70. Solving a chemistry problem

31. A weighed portion of the drug sodium salicylate weighing 0.1996g. placed in a 50 ml flask and made up to the mark with titration solution. Then 15 ml of the resulting solution was transferred into a 50 ml volumetric flask, brought to the mark with a titration solution and titrated with 0.1 M Na2S2O3. 7.89 ml of Na2S2O3 was used for titration. Write a diagram of the quantification process, indicate the indicator, fix the equivalence point. Calculate the titer and content of the active substance in the sample. (The molecular weight of the analyte is 160.11). 30 ml of titrant was used for the control experiment.