Formation of Colloidal Gold with Acetone-Dicarboxylic Acid in Aqueous Phase

Abstract

The reduction of chloroauric acid with acetone-dicarboxylic acid in the aqueous phase was measured by a spectrophotometer. The rate of decrease in chloroauric acid concentration was obtained from the time courses of absorbance at 210 nm. The rate was proportional to both concentrations of chloroauric acid and acetone-dicarboxylic acid. As the activation energy of the rate constant was obtained as -21.2 kJ/mol, the process was deduced to be a nucleation process. The wave length of maximum absorbance of the colloidal gold formed was 530 nm. The time cource of the absorbance at 530 nm had an induction time and was expressed by a sigmoidal curve. The induction period decreased with concentrations of both chloroauric acid and acetone-dicarboxylic acid and with temperature. The activation energy of the induction period was obtained as 85 kJ/mol. Growth of colloidal gold occurs in this induction period. © 1995, The Society of Chemical Engineers, Japan. All rights reserved.