Phosphoric acid

Phosphoric acid
Names
IUPAC name
Phosphoric acid
Other names
Orthophosphoric acid
Identifiers
3D model (JSmol)
ChEBI
ChEMBL
ChemSpider
ECHA InfoCard 100.028.758
EC Number
  • 231-633-2
E number E338 (antioxidants, ...)
KEGG
RTECS number
  • TB6300000
UNII
UN number 1805
  • 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
  • OP(=O)(O)O
Properties
H3PO4
Molar mass 97.994 g·mol−1
Appearance Colorless solid
Odor Odorless
Density 1.6845 g/cm3 (25 °C, 85%), 1.834 g/cm3 (solid)
Melting point 42.35 °C (108.23 °F; 315.50 K) anhydrous
29.32 °C (84.78 °F; 302.47 K) hemihydrate
Boiling point
  • 212 °C (414 °F)(only water evaporates)
  • 392.2 g/(100 g) (−16.3 °C)
  • 369.4 g/(100 mL) (0.5 °C)
  • 446 g/(100 mL) (15 °C)
  • 548 g/(100 mL) (20 °C)
Solubility Soluble in ethanol
log P −2.15
Vapor pressure 0.03 mmHg (20 °C)
Conjugate base Dihydrogen phosphate
−43.8·10−6 cm3/mol
  • 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
Monoclinic
Tetrahedral
Thermochemistry
145.0 J/(mol⋅K)
150.8 J/(mol⋅K)
−1271.7 kJ/mol
−1123.6 kJ/mol
Hazards
GHS labelling:
Danger
H290, H314
P280, P305+P351+P338, P310
NFPA 704 (fire diamond)
3
0
0
Flash point Non-flammable
Lethal dose or concentration (LD, LC):
1530 mg/kg (rat, oral)
NIOSH (US health exposure limits):
PEL (Permissible)
 TWA 1 mg/m3
REL (Recommended)
 TWA 1 mg/m3 ST 3 mg/m3
IDLH (Immediate danger)
 1000 mg/m3
Safety data sheet (SDS) ICSC 1008
Related compounds
Except where otherwise noted, data are given for materials in their standard state (at 25 °C [77 °F], 100 kPa).
N verify (what is YN ?)
Infobox references
This article is about orthophosphoric acid. For other acids commonly called "phosphoric acid", see Phosphoric acids and phosphates.
Not to be confused with Phosphorous acid.

Phosphoric acid (orthophosphoric acid, monophosphoric acid or phosphoric(V) acid) is a colorless, odorless phosphorus-containing solid, and inorganic compound with the chemical formula H3PO4. It is commonly encountered as an 85% aqueous solution, which is a colourless, odourless, and non-volatile syrupy liquid. It is a major industrial chemical, being a component of many fertilizers.

The compound is an acid. Removal of all three H+ ions gives the phosphate ion PO3−4. Removal of one or two protons gives dihydrogen phosphate ion H2PO−4, and the hydrogen phosphate ion HPO2−4, respectively. Phosphoric acid forms esters, called organophosphates.

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.

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