铝的配合-沉淀电位滴定法
来源期刊：中南大学学报(自然科学版)1993年第1期
论文作者：李习纯 曾斌礼
文章页码：129 - 135
关键词：铝; 氟离子选择电极; 溶液平衡; 电位滴定
Key words：aluminium; fluoride ion selective electrode; solution equilibra; potentiometric titration
摘 要：本文对乙醇-水介质中氟-铝配合-沉淀电位滴定体系进行了研究。用该体系进行铝的配合-沉淀电位滴定,电位突跃明显,有确定的氟/铝计量比6:1,并有较高的选择性和准确度。在研究涉及的化学平衡中,测定了氟-铝各级配合物的稳定常数,并计算了沉淀的溶度积。在研究pH对平衡的影响中,测定了F-离子在水中及在不同浓度的乙醇介质中的加质子常数。通过标准回收及标样分析,对该体系用于氟-铝电位滴定的可行性进行了方法检验,其回收率达100±0.6%。对标准试样分析的相对误差小于1%。并进行了试样分析,与其他方法对照,结果一致。
Abstract: Aluminium can be determined by several potentiometric titration methods, such as com-pleximerric potentometric titration method using EDTA as a titrant, compleximetric poten-tiometric titration method using fluoride as a titrant. In this paper the potentiometric titration system of the complexation-precipition of aluminium with fluoride was investigated inethanol-water midium. For example, the titration curves have a well-defined end point break, the exact stoichiometry ratio between fluoride and aluminium is 6:1 under a given condition. This method has higher selectivity and accuracy. The successive stability constants for aluminium-fluride have been determined in the complexation part of the titrationcurve. The solubility product of the precipitation of Na3AlF6 was calculated in precipitationpart of the titration curve. The effects of pH on the equilibrium theoretically have been explored. The additional proton contents of fluoride ion have been determined in water and diffrental concentration ethanol medium. The values are found to be in fair agreement with literature data. The titration system has been tested by standard recovery and standard sample analysis. Recovery ratio is 100±0.6%. The relative errors for standard sample analysis were less than 1%. It has been shown that the system for aluminium-fluride potentiometrictitration is valid.
