Abstract
The behavior of thirty triazolo [4, 5-d] pyridazines [TPD], six imidazolo [4, 5-d] pyridazines [IPD] and three benzotriazoles as an addition agent for a photographic emulsion was studied. TPDs substituted by methyl, alkoxyl and acetamino radical at 4 and 7 position exhibited a good stabilizing effect, however TPD without a substituent did not (Table 1). IPDs showed only weak stabilizing action.
The retardation of these compounds on chemical ripening (Fig. 1) and silver sulfide forming reaction between silver iodobromide and thiosulf ate ion at pH 6.0 (Fig. 2, Table 3) was connected with the stabilizing effect.
In the last experiment, silver iodobromide particles were suspended in a polyvinylalkohol solution. To this suspension, sodium thiosulf ate solution was added and this suspension were ripened for 80 min. at 55°C. In this period, each stabilizers were added and the ripening was continued for further 120min. The suspension was chilled and a developer solution was added. After a stop and fixing solution were added, the optical density was measured. As is seen in Fig. 3 and Table 4, some of TPDs retarded the ripening almost completely by presence of only ten fold moles of the amount of thiosulfate ion. On the other hand, 5-methyl-7-oxy-s-triazolo [2, 3-a] pyrimidine required twenty five fold moles of thiosulf ate ion in order to exhibit the same effect. These results coinsided with the inhibiting effect for chemical ripening with thiosulf ate in an innert gelatine medium.
In this series of the experiments, a type of compounds which exhibited an effective retardation of a chemical ripening but only weak retardation of incubation fog were found.
