ELISHA MITCHELL SCIENTIFIC JOURNAL 43 



ever more apparent than real. Inorganic chemistry, as a 

 present practiced, consists chiefly in the preparation and study 

 of certain compounds, and to a lesser extent in the study of 

 reactions, usually a qualitative study. In so far as we are 

 dealing- with single substances, all that is inorganic chemistry 

 as well as much more finds its place under one-component sys- 

 tems. The preparation of compounds involves phase separa- 

 tion by definition and is therefore included under what is 

 called physical chemistry. The study of reactions is physical 

 chemistry pure and simple. In fact, inorganic chemistry is 

 merely one part of what should be called chemistry, but 

 which unfortunately is called physical chemistry. I quite 

 appreciate that many people take physical chemistry to mean 

 the theory of dilute solutions. That is a very natural mis- 

 take which is made even by some who call themselves physical 

 chemists. If one accepts my definition of physical chemistry 

 as the science of chemistry, it is clear that it includes inor- 

 ganic chemistry and that it includes very much more than the 

 theory of dilute solutions. 



I have tried to show that the phase rule offers a satisfactory 

 basis for the classification of practically all the phenomena of 

 inorganic chemistry. For the present, we cannot include 

 much of organic chemistry any more than we can include 

 potassium chlorate, because we are dealing with passive resis- 

 tances to change in these cases. I look upon this as a tem- 

 porary limitation and I have hopes that some day it will be 

 possible to present organic chemistry as a system made up of 

 carbon, hydrogen and oxygen as the independently variable 

 components. The recent work of Sabatier and Senderens on 

 the catalytic action of nickel and copper makes the applica- 

 tion of the phase rule to organic chemistry a problem of today; 

 but the work has not }'et been done and for that reason I have 

 discussed the phase rule only in its bearing on the classifica- 

 tion of inorganic chemistry. It is now in order to ask 

 what use the phase rule has been and will be in promoting 

 research. 



