0731. Solving a chemistry problem

92. A sample of 0.8325 g of chromium-nickel alloy containing small amounts of bismuth and antimony as impurities was dissolved in concentrated nitric acid; the resulting solution is neutralized with excess ammonium hydroxide; the chromium hydroxide precipitate used as a collector for the coprecipitation of bismuth and antimony, after appropriate treatment and centrifugation, was dissolved in 25 ml of a 5.0 M sulfuric acid solution. For polarography, 10 ml of solution was taken into the cell and an alternating current polarogram was taken in the range from 0.2 to –0.5 V relative to the bottom mercury. The height of the peaks (the difference in peak potentials against a given background is 150 mV) was 15 mm for bismuth and 28 mm for antimony. When polarographing a standard solution containing 1.0 • 10–5 mol/L salts of these materials under similar conditions, the peak heights turned out to be 42 mm and 75 mm, respectively. Calculate the content of the metals Bi and Sb in the alloy.