4. A sample of antimony weighing m (g) was transferred into solution and aluminum contained as an impurity was isolated in the form of oxyquinolinate. After washing and dissolving the precipitate in hydrochloric acid, the coulometric titration of oxyquinoline was carried out with bromine generated from KBr at a constant current of 8.5 mA. The equivalence point found biamperometrically corresponded to the electrolysis time τ. Calculate the mass fraction (%) of aluminum in antimony according to the following data, according to the number of your option (see Table 3)
Table 3
Variant No. Mass of antimony m (g) Electrolysis time τ, s
4 0.6999 169

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