Preparation of Sodium Citrate Directly from Calcium Citrate

Abstract

The preparation of sodium citrate from calcium citrate involves initial preparation of citric acid by decomposition of calcium salt with H₂SO₄, neutralization with Na₂CO₃ and subsequent crystallization by evaporation. The reaction proceeds 98% even by applying Na₂CO₃ to calcium citrate while hot. However, sodium citrate so prepared contains pectin substance and is difficult to purify. By purification with concentrated NaCl solution, solubility of pectin substance is lowered, thereby decreasing the amount of the same in solution and lowering the solubility of sodium salt. Moreover, this NaCl solution can be used repeatedly which makes it economical. Although sodium citrate so prepared contains a small amount of NaCl, it can be brought up to the standard of Pharmacopoea by recrystallization.