Effect of the addition of alcoholic miscible co-solvents on the properties of ascorbic acid in its supersaturated aqueous solution by Waid Omar and Joachim Ulrich

Crystal Research and Technology

Cryst. Res. Technol. 41, 431 (2006) - Abstract -

Effect of the addition of alcoholic miscible co-solvents on the properties of ascorbic acid in its supersaturated aqueous solution

Waid Omar and Joachim Ulrich*

Tafila Technical University, Department of Natural Resources and Chemical Engineering, Tafila, Jordan
*Martin-Luther-Universität Halle-Wittenberg, FB Ingenieurwissenschaften, Institut für Verfahrenstechnik/ TVT, 06099 Halle, Germany

Keywords	ascorbic acid, solvent effect, UNIFAC, driving force, metastable zone
PACS	82.60.Lf
DOI	10.1002/crat.200510601

In the current study results are presented on the influence of the solvent composition on the properties of ascorbic acid in its supersaturated aqueous solutions. In examining the role of addition of 20 wt.% ethanol or 1-propanol to the ascorbic acid water system, it was emphasized that the solubility is reduced significantly due to the addition of alcoholic co-solvents. Using UNIFAC simulation, tt was found that the addition of alcoholic co-solvents to the aqueous ascorbic acid solution and in the state of equilibrium reduces significantly the activity coefficient of ascorbic acid. In the supersaturated ascorbic acid solutions, the calculated activity ratio (γ/γ_eqm) by means of UNIFAC simulations as a function of supersaturation ratio (x/x_eqm) point out that the addition of alcoholic co solvents lead to an increase in the thermodynamic driving force. The measured metastable zone widths in the presence of alcoholic co-solvents displays that alcoholic co-solvents acts on increasing the width of the metastable zone.

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