The Solubility of Gypsum in Magnesium Sulphate Solutions
The Journal of Physical Chemistry
The solubility of gypsum in aqueous solutions of magnesium sulphate has not been studied systematically and the few results recorded in the literature must be considered as of a qualitative nature only. Fassbender' states that no gypsum dissolves in a saturated solution of magnesium sulphate even after several days' contact. DroezeS has repeated the experiment a t 13.5' and by analysis of the residual solid finds all the calcium sulphate which was originally added. The solubility of gypsum in a
... lity of gypsum in a solution of magnesium sulphate one-tenth saturated, he gives as 0.86 gram per liter. There is no accurate method of separation of small amounts of calcium from large amounts of magnesium. The separation of calcium from magnesium by precipitation with ammonium oxalate is feasible only in case the magnesium salts are present in small amount. This is due to the wellknown solvent action on calcium oxalate by magnesium salts. The method based on the solubility of niagnesium sulphate in aqueous alcohol and the insolubility of calcium sulphate in this solvent is not delicate enough to estimate the calcium in solution when the concentration of magnesium sulphate is great. Attempts to determine the composition of such solutions by analytical means were therefore abandoned and a different method was resorted to. As the detection of small quantities of calcium in the presence of large amounts of magnesium is not feasible in a wet way, the magnesium sulphate was examined spectroscopically and no calcium could be discovered. As a large Published by permission of the Secretary of Agriculture.