A new general-purpose isothermal microcalorimeter for use at temperatures up to 200 degrees C

The design and some properties of a new general-purpose isothermal microcalorimeter are reported. The instrument is a twin thermopile heat conduction calorimeter, which is designed for use up to 200 degreesC. The calorimetric units and surrounding heat sink are suspended inside a hollow aluminium construction, which is thermostated. Above that unit a second thermostated block is positioned and the whole assembly is suspended inside a Dewar vessel. When the instrument is used at room temperature and below, the thermostated units are cooled by use f an insertion Peltier effect cooler. The instrument can be used with a wide range of different reaction vessels (diameter 14 mm). Baseline experiments have been conducted in the temperature range 15-200 degreesC. Typical values obtained during 10 h periods at 200 degreesC are +/-3 and +/-10 nW for the baseline drift and baseline fluctuations, respectively. The heat detection limit, determined by release of electrical energy, is about 2 muJ. Preliminary stability measurements have been conducted at 100 degreesC on samples of stabilised and non-stabilised polyamide film. (C) 2003 Elsevier Science B.V. All rights reserved