Three samples of alunite containing various amounts of silica were subjected to heat treatment and the residues extracted with water to recover potassium sulphate. High recoveries were obtained from a sample containing only a small percentage of silica while low recoveries were obtained from the sample with a high silica content. When mixtures of alunite and limestone were heated, improved extraction of potash was generally obtained, while the temperature required was lower than that for alunite alone. The lowering of the temperature however, does not seem sufficient to enable an economic process to be developed from South Australian alunite deposits.