138 

 Results. 



THE ROYAL SOCIETY OF CANADA 



Table IV. 



GIVING THE OSMOTIC PRESSURES OBSERVED IN TUBES (1) AND (2) AND THE NEGATIVE 

 PRESSURES OBSERVED IN TUBE (3.) 



Depth of soil columns (1) 7-5 cms., (2) 8-5 cms., (3) 5-5 cms. 

 Electrical resistance of soil solutions (1) 70 ohms, (2) 85 ohms, (3) 

 80 ohms, of -02N. KC1 solution 270 ohms at 18°C. 



Conclusions. 

 Part I. 



Using a concentrated soil solution as solution and a column of 

 soil approximately 2-5 inches deep as semi-permeable membrane we 

 have observed an osmotic pressure equal to the pressure exerted by a 

 column of water 11-5 feet high. 



Part II. 



(1) The results indicate that the pressures observed are not due 

 to the swelling of the soil column. 



(2) They indicate also that the pressures observed are due to 

 osmosis, as follows: (a) the semi-permeable membranes used in in- 

 vestigations on osmotic pressure are colloids; (b) there is strong 

 evidence that the action of semi-permeable membranes is one of un- 

 equal absorption. One liquid is absorbed more readily than the other 

 and the movement is toward the liquid least absorbed. The soil 

 we have been using as a semi-permeable membrane resembles the 

 ordinary semi-permeable membranes in both ways: (a) it is quite 

 probable that it is in a colloidal state; (b) it absorbs water more readily 

 than it does a soil solution and the movement is toward the liquid 

 least absorbed, namely, toward the soil solution. 



