High-pressure photoacoustic calorimetry

A high-pressure photoacoustic calorimeter has been developed to operate up to 200 MPa. Photoacoustic calorimetry can be used to study the microsecond kinetics and thermodynamics of reactions in solution. Both thermal expansion and volume of reaction contribute to the generation of the photoacoustic signal, and the separation of these contributions has been achieved by the variation of pressure. The construction of a stainless-steel flow cell, bellows, and a high-pressure manifold are described. These components enable rapid sample change and sample flow at high pressure. As a test, the enthalpy and volume of reaction were determined for diphenylcyclopropenone decomposition to diphenylethyne and carbon monoxide. (C) 2000 American Institute of Physics. [S0034-6748(00)00511-6].