One type of concentration precisely delivers a known amount of solute by measuring the volume of the solution. Molarity and % mass-vol (% wt-vol) are examples of this type. The moles of solvent are not precisely defined in these solutions. Volumes of solution are not the same as volumes of pure solvents.

The other type of concentration allow the precise determination of the moles (and mass) of each component in the solution from the concentration. Mole fraction, % by mass, molality, and ppm units of concentration are examples of this type. The ratio of solute to solvent is precisely defined in these concentration units. These solutions are frequently used for measuring intensive properties of solutions such as vapor pressure, osmotic pressure, and freezing point depression.