Polarographic Determination of Fluoride

Abstract

Willard and Dean¹ have described a polarographic method for the determination of aluminium, based on the measurement of the polarographic step produced by the reduction of ‘Solochrome Violet R.S.’ (sodium salt of 5-sulpho-2 hydroxy-α-benzene azo-2 naphthol), which is known as ‘Pontachrome violet S.W.’ in the United States. This compound produces a step of half-wave potential about 0.3 V. vs. the saturated calomel electrode in an acetate buffer solution of pH 4.6. Addition of aluminium to a solution of this dye causes this polarographic step to be reduced in height and a second step to appear at a point about 0.2 V. more negative. The sum of the height of these two steps is equal to the height of the original step, and the size of the second step is proportional to the concentration of aluminium present.