A high-temperature high-pressure calorimeter for determining heats of solution up to 623 K

Abstract

A high-temperature high-pressure isoperibol calorimeter for determining the heats of solution and reaction of very dilute substances in water (10(-4) m) at temperatures up to 623 K is described. The energies of vaporization of water at steam saturation pressure were measured as a function of temperature and the results agree with the corresponding values from steam tables to better than 0.08+/-0.18%. The novelties of the present instrument relative to flow type heat capacity calorimeters are that measurements can be made at orders of magnitude lower concentrations and that measurement of heat of reaction involving solids or gases or in the presence of high concentrations of supporting electrolytes, acids, and bases is possible. Furthermore, the advantage of using enthalpy data over heat capacity data for calculations of the standard state Gibbs free energies of electrolytes is that the experimental heat data of this research need only be integrated once to derive higher temperature free energy data from lower temperatures. The derived heat capacities can be used mathematically to obtain free energies by double integration. However, the resulting errors are much smaller than if experimental aqueous heat capacities were used for the integrations.

Heat output by marine microbial and viral communities

“…The calorimeter was provided with a calibration heater through which the chemical generation of heat by microbes was simulated by introducing a carefully measured quantity of electrical energy [21]. A simplified diagram of the calorimeter is shown in Figure 1.…”

“…The software can then continuously calculate the total energy introduced into the calorimetric system until this energy reaches a predetermined value. The circuitry for generating and measuring the electrical energy has been described previously [21].…”