Nitrate
In inorganic chemistry, a nitrate is a salt of nitric acid. In organic chemistry the esters of nitric acid and various alcohols are called nitrates. The nitrate ion is a polyatomic anion with the empirical formula NO3- and a molecular mass of 62.01 daltons; it consists of one central nitrogen atom surrounded by three identical oxygen atoms in a trigonal planar arrangement. The nitrate ion carries a negative one formal charge. Nitrates should not be confused with nitrites, the salts of nitrous acid. Organic compounds containing the nitro functional group (which has the same formula and structure as the nitrate ion save that one of the O2 atoms is replaced by the R group) are known as nitro compounds. Nitrate ions can be toxic. In particular, nitrate toxicosis in humans occurs through enterohepatic metabolism of nitrates to ammonia, with nitrite being an intermediate. Nitrites oxidize the iron atoms in hemoglobin from Ferrous Iron (2+) to Ferric Iron (3+), rendering it unable to carry oxygen. This condition is called methemoglobinemia and can lead to a lack of oxygen in tissues. Methemoglobinemia can be treated with methylene blue. -- Wikipedia.