No abstract

The non-oxidative decomposition of heated sodium dithionite was shown by thermal and i.r. spectroscopic analyses to proceed by two routes depending on sample configuration. The previously postulated reaction 2Na2S204 --* NalS203 +NazSOJ + SO2 predominated when the heaped substance was heated at 16"C/min giving a sudden exotherm of 47 kJ mol-' at 205 "C. In other conditions, particularly when heated in thin layers, two exotherms were found. The major exothenn at 210 "C yielded 63 kJ mol-I the main products being thiosulphate, trithionate, sulphate and sulphite. A subsequent exotherm at 250 "C appeared to arise from phase changes in this material, coincident with the endothermic decomposition of sodium trithionate.