A clear, colorless, sparkling liquid or a transparent orthorhombic crystal; H₃PO₄(orthophosphoric acid), depending on the concentration and the temperature. At ordinary atmospheric temperature (20 degrees C), the 50% and 75% acids are mobile liquids, the 85% acid is syrupy, and the 100% acid is in crystals; specific gravity, 1.834 (at 18 degrees C); melting point, 42.35 degrees C; boiling point, 260 degrees C; soluble in water and in alcohol; and very corrosive to ferrous metals and alloys.