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本工作制定了用离子选择电极电位滴定法连续测定瓷土中钙镁含量的分析方法。以硫化银电极为指示电极,EGTA—Ag 为液体指示剂,不须另取试液可用 EGTA和 CyDTA 连续滴定钙和镁。在 pH=9.5—10.0,在25ml 的一份试液中加入5毫克分子酒石酸钾钠,可隐蔽 Fe~(3+)、Al~(3+)、Ti~(4+)等干扰离子。EGTA、CyDTA 的浓度分别是1×10~(-3)M、5×10~(-3)M。实验发现:CyDTA 同钙(镁)的反应速度快于 EDTA同钙(镁)的反应速度,且在 CyDTA 滴定曲线上的电位突跃范围比在 EDTA 滴定曲线上的电位突跃范围宽。当钙(镁)氧化物的含量由0.1—3%时,可以测定得到准确的结果。
This work developed a method for the continuous determination of calcium and magnesium in porcelain clay by ion-selective electrode potentiometric titration. With silver sulfide electrode as the indicator electrode, EGTA-Ag as a liquid indicator, without another test solution EGTA and CyDTA continuous titration of calcium and magnesium. At pH = 9.5-10.0, adding 5 mg of potassium sodium tartrate to 25 ml of a test solution can conceal interference ions such as Fe 3+, Al 3+ and Ti 4+. The concentrations of EGTA and CyDTA are 1 × 10 -3 M and 5 × 10 -3 M, respectively. It was found that the reaction rate of CyDTA with calcium (magnesium) was faster than that of EDTA with calcium (magnesium), and the range of potential jump in CyDTA titration curve was wider than the potential jump in EDTA titration curve. When the content of calcium (magnesium) oxide is from 0.1 to 3%, accurate results can be measured.