Determination of the surface area of silver sols based on the rate of the electrocatalytic oxidation of N,N-dimethyl-p-phenylenediamine with chloropentaamine-cobalt(III) chloride

The rate of the electrocatalytic reaction between N,N-dimethyl-p-phenylened iamine and the cobalt(III) complex [Co-III(NH3)(5)Cl](2+) is proportional t o the surface area of silver which acts as catalyst. For a monodisperse col loid the surface area can be calculated from the size of the particles. Thu s, a calibration line can be obtained by carrying out several measurements with the same silver sol but in different concentration. Silver sols of bot h large particles (4.6 mum diameter) and small particles (22.6 nm) were use d. These sols were prepared by reduction of silver nitrate with ascorbic ac id and borohydride respectively. The calibration line allows the determinat ion of the blank surface area of silver sols from the catalytic acceleratio n of the chosen standard redox reaction. (C) 2001 Elsevier Science B.V. All rights reserved.