云南磷矿石中氧化钙含量测定方法的改进

用国标EDTA容量法检测磷矿石中氧化钙含量时,存在终点难以判定等问题,实验研究改用钙羧酸作指示剂,用三乙醇胺掩蔽铁、铝和少量锰,用糊精作保护剂抑制磷酸根和镁的干扰,同时采用KOH溶液调节试样溶液的pH值≥13,用EDTA标准溶液滴定,终点颜色变化敏锐,测定氧化钙的结果准确,方法可靠。

Improvement of determination for calcium oxide content in Yunnan phosphate rock

With the calconcarboxylic acid as indicator triethanolamine for masking iron, aluminum and a small amount of manganese, dextrin as protective agent for inhibiting the interference of phosphate and magnesium, and KOH solution adjusting the pH of sample solution for pH 913, and EDTA standard solution titrating, thus the color change of titration end point is acute, the determination result of calcium oxide content in phosphate rock is accurate, reliable in operation. However the original national standard EDTA volumetry makes the determination of calcium oxide content difficult in dull titration end point.