II. On the solubility of salts in water at high temperatures

Abstract

The experiments of which an account is given in the following paper originated in a desire to investigate further the remarkable anomalies which have been observed in the solubility of sulphate of sodium in water. It appears to have been first discovered by Gay Lussac (Ann. Chim. Phys., xi., 313) that whilst the solubility of this salt in water increases rapidly with rise of temperature above zero, it attains a maximum at 33° or thereabouts, and above that temperature diminishes till the boiling point (about 103°) of the saturated solution is reached. On referring, however, to the curve of solubility for this salt traced by Gay Lussac, or to the numbers published many years afterwards by Löwel (Ann. Chim. Phys. [3], xlix., 32), it will be seen that the rate of decrease of solubility, though at first rapid, soon slackens, and the descending curve becomes nearly parallel with the axis of the abscissae representing temperatures. It appeared probable that if the solubility of sulphate of sodium could be traced through a range of higher temperatures, the solubility would be found once more to increase, and the curve resume an upward direction.