Phosphoric 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.
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Product Info
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| Names | |||
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| IUPAC name
Phosphoric acid
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| Other names
Orthophosphoric acid, hydrogen phosphate
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| Identifiers | |||
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3D model (JSmol)
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| ChEBI | |||
| ChEMBL | |||
| ChemSpider | |||
| ECHA InfoCard | 100.028.758 | ||
| EC Number |
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| E number | E338 (antioxidants, …) | ||
| KEGG | |||
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PubChem CID
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| RTECS number |
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| UNII | |||
| UN number | 1805 | ||
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CompTox Dashboard (EPA)
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| Properties | |||
| H3PO4 | |||
| Molar mass | 97.994 g·mol−1 | ||
| Appearance | Colorless solid | ||
| Odor | Odorless | ||
| Density | 1.6845 g/cm3 (25 °C, 85%),[1] 1.834 g/cm3 (solid)[2] | ||
| Melting point | 42.35 °C (108.23 °F; 315.50 K) anhydrous[12] 29.32 °C (84.78 °F; 302.47 K) hemihydrate[13] |
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| Boiling point | |||
| Solubility | Soluble in ethanol | ||
| log P | −2.15[7] | ||
| Vapor pressure | 0.03 mmHg (20 °C)[8] | ||
| Conjugate base | Dihydrogen phosphate | ||
| −43.8·10−6 cm3/mol[10] | |||
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Refractive index (nD)
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| Viscosity | 2.4–9.4 cP (85% aq. soln.) 147 cP (100%) |
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| Structure | |||
| Monoclinic | |||
| Tetrahedral | |||
| Thermochemistry[14] | |||
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Heat capacity (C)
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145.0 J/(mol⋅K) | ||
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Std molar
entropy (S⦵298) |
150.8 J/(mol⋅K) | ||
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Std enthalpy of
formation (ΔfH⦵298) |
−1271.7 kJ/mol | ||
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Gibbs free energy (ΔfG⦵)
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−1123.6 kJ/mol | ||
| Hazards | |||
| GHS labelling: | |||
 [15] |
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| Danger | |||
| H290, H314[15] | |||
| P280, P305+P351+P338, P310[15] | |||
| NFPA 704 (fire diamond) | |||
| Flash point | Non-flammable | ||
| Lethal dose or concentration (LD, LC): | |||
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LD50 (median dose)
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1530 mg/kg (rat, oral)[16] | ||
| NIOSH (US health exposure limits): | |||
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PEL (Permissible)
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TWA 1 mg/m3[8] | ||
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REL (Recommended)
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TWA 1 mg/m3 ST 3 mg/m3[8] | ||
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IDLH (Immediate danger)
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1000 mg/m3[8] | ||
| Safety data sheet (SDS) | ICSC 1008 | ||
| Related compounds | |||
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Related phosphorus oxoacids
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