Aluminum phosphide with molecular formula AlP is dark gray or yellow crystals in its pure state. Formulations of aluminum phosphide as a rodenticide and fumigation insecticide in the form of flat tablets, spherical tablets, pellets, granules and dust have different trade names such as Phostek® , Alphos®, Fastphos®, Fumitoxin®, Gastoxin®, Max-Kill®, Phostoxin®, Celphos®, Synfum®, Phosphume® and Quickphos®. The rice tablets contain phosphide in white, gray, green to brown colors and the approximate weight of each tablet is 3 grams. A three-gram tablet containing aluminum phosphide in proximity to moisture, could produce almost one gram of phosphine gas (PH3). In Iran, flat tablets of aluminum phosphide are imported and mostly available under the brand name Phostoxin®, which contain aluminum phosphide (56% of the weight of the tablet), urea and ammonium carbamate and produce phosphine, ammonia and carbon dioxide gas due to contact with water or water vapor. This type of rice tablets is used for industrial and agricultural purposes. Another type of rice tablets in the country, which was prepared for home use and was available with popular and common names such as vegetable rice tablets or garlic tablets or banana tablets, does not contain any metal phosphide as an effective ingredient and only contains garlic extract or pepper, sodium chloride, talc and starch, and of course it does not contain the toxic effects of aluminum phosphide. Phosphine gas with a molecular formula of PH₃ and molecular weight of 34 is a colorless, toxic, flammable gas and heavier than air. Its smell is similar to garlic or rotten fish, which can be detected at a concentration of 2ppm. The reason for the smell of phosphine gas is the presence of impurities such as diphosphine (P₂H₄), methane, arsine, hydrogen and substituted phosphines, otherwise pure phosphine gas has no smell.n Spontaneous ignition of phosphine gas in air has been reported, which is mostly related to the presence of aluminum oxide and diphosphine gas.
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