Orthophosphoric acid

Phosphoric acid

Names
IUPAC name Phosphoric acid; trihydroxidooxidophosphorus
Other names Orthophosphoric acid; Trihydroxylphosphine oxide
Identifiers
CAS Number	7664-38-2 Y 16271-20-8 />16271-20-8 (hemihydrate) N
3D model (Jmol)	Interactive image
ChEBI	CHEBI:26078 Y
ChEMBL	ChEMBL1187 Y
ChemSpider	979 Y
ECHA InfoCard	100.028.758
EC Number	231-633-2
E number	E338 (antioxidants, ...)
KEGG	D05467 Y
PubChem	1004
RTECS number	TB6300000
UNII	E4GA8884NN Y
UN number	1805
InChI InChI=1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4) Y Key: NBIIXXVUZAFLBC-UHFFFAOYSA-N Y 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	H3O4P
Molar mass	97.99 g·mol−1
Appearance	white solid or colourless, viscous liquid (>42 °C) deliquescent
Odor	odorless
Density	1.885 g/mL (liquid) 1.685 g/mL (85% solution) 2.030 g/mL (crystal at 25 °C)
Melting point	42.35 °C (108.23 °F; 315.50 K) (anhydrous) 29.32 °C (84.78 °F; 302.47 K) (hemihydrate)
Boiling point	158 °C (316 °F; 431 K) 213 °C (415 °F; 486 K) decomposes
Solubility in water	392.2 g/100 g (−16.3 °C) 369.4 g/100 mL (0.5 °C) 446 g/100 mL (14.95 °C) miscible (42.3 °C)
Solubility	soluble in ethanol
Vapor pressure	0.03 mmHg (20°C)
Acidity (pKa)	pKa1 = 2.148 pKa2 = 7.198 pKa3 = 12.319
Magnetic susceptibility (χ)	−43.8·10−6 cm3/mol
Refractive index (nD)	1.3420 (8.8% w/w aq. soln) 1.4320 (85% aq. soln) 25 °C
Viscosity	2.4–9.4 cP (85% aq. soln.) 147 cP (100%)
Structure
Crystal structure	monoclinic
Thermochemistry
Std molar entropy (So298)	158 J/mol·K
Std enthalpy of formation (ΔfHo298)	-1288 kJ/mol
Hazards
Safety data sheet	ICSC 1008
GHS pictograms
GHS signal word	Corrosive
GHS hazard statements	H290, H314
GHS precautionary statements	P280, P305+351+338, P310
EU classification (DSD)	C
R-phrases	R34
S-phrases	(S1/2), S26, S45
NFPA 704	0 3 0
Flash point	Non-flammable
Lethal dose or concentration (LD, LC):
LD50 (median dose)	1530 mg/kg (rat, oral)
US health exposure limits (NIOSH):
PEL (Permissible)	TWA 1 mg/m3
REL (Recommended)	TWA 1 mg/m3 ST 3 mg/m3
IDLH (Immediate danger)	1000 mg/m3
Related compounds
Related phosphorus oxoacids	Hypophosphorous acid Phosphorous acid Pyrophosphoric acid Triphosphoric acid Perphosphoric acid Permonophosphoric acid
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N  (what is YN ?)
Infobox references

Phosphoric acid (also known as orthophosphoric acid or phosphoric(V) acid) is a mineral (inorganic) acid having the chemical formula H₃PO₄. Orthophosphoric acid refers to phosphoric acid, which is the IUPAC name for this compound. The prefix ortho is used to distinguish the acid from related phosphoric acids, called polyphosphoric acids. Orthophosphoric acid is a non-toxic acid, which, when pure, is a solid at room temperature and pressure. The conjugate base of phosphoric acid is the dihydrogen phosphate ion, H
2PO−
4, which in turn has a conjugate base of hydrogen phosphate, HPO2−
4, which has a conjugate base of phosphate, PO3−
4. Phosphates are nutritious for all forms of life.

In addition to being a chemical reagent, phosphoric acid has a wide variety of uses, including as a rust inhibitor, food additive, dental and orthop(a)edic etchant, electrolyte, flux, dispersing agent, industrial etchant, fertilizer feedstock, and component of home cleaning products. Phosphoric acids and phosphates are also important in biology.