Abstract: A system for determining the volumetric ratio of solids suspended in a liquid comprises a photometer or similar means for passing a beam of electromagnetic energy through a sample of the liquid having solids suspended therein. Means for measuring a characteristic representative of the amount of energy absorbed by the sample is provided, as a photo detector for example. The volumetric ratio is then computed by applying a proportionality factor characteristic of the solids suspended in the liquid to the output of the measuring means.