The zirconium-precipitating action of mandelic acid is also shown by other glycolic acid derivatives. By use of appropriate derivatives, larger volumes of precipitate per unit weight of zirconium can be obtained than with mandelic acid. p-Chloromandelic acid and p-bromomandelic acid were successfully applied to the determination of zirconium in commercial zirconyl chloride, an iron-zirconium-aluminum alloy, and a silicate ore. Sulfuric acid up to 5% by weight does not prevent quantitative precipitation. The possibility of determining zirconium by direct weighing of the mandelate precipitates was investigated. The preferable reagent for the determination of zirconium by the mandelate method was found to be p-bromomandelic acid, then p-chloromandelic acid, and finally mandelic acid. THE methods available for the gravimetric determination of zirconium are not satisfactory. They employ reagents which are lacking in selectivity or involve difficult and tedious procedures (10).

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The ionization constants of thirteen mandelic acid derivatives were measured in aqueous solution at 25°C. using the potentiometric method described by Albert and Serjeant, DaTA on the ionization constants of mandelic acid derivatives are limited. Besides mandelic acid (11), values appear to be available only for the m-halo (5, 11), o-, m-, and p-nitro (6), and p-bromo (2) mandelic acids. The ionization constants of additional mandelic acid derivatives have now been obtained.

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