Bromine amperometric titrations with

Amperometric-Coulometric Apparatus, automatic, suitable for bromine index titrations with variable generator current and timer. A typical circuit diagram of suitable equipment is shown in Fig. l. ... 

A bromination method has been described116 based on amperometric titration at 0.3 V of the =Si-H groups in the presence of double bonds in 4 m hydrochloric acid medium with 0.1 M-methanolic bromine saturated with sodium bromide with a rotating platinum micro-electrode, then analogous titration of the double bonds after treatment with methanolic potassium hydroxide to destroy the silidyne groups. The content of silidyne groups is then found by difference. 

The possible method of following the concentration of bromine as a measure of the total amount of unsaturation has not yet been very widely used (see amperometric titration on p. 163), but rather a method which involves a reaction with maleic anhydride. 

EXAMPLE 15-1 Consider the titration of arsenic(III) with bromate. In a hydrochloric add solution containing excess bromide, the end point can be determined potentiometrically by using the bromine-bromide couple as the potential-determining system. Alternatively, the same titration can be followed amperometrically by measuring the diffusion-controlled current due to excess bromine slightly beyond the end point. At an initial concentration of 5 x 10 M arsenic(III), the potentiometric titration can barely be carried out, because several minutes are required for electrode equilibrium at each point of the titration. The amperometric method gives a successM end point even at 5 x 10 M arsenic(III), the whole titration taking only a few minutes. ////... 

Another important amperometric titrant is bromine solution, which undergoes stoichiometric oxidation-reduction reactions with many substances such as As(III), Sb(III), ammonium salts, and others. Often the titration involves adding an excess of KBr to an acidified solution of the substance to be oxidized and then titrating it with potassium bromate solution. Bromine is thereby generated in situ. 

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