The sulphoaluminates of calcium

Abstract

Two calcium sulphoaluminates have been prepared and their compositions and optical characteristics determined. One of these, having the composition 3CaO.Al2O3.3CaSO4,31H2O, is relatively stable in aqueous solutions but is decomposed by solutions of magnesium salts and of carbonates. The other, having the composition 3CaO.A12O3).CaSO4.2H2O, is relatively unstable except in high concentration of hydroxyl ion. It is readily converted to the high sulphate form in aqueous solutions but is decomposed by magnesium salts and carbonates. In sulphate solutions the high sulphate form may be produced, but in the presence of a slight excess of magnesium salts or carbonates neither of the sulphoalutninates can continue to exist. In these cases the less soluble magnesium hydroxide and calcium carbonate, respectively, are formed.