Magnesium phosphide

Description

Magnesium phosphide has the formula of Mg3P2 and themolecularweight of 134.9456 g/mol.It is a yellow cubic crystal having a density of 2.06 g/cm. It reacts violently with water and may ignite upon contact with air. It is toxic by ingestion. It has a slight odor of garlic.
It is not combustible but forms a flammable gas on contact with water or damp air:
Mg3P2 (solid) + 6H2O (liq)?3Mg(OH)2 (solid) + 2PH3 (gas)
Mg3P2 burns in air or oxygen at a dull red heat to form a phosphate, and reacts with chlorine gas to form:
Mg3P2 (solid) + Cl2?MgCl2 + PCl3

Chemical properties

shiny grayish yellow; stable in dry air; decomposed by moisture; can be prepared directly from magnesium and phosphorus; used with igniting agent such as 1% HNO3 in sea flares [KIR82]

The Uses of Magnesium phosphide

Magnesium phosphide has found several uses in industry. It reacts with moisture in the atmosphere to produce phosphine gas which is the substance that is active as a pesticide to control insects and rodents. It is primarily used for indoor fumigation of raw agricultural commodities, animal feeds, processed food commodities, and nonfood commodities in sealed containers or structures, and for outdoor fumigation of burrows to control rodents and moles in nondomestic areas, noncropland, and agricultural areas. Aluminum and magnesium phosphide are formulated as tablets, pellets, impregnated materials and dusts. Aluminum and magnesium phosphide are restricted use chemicals.
With magnesium phosphide, a fumigant is available which can be used for fumigating tobacco even at low temperatures.Magnesium phosphide treatment of dried-fig stacks at 600 and 1000 ppm phosphine for 3 days under tarpaulin were compared with the standard method of control, Methyl bromide. The tested concentrations and exposure periods for Mg3P2 provided 100% mortality in test insects and no negative effect on fruit quality for 9 months in storage under ambient conditions. In contrast, fruit quality with CH3Br did not match that of PH3-treated fruit.
Magnesium phosphide has also been used to control insects in stored almonds, barley, brazil nuts, cashews, cocoa beans, coffee beans, corn, cottonseed, dates, filberts, flower seed, grass seed,millet,oats, peanuts, pecans, pistachio nuts, popcorn, rice, rye, sorghum, soybeans, sunflower seed, triticale, walnuts, wheat, vegetable seed, animal feed or feed ingredients.

General Description

Magnesium phosphide is a white crystalline solid. Magnesium phosphide reacts violently with water and may ignite upon contact with air. Magnesium phosphide is toxic by ingestion. Magnesium phosphide is used to make other chemicals.

Air & Water Reactions

Decomposed by water or moisture in air evolving toxic phosphine and diphosphine, that often ignites [Douda 1966]. May ignite upon contact with air.

Reactivity Profile

Magnesium phosphide is a strong reducing agent. Nitric acid oxidizes Magnesium phosphide with incandescence [Mellor 8:842. 1946-47]. Magnesium phosphide ignites on heating with chlorine, bromine, or iodine vapors, [Mellor, 1940, Vol. 8, 842]. Magnesium phosphide reacts vigorously with most oxidants.
Magnesium phosphide and Magtoxin have not been reported as flammable chemical substances. However, they react readily with water to produce hydrogen phosphide (phosphine, PH3) gas, which may ignite spontaneously in air. Magnesium phosphide is stable to most chemical reactions, except for hydrolysis. Magtoxin, Fumi-Cel, and Fumi-Strip will react with moist air, liquid water, acids, and some other liquids to produce toxic and flammable hydrogen phosphide gas. Magnesium phosphide is more reactive than aluminium phosphide and will liberate hydrogen phosphide more rapidly and more completely at lower temperatures and humidities. Magnesium phosphide is not combustible but forms flammable gas on contact with water or damp air. Magnesium phosphide gives off irritating or toxic fumes (or gases) in a fire and on contact with water or damp air may cause explosion hazard.

Health Hazard

Highly toxic: contact with water produces toxic gas, may be fatal if inhaled. Inhalation or contact with vapors, substance or decomposition products may cause severe injury or death. May produce corrosive solutions on contact with water. Fire will produce irritating, corrosive and/or toxic gases. Runoff from fire control may cause pollution.

Fire Hazard

Produce flammable and toxic gases on contact with water. May ignite on contact with water or moist air. Some react vigorously or explosively on contact with water. May be ignited by heat, sparks or flames. May re-ignite after fire is extinguished. Some are transported in highly flammable liquids. Containers may explode when heated. Runoff may create fire or explosion hazard.

Safety Profile

A poison. Flammable when exposed to heat, flame, or oxidizing materials. Ignites when heated in chlorine, bromine, or iodine vapors. Incandescent reaction with nitric acid. Reacts with water to evolve flammable phosphme gas. When heated to decomposition it emits toxic fumes of POx and phosphine. See also MAGNESIUM and PHOSPHIDES.