Appendix

KT <sup>0</sup> ¼ KT

<sup>þ</sup><sup>2</sup> <sup>¼</sup> <sup>1</sup> þ ½SO �<sup>2</sup>

three parts: before, in, and beyond the equivalence point regions.

<sup>α</sup>½FeL2�

Thus, [SO4

error.

S4O6

<sup>2</sup>�/S2O3

curve-smoothing and differentiation.

�2

140 Redox - Principles and Advanced Applications

6. Final comments

1 αCe�SO4

] should be < 0.39 M, to perform the titrimetry with accuracy.

<sup>4</sup> �β<sup>1</sup> <sup>þ</sup> SO �<sup>2</sup>

As a matter of fact redox titrations play a prominent role in volumetric analysis of redox actives species. A systematic study of the bibliography is undertaken in order to ascertain the state of the art concerning to redox titration curves. A method for the determination of titration error in donor/acceptor titrations of displacement and electronic transference reactions has been devised; a hyperbolic sine expression being derived for the titration error, applicable to symmetrical reactions (no polynuclear species being involved in one side of a half-reaction). The hyperbolic sine expression developed is compact and allows calculating the entire titration curve without piecemeal approximations, as usually occurs by dividing the titration curve in

The method has been applied to some experimental systems characteristics of redox titration reactions. The method proposed is also applicable to mixtures of analytes, e.g., Fe(II) þ Tl(I), as well as to multistep redox titrations, e.g., V(II)/V(III)/V(IV)/V(V) system. The forms of the redox titration curves are independent of the concentrations. However, when the concentrations involved are very low the responses of the electrodes are not appropriate. All calculations involved have been checked with the method proposed by "de Levie" [62] for the sake of comparison, and no differences were found in the numerical values obtained by both methods. A diagram for the titration error in function of the difference between the end and equivalence point (pX) is drawn in order to facilitate the graphical calculation of titration

Automatic titrators enable recording automatically the change with potential (E) or pH in titre during a given titration. The accuracy of the measurements can increase with the help of online microcomputer for the control and data acquisition, allowing among the possibility for

At the end of the chapter an appendix including a detailed study of the propagation of systematic and random errors on redox titration error has been carried out and spite of the complex expression obtained first on differentiation, the final expressions formulated were

<sup>2</sup>� remains a challenge, this being a complex problem involving a complete

The extension of the method to nonhomogeneous systems of the type Cr2O7

reformulation of the presented equations, which implies a higher level of difficulty.

very compact. This topic is still under study and it will be dealt in further calculus.

4 <sup>2</sup>

, <sup>α</sup>Ce�SO4 <sup>&</sup>lt; 107:<sup>2</sup> <sup>ð</sup>77<sup>Þ</sup>

β<sup>3</sup> ð78Þ

<sup>2</sup>�/Cr3<sup>þ</sup>, I2/I�, or

<sup>β</sup><sup>2</sup> <sup>þ</sup> SO �<sup>2</sup> 4 <sup>3</sup>
