Zinc phosphide

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Zinc phosphide
Zinc phosphide
Other names trizinc diphosphide
Molecular formula Zn3P2
Molar mass 258.1 g/mol
Appearance dark gray crystals
Crystal structure tetragonal
CAS number [1314-84-7]
Density and phase 4.6 g/cm3, solid
Solubility in water insoluble
Melting point 420°C
Boiling point 1100°C
EU classification
NFPA 704
Except where noted otherwise, data are given for
materials in their standard state (at 25 °C, 100 kPa)
Infobox disclaimer and references

Zinc phosphide (Zn3P2) is an inorganic chemical compound.

Metal phosphides have been used as a means of killing rodents. 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. Rat, mouse, guinea pig and rabbit do not have the vomiting reflex so can not vomit it.[1]

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

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