In vol. vi. of the Zeitschrift für Physikalische Chemie (1890), pp. 16–36, Nernst demonstrates the relation between the osmotic pressure of a given solution of N in A and the difference of concentration of two solutions of A in B, the one made by shaking up B with A and the other by shaking up B with the solution of N in A; where A and B are two liquids miscible with each other, but not in all proportions, as, for instance, water and ether, and N a substance soluble in A but not in B. Immediately after this paper, Nernst describes (l.c., pp. 37–40) an osmotic experiment in which the “semipermeable membrane” is a layer of the liquid B held in its place by capillarity. Through this layer no N can pass, because N is insoluble in B, but A will pass from what we may call the A side, on account of the concentration gradient, the layer of B containing more A dissolved in it on the A side than on the solution side. At the same time a pressure is developed on the solution side equal to the osmotic pressure of the solution of N.

So far as the diffusion of A through the layer of B from the A side to the solution side is concerned, Nernst's experiment can be shown without fixing the layer of B. In the form exhibited to the Society, A is water, B phenol, and N calcium nitrate.