The Mechanism of Emulsion Stabilization by 5-methyl-7-hydroxy-l, 3, 5-triazaindolizine.^*

* We wish to record, that Dr. Graziella Cibrario, who was responsible for many of the measurements described in this paper, was involved in a fatal accident before the work was completed.

Abstract

The inefficiency of 5-methyl-7-hydroxy-1, 3, 4-triazaindolizine (Aza) os an antifoggant in a developer is caused by the desorption of Aza from the development centres by developing agents and bromide and is also influenced by the sulphite concentration and the pH of the bath. Nitrobenzimidazole (Nitro) is not desorbed completely under the same conditions. The adsorption on the specks measured with C¹⁴-labelled Aza, Nitro and benzimidazole, is not only influenced by the solubility product of the silver salts but also by other factors such as gelatin concentration and by the value of the acid dissociation constant. So with increasing pH the adsorption of Aza on the active centres diminishes and the adsorption of Nitro increases. In addition the Aza is in competition with the gelatin for the adsorption on the grains. The adsorption of Aza on the grains reduces the amount of adsorbed gelatin and this may cause the increase in sensitivity by Aza. Our results indicate on adsorption of hydroquinone on the active centres. The distribution of Aza between the gelatin phase of the emulsion, the gelatin layer adsorbed on the grains and the surface of the grains has been studied. The increase in the concentration of Aza in the gelatin layer adsorbed on the grains results in an increased formation of photographically inactive specks in this layer.

Notes

* We wish to record, that Dr. Graziella Cibrario, who was responsible for many of the measurements described in this paper, was involved in a fatal accident before the work was completed.