The apparent (molal) volume of a solute can be expressed as a function of the molality b of that solute (and of the densities of the solution and solvent). The volume of solution per mole of solute is
Subtracting the volume of pure solvent per mole of solute gives the apparent molal volume:
For more solutes the above equality is modified with the mean molar mass of the solutes as if they were a single solute with molality b:
The sum of products molalities – apparent molar volumes of solutes in their binary solutions equals the product between the sum of molalities of solutes and apparent molar volume in ternary of multicomponent solution mentioned above.