The corrosion rate of copper in laboratory tests is shown to be a sensitive function of relative humidity, sulfur dioxide, hydrogen sulfide, ozone, hydrogen chloride, and chlorine concentrations. Observed indoor corrosion rates obey log normal statistics over the field population of this study. Also, the observed indoor rates correlate reasonably well with the measured reduced sulfur concentrations ( H2S , S8 ). The corrosion rate of silver is shown not to be humidity dependent. Hydrogen sulfide, ozone, chlorine, and hydrogen chloride concentrations substantially influence its corrosion rate. The observed indoor rates obey log normal statistics and correlate well with the reduced sulfur gas concentration. In contrast to copper, where indoor rates are 1% of outdoor values, silver often corrodes faster indoors than outdoors. Its sensitivity to sulfur gases and insensitivity to relative humidity is proposed as a plausible explanation for these findings. It is proposed that metallic silver is stable in polluted acidic atmospheric environments and therefore is the dominant surface species while Cu2O is present on the surface of copper. The thermochemistry and kinetics of these two surfaces will control the stability of silver and copper, respectively, in the presence of pollutants.

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Plants of wheat, ryegrass, red clover, white clover, and N eptunia amplexicaul'is (a selenium accumulator) were grown in nutrient solutions containing 75Se-selenite ion. The uptake of 75Se was measured and the root and shoot tissues fractionated to examine the products of selenite assimilation.Over a period of 10 days the uptake of 75Se-selenite from culture solutions was of a similar order (expressed per gram fresh weight) for all five species.Characteristic differences were observed between species in the distribution of 75Se in different fractions. The highest ethanol-soluble concentration of 75Se was found in N eptunia, in which at least two unidentified seleno-compounds were present in appreciable amounts. Selenite was predominant in the ethanol extracts of wheat, whereas those from the pasture species contained selenium analogues of several common sulphur-containing metabolites.An appreciable unidentified fraction was present in ryegrass extracts.Aqueous extracts made after alcohol extraction contained selenite, as well as material which was immobile in chromatographic and electrophoretic systems and was probably elemental Se.Extensive protein incorporation of 75Se in seleno-amino acids was observed in ryegrass, wheat, red clover, and'white clover. Protein incorporation of 75Se occurred to a much smaller extent in N eptunia.