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Original Articles

The Autoxidation of Developing Agents at High pH

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Pages 17-18 | Received 08 Sep 1976, Published online: 22 Jul 2016
 

Abstract

The rates of autoxidation of l-phenyl-3-pyrazolidone, 4,4-dimethyl-l-phenyl-3-pyrazoIidone, N-methyl-p- aminophenol and hydroquinone increase, with increasing pH, to maximum values in the pH range 10-11.5. Thereafter the rates fall as the pH rises. The reversal of the trend can be associated with the fall in the redox potential of oxygen-water systems with increasing pH.

resume

Les vitesses d’auto-oxydation de la l-phényIe-3-pyrazolidone, de la 4,4-diméthyl-l-phényl-3-pyrazoIidone, du N-méthyl-p- aminophénol et de l’hydroquinone augmentent avec le pH et passent par un maximum entre pH 10 et 11, 5. Au-delà de ces valeurs, les vitesses diminuent lorsque le pH augmente.

Ce renversement de comportement peut être associé à la décroissance du potentiel redox des systèmes oxygène-eau lorsque le pH augmente.

Zusammenfassung

Die Geschwindigkeiten der Auto-Oxidation von l-phenyl-3-pyrazolidon, 4,4-dimethyl-l-phenyI-3-pyrazoIidon, N-methyl-p-aminophenol und Hydrochinon steigen mit ansteigendem pH-Wert bis zu Maximalwerten im pH-Bereich 10 bis 11, 5 an. Bei weiter steigendem pH-Wert nehmen die Geschwindigkeiten wieder ab. Diese Umkehr kann auf den Abfall des Redoxpotentials des SauerstoffWasser-Systems mit steigendem pH-Wert zurückgefürt werden.

Riassunto

La velocità di autoossidazione dell’l fenil-3-pirazolidone, del 4-4 dimetil-l-fenil-3-pirazolidone, del-l’ N-metil-p-aminofenolo e dell’idrochinone aumenta col crescere del pH fino a raggiungere un valore massimo intorno a pH 10-11,5. Superato questo valore la velocità diminuisce. L’inversione di tendenza può essere associata con la caduta del potenziale redox presente nei siste mi ossigeno-acqua col crescere del pH.

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