Mixed acid - a colourless or light yellow liquid, with a sharp, choking smell; caustic, toxic. It has oxidising and nitrating properties. It fumes in air and gives off nitrogen dioxide, sulphur oxides and acid vapours. The liquid is non-flammable. It dissolves in water giving off substantial amounts of heat. Contact between mixed acid and most metals should be avoided. In contact with organic materials, it may result in their combustion. Mixed acid reacts dangerously with metallic elements and reducing agents. In contact with skin, it causes dangerous burns, and on penetrating the subcutaneous layer and muscle, it causes necrosis.