Determination of dissolved oxygen in water

1、 The amount of dissolved oxygen in water is a very important factor It is related to the success or failure of breeding 2、 Determination principle: the amount of dissolved oxygen in water is determined by Iodimetry (Winkler) When MnSO4 solution and Ki NaOH solution are added to the water, the dissolved oxygen in the water is quantitatively converted into brown precipitate of trivalent manganese compounds Mn + 2OH - ===== Mn (OH) 2 Mn (OH) 2 + O2 = 2mno (OH) 2 2mno (OH) 2 + 2I - + 6h + ===== 2mn2 + + I2 + 6h2o2na2s22o3 + I2 = na2s4o6 + 2nai with starch as indicator, titrate the I2 generated by the above reaction with Na2S2O3 standard, and calculate the dissolved oxygen content in the effluent 3、 Reagent: KIO3 = 0.0100/6mol/l Na2S2O3 0.01mol/l starch solution MnSO4 solution ki --- Kaoh solution H2SO4 solution ki solution IV determination: KIO3 20.00ml, add 3ml ki solution and 2ml H2SO4 solution, add 50ml water, titrate to light yellow with Na2S2O3 standard solution, add 1ml starch solution, titrate to no color KIO3 + 5ki + 3h2so4 = 3K2SO4 + 3i2 + 3h2o2na2s2o3 + I2 = na2s4o6 + 2nai 1:6 reaction 5 Water sample determination: a bottle of water sample (about 50ml) is known as volume V1, 1ml of MnSO4 solution and 1ml of Ki NaOH solution are added, the bottle is covered (without air), uniform, and precipitated at the bottom Add 41ml of H2SO4, precipitate and dissolve, pour all the liquid into the iodine measuring bottle, calibrate it to scorching yellow with nas2o3, add 1ml of starch, drop it to colorless, pour a small amount of solution back to the sample bottle, pour back to the iodine measuring bottle, and then drop it to colorless to obtain volume v 6、 Do (mg / L) = = = = = = (8.000 * 1000cv) / V1-2 C is the concentration of nas2o3 (mol / L)