3.第三类电极 金属与两种具有共同阴离子或络合剂的难溶盐或难离 解的络离子组成,M|M,N,N+ Pb PbC204 (S), CaC204(), Ca Pb2++2e→Pb E=EOz+n tInPb2+ 2F RT, Ks(PbC204) RT Ps"' P 2F"xm(Cac,O,*2F nace RT e +-lna 2F Ksp(PbC204)=pa+aco- Ksp( CaC204)=aca+.,o Ksp(PbC204) Ksp( Cac204)3. 第三类电极 金属与两种具有共同阴离子或络合剂的难溶盐或难离 解的络离子组成，M|MX，NX，Nn+ K (CaC O ) K ( PbC O ) a a K ( PbC O ) a a K (CaC O ) a a lna F RT E lna F RT K (CaC O ) K ( PbC O ) ln F RT E lnPb F RT E E Pb e Pb Pb | PbC O ( S ),CaC O ( S ),Ca sp sp Pb Ca sp Pb C O sp Ca C O Ca Ca sp sp Pb ,Pb Pb ,Pb 2 4 2 4 2 4 2 4 0 2 4 0 2 4 0 2 2 2 2 4 2 4 2 2 2 2 4 2 2 2 4 2 2 2 2 2 2 2 2 2 2 = ⋅ = ⋅ = ⋅ + ′ = = + + = + + → + + + − + − + + + + + + +