Disodium dihydrogen diphosphate
Structural formula | |||||||||||||||||||
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General | |||||||||||||||||||
Surname | Disodium dihydrogen diphosphate | ||||||||||||||||||
other names |
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Molecular formula | Na 2 H 2 P 2 O 7 | ||||||||||||||||||
Brief description |
colorless and odorless powder |
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properties | |||||||||||||||||||
Molar mass | 221.9 g mol −1 | ||||||||||||||||||
Physical state |
firmly |
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density |
1.86 g cm −3 |
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Melting point |
220 ° C (decomposition) |
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solubility |
moderate in water (120 g l −1 at 20 ° C) |
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safety instructions | |||||||||||||||||||
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As far as possible and customary, SI units are used. Unless otherwise noted, the data given apply to standard conditions . |
Sodium acid pyrophosphate Na 2 H 2 P 2 O 7 , a sodium salt of diphosphoric acid , belongs to the group of diphosphates . It is used as a food additive , among other things , and is often incorrectly referred to as disodium diphosphate .
Appearance and properties
Na 2 H 2 P 2 O 7 can be produced from sodium dihydrogen phosphate by heating it for several hours at about 210 ° C:
Alternatively, the representation takes place by reacting the diphosphoric acid with two equivalents of sodium hydroxide solution .
Above this temperature, the long-chain Maddrell salt (NaPO 3 ) n or sodium trimetaphosphate Na 3 P 3 O 9 is formed .
The salt is easily soluble in water and is slightly acidic .
The hexahydrate of the compound has a monoclinic crystal structure with the space group C 2 / c (space group no. 15) .
use
In food chemistry , Na 2 H 2 P 2 O 7 is used as an additive for baking powder under the name E 450a ; as it reacts acidic, it promotes the decomposition of the leavening agents .
Since, as pyrophosphate, it strives to absorb water from its environment and thereby to regress the above-mentioned sodium dihydrogen phosphate
it is also used as a dehydrating preservative for food.
literature
- AF Holleman , E. Wiberg , N. Wiberg : Textbook of Inorganic Chemistry . 102nd edition. Walter de Gruyter, Berlin 2007, ISBN 978-3-11-017770-1 .
Individual evidence
- ↑ Entry on DISODIUM PYROPHOSPHATE in the CosIng database of the EU Commission, accessed on February 11, 2020.
- ↑ a b c d e f Entry on disodium dihydrogen pyrophosphate in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
- ^ RN Bell: Sodium pyrophosphates . In: Ludwig F. Audrieth (Ed.): Inorganic Syntheses . tape 3 . McGraw-Hill, Inc., 1950, pp. 98-101 (English).
- ^ DEC Corbridge: Phosphorus Chemistry, Biochemistry and Technology, Sixth Edition . CRC Press, 2016, ISBN 978-1-4398-4089-4 , pp. 234 ( limited preview in Google Book search).
- ^ Arthur DF Toy: The Chemistry of Phosphorus Pergamon Texts in Inorganic Chemistry . Elsevier, 2016, ISBN 978-1-4831-3959-3 , pp. 513 ( limited preview in Google Book search).