Sodium paratungstate

Preparation of Sodium Paratungstate, a. Pour 20 ml of a 50% sodium hydroxide solution into a 100-ml porcelain beaker provided with a mechanical mixer, put the beaker on a water bath, and introduce the calculated amount of a freshly precipitated wet suspension of tungstic acid in small portions while vigorously stirring. At the end of the reaction, the pH of the solution should be 6-6.5. Filter the solution, evaporate it a little, and let it stand for 24 hours. Separate the formed crystals by filtration and dry them in the air. 

Perform a similar experiment with sodium paratungstate, keeping the temperature within 600 °C. What properties do tungsten bronzes exhibit Where are they employed ... 

H2O, or 2Na,0.Ba0.7W03.14H20, separates when excess of barium hydroxide solution is added to a boiling solution of sodium paratungstate and the mixture is allowed to cool. ... 

Zettnow, who obtained it by the addition of hydrochloric add and barium chloride to a solution of sodium paratungstate which contained sufficient phosphoric acid to jJrevent precipitation by hydrochloric acid alone according to Scheibler the precipitate so formed is not of definite composition. 

The salt, 2K20.5 V03.4H20, is obtained as an amorphous precipitate by adding a cold concentrated solution of the normal salt to excess of glacial acetic acid it is soluble in 20 parts of water, and the solution on evaporation at ordinary temperatures deposits prismatic tables. The solution decomposes on boiling. This salt may also be produced by the addition of potassium chloride to a hot solution of sodium paratungstate, or by crystallisation from a hot solution of potassium paratungstate. ... 

Silver Paratungstate, 5Ag.30.12W03.28H20, is obtained as a whitish-yellow crystalline precipitate on adding a solution of a silver salt to a solution of sodium paratungstate. After drying at 60° C. it contains SHjO. It melts at a red heat, and on cooling solidifies to a white lustrous crystalline mass. 

Solubility data for sodium paratungstate have been given as follow s ... 

Xa.,W20j.2H.,0 is obtained as white radiating crystals by the addition of hydrogen peroxide to a hot solution of sodium paratungstate and evaporation of the mixture in a vacuum. The crystals are easily soluble in water. 

A solution is prepared by heating a mixture of 7.8 g. of sodium paratungstate (prepared as above) and 70 ml. of water. This mixture is then reacted with a warm, saturated solution of 2.4 g. of... 

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