Phosphoric acid

Phosphoric acid
Ball-and-stick model	Space-filling model
Names
	IUPAC name Phosphoric acid
	Other names Orthophosphoric acid
Identifiers
CAS Number	7664-38-2 ;
3D model (JSmol)	Interactive image;
ChEBI	CHEBI:26078 ;
ChEMBL	ChEMBL1187 ;
ChemSpider	979 ;
ECHA InfoCard	100.028.758
EC Number	231-633-2;
E number	E338 (antioxidants, ...)
KEGG	D05467 ;
PubChem CID	1004;
RTECS number	TB6300000;
UNII	E4GA8884NN ;
UN number	1805
CompTox Dashboard (EPA)	DTXSID5024263 ;
	InChI InChI=1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4) Key: NBIIXXVUZAFLBC-UHFFFAOYSA-N ; InChI=1/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4) Key: NBIIXXVUZAFLBC-UHFFFAOYAI;
	SMILES OP(=O)(O)O;
Properties
Chemical formula	H; 3PO; 4
Molar mass	97.994 g·mol−1
Appearance	colorless syrup
Odor	Odorless
Density	1.6845 g⋅cm−3 (25 °C, 85%),[1] 1.834 g⋅cm−3 (solid)[2]
Melting point	40–42.4 °C (104.0–108.3 °F; 313.1–315.5 K)[3]
Boiling point	212 °C (414 °F; 485 K)[4]
Solubility in water	392.2 g/100 g (−16.3 °C); 369.4 g/100 mL (0.5 °C); 446 g/100 mL (15 °C)[5]; 548 g/100 mL (20 °C)[3];
Solubility	Soluble in ethanol
log P	−2.15[6]
Vapor pressure	0.03 mmHg (20 °C)[7]
Conjugate base	Dihydrogen phosphate
Magnetic susceptibility (χ)	−43.8·10−6 cm3/mol[8]
Refractive index (nD)	1.3420 (8.8% w/w aq. soln.)[9]; 1.4320 (85% aq. soln) 25 °C;
Viscosity	2.4–9.4 cP (85% aq. soln.) ; 147 cP (100%)
Structure
Crystal structure	Monoclinic
Molecular shape	Tetrahedral
Thermochemistry[10]
Heat capacity (C)	145.0 J/mol⋅K
Std molar; entropy (So298)	150.8 J/mol⋅K
Std enthalpy of; formation (ΔfH⦵298)	−1271.7 kJ/mol
Gibbs free energy (ΔfG˚)	-1123.6 kJ/mol
Hazards
Safety data sheet	ICSC 1008
GHS pictograms	[11]
GHS Signal word	Danger
GHS hazard statements	H290, H314[11]
GHS precautionary statements	P280, P305+351+338, P310[11]
NFPA 704 (fire diamond)	0 3 0
Flash point	Non-flammable
	Lethal dose or concentration (LD, LC):
LD50 (median dose)	1530 mg/kg (rat, oral)[12]
	NIOSH (US health exposure limits):
PEL (Permissible)	TWA 1 mg/m3[7]
REL (Recommended)	TWA 1 mg/m3 ST 3 mg/m3[7]
IDLH (Immediate danger)	1000 mg/m3[7]
Related compounds
Related phosphorus oxoacids	Hypophosphorous acid; Phosphorous acid; Pyrophosphoric acid; Triphosphoric acid; Peroxomonophosphoric acid; Peroxodiphosphoric acid;
	Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
	verify (what is ?)
	Infobox references

Phosphoric acid, also known as orthophosphoric acid or phosphoric(V) acid, is a weak acid with the chemical formula H
₃P O
₄. It is normally encountered as a colorless syrup of 85% concentration in water. The pure compound is a colorless solid.

All three hydrogens are acidic to varying degrees and can be lost from the molecule as H⁺ ions (protons). When all three H⁺ ions are removed, the result is an orthophosphate ion PO₄³⁻, commonly called "phosphate". Removal of one or two protons gives dihydrogen phosphate ion H
₂PO⁻
₄, and the hydrogen phosphate ion HPO²⁻
₄, respectively. Orthophosphoric acid also forms esters, called organophosphates.[13]

Phosphoric acid is commonly encountered in chemical laboratories as an 85% aqueous solution, which is a colourless, odourless, and non-volatile syrupy liquid. Although phosphoric acid does not meet the strict definition of a strong acid, the 85% solution can still severely irritate the skin and damage the eyes.

The name "orthophosphoric acid" can be used to distinguish this specific acid from other "phosphoric acids", such as pyrophosphoric acid. Nevertheless, the term "phosphoric acid" often means this specific compound; and that is the current IUPAC nomenclature.

Manufacture

Phosphoric acid is produced industrially by two general routes.[14] In the wet process a phosphate-containing mineral such as calcium hydroxyapatite is treated with sulfuric acid.[15]

{\ce {Ca5(PO4)3OH + 5H2SO4 -> 3H3PO4 + 5CaSO4v + H2O}}

Fluoroapatite is an alternative feedstock, in which case fluoride is removed as the insoluble compound Na₂SiF₆. The phosphoric acid solution usually contains 23–33% P₂O₅ (32–46% H₃PO₄). It may be concentrated to produce commercial- or merchant-grade phosphoric acid, which contains about 54–62% P₂O₅ (75–85% H₃PO₄). Further removal of water yields superphosphoric acid with a P₂O₅ concentration above 70% (corresponding to nearly 100% H₃PO₄). Calcium sulfate (gypsum) is produced as a by-product and is removed as phosphogypsum.

To produce food-grade phosphoric acid, phosphate ore is first reduced with coke in an electric arc furnace, to make elemental phosphorus. Silica is also added, resulting in the production of calcium silicate slag. Elemental phosphorus is distilled out of the furnace and burned with air to produce high-purity phosphorus pentoxide, which is dissolved in water to make phosphoric acid.

The phosphoric acid from both processes may be further purified by removing compounds of arsenic and other potentially toxic impurities.

Acidic properties

All three hydrogens are acidic, with dissociation constants pK_a1 = 2.14, pK_a2 = 7.20, and pK_a3 = 12.37. It follows that, in water solutions, phosphoric acid is mostly dissociated into some combination of its three anions, except at very low pH. The equilibrium equations are:

H₃PO₄ + H₂O ⇌ H₃O⁺ + H₂PO₄⁻ K_a1= 7.25×10⁻³ [pK_a1 = 2.14]

H₂PO₄⁻+ H₂O ⇌ H₃O⁺ + HPO₄²⁻ K_a2= 6.31×10⁻⁸ [pK_a2 = 7.20]

HPO₄²⁻+ H₂O ⇌ H₃O⁺ + PO₄³⁻ K_a3= 3.98×10⁻¹³ [pK_a3 = 12.37]

Uses

The dominant use of phosphoric acid is for fertilizers, consuming approximately 90% of production.[16]

Application	Demand (2006) in thousands of tons	Main phosphate derivatives
Soaps and detergents	1836	STPP
Food industry	309	STPP (Na₅P₃O₁₀), SHMP, TSP, SAPP, SAlP, MCP, DSP (Na₂HPO₄), H₃PO₄
Water treatment	164	SHMP, STPP, TSPP, MSP (NaH₂PO₄), DSP
Toothpastes	68	DCP (CaHPO₄), IMP, SMFP
Other applications	287	STPP (Na₃P₃O₉), TCP, APP, DAP, zinc phosphate (Zn₃(PO₄)₂), aluminium phosphate (AlPO₄, H₃PO₄)

Food-grade phosphoric acid (additive E338[17]) is used to acidify foods and beverages such as various colas and jams, providing a tangy or sour taste. Soft drinks containing phosphoric acid, which would include Coca-Cola, are sometimes called phosphate sodas or phosphates. Phosphoric acid in soft drinks has the potential to cause dental erosion.[18] Phosphoric acid also has the potential to contribute to the formation of kidney stones, especially in those who have had kidney stones previously.[19]

Specific applications of phosphoric acid include:

In anti-rust treatment by phosphate conversion coating or passivation
As an external standard for phosphorus-31 nuclear magnetic resonance.
In phosphoric acid fuel cells.
In activated carbon production.[20]
In compound semiconductor processing, to etch Indium gallium arsenide selectively with respect to indium phosphide.[21]
In microfabrication to etch silicon nitride selectively with respect to silicon dioxide.[22]
As a pH adjuster in cosmetics and skin-care products.[23]
As a sanitizing agent in the dairy, food, and brewing industries.[24]

Safety

A link has been shown between long-term regular cola intake and osteoporosis in later middle age in women (but not men).[25] This was thought to be due to the presence of phosphoric acid, and the risk for women was found to be greater for sugared and caffeinated colas than diet and decaffeinated variants, with a higher intake of cola correlating with lower bone density.

At moderate concentrations phosphoric acid solutions are irritating to the skin. Contact with concentrated solutions can cause severe skin burns and permanent eye damage.[26]

gollark: Here is the main apiary system.

gollark: Wrong. We checked with the PIERB, it's very ethical.

gollark: There's plenty of space because the bees are eaten by the flowers.

gollark: We checked, it's very ethical.

gollark: No, #5 is me.

References

Christensen, J. H. and Reed, R. B. (1955). "Design and Analysis Data—Density of Aqueous Solutions of Phosphoric Acid Measurements at 25 °C". Ind. Eng. Chem. 47 (6): 1277–1280. doi:10.1021/ie50546a061.CS1 maint: multiple names: authors list (link)
"CAMEO Chemicals Datasheet - Phosphoric Acid".
Haynes, p. 4.80
http://www.chemspider.com/Chemical-Structure.979.html
Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand. Retrieved 2 June 2014.
"phosphoric acid_msds".
NIOSH Pocket Guide to Chemical Hazards. "#0506". National Institute for Occupational Safety and Health (NIOSH).
Haynes, p. 4.134
Edwards, O. W.; Dunn, R. L. and Hatfield, J. D. (1964). "Refractive Index of Phosphoric Acid Solutions at 25 C.". J. Chem. Eng. Data. 9 (4): 508–509. doi:10.1021/je60023a010.CS1 maint: multiple names: authors list (link)
Haynes, p. 5.13
Sigma-Aldrich Co., Phosphoric acid. Retrieved on 9 May 2014.
"Phosphoric acid". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).
Westheimer, F.H. (6 June 1987). "Why nature chose phosphates". Science. 235 (4793): 1173–1178 (see pp. 1175–1176). Bibcode:1987Sci...235.1173W. CiteSeerX 10.1.1.462.3441. doi:10.1126/science.2434996. PMID 2434996.
Becker, Pierre. (1988). Phosphates and phosphoric acid. New York: Marcel Dekker. ISBN 978-0824717124.
Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 520–522. ISBN 978-0-08-037941-8.
Schrödter, Klaus; Bettermann, Gerhard; Staffel, Thomas; Wahl, Friedrich; Klein, Thomas; Hofmann, Thomas (2008). "Phosphoric Acid and Phosphates". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_465.pub3.
"Current EU approved additives and their E Numbers". Foods Standards Agency. 14 March 2012. Retrieved 22 July 2012.
Moynihan, P. J. (23 November 2002). "Dietary advice in dental practice". British Dental Journal. 193 (10): 563–568. doi:10.1038/sj.bdj.4801628. PMID 12481178.
Qaseem, A; Dallas, P; Forciea, MA; Starkey, M; et al. (4 November 2014). "Dietary and pharmacologic management to prevent recurrent nephrolithiasis in adults: A clinical practice guideline from the American College of Physicians". Annals of Internal Medicine. 161 (9): 659–67. doi:10.7326/M13-2908. PMID 25364887.
Toles, C.; Rimmer, S.; Hower, J. C. (1996). "Production of activated carbons from a washington lignite using phosphoric acid activation". Carbon. 34 (11): 1419. doi:10.1016/S0008-6223(96)00093-0.
Wet chemical etching. umd.edu.
Wolf, S.; R. N. Tauber (1986). Silicon processing for the VLSI era: Volume 1 – Process technology. p. 534. ISBN 978-0-9616721-6-4.
"Ingredient dictionary: P". Cosmetic ingredient dictionary. Paula's Choice. Archived from the original on 18 January 2008. Retrieved 16 November 2007.
"STAR SAN" (PDF). Five Star Chemicals. Retrieved 17 August 2015.
Tucker KL, Morita K, Qiao N, Hannan MT, Cupples LA, Kiel DP (1 October 2006). "Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study". American Journal of Clinical Nutrition. 84 (4): 936–942. doi:10.1093/ajcn/84.4.936. PMID 17023723.
"Phosphoric Acid, 85 wt.% SDS". Sigma-Aldrich. 5 May 2016.

Cited sources

Haynes, William M., ed. (2011). CRC Handbook of Chemistry and Physics (92nd ed.). CRC Press. ISBN 978-1439855119.

External links

This article is issued from Wikipedia. The text is licensed under Creative Commons - Attribution - Sharealike. Additional terms may apply for the media files.

[Density_85%-1] Christensen, J. H. and Reed, R. B. (1955). "Design and Analysis Data—Density of Aqueous Solutions of Phosphoric Acid Measurements at 25 °C". Ind. Eng. Chem. 47 (6): 1277–1280. doi:10.1021/ie50546a061.CS1 maint: multiple names: authors list (link)

[Density_solid-2] "CAMEO Chemicals Datasheet - Phosphoric Acid".

[crc-3] Haynes, p. 4.80

[chemspider-4] ttp://www.chemspider.com/Chemical-Structure.979.html

[sioc-5] Seidell, Atherton; Linke, William F. (1952). Solubilities of Inorganic and Organic Compounds. Van Nostrand. Retrieved 2 June 2014.

[chemsrc-6] "phosphoric acid_msds".

[PGCH-7] NIOSH Pocket Guide to Chemical Hazards. "#0506". National Institute for Occupational Safety and Health (NIOSH).

[8] Haynes, p. 4.134

[Refractive_Index-9] Edwards, O. W.; Dunn, R. L. and Hatfield, J. D. (1964). "Refractive Index of Phosphoric Acid Solutions at 25 C.". J. Chem. Eng. Data. 9 (4): 508–509. doi:10.1021/je60023a010.CS1 maint: multiple names: authors list (link)

[10] Haynes, p. 5.13

[sigma-11] Sigma-Aldrich Co., Phosphoric acid. Retrieved on 9 May 2014.

[12] "Phosphoric acid". Immediately Dangerous to Life and Health Concentrations (IDLH). National Institute for Occupational Safety and Health (NIOSH).

[Westheimer-13] Westheimer, F.H. (6 June 1987). "Why nature chose phosphates". Science. 235 (4793): 1173–1178 (see pp. 1175–1176). Bibcode:1987Sci...235.1173W. CiteSeerX 10.1.1.462.3441. doi:10.1126/science.2434996. PMID 2434996.

[14] Becker, Pierre. (1988). Phosphates and phosphoric acid. New York: Marcel Dekker. ISBN 978-0824717124.

[15] Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nd ed.). Butterworth-Heinemann. pp. 520–522. ISBN 978-0-08-037941-8.

[Ullmann-16] Schrödter, Klaus; Bettermann, Gerhard; Staffel, Thomas; Wahl, Friedrich; Klein, Thomas; Hofmann, Thomas (2008). "Phosphoric Acid and Phosphates". Ullmann's Encyclopedia of Industrial Chemistry. Weinheim: Wiley-VCH. doi:10.1002/14356007.a19_465.pub3.

[17] "Current EU approved additives and their E Numbers". Foods Standards Agency. 14 March 2012. Retrieved 22 July 2012.

[18] Moynihan, P. J. (23 November 2002). "Dietary advice in dental practice". British Dental Journal. 193 (10): 563–568. doi:10.1038/sj.bdj.4801628. PMID 12481178.

[Qa2014-19] Qaseem, A; Dallas, P; Forciea, MA; Starkey, M; et al. (4 November 2014). "Dietary and pharmacologic management to prevent recurrent nephrolithiasis in adults: A clinical practice guideline from the American College of Physicians". Annals of Internal Medicine. 161 (9): 659–67. doi:10.7326/M13-2908. PMID 25364887.

[20] Toles, C.; Rimmer, S.; Hower, J. C. (1996). "Production of activated carbons from a washington lignite using phosphoric acid activation". Carbon. 34 (11): 1419. doi:10.1016/S0008-6223(96)00093-0.

[21] Wet chemical etching. umd.edu.

[Wolf-22] Wolf, S.; R. N. Tauber (1986). Silicon processing for the VLSI era: Volume 1 – Process technology. p. 534. ISBN 978-0-9616721-6-4.

[23] "Ingredient dictionary: P". Cosmetic ingredient dictionary. Paula's Choice. Archived from the original on 18 January 2008. Retrieved 16 November 2007.

[24] "STAR SAN" (PDF). Five Star Chemicals. Retrieved 17 August 2015.

[25] Tucker KL, Morita K, Qiao N, Hannan MT, Cupples LA, Kiel DP (1 October 2006). "Colas, but not other carbonated beverages, are associated with low bone mineral density in older women: The Framingham Osteoporosis Study". American Journal of Clinical Nutrition. 84 (4): 936–942. doi:10.1093/ajcn/84.4.936. PMID 17023723.

[:0-26] "Phosphoric Acid, 85 wt.% SDS". Sigma-Aldrich. 5 May 2016.