RICHARDS. — SIGNIFICANCE OP CHANGING ATOMIC VOLUME. 603 



monatoinically as zinc does, even the strongest tie binding each atom 

 must be broken ; on the other hand the tenacity of the metal could be no 

 greater than the cohesion of the weakest tie, as has already been pointed 

 out, in the case of tin. If all the atomic ties were nearly equal in each 

 of two cases, that is, if the atoms were equally compressed on all sides, 

 tenacity and boiling point would be expected to vary in a parallel manner. 

 In a similar way the other physical properties might be discussed in rela- 

 tion to the varying intensities of cohesive and chemical attraction; but 

 the complete discussion involves more knowledge concerning the extent 

 and nature of polymerization in solids than is at present available ; hence 

 it must be postponed. 



In conclusion, it may be noted that the hypothesis of compressible 

 atoms is consistent with either of the two alternative hypotheses concern- 

 ing the ultimate nature of material — namely, the corpuscular conception 

 so popular to-day, and the hypothesis assuming the atom to be an ultimate 

 continuous although compressible aggregation. 



Moreover, it is not a necessary consequence of the facts discussed above 

 that the atom should have a very sharply defined surface, — the concen- 

 tration of its substance may increase gradually as the centre is approached. 

 On the other hand the fact that a definite volume is attained, and that 

 the compressibility decreases greatly with diminishing volume, seems to 

 prove that the distending effect increases much faster than the law of in- 

 verse squares governing the usual forms of attraction. The discussion of 

 these questions is best deferred until some of the more immediate conse- 

 quences of the hypothesis have been studied. 



Summary. 



In this paper the following conclusions, based upon new data of known 

 accuracy, are attained : — 



(1) Among compounds of lithium, sodium, potassium, chlorine, bro- 

 mine, and iodine, it is shown that in every case the compound of a more 

 compressible element is formed with a greater decrease of volume than 

 the compound of a less compressible element, other conditions being 

 equal. 



(2) From a study of data concerning the chlorides of silver, the chlo- 

 rides and bromides of zinc and cadmium, and carbon bisulphide, it is 

 shown that the more volatile the substance (i. e. the slighter its cohesive 

 attraction;, the greater is the molecular volume, other conditions being 

 equal. 



