Netsu Sokutei, 48 (3), p. 93, (2021)



Development of Quasi-Conduction Type of Calorimeter for Solution and Applications to Systems of Aqueous Solutions

A simple design of quasi-conduction type of calorimeter has been developed and constructed using cheap parts and commercially available equipment to measure enthalpy of dissolution, titration or mixing of liquid easily. Heat change of the calorimeter could be calculated from detected temperature change on mixing of liquids by Wheatstone bridge circuit with thermistor temperature sensor. Resolution and reproducibility were estimated to be less than 0.03 J in observed heat and 0.6 %, respectively, from linearity test using the calibration heater. Result of enthalpy of dissolution of 1-propanol in water at infinite dilution was 10.52 kJ mol-1, which agreed with IUPAC standard value within 3.5 %. To demonstrate the applicability to education, academic study and industrial development, the apparatus was used in three types of measurements. From the study of enthalpy of dissolution of ethanol in aqueous salt solution, weakened solvation enthalpy of ethanol in water was observed by adding CaCl2 rather than adding MgCl2. In application of titration measurement for neutralization of acid with aqueous NaOH base, oxalic acid and phosphoric acid show different values for equivalent neutralization heat at each different dissociation step of ionization equilibrium. In the measurement of enthalpy of mixing, endothermic heat was detected for mixing of LiCl + NaCl aqueous solutions, regardless of exothermic heat for LiCl + all the other salts.