Potassium phosphate (K3PO4) structure, properties, uses

The Potassium Phosphate is an inorganic compound formed by three potassium K ions⁺ and a phosphate ion PO₄^3-. Its chemical formula is K₃PO₄. It is a colorless or white crystalline solid. It is very soluble in water, forming alkaline solutions, that is, with many OH ions^-, hence basic pH.

The phosphate ion has an important function in cells that has to do with energy storage. Potassium phosphate is widely used in organic chemistry reactions where it can act as a base, that is, taking H protons⁺. It can also function as a catalyst or accelerator of some reactions.

It has been used to reduce the attack of certain insects on wheat plants as it makes them more resistant to these. However, it has been observed that it favors the evolution of methane (CH₄), a greenhouse gas, from rice microcultures.

It has been used as a laxative, to increase the duration of local anesthesia, to stop cavities and to help coat surfaces, among other applications.

Article index

• 1 Structure
• 2 Nomenclature
• 3 Properties
  • 3.1 Physical state
  • 3.2 Molecular weight
  • 3.3 Melting point
  • 3.4 Density
  • 3.5 Solubility
  • 3.6 pH
  • 3.7 Chemical properties
  • 3.8 Other properties
  • 3.9 Role of phosphate in the human body
• 4 Obtaining
• 5 Uses
  • 5.1 As a basis in organic chemistry reactions
  • 5.2 As a catalyst
  • 5.3 In agriculture
  • 5.4 In medical applications
  • 5.5 As a laxative
  • 5.6 In veterinary medicine
  • 5.7 In obtaining DNA
  • 5.8 In various applications
  • 5.9 Negative aspect for use in agriculture
• 6 References

Structure

Potassium phosphate is made up of three potassium K cations⁺ and a phosphate anion PO₄^3-.

The phosphate ion PO₄^3- It is made up of one phosphorus atom (P) and four oxygen atoms (O), where phosphorus has an oxidation state of +5 and oxygens a valence of -2.

Nomenclature

• Potassium Phosphate
• Tripotassium phosphate
• Tribasic potassium phosphate
• Tripotassium orthophosphate

Properties

Physical state

Colorless or white crystalline solid.

Molecular weight

212.27 g / mol

Melting point

1340 ºC

Density

2,564 g / cm³

Solubility

Very soluble in water: 106 g / 100 g of water at 25 ° C. Insoluble in ethanol.

pH

A solution with 1% K₃PO₄ has a pH of 11.5-12.3.

Chemical properties

When dissolved in water, potassium phosphate separates into the three potassium cations K⁺ and the phosphate anion PO₄^3-. The phosphate anion takes a proton from water and the hydrogen phosphate anion HPO is formed₄^two-. The latter in turn takes another proton from the water and becomes the dihydrogen phosphate anion H_twoPO₄^-.

PO₄^3- + H_twoO ⇔ HPO₄^two- + Oh-

HPO₄^two- + H_twoO ⇔ H_twoPO₄^- + Oh^-

As OH ions are formed^- aqueous solution becomes alkaline.

Other properties

In addition to the anhydrous form (without water), it has several hydrated forms; this means that the K molecule₃PO₄ can be accompanied by one or more water molecules within the crystalline structure.

For this reason it can form, for example, the monohydrate K₃PO₄.H_twoOr, the trihydrate K₃PO₄.3H_twoOr, the heptahydrate and nonahydrate.

Role of phosphate in the human body

The phosphate ion PO₄^3- it is the most abundant anion inside cells and plays an important role in energy storage.

The phosphate ion also participates in activities of formation and nutrition of bones and teeth, as it regulates the concentration of calcium in the blood serum and in numerous energy transfer reactions in the cell..

Obtaining

Potassium phosphate can be obtained starting from the reaction between potassium chloride KCl and ammonium phosphate (NH₄)₃PO₄.

Potassium Chloride + Ammonium Phosphate → Potassium Phosphate + Ammonium Chloride

3 KCl + (NH₄)₃PO₄ → K₃PO₄ + 3 NH₄Cl

Applications

As a basis in organic chemistry reactions

Potassium K phosphate₃PO₄ It has been used in various organic chemistry reactions. For example, it serves in the synthesis of acetylenes starting from dibrominated compounds..

In this synthesis, a dehydrobromination (elimination of hydrogen and bromine) occurs, where K₃PO₄ anhydrous solid (without water) acts as a soft base and takes two protons from the molecule, the two bromine atoms are removed and the corresponding acetylene is obtained.

C₆H₅-CHBr-CH_twoBr + 2 K₃PO₄ → C₆H₅-C≡CH + 2 KBr + 2 K_twoHPO₄

As a catalyst

The K₃PO₄ It serves as a catalyst in various organic chemistry reactions. For example, it has been used as a solid to obtain biodiesel from used frying oil..

Biodiesel is a fuel similar to diesel but obtained from fats or natural oils used or not.

Potassium phosphate was more effective as a catalyst or accelerator of this reaction than sodium phosphate Na₃PO₄ and calcium oxide CaO.

In agriculture

The K₃PO₄ has been used to treat wheat plants and make them resistant to certain pests.

Some researchers treated wheat seedlings with potassium phosphate and it turned out that it induces resistance against aphids. Diuraphis noxia, an insect that attacks these plants.

After applying a dilute solution of K₃PO₄ less severity of the symptoms caused by these insects and a decrease in the number of aphids feeding on them was observed on the seedlings.

In medical applications

Potassium phosphate has been used to modify the anesthetic effect of lidocaine, a local anesthetic. A local anesthetic is a drug that when applied to an area of ​​the body causes loss of sensitivity to pain in that area..

It was found that the K₃PO₄ allows to prolong the local anesthesia of lidocaine.

As a laxative

Potassium phosphate increases the fluidity of the intestinal content as it helps to retain water in the intestine, which indirectly induces the contraction of the intestinal muscle.

In veterinary medicine

The K₃PO₄ is used in animals with diabetic ketoacidosis (a complication of diabetes) to treat hypophosphatemia (low amount of phosphate in the blood).

However, when given in excess it can cause hypocalcaemia (low calcium in the blood), hyperphosphatemia (excess phosphate in the blood), involuntary contraction of muscles, mineralization of soft tissues and kidney failure..

In obtaining DNA

Potassium phosphate has been used as a buffer to purify DNA in genetics laboratories.

DNA is a protein found in cells and contains all the genetic information necessary for the development and functioning of living beings.

By isolating DNA, scientists delve into the study of how hereditary traits are transmitted, which is why potassium phosphate is very helpful.

In various applications

Potassium K phosphate₃PO₄ it serves:

• as a dietary supplement,
• for electrolyte replacement,
• as a buffer, that is, as a chemical system that allows controlling the levels of OH ions^- or hydrogen H⁺ in aqueous solution,
• to slow or inhibit tooth decay,
• as a corrosion inhibitor and antifouling agent,
• as a surface treatment agent and a coating agent,
• as antifreeze,
• in cleaning products.

Negative aspect for use in agriculture

Certain researchers found that adding K₃PO₄ a microculture of rice increases the emission of methane (CH₄) to the atmosphere. Methane is a gas that contributes to the greenhouse effect and increases the temperature of our planet.

References

1. U.S. National Library of Medicine. (2019). Potassium phosphate. Recovered from pubchem.ncbi.nlm.nih.gov.
2. Panciera, D.L. (2012). Fluid Therapy in Endocrine and Metabolic Disorders. Phosphorus Supplementation. In Fluid, Electrolyte, and Acid-Base Disorders in Small Animal Practice (Fourth Edition). Recovered from sciencedirect.com.
3. Shenawi-Khalil, S. et al. (2012). Synthesis of acetylenes via dehydrobromination using solid anhydrous potassium phosphate as the base under phase-transfer conditions. Tetrahedron Letters, Volume 53, Issue 18, 2012, Pages 2295-2297. Recovered from sciencedirect.com.
4. Guan, G. et al. (2009). Tri-potassium phosphate as a solid catalyst for biodiesel production from waste cooking oil. Fuel Processing Technology, Volume 90, Issue 4, 2009, Pages 520-524. Recovered from sciencedirect.com.
5. Kulkami, M.A. (2012). Mechanistic approach for expeditious and solvent-free synthesis of α-hydroxy phosphonates using potassium phosphate as catalyst. Comptes Rendus Chimie, Vol 16, Issue 2, 2013, Pages 148-152. Recovered from sciencedirect.com.
6. Venter, E. et al. (2014). Potassium phosphate induces tolerance against the Russian wheat aphid (Diuraphis noxia, Homoptera: Aphididae) in wheat. Crop Protection Vol 61, July 2014, Pages 43-50. Recovered from sciencedirect.com.
7. Bonturi, N. et al. (2013). Sodium citrate and potassium phosphate as alternative adsorption buffers in hydrophobic and aromatic thiophilic chromatographic purification of plasmid DNA from neutralized lysate. Journal of Chromatography B, Volumes 919-920, 2013, Pages 67-74. Recovered from sciencedirect.com.
8. Conrad, R. and Klose, M. (2005). Effect of potassium phosphate fertilization on production and emission of methane and its ¹³C-stable isotope composition in rice microcosm. Soil Biology and Biochemistry, Vol 37, Issue 11, 2005, Pages 2099-2108. Recovered from sciencedirect.com.
9. Lide, D.R. (editor) (2003). CRC Handbook of Chemistry and Physics. 85^th CRC Press.
10. Smokefoot. (2019). Tripotassium phosphate. Recovered from en.wikipedia.org