A differential heat-conduction microcalorimeter for heat-capacity measurements of fluids

Abstract A heat-conduction calorimeter has been developed for measuring small changes in heat capacity of milligram samples of membrane lipid dispersed in water as a function of temperature. The operation of the instrument is based on the principle that the thermal response of the sample to a short (10 s), electrically generated heat burst is a function of the diffusivity of the sample. Modeling studies of the instrument's performance have revealed that the output response after the heat burst is a function of only the heat capacity, ϱC p . Calibration of the instrument experimentally confirmed this behavior. This feature obviated the need to measure the thermal conductivity in order to determine ϱC p from the diffusivity equation, η = γ / ϱC p . The calorimeter has the following characteristics: reproducibility of loading: ± 400 μ J/C° · cm 3 ; baseline stability: ± 10 μ J/C° · cm 3 per 36 h; resolution (± 1 S.D.): ± 50 μ J/C° · cm 3 ; sample size 600 μl.