ON A SIMPLE HIGH-TEMPERATURE DIRECT REACTION CALORIMETER

Several commercial and laboratory-made instruments have been described in the literature based on a drop technique and containing an isoperi bolic differential detector. The instrument presented here consists of two cells set one above the other and located in ceramic and metallic tubes for thermal equalization. The temperature difference between th e two cells (working and reference cells) is measured by a 20-couple t hermopile. The calorimeter is enclosed in a furnace with three indepen dently controlled zones which can be heated up to 1200 degrees C. A ty pical run consists of dropping from a room temperature thermostat a sm all capsule containing about 2 g of a metal mixture. The heat effect i s evaluated by dropping, before and after the capsule, a number of wei ghed Ag specimens. Subsequently, in a second run, the same capsule con taining the reacted sample is dropped again into the calorimeter. The difference between the heat effects obtained in the two runs gives the room temperature heat of formation of the alloy. A brief description of the instrument, of the calibration procedure and of the necessary a uxiliary examinations is reported and the results obtained in a first set of measurements on a number of alloys are given.