The major use for phosphorus is as an essential nutrient for all plant and animal life, commonly as phosphate in inorganic fertiliser. At the same time, phosphates and organophosphates are widely used in such diverse applications as detergents, plasticisers, flame-retardants, corrosion inhibitors, pesticides, and scale inhibitors in water heaters and boilers, etc.
A wide variety of small molecular weight esters of phosphates (organophosphates) are made industrially, and vary from highly toxic pesticides to non-toxic plasticisers and surfactants.
Substance name: Total phosphorus
CASR number: Not applicable
Molecular formula: The formula for the orthophosphate ion is (PO4)3-
Synonyms: Total phosphorus is defined for the NPI as compounds that give rise to phosphate ions. This is a very broad group including many natural and anthropogenic substances, either containing phosphate or decomposing into it. These compounds include salts such as trisodium phosphate and calcium hydroxyapatite, and polyphosphates and organophosphates.The vast number and variety of molecular structures making up organic chemistry (that is, compounds based on carbon atoms) is mirrored in the chemistry of compounds based on phosphorus. This variety is based on the orthophosphates and the long-chain polyphosphates, compounds in which phosphate groups are linked by oxygen.
Phosphates: Phosphate salts vary very widely in their solubility, from several percent for solutions of salts such as trisodium phosphate, to micrograms per Litre for calcium hydroxyapatite. In addition, their solubility is strongly affected by the pH of the solution.However, the solubility of phosphate in waters containing hydrated iron(III) oxides is reduced by orders of magnitude, since phosphate binds extremely strongly to the oxide surfaces.
Polyphosphates and organophosphates: These also vary widely in their solubility generally decreasing as the molecular weight increases, and again is very dependent on pH.
Phosphates: Phosphate salts in solution are only partially dissociated at neutral pH. Nevertheless, the degree of dissociation is critically important to its reactivity in not only precipitation/dissolution reactions, but also to the formation of the various organophosphate esters.
Phosphates: Inorganic phosphates are generally chemically unreactive. On the other hand, the formation and hydrolysis of the organophosphates and polyphosphates is critical to their manufacture and/or their function in biological systems, whether this be in maintaining life or in the role of pesticides
The National Pollutant Inventory (NPI) holds data for all sources of phosphorus in Australia.
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