iv Preface. 



The different physical behavior of free and of combined water 

 suggested to Dr. Shaeffer the desirability of studying the relative disso- 

 ciating powers of free and of combined water. This work was under- 

 taken by Mr. Ordeman. He prepared isochloric solutions of the 

 slightly hydrated salt potassium chloride, and of the strongly hydrated 

 salt calcium chloride, and used these solutions as solvents in which to 

 dissolve chlorides and measure their dissociations. The dissociation 

 of a number of salts in these solvents was measured ; and while we are 

 not yet prepared to draw any final conclusions, it seems probable that 

 "combined" water has rather less dissociating power than "free" 

 water. 



The absorption and adsorption of the slightly hydrated salt potas- 

 sium chloride by soils, is a problem of both scientific and technical 

 importance. Work has been in progress in my laboratory on this 

 problem during the past year by Mr. McCall, with the cooperation of 

 Messrs. Hildebrandt, Johnston, F. S. Holmes, and Trelease. They find 

 that a part of the potassium chloride is absorbed or combined chem- 

 ically with the soil particles, and a part is adsorbed or in a state of 

 physical union with the particles of the soil. Under certain conditions 

 the solvent may be more rapidly adsorbed than the salt. 



The results of these investigations, many of which have been carried 

 out with the aid of grants generously awarded me by the Carnegie 

 Institution of Washington, are all recorded in this publication. 



HARRY C. JONES. 

 JOHNS HOPKINS UNIVERSITY, 



June, 1915. 



