含锂碱金属盐类混合物中锂及铷、铯、钠的连续非水络合光度滴定

Sequential Non-aqueous Complexo-Photometric Titrations of Lithium, Rubidium, Cesium, and Sodium in Mixtures Containing Lithium

本文提出一种非水络合光度滴定法,不仅可用于测定含锂碱金属盐类混合物中的锂和碱金属总量,也可用于连续测定含锂二元碱金属盐类混合物中的锂和铯(或铷,或钠),其共存摩尔比为1∶5至5∶1。探讨了滴定过程的化学反应机理。发现离子势与铜(Ⅱ)相近,与铜(Ⅱ)同属生色离子的钴(Ⅱ)、镍(Ⅱ)也可用作锂盐的光度滴定剂。

A methods have been developed for consecutive non-aqueous complexophotometric titrations of lithium and total alkali metal in alkali salt mixtures containing lithium (for binary mixture the mole ratio of lithium to another alkali metal are from ca. 1:5 to 5:1). The procedure is as follows: to one sample aliquot add ketone to dissolve lithium chloride, after filtering and washing the residue with ketone, combine filtrate and washings and transfer their aliquot into a beaker (employed as titration cell). Titrate lithium chloride with standard copper chloride ketone solution without adding indicator on a self-made photoelectric titrator at 475nm. Rubidium, Cs, Na, ammonium salts do not interfere with the determination. To another aliquot add known excess of copper chloride ketone solution, shake and wait till all are dissolved, then find the alkali salts total by backtitrating with lithium chloride Ketone solution. The relative errores not exceed ±2%. The mechanisms on the two titration reactions have been discussed. In addition, it was found that nickel and cobalt salts may be also used as photometric titrants for lithium salt.