Aluminium phosphate

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Aluminium phosphate
Other names	Aluminium monophosphate Phosphoric acid, aluminum salt (1:1)
Identifiers
CAS number	7784-30-7 Y
PubChem	64655
RTECS number	TB6450000
SMILES	O=P12O[Al](O1)O2
InChI	1/Al.H3O4P/c;1-5(2,3)4/h;(H3,1,2,3,4)/q+3;/p-3/rAlO4P/c2-6-3-1(4-6)5-6
InChI key	ILRRQNADMUWWFW-ITXURHEJAW
ChemSpider ID	21172744
Properties
Molecular formula	AlPO4
Molar mass	121.9529 g/mol
Appearance	white, crystalline powder
Density	2.566 g/cm3, solid
Melting point	1800 °C
Boiling point	decomposes
Solubility in water	insoluble
Solubility	very slightly soluble in HCl and HNO3
Refractive index (nD)	1.546 [1]
Hazards
EU classification	Xi
R-phrases	R36/37/38
S-phrases	S26
NFPA 704	0 2 0
LD50	4640mg/kg (rat, oral) > 4640 mg/kg (rabbit, dermal)
Y (what is this?)  (verify) Except where noted otherwise, data are given for materials in their standard state (at 25 °C, 100 kPa)
Infobox references

Aluminium phosphate (AlPO₄) is a chemical compound. It is used in cake mixes and in some baking powders as a leavening agent to help baked goods rise. Medicinally it is used as adsorbent for toxoid.

It is also used industrially as a high-temperature dehydrating agent. When heated to decomposition, aluminium phosphate decomposes into aluminium oxide and phosphorus pentoxide, the latter of which is very effective at absorbing water.^[2][3] Phosphorus pentoxide may be useful in a number of applications including the production of ketene from acetic acid, although this process is rather dangerous and may yield a significant amount of byproducts.^[4]

4AlPO₄ → 2Al₂O₃ + P₄O₁₀^[5]

-

6CH₃COOH + P₄O₁₀ → 4H₃PO₄ + 6CH₂CO

CH₂CO + CH₃COOH → (CH₃CO)₂O

Occurrence

Although it is unstable to heat, in geologically stable regions like Australia and Southern Africa, alumiunium phosphate is generally the most common form of phosphorus in soils, as it forms when phosphate in rainwater reacts with dissolved aluminium in the soil. Although it is not as insoluble as many other components of soils in those regions, aluminium phosphate can form exceedingly insoluble double salts known as taranakites with many essential elements for plant growth that are normally highly soluble in water, such as potassium and nitrogen.

In coastal areas of South Africa and Namibia, the combination of exceedingly old soils and a high input of phosphate from very fertile oceans due to the Benguela Current causes aluminium phosphate to accumulate to form a concentrated mineral, known as aluminium phosphate rock. Only in recent years has there been any interest in the mining of these considerable deposits as a source of phosphorus for agriculture, but there could be considerable economic value if low-cost treatment becomes possible.

The mineral form of aluminium phosphate, berlinite, is rarely found in the nature. It possess quartz-like structure, which makes these 2 minerals often hard to distinguish by standard laboratory methods (like Powder X-Ray Diffraction)

References

1. ^ Pradyot Patnaik. Handbook of Inorganic Chemicals. McGraw-Hill, 2002, ISBN 0070494398
2. ^ http://www.spipharma.com/downloads/Products/AntacidActives/Specialty_Products/AlPhosphateMSDS.pdf, Aluminum phosphate MSDS, SPI Pharma
3. ^ http://www.nithyasrichemicals.com/aluminium-based-products.html, Aluminium Based Products at Nithyasri Chemicals]
4. ^ http://www.sciencemadness.org/talk/viewthread.php?tid=12694, Sciencemadness thread "Aluminum phosphate decomposition"
5. ^ Ibid

External links

• MSDS

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