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用络合滴定法测定钙镁,其中最困难的问题是大量镁存在下测定少量钙。过去大多采用在pH≥12.5使镁生成Mg(OH)_2沉淀而滴定钙,然后凋节pH为10滴定镁或另取一份试液在pH10时滴定钙镁合量。由于有大量Mg(OH)_2沉淀生成,严重吸附钙和指示剂,使终点难以观察,致使钙的结果偏低,且镁也难以得到准确的结果。
Determination of calcium and magnesium by complexometric titration, the most difficult of which is the measurement of a small amount of calcium in the presence of large amounts of magnesium. In the past mostly used in the pH ≥ 12.5 so that Mg (OH) _2 precipitation of magnesium and titration of calcium, and then withered withal pH 10 titration of magnesium or another test solution titrated at pH10 titration of calcium and magnesium. As a large number of Mg (OH) _2 precipitate formation, severe adsorption of calcium and indicator, so difficult to observe the end point, resulting in low calcium results, and magnesium is difficult to get accurate results.