Sodium chloride (NaCl) is an ionic compound consisting of equal proportions of sodium and chlorine. It is commonly known as salt or table salt and is a major component of the extracellular fluid that makes up most of the body’s cells. It is one of the primary electrolytes in this compartment, cooperating with other ions to regulate water balance. Disorders of the cell’s sodium content are associated with loss or excess of water and can lead to cellular dehydration and even death.
Despite its familiarity, the chemical is not very well understood at the molecular level. Its solid structure resembles a face-centered cubic crystal. In the crystal, larger chloride ions occupy octahedral voids and smaller sodium ions occupy cubes in an interpenetrating arrangement. These ions are bonded to each other by strong hydrogen bonds that form the NaCl lattice. The NaCl molecule is also hygroscopic, absorbing moisture that can alter its physical properties.
Sodium chloride is widely used in industrial processes and is the principal source of salt for deicing roadways in cold weather. Sodium is also an essential element in living organisms, being found in the blood plasma and in most of the other body fluids. It plays important roles in acid-base equilibrium, nerve impulse transmission and muscle relaxation. It helps the body absorb glucose and assists in a number of other metabolic processes. Its concentration in the extracellular fluid regulates blood pressure and helps maintain concentration differences across cell membranes.