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本文研究了酒石酸、柠檬酸、草酸及氟化铵对Ta(V)-H_2O_2-PAR三元络合物的影响。在这些辅助络合剂中,发现只有适量酒石酸才能使络合物在较宽的pH范围(4～7)内稳定存在,并有利于钽的分光光度测定。提出了在酒石酸介质中,于pH5.6,在波长530nm处,用Ta(V)-H_2O_2-PAR三元络合物分光光度测定钽的方法。在选定的条件下,用CyDTA、NTA及六偏磷酸钠作掩蔽剂,对18种阳离子的干扰进行了研究。钽在0～9微克/毫升范围内符合比尔定律。在pH5.6及波长530nm处测定,钽的三元络合物的克分子消光系数为4.1×10~4。用等克分子系列法、平衡移动法、三元相图法及电泳法测得络合物组成为[Ta(O_2)_2PAR]~-。计算得到表观稳定常数为5.9×10~5。此法用于矿石中钽的测定,操作简便易于掌握,其精确度在±7％以内。
In this paper, the effects of tartaric acid, citric acid, oxalic acid and ammonium fluoride on the ternary complex of Ta (V) -H 2 O 2 -PAR were studied. Among these auxiliary complexing agents, only tartaric acid was found to stabilize the complex over a wide range of pH (4 ~ 7) and to favor the spectrophotometric determination of tantalum. A method for the spectrophotometric determination of tantalum with Ta (V) -H 2 O 2-PAR ternary complex at pH 5.6 and at a wavelength of 530 nm in a tartaric acid medium was proposed. Under the selected conditions, interference of 18 kinds of cations was studied using CyDTA, NTA and sodium hexametaphosphate as masking agents. Beer’s law is valid for tantalum in the range of 0 to 9 μg / ml. The molar extinction coefficient of ternary complex of tantalum was 4.1 × 10 ~ 4 as measured at pH5.6 and wavelength of 530 nm. The composition of [Ta (O_2) _2PAR] ~ - was determined by the method of equimolar series, equilibrium shift, ternary phase diagram and electrophoresis. The calculated apparent stability constant is 5.9 × 10 ~ 5. This method for the determination of tantalum ore, easy to operate easy to grasp, the accuracy of ± 7% or less.