Stability constants of hydracid-tributyl phosphate complexes in alkane solution: hydrochloric acid and hydrogen cyanide
✍ Scribed by K.G. Furton; J.H. Purnell; G. Stedman
- Publisher
- Elsevier Science
- Year
- 1989
- Tongue
- English
- Weight
- 995 KB
- Volume
- 468
- Category
- Article
- ISSN
- 1873-3778
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✦ Synopsis
The gas chromatographic technique of elution by characteristic point (ECP) has been used to determine the stoichiometric stability constants (KJ of complexes of both hydrochloric acid and hydrogen cyanide with tributylphosphate (TBP) in hexadecane solution. The study covered the temperature range 2565°C and the concentration ranges in solution: TBP (O-l _ 1 M> and acids (O-O.3 1M). Values of K1 determined ranges between 20 and 120 1 mol-' depending on conditions. An extension of gas--liquid chromatographic theory to take into account dilution of solvent and depletion of TBP (due to the large K1 prevailing) at high acid levels is presented and its validity demonstrated. This will allow correction for purely formal effects to be made in future studies of this type.
The results are shown to be of high accuracy and, hence, both to provide a secure reference base for further studies and to establish ECP as a technique of wide applicability, and relative practical simplicity, for the investigation of systems of large K1 at finite (practical) concentrations.
Measurements for the acids in hexadecane alone allow estimation of the enthalpy of vaporisation of hydrochloric acid around its critical temperature as 3.8 kcal mol-I, and of monomeric hydrogen cyanide (2565°C) as 2.4 kcal mall'. The latter figure implies an enthalpy associated with the hydrogen-bonding polymerisation of liquid hydrogen cyanide of 3.6 kcal mol-'.