Chapter 4 - Jacobs University

Chapter 2
Experimental
2.2.3 Synthesis of K 14 [As 2 W 19 O 67 (H 2 O)]
To a solution of 94g (285 mmol) of Na 2 WO 4 ×2H 2 O in 250 mL of distilled water, 4.45g (22.5
mmol) of As 2 O 3 were added subsequently. The solution was stirred for few minutes and pH was
adjusted to 6.3 by addition of 12 M HCl (37%).The solution was heated to ~80 o C for 10 min,
and after cooling 35g (45 mmol) of KCl was added to the solution at room temperature. The
solution was stirred again for 15 mins and the formed precipitate was filtered off and dried at ~
80 o C in an air oven overnight. It was characterized by FTIR spectroscopy and compared to the
reported spectrum. 3
2.2.4 Synthesis of A & B Na 8 [HAsW 9 O 34 ]×11H 2 O (A & B-Type AsW 9 O 34 )
30 g of Na 2 WO 4 ×2H 2 O and 2.3 g of As 2 O 5 were dissolved in 40 mL of distilled water with
stirring. Glacial CH 3 COOH was added drop wise until the pH changed to 8.1 or 8.3 the solution
turned milky on addition of CH 3 COOH but after stirring for a period of 30 min a heavy white
precipitate was formed. The precipitate was filtered on a frit and air dried. The product obtained
is A-AsW 9 O 34 . If the above product is kept in the oven for a period of 2hrs at ~140 o C it
isomerizes to give B-AsW 9 O 34 . This synthesis was done with slight modification to the published
method. They were characterized by FTIR spectroscopy and compared to the A & B reported
spectrum. 4
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