The importance of statistical errors on the different parameters involved in the Gran addition technique has been discussed in Part I of this series'. In order to obtain optimal predtsion in volume V, obt;dmc~ b,v e~W4xsasjo4 fm paramekrs V miw V,, C, C,, N (for definitions, see Part I) should be chosen such that : C+C!l .v,,,= co+-cs vo R min where Rmin is a function of the number of additions (N)* and has a theoretical value of 2.7 for N = 10, when the extrapolation is carried out statistically. In this paper only the statistical method will be considered. The results outlined in Part I were obtained on the assumption that the electrode slope is known with great accuracy. However the electrode slope, r, is determined experimentally and the error, Ar, incurred in r causes a systematic error in the determination of VX, in the addition method. The occurrence of this error has led several authors2*' to avoid using the Gran method in the form described here. These authors determine EL, r and C,,, using the least-squares lit method, on the basis of the relation which fits best with the experimental curve E = f( V). The present work was undertaken in order to establish the role played by Ar in the determination of V, obtained by extrapolation. All calculations were performed on the CDC 3800 computer of the University of Geneva. Appropriate programs enabled the figures to be printed on the printer. These program a~= a=+a%a% ffwm %+,z a~&or. THEORETICAL CALCULATIONS OF ERROR IN V, CAUSED BY .Ar ' * (Vi+ v,) 1 where l/r = k (definitions of all parameters are .given in Part I) On linearizing eqn. (1) one gets: