Diphosphorus pentoxide

Diphosphorus pentoxide. According to systematic nomenclature, also known by the stock nomenclature as phosphorus oxide (V), and by the traditional nomenclature as diphosphorous pentaoxide, or phosphoric oxide, it is presented in a simple monomeric form whose stoichiometric formula is (P 2 O 5 ) and its dimers, presented as a molecular formula (P 4 O 10 ), can be considered as the anhydride of phosphoric acid.


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  • 1 Structure
  • 2 Physical properties
  • 3 Obtaining
  • 4 Chemical properties
  • 5 Chemical hazards
  • 6 Risks
  • 7 First aid measures
  • 8 Applications
  • 9 Sources


Its structure is related to that of tetrahedral phosphorus, by inserting an Oxygen atom into each of the four Phosphorous . The Phosphorus – Oxygen bonds are more polar than the corresponding Oxygen and Nitrogen (the partial charges of Phosphorus and Oxygen are + 0.27 and – 0.13 respectively). It presents several polytropic forms (three crystalline and one amorphous), the mixture of these three varieties constitutes the so-called “phosphoric snow”.

Physical properties

The molar mass diphosphorus pentoxide 141.9 g / mol, very soluble in water , forms very hygroscopic white crystals, is very volatile and easy to sublimate at 300 ° C (about 573.15 K. When P 4 O 10 is heated to more than 500 ° C, it does not liquefy, but becomes a solid with a high degree of polymerization.


Phosphorus pentoxide is produced by the combustion of phosphorus with excess dioxygen in a commercial way, resulting in the product being doped with lower oxides and purified by sublimation in the presence of dioxygen

4 (s) + 3O 2 (g) = P 4 O 6 (l)

When the oxide is heated to around 200  ° C in a vacuum it is transformed into phosphorus tetroxide along with red phosphorus.

Chemical properties

The diphosphorus pentoxide solution reacts in water to obtain a strong acid, reacts violently with bases and is corrosive. Diphosphorous pentoxide in the presence of water reacts with metals to form flammable or poisonous gases (hydrogen or phosphine).
4 O 10 is very hygroscopic, it reacts vigorously with water, which leads to the formation of a series of acid hydroxides of phosphorus V:

4 O 10 (l) + 2H 2 O = 4HPO 3 (ac)


4HPO 3 (ac) + 2H 2 O = 2H 4 P 2 O 7 (ac)


2H 4 P 2 O 7 (ac) + 2H 2 O = 4H 3 PO 4 (ac)

Chemical hazards

Never pour water on this substance; When it must be dissolved or diluted, always add it to the water slowly, in addition to not putting the diphosphorus pentoxide in contact with combustible substances. The solution in water is a strong acid, reacts violently with bases and is corrosive.

Reacts violently with perchloric acid, creating a risk of fire and explosion. Reacts violently with water to form phosphoric acid with heat generation. In the presence of water it reacts with metals forming flammable or poisonous gases ( hydrogen or phosphine ).


Diphosphorus pentoxide is a white powder that facilitates the combustion of other substances, it is very corrosive to the eyes, the skin and the respiratory tract. it can be absorbed by inhalation and by ingestion, evaporation at 20 ° C is negligible; however, a harmful concentration of airborne particles can be reached quickly by dispersion.

The effects due to inhalation vary from burning sensations in the nose and throat, causing coughing, gasping, can cause pulmonary edema. Ingestion can cause abdominal pain, diarrhea, nausea, vomiting. Contact with skin or eyes can cause redness, skin burns, or severe deep burns in addition to pain.

The symptoms of pulmonary edema often do not become apparent until a few hours have passed and are aggravated by physical exertion. Do not pour into the sewer. The spilled substance must be collected in acid resistant containers, carefully neutralize the residue with soda lime or calcium carbonate, eliminate the residue with abundant water .

First aid measures

In case of:

Ingestion: It is important not to induce vomiting, rest and undergo medical attention.
Inhalation: Move the person where there is clean air, in addition to rest. If breathing is difficult, artificial respiration and medical attention should be indicated.
Skin contact: Wash off quickly with plenty of water, for at least 15 minutes, use an emergency shower, take off contaminated clothing and then wash or discard it, if injury is maintained, seek medical assistance immediately.
Eye contact :Wash quickly with plenty of water in an eye wash, at least 15 to 10 minutes, separating the eyelids (remove contact lenses if this can be done more easily), then consult a doctor.
Fire in the environment: all extinguishing agents are allowed.


Reacting vigorously with water, it is used as a good drying agent for gases and liquids. Exposed to humidity, it becomes viscous as it incorporates water, and its affinity for it is so great that it is frequently used as a dehydrating agent in chemical reactions, especially in organic synthesis.


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