OXIDATIONS WITH CERIUM IV SULPHATE SOLUTION

Cerium(IV) sulphate is a powerful oxidising agent its reduction potential in 

0M sulphuric acid at 25 °C is 1.43 0.05 volts. It can be used only in acid solution, best in 0.5M or higher concentrations as the solution is neutralised, cerium(IV) hydroxide [hydrated cerium(IV) oxide] or basic salts precipitate. The solution has an intense yellow colour, and in hot solutions which are not too dilute the end point may be detected without an indicator this procedure, however, necessitates the application of a blank correction, and it is therefore preferable to add a suitable indicator. 

The advantages of cerium(IV) sulphate as a standard oxidising agent are  

Cerium(IV) sulphate solutions are remarkably stable over prolonged periods. They need not be protected from light, and may even be boiled for a short time without appreciable change in concentration. The stability of sulphuric acid solutions covers the wide range of 10-40 mL of concentrated sulphuric acid per litre. It is evident, therefore, that an acid solution of cerium(IV) sulphate surpasses a permanganate solution in stability. 

Cerium(IV) sulphate may be employed in the determination of reducing agents in the presence of a high concentration of hydrochloric acid (contrast potassium permanganate, Section 10.92). 

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Other examples are the use of osmium(VIII) oxide (osmium tetroxide) as catalyst in the titration of solutions of arsenic(III) oxide with cerium(IV) sulphate solution, and the use of molybdate(VI) ions to catalyse the formation of iodine by the reaction of iodide ions with hydrogen peroxide. Certain reactions of various organic compounds are catalysed by several naturally occurring proteins known as enzymes. 

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