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络合滴定中的返滴定是指在适当酸度下加入过量EDTA,加热或不加热使被测金属离子与EDTA络合完全。然后调到一定的pH值,以适当金属盐标准溶液返滴定到终点。这种滴定方式对于反应速度慢,在滴定条件下易产生沉淀,或无适当指示剂可供选择等情况的滴定体系,均有实用价值。近年来有关返滴定的报导大致有铝、镍、钼、稀土元素、钛金、钯、汞、镓、铟、铬、钒、硅、碳、锡、SO_4=[9]、铌、锆等金属离子或非金属离子的返滴定方法。返滴定中怎样选择金属盐返滴定剂,以及有关返滴定的一些平衡问题,如待测离子以及金属盐返滴定剂与EDTA形成络合物的稳定常数(lgK’MY,lgK’NY)
Back titration in complexometric titration refers to the addition of excess EDTA at an appropriate acidity, with or without heating, to complete the complexation of the metal ion under test with EDTA. Then transferred to a certain pH value, with appropriate standard solution of metal salt back titration to the end. This titration method has practical value for the titration system which is slow in reaction, easy to produce precipitation under the titration condition, or has no suitable indicator for selection. In recent years, reports on back-titration have been generally reported for metals such as aluminum, nickel, molybdenum, rare earth elements, titanium, palladium, mercury, gallium, indium, chromium, vanadium, silicon, Back titration of ionic or non-metallic ions. Back titration how to choose metal salt back titration, as well as back to the balance of some of the balance issues, such as the test ion and metal salt back titration complex with EDTA stability constants (lgK’MY, lgK’NY)