger days I was quite en- 

 thused with these hypotheses, and it was to 

 me a great disappointment to find later 

 that they were contradicted by so many 

 experimental truths. It is rather my pur- 



pose to point out the direction in which 

 experimental investigations made thus far 

 have led us, and to attempt to indicate the 

 line of attack which must be followed to 

 insure success in the future, so far as this 

 can at present be foreseen. 



The data collected since 1887 in studying 

 the various properties of solutions, though 

 frequently gathered with the aid of the 

 physical hypotheses already named, have 

 nevertheless gradually and unerringly 

 demonstrated that the chemical view of 

 solutions is far nearer to the truth, than is 

 the idea that a solution is a mere physical 

 mixture. In this connection permit me to 

 call attention to a few experimental illus- 

 trations. 



When antimony trichloride and camphor 

 are brought together the two solids liquefy 

 each other, forming a thick syrupy solu- 

 tion, the proportions of the two ingredi- 

 ents of which may be varied within cer- 

 tain limits. Antimony trichloride and 

 chloral hydrate similarly liquefy each other, 

 though less readily. Again, camphor and 

 chloral hydrate when in intimate contact 

 with each other form a liquid. If now 

 cane sugar or paraffine be treated with 

 antimony trichloride or with camphor or 

 chloral hydrate no change will be observed. 

 The question arises, why do antimony tri- 

 chloride and camphor liquefy each other 

 and cane sugar and camphor not? It is 

 perfectly clear that all that we can say is 

 that this is because of the specific nature 

 of the substances themselves. In other 

 words, antimony trichloride and camphor 

 liquefy each other and sugar and camphor 

 do not for reasons that are similar to those 

 which we give as to why charcoal will 

 burn and platinum will not. We may say 

 that the mutual attraction, i. e., the affinity 

 of antimony trichloride for camphor, is 

 sufiicient to overcome their cohesions, and 

 so they unite and form the solution. Now 

 as to whether the antimony trichloride dis- 



