DIFFERENTIAL THERMAL-ANALYSIS OF LINEAR-CHAIN MERCURY-COMPOUNDS

Differential thermal analysis of powders and single crystals of Hg//3// minus // delta AsF//6 is reported for the temperature interval 100 to 500 K. There is an endotherm at 234 K, corresponding to the melting of mercury during warming, but no exotherm at this temperature during cooling. The amount of mercury expected from simple contraction of the lattice from room temperature. These results are explained by the presence of a phase of dispersed, solid mercury in the sample. Mercury is formed at the order-disorder transition of the mercury chains and melts at 235 K. Mercury in samples with some decomposition showed a freezing exotherm after supercooling at 18 K. There is irreversible thermal decomposition of Hg//3// minus // delta AsF//6 above 400 K.