Novel applications of dipicrylamine as an extractant in the determination of alkali metals

A ten-stage mixer-settler type extraction procedure has been used for the preparation of rubidium-free caesium salts. A nitrobenzene solution of (0.11M CsDPA flows counter to a purified aqueous solution of 0.05M CsCl and 10(-3)M Cs(4)(EDTA), which removes Rb, K, Na and most other metals from the organic phase. An extraction colorimetric titration procedure for 0.2-2 mg of caesium is described, and also an indirect method for determination of potassium and sodium in admixture, based upon the difference in the ability of the two ions to replace (137)Cs(+) in a nitrobenzene solution of dipicrylaminate.