Abstract A Tian-Calvet heat-flow microcalorimeter system is described for measurement of heats of adsorption and reaction on porous solids. Heat-flow signals are measured in transducer assemblies consisting of several hundred Seebeck-effect thermoelements connected in series and arranged in a square configuration. These transducers surround a stainless steel calorimeter cell connected to a high-vacuum volumetric adsorption system. The sensitivity of the calorimeter was calibrated by measurement of electric response and of heats of adsorption for known processes. Microcalorimetric measurements have been conducted at temperatures from 273 to 298 K. The calorimetric cell described here facilitates sample handling under controlled atmosphere conditions, allowing the study of freshly treated materials and samples that have been exposed to catalytic reaction conditions.