Crystalline solid. Decomposes at 218C. Insoluble in water; soluble in hydrochloric acid, weak sulfuric acid, and sodium hydroxide solution.
In acrylonitrile polymer fiber finishes.
Decomposes to toxic phosphine.
Flammability and Explosibility
Flammable
During synthesis, if the pH is not well controlled, it is highly likely that Al(OH)3 will be obtained;
If one simply mixes two solutions of aluminum sulfate and sodium hypophosphite, it seems to be prone to double hydrolysis:
Al(3+) + 3H2PO4(-) + 3H2O = Al(OH)3 + 3H3PO2
Aluminum hypophosphite is only made if aluminum sulfate is kept in excess;
Even if aluminum hypophosphite is made, its high-temperature process produces toxic gases: Al(H2PO2)3 = AlPO4 + 2PH3
As you can see, aluminum hypophosphite does not seem to be an environmentally friendly flame retardant.
