Separate analysis of free chlorine and sodium hypochlorite in light brine from the ion membrane outlet
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This post was last edited by sunjl1981 on 2013-1-6 23:34. I would like to ask you if the free chlorine and sodium hypochlorite in the light brine from our ion membrane outlet tank can be analyzed separately? This is how our laboratory analyzes sodium hypochlorite in light brine from the ion membrane outlet.: Principle: In acidic solution, free chlorine and sodium hypochlorite can oxidize iodide ions into iodine. Free iodine is titrated with sodium thiosulfate standard solution. The reaction formula is as follows. Cl2+2KI=2KCl+I2 NaClO+2KI+2CH2COOH=NaCl+H2O+2CH2OOK+I2 I2+2Na2S2O3=2NaI+Na2S4O6 Reagents and solutions Sodium thiosulfate standard solution ； Acetic acid solution ； Potassium iodide solution ； Starch solution. Measurement steps: Add potassium iodide solution and acetic acid solution to the iodine flask, then quickly add the sample that has been cooled to room temperature, cover it and shake well. After letting it stand in a dark place, titrate with sodium thiosulfate standard solution through a microburette. When the solution is near the end point, it turns light yellow. Add starch indicator and continue titrating until the blue color just disappears. Do a blank test at the same time. Calculate the content of chlorine and sodium hypochlorite (available chlorine) (X) using the following formula (calculated as chlorine) X (mg/L) = c. (v1-v2) * 0.3545 * 1000/25 where v1——the volume of sodium thiosulfate standard solution, ； v2————The volume of sodium thiosulfate standard solution in blank test, ； c————The concentration of the substance in the sodium thiosulfate standard solution, ； 0.03545——The mass of chlorine in grams equivalent to 1 mol of sodium thiosulfate standard solution. I think the value analyzed in this way is the combination of free chlorine (dissolved chlorine) and sodium hypochlorite, not the pure sodium hypochlorite content, so it cannot be used as a basis when conducting cell analysis. I hope you guys can give me some pointers. I would like to introduce the analysis method of sodium hypochlorite in the light brine from the ion membrane outlet of your company. I would be very grateful! ! # , , &
There is a reaction equilibrium constant between Cl2 and NaClO. You need to distinguish between the two. The concentration of chlorine can be calculated approximately based on its saturated solubility at different temperatures, so that the concentrations of the two can be calculated approximately.
The poster is right, what is analyzed in this way is the combination of hypochlorite and free chlorine. In fact, what is obtained is the content of available chlorine in terms of chlorine. I think it is difficult to separate free chlorine and hypochlorite using titration. However, in actual production, the content of available chlorine can be approximated to the content of hypochlorite to a certain extent. The reasons are as follows. 1. Light salt water is strongly acidic. Under acidic conditions, the solubility of chlorine in salt water is very low. 2. The temperature of light salt water is very high. At high temperatures, dissolved chlorine gas is easily volatilized. When we analyze, we require cooling to room temperature. 3. Before taking out the light salt water, there is saturated chlorine above the solution, but after sampling, there is air above the solution. Therefore, a large part of the dissolved chlorine gas will volatilize. 4. In fact, under acidic conditions, hypochlorite is also very unstable and will decompose to a certain extent. In fact, generally speaking, we only care about the content of available chlorine and not the real content of hypochlorite, because the two substances are in a state of equilibrium and have little meaning when separated. For factories, it is best to analyze the hypochlorite content in the dechlorinated brine. Or the hypochlorite content of primary brine, which is more instructive for production. As for the analysis of the hypochlorite content of the light brine from the tank, it can only be a reference.