6 Mr. J. J. Coleman on Liquid Diffusion. 



The diffusion of chloric acid against sulphuric acid I had to 

 make specially* ; the other figures are from the tables and 

 data before given, and the atomic volumes are quoted from 

 Ira Remsen's recent book, the ' Principles of Theoretical 

 Chemistry.' 



Here then is evidence that, given a number of elements the 

 atomic weights of which do not differ widely, the diffusibility 

 will vary in some sort of proportion to the atomic or mole- 

 cular volume, which latter, indeed, may be to some extent 

 regulated by the energy of the molecules. 



Mendelejeff's fourth horizontal series commences with K 

 and Ca, the molecular volumes and diffusibilities of the chlo- 

 rides being thus : — 



K 2 C1 2 . CaCl 2 . 



Molecular volume ... 74 44 



Diffusibility 41 27 



Here again diffusibility corresponds with the larger molecular 

 volume. 



The fifth series commences with copper and zinc, the mole- 

 cular volume of the sulphates being exactly equal and the 

 diffusibility nearly equal. 



The sixth series commences with rubidium and strontium, 

 the metal rubidium possessing, with the exception of caesium, 

 the largest atomic volume of any metal yet discovered. 



Graham has already shown that chloride of strontium is 

 much less diffusible than chloride of potassium. If, there- 

 fore, chloride of rubidium be as diffusible as chloride of potas- 

 sium, then the diffusibility of chloride of rubidium will be 

 greater than that of chloride of strontium. This has been 

 proved to be the case by the following diffusions I have 

 recently made. Chloride of rubidium, chloride of potassium, 

 and chloride of sodium were diffused for 10 days at 12° C. in 

 the apparatus figured on Plate I. 



* By new method of diffusion : — 



58 per cent, sulphuric acid rose 25 millim. in 7 days. 



12 





75 





V 



70 per cent. 



chloric acid rose 



25 



a 



» 



is ;; 





50 



75 







temperature 12° Cent. 



