An organic analytical reagent, 4 : 7-diphenyl-1 : 10-phenanthroline (bathophenanthroline), which is specific for iron, is described for the ultra-micro spectrophotometric determination of iron. The reagent has been applied to the determination of amounts of iron ranging from 1 to 10 pg in 100 ml of water. It forms a iris type molecular complex ferrous ion whose wavelength of maximum absorption is 533 m p arid molecular extinction coefficient is 22,400. An extraction procedure for the isolation of the coloured complex from its aqueous solution increases the sensitivity and extends the specificity to the point where no known interference b:y either metal cations or common anions such as chloride, nitrate, acetate, sulphate or chlorate occurs. The method has been applied to the determination of raw and purified well water provided by municipal water supply systems. Copper does not interfere.

A new reagent for replacement of diquinoline as a specific reagent for determination of cuprous copper in the presence of iron is described. The procedure in the application of 2,9-dimethyl-1,10-phenan-

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Oxidation of Glycerol by Cerium(IV) in Sulfuric and Perchloric Acids 283 solubility of the organic compounds tried; it dissolves From these data it appears that N-methylacetamide only to the extent of about 5% by weight at 40°. is a more "universal" solvent than is water.