The Decomposition of Sodium Carbonate

JSGT 1934 V18 T182-T193

A study has been made of the decomposition at temperatures from 650° to 1100° of sodium carbonate heated in air and in a stream of water vapour. Decomposition of the material took place to an appreciable extent at 800°, and was even detectable after heating for one day in –air at 400°, temperatures much lower than the commencement of dissociation in an evacuated system. This decomposition in air is regarded as due to reaction between sodium carbonate and the water vapour of the atmosphere resulting in the formation of free sodium hydroxide. At 800° the equilibrium was approximately 97·5% Na₂CO₃ and 2·5% NaOH, although these figures were largely dependent on the mass and depth of charge. Sodium carbonate required in a high state of purity should not be heated for any appreciable time above a dull red heat (500°), and the safe limit should be regarded as 400°.

Eric Preston & W. E. S. Turner