Sodium a-Pentadecatungstodiphosphate, Na

The sodium salt is a white powder, little soluble in pure water, but solubilized in the presence of lithium ions. The solutions are unstable, and conversion to the [a2 P2Wi706,] ° anion is complete after several hours. In molar acetic acid-lithium acetate buffer the half-wave potentials (V vs SCE) are — 0.52 (4e) and —0,78 (2e). The PNMR spectrum of a freshly prepared solution in molar acetic acid-lithium acetate buffer exhibits two equal resonances at -l-O.l and —13.3 ppm (85% H3PO4 reference). In the IR spectrum the P—O bands are at 1130, 1075, and 1008 cm(KBr pellet). As occurs with hydrated compounds, some bands are shifted if the measurements are performed in mineral oil (1130, 1086, and 1009 cm ). 

In a 1-L beaker a sample of 83 g (1.7 x 10 mol) of KgCa-or -P2W,8062] XH2O is dissolved in 3(X)mL of water, and a solution of 48.4g (0.4 mol) of tris(hydroxymethyl)aminomethane in 200 mL of water is added. The solution is left at room temperature for jh and then 80 g of potassium chloride is added. After complete dissolution, a solution of 5S.3 g (0.4 mol) of potassium carbonate in 200 mL of water is added. The solution is vigorously stirred for 15 min, and the white precipitate that appears after a few minutes is filtered on a coarse sintered glass frit, dried under suction for 12h, washed with 50 mL of ethanol for 2 to 3 min air dried under suction for 3 h, washed again with ethanol and dried under suction, and finally air dried for 3 days. Yield 60g(89%). 

POTASSIUM a,-LITHIUM HEPTADECATUNGSTODI-PHOSPHATE, K9[a,-LiP2W,7O6i]-20H2O 

In a 1-L beaker, 21.2 g (0.50 mol) of lithium chloride is dissolved in 500 mL of water acidified with 10 mL of 1 M HCl. After the solution has been allowed 

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