The sample is acidified in a closed container and heated and distilled to release the sulfur dioxide in it, and the release is absorbed with water. After absorption, the iodine standard solution was titrated, and the sulfur dioxide content in the sample was calculated according to the amount of iodine standard solution consumed.
2 Reagents. 2.1 phosphoric acid (1+3).
2.2 Iodine standard solution [c(1 2i2) = 0.]010mol l]: Iodine standard solution (0100mol l) dilute 10 times with water.
2.3 Starch indicator solution (10g L): Weigh 1g of soluble starch, mix it into a paste with a little water, slowly pour it into 100ml of boiling water, stir with addition, boil for 2min, let it cool, set aside, this solution should be newly prepared when it is used.
Install the condensing device, the condenser tube should be inserted into the absorbent solution containing 100ml of freshly boiled cold water (add 1ml of starch indicator (10g l) pre-iodized standard solution to light blue), add 200ml of freshly boiled cold water to the sample, and place it in a 1000ml round-bottom distillation flask, then add 10ml (1+3) phosphoric acid to the round-bottom distillation flask, immediately cover and plug, and heat the distillation. When the blue color of the receiving liquid recedes, start titration with iodine standard solution until it is blue and does not fade within 30 seconds, cut off the power supply, rinse the part of the device inserted into the receiving with a small amount of distilled water, if the blue fades, continue to titrate until it is blue and does not fade within 30 seconds, and do a blank test at the same time as the test sample.