Chapter 4 - Jacobs University

Chapter 2
Experimental
2.2.7 Synthesis of K 14 [P 2 W 19 O 69 (OH 2 )]×24H 2 O
A solution of Na 8 [HPW 9 O 34 ](aq) (10.65g, 3.75 mmol) was added to a solution of
K 7 [PW 11 O 39 ](aq) (4.0g, 1.25mmol), the pH reduced to ca. 6-6.5 and the mixture stirred and
heated at 50 o c. Solid KCl was added until a fine crystalline precipitate appeared. Further KCl (3-
4g) was the added. A crystalline powder separated. Stirring was maintained until room
temperature was reached. The product was then filtered off and washed with chilled water
(10cm -3 ). 7
2.2.8 Synthesis of K 8 [a-SiW 11 O 39 ]×13H 2 O
Sodium metasilicate (5.50g, 25 mmol) was dissolved with magnetic stirring at room temperature
in 50ml of distilled water (Solution A). In a 1-L beaker, containing a magnetic stirring bar,
sodium tungstate (91g, 0.275 mmol) is dissolved in 150 ml of boiling distilled water (Solution
B).
To the boiling solution B, a solution of 4M HCl (82.5 ml) was added dropwise in ~30min, with
vigorous stirring to dissolve the local precipitate of tungstic acid. Solution A is then added and,
quickly, 25ml of 4M HCl was also added. The pH was ~5 to 6. The solution was kept boiling for
1 h. After cooling to room temperature, the solution was filtered if it was not completely clear.
Potassium Chloride (75g) was added to the solution, which was stirred magnetically. The white
solid product was collected on a sintered glass funnel, washed with two 50 mL portion of a 1M
KCl solution, then washed with 50 mL of cold water, and finally dried in air. 8
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