GB423592A - Improvements in and relating to the manufacture of sodium carbonate decahydrate - Google Patents

Abstract

Solid compositions consisting essentially of sodium carbonate decahydrate are prepared by obtaining a uniform magma approximating in composition to sodium carbonate decahydrate of which the solid phase consists essentially of sodium carbonate heptahydrate, with or without some decahydrate, and which accordingly has a temperature of 32--35 DEG C., forming the magma into shapes, e.g. by pouring into moulds or by extrusion and cutting, and rapidly cooling the magma to a temperature substantially below 32 DEG C., during or immediately after forming. The final shaped bodies may contain some of the heptahydrate. Some sodium bicarbonate may be introduced into the initial mixture and additional detergent substances such as soap, sodium phosphate or sodium aluminate may be added at any convenient stage. The magma may be obtained within the specified temperature range by rapidly cooling from a higher temperature a liquid or magma of the necessary composition, for example a mixture of soda ash and water may be brought into the stable range of the p monohydrate, that is above 35 DEG C., prior to adjusting the temperature within the range 32--35 DEG C. The preparation may be carried out continuously by adding the required quantities of the initial ingredients to a large quantity of the hot stirred magma, from which the corresponding quantities are withdrawn for cooling to 32--35 DEG C. followed by shaping and further cooling as above described. Finely ground sodium carbonate decahydrate crystals may be added to the magma at 32 DEG C. to modify the consistency. The magma may also be prepared by melting sodium carbonate decahydrate crystals. Specification 232/02, [Class 1], is referred to.