Phosphoric acid phosphoric acid

phosphoric acid ( English:phosphoric acid) or called orthophosphoric acid (orthophosphoric acid), chemical type H3PO4 , is a common inorganic acid, non-volatile, easy decomposition, almost no oxidation. With acid, is ternary medium acid, its acidity than hydrochloric acid, sulfuric acid, nitric acid is weak, but than acetic acid, boric acid and other strong. It can be obtained by dissolving the phosphorus pentoxide in hot water. The orthophosphoric acid industry uses sulfuric acid to treat apatite. With nitric acid to oxidize phosphorus, you can get a purer phosphoric acid, usually 83%-98% thick solution, if re-concentrated, you can get colorless crystals. Phosphoric acid is easy to be hygroscopic in the air, heating will gradually lose the coke phosphoric acid, further dehydration to obtain the partial phosphoric acid. Phosphoric acid is easy to combine itself into a variety of compounds such as pyrophosphate (pyrophosphoric acid) or triphosphate (triphosphoric acid).

In addition to being used as a chemical reagent, phosphoric acid can also be used mainly in pharmaceuticals, iron stainless conversion agents, food additives, solvents, electrolytes, fertilizers, metallurgy, feed, etc., as well as in the use of medical cosmetology and dentistry.

Phosphoric acid is ternary acids, can be dissociation out of three hydrogen ions, so it can form three different acidity, respectively: phosphoric acid two hydrogen root h2po−
4. Hydrogen phosphate root hpo2−
4 and phosphate root po3−
4.

Directory[Hide]

• 1 Structure
• 2 Chemical Properties
  • 2.1 Aqueous Solution
• 3 Preparation
  • 3.1 Heating Method
  • 3.2 Wet Manufacturing method
• 4  purpose
  Li class= "toclevel-2 tocsection-8" > 4.1  properties Li class= "toclevel-2 tocsection-9" > 4.2  reaction to halides
  • 4.3  Iron Stainless conversion agent
  • 4.4  food additives
  • 4.5  medicinal
  • 4.6  other applications
• 5 Biological Effects
  • 5.1 Beverage Additives
• 6 References
• 7 External Links
• 8 See also

structure [edit ]

With phosphorus as the center, four oxygen surrounds it, including a double-bond oxygen and three hydroxyl groups. Three solvable hydrogen atoms are combined with three oxygen atoms, respectively.

Chemical Properties [edit ]

Pure phosphoric acid anhydrous compounds at room temperature for white crystals, melting point of 42.35°c, dissolved as viscous liquid.

The orthophosphoric acid is extremely polar, so phosphoric acid is easily soluble in water.

The oxidation number of the central phosphorus (p) of orthophosphoric acid was +5, while the oxidation number of the surrounding oxygen atom (O) was 2 and the hydrogen ion was +1.

Phosphoric acid is a non-toxic inorganic substance, which is a ternary weak acid. Ternary acid means can be extracted from the water out of three H + acid, phosphoric acid dissociation process is as follows:KA1,kA2 and KA3 for the chemical type at 25°c of the dissociation constant

H3po4 (s) + H2O (l) h3o+ (aq) + H2po4− (aq) Ka1= 7.25x10−3

H2po4− (aq) + H2O (l) h3o+ (aq) + Hpo42− (aq) Ka2= 6.31x10−8

Hpo42− (aq) + H2O (l) h3o+ (aq) + Po43− (aq) Ka3= 4.80x10−13

Because of the multi-acid properties of phosphoric acids, the ph value of the large amplitude, causing its buffering phenomenon. Because of its non-toxicity and easy to obtain, the laboratory and industry often take non-toxic phosphate and weak acid (such as citric acid) mixture as a buffer solution,

Phosphoric acid is widely found in organisms, especially phosphorylated carbohydrates, such as DNA, RNA, and ATP.

If the orthophosphoric acid is heated, the monomers of several phosphoric acid molecules are dehydrated and aggregated, such as:

Two phosphoric acid connected to remove a water to form pyrophosphate (pyrophosphoric Acid,h4p2o7)

If several phosphate rings are connected and a molecule of water is detached, a partial phosphoric acid (metaphosphoric acid) is formed, and the general formula is: (HPO3) n. The Chinese name is n-biased phosphoric acid (n≥3). ^{[2] The phosphoric acid is a dehydration of the substance, so it is often used as a desiccant. To further the partial phosphoric acid dehydration is very difficult, the need to use a very strong dehydration agent with heating (simple heating ineffective), can be dehydrated phosphoric acid phosphate anhydride (phosphorus pentoxide, phosphorus pentoxide, chemical formula: P2O5, Molecular formula: P4O10), phosphorus anhydride has a very strong dehydration, Can be used as a desiccant for acidic substances.}

In the case of a super-strong acid (superacids, stronger than H2SO4 acid), phosphoric acid will form a theoretically corrosive acidic substances, hydroxyl phosphate ions (tetrahydroxylphosphonium ion). An example of a super strong acid (Fluoroantimonic Acid,hsbf6) with fluorine antimony acid:

H3po4 + hsbf6→[p (OH) 4+][sbf6]−

Water Solutions [edit ]

Calculation method of phosphoric acid concentration ([a] for the ear concentration) [a] = [H3PO4] + [h2po4−] + [hpo42−] + [po43−]

The following table is the ph of phosphoric acid at different concentrations, and the concentration of each conjugate base of phosphoric acid.

[A] (mol/l)	pH	[h3po4]/[a] (%)	[H2po4−]/[a] (%)	[Hpo42−]/[a] (%)	[Po43−]/[a] (%)
1	1.08	91.7	8.29	6.20x10−6	1.60x10−17
10−1	1.62	76.1	23.9	6.20x10−5	5.55x10−16
10−2	2.25	43.1	56.9	6.20x10−4	2.33x10−14
10−3	3.05	10.6	89.3	6.20x10−3	1.48x10−12
10−4	4.01	1.30	98.6	6.19x10−2	1.34x10−10
10−5	5.00	0.133	99.3	0.612	1.30x10−8
10−6	5.97	1.34x10−2	94.5	5.50	1.11x10−6
10−7	6.74	1.80x10−3	74.5	25.5	3.02x10−5
10−10	7.00	8.24x10−4	61.7	38.3	8.18x10−5

preparation [edit ]

Phosphoric acid has three kinds of preparation methods, heating method (thermal process), wet manufacturing method (wet process) and dry kiln method (dry kiln process)

Heating Method [edit ]

The combustion of phosphorus elemental produces phosphorus pentoxide and dissolves in water to produce phosphoric acid. This method can produce purer phosphoric acid, because many impurities have been removed in the process of refining phosphorus, but still need to remove the hidden arsenic. The most modern method of pure phosphorus is to heat calcium phosphate with sand (mainly silica) and coke in an electric furnace. The chemical formula is as follows:

• CA3 (PO4) 2+3SIO2→3CASIO3+P2O5
• P2o5+5c→2p+5co

Wet Manufacturing Methods [edit ] See also: Nitrate phosphate method

The wet manufacturing method is to add sulfuric acid to calcium phosphate, the source of calcium phosphate is usually apatite.

Reaction: (x is halogen)

Ca5 (PO4) 3X + 5 H2SO4 + h2o→3 H3po4 + 5 CaSO4 2H2O + HX

The solubility of calcium sulfate is small, so it can be filtered out.

The phosphoric acid concentration originally produced by this method contains approximately 23% to 33% P2O5, which is then distilled or diluted to the desired concentration. The commodity grade phosphoric acid is about 54%, while the concentration of the super phosphoric acid is about 70%. ^[3][4]

Products in the wet manufacturing process must also be purified to remove the contained fluoride and arsenide.

uses [edit ] Nature [Edit ]

Concentrated phosphoric acid about 75–85%, for clarification, colorless, tasteless, non-volatile viscous liquid. Although phosphoric acid is non-toxic, 85% of the concentrated phosphoric acid is corrosive.

At such a high concentration, the phosphoric acid molecules in the concentrated phosphoric acid converge to gather phosphoric acid,

reactions to halides [edit ]

Phosphoric acid and halide produce hydrogen halide gas, which can be prepared by this method in the laboratory.

NaCl (s)	+ H3PO4 (L) →nah2po4 (s)	+ HCl (g)
NABR (s)	+ H3PO4 (L) →nah2po4 (s)	+ HBr (g)
NaI (s)	+ H3PO4 (L) →nah2po4 (s)	+ HI (g)

Iron Stainless Conversion Agents [edit ]

Phosphoric acid can be used as the composition of iron stainless conversion agent, phosphoric acid can be red-brown Fe2O3 to Black FePO4, to be stripped to reveal a new metal surface, but also can not be stripped, let him as a metal surface of the protective layer, to prevent further oxidation.

Iron Stainless Conversion Agents are sometimes configured as liquids for metal immersion. Sometimes configured as gelatinous, nicknamed "Navy Jam (Naval jelly)", it can be applied on a vertical or steep incline.

Food Additives [edit ]

Food grade phosphoric acid can be used to acidification drinks or food, such as cola, but the use of health concerns are still. ^[5]

Adding phosphoric acid can make food stimulating and sour, and it can be manufactured cheaply and massively in the industrial process. Phosphoric acid has a greater commercial interest than other organic compounds with the same effect. Citric acid, for example, is usually made from metabolites of black kojimachi bacteria ( aspergillus niger ), which is much more expensive than the production of phosphoric acid. ^[6]

medicinal [edit ]

Phosphoric acid is also used in dentistry and beauty. In dentistry, phosphoric acid can be used to clean teeth and whiten teeth.

Phosphoric acid is also added to the anti-corona drug.

other Applications [edit ]

In addition to the above applications, phosphoric acid also has the following uses:

• Phosphoric acid containing phosphorus-31 can be used as an external marker for NMR
• High Performance liquid Chromatography
• Delivered genre method (Wentworth process): As an oxidizing agent of activated carbon. ^[7]
• Electrolytes in fuel cells of phosphoric acid.
• As a catalyst for olefin and water addition to the manufacture of alcohols.
• As an electrolytic solution for copper plating polishing.
• As Flux
• In the semiconductor process, phosphoric acid can be used as an etching solvent, for example: a mixture of phosphoric acid and hydrogen peroxide can convert InGaAs to INP for etching purposes ^[8].
• Etching silicon nitride, phosphoric acid can convert Si3N4 into SiO2. ^[9]
• As a buffer solution.
• As a dispersing medium for leather handling and detergents.
• As a conditioner for the ph value of the maintenance product ^[10].
• Phosphoric acid is used in the construction industry to remove mineral deposits, cement pictures and water stains.
• Household cleaning agent.
• It can also be used as a direct source of plant phosphorus nutrients by using water-tillage as a regulator for ph value.

Biological Effects [edit ] Beverage Additives [Edit ]

Phosphoric acid is used in food additives, and there is always doubt about osteoporosis. In the past, the frequency of drinking cola and other carbonated beverages was selected by questionnaires, and it was found that subjects who drank carbonated drinks were more prone to osteoporosis. Studies have pointed out that people who drink carbonated beverages do not consume more phosphorus than others, but the body's calcium-phosphorus ratio is significantly lower. A study in the American Journal of Clinical Nutrition (American Journal of Clinical Nutrition) ^{[11] Using double-energy X-rays from 1996 to 2001 to detect bone mineral density in 1672 women and 1148 men found that phosphoric acid did reduce bone density, and the study provided more evidence than previously used questionnaires.}

Another clinical study suggests that phosphorus uptake lowers bone density. However, the total phosphorus intake was not clearly demonstrated to be the main cause of the decrease in bone density is phosphoric acid. ^[]

However, the use of calcium balance in Heaney and Rafferty for 20-40-year-old women who used to drink more than three cups (680 ML) carbonated drinks in the clinical study, but found that phosphate-containing carbonated drinks are not related to calcium loss. ^{[13] The study compared water, milk and a variety of non-alcoholic beverages (two caffeine-free, two non-caffeinated, two phosphoric acid, two containing citric acid). They found that, compared to water, only milk and two other caffeine-containing drinks increased the amount of calcium in the urine, while the addition of a caffeine drink with phosphoric acid and a caffeine-containing drink had a similar rate of calcium loss, and did not increase the effect of caffeine on calcium loss. [14] The study showed that the calcium loss caused by caffeine would be gradually added back, while phosphoric acid did not affect calcium loss in the experiment. Heaney and Rafferty that the cause of osteoporosis in the experimental subjects was that the participants drank carbonated drinks, resulting in less milk intake, resulting in insufficient calcium intake.}

Caffeine is thought to be one of the culprits for osteoporosis. [From ^{][source request].}

Phosphoric acid phosphoric acid