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Original Articles

Breakdown of Sodium Thiosulphate on Silver Halide Grains, Studied by Electron Microscopy

Pages 53-59 | Received 12 May 1976, Published online: 22 Jul 2016
 

Abstract

The breakdown of the thiosulphate, adsorbed on the grains of a photographic emulsion after treatment with diluted sodium thiosulphate solutions, is studied by electron microscopy of the extraction replicas of the treated grains.

Deposits of monoclinic Ag2S are produced at the surface of the grains during the breakdown, being identified by selected area diffraction. They appear as thin layers in different steps of their growth, and as three dimensional specks.

The reaction is found to depend on the initial concentration of the thiosulphate and on the temperature of the process, which have been varied within certain limits.

The most important deposits of Ag2S are produced for the 10-4 M/l thiosulphate concentration at the three temperatures employed. Also, an increase of the Ag2S deposits is evident as the temperature increases.

Résumé

La dismutation du thiosulfate, adsorbé sur les grains d’une émulsion photographique à la suite d’un traitement avec des dissolutions diluées de thiosulfate de sodium, a été étudiée par la microscopie électronique de répliques-transfert des grains traités.

Pendant la dismutation, des dépôts de Ag2S monoclinique son produits à la surface des grains, identifiés par diffraction d’aire sélectionnée. Ils apparaissent sous la forme de couches minces à plusieurs moments de leur croissance, et aussi comme amas à trois dimensions.

On trouve que la réaction depend de la concentration initiale de thiosulfate et aussi de la température du processus, ayant fait varier toutes les deux entre certaines limites.

Les plus importants dépôts de Ag2S se sont produits pour la concentration KF4 M/l du thiosulfate aux trois températures employées. Une augmentation des dépôts de Ag2S est mise en évidence aussi, quand la température monte.

Zusammenfassung

Die Umsetzung des nach Behandlung mit verdünnter Thiosulfatlösung an der Oberfläche photographischer Emulsionskristalle adsorbierten Thiosulfates zu Silbersulfid wird elektronenmikroskopisch (Gelatinehüllen) untersucht. Bei der Umsetzung werden an der Kornoberfläche Niederschläge von monoklinem Ag2S erzeugt, die durch Feinbereichsbeugung identifiziert werden können. Die Niederschläge treten als dünne Schichten in unterschiedlichen Wachstunisphasen oder auch als dreidimensionale Teilchen auf. Die Umsetzungsreaktion hängt von der Anfangskonzentration des Thiosulfates und von der Temperatur ab, die innerhalb gewisser Grenzen variiert wurde.

Riassunto

E’ stata studiata la decomposizione del tiosolfato adsorbito sui granuli di una emulsione fotografica, dopo trattamento con soluzioni diluite di tiosolfato, operando per microscopia elettronica su repliche di estratti dei granuli cosi trattati.

Nel corso della decomposizione si formano sulla superficie dei granuli, dei depositi di Ag2S monoclini identificati mediante diffrazione selettiva zonale.

Il loro aspetto è duplice: strati sottili nei diversi stadi di crescita e nuclei tridimensionali.

Si è trovato che la reazione è dipendente dalla concentrazione iniziale di tiosolfato e dalla temperatura del processo che sono state variate entro certi limiti.

Ai tre livelli di temperatura esplorati i depositi più importanti di Ag2S si formano per concentrazioni di tiosolfato 10-4 M/l.

Inoltre si osserva un aumento dei depositi di Ag2S come cresce la temperatura.

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