François-Marie Raoult, a French Chemist, researched into the properties and behavior of solutions, including the vapor pressure lowering and the depression of freezing points. The relationship between solution and solvent vapor pressure depends on the concentration of the solute in the solution. It is given by Raoult’s Law, which states that the vapor pressure of a solvent over a solution, P1, is given by the vapor pressure of the pure solvent, P1o, times the mole graction of the solvent in the solution X1:

It can be rewritten as the formula below, where a directly proportional relationship between decrease in the vapor pressure and concentration of the solute present is observable.