International Numbering System (INS) for Food Additives 338
Food additives Europe numbers: E338
Functional Category
Acidifying agent.
Applications in Pharmaceutical Formulation
Phosphoric acid is widely used as an acidifying agent in a variety of pharmaceutical formulations. It is used in pharmaceutical products as part of a buffer system when combined with a phosphate salt such as sodium phosphate, monobasic or dibasic. It is also widely used in food preparations as an acidulant, flavor, and synergistic antioxidant (0.001–0.005%) and sequestrant. Therapeutically, dilute phosphoric acid has been used welldiluted in preparations used in the treatment of nausea and vomiting. Phosphoric acid 35% gel has also been used to etch tooth enamel and to enhance delivery of drugs through the nail.(3) Nanosized hydroxyapatite powder was made by combining phosphoric acid with egg shells.(4)
Description
Concentrated phosphoric acid occurs as a colorless, odorless, syrupy liquid.
Stability and Storage Conditions
When stored at a low temperature, phosphoric acid may solidify, forming a mass of colorless crystals, comprising the hemihydrate, which melts at 288C. Phosphoric acid should be stored in an airtight container in a cool, dry place. Stainless steel containers may be used.
Incompatibilities
Phosphoric acid is a strong acid and reacts with alkaline substances. Mixtures with nitromethane are explosive.
Safety
In the concentrated form, phosphoric acid is an extremely corrosive and harmful acid. However, when used in pharmaceuticalformulations it is usually very diluted and is generally regarded as an essentially nontoxic and nonirritant material. The lowest lethal oral dose of concentrated phosphoric acid in humans is reported to be 1286 mL/kg.(1) LD50 (rabbit, skin): 2.74 g/kg(1) LD50 (rat, oral): 1.53 g/kg