TARNISHING OF AG AT NATURALLY-OCCURRING H2S AND SO2 LEVELS

The rate at which Ag tarnishes was measured under laboratory conditions which were realistic with respect to the levels of H2S, SO2 and water vapour found under natural conditions and show the need for caution in designing accelerated tests. The addition of SO2 (2ppm) has no significant effect on the rate of sulphide formation on pure Ag surfaces at the 0·02-0·05ppm H2S level in dry or moist conditions, but nullifies the enhancement of the rate caused by contamination of the Ag surface by Fe. © 1968 Pergamon Press.