128 RELATION TO PHYSICAL CONDITIONS 



Effect on Moisture Movements. The somewhat un- 

 usual moisture conditions in alkali soils have long been 

 observed by students of alkali. Briggs and Lapham (4) 

 investigated the effect of various soluble salts on rate of 

 capillary movements through the soil and as a result of 

 their studies came to the following conclusions: "(1) Dis- 

 solved salts in general do not increase the capillary rise of 

 soil waters; (2) neutral salts in dilute solution have prac- 

 tically no influence on the extent of capillary action; 

 (3) concentrated or saturated solutions of all salts materially 

 diminish capillary activity; (4) this effect appears to be 

 due (a) to the increased density of the solution which 

 more than offsets the increased surface tension, and (b) to 

 the resistance of a film to a tangential shearing stress which 

 retards capillary action and offers in addition a permanent 

 resistance to the movement of the solution through films, 

 thus increasing the angle of contact, or (e) to an increase 

 in the tension of the liquid-solid surface, as the concen- 

 tration is increased; (5) sodium carbonate differs from 

 neutral salts, the capillary rise being considerably greater 

 than for neutral solutions of equal concentration; (6) this 

 may be due in part to the saponification of traces of grease 

 on the surface of the soil grains through the hydrolysis 

 of the sodium carbonate, thus forming clean surfaces for 

 capillary action; (7) the same effect should consequently 

 be observed with all salts which undergo an alkaline hy- 

 drolysis, viz., potassium and sodium carbonates, borates, 

 phosphates, etc. ; (8) this action is characterized in the soil 

 tubes by indistinctness of the upper boundary of the 

 capillary column. " 



Capillarity is dependent on surface tension. Since the 

 capillarity does not seem to be greatly influenced by 

 soluble salts it seems evident, as pointed out by Davis (6), 



