Phosphoric acid

Absorption

Ortho phosphate is absorbed from, and to a limited extent secreted into, the gastrointestinal tract.

Toxicity

Man: LDLo, route unreported at 220mg/kg Rabbit: LD 50, Route: Skin, Reported dose: 2740 mg /kg, Effects: Behavioral : somnolence ( general depressed activity), Excitement Rat: LC50, Route: inhalation, Reported dose: >850 mg/m3/1h Rat: LD50, Route: oral, Reported dose: 1530 mg/kg, Effects: Kidney, ureter and bladder hematuria, Behavioral: somnolence (general depressed activity)

Description

The most common form of phosphoric acid (H3PO4) is the 85% aqueous form. Pure anhydrous phosphoric acid is a white solid with a melting point of 42 C. Phosphoric acid has three pKa values covering a wide range (pKa's: 2.15, 7.20, 12.32). This is the reason why phosphoric acid solutions make a great choice as a buffer.

Chemical properties

Phosphoric acid is a colorless, odorless, crystalline solid or a thick syrupy liquid. Physical state is strength and temperature dependent.
Concentrated phosphoric acid occurs as a colorless, odorless, syrupy liquid. It has a pleasing acid taste when suitably diluted.
Pure phosphoric acid, also called orthophosphoric acid, is a clear, colorless, mineral acid with moderate strength. It is normally marketed as an aqueous solution of 75–85% in which it exists as a clear, viscous liquid.

Food-grade phosphoric acid is used to acidify foods and beverages. It provides a tangy or sour taste and, being a mass-produced chemical, is available cheaply and in large quantities. Phosphoric acid, used in many soft drinks, has been linked to lower bone density in epidemiological studies. In brief, phosphoric acid is a strong acid and common industrial chemical used in the manufacture of a wide number of products, notably porcelain and metal cleaners, detergents, and fertilisers. It is also used as a food additive and is a major constituent of many soft drinks. Low phosphate concentrations are found in drinking water to which it is added in some areas in order to reduce lead solubility.

Indications

Phosphoric acid is used in dentistry and orthodontics as an etching solution, to clean and roughen the surfaces of teeth where dental appliances or fillings will be placed.

Background

Phosphoric Acid is a colorless, odorless phosphorus-containing inorganic acid. Phosphoric acid is a sequestering agent which binds many divalent cations, including Fe++, Cu++, Ca++, and Mg++.

Pharmacokinetics

Transport of phosphate from the gut lumen is an active, energy-dependent process that is modified by several factors. ... Vitamin D stimulates phosphate absorption, an effect reported to precede its action on calcium ion transport.

The Uses of Phosphoric acid

Phosphoric acid is used in the manufacture of superphosphate fertilisers, livestock feeds, phosphate salts, polyphosphates, soaps, waxes, polishes and detergents. Phosphoric acid is used as a soil stabiliser, in the manufacture of fire control agents, opal glasses, electric lights, in cotton dyeing, tile cleaning, ceramic binding, dental cement, water treatment, electro-polishing, operating lithography, photoengraving operations, process engraving, as a petrol additive and in coagulating rubber latex. It is used in metal rust proofing before painting, in the polishing of metals, in pickling and in hot stripping for aluminium and zinc substrates.
Phosphoric acid is used as an acid catalyst in making ethylene and purifying hydrogen peroxide, in the manufacture of chemicals (ethylbenzene, propylene, cumene), as a bonding agent for refractory bricks, in extracting penicillin and as an analytical agent. It is used as an anti-oxidant in food, as a flavour additive for sharp taste in food (jellies, preserves) and soft drinks (e.g. Coca-Cola), as a tang (Food Additive 338) and for the manufacture of yeasts and gelatine. It is used to manufacture the phosphoric acid electrolyte fuel cell system and it has been used to treat lead poisoning.