Note 230 — Chapter VII · PHYSICAL OR HETEROGENEOUS EQUILIBRIUM.—THE COLLOIDAL CONDITION

[Br]aq. and [Br]ch. are used to express the actual concentrations at any given moment we wish to consider, for instance at the moment equilibrium is reached. The ratio k2 / k1 for any substance S is found to be equal to the ratio of the solubilities of the substance in the two solvents. That it must be so can be proved by applying the law of physical equilibrium to the mixed solvents in contact with an excess of the substance, i.e. to its saturated solutions (see below).