Enthalpy Measurements of Condensed Matter by Peltier-element-based Adiabatic Scanning Calorimetry (pASC)
Adiabatic scanning calorimetry (ASC) is a technique that aims to simultaneously measure the temperature dependence of the enthalpy and the heat capacity of a liquid or solid condensed matter sample. The basic concept of ASC resides in applying a constant heating or cooling power to a sample holder containing the material to study. Although the ASC concept was first implemented in the late 1970s and further improved over the years, instruments remained largely limited to specific research applications because they required operation by skilled and trained personnel. This was not least due to elaborate construction and control to impose adiabatic conditions, as well as complicated sample cell mounting. In this chapter we describe a novel implementation, incorporating a Peltier element between the sample cell and the adiabatic shield. The new user-friendly Peltier-element-based adiabatic scanning calorimeter (pASC) allows measurements over large temperature ranges on milligram-sized samples with high resolution in temperature, enthalpy, and heat capacity. In addition to the heating and cooling modes of the pASC, it can also be used as a classical heat step calorimeter and in differential scanning calorimetry (DSC) type heat-flux or power-compensated modes. As examples, enthalpy results are presented for the melting transitions of gallium and water, and for phase transitions in an aqueous lipid vesicle suspension and in a liquid crystal.