Orthophosphoric

Part of speech: adjective

Definitions

1. Relating to or containing orthophosphoric acid, the most common form of phosphoric acid with the formula H3PO4
2. Describing a compound derived from orthophosphoric acid, a triprotic acid used in fertilizers, detergents and rust removers
3. Pertaining to the widely used mineral acid whose formula is H3PO4 and which is central to phosphate chemistry

Etymology: Orthophosphoric acid is a chemistry term built from two older parts. "Ortho-" comes from Ancient Greek "orthós", meaning straight, upright or correct, and in chemistry it marks the most fully hydrated form of an acid among several that share the same base. "Phosphoric" describes an acid containing phosphorus, and the element's name is itself Greek in spirit, from "phosphoros", meaning light-bringer, a reference to its glow. The compound is therefore a coinage rather than an ancient word. Chemists needed a way to distinguish between closely related phosphorus acids, and prefixing "ortho-" to "phosphoric" gave a precise label for the standard form. The Greek element "orthós" thus travels a long way from its original sense of "straight" to name one specific molecular structure.