10 Mr. P. S. Barlow : Osmotic Experiments 



When placed in water after the above there was a temporary 

 fall of nearly 80 mm. succeeded by a large and steady rise. 



In Table V. the time required for the permanent fall to set 

 in is about four hours ; in Table VI. probably less than four 

 hours. In Table I. the fall began in a little more than half 

 an hour : in Table II. the gauge had risen and fallen again 

 below its starting point in less than four hours. In this way, 

 therefore, the temporary effects seem satisfactorily accounted 

 for, and the true explanation of Pickering's observations 

 given. 



These experiments have shown that what was claimed as a 

 "crucial" experiment in support of the hydrate (as distin- 

 guished from the dissociation) theory of solution can no 

 longer be claimed as such. Nevertheless it would not be a 

 justifiable inference to conclude that therefore a hydrate 

 theory of solution is untenable. A large amount of work has 

 been done on the properties of solutions of various solvents — 

 among other workers mention may be made of Fitzpatrick *, 

 Lincoln t, Schlundt J, H. C. Jones and Carroll §, — and 

 all goes to show that the influence of the solvent is con- 

 siderable and that some kind of complex of solvent and 

 solute is formed. Some kind of " hydrate " theory seems 

 necessary ; but in this sense it must not be regarded as 

 excluding dissociation. 



It may justly be concluded that these experiments prove 

 that the part played by the membrane in osmotic phenomena 

 is not a sieve-like one. For in the experiments where the 

 outside alcohol got its water by absorbing the aqueous vapour 

 in the air above it, the ratio of the alcohol molecules to the 

 water molecules must have been very large ; hence it is very 

 probable that each water molecule would be the centre of an 

 ao'oreorate of alcohol molecules, which is carried along with 

 it. Everything really seems to be in favour of the pure 

 alcohol getting through to produce a current from within 

 outwards. For if we consider the alcohol within the cell, it 

 has none of its molecules hampered by the aggregating 

 influence of water molecules ; and therefore on any theory 

 accepting a quasi-gaseous pressure exerted by the liquids, 

 there w T ould be a larger number of effective alcohol molecules 

 inside the cell. This w T ould lead us to anticipate an outflow 

 of alcohol from the cell ; a decrease, instead of an increase, 



* Phil. Mag-, xxiv. p. 377 (Nov. 1887). 



+ Joum. Phys. Cliem. iii. p. 457. 



X Ibid, vi. p. 159. 



§ Amer. Chem. Journ. xxxii. 6 Dec. 1904, p. 521. 



