What method is used to measure sodium sulfate and sodium thiosulfate in desulfurization liquid?

so4- This can be done through barium hydroxide solution. Barium carbonate is soluble in acid. Sodium thiosulfate is not very clear.

Sodium thiosulfate is easily oxidized to sodium sulfate, which will affect the determination of sodium sulfate.

For sodium sulfate, use the barium sulfate gravimetric method or the lead salt dropback method to determine sulfate radicals. Thiosulfate can be determined by iodometric method. Of course, two test solutions must be taken separately. Very easy to measure.

How to eliminate the influence of sodium thiosulfate?

Take two separate test solutions. Sodium thiosulfate will not interfere with the determination of sulfate radicals.

Take two separate test solutions. "Sodium thiosulfate does not interfere with the determination of sulfate radicals. ” I have some doubts, I don’t know if it will work!

Post by Haiyou, please understand that Na2S2O3 in the desulfurization solution is a by-product of the desulfurization process. Its content is not only a reflection of the desulfurization ability of the solution, but also an important reference data for operators when adding materials to the desulfurization solution. Therefore, the analysis of the Na2S2O3 content in the desulfurization solution is very important. Since the desulfurization solution contains reducing ions such as S2- which interfere with the determination of Na2S2O3, it is necessary to find a suitable method to eliminate the interference of reducing ions such as S2- during the measurement. Generally, there are three methods for measuring Na2S2O3 content: (1) Add zinc carbonate suspension to the desulfurization solution to precipitate S2- and other interfering ions, filter it, and take the filtrate to analyze the Na2S2O3 content using iodometric back titration ； (2) Add excess cadmium chloride to the desulfurization solution to precipitate interfering ions such as S2, and directly use iodometric titration to analyze the Na2S2O3 content ； (3) Add an appropriate amount of boric acid to the desulfurization solution, heat it to remove main interfering ions such as S2- in the solution, after cooling, add acetic acid to acidify, and then use iodometric back titration to analyze the Na2S2O3 content. Acetic acid-sodium acetate buffer solution pH≈4.5 ； Starch solution 5g/L ； Iodine standard solution c(1/2 I2)=0.1mol/L ； Sodium thiosulfate standard solution c (Na2S2O3) = 0.100 2mol/L ； Acetic acid solution 10% ； Boric acid solution 100 g/L ； Na2S standard solution c(1/2Na2S)=0.095 2mol/L. Accurately transfer a certain amount of Na2S2O3 standard solution and Na2S standard solution, add 10 mL of boric acid solution and 5 mL of acetic acid solution, heat and boil for 10 minutes. After cooling, add 5 mL of acetic acid solution, add 10 mL of acetic acid-sodium acetate buffer solution, and 10.00 mL of iodine standard solution. Use starch as an indicator and back-titrate with sodium thiosulfate standard solution.

Test of sodium thiosulfate 1. Experimental principle: I2 + 2S2O32- = 2I- + S4O62- Iodine and starch can form a blue soluble adsorbed compound in the presence of I-. When sodium thiosulfate is added, sodium thiosulfate reacts with iodine, causing the blue color to disappear. 2. Experimental reagents: 1) Iodine-potassium iodide solution: Dissolve 7g of iodine and 18g of potassium iodide in 100ml of water and dilute to 1000ml. Store in brown reagent bottle, protected from light. 2) 10g/L starch indicator, ready for use. 3.Method: Take 2 ml of test sample, add 2 drops of starch indicator, shake well, add 0.05 ml of iodine-potassium iodide solution, shake well immediately and observe the color.

I think the iodometric method can definitely accurately measure thiosulfate ions, because other ions do not interfere with it. In the following steps, I recommend adding excess hydrochloric acid first, because carbonate will generate CO2, thiosulfate will generate SO2 and S, and the introduced chloride ions will not interfere with the measurement. In this way, interfering ions can be removed. After filtering with quantitative filter paper, use the EDTA method or gravimetric method to measure sulfate. It is not recommended to measure sulfate directly. Barium thiosulfate and barium carbonate are both insoluble in water and only soluble in acid. ； And if you precipitate first and then add acid, and use EDTA method or gravimetric method to measure, the results will be distorted.