Pentasodium triphosphate

Structural formula
General
Surname	Pentasodium triphosphate
other names	Sodium tripolyphosphate Pentabasic sodium triphosphate PENTASODIUM TRIPHOSPHATE ( INCI )
Molecular formula	Na 5 P 3 O 10
Brief description	white, odorless solid
External identifiers / databases
CAS number 7758-29-4 EC number 231-838-7 ECHA InfoCard 100,028,944 PubChem 24455 Wikidata Q29145
properties
Molar mass	367.86 g mol −1
Physical state	firmly
density	2.52 g cm −3
Melting point	622 ° C (decomposition)
solubility	easily in water (145 g l −1 at 25 ° C)
safety instructions
GHS labeling of hazardous substances no GHS pictograms H and P phrases H: no H-phrases P: no P-phrases
Toxicological data	3120 mg kg −1 ( LD 50 ,  rat ,  oral )
As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions .

Pentasodium triphosphate (also sodium tripolyphosphate ) is a colorless sodium salt of the anion triphosphate, belongs to the phosphates and has the empirical formula Na ₅ P ₃ O ₁₀ . The name triphosphate is occasionally used in place of pentasodium triphosphate. Triphosphates are also parts of important organic compounds such as adenosine triphosphate .

synthesis

Pentasodium triphosphate is formed by condensation of ortho-phosphoric acid :

${\displaystyle \mathrm {6\ H_{3}PO_{4}+5\ Na_{2}CO_{3}\longrightarrow } }$ ${\displaystyle \mathrm {2\ Na_{5}P_{3}O_{10}+5\ CO_{2}+9\ H_{2}O} }$

In the laboratory it is obtained from sodium phosphate and sodium diphosphate :

${\displaystyle \mathrm {NaPO_{3}+Na_{4}P_{2}O_{7}\longrightarrow Na_{5}P_{3}O_{10}} }$

Production from sodium trimetaphosphate is also possible :

${\displaystyle \mathrm {Na_{3}P_{3}O_{9}+2\ NaOH\longrightarrow Na_{5}P_{3}O_{10}+H_{2}O} }$

properties

Pentasodium triphosphate is a hygroscopic, white, odorless, non-flammable solid that is easily soluble in water. It decomposes from a temperature of 622 ° C, producing phosphorus oxides and sodium oxide . Its aqueous solution has an alkaline reaction.

use

INCI -compliant declaration of the ingredients of a toothpaste

Triphosphates are used in detergents to soften the water and thus support the surfactants in their effectiveness. The triphosphate anions of pentasodium triphosphate, for example, form stable and water-soluble compounds with calcium and magnesium ions. It is therefore a good complexing agent that prevents poorly soluble compounds, so-called " lime soaps ", from forming from the alkaline earth metals , which then settle on the heating rods in washing machines or on the laundry and thus the effect of the detergent , the surfactants . In Switzerland is forbidden to use of phosphates in detergents.

Modern sewage treatment plants hold back most of the phosphates contained in wastewater and required as nutrients by microorganisms and plants. Nevertheless, a large proportion of detergent phosphates are nowadays replaced by zeolite A - a sodium aluminum silicate - in order to prevent overfertilization of surface waters by phosphates. However, in machine dishwashing detergents, phosphates are still used as softeners.

Pentasodium triphosphate is used in food technology as a complexing agent , acid regulator , melting salt , firming agent or stabilizer . Pentasodium triphosphate is approved together with pentapotassium triphosphate in the EU as a food additive under the common number E 451 for certain foods with different maximum quantity restrictions. According to the Additive Admissions Ordinance , these are - largely uniform for most of the approved phosphates - individual specifications for a wide range of numerous different types of food. The maximum permitted quantities vary from 0.5 to 50 grams per kilogram (in creamer for vending machines) or the lack of a fixed limit ( quantum satis - as required, for food supplements and sometimes for chewing gum). Phosphates are suspected of causing hyperactivity , allergic reactions and osteoporosis . A permissible daily dose of 70 milligrams per kilogram of body weight was set for the total amount of phosphoric acid and phosphates ingested.

Individual evidence

1. ↑ Entry on PENTASODIUM TRIPHOSPHATE in the CosIng database of the EU Commission, accessed on February 16, 2020.
2. ↑ ^{a b c d} data sheet penta sodium triphosphate (PDF) from Merck , accessed on January 19, 2011.
3. ↑ ^{a b c} Entry on pentasodium triphosphate in the GESTIS substance database of the IFA , accessed on August 3, 2019(JavaScript required) .
4. ↑ G. Brauer (editor), Handbook of Preparative Inorganic Chemistry 2nd edition, volume 1, Academic Press 1963, pp. 547-8.
5. ^ Ernst Guggolz: Phosphates in dishwashing detergents - a blessing and a curse. Gesellschaft Deutscher Chemiker, press release from January 26, 2012 from Informationsdienst Wissenschaft (idw-online.de), accessed on August 24, 2015.