A small scale (100 mL) calorimeter is developed. It includes a glass vessel submerged in a thermostatic bath, a compensation
electrical heater, and a control system. The typical operation mode consists on introducing the solvents and part of the reactants
into the vessel, to stabilise a temperature of the bath (Tj) some degrees below the desired process temperature (Tp) and to adjust the reaction mass temperature (Tr) to Tp using the electrical heater. An oscillating set point is established for Tr, which produces an oscillating response of the
applied compensation power (Qc). Finally, the rest of reactants are dosed to the vessel. A small deviation of Tr and Tp is observed. Even though it can be avoided improving the tuning of the controller, it can be useful for enhancing the calculation
of the heat capacity of the reaction mixture (CP). The signals of Tr, Qc and Tj are processed on-line using the FFT (Fast Fourier Transform) method as the mathematical tool used to analyse the data obtained,
producing accurate values of the heat evolved (Qc) by the process, the heat transfer coefficient (UA), and the heat capacity of the reaction mixture (CP).