Refined Flow Microcalorimetric Setup for Measurement of Mixing Enthalpies at High Dilutions: Determination of Infinite Dilution Dissolution Enthalpies of Some Alkanol and Ether Solutes in Water

Abstract

A refined flow microcalorimetric setup with a fully automatic control of the entire experimental sequence has been designed for accurate measurement of mixing enthalpies of highly dilute aqueous solutions as a function of composition and, in turn, for reliable determination of the solute's infinite dilution dissolution enthalpies (Δsol ). The instrument and procedure were extensively tested, and their performance was verified using various microcalorimetric standards and further test reactions that involved the dissolutions of 1-propanol at eight temperatures from (283.15 to 318.15) K, of 1-butanol at 298.15 K, of 2-hexanol at five temperatures from (288.15 to 318.15) K and the dilutions of 10 % mass fraction aqueous 1-propanol and 2 mol·kg-1 sucrose solutions at 298.15 K. It was found that even for viscous solute media (viscosity 7 mPa·s) of limited aqueous solubility (mole fraction 0.002), Δsol could be determined with a combined standard uncertainty of 1 % or lower. The microcalorimeter was employed to determine Δsol for further oxygenated solutes for which these data are lacking or insufficient, namely, for 2-pentanol, 3-methyl-1-butanol, and 3-methyl-2-butanol at 298.15 K, for 1-methoxy-2-propanol at four temperatures from (288.15 to 318.15) K, for diethyl ether at five temperatures from (283.15 to 303.15) K, and for dimethoxymethane at seven temperatures from (288.15 to 318.15) K. The measurements of Δsol as a function of temperature enabled us to derive reliable values of infinite dilution dissolution heat capacities.