88 THE DIFFUSION OF GASES. 



general decreases rapidly with the strength of the solution, /. e., the physical 

 pores of the solvent are invariably at least virtually stopped up by the 

 solute. But the decrease of diflusivity k occurs at a rapidly retarded rate 

 with the strength of solution, so that the chief effect is already patent for 

 solutions lying within 5 to lo per cent strength. The water of the solvent 

 should therefore be very pure. 



Different solutions, moreover, behave quite differently. Thus the al- 

 kalis KCl and NaCl are more powerful in decreasing the diffusivity of a gas 

 than the chlorides or alkaline earths BaClg and CaClj, at least so far as the data 

 now available allow an assertion. One w^ould naturally anticipate some 

 result here with a bearing on the periodic law, but the time for this is not 

 yet at hand, and the conditions are liable to be variously complicated. 

 Thus the continued dilution of a concentrated solution does not necessarily 

 imply the continued decrease of the diffusivity of the gas through it. The 

 table shows instances, e. g., CaClj, K2SO4, in which the dilute solutions 

 show lower diffusion coefficients than the more concentrated solutions. 

 One would naturally attribute such a result (if indefinitely substantiated), 

 to the formation of hydrates at different favorable strengths of solution, by 

 which the structure of the solution is fundamentally modified. 



In conclusion, therefore, the present experiments, in spite of all the labor 

 and patience spent upon them, have done no more than enhance the interest 

 of the subject in a very real degree. That the internal structure of the 

 liquid may in a measure be explored in this way admits of no doubt; but 

 the path of the explorer has proved very much more arduous than the 

 initial trials promised. The work will nevertheless be continued in various 

 directions. 



