their oxides and, hence, to volatile chelates of the form ZrO& (where X is the residue of a fluorinated diketone). It is possible to determine such chelates using the same method and, hence, to estimate zirconium and hafnium in aqueous solution. Work is proceeding upon the determination of zirconium and hafnium in alloys and ores by this procedure.
ACKNOWLEDGMENTThe authors are indebted to M. J. A. Reade for assistance in spectrometry. (1)(2)(3)(4)(5)(6). This effect was first noticed with the ferrous ion ( I ) , and since this complex of a given compound is generally of a more intense color than are those with other ions (7), the atomic configuration in question was given the trivial name of the ferroin group. During the last century, hundreds of compounds containing the ferroin group have been synthesized (7), the majority of which demonstrate the ability to form complexes with the ferrous ion. Most of these complexes are only weakly
RECEIVED
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