34 Dr. A. Tick on Liquid Diffusion. 



length (expressed in millimetres), the same value, viz. the above- 

 defined k, must be obtained for all three tubes. I here annex a 

 short table of the best experiments with common salt, to which I 

 have hitherto confined my attention : — 



If we take into consideration the unavoidable sources of error, 

 a nearer identity of numbers could scarcely be expected. The 

 table shows, as might be already expected from Graham's expe- 

 riments, that the value k increases with increase of temperature ; 

 probably, however, this dependence upon temperature is not a 

 simple one. On the relations of k to otlier values expressing the 

 essential properties of bodies, as, for instance, to atomic weight, 

 nothing can be said until extensive series of experiments with 

 different substances have been made. It is now of importance 

 to make the views thus obtained furnish an insight into the dif- 

 fusion of salt solutions through porous partitions. Bi'ucke* first 

 made an attempt to give a mechanical explanation to these phfe- 

 nomena. He went upon the assumption that the substance of 

 the partition attracted the particles of water more strongly than 

 the particles of salt. This assumption gained important support 

 from the experiments of Ludwigt and Cloetta J, who found that 

 the solution of salt, imbibed by an animal membrane, was richer 

 in water, and poorer in salt, than the solution in which the 

 membrane was immersed. Brackets theory, which was only 

 indeed obscurely intimated, can be more clearly determined by 

 the help of our fundamental law as follows. 



Let us imagine a cylindrical pore of the radius p, in a mem- 

 brane which is immersed in a saturated solution of a salt, and 

 let us assume with Briicke, a stronger attraction between water 

 and the molecules of the membrane, than between the latter and 

 the salt molecules ; then the density of the solution in each con- 



* Poggendoi-iF's Annalen, vol. Iviii. p. 77- 

 + Experiments on Diffusion tlirough Membranes with two Salts. 

 1851. 



1, 



iirich, 



