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A quartic equation of state (EOS) [Yun et al., Fluid Phase Equilibr. 2001; 187-188: 275-298] is used for predicting critical properties of pure substances. Parameters in the EOS are rewritten as functions of temperature (T in K), and there are totally eleven substance-specific constants in the functions for each substance. Data of few experimental points including saturated vapour pressure, saturated liquid molar volume and evaporation enthalpy at some temperatures are required in this study to determine the substance-specific constants in the EOS, while the knowledge of molecular structure is not necessary. (2001)) est utilisée pour prédire les propriétés critiques des substances pures. Les paramètres de l'équation d'état sont réécrits comme des fonctions de la température (T, en K) et il y a un total de onze constantes propres aux substances dans les fonctions pour chaque substance. Les données de quelques points expérimentaux comprenant la pression de vapeur saturante, le volume molaire de la solution saturée et l'enthalpie d'évaporationà certaines températures sont requises dans cetteétude dans le but de déterminer les constantes propres aux substances dans l'équation d'état, alors que la connaissance de la structure moléculaire n'est pas nécessaire.

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A two-step process and a direct alkaline transesterification process in preparation for cogeneration˛-tocopherol and biodiesel (fatty acid methyl esters, FAME) from cottonseeds were studied in this article. The effects of some factors on recovery of˛-tocopherol and conversion of cottonseed oil (triacylglycerols, TAGs) to biodiesel in the two processes were systematically studied by single factor experiments and orthogonal design method. In the two-step process,˛-tocopherol and biodiesel were produced from extraction with two-phase solvent followed by base-catalysed transesterification. Approximately 95.5% TAGs was converted into biodiesel, and 1.008 mg/g (wet basis)˛-tocopherol was detected on the condition: 1:3 petroleum ether/methanol volume rate, 40 • C extraction temperature; 7:1 methanol/cottonseed oil molar ratio, 1.1% KOH (w/v) concentration in methanol and 60 • C esterification temperature. And in the direct alkaline transesterification reaction, 98.3% conversion of TAGs and 0.986 mg/g content of˛-tocopherol could be achieved at 60 • C in 2 h. Both of the two processes were feasible from the economic point of view for further utilisation of cottonseed.

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