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有机试剂与金属离子之间形成络合物的反应大多数伴随有质子的释放,例如乙二胺四乙酸二钠与金属离子的反应:H_2Y~(2-)+M~(2+)(?)MY~(2-)+2H~+每形成1摩尔MY~(2-),放出2摩尔H~-。因此,测量络合反应进行到一定程度时放出的H~-浓度就知道溶液中形成了多少MY~(2-),也就知道络合物的稳定性,并可测得其稳定常数。我们在测定酸解离常数时是用标准碱溶液去滴定待测的酸溶液。如果用碱液滴定乙二胺四乙酸二钠,是把它做为弱酸来滴定。这时H_2Y~(2-)中的两个质子逐渐被中和。例如,在乙二胺四乙酸二钠与金属离子混
Most of the reactions that form complexes between organic reagents and metal ions are accompanied by the release of protons, such as the reaction of disodium ethylenediaminetetraacetate with metal ions: H 2 Y 2 + M 2 + ) MY ~ (2 -) + 2H ~ + form 1 mol of MY ~ (2-), release 2 mol H ~ -. Therefore, measuring the concentration of H ~ - released when the complexation reaction reaches a certain level, we know how much MY? (2-) is formed in the solution and the stability of the complex is known and the stability constant can be measured. When we measure the acid dissociation constant, we use a standard alkaline solution to titrate the acid solution to be measured. If using alkaline lysis disodium ethylenediaminetetraacetic acid, it is as a weak acid to titrate. At this moment, two protons in H_2Y ~ (2-) are gradually neutralized. For example, ethylenediaminetetraacetic acid disodium mixed with metal ions