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Osmotic and diffusive forces in human society are all the results of incongruences, disparities, differences, inequalities and the negative and positive emotions attached to them. The passengers of the first class were preferred because they paid more for their tickets.
Osmotic pressure will then appear to be due to the shock of the dissolved molecules against the membrane. It will come from one side of this partition to superpose itself on the hydrostatic pressure, which latter must have the same value on both sides. The analogy with a perfect gas naturally becomes much greater as the solution becomes more diluted.
A noted European chemist, Dr. Leduc, has produced what he calls "osmotic growths," from purely unorganized mineral matter growths in form like seaweed and polyps and corals and trees. His seeds are fragments of calcium chloride, and his soil is a solution of the alkaline carbonates, phosphates, or silicates.
Developing this idea, Professor Nernst calculates, by means of the action of the osmotic pressures, the variations of energy brought into play and the value of the differences of potential by the contact of the electrodes and electrolytes.
The coincidence of the formulas would thus be verified, for all the characteristic equations are symmetrical with regard to these two pressures. From this point of view the osmotic pressure would be considered as the result of an attraction between the solvent and the solute; and it would represent the difference between the internal pressures of the solution and of the pure solvent.
At a certain moment the pressure will cease to increase and will remain at a fixed value which now has a given direction. This is the osmotic pressure. Pfeffer demonstrated that, for the same substance, the osmotic pressure is proportional to the concentration, and consequently in inverse ratio to the volume occupied by a similar mass of the solute.
He gave figures from which it was easy, as Professor Van t'Hoff found, to draw the conclusion that, in a constant volume, the osmotic pressure is proportional to the absolute temperature. De Vries, moreover, by his remarks on living cells, extended the results which Pfeffer had applied to one case only that is, to the one that he had been able to examine experimentally.
The osmotic force will not force fat drops through membranes, and to explain their passage through the walls of the intestine requires something additional. We are as yet, however, able to give only a partial explanation of this matter. The inner wall of the intestine is not an inert, lifeless membrane, but is made of active bits of living matter.
At all events, the endosmotic or exosmotic action of the skin of a living body must necessarily play an important role in the absorption of medicinal agents; and, on the other hand, it is plain that fats, which render the living skin impermeable, necessarily also diminish or entirely neutralize its osmotic action.
If the liquid, instead of being a solvent like pure water, contains an electrolyte, it already contains metallic ions, the osmotic pressure of which will be opposite to that of the solution.
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