GENEEAL AND PHYSICAL CHEMISTRY NEENST. 249 



The problem, however, of reconciling experience and theory in 

 the case of some other physical properties, as successfully as in this 

 example, seems still far from solution. In general the exactness and 

 consequently the reliability of theoretical treatment have been more 

 striking in connection with the theory of corresponding states which 

 we shall now take up. 



In the theoretical consideration of natural processes, it has gener- 

 ally been considered necessary to take account only of very small 

 variations of the system under observation ; a variation of any extent 

 caused so many complex accessory phenomena that it was impossible 

 for the mind's eye to follow them. Thus in theoretical physics we 

 see the quintessence of nearly all theories represented by a differential 

 equation, that is to say, by a mathematical formula which has to do 

 with only infinitely small variations. The establishment of a differ- 

 ential equation (assuming, of course, that it can be solved) has a 

 symtomatic signification in a science, since its employment proves 

 that the region of corresponding phenomena has been carefully con- 

 sidered. It was, however, by a rare and fortunate chance that the 

 law of mass action was established in chemistry some forty years ago. 



I recall very vividly the great surprise I experienced when for 

 the first time a differential equation appeared to me in the study 

 of the speed of reaction of the saponification of ethers, especially 

 when I discovered how beautifully the integral of this equation was 

 confirmed by the facts. How many inconsistencies, how many 

 irregularities, and how many values depending on all sorts of condi- 

 tions appear at first glance in chemical phenomena ! Nevertheless 

 the law of mass action shows us that, if we disregard the secondary 

 phenomena of supersaturation and the like, if we maintain a constant 

 temperature, and if we consider a chemically homogeneous system, 

 we will have to deal with phenomena very clearly defined and calcu- 

 lable with mathematical precision. 



The law of mass action furnishes at the same time the law for 

 static and kinetic chemistry. It gives us the outlines not onlj^ for 

 the experimental investigation of chemical equilibrium but for the 

 speed of chemical reaction. Therefore I can cite as the most im- 

 portant result of the last forty years in this field the fact that not 

 only are we in possession of the laws of chemical equilibrium and 

 the speed of reaction, but above all we can classify a great many 

 experimental facts as logically following the law of mass action. 

 This law, as I have stated, is of the most general application, but 

 experience shows us that general theories are not very profitable. 

 Accurate results are never obtained except by fortunate specialization. 



Organic chemistry, characterized by the inertia of the bonding of 

 the carbon atom, furnishes a vast field for the application of kinetic 

 chemistry, while the solutions of salts, acids, and bases which are 



