on Mixtures of Alcohol and WaUr. 7 



The above tables of results are typical of those obtained 

 from experiments with other solutions and with other cells. 

 Considering the results in Table I., we find a rapid rise of 

 pressure when the cell is surrounded by water. The normal 

 rise of pressure is spoken of as u permanent "" for the purposes 

 of this paper. 



When placed in alcohol, cell (3 showed an increase of 

 pressure, the gauge rising through 20*5 mm. in 48 minutes. 

 There was no further rise. The level then fell steadily. The 

 above rise was " temporary " : this fall is u permanent/'' that 

 is, it would have continued until the liquids on both sides of 

 the membrane had the same composition, or until further 

 outflow was stopped by the difference between the internal 

 and external pressures. That this outflow was permanent in 

 this sense, and not temporary, was readily shown by repeatedly 

 opening and closing the cell while it remained in the alcohol; 

 there was always a fall of the gauge-reading. It was 

 necessary to open the cell at intervals to avoid the mercury 

 being sucked back beyond the bend of the gauge. 



In this connexion the experiment of Table IV. is important. 

 The arrangement in this case is the reverse of having the 

 solution inside and the alcohol outside. The osmotic current, 

 which in the latter was the permanent outflow, now becomes 

 a steady inflow and may be allowed to show itself over a long 

 interval of time. The rate of rise of pressure is much slower 

 than in the case when pure water is outside, as would be 

 expected. The results given in Table IV. are spread over a 

 week. Obviously, if the current can only be from the single 

 liquid to the mixture, as expressed in Pickering's account, 

 then results like those of Table IV. would be impossible. 



When the cell was placed in water after being removed 

 from the alcohol, there was a temporary fall in all cases. In 

 Table I. this fall continued for about three hours, and was 

 succeeded by a steady increase of pressure. On being placed 

 in alcohol again without relieving the internal pressure, there 

 was a temporary rise as before ; but this time the rise was 

 less. The internal pressure opposed the temporary inflow. 



The case in Table III. is slightly different. The cell was 

 first soaked in the alcohol, and then the solution was added. 

 The cell being in alcohol, there was no temporary rise ; the 

 permanent fall began at once. When placed in water, the 

 temporary fall was that usually found. 



All the experiments point to the conclusion that the water 

 tends to cross the membrane in that direction which will 

 promote its equal distribution on both sides. 



This conclusion has been put to the following severe test. 



