The determination of enthalpies of sublimation by means of thermal conductivity manometers

✍ Scribed by C. G. de Kruif; H. A. J. Oonk

• Publisher: John Wiley and Sons
• Year: 1973
• Tongue: German
• Weight: 702 KB
• Volume: 45
• Category: Article
• ISSN: 0009-286X
• DOI: 10.1002/cite.330450705

✦ Synopsis

Abstract

This paper describes an investigation into the suitability – for the determination of enthalpies of sublimation of low volatility substances – of thermal conductivity manometers which are operated according to the method described by Engelsman. By making use of the known vapour pressure‐temperature relation of liquid mercury the characteristics of the manometers are obtained. They show deviations from linearity at higher pressures; in spite of this the most suitable manometers still have linear ranges of three to four decades. One of the thermal conductivity manometers (TCM) was used for the determination of the enthalpies of sublimation of benzophenone (Δ~s~H = 22.60 ± 0.10 kcal mole^−1^), benzoic acid (Δ~s~H = 21.05 ± 0.05 kcal mole^−1^), ferrocene (Δ~s~H = 17.7 ± 0.4 kcal mole^−1^) and trans‐stilbene (Δ~s~H = 24.40 ± 0.15 kcal mole^−1^). As the measurements on ferrocene fell outside the linear range of the manometer, it was necessary to introduce a correction coefficient derived from the measurements on benzophenone and benzoic acid in order to obtain satisfactory results.