An understanding of calorimeter design as applied at low temperatures (50-70 degrees C) was used to construct a heat balance calorimeter that is also suitable for high-temperature applications (90-120 degrees C). The broad temperature scale means that a wide range of polyreactions can be studied. An accurate model for the thermal effects of the reaction calorimeter is needed to ensure good estimates of basic parameters and to guarantee an accurate characterization of its operation. The time constants of the temperature measurement devices and the heat capacities of the system parts were carefully determined in simulated reactions. The dynamic behaviour of the calorimeter is well described by the five differential equations presented.