[lynde-dupré] 



ON OSMOSIS IN SOILS 

 Table 9. 



79 



Giving the Negative Flow in each Tube in Linear Centimetres per day 

 AND THE Electrical Resistances of the Solution. 



It will be noticed that the outer Hquids had the greater concen- 

 tration and that the flow was negative in each case. It will be noticed 

 also that the inside liquids had a much higher resistance in this test 

 than they had when distilled water was used in the seventh test. 

 This indicates that in the seventh test the w^ater moved up and carried 

 salts for the soil to the inside solutions; but in this test the water 

 moved down through the soil and the soluble salts were carried from 

 the soil to the outer solutions. 



NINTH TEST. DOES CLAY SUBSOIL IN ITS NATURAL CONDITION ACT 

 ^ AS A SEMI-PERMEABLE MEMBRANE ? 



In the former tests the subsoil was settled in an artificial manner, 

 the following experiments were made with the subsoil in a more 

 natural condition. 



The moist clay subsoil was broken into small lumps and was 

 rammed into the bottom of tubes similar to those used above until the 

 depth of soil was about 2 • 5 cm. 



Four such tubes were set up as in Fig. 2. Tube (1) was filled 

 with a strong sugar solution (100 g. granulated sugar in 100 c.c. of 

 water) ; tube (2) was filled with a saturated K2SO4 solution; tube 

 (3) was filled with a medium strong soil solution; and tube (4) was 

 filled with distilled water. 



In tube (1) (sugar solution) a flow started at once and still con- 

 tinues (9 days). In tube (2) (K2SO4) a negative flow took place for 

 4 days and since then the flow has been positive (5 days). In tube 

 (3) (soil solution) a negative flow occurred for 6 days and since then 

 the flow has been positive (3 days). In tube (4) (distilled water) a 

 very strong negative flow occurred at first and it still continues but 

 it is gradually decreasing. 



