
TY  - JOUR
A1  - Smith, Bradley J. 
A1  - Patrick, Vincent A. 
T1  - Quantitative Determination of Sodium Metatungstate Speciation by <emph type="7">183</emph>W N.M.R. Spectroscopy
JF  - Australian Journal of Chemistry
JO  - Aust. J. Chem.
Y1  - 2001
VL  - 53
IS  - 12
SP  - 965
EP  - 970
KW  - Metatungstates, paratungstates, polyoxometallate.
UR  - https://doi.org/10.1071/CH00140 
N2  - The speciation and equilibria of sodium metatungstate, Na6&#91;H2W12O40&#93;, has been determined by a combination of 183W n.m.r. spectroscopy and gravimetry over the p&#91;H&#93; range 4.5&#8211;10.0. The use of n.m.r. spectroscopy allowed the direct observation of polytungstate anions in aqueous solution and high concentration (0.25 mol l&#8211;1). Sodium metatungstate, with the progressive addition of base, was found to decompose to paratungstate A, &#91;W7O24&#93;6&#8211;. Paratungstate A then slowly converted to paratungstate B, &#91;H2W12O42&#93;10&#8211;. The kinetics of equilibrium was found to be slow, requiring up to 8 months to stabilize. With the addition of further base paratungstate B decomposed to orthotungstate, WO42&#8211;. Logarithmic constants (logK) for these transformations were determined as 195, 20 and 118, respectively. The solubility product for sodium paratungstate B was determined to be 6.89 ( 0.80) 10&#8211;6. 
ER  -

