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Color reactions are popular criteria for the identification and quantitative determination of substances. For alkaline-earth metal ions, dye reagents and color indicators are available that allow titrimetric determination of the ionic content with chelating agents of the EDTA type.1 For alkali metal ions however, only a few color reagents were known before 1977,2 and these do not allow the photometric ion determination of practical samples. New possibilities were opened by the discovery3 and development of the crown ether chemistry.4 The selectivity of non-, moño-, and bicyclic oligoethers to alkaliand alkaline-earth metal ions has

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Research Council of Canada. We thank Dr. M. Békhazi, whose initial work with the oxadiazoline system indicated that neat samples led to a greater variety of products than did dilute samples.