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Phosphoric acid was prepared first by Robert Boyle in 1694 by dissolving phosphorus pentoxide in water.
Phosphoric acid is probably the most important compound of phosphorus.
Phosphoric acid is the second largest inorganic chemical by volume, after sulfuric acid, marketed in the United States.
CAS: 7664-38-2
MF: H3O4P
MW: 98
EINECS: 231-633-2
Synonyms
phosphoricacidsolutions;Phosphorsaeureloesungen;Sonac;wc-reiniger;White phosphoric acid;whitephosphoricacid;phosphoric acid for technical;Phosphoric acid, 85 WT% solution in water, for analysis
The single most important application of Phosphoric acid is manufacturing phosphate salts for fertilizers.
Such fertilizer phosphates include sodium, calcium, ammonium, and potassium phosphates.
Other applications are in metal pickling and surface treatment for removal of metal oxides from metal surfaces; electropolishing of aluminum; as a bonding agent in various refractory products such as alumina and magnesia; as a catalyst in making nylon and gasoline; as a dehydrating agent; in fireproofing wood and fabrics; in lithographic engraving; in textile dyeing; in dental cement; in coagulating rubber latex; in purifying hydrogen peroxide; and as a laboratory reagent.
Dilute solutions of phosphoric acid are used as additives to carbonated beverages for a pleasing sour taste.
Also, dilute acid is used in refining sugar; as a nutrient; and as a buffering agent in preparing jam, jelly, and antibiotics.
The commercial phosphoric acid is 85% (w/w) in strength.
Phosphoric acid is a phosphorus oxoacid that consists of one oxo and three hydroxy groups joined covalently to a central phosphorus atom.
Phosphoric acid has a role as a solvent, a human metabolite, an algal metabolite and a fertilizer.
Phosphoric acid is a conjugate acid of a dihydrogenphosphate and a phosphate ion.
A clear colorless liquid or transparent crystalline solid.
The pure solid melts at 42.35°C and has a density of 1.834 g / cm3.
Liquid is usually an 85% aqueous solution.
Shipped as both a solid and liquid.
Corrosive to metals and tissue.
Used in making fertilizers and detergents and in food processing.
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.
Phosphoric acid is commonly encountered as an 85% aqueous solution, which is a colourless, odourless, and non-volatile syrupy liquid.
Phosphoric acid is a major industrial chemical, being a component of many fertilizers.
Phosphoric acid is an acid.
Removal of all three H+ ions gives the phosphate ion PO3−4.
Removal of one or two protons gives dihydrogen phosphate ion H2PO−4, and the hydrogen phosphate ion HPO2−4, respectively. Phosphoric acid forms esters, called organophosphates.
The name "orthophosphoric acid" can be used to distinguish this specific acid from other "phosphoric acids", such as pyrophosphoric acid.
Nevertheless, the term "phosphoric acid" often means this specific compound; and that is the current IUPAC nomenclature.
History
Phosphoric acid was produced but not identified by alchemists in ancient times.
Phosphoric acid derives its name from the element phosphorus, which was discovered in 1669 by Henning Brand (1630 1710).
Scheele subsequently isolated phosphorus from bone ash and produced phosphoric acid by reacting phosphorus and nitric acid.
Scheele's method replaced bone as the main source of phosphorus rather than urine.
John Bennett Lawes (1814 1900) patented a process in 1841 of making superphosphate from bones and later extended his process to phosphates obtained from rock.
Superphosphates are made by treating Ca3(PO4)2 with sulfuric acid to make more soluble calcium hydrogen phosphates: Ca3(PO4)2 + 2H2SO4 Ca(H2PO4)2 + 2CaSO4.
In this reaction Ca(H2PO4)2 is monobasic calcium phosphate, which is also called superphosphate.
Calcium hydrogen phosphates (superphosphates) are more water soluble and therefore more readily available to plants.
Phosphoric acid Chemical Properties
Melting point: ~40 °C(lit.)
Boiling point: 158 °C(lit.)
density: 1.685 g/mL at 25 °C(lit.)
vapor density: 3.4 (vs air)
vapor pressure: 2.2 mm Hg ( 20 °C)
refractive index: n20/D 1.433
FEMA: 2900 | PHOSPHORIC ACID
storage temp.: no restrictions.
solubility: H2O: soluble
pka: 2.1-7.2-12.3(at 25℃)
form: Solid or Viscous Liquid
color: ≤10(APHA)
Specific Gravity: 1.7
Odor: Odorless
PH Range: 1.5
PH: 3.06(1 mM solution);2.26(10 mM solution);1.63(100 mM solution);
biological source: synthetic
Water Solubility: MISCIBLE
λmax λ: 260 nm Amax: ≤0.05
λ: 280 nm Amax: ≤0.04
Merck: 14,7344
BRN: 1921286
Dielectric constant: 61.0
Exposure limits TLV-TWA 1 mg/m3 (ACGIH, MSHA, and OSHA); TLV-STEL 3 mg/m3 (ACGIH).
Major Application: battery manufacturing
Cosmetics Ingredients Functions: BUFFERING
InChI: 1S/H3O4P/c1-5(2,3)4/h(H3,1,2,3,4)
InChIKey: NBIIXXVUZAFLBC-UHFFFAOYSA-N
LogP: -2.15
CAS DataBase Reference: 7664-38-2(CAS DataBase Reference)
NIST Chemistry Reference: Phosphoric acid(7664-38-2)
EPA Substance Registry System: Phosphoric acid (7664-38-2)
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.
Phosphoric acid has a pleasing acid taste when suitably diluted.
Pure phosphoric acid, also called orthophosphoric acid, is a clear, colorless, mineral acid with moderate strength.
Phosphoric acid 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.
Phosphoric acid 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.
Phosphoric acid 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.
Physical properties
Chemists refer to orthophosphoric acid as phosphoric acid, which is the IUPAC name for this compound.
The prefix “ortho” is used to distinguish the acid from other phosphoric acids, which are generally called polyphosphoric acids.
Orthophosphoric acid is a nontoxic, rather weak triprotic acid.
When pure, Phosphoric acid is a solid at STP.
Orthophosphoric acid is a very polar molecule which makes it highly soluble in water.
The valence state of phosphorous in orthophosphoric acid and other phosphoric acids is ＋5.
Triprotic means that the orthophosphoric acid molecule can dissociate up to three times, producing a hydrogen cation, H+, each time.
Uses
Phosphoric acid is second only to sulfuric acid as an industrial acid and consistently ranksin the top 10 chemicals used globally.
States, but it is used in a number of other applications.
Phosphateswere used as builders and water softeners.
A builder is a substance added to soaps or detergentsto increase their cleansing power.
Phosphoric acid is used as an intermediate in the production of animal feed supplements,water treatment chemicals, metal surface treatments, etching agent, and personal care productssuch as toothpaste.
Phosphoric acid is used as a catalyst in the petroleum and polymer industry.
Phosphoricacid is used in food as a preservative, an acidulant, and flavor enhancer; it acidifies carbonateddrinks such as Coca Cola and Pepsi, giving them a tangy flavor.
Phosphoric acid is used as arust remover and metal cleaner.
Naval Jelly is approximately 25% phosphoric acid.
Other uses for phosphoric acid include opacity control in glass production, textile dyeing, rubber latexcoagulation, and dental cements.
Phosphoric acid (H3PO4) is the most important oxoacid of phosphorus and its main use is in the manufacture of fertilisers.
Within the human body, phosphate is the main phosphorus-containing compound.
Phosphoric acid is an inorganic compound and is the salt of phosphoric acid.
Phosphoric acid can form organic esters with a variety of compounds and these are important in many biochemical processes.
Phosphoric acid has the empirical formula PO43-.
Phosphoric acid is a tetrahedral molecule, where the central phosphorus atom is surrounded by four oxygen atoms.
In biological systems, Phosphoric acid is often found either as the free ion (inorganic phosphate) or as an ester after reaction with organic compounds (often referred to as organic phosphates).
Inorganic phosphate (mostly denoted as Pi) is a mixture of HPO42- and H2PO4- at physiological pH.
Phosphoric Acid is an acidulant that is an inorganic acid produced by burning phosphorus in an excess of air, producing phosphorus pentoxide which is dissolved in water to form Phosphoric acid of varying concentrations.
Phosphoric acid is a strong acid which is soluble in water.
the acid salts are termed phosphates.
Phosphoric acid is used as a flavoring acid in cola and root beer beverages to provide desirable acidity and sourness.
Phosphoric acid is used as a synergistic antioxidant in vegetable shorten- ings.
In yeast manufacture, Phosphoric acid is used to maintain the acidic ph and provide a source for phosphorus.
Phosphoric acid also functions as an acidulant in cheese.
Phosphoric acid is also termed orthophosphoric acid.
In the manufacture of superphosphates for fertilizers, other phosphate salts, polyphosphates, detergents.
Acid catalyst in making ethylene, purifying hydrogen peroxide.
As acidulant and flavor, synergistic antioxidant and sequestrant in food.
Pharmaceutic aid (solvent).
In dental cements; process engraving; rustproofing of metals before painting; coagulating rubber latex; as analytical reagent.
Phosphoric acid is used to acidify foods and beverages such as various colas and jams, providing a tangy or sour taste.
The phosphoric acid also serves as a preservative.
Soft drinks containing phosphoric acid, which would include Coca-Cola, are sometimes called phosphate sodas or phosphates.
Phosphoric acid in soft drinks has the potential to cause dental erosion.
Phosphoric acid also has the potential to contribute to the formation of kidney stones, especially in those who have had kidney stones previously.
Specific applications of Phosphoric acid include:
in anti-rust (iron and steel oxidation) treatment by phosphate conversion coating or passivation, including the Parkerization process
as an external standard for phosphorus-31 nuclear magnetic resonance
in phosphoric acid fuel cells
in activated carbon production
in compound semiconductor processing, to etch Indium gallium arsenide selectively with respect to indium phosphide[38]
in microfabrication to etch silicon nitride selectively with respect to silicon dioxide
in microfabrication to etch aluminium
as a pH adjuster in cosmetics and skin-care products
as a sanitizing agent in the dairy, food, and brewing industries
in chemical polishing (etching) of metals like aluminium
Pharmaceutical Applications
Phosphoric acid is widely used as an acidifying agent in a variety of pharmaceutical formulations.
Phosphoric acid is used in pharmaceutical products as part of a buffer system when combined with a phosphate salt such as sodium phosphate, monobasic or dibasic.
Phosphoric acid 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.
Nanosized hydroxyapatite powder was made by combining phosphoric acid with egg shells.
Industrial uses
As a cleanser for metals, phosphoric acid produces a light etch on steel, aluminum, or zinc, which aids paint adhesion.
Phosphoric acid is a phosphoric acid cleanser for metals.
Nielite D is phosphoric acid with a rust inhibitor, used as a nonfuming pickling acid for steel.
Albrite is available in 75, 80, and 85% concentrations in food and electronic grades, both high-purity specifications.
DAB and Phosbrite are called Bright Dip grades, for cleaning applications.
Phosphoric anhydride, or phosphorus pentoxide, P2O5, is a white, water-soluble powder used as a dehydrating agent and also as an opalizer for glass.
Phosphoric acid is also used as a catalyst in asphalt coatings to prevent softening at elevated temperatures and brittleness at low temperatures.
Production Methods
The majority of phosphoric acid is made by digesting phosphate rock (essentially tricalcium phosphate) with sulfuric acid; the phosphoric acid is then separated by slurry filtration. Purification is achieved via chemical precipitation, solvent extraction, crystallization, or ion exchange.
Preparation
Low-purity technical grade phosphoric acid for use in fertilizers is produced from phosphate rocks by digestion with concentrated sulfuric acid.
The apatite types, primarily consisting of calcium phosphate phosphate rocks, are used: Ca3(PO4)2 + 3H2SO4 + 6H2O → 2H3PO4 + 3(CaSO4•2H2O)
The insoluble calcium sulfate slurry is filtered out.
Acid from this wet process is impure but can be purified by various methods.
Purification steps involve precipitation, solvent extraction, crystallization, and ion exchange techniques.
Phosphoric acid also can be made by many different methods.
Dissolution of phosphorus pentoxide in water and boiling yields phosphoric acid. Pure phosphoric acid can be obtained by burning phosphorus in a mixture of air and steam:
P4 (l) + 5O2 (g) →P4O10 (s)
P4O10 (s) + H2O (g) → 4H3PO4 (l)
The acid also may be prepared by heating violet phosphorus with 33% nitric acid:
4P + 10HNO3 + H2O → 4H3PO4 + 5NO ↑ + 5NO2 ↑
or by heating red phosphorus with nitric acid (1:1). The overall equation is:
P + 3HNO3 → H3PO4 + NO + 2NO2
Production Methods
The major sources of H3PO4 traditionally have been mineral deposits of phosphate rock.
Mining operations are extensive in a number of locations, including the United States (Florida), the Mediterranean area, and Russia, among others.
The major constituent of most phosphate rocks is fluorapatite, 3Ca3(PO4)2·CaF2.
The supply of high-grade phosphates, the raw material of choice for producing high-purity phosphoric acid by the wet process, is rapidly decreasing in some areas.
Two major methods are utilized for the production of phosphoric acid from phosphate rock.
The wet process involves the reaction of phosphate rock with sulfuric acid to produce phosphoric acid and insoluble calcium sulfates.
Many of the impurities present in the phosphate rock are also solubilized and retained in the acid so produced.
While they are of no serious disadvantage when the acid is to be used for fertilizer manufacture, their presence makes the product unsuitable for the preparation of phosphatic chemicals.
In the other method, the furnace process, phosphate rock is combined with coke and silica and reduced at high temperature in an electric furnace, followed by condensation of elemental phosphorus.
Phosphoric acid is produced by burning the elemental phosphorus with air and absorbing the P2O5 in water.
The acid produced by this method is of high purity and suitable for nearly all uses with little or no further treatment.
Synthesis
The elemental phosphorus is burned to produce phosphorous pentoxide (P2O5), which is then hydrated.
The heat is then removed and the phosphoric acid (H3PO4) is collected as a fine mist.
Another important source of phosphoric acid is from phosphate rocks by treatment with sulfuric acid; this is the so-called wet-acid process.
The synthesis of pure phosphoric acid involves several steps including a time-consuming, expensive step, the sublimation of white phosphorus.
