Simultaneous thermal analysis apparatus was used to determine the thermal properties of gaylussite over a temperature range from ambient to 1,000 deg c at 10 deg per minute in several carefully controlled atmospheres. In a dry atmosphere, dehydration occurs in a single step, but in the presence of water, dehydration occurs in two steps. Dehydration converts gaylussite to double carbonate, na2ca(co3)2, which generate the thermal effects above 250 deg c. From 250 deg to 500 deg c thermal analysis indicates one major crystal change and two crystal inversions in the double carbonate. Above 500 deg c the thermal properties of the double carbonate are controlled by the presence or absence of co2 in the atmosphere surrounding the sample. In a co2 atmosphere na2ca(co3)2 first melts, then decomposes to form na2co3 and cao. In a co2-free atmosphere the double carbonate decomposes to form na2co3 and cao. Melting is again detected by thermal analysis; however, the material that melts is na2co3 formed from decomposition of the double carbonate.
Am. Mineralogist, V. 58, July-August 1973, PP. 778-784