Potassium phosphate
| Crystal structure | ||||||||||
|---|---|---|---|---|---|---|---|---|---|---|
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| __ K + __ P 5+ __ O 2− | ||||||||||
| Crystal system |
orthorhombic |
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| Space group |
Pnma (No. 62) |
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| Lattice parameters |
a = 1.123772 nm, b = 0.810461 nm and c = 0.592271 nm |
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| General | ||||||||||
| Surname | Potassium phosphate | |||||||||
| other names |
Tripotassium phosphate |
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| Ratio formula | K 3 PO 4 | |||||||||
| Brief description |
white, deliquescent, granular powder |
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| External identifiers / databases | ||||||||||
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| properties | ||||||||||
| Molar mass | 212.28 g mol −1 | |||||||||
| Physical state |
firmly |
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| density |
2.56 g cm −3 |
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| Melting point |
1340 ° C |
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| solubility |
easily in water (508 g l −1 at 25 ° 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 . | ||||||||||
Potassium phosphate is the potassium salt of phosphoric acid . It is mainly used in laundry detergents.
Extraction / representation
Potassium phosphate is also formed when Thomas slag is heated with coal and potassium sulfate .
properties
Potassium phosphate dissolves in water with an alkaline reaction. The anhydrate crystallizes in the orthorhombic space group Pnma (space group no. 62) with the lattice constants a = 1.123772 nm, b = 0.810461 nm and c = 0.592271 nm with four formula units each in one unit cell. There is also a high-temperature modification of this with a cubic structure with a = 0.811 nm.
Manufacturing
It is not possible to obtain anhydrous potassium phosphate by crystallization from aqueous solution, but the pure octahydrate is obtained by introducing ammonia into the solution.
use
Phosphates are used as additives in detergents . They are capable of complex formation with multivalent metal ions (Mg 2+ which etc.) Hardness reduced. Their use is now banned in some countries (including Switzerland). Phosphates are also used as mineral fertilizers .
It is used as an acidity regulator in food technology. Together with primary (KH 2 PO 4 ) and secondary potassium phosphate (K 2 HPO 4 ), it is approved in the EU as a food additive under the common number E 340 (“ potassium phosphate ”) 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 amounts 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). Phosphorus is 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.
Biological importance
The consequence of the use in detergents is a greater supply of nutrients in water . This results in increased algae growth, which can lead to the overturning of a body of water.
Individual evidence
- ↑ a b V. I. Voronin et al. : Crystal Structure of the Low-Temperature Form of K 3 PO 4 . In: Inorganic Materials . tape 42 , no. 8 , August 2006, p. 908-913 , doi : 10.1134 / S0020168506080206 .
- ↑ a b c Entry on potassium phosphates. In: Römpp Online . Georg Thieme Verlag, accessed on July 15, 2014.
- ↑ a b data sheet potassium phosphate at AlfaAesar, accessed on March 14, 2010 ( PDF )(JavaScript required) .
- ↑ a b c Entry on tripotassium orthophosphate in the GESTIS substance database of the IFA , accessed on January 8, 2018(JavaScript required) .
- ↑ R. Hoppe, HM Seyfert: For the knowledge of anhydrous orthophosphates of the higher alkali metals: K 3 PO 4 Rb 3 PO 4 , Cs 3 PO 4 . In: Journal of Nature Research B . tape 28 , no. 7–8 , August 1973, pp. 507-508 , doi : 10.1515 / znb-1973-7-828 .
- ↑ G. Brauer (Ed.): Handbook of Preparative Inorganic Chemistry 2nd edition, volume 1, Academic Press 1963, page 545.