Kontinuierliche Bestimmung von Mischungswärmen durch isotherme Enthalpietitration

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Abstract
A continuous method for determining the heats of mixing of liquid systems is described by which the complete mixing curve of a binary system, HM= ƒ(NA) is rapidly obtained by two experiments only, giving 40 or more curve points which are accurate to better than ±1%. Isothermal conditions within +0.002° to ± 0.008° are maintained by means of controlled thermoelectric cooling or heating. The air space above the liquid is completely excluded by operation at constant volume; the pure liquid B enters and the equilibrated mixture leaves the calorimeter vessel with equal velocities. A theoretical discussion of the heat balance equation of this mixing procedure, including the performance curve of the thermoelectric module, the response characteristics of the controller for the Peltier current, and the influence of excess volumes, is given. As examples for the correct operation of the heatof- mixing calorimeter described, the results at 25° for the systems acetone -chloroform, benzyl acetate -chloroform, and pyridine -chloroform are given; they agree with the literature data within the uncertainty limits reported there.

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