Chapter 17, Problem 87AP

In some old European churches, the stained-glass windowshave so darkened from corrosion and age that hardly anylight comes through. Microprobe analysis showed that tinycracks anddefects on the glass surface were enriched ininsoluble Mn(III) and Mn(IV) compounds. From AppendixE, suggest a reducing agent and conditions that might successfullyconvert thesecompounds to soluble Mn(II) withoutsimultaneously reducing Fe(III) (which gives the glassits colors) to Fe(II). Take ${\text{MnO}}_{\text{2}}$ as representative of theinsoluble Mn(III) and Mn(IV) compounds.