A silvery white metallic element that belongs to period 6 of the lanthanoids family, with phosphate binding property. Lanthanum, when administered in a salt form, dissociates in acid to release lanthanum ions, which then bind dietary phosphate. This agent inhibits the absorption of phosphate by forming highly insoluble lanthanum-phosphate complexes that reduce concentrations of serum phosphate and calcium phosphate.

Rare metallic element, symbol La, atomic number 57.

The prototypical element in the rare earth family of metals. It has the atomic symbol La, atomic number 57, and atomic weight 138.91. Lanthanide ion is used in experimental biology as a calcium antagonist; lanthanum oxide improves the optical properties of glass.