Weigh 1~1.5g sample (accurate to 0.0001g) into a 250ml dry iodine measuring flask, and record the weight m. Add 20ml of water, 3g of potassium iodide, and 10ml of sulfuric acid solution (10%), and shake it up to dissolve completely, place in a dark place for 10-15 minutes, add about 80ml of water, titrate with sodium thiosulfate standard titration solution, and add when near the end 3ml starch indicator solution, continue to titrate until the blue color of the solution fades as the end point.
V--The value of the volume of sodium thiosulfate standard titration solution, in milliliter (mL);
c--The exact value of the concentration of sodium thiosulfate standard titration solution, the unit is moles per liter (mol/L);
0.404- -The mass of iron nitrate [(Fe (NO3) 3●9H2O)] equivalent to 1.00mL with sodium thiosulfate standard titration solution [C (Na2S2O3)=0.1000mol/L] in grams;
m---Sample mass, g.
