Raman spectroscopy has been applied to the study of the pH-dependent decomposition of 12-molybdophosphoric acid, H3(PMo12O40), and 12-molybdosilicic acid, H4(SiMo12O40), in aqueous solution. The decomposition schemes involving several smaller polymeric molybdate species, proposed from indirect techniques such as electrochemistry, are confirmed. Identification of the species present in solution is made by comparison of the Raman spectra to the spectra of known species, except in the case of (PMo11O39)7-, for which the spectrum is reported for the first time.
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