Preparation of Potassium Hexachloromolybdate III

Preparation of Potassium Hexachloromolybdate(III). Perform the experiment in a fume cupboard ) Dissolve 50 g of molybdic anhydride in 250 ml of concentrated hydrochloric acid. Spill the molyb-denum(Vl) oxide into the beaker in small portions as it dissolves during 6 hours. If the solution is turbid, filter it through a glass filter (prepare the solution beforehand). 

Transfer the solution into thick-walled glass beaker 1 containing porous clay cylinder 2 that functions as a diaphragm and anode vessel (Fig. 130). Fill the anode compartment with 12 N hydrochloric 

Connect the electrolyzer to a d-c source at about 2 V. Use rheostats and 7 2 to set a current of about 5 A. The current density during the electrolysis must remain constant and be 0.07 A/cm . Perform the electrolysis until a sample of the solution diluted with water becomes red (in about eight hours). Write the equations of the reactions 

Pour the solution obtained in reduction into a conical flask preliminarily filled with carbon dioxide and heat the reaction mixture in a stream of carbon dioxide in a water bath during an hour. Introduce 35 g of potassium chloride into the hot solution in small portions and evaporate the solution up to one-third of its volume. Close the flask with a rubber stopper and let it stand in the cold overnight. 

Separate the formed crystals using a glass funnel with a filtering bottom. Wash them on the filter with absolute ethanol and dry them in a desiccator over phosphorus(V) oxide. Weigh the substance and calculate the yield in per cent. 

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