A case study for the manufacture of sodium hydrogen carbonate

Abstract

Sodium hydrogen carbonate is used extensively in the baking and pharmaceutical industries, where it is required in very high purity. Commercially, it is prepared through the solvay process. In this project methods of preparing high purity grade sodium hydrogen carbonate from Magadi soda have been investigated. The method studied involves the carbonation of soda ash at varying temperatures, pressures and stirring times. Determinations of sodium carbonate and sodium hydrogen carbonate concentrations were carried out titrimetrically using methyl orange-indigo carmine and thymol blue-cresol red mixed indicators at pH 3.8 and pH 8.3 respectively. This method gave an accuracy of 97% ± 1.9% for concentrations upto 10 ppm. Factors affecting the separation of sodium hydrogen carbonate from the sodium carbonate solution have also been studied. The solubility lities of the two salts differ greatly at 40°C and this has been shown to be the best temperature at which pure crystals of sodium hydrogen carbonate are formed. It has also been shown, through mutual solubility studies, that solubility of sodium hydrogen carbonate in saturated sodium carbonate solution is very low, 0.23g NaHC03 in 51g Na2C03/100g H20.