A comparison of the existing stability data for the reaction of a given chelating agent with a series of metal ions 2~3 shows that the stability order for a given reagent is much the same from reagent to reagent, although the individual metal chelate stabilities vary widely. The question of whether this general stability order is characteristic of all reagents is of considerable importance in determining the factors which confer selectivity or specificity upon a reagent. One of the most specific of all organic analytical reagents is dimethylglyoxime, which, under ordinary conditions, forms water-insoluble precipitates only with nickel (II) and palladium (II) ions. It was therefore thought desirable to investigate the stabilities of the chelates of this reagent by means of the Calvin-Bjerrum titration technique, in order to learn whether the famed specificity of this reagent for nickel is due to an unusually great stability of the nickel complex, relative to the stabilities of the other metal dimethylglyoxime complexes, or whether some other factor is involved.
Stability measurements were also extended to the chelates of the 0-monomethyl ether of dimethylglyoxime.
This compound is of particular interest since the structure of the nickel salt of dimethylglyoxime is known to involve hydrogen bondingd*S, while no such hydrogen bonding is possible with the O-ether complexes. EXPERIMENTAL Materials. Baker and Adamson Reagent Grade dimethylglyoxime was recrystallized twice from ethanol-water mixtures and was dried in a vacuum desiccator. * For paper IV see reference (I). +* Abstracted from the thesis submitted by ROBERT G. CHARLES in partial fulfillment of the requirements for the Ph.D. degree in chemistry, August 1952.