Beryllium is a steel-gray, very hard, light metal. It is brittle at ordinary temperatures and ductile at red heat. It has a density of 1.8477, a melting point of 1285 °C, a boiling point of 2477 °C. Its electrical conductivity is 1/12 of that of copper. Beryllium has a metallic luster in dry air at ordinary temperatures and the powder burns on heating to form BeO. In H2O, Be is coated with a thin skin of hydroxide which has a solubility product of 2.7 × 10−19. Aqueous solutions of beryllium salts are colorless and have a sweet taste.