Salt (Sodium Chloride) in Foods
Salts are made when an acid and a base react. They are formed by total or partial replacement of hydrogen with a metal. The most common of the salts is formed when sodium hydroxide and hydrochloric acid react, giving sodium chloride and water: \(NaOH + HCl \to NaCl + HOH\) In measuring the presence of salt in foods, a number of methods may be used. Salt dissolves in water; therefore it may be measured in aqueous solution by use of a hydrometer. Another method employs a titration using silver nitrate. In this method, a known normal strength of silver nitrate (AgNO3) is allowed to react with the salt in a food product that has been liberated through a nitric acid (HNO3) digestion. After the salt and silver nitrate have reacted, the nitrate that remains is titrated against a known normal solution of ammonium thiocyanate (NH4SCN) in the presence of a ferric nitrate Fe(NO3)3 indicator. In an excess of ammonium thiocyanate, ferric thiocyanate, FeSCN2+, which has a salmon-colored complex, will form, indicating the end point.
KeywordsAmmonium Nitrate Silver Nitrate Sodium Nitrate Ferric Ammonium Ammonium Thiocyanate
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