原理:乙二胺四醋酸二钠为钙、镁的试药,和钙、镁离子生成稳定的络合物。在检水pH=10时,以зри-охромчерный(Eriochromic black)为指示剂,用乙二胺四醋酸二钠可直接测定水的硬度。指示剂эриохромч-ерный和镁离子生成玫瑰红色络合物。用二二胺四醋酸二钠滴定时,先和钙离子结合,然后再和镁离子生成稳定的络合物。当钙、镁所有阳离子和乙二胺四酷酸二钠完全生成络化物后,溶液颜色由玫瑰红色变为淡蓝色。 Principle: Disodium ethylenediaminetetraacetate is calcium and magnesium reagent, and calcium and magnesium ions generate stable complexes. The hardness of water can be determined directly with disodium ethylenediaminetetraacetate (pH = 10) using зри-охромчерный (Eriochromic black) as indicator. The indicator эриохромч-ерный and magnesium ions generate a rose-red complex. With diamine four disodium titration, the first combination of calcium and magnesium ions and then generate a stable complex. When all of the calcium and magnesium cations and disodium ethylenediaminetetracarbohydrate completely form the complex, the color of the solution changes from rose red to light blue.