10.9 : 氧化还原滴定法：其他氧化剂和还原剂

In addition to iodine, several other oxidizing or reducing agents can be employed as titrants in redox titrations.

Potassium permanganate is a strong oxidizing titrant that reduces from manganese(VII) to manganese(II) in a strongly acidic solution.

Here, the purple permanganate acts as a self-indicator because manganese(II) is colorless.

Reducing analytes can also be titrated using acidic cerium(IV) solutions while using redox indicators for end point detection. In the titration, the analyte is oxidized while cerium(IV) reduces to cerium(III).

Potassium dichromate is a moderately strong oxidizing titrant that reduces from chromium(VI) to chromium(III) in acidic solutions. The dichromate end point is observed using a redox indicator.

In contrast, most reducing titrants are oxidized by atmospheric oxygen, so they are rarely used for the direct titration of oxidizing analytes.

For instance, thiosulfate is used indirectly as a typical reducing titrant for iodometric titrations.

However, an acidified iron(II) solution can be used to titrate some strong oxidizing analytes, such as cerium(IV), chromium(VI), and vanadium(V).