Extractive photometric determination of gallium with 8-quinolinol in layered crystals of bismuth telluride-estimation of the determination limit.

A method for determining microgram amounts of gallium in milligram samples of layered monocrystals of the type A(V)(2)B(VI)(3) is described. For the separation of 1-5 mug of gallium(III) from a large excess of bismuth in a single extraction the recommended conditions are pH 3.6-4.

Colour changes of chemical indicators-VI: metallochromic indicators for direct chelometric titrations of zinc.

Eriochrome Blue SE, Eriochrome Red B, Naphthylazoxine 6S, SNAZOXS, and Zincon have been studied in order to find optimum conditions for their use as metallochromic indicators in direct visual chelometric titrations of zinc. The sharpness of the indicator transitions has been investigated by means of photometric titrations and the colour quality has been specified with the aid of the C.I.

Colour changes of chemical indicators-III: colour specification and its accuracy.

The systematic deviations involved in methods for computation of chromaticity co-ordinates have been studied for the specification of indicator colour changes. The weighted ordinale method (Deltalambda = 10 nm) has proved to be satisfactory for evaluation both of C.I.

End-point evaluation in instrumental titrimetry-II Confidence intervals in extrapolation of linear titration curves.

The random titration error has been evaluated by single linear regression analysis of both linear branches of titration curves. As a simplification the confidence interval of a titration is estimated by substituting divergent linear confidence limits for the curved confidence limits of both branches of the curve. The influence of the angle between both branches upon the confidence interval of a titration has also been evaluated.

End-point evaluation in instrumental titrimetry-I Linear extrapolation of hyperbolic titration curves.

A method is described for the estimation of a systematic titration error which is introduced by linear extrapolation of hyperbolic titration curves in amperometric, photometric, and other instrumental titrations. It is assumed that the titration is based upon a single-step ion-association reaction mA + nB right harpoon over left harpoon A(m)B(n) and that the measured physical property falls within known minimum and maximum values. The procedure is suitable for end-point determination, even when the titration curves have extensive curvature, and for predicting the choice of optimum experimental conditions for a given titration.