2-Ethylpyridinium dodecatungstate(Vl) monohydrate was synthetized and characterized as ~-(CsH4NHC2Hs)sH [HzW1204o]. H20 by chemical analysis and electronic, IR and ~H NMR spectral studies.The UV spectra showed the characteristic maximum absorption at 260 nm for the metatungstate anion. The two central protons in the anion were also characterized via I R and J H NMR spectroscopy.The thermal behaviour of this compound was investigated by thermogravimetric and derivative thermogravimetric methods. The TG curves revealed four main steps of decomposition, viz. dehydration, partial organic base decomposition and pyrolysis of the organic base, leading to the formation of WO 3 in the final stage.The intermediates obtained at the end of the various thermal decomposition steps were studied via the IR spectral data on the residues obtained by isothermal heating of the compound at different temperatures.Kinetic parameters for the dehydration reaction were obtained through two methods of analysis.At temperatures lower than 100 ~ the acidification of alkali metal tungstate solutions results in the formation of various polynuclear species. The results of a great number of studies to characterize the polytungstate species have been exhaustively reviewed by several authors [1][2][3][4].The pH inflection observed at H+/WO42-= 1.5 in potentiometric titrations of aqueous alkali metal tungstates corresponds to the formation of pseudometatungstate (0). The latter anion is formed rapidly, but is metastable in solution and is slowly transformed first into "tungstate-X" and finally into true metatungstate, e-[H2W1204o] 6-, the thermodynamically stable product. At 50 ~ and 5 mM tungstate concentration, some 15 days are required for complete conversion to meta-

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