A technique which eliminates effects of changes in asymmetry potential has been adapted for use in pH titrations with high-resistance glass electrodes. A study, using cells without liquid junctions, has been made of the hydrolysis of the oxovanadium( iv) ion and of its complexes with the ' I ,2-dihydroxybenzenato(2-) ion. Equilibrium constants University, Whiteknights, Reading RG6 2AD are reported.THE oxovanadium(1v) ion, V02+, forms stable complexes with the 1,2-dihydroxybenzenat0(2 -) ion in aqueous solutions, but the results of earlier quantitative studies of the stabilities, and even the identities, of these complexes are discrepant and unsatisfactory. Potentiometric studies 1-3 were made on cells with liquid junctions and with uncertain control of ionic activity coefficients. Furthermore, the effects of hydrolysis of the oxovanadium(rv) ion or the formation of complexes with sulphate or chloride ions were ignored or inadequately considered. Spectrophotometric measurements lead to stabilityconstant values which disagree with those reported from potentiometric measurements.In the present study precise potentiometric measurements have been made on cells with glass and silversilver chloride electrodes which avoid liquid junctions. A careful examination of the hydrolysis of the oxovanadium(1v) ion was necessary before the investigation of the complexes. The only satisfactory previous study 5 of this hydrolysis relates to measurements in S~-sodium

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It is the purpose of this paper to clarify the relationship of equations relating stability constants to parameters such as the size of ions and the dielectric constant of solvents to one another and to the different models from which they derive.

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Volumen xxxm, Fasciculus IV (1950) 129-130. 985 Z us a mm en f a s sung. Es wurden die Gleichgewichte bei der Komplexbildung mit &B '-Diamino-N, N'-diiithyl-athylendiamin (= ,,trien") A. Die B a s i z i t i i t s k o n s t a n t e n von ,,den". Die Basizitiitskonstanten von ,,den" fur die ionalen StLken p = 0,l und p = 0,5 sind in Tabelle 1 registriert. Diejenigen in 0,5-n. Losung werden wir fur die Auswertung der bei Gegenwart von Quecksilber( 11)-Ion aufgenommenen Kurven benotigen. l) Fur die Uberlassung des Praparates mochten wir der CIBA Aktiengesellschuft bestens danken.-No.