Antimony is a silver-white solid with a blue tint and a brilliant lustre. It has a density of 6.697 g/cm and is brittle, and moderately hard (more so than arsenic; less so than iron; about the same as copper). It is stable in air and moisture at room temperature. It is attacked by concentrated nitric acid, yielding the hydrated pentoxide Sb 2 O 5. Aqua regia gives the pentachloride SbCl 5 and hot concentrated sulfuric acid results in the sulfate Sb 2 (SO 4) 3. It is not affected by molten alkali. Antimony is capable of displacing hydrogen from water, when heated: 2 Sb + 3 H 2 O → Sb 2 O 3 + 3 H 2. It melts at 631 °C. Antimony is a semimetal with an electrical conductivity of around 3.1 × 10 S•cm and a band overlap of 0.16 eV. Liquid antimony is a metallic conductor with an electrical conductivity of around 5.3 × 10 S•cm.