Scheele and Bergman suggested the possibility of obtaining a new metal by reducing this acid. Important deposits of tungsten occur in California, North Carolina, South Korea, Bolivia, U.S.S.R., and Portugul. Natural tungsten contains five stable isotopes. Twelve other unstable isotopes are recog- nized. The metal is obtained commercially by reducing tungstic oxide with hydrogen or cargon.
Pure tungsten is a steel gray to tin-white metal.
Very pure tungsten can be cut with a hacksaw, and can be forged, spun, drawn, and extruded. The impure metal is brittle and can be worked only with difficulty. Tungsten has the highest melfing point and lowest vapor pressure of all metals, and at temperatures over 16500C has the highest tensile strength. The metal oxidizes in air and must be protected at elevated tempera- tures. It has excellent corrosion resistance and is attacked only slightly by most mineral acids.