The structures and morphologies of various commercial forms of ammonium paratungstate have been studied and related to the processes used for the production of this material. High temperature crystallization processes are shown to produce the monoclinic pentahydrate 5(NH4)2O.12WO3.5H2O which yields a cuboid or equiaxed monoclinic powder morphology. Crystallization at room temperature produces the orthorhombic undecahydrate 5(NH4)20.12WO3.11H2O which has a lath-like particle morphology. Freeze-dried ammonium paratungstate is shown to be amorphous in nature, to have a chemical composition approaching that of the undecahydrate, and to have a porous, multiparticulate agglomerate particle morphology. The apparent densities of the samples of ammonium paratungstate are explained in terms of the particle morphologies.
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