40. Solving a chemistry problem

1. Justify the principle of determining impurities of sulfates and cyanides in the pharmacopoeial preparation "Kalii iodidum". Article requirements:
sulfates. 3 g of the drug is dissolved in 30 ml of water. 10 ml of this solution must pass tests for sulfates not more than 0.01% in the preparation).
cyanides. To 5 ml of the same solution add 5 drops of ferrous sulfate solution, 2 drops of ferrous chloride solution, 1 ml of sodium hydroxide solution and heat slightly. After acidification with HCl, the solution should not turn blue.
Write the sequence of the definition, the reaction equations and make the necessary calculations.