Small light gray powder. A strong reduction. Usually contain a small amount of zinc oxide. Relative density: 7.133 (25 ℃) Melting point: 419.58 ℃ Boiling point: 907 ℃ in air ignition point: about 500 ℃ explosive limit: lower limit of 420 g / m maximum explosion pressure: 34.3 cattle / cm latent heat of vaporization: 114.8 kJ / mole vapor pressure: 133.3 kPa (487 ℃)