Permanganate molybdenum determination

Volumetric methods for determining columbium are rapid and fairly satisfactory since tantajum does not interfere. But tungsten, molybdenum, and titanium must be completely removed. The methods depend on the reduction of pentavalent columbium to the trivalent condition by means of zinc, then the oxidation by standard permanganate. Taylor s method3 makes the reduction in a Jones reductor and the titration in an atmosphere of C02. Levy s method4 carries out the reduction and titration in an atmosphere of hydrogen in a conical flask from which the air is excluded. 

Arsonium salts have found considerable use in analytical chemistry. One such use involves the extraction of a metal complex in aqueous solution with tetraphenylarsonium chloride in an organic solvent. Titanium (TV) thiocyanate [35787-79-2] (157) and copper(II) thiocyanate [15192-76-4] (158) in hydrochloric acid solution have been extracted using tetraphenylarsonium chloride in chloroform solution in this manner, and the Ti(IV) and Cu(II) thiocyanates determined spectrophotometrically. Cobalt, palladium, tungsten, niobium, and molybdenum have been determined in a similar manner. In addition to their use for the determination of metals, anions such as perchlorate and perrhenate have been determined as arsonium salts. Tetraphenylarsonium permanganate is the only known insoluble salt of this anion. 

A number of transition metals can be determined conveniently if their cations undergo a definite change of oxidation state see Oxidation Number) on titration with a standard solution of potassium permanganate, potassium dichromate, cerium(IV) sulfate, or ammonium hexanitratocerate(IV). Several visual indicators have been proposed, including diphenylamine and its derivatives, xylene cyanole FF, and especially A-phenylanthranilic acid and tris(l,10-phenanthroline)iron(II) sulfate ( ferroin ). Solutions of have been used in the determination of iron, copper, titanium, vanadium, molybdenum, tungsten, mercury, gold, silver, and bismuth, and standard solutions of and Sn F U, and and Mo have also... 

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