Substance profile
Phosphoric acid
Phosphoric acid is unstable orthorhombic crystals or clear syrupy liquid and is odorless.
01 · Identification
What Phosphoric acid is
Phosphoric acid is unstable orthorhombic crystals or clear syrupy liquid and is odorless. Its molecular formula is H3O4P and its molecular weight is 97.995 g/mol. It boils at 407 °C, melts at 42.4 °C, is soluble in water.
Under the GHS it carries the signal word Danger. It is classed as corrosives.
Other names for Phosphoric acid
- orthophosphoric acid
- H3PO4
- C 134
- C 134 (Acid)
- C 434
- C 434 (Acid)
- Decon 4512
- Evits
- K-Etchant
- Kefo
- 3M Etching Liquid
- Mikro Klene Df
- Phosphoric Acid (Aqueous)
- Phosphoric Acid, Aqueous
- phosphoric acid ... %, orthophosphoric acid ... %
02 · GHS classification
Hazards and label elements
Harmonised classification under CLP Annex VI. This is the legally binding classification in the EU; other jurisdictions may differ.
| Code | Hazard statement |
|---|---|
| H314 | Causes severe skin burns and eye damage. |
Precautionary statements: P260, P280, P301, P310, P331
This page lists only the codes assigned to Phosphoric acid. The full reference lives on the hazard statements hub, the precautionary statements hub and the GHS pictograms hub.
03 · Physical and chemical properties
Phosphoric acid properties
Every value is shown with the conditions it was measured under and the source it came from. Where sources disagree, all values are listed rather than one being picked — the difference is usually a different form of the substance, not an error.
| Property | Value | Conditions | Source |
|---|---|---|---|
| Boiling point | 407 °C (764.6 °F) | HSDB | |
| 212.78 °C (415 °F) | NIOSH | ||
| 158 °C (316.4 °F) | ICSC | ||
| Melting point | 42.4 °C (108.3 °F) | HSDB | |
| -17.5 °C (0.5 °F) | HSDB | ||
| 25 °C (77 °F) | HSDB | ||
| Density | 1.8693 g/cm³ | HSDB | |
| 1.8741 g/cm³ | at 25 °C | HSDB | |
| 25 g/cm³ | at 25 °C | HSDB | |
| Solubility | Soluble in water, alcohol; soluble in 8 volumes of 3:1 ether:alcohol mixture | HSDB | |
| Soluble in ethanol | HSDB | ||
| 548 g/100 g water at 20 °C | at 20 °C | HSDB | |
| Vapor pressure | 0.03 mmHg | NIOSH | |
| 0.0285 mmHg | at 20 °C | HSDB | |
| Autoignition temperature | Not flammable (USCG, 1999) | CAMEO | |
| Lower explosive limit (LEL) | Noncombustible Solid | NIOSH | |
| Vapor density | 3.4 (air = 1) | ICSC | |
| Corrosivity | Corrosive to ferrous metals and alloys | HSDB |
Values compiled from PubChem Laboratory Chemical Safety Summary. Temperatures converted to Fahrenheit for reference.
04 · Handling and storage
Storing and handling Phosphoric acid
Storage conditions
Store in cool, dry, well-ventilated location. Separate from alkalies and most metals.
Source: Hazardous Substances Data Bank (HSDB)
Incompatible materials
Reacts with metals to liberate flammable hydrogen gas.
Source: Hazardous Substances Data Bank (HSDB)
Reactivity
PHOSPHORIC ACID reacts exothermically with bases. May react with active metals, including such structural metals as aluminum and iron, to release hydrogen, a flammable gas. Can initiate the polymerization of certain classes of organic compounds. Reacts with cyanide compounds to release gaseous hydrogen cyanide. May generate flammable and/or toxic gases in contact with dithiocarbamates, isocyanates, mercaptans, nitrides, nitriles, sulfides, and strong reducing agents. Forms explosive mixture with nitromethane. Reacts violently with sodium tetrahydroborate. In the presence of chlorides can corrode stainless steel to form explosive hydrogen gas. Emits toxic and irritating fumes of oxides of phosphorus when heated to decomposition [Lewis, 3rd ed., 1993, p. 1029].
Source: CAMEO Chemicals
Planning storage for a mix of chemicals? Check Phosphoric acid in the storage compatibility matrix →
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