Nitric acid, other than red fuming appears as a pale yellow to reddish brown liquid with reddish brown vapors and a suffocating odor. Very toxic by inhalation. Corrosive to metals or tissue. Accelerates the burning of combustible material and may cause ignition of flammable materials upon contact. Prolonged exposure to low concentrations or short-term exposure to high concentrations may result in adverse health effects. The density is 12 lb/gal.