Use of a fixed-cell, power-compensation, differential-output, temperature-scanning calorimeter to measure heat capacities of NaCl(aq) at temperatures from 283.15 K to 393.15 K at the pressure 0.35MPa
✍ Scribed by Earl M. Woolley
- Publisher
- Elsevier Science
- Year
- 1997
- Tongue
- English
- Weight
- 163 KB
- Volume
- 29
- Category
- Article
- ISSN
- 0021-9614
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✦ Synopsis
We have used a fixed-cell, power-compensation, differential-output, temperature-scanning Ž . Ž . Ž . calorimeter d.s.c. to measure heat capacities of NaCl aq at T s 283.15 to 393.15 K at the . y1 pressure 0.3 MPa. Consecutive scans at a rate of 16.7 mK s gave results that were 5 Ž .
3 reproducible to " 1 to 2 W for filled cells of nominal volume 0.9 cm . The difference between volumic heat capacities of liquids in the working cell for two separate experiments is proportional to the difference between the calorimetric outputs from temperature scans run at the same scan rate and pressure. In a ''baseline'' experiment, scans are made when both cells contain water. In the second experiment, the reference cell contains water and the sample cell contains the solution of interest. The calibration constant was determined over the temperature range of the experiments from results of measurements on a solution of . y1 Ž . Ž . known volumic heat capacity, 1 mol kg NaCl aq . More dilute solutions of NaCl aq were then treated as ''unknowns'' to test the calorimeter's ability to measure volumic heat capacities. Apparent molar heat capacities C calculated from the results of multiple p, temperature scans both upward and downward, and also from replicate experiments, have . y1 . y1 Ž . root-mean-square deviations ⌬ less than 0.