μFlowCal – High‐Resolution Differential Flow Microcalorimeter for the Measurement of Heats of Mixing

Abstract

The authors dedicate this article to Professors Margarida Bastos and Ingemar Wadsö for their support, recognition, enlightenment and inspiration.This work presents the description, calibration, test and performance evaluation of a new flow microcalorimeter. The μFlowCal is a differential heat conduction, flow microcalorimeter, designed to work in isothermal conditions, in differential mode and in the absence of gas phase, requiring small amounts of sample (200 μL). Both the microcalorimeter and its operational methodology were optimized to measure the heat of mixing of fluids with moderate viscosity and volatility. The microcalorimeter has a sensitivity of 116 μV mW À 1 and a level of detection of 170 nW. A very good performance (uncertainty < 5 %) was obtained for the selected test processes: enthalpy of dilution of aqueous sucrose solutions and excess enthalpy of binary mixtures of decane-octanol. The μFlowCal prototype is a new tool in micro-scale physical chemistry and a step forward concerning signal resolution and sample volume. Nowadays, these are major requirement for the study of novel promising solvents and their mixtures.