14 



Mr Vegard, On the Free Pressure in Osmosis. 



ments corresponding to a considerable difference in the maximum 

 electric resistance of the membrane. Before each experiment the 

 cell was electrolysed after which it was placed for about thirty 

 hours in distilled water in order to remove possible substances 

 soluble in water. The measurements gave the following result : 



Table I. 



Determinations of Osmotic Velocities. 



8. The velocities were measured with the osmometer earlier 

 described for some aqueous solutions of cane sugar and no pressure 

 was applied on the solution. The measurements including also 

 the determination of the frictional resistance in Exp. 2 were 

 carried out as quickly as possible in succession and in the order 

 of increasing concentrations. The membrane was not electrolysed 

 between each trial. Thus it was secured that the properties of 

 the membrane were kept as nearly as possible the same under the 

 whole series of measurements. The results are given in the 

 following table. 



The temperature was kept at 15° C. which very nearly was 

 the temperature of the room. 



The velocity is here given in an arbitrary unit as the number 

 of mm. which the water level in the capillary from the cell* 

 changes in one hour. For the sake of comparison with other 

 experiments we shall find how this unit is connected to the 

 absolute unit. To find this we must know the area of the 

 membrane (0) and the inner diameter (d) of the capillary. For 

 the apparatus used in Cambridge 0= 17'Ocm,^ (very nearly) and 



* See description of apparatus, loc. cit. p. 248. 



