Nitrate and nitrite are compounds that contain a nitrogen atom joined to oxygen atoms, with nitrate containing three oxygenatoms and nitrite containing two. In nature, nitrates are readily convertedto nitrites and vice versa. Both are anions, or ions with a negative charge.They tend to associate with cations, or ions with a positive charge, to achieve a neutral charge balance.
Nitrates are used primarily to make fertilizer, but they are also used to make glass and explosives. These compounds also are used in various chemical production and separation processes. Nitrites are manufactured mainly for use as a food preservative, and both nitrates and nitrites are used extensively to enhance the color and extend the shelf life of processed meats.
Nitrates are naturally present in soil, water, and food. In the naturalnitrogen cycle, bacteria convert nitrogen to nitrate, which is taken up by plants and incorporated into tissues. Animals that eat plants use the nitrate to produce proteins. Nitrate is returned to the environmentin animal feces, as well as through microbial degradation of plants and animals after they die. Microorganisms can convert nitrate or the ammonium ion (which is a nitrogen atom combined with four hydrogen atoms) to nitrite; this reaction occurs in the environmentas well as within the digestive tract of humans and other animals. After bacteriaconvert (reduce) nitrate to nitrite in the environment, the nitrogen cycle is completed when they then convert the nitrite to nitrogen.