nitric acid (HNO3) /nī″trik/ [Gk, nitron, soda; L, acidus, sour] , a colorless, highly corrosive liquid that may give off suffocating brown fumes of nitrogen dioxide on exposure to air. Traces of nitric acid may be found in rainwater during a thunderstorm. Commercially prepared nitric acid is a powerful oxidizing agent used in photoengraving and metallurgy; in the manufacture of explosives, fertilizers, dyes, and drugs; and occasionally as a cauterizing agent for the removal of warts. Organic nitrates or polyol esters of nitric acid such as nitroglycerin and amyl nitrite are effective vasodilators often used in relieving angina, but exactly how they function in dilating arterial and venous smooth muscle is not yet understood. Historically known as aqua fortis.
