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.
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