Preparation of Tungsten Bronzes

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

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Preparation of Tungsten Bronzes. Three methods have been successfully used by the Cornell group for making single crystals of Ma.W03 ... 

Tungsten bronzes can be prepared by a variety of reductive techniques but probably the most general method consists of heating the normal tungstate with tungsten metal. They are extremely inert chemically, being resistant both to alkalis and to acids, even when hot and concentrated. Their colours depend in the proportion of M and W present. In the case of sodium... 

Molybdenum and Tungsten Bronzes.—The results of the majority of studies of studies of new bronze phases are summarized in Table 9. Sno.2W03 and Sno.3 WO3 have been prepared and their crystal structures determined. Whether they are bronzes is debatable since they do not involve a host lattice of WO ... 

At IREQ, besides the participation in the field tests run by the engineers of Hydro-Quebec (12), the main effort has been to tackle fundamental problems in the field of electrocatalysis (18-22) and of anodic oxidation of different potential fuels (23-26). A careful and extensive study of the electrochemical properties of the tungsten bronze has been carried out (18-20) the reported activity of these materials in acid media for the oxygen reduction could not be reproduced and this claim by other workers has been traced back to some platinum impurities in the electrodes. Some novel techniques in the area of electrode preparation are also under study (21,22) the metallic deposition of certain metals on oriented graphite show some interesting catalytic features for the oxygen reduction and also for the oxygen evolution reaction. 

Crystals of the various alkali tungsten bronzes were prepared by electrolysis from a melt of the appropriate alkali tungstate and W03. The electrolytic cell consisted of a glazed ceramic crucible, a Chromel wire cathode, and a graphite anode. Crystals were obtained under the following conditions temperatures of the melt, 750° to 900° C. current through the cell, 15 to 50 ma. time of electrolysis, 12 to 24 hours. 

The hydrogen molybdenum and tungsten bronzes H MoOj and H WOj, where X = 0.6, may be prepared by electrochemical reduction of WO3 or M0O3. They violate the condition that the metal must be a hydride former, but they cannot be prepared by direct reaction of the oxide with Hj, and they differ from other compounds because the hydrogen prefers to bond with oxygen rather than the metal. 

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