On the Cause of the Influence of Ions on the Rate of Diffusion of Water through Collodion Membranes. Ii. by Jacques Loeb

In this note it is intended to complete the proof that the influence of the concentration of electrolytes on the transport of water through a collodion membrane is similar in the case of free and of electrical endosmose. Fig. 1 gives the curves representing the influence of different concentrations of KC1, K~SO4, K3 citrate, and CaC12 upon the initial rate of diffusion of water from pure water through a collodion membrane into solution (free osmosis). The solution was inside a collodion bag and the latter dipped into a beaker filled with distilled water. The ordinates of the curves give the rise in the level of liquid after 20 minutes in a glass tube pushed through a rubber stopper into the collodion flask. The curves show, as pointed out in a preceding publication, 1 that the level rises at first with increasing concentration until it reaches a maximum at about ~/512 or M/256 and that it then drops with a further rise in concentration until the latter is ~/16 when a second rise begins. The second rise is presumably the expression of a prevalence of the gas pressure effect while the first rise and fall are the effect of the electrostatic influence of the ions on the rate of diffusion of water. As stated in the preceding publication, pure water as well as water containing electrolytes is positively charged when in contact with a collodion membrane while the latter is negatively charged. Leaving aside the gas pressure effect on the rate of diffusion, water will be driven through the pores or interstices of the