a. Chem. [f. L. quinqui- five- + valent as in equivalent, quadrivalent.] Capable of combining with five univalent atoms; pentavalent.
1877. Watts, Fownes’ Chem., I. 256. Quinquivalent elements, or Pentads.
1880. Cleminshaw, trans. Wurtz’ Atom. The., 229. It is quinquivalent in chloric acid.
1885. Remsen, Org. Chem. (1888), 209. In contact with certain substances it [the nitrogen] becomes quinquivalent.
