Study of the behavior of some metallic chelates using gaseous phase chromatography

The behavior of some metallic chelates derived from particular β-dicetones was investigated using gaseous phase chromatography : in view of defining the phenomens taking place in the column, the magnitudes of Sorne thermodynamic parameters such as the enthalpy of the mixture, and the coefficient of activity were determined. The se determinations necessitated, in addition, the values of the specific retention volumes, and the saturated vapor pressure of the pure chelates ; the decomposition of these substances established from pressure measurements lea to the kinetic measurement method adopted. An extrapolation led to the true value of the vapor pressure in the absence of decomposition ; the form of the curve obtained enabled the stability domain of the chelate and the rate of decomposition when this phenomenon intervenes to be defined as a function of the temperature. The values obtained for the coefficients of activities were generally very large and attempts were made to discover the exact nature of the phenomena intervening a particular example is given concerning the hypothesis of a liquid-gas interface which accounts for the values observed, In this way the partition coefficient and the liquid-gas adsorption coefficient were determinéd. It was thus possible to determine the respective participation of the dissolution and adsorption phenomena in the retention. The possibilities of the method are illustrated from an experiment on the separation of uranium and thorium chelates by gaseous phase chromatography and the quantitative determination of metals. (author)