Abstract Abstract The construction of a heat-conduction flow microcalorimeter of the twin type, that uses thermopiles to detect thermal changes in the reference and reaction cells, is described. For comparative purposes, gold and silver cells, with different geometric shapes, are used. The calorimetric set is immersed in a water thermostat at a temperature of 25.000 ± 0.005°C. The thermostat is placed in a room whose temperature is controlled to 25.0 ± 0.2°C by an air thermostat. The calibration constant of the apparatus is determined for several values of electric work and power. Values of 22 WV1 and 14 WV1 are obtained for the gold and silver cells, respectively. The influence of the flow rate on the potential signal is studied. Chemical calibrations are performed with HCl-NaOH, THAM-HCl (trihidroxymethylaminomethane), and urea-water systems at different flow rates. The results are in good agreement with those reported in the literature.