Differential Thermal Analysis and PVT Measurements on 2,2,2-Trichloro-ethanol Under High Pressure

Abstract

The phase behaviour, the calorimetric and volumetric properties of 2,2,2-trichloro-ethanol (TCE) have been studied with differential thermal analysis (DTA) and pVT measurements in the pressure range 1 atm to 300 MPa and temperatures between 250 K to 355 K. TCE displays a metastable plastic phase (solid I') and a non-plastic solid phase II at atmospheric pressure. At least two pressure-induced solid phases have been detected: a stable plastic phase (solid I') and a non-plastic phase (solid III). There are two sets of triple points: a) 123 MPa and 308 K with the phases solid I, solid II and the liquid, b) 243 MPa and 316 K for solid I, II, III. Furthermore a metastable low-temperature brittle form (solid II') has been found, which transforms to solid I at a considerably lower temperature than solid II. The melting curve of solid I' can be pursued to higher pressures up to 260 MPa. On the other hand, the melting curve of the stable plastic phase solid I can be extrapolated beyond the triple point to pressures below 123 MPa. Volume and enthalpy changes are reported for all phase transitions.

Thermodynamic Measurements on n-Hexadecane (C16H34) and n-Heptadecane (C17H36) at Elevated Pressures

“…The high-pressure dilatometric cell is described in [2,17]. The sample is separated from the pressurizing gas by a moving piston whose displacement is recorded inductively.…”

“…DTA (Differential thermal analysis) and pVT measurements have been performed for many plastic crystals in the last years [ 1,2], In the present contribution we present results for some /?-alkanes, which play an important role as model systems for lipids, polymers and liquid crystals [3,4], In particular multi-component systems of/7-alkanes are used as thermal protection materials and for energy storage applications, and therefore their excess thermodynamic properties of the rotator phase solid solutions have been analysed in detail [5,6], Whereas densities of the liquid state for^-alkanes have been reported by many authors [7,8], only few pressure-volume studies are concerned with the solid state [9][10][11][12], pVT data of //-alkanes have been widely used to model the equation of state [13] which enables also to calculate the volume-dependent part of the entropy of melting [14], We studied /z-C 16 H 34 (M = 226.44 g/mol) and n-C 17 H 36 (M = 240.47 g/mol) in the neighbourhood of their phase transitions (crystal -* rotator phase -* liquid) up to 300 MPa. Volume and enthalpy changes accompanying the phase transitions are reported.…”

Dielectric spectroscopy on two orientationally disordered crystals: NPA (CH2OHC(CH3)3) and TCE (CH2OHCCl3)

“…As far as TCE is concerned, and despite the molecular structural analogies with NPA, so far only one work has been reported in the literature about the phase behaviour of TCE at normal pressure and under pressure [10]. In such a work, the P -T and P -v-T phase diagrams were reported in order to determine the phase properties and specific volumes for the liquid and solid states.…”