Solubility of Sodium Chromate and Sodium Aluminate in Sodium Hydroxide Solution

Abstract

The solubility of sodium chromate and sodium aluminate in sodium hydroxide solution at 80°C, was determined in connection with the separation process of sodium chromate and sodium aluminate from the reaction product of chromite with molten sodium salts.
In the Na₂CrO₄-NaAlO₂-NaOH-H₂O system, it has been found that the solu bility of sodium chromate decreased along a smooth curve with the increase of sodium hydroxide concentration, and that the solubility of sodium aluminate increased sharply to the maximum point at the sodium hydroxide concentration: ca.34%, and then decreased markedly, with the increase of sodium hydroxide concentration. Solid phases were Na₂CrO₄, Al₂O₃ ⋅n H₂O, NaAlO₂⋅ n H₂O and 4 Na₂O⋅CrO₃. Al₂O₃⋅n H₂O.
New solid phase, 4 Na₂O⋅CrO₃⋅Al₂O₃⋅n H₂O, was recognized as a double salt composed of Na₂CrO₄ and 3 N ₂O⋅Al₂O₃⋅n H₂O. Studies on Manufacturing Process of Sodium Chromate. V.