The thermal conductivity of solid and liquid sulphur

Abstract

By reason of the multiplicity of its solid and liquid phases, the physical and chemical properties of sulphur have been the subject of many investigations in the past. The technique of measuring thermal conductivities using a temperature drop across the specimen of only a few degrees has reached a precision which affords an additional means of exploring change-point regions. An investigation has therefore been undertaken of the thermal conductivity of solid and liquid sulphur over a range of temperature from 20° C. to 210° C., a region which embraces the transition point from rhombic (α) to monoclinic (β) sulphur (95° C.), the “natural” melting point of monoclinic sulphur (115° C.), and the well-known change-point of liquid sulphur (160° C.) with its conspicuous alterations in physical properties (fig. 1). In the case of solid sulphur, measurements have been made of the thermal conductivity of the rhombic and monoclinic varieties each in the form of crystalline aggregates. The influence of the previous thermal history of a sample of sulphur on the velocity of the reversible rhombic-monoclinic transformation has been demonstrated by thermal conductivity measurements. In addition, measurements have been made on the “plastic” variety of sulphur obtained by the sudden chilling of molten sulphur near its boiling point, the progressive change in thermal conductivity being followed during the slow transition at room temperature from the unstable plastic to the stable rhombic form. It has also been shown by conductivity experiments how the rapidity of this transformation is influenced by the temperature.