An isothermal flow calorimeter for use with corrosive solutions from 50 to 125°C

Abstract

An isothermal flow calorimeter suitable for measuring heats of mixing of two fluid streams which may or may not contain reactive solutes is described. The calorimeter proper was constructed of a platinum-10% rhodium alloy (tubing) and platinum-10% iridium alloy (mixing chamber) in order to obtain corrosion resistance to both strong acids and strong bases. Endothermic and exothermic processes can be studied from 323 to 398 K and from 0.1 to 20 MPa with the calorimeter. Energy effects from 0.0025 to 0.50 J sec −1 are measured at a constant temperature and pressure through the use of an automatically controlled pulsed heater and a constant cooling Peltier device. The calorimeter was tested (pressures given in parentheses) by measuring the heat of mixing of ethanol and water at 348.15 K (1.52 MPa) and the heat of dilution of aqueous sodium chloride at 323.15 (0.34 MPa), 348.15 (0.34 MPa), 372.85 (6.6 MPa) and 398.15 K (1.03 MPa), and was found to produce data in good agreement with literature values.