Phosphoric acid is an inorganic chemical compound belonging to the group of triprotic oxoacids, in which phosphorus occurs in the +V oxidation state. Accordingly, the acid can be deprotonated in three steps, forming three different anions, which in turn form three different phosphoric acid salts:
1. Dihydrogen phosphates (dihydrogen phosphate anion):
H3PO4(aq) + H2O(l) ⇌ H3O+(aq) + H2PO4-(aq) / Ks1 = 6,9 × 10-3; pKs1 = 2,161.
2. Hydrogen phosphates (hydrogen phosphate anion):
H2PO4-(aq) + H2O(l) ⇌ H3O+(aq) + HPO42-(aq) / Ks2 = 6,2 × 10-8; pKs2 = 7,207.
3. Phosphates (phosphate anion):
HPO42-(aq) + H2O(l) ⇌ H3O+(aq) + PO43-(aq) / Ks3 = 4,7 × 10-13; pKs3 = 12,325.
The esters of phosphoric acid are also called phosphates or organophosphates.
INCI name
PHOSPHORIC ACID
Molecular formula and structural formula of Phosphoric Acid:
H3O4P or H3PO4
Mr = 97.9938 g/mol
SMILES: OP(=O)(O)O
Pure anhydrous phosphoric acid is a white, non-volatile, non-flammable, odorless, highly hygroscopic solid that deliquesces rapidly in air. Commercially available are colorless aqueous phosphoric acid solutions of varying concentrations up to approximately 90%. The more concentrated acid is viscous to syrupy. The data in the following table refer to the solid form unless otherwise stated.
Mass-related elemental composition and isotope proportions of the compound Phosphoric Acid - H3O4P - calculated based on molecular mass.
*) The third column lists the atomic masses or isotope masses of the elements involved and - in square brackets - the natural isotope composition.
The molar mass is M = 97.993761998 grams per mole.
The amount of substance in one kilogram of the substance is n = 10.205 mol.
The amount of substance in one gram of the substance is n = 0.01 mol.
Monoisotopic mass: 97.9768955703 Da - related to 1H316O431P.
E-Nummer: E338
The food industry uses diluted phosphoric acid as a food additive with the E number E338 as a preservative, acidifier, acidity regulator and antioxidant to inhibit the rancidification of fats and the discoloration of meat, sausage or cake fillings.
EU: Status and regulations see EU Food Additives DB Ref. Number 3107.
INCI Name: PHOSPHORIC ACID
Phosphoric acid is an ingredient in cosmetic products, functioning as a buffering component.
Source: CosIng (Cosmetic Ingredient Database) number: 36546.
(General information without guarantee of accuracy and completeness! The information does not replace the chemical safety data sheet or a risk assessment, but rather provides a general overview of the risk posed by the hazardous substance.
Signal word: Danger
GHS hazard statements (H phrases):
LD50 (rat, oral): 1530 mg/kg.
Labeling in the EU: See ECHA Substance Infocard 100.028.758.
For toxicology and occupational safety when handling Phosphoric Acid as well as measures to be taken in case of danger, see: Hazardous Substances Information System GESTIS, ZVG-Nr. 001800.
International Chemical Safety Card ICSC (SDS, MSDS): See ICSC: 1008.
Note: The labeling requirement according to the CLP Regulation (EU) does not apply, among other things, to certain substances and mixtures for end users that are in the form of finished products, such as pharmaceuticals, veterinary drugs, cosmetics, certain medical products and medical devices, food or feed, as well as certain Food additives or flavorings. Special legal regulations may need to be adhered to here.
The table below lists producers and suppliers of Phosphoric Acid as a commercial chemical for laboratories, research, industry and production with the corresponding contact details.
[0] - Specialist and research articles in scientific journals via PubMed: Phosphoric_Acid.
Last update: 2025-12-28
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