Nitrates are salts formed by the reaction of nitric acid with metals. It is composed of metal ions (or ammonium ions) and nitrate ions. Nitrate is a general term for the compounds derived from nitric acid, which is usually composed of metal ions or ammonium ions and nitrate ions. Nitrates are ionic compounds. Almost all nitrate is easily soluble in water, only urea nitrate is slightly soluble in water, while bismuth nitrate is difficult to dissolve in water, so nitrate can not be precipitated by most other cations.