Polyphosphate

Polyphosphates are the condensation products of salts of ortho- phosphoric acid ( H3PO4) with the general empirical formula M'n 2 P n O 3n 1 and the structure

M' -O- [P (OM ') ( O)-O ] n- M'. (M ' = monovalent metal )

The polyphosphates are (actually counted oligo ) phosphates and very often the short chain. Cyclic polymers are referred to as meta. The degree of polymerization can be several thousand.

Examples

With n = 3: adenosine triphosphate ( ATP), triphosphate Na5P3O10

With n = 15 to 20: ( NaPO 3 ) n; often carries the incorrect name hexametaphosphate.

With n = hundreds to thousands: Volutin (stabilized with Ca2 , Mg2 ) in prokaryotes and in Acidocalcisomen in single-cell eukaryotes.

Use

( NaPO 3 ) 15-20 was formerly principal component (next Metaphospaten ) Calgon ™, a product for softening water for household appliances. The chemical often bears the incorrect name hexametaphosphate.

Polyphosphates are used in the food industry as complexing agents, emulsifying salts, firming agents and stabilizers. Sodium, potassium, sodium, calcium and calcium polyphosphate are approved for certain foods, each with different maximum quantity restrictions in the EU as a food additive under the E number 452. After the addition approval regulations, these are - for the most approved phosphates largely uniform - individual specifications for a wide range with many different types of food. The approved maximum amounts vary from about 0.5 to 5 usually up to 50 grams per kilogram ( in beverage whiteners for vending machines ) or the lack of a fixed restriction ( quantum satis - as required in food supplements). Phosphorus is in hyperactivity suspected of causing allergic reactions and osteoporosis. It has a permitted daily dose of 70 milligrams per kilogram of body weight for the total amount of recorded phosphoric acid and phosphates total set.

Biological functions

All eukaryotic and prokaryotic cells contain polyphosphates. In bacteria and yeasts, the polymers of energy storage used and stored in Acidocalcisomen. Platelets contain homologous polyphosphate -storing structures called dense granules ( dense granules ) that are polyphosphates - rich. Platelet activation results in the secretion of the polymers, then the start of the activation of a blood coagulation factor XII ( Hageman factor, FXII ) the formation of fibrin and the release of the inflammation mediator, bradykinin and act as a procoagulant and proinflammatory.

Properties

Polyphosphatmoleküle are labile. A hydrolysis is promoted by increases in temperature ( 60-70 ° C), a lowering of the pH ( pH 3.5-4 ), the presence of cations, or in which they are by raising the ionic strength of the medium itself.