Abstract
A considerable amount of work has been reported on the qualitative effects of various addition agents to aqueous and non-aqueous silver electroplating solutions. This thesis reports some quantitative investigations into silver complexes in various solutions. This work has been mainly concerned with the d.c. polarography of silver at silver and platinum electrodes in aqueous and non-aqueous systems. In aqueous systems it was found that silver could be determined quantitatively at a stationary platinum microelectrode over the range 2.5 x 10[-4]M to 2.0 x 10[-3]M, the current-voltage readings were recorded manually. A wave at about -0.55V (versus the molybdenum electrode) in the current-voltage curve of aqueous solutions containing silver nitrate and sulphosalicylic acid using silver and molybdenum electrodes has been shown to be due to complex molybdenum ions produced by a first order exchange reaction at the molybdenum electrode and not to silver ions as reported by previous workers. This wave could be used for the determination of molybdenum and the specific rate constant of the exchange reaction was directly proportional to the area of the molybdenum electrode. Silver reduction was carried out in propylene carbonate, pyridine and N,N-dimethylformamide at a stationary platinum microelectrode, some quantitative work was carried out on the silver perchlorate/propylene carbonate system. The effects of the addition of small quantities of perchloric acid and water, to the above systems were also noted. Adopting a three electrode cell system good S-shaped current-voltage curves were obtained for silver in propylene carbonate and pyridine at a vibrating platinum microelectrode and analysis of these waves for a reversible reaction yielding an insoluble product, showed them to correspond to one electron reductions. Quantitative determinations in propylene carbonate gave good linearity between the diffusion current and the silver concentration from 2.0 x 10[-4] to 7.0 x 10[-3]M. When pyridine was added to the silver perchlorate/propylene carbonate system, the change in the half-wave potential of silver towards the negative side was almost logarithmic with respect to the pyridine concentration and thought to be due to either solvation or a change in characteristic of the electrodeposited silver crystals. Photomicrographs of silver electrodeposition on platinum from pyridine, propylene carbonate and the propylene carbonate/pyridine mixed solvent system are included in this thesis.