What happens when H3PO3 is heated

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Representation: Oxygen acids of phosphorus is represented by the reaction of phosphorus (III) chloride or phosphorus (III) oxide with water:

Phosphonic acid,, is the tautomeric form of phosphorous acid. The tautomeric equilibrium between phosphonic acid, with a non-acidic atom directly bonded to phosphorus, and phosphorous acid,, is completely on the side of the dibasic phosphonic acid for the free acid:

Organyl derivatives (esters) are known of both forms of the acid. The pure acid can be isolated in the form of colorless, easily water-soluble crystals (melting point: 74).

The dissociating in two stages forms two series of salts: the primary phosphonates (hydrogen phosphonates, hydrogen phosphites),, and the secondary phosphonates (phosphonates, phosphites),. Alkali phosphonates are easily soluble in water, other salts of phosphonic acid are sparingly soluble.

Phosphonic acid is easily oxidized to phosphoric acid,,. In relation to silver ions and other more noble metal cations, for example, it already acts as a reducing agent in an aqueous solution:

When the acid is heated, disproportionation to phosphoric acid and phosphine occurs:

Use: is widely used as a reducing agent. However, the organyl derivatives of the acid, e.g. the phosphonic acid esters, or the phosphorous acid esters, which are used as stabilizers (antioxidants) in plastics, rubber products and lubricating oils or as starting materials for insecticides and veterinary drugs, are of greater importance.