Potassium pentathionate, K₂S₅O₆

The Potassium pentathionate, K₂S₅O₆ and tetrathionate are produced simultaneously by concentrating a solution of sulphurous acid saturated with hydrogen sulphide, filtering off the precipitated sulphur, and adding the calculated quantity of potassium acetate. The salts are separated mechanically by means of a mixture of bromoform and xylene in such proportions as to cause the pentathionate to float and the tetrathionate to sink. The pentathionate has a density of 2.1123 at 20° C. Its heat of formation is 390.1 Cal.