RICHARDS. — SIGNIFICANCE OP CHANGING ATOMIC VOLUME. 17 



atomic distortion would accompany chemical union, and the heat of the 

 reaction would be the outcome of the resulting decrease of internal 

 energy. Atomic volume and atomic compressibility might limit the 

 possibility of distortion ; hence would arise a possible explanation for 

 quantivalence, stereochemistry, and crystal form. Many other proper- 

 ties of material, too numerous to mention, seem to be explicable in a 

 similar way. 



It would be unreasonable to expect the hypothesis thus briefly de- 

 scribed to correspond to all known facts. No hypothesis has ever been 

 proposed which is wholly satisfactory ; our knowledge is incommensurate 

 with the possibilities involved. If, however, a given theory is found to 

 explain some relationships better than other hypotheses, it may be of 

 service in suggesting new experimental research. Such a service is of 

 course the best one which a hypothesis can perform. 



The idea discussed above has been already applied in plausible fashion 

 to a wide range of chemical and physical phenomena. If future experi- 

 mentation to be carried on here seems to warrant it, these applications 

 may form the subject of another communication. 



The object of the present paper may be summed up in a few words, as 

 follows : It is pointed out that changing atomic volume may be used as 

 an approximate measure of the pressure which causes it, and therefore 

 of the affinity which causes the pressure. Some of the difficulties in 

 the way of exact interpretation are pointed out, and hints are given 

 as to possible modes of overcoming the difficulties. 



The chief outcome of the paper is the following postulate : The atomic 

 volume is not constant, but a function of pressure and temperature, and 

 probably of electric stress. 



In this connection it is pointed out that chemical affinity is possibly a 

 reciprocal function of mass. 



To explain these and many other facts, a modification of the atomic 

 hypothesis is tentatively proposed which contends that we have no right 

 to disregard the compressible environments around the centres of gravity 

 and affinity. 



Cambridge, Mass. 



