Zinc phosphate

Structural formula
General
Surname	Zinc phosphate
other names	Trizinc bis (orthophosphate) Trizinc diphosphate Zinc orthophosphate
Molecular formula	Zn 3 (PO 4 ) 2
Brief description	white odorless solid
External identifiers / databases
CAS number 7779-90-0 14485-28-0 (dihydrate) 7543-51-3 (tetrahydrate) 13847-22-8 (mixture of zinc phosphates) PubChem 24519 Wikidata Q59714
properties
Molar mass	386.11 g mol −1
Physical state	firmly
density	3.75 g cm −3
Melting point	> 900 ° C
solubility	practically insoluble in water
safety instructions
GHS hazard labeling from  Regulation (EC) No. 1272/2008 (CLP) , expanded if necessary Caution H and P phrases H: 410 P: 273-501
Toxicological data	> 5000 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 .

Zinc phosphate is a chemical compound from the group of phosphates and zinc compounds .

Occurrence

Of course, zinc phosphate occurs as a tetrahydrate as a mineral in the form of the orthorhombic hopeite and triclinic parahopeite , as a hydroxide in the form of the mineral tarbuttite and in connection with iron and manganese as phosphophyllite .

Extraction and presentation

Zinc phosphate (as tetrahydrate) can be obtained by reacting zinc oxide with phosphoric acid.

${\displaystyle \mathrm {3\ ZnO+2\ H_{3}PO_{4}+H_{2}O\rightarrow Zn_{3}(PO_{4})_{2}\cdot 4\ H_{2}O} }$

It is also possible to obtain it by reacting zinc sulfate with disodium hydrogen phosphate .

${\displaystyle \mathrm {3\ ZnSO_{4}\cdot 7\ H_{2}O+2\ Na_{2}HPO_{4}\cdot 2\ H_{2}O} }$

${\displaystyle \mathrm {\rightarrow Zn_{3}(PO_{4})_{2}\cdot 4\ H_{2}O+2\ Na_{2}SO_{4}+H_{2}SO_{4}+21\ H_{2}O} }$

properties

Zinc phosphate is a white, odorless solid that is insoluble in water but soluble in dilute mineral acids . In addition to the anhydrous, it also occurs as mono-, di- and tetrahydrate . Zinc phosphate monohydrate, Zn ₃ (PO ₄ ) ₂ · H ₂ O is in the centric space group P 2 ₁ / c (space group no. 14) (C ⁵ _2h ) with four formula units per unit cell and the lattice constants a = 8.696 (6 ), b = 4.891 (2) and c = 16.695 (9) Å and β = 94.94 (3) °. Zinc phosphate dihydrate crystallizes in the central space group P 2 / c (No. 13) (C ⁵ _2h ) and eight formula units with the lattice constants a = 10.451 (7), b = 5.036 (3) and c = 31.437 (15) Å as well β = 92.46 °. Zinc phosphate tetrahydrate is a dimorphic orthophosphate that occurs as orthorhombic hopeite or triclinic parahopeite, three different modifications of the former being known, which differ only in the arrangement of the hydrogen atoms. Parahopeit crystallizes in the central space group P 1 (No. 2) (C ¹ _i ) with one formula unit per unit cell and the lattice constants a = 5.768 (5), b = 7.550 (5), c = 5.276 (5) Å, α = 93.4 °, β = 91.2 ° and γ = 91.4 °. Hopeite crystallizes in the central space group Pnma (No. 62) (D ¹⁶ _2h ) with four formula units per unit cell and the lattice constants a = 10.597 (3), b = 18.318 (8) and c = 5.031 (1) Å. α – Hopeite transforms into other forms at temperatures> 105 ° C, β – Hopeite above 140 ° C and p – Hopeite above 163 ° C. The water-free version is obtained from 250 ° C.

use

Zinc phosphate is used as an anti-corrosive pigment and for the production of dental cements .

Substance evaluation

In 2013, zinc phosphate was included in the EU's ongoing action plan ( CoRAP ) in accordance with Regulation (EC) No. 1907/2006 (REACH) as part of substance evaluation . The effects of the substance on human health and the environment are re-evaluated and, if necessary, follow-up measures are initiated. The uptake of zinc phosphate was caused by concerns about high (aggregated) tonnage and widespread use. The re-evaluation took place from 2013 and was carried out by Romania . A final report was then published that did not recommend any changes to the labeling.

Related links

• Zinc pyrophosphate Zn ₂ P ₂ O ₇
• Dizinc cyclotetraphosphate Zn ₂ P ₄ O ₁₂
• Zinc hydrogen phosphate ZnHPO ₄
• Zinc hydroxide phosphate Zn ₂ (OH) PO ₄

Individual evidence

1. ↑ ^{a b c d e f g} Entry on zinc phosphate in the GESTIS substance database of the IFA , accessed on February 22, 2017(JavaScript required) .
2. ↑ Entry on Trizinc bis (orthophosphate) in the Classification and Labeling Inventory of the European Chemicals Agency (ECHA), accessed on February 1, 2016. Manufacturers or distributors can expand the harmonized classification and labeling .
3. ↑ ^{a b} IUCLID Datasheet of the European chemical Substances Information System (ESIS): trizinc bis (orthophosphate) ( Memento of November 10, 2013 in the Internet Archive ) of February 19, 2000.
4. ↑ Hopeit (Mineral Atlas)
5. ↑ ^{a b} Basic studies on the setting reaction of zinc phosphate cement
6. ^ Process for the production of particulate zinc phosphate. (Free patents online)
7. ↑ Georg Brauer (Ed.), With the collaboration of Marianne Baudler a . a .: Handbook of Preparative Inorganic Chemistry. 3rd, revised edition. Volume II, Ferdinand Enke, Stuttgart 1978, ISBN 3-432-87813-3 .
8. ↑ Zinc phosphate data sheet (PDF; 156 kB) from Gischem.
9. ^ European Chemicals Agency (ECHA): Substance Evaluation Report and Conclusion Document .
10. ↑ Community rolling action plan ( CoRAP ) of the European Chemicals Agency (ECHA): Trizinc bis (orthophosphate) , accessed on March 26, 2019.