Properties of Aluminium Triphosphates

Abstract

For aluminium dihydrogentriphosphates, AlH₂P₃O₁₀⋅H₂O (I) and II type of AlH₂P₃O₁₀(II) various fundamental properties, such as solubilities, densities, surface areas, and heats of reaction (e H) and activation energies (E) of their thermal change into aluminium metaphos phate Al(PO₃)₃, were measured. Further, the adsorption of ammonia gas and amines on aluminium triphosphates, as well as structures of cation-exchanged compounds AlM₂P₃O₁₀. n H₂0 (M=Na, K, NH4), were investigated.
1) At room temperature, solu bilities of I and II in water are found to be 0.01 and 0.05g/₁₀0 cm³ H₂O, respectively. The order of their solubilities in various solvents is NH₃>KOH >NaOH>HCl>H₂O. 2) Densities of I and II are 2.31 and 2.60 g/cm³, and su rface areas are 5.2and <1 m₂/g, respectively. 3) For both I and II, the heat of the thermal change into Al (PO₃)₃ was found to be 11.4 kcal/mol, while the activation energies are 25.3 and 61.9kcal/mol for I and II, respectively. 4) The temperature of the thermal change from I into Al(PO₃) was proved to be closely correlated with the quantity of free phosphoric acid adhered to I. 5) Both I and II adsorb basic materials, such as ammonia gas and amines, quite well. 6) The sample of I, which has a stratified structure, is submitted to ion exchange with univalent metallic ions to form AlM₂P₃O₁₀⋅n H₂O (n= 2 for Na salt, for K salt, 2-1 for NH₄ salt). Their crystal structures were destroyed with the decrease of n.