Search

The oxidation of ferrocyanide by hypobromite and the optical density of the yellow colour of ferricyanide thus developed has been studied with the aid of a Hilger Spekker Absorptiometer Model H 760. A violet filter having maximum transmission in the range of 420–450 mμ was used. Series of experiments showed that quantitative oxidation of ferrocyanide occurred in the pN range 8–8.5 (bicarbonate buffer) and the colorimetric titration may be used for the standardisation of hypobromite. The results compared favourably with those obtained by amperometric titration of hypobromite against sodium arsenite as a primary standard.

The gradual disappearance of the yellow colour of ferricyanide with the addition of vanadyl ions in alkaline medium has been made the basis of the quantitative determination of both vanadium and ferricyanide. The colorimetric titrations were carried out with the aid of a Hilger Spekker Absorptiometer with a blue filter having maximum transmission in the range of 450–500 mμ. It is shown that the accuracy of the results compares favourably with those obtained by other standard procedures.