Zinc phosphide

Chembox new
Name = Zinc phosphide
ImageName = Zinc phosphide
OtherNames = trizinc diphosphide
Section1 = Chembox Identifiers
CASNo = 1314-84-7
Section2 = Chembox Properties
Formula = Zn₃P₂
MolarMass = 258.1 g/mol
Appearance = dark gray crystals
Density = 4.6 g/cm³, solid
Solubility = insoluble
MeltingPt = 420°C
BoilingPt = 1100°C
Section3 = Chembox Structure
CrystalStruct = tetragonal
Section7 = Chembox Hazards
EUClass =

Zinc phosphide (Zn₃P₂) is an inorganic chemical compound.

Metal phosphides have been used as rodenticides. A mixture of food and zinc phosphide is left where the rodents can eat it. The acid in the digestive system of the rodent reacts with the phosphide to generate the toxic phosphine gas. This method of vermin control has possible use in places where rodents immune to many of the common poisons have appeared. Other pesticides similar to zinc phosphide are aluminium phosphide and calcium phosphide.

Zinc phosphide is typically added to rodent baits in amount of around 0.75-2%. The baits have strong, pungent garlic-like odor characteristic for phosphine liberated by hydrolysis. The odor attracts rodents, but has a repulsive effect on other animals; birds, notably wild turkeys, are not sensitive to the smell. The baits have to contain sufficient amount of zinc phosphide in sufficiently attractive food in order to kill rodents in a single serving; a sublethal dose may cause aversion towards zinc-phosphide baits encountered by surviving rodents in the future.

Rodenticide-grade zinc phosphide usually comes as a black powder containing 75% of zinc phosphide and 25% of antimony potassium tartrate, an emetic to cause vomiting if the material is accidentally ingested by humans or domestic animals. However, it is still effective against rats, mice, guinea pigs and rabbits, all of which do not have a vomiting reflex. [http://www.ratbehavior.org/vomit.htm]

Conditions/substances to avoid contact of zinc phosphide with are: acids, water, carbon dioxide and strong oxidizing agents.

Reactions

Zinc phosphide can be prepared by the reaction of zinc with phosphorus:

:3 Zn + 2 P → Zn₃P₂

Zinc phosphide will react with water to produce phosphine (PH₃) and zinc hydroxide (Zn(OH)₂):

:Zn₃P₂ + 6 H₂O → 2 PH₃ + 3 Zn(OH)₂

References

External links

* [http://extoxnet.orst.edu/pips/zincphos.htm Zinc Phosphide Pesticide Information Profile - Extension Toxicology Network]
* [http://www.epa.gov/pesticides/factsheets/chemicals/rodenticides_fs.htm EPA Proposed Risk Mitigation Decision for Nine Rodenticides]
* [http://www.michigan.gov/dnr/0,1607,7-153-10370_12150_12220-26326--,00.html Zinc phosphide properties and use in Michigan]
* [http://milmed.pmk.ac.th/md0173%20PESTICIDES%20IN%20THE%20MILITARY.pdf MD0173 - Pesticides in the military]