Differential Thermal Analysis under High Pressure I: Investigation of the Polymerisation of Liquid Sulfur

A DTA apparatus constructed for pressures up to 4000 bar and temperatures to 500°C is described. It was applied to the qualitative and calorimetric investigation of the monomer‐polymer equilibrium in liquid sulfur (commonly called Sλ‐Sμ transition). A resulting polymerisation line determined by the connection of the floor temperatures at different pressures shows only a slight negative pressure dependence; it starts at 159°C at normal pressure and intercepts the melting curve at approx. 155°C and 1300 bar the slope of the P(T)‐curve becoming increasingly steeper. The increase of polymer formation in liquid sulfur at the Sλ‐Sμ transition can be deduced quantitatively from the calorimetric measurements.