Aluminium phosphide

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Not to be confused with Aluminium phosphate.
Aluminium phosphide
Aluminium phosphide
Identifiers
CAS number 20859-73-8 YesY
PubChem 30332
ChemSpider 28171 YesY
UNII E23DR6L59S YesY
EC number 244-088-0
RTECS number BD1400000
Jmol-3D images Image 1
Properties
Molecular formula AlP
Molar mass 57.9552 g/mol
Appearance Yellow or gray crystals
Odor garlic-like
Density 2.85 g/cm3
Melting point 2,530 °C (4,590 °F; 2,800 K)
Solubility in water reacts
Band gap 2.5 eV (indirect)[1]
Refractive index (nD) 2.75 (IR), ~3 (Vis) [1]
Structure
Crystal structure Zincblende
Space group T2d-F43m
Lattice constant a = 546.35 pm
Coordination
geometry
Tetrahedral
Thermochemistry
Std molar
entropy
So298
47.3 J/mol K
Std enthalpy of
formation
ΔfHo298
-164.4 kJ/mol
Hazards
MSDS External MSDS
EU classification Toxic T
Dangerous for the Environment (Nature) N
NFPA 704
Flammability code 4: Will rapidly or completely vaporize at normal atmospheric pressure and temperature, or is readily dispersed in air and will burn readily. Flash point below 23 °C (73 °F). E.g., propane Health code 4: Very short exposure could cause death or major residual injury. E.g., VX gas Reactivity code 2: Undergoes violent chemical change at elevated temperatures and pressures, reacts violently with water, or may form explosive mixtures with water. E.g., phosphorus Special hazard W: Reacts with water in an unusual or dangerous manner. E.g., cesium, sodiumNFPA 704 four-colored diamond
Flash point >800 °C
LD50 11.5 mg/kg
Except where noted otherwise, data are given for materials in their standard state (at 25 °C (77 °F), 100 kPa)
 YesY (verify) (what is: YesY/N?)
Infobox references

Aluminium phosphide (aluminum phosphide) is a highly toxic inorganic compound with the chemical formula AlP used as a wide band gap semiconductor and a fumigant. This colorless solid is generally sold as a grey-green-yellow powder due to the presence of impurities arising from hydrolysis and oxidation.

Properties[edit]

AlP crystals are dark grey to dark yellow in color and have a zincblende crystal structure[2] with a lattice constant of 5.4510 Å at 300 K.[3] They are thermodynamically stable up to 1,000 °C (1,830 °F).[4]

Aluminium phosphide reacts with water or acids to release phosphine:[5]

AlP + 3 H2O → Al(OH)3 + PH3
AlP + 3 H+ → Al3+ + PH3

Preparation[edit]

AlP is synthesized by combination of the elements:[4][6]

4Al + P4 → 4AlP

Caution must be taken to avoid exposing the AlP to any sources of moisture, as this generates toxic phosphine gas.

Uses[edit]

Pesticide[edit]

AlP is used as a rodenticide, insecticide, and fumigant for stored cereal grains. It is used to kill small verminous mammals such as moles and rodents. The tablets or pellets, known as "wheat pills", typically also contain other chemicals that evolve ammonia which helps to reduce the potential for spontaneous ignition or explosion of the phosphine gas.

AlP is used as both a fumigant and an oral pesticide. As a rodenticide, aluminium phosphide pellets are provided as a mixture with food for consumption by the rodents. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas. Other pesticides similar to aluminium phosphide are zinc phosphide and calcium phosphide. In this application, aluminium phosphide can be encountered under various brand names, e.g. Celphos, Fumitoxin, Phostoxin, Talunex and Quick Phos. It generates phosphine gas according to the following hydrolysis equation.[6]

2 AlP + 6 H2O → Al2O3∙3 H2O + 2 PH3

It is used as a fumigant when other pesticide applications are impractical and when structures and installations are being treated, such as in ships, aircraft, and grain silos. All of these structures can be effectively sealed or enclosed in a gastight membrane, thereby containing and concentrating the phosphine fumes. Fumigants are also applied directly to rodent burrows.[7]

Semiconductor applications[edit]

Industrially, AlP is a semiconductor material that is usually alloyed with other binary materials for applications in devices such as light-emitting diodes (e.g. aluminium gallium indium phosphide).[8]

Toxicology[edit]

Evidently poisonous, aluminium phosphide has been used for suicide.[9] Fumigation has also caused unintentional deaths, such as examples in Saudi Arabia[10] and the United States.[11] Known as "rice tablet" in Iran, for its use to preserve rice, there have been frequent incidents of accidental or intentional death. There is a campaign by the Iranian Forensic Medicine Organization to stop its use as a pesticide.[12][13]

Recycling of plastic bottle caps containing aluminium phosphide caused the death of three family members in Alcalá de Guadaira, Spain. They had been keeping them in plastic sacks in their bathroom. The deaths occurred accidentally due to aluminum phosphide reacting with water or moisture, and becoming phosphine, leading to their death within hours.[14]

Aluminium phosphide poisoning is considered a wide-scale problem in the Indian subcontinent.[15][16]

References[edit]

  1. ^ a b Berger, L. I. (1996). Semiconductor Materials. CRC Press. p. 125. ISBN 0-8493-8912-7. 
  2. ^ Van Zeghbroeck, B. J. (1997). "Bravais Lattices; Zincblende Lattice". University of Colorado. 
  3. ^ "Lattice Constants". SiliconFarEast.com. 2004. Retrieved 10/02/2011. 
  4. ^ a b White, W. E.; Bushey, A. H.; Holtzclaw, H. F.; Hengeveld, F. W. (1953). "Aluminum Phosphide". In Bailar, J. C. Inorganic Syntheses 4: 23–25. doi:10.1002/9780470132357.ch7. 
  5. ^ Holleman, A. F.; Wiberg, E. (2001), Inorganic Chemistry, San Diego: Academic Press, ISBN 0-12-352651-5 
  6. ^ a b White, W. E.; Bushey, A. H. (1944). "Aluminum Phosphide – Preparation and Composition". Journal of the American Chemical Society 66 (10): 1666. doi:10.1021/ja01238a018. 
  7. ^ Buckle, A. (2005), "Rodenticides", Ullmann's Encyclopedia of Industrial Chemistry, Weinheim: Wiley-VCH, doi:10.1002/14356007.a23_211 
  8. ^ Corbridge, D. E. C. (1995). Phosphorus: An Outline of its Chemistry, Biochemistry, and Technology (5th ed.). Amsterdam: Elsevier. ISBN 0-444-89307-5. 
  9. ^ "Millionaire's death sparks poison scare". BBC News. 2002-10-10. Retrieved 2009-04-05. 
  10. ^ "Fumes kill two Danes in Jeddah". BBC News. 2009-02-24. Archived from the original on 25 February 2009. Retrieved 2009-02-25. 
  11. ^ "Family loses 2nd child in suspected pesticide poisoning". KSL-TV. 2010-02-09. Archived from the original on 11 February 2010. Retrieved 2010-02-09. 
  12. ^ Shadnia, S.; Sasanian, G.; Allami, P.; Hosseini, A.; Ranjbar, A.; Amini-Shirazi, N.; Abdollahi, M. (2009). "A Retrospective 7-Years Study of Aluminum Phosphide Poisoning in Tehran: Opportunities for Prevention". Human & Experimental Toxicology 28 (4): 209–213. doi:10.1177/0960327108097194. PMID 19734272.  edit
  13. ^ Mehrpour, O.; Singh, S. (2010). "Rice Tablet Poisoning: A Major Concern in Iranian Population". Human & Experimental Toxicology 29 (8): 701–702. doi:10.1177/0960327109359643. PMID 20097728. 
  14. ^ "La familia de Alcalá de Guadaira murió tras inhalar plaguicida". La Vanguardia. Agencia EFE. 3 February 2014. Retrieved 3 February 2014. 
  15. ^ Siwach, SB; Gupta, A (1995). "The profile of acute poisonings in Harayana-Rohtak Study". The Journal of the Association of Physicians of India 43 (11): 756–9. PMID 8773034. 
  16. ^ Singh, D; Jit, I; Tyagi, S (1999). "Changing trends in acute poisoning in Chandigarh zone: A 25-year autopsy experience from a tertiary care hospital in northern India". The American journal of forensic medicine and pathology 20 (2): 203–10. doi:10.1097/00000433-199906000-00019. PMID 10414665.