In a mixture of closely related liquids (such as benzene and toluene), the Raoult law states that the ratio p_A is proportional to the mole fraction of A in the liquid, ${\mathrm{P}}_{\mathrm{A}}={\mathrm{P}}^{\circ }{\mathrm{Ax}}_{\mathrm{A}}$. Mixtures that obey the law throughout the composition ranges from pure A to pure B are called ideal solutions. In ideal solution the solute also obeys Raoult’s law. Then the total pressure is given by ${\mathrm{P}}_{\text{total }}={\mathrm{P}}_{{\mathrm{A}}^0}{\mathrm{x}}_{\mathrm{A}}+{\mathrm{P}}_{\mathrm{B}}^0{\mathrm{x}}_{\mathrm{B}}$.