The Effects of Salts and Nonelectrolytes on the Solubility of Potassium Bitartrate: An Introductory Chemistry Discovery Experiment

An introductory chemistry discovery experiment on the effect of the presence of various solutes on the solubility of potassium bitartrate (KHT) is presented. Aqueous solutions of KCl, NaCl, MgSO 4 and glucose with concentrations ranging from 0.0 to 0.10 M are saturated with KHT. The solubility of the KHT in these various solutions is determined by titration with standardized NaOH solution. The results show that the solubility of KHT is unaffected by changing the glucose concentration, decreases with increasing KCl concentration, and increases with increasing NaCl and MgSO 4 concentration. MgSO 4 causes a greater increase in solubility than does NaCl. The results are presented graphically and are interpreted in terms of the common ion effect and interionic interactions. The apparent solubility product constant is found to increase with the ionic strength of the solute. When the experiment is repeated with KCl-NaCl mixtures at a constant ionic strength, the solubility product constant does not vary with the composition of the mixture.