EDTA络合滴定法快速测定矿石中钙、镁

试样用盐酸、硝酸、氢氟酸、高氯酸分解,在pH值为6～9时,经六次甲基四胺-铜试剂分离铁、铝、镍、钴、铅、锌、铜、镉、锰等干扰元素后,在pH=10的氨水和氯化铵缓冲溶液中,以酸性铬蓝K-萘酚绿B为指示剂,用EDTA络合滴定法测定钙镁合量;另在氢氧化钾溶液中,用钙试剂为指示剂,以EDTA络合滴定法测定钙量,从而计算镁的含量。当样品钙高镁低或者镁高钙低时,低含量的镁量或钙量(<5%)可用电感耦合等离子体原子发射光谱(ICP-AES)法准确测定,使结果更准确。实验中对三个标准样品中的钙和镁进行多次测定,结果与认定值相符,相对标准偏差在0.69%～1.3%(n=7),加标回收率在99%～102%。方法实用性强,已经成功应用于各类矿石中钙镁的检测。

Rapid Determination of Calcium and Magnesium in Ore by EDTA Complexometric Titration

SThe sample was decomposed by hydrochloric acid, nitric acid, hydrofluoric acid and perchloric acid, and at pH 6-9, Fe, Al, Cr, Ti, Ag, Hg, Bi, Ni, Co, Pb, Zn, Cu, Cd and Mn were separated by hexamethylenetetramine-copper reagent, followed by acid chromium blue K-naphthol green B in ammonia solution of pH=10 and ammonium chloride buffer solution of ammonia chloride. Calcium and magnesium were determined by EDTA complexometric titration as indicator and calcium was determined by EDTA complexometric titration in potassium hydroxide solution with calcium reagent as indicator. The content of magnesium or calcium (< 5%) with low content can be accurately determined by ICP-AES when the sample is high in calcium and low in magnesium and high in calcium. Calcium and magnesium in three standard samples were determined by this method. The results were in agreement with the certified values. The relative standard deviation was between 0.85% and 1.25% (n=7), and the recovery was between 98% and 101%. This method is practical and has been successfully applied to the determination of calcium and magnesium in various ores.