Solubility and Solubility Product Determination of a Sparingly Soluble Salt: A First-Level Laboratory Experiment

A simple experiment was devised to let students determine the solubility and solubility product, K sp, of calcium sulfate dihydrate in a first-level laboratory. The students experimentally work on an intriguing equilibrium law: the constancy of the product of the ion concentrations of a sparingly soluble salt. The determination of solubility is proposed either in an equimolar precipitation of CaSO 4 ·2H 2 O, from which the K sp is obtained, or working with an excess of one of the two reagents.