Section III., 1913. 



[105] 



Trans. R.S.C. 



On Osînosis in Soils. 



The Efficiency of the Soil Constituents as semi- 

 Permeable Membranes. 



By C. J. Lynde, Professor of Physics, and H. A. Dupré, Research 

 Assistant under the Dominion Grant for Agriculture, 

 Macdonald College, P.Q., Canada. 



Presented by Prof. H. T. Barnes, F.R.S.C. 

 (Read May 28, 1913) 



The object of the work herein described was to compare the efficien- 

 cies of the different soil constituents as semi-permeable membranes. 



The results show that the finer the particles in a soil constituent 

 the greater is the efficiency of the soil constituent as a semi-permeable 

 membrane, when used with a clay subsoil solution. 



rr—Dist. water 



Sugar sol 



Porous cup 

 with memorane 



Figure 1. Pfeffer's Apparatus. 



Before describing the experiments, we will for the sake of clearness 

 review briefly the work of Pfeffer on osmotic pressure and the work on 

 osmosis in soils carried on in the years 1911 and 1912 in the physics 

 laboratory of Macdonald College. 



In 1877 W. Pfeffer* measured the osmotic pressure of various 

 solutions and showed: — 



*Osmotische Untersuchungen, Leipzig, 1877. 

 Sec. Ill, 1913—7 



