Qualitative And Quantitative Polarographic Analysis:

The qualitative analysis of a sample is carried out by matching its E_1/2 with the tabulated values of the ions (given in the text books) in the supporting electrolytes used. It is also advisable to use the log-plot for knowing the correct E_1/2.

Table 8.4:  The half-wave potentials of some of the common ions

Metal ion                                                            Supp. electrolytes

i)1 M NH₃ + 1 M NH₄ Cl                                         E_1/2, V vs. SCE

Cd(II)                                                                                      -0.81

Co(II)                                                                                      -1.29

Cu(II)                                                                                      -0.24

Fe(II)                                                                                       -0.34 and -1.49

Mn(II)                                                                                     -1.66

Mo(VI)                                                                                   -1.71

Ni(II)                                                                                       -1.10

Pb(II)                                                                                      -0.67

Pd(II)                                                                                      -0.75

Se(II)                                                                                       -1.53

Te(IV)                                                                                     -1.21

Tl(I)                                                                                         -0.48

U(VI)                                                                                      -0.8 and 1.4