Salt, Chemical, is a compound that results when a base neutralizes an acid. In this reaction, the metal in the base displaces the hydrogen in the acid. For example, ordinary table salt, sodium chloride (NaCl), is formed when the base sodium hydroxide (NaOH) neutralizes hydrochloric acid (HCl). The salt calcium carbonate is formed when the base calcium hydroxide neutralizes carbonic acid. See Neutralization .
Salts are among the most important chemical compounds. They are used in making many industrial and agricultural chemicals. For example, sodium chloride is used in making chemicals needed in the manufacture of rayon, soap, and many other products. The salt ammonium nitrate is used in fertilizers to add nitrogen to soil. Some metals, including sodium and potassium, are extracted from salts. Plants and animals need various salts to stay healthy. For example, the salts sodium chloride and potassium chloride supply ions (electrically charged atoms) needed by nerve cells.
Earth’s crust contains many salts. The most abundant salt, sodium chloride, is found in large land deposits and in the ocean. The salt calcium carbonate is found in limestone and in the shells of sea animals. Well-known natural salt deposits include Great Salt Lake in Utah and beds of borax in Nevada.
The salt that is formed when a base completely neutralizes an acid is called a normal salt. Sodium sulfate (Na2SO4), also known as Glauber’s salt, is a normal salt. Incomplete neutralization may produce either an acid salt or a basic salt. Acid salts contain hydrogen ions, as in sodium bisulfate (NaHSO4). Basic salts contain hydroxyl radicals, as in basic lead chloride (Pb[OH]Cl).
A salt crystal contains positive and negative ions in a regular, repeating arrangement. This arrangement is called an ionic lattice. When the salt crystal dissolves in water, these ions are released and move about freely in the solution. A simple salt, such as sodium chloride, is made up of only two kinds of ions. One ion is positive, and the other is negative. When two simple salts form crystals, the resulting substance is called a double salt. Alum, a double salt of aluminum sulfate and potassium sulfate, is used to make cement and to harden plaster casts (see Alum ).
