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Texts from scientific articles

Journal: Analytica Chimica Acta

Oxidizing properties of Perchloric Acid solution

Introduction

The oxidizing properties of hot concentrated perchloric (chloric (VII)) acid are well known. From the oxidations performed the reduction potential of the boiling perchloric acid-water azeotrope is estimated to be +2.0 V. As noted by Smith, this suggests the possibility of using this reagent to oxidize cerium to the tetravalent state. However, no suitable procedure has been published. Indeed, cerium is not oxidized to the tetravalent state by boiling with perchloric acid alone, a fact utilized by O’Laughlin to determine chromium in a chromium-cerium-uranium alloy. Although a faint yellow color appears in cerium solutions during boiling with perchloric acid , the solution becomes colorless when it is cooled and or diluted with water. However , if a small amount of sulphuric (VI) acid is also present, rapid oxidation occurs , indicated by the appearance of the characteristic red-orange color of cerium(IV). This paper presents a satisfactory procedure and optimum conditions for the oxidation of cerium(III) to cerium(1V) using a mixture of hot concentrated perchloric and sulphuric (VI) acids. The procedure is potentially useful for the oxidimetric determination of cerium as well as for the preparation of cerium (IV) solutions that are free of foreign cations and of anions other than sulphate and perchlorate.

Journal: Analytica Chimica Acta

Oxidation of Cerium (III) to Cerium (1V)

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