FORMATION OF COLLOIDAL GOLD WITH ACETONE- DICARBOXYLIC ACID IN AQUEOUS-PHASE

The reduction of chloroauric acid with acetone-dicarboxylic acid in th e aqueous phase was measured by a spectrophotometer. The rate of decre ase in chloroauric acid concentration was obtained from the time cours es of absorbance at 210 nm. The rate was proportional to both concentr ations of chloroauric acid and acetone-dicarboxylic acid. As the activ ation energy of the rate constant was obtained as - 21.2 kJ/mol, the p rocess was deduced to be a nucleation process. The wave length of maxi mum absorbance of the colloidal gold formed was 530nm. The time cource of the absorbance at 530 nm had an induction time and was expressed b y a sigmoidal curve. The induction period decreased with concentration s of both chloroauric acid and acetone-dicarboxylic acid and with temp erature. The activation energy of the induction period was obtained as 85 kJ/mol. Growth of colloidal gold occurs in this induction period.