The determination of bismuth in bismuth concentrates by chelatometric titration / A. Hitchen and G. Zechanowitsch, Extraction Metallurgy Division. : M34-20/173E-PDF

“Two methods for the determination of bismuth in bismuth concentrates are described, both based on titration of the bismuth with sodium ethylenediamine-tetraacetate (EDTA). In one method, the end-point is detected visually by means of xylenol orange indicator, whereas in the other, the end-point is detected amperometrically using a rotating platinum electrode maintained at + 1.2 volts vs the s.c.e. The advantages and disadvantages of each method are discussed. The effects of a number of elements peculiar to the particular sample material analyzed here and of others commonly found in other bismuth concentrates were investigated. Procedures for the elimination of those that interfered were investigated and their effectiveness has been established. In particular, a rapid acid attack-volatilization procedure for the simultaneous dissolution of the sample and volatilization of arsenic, antimony, and tin (without significant loss of bismuth) has been developed and is presented here. A hitherto undescribed interference due to aluminum, when xylenol orange is used, has been observed and causes and remedies for it are discussed. It is also shown that aluminum, which interferes when xylenol orange is used, does not interfere when amperometric end-point indication is used, whereas iron and ascorbic acid, which interfere with the amperometric end-point method, do not interfere with the xylenol orange end-point"--Abstract, p. i.

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