Characteristics: Hard, brittle, gray solid. Not found native. High electrical conductivity. Soluble in a mixture of nitric acid and hydrofluoric acid. Low toxicity. Corroded by seawater. Oxidizes in air at 400 °C, the rate increasing rapidly with temperature.
Hazards: Finely divided form is highly flammable and may ignite spontaneously. Tolerance (as W) (insoluble compounds): 5 mg/m3 of air; soluble compounds, 1 mg/m3 of air.