116. Solving a chemistry problem

1. Justify the definition of sulfites and sulfates in sodium thiosulfate according to the method of GF X (Article 441): 0.1 g of the substance is dissolved in 1 ml of water, 4-4.5 ml of 0.1 M iodine solution is added until the solution turns yellow. The latter should not show an acidic reaction. To the same solution is added 2 ml of water and 1 ml of barium nitrate solution. The liquid must remain clear. Support your answer with the chemistry of the reactions.