  Another set of phenomena providing opportunities to develop atomism involved the effects of solutes on solutions. It was discovered that effects such as the depression of freezing point and vapour pressure and the elevation of boiling point of a solvent brought about by dissolving a non-electrolytic solute in it are proportional to the weight of dissolved substance and, what is more, that the relative effects of differing solutes in a given solvent were determined by the molecular weight of the solute. More specifically, the magnitude of the various physical effects of a solute was dependent on the number of gram molecules of the dissolved solute, independent of the chemical nature of the solute. This provided a way of measuring the molecular weight of soluble substances that complimented the method involving the measurement of the vapour pressure of volatile ones. The strong suggestion that these effects depended on the number of molecules per unit volume was strengthened when it was discovered that the osmotic pressure of a solute in a solvent obeys the gas laws. That is, the osmotic pressure exerted by a solute in a definite volume of solvent, measurable as the pressure exerted on a membrane permeable to the solvent but not the solute, was exactly the same as if that same amount of solute were to fill that same volume as a gas.