tetrasodium

Tetrasodium is a chemical naming prefix used to indicate a salt in which four sodium ions accompany a negatively charged ligand or anionic moiety. It is not a single substance by itself but rather a descriptor that appears in the names of certain four-sodium salts, typically when four acidic protons have been replaced by sodium ions in a polyprotic compound.

Common examples include tetrasodium EDTA and tetrasodium pyrophosphate. Tetrasodium EDTA refers to the tetra-sodium salt of ethylenediaminetetraacetic acid, in which four Na+ ions balance the charge of the EDTA4− anion. Tetrasodium pyrophosphate is the sodium salt form of pyrophosphoric acid, where four sodium ions balance the pyrophosphate anion. These salts are usually highly soluble in water, with properties reflecting their role as counterions to multivalent anions.

Uses and applications of tetrasodium salts are broad. Tetrasodium EDTA is a widely used chelating agent in detergents, cosmetics, and some pharmaceuticals, where it binds metal ions such as calcium and magnesium to improve cleaning efficiency, color stability, and colorfastness. Tetrasodium pyrophosphate serves as a buffering agent, sequestrant, or leavening aid in foods and as a water-softening or buffering additive in cleaners. In both cases, the four sodium ions influence solubility, pH behavior, and the overall chemical reactivity of the salt.

In nomenclature, the term tetrasodium highlights the four sodium counterions and is typically contrasted with other sodium salt forms, such as disodium or monosodium variants, depending on how many acidic hydrogens have been replaced.