82 



HARRY C. JONES 



It is thus obvious that if we are ever to have a really exact 

 science of chemistry, geology or biology, even as we have a science 

 of phj^sics today, we must first know the condition and properties 

 of matter in that state which gives us these sciences. 



The importance of the generalizations of Van't Hoff and Arrhe- 

 nius as to the nature of solution and the relations between solu- 

 tions and gases for the development of a real science of chemistry, 

 in contradistinction to a heterogeneous mass of more or less dis- 

 connected facts, cannot easily be overestimated. 



The announcement of these generalizations in 1887 marked a 

 new epoch in the history of chemistry, and the beginning of what 

 we may fairly call a real science of chen^istr3^ From 1887 to the 

 present, general chemistry has made more progress towards becom- 

 ing a branch of really exact science than in the entire century which 

 elapsed prior to 1887; and these generalizations as to the nature 

 of solutions came as the result of Van't Hoff comparing Pfeffer's 

 measurements of osmotic pressure with the gas pressure of gases. 

 This alone would suffice to show the fundamental significance of 

 osmotic pressure for the development of general chemistry. 



In making the above statement in reference to the enormous 

 strides that scientific chemistry has taken since 1887, I am not 

 unmindful of the fact that the law of mass action was discovered 

 and its discovery published in 1868, but the law of mass action 

 without the work herein discussed on the nature of solution was 

 comparatively barren. Indeed, it was this same Van't Hoff who 

 first applied successfully the law of mass action to chemical reac- 

 tions, and this, after he had shown the inherent relation between 

 solutions and gases. 



It is not quite fair to leave the subject of the bearing of osmotic 

 pressure on the theory of solutions, without saying a few words 

 at least with reference to concentrated solutions, especially of 

 electrolytes. 



The theory of Arrhenius, which it will be remembered was pro- 

 posed to account for the abnormally great osmotic pressure of 

 electrolytes, was really a theory of "ideal" or "very dilute" solu- 

 tions. It not only did not apply to concentrated solutions, but 

 not even to those concentrations with which we actually work in 



