Sensitization of cubo-octahedral silver bromide emulsion doped with formate

In the emulsifying process. of AgBr microcrystals in the double-jet apparatus controlled by a microcomputer, a certain amount of formate salt was injected at specific time and pAg into a reactor to prepare cubo-octahedral AgBr grain emulsions in which formate ions were doped at subsurface of AgBr microcrystals. The sensitometric results from these emulsions showed: 1) that the sensitivities (S-d) of formate-doped emulsions, relative to those (SO) of the corresponding undoped ones as the controlled, regardless of whether it is primitive, or sensitized chemically and spectrally, were remarkably increased; 2) that a cooperative sensitization by formate dopant, S+Au and dye without significant increase in fog level, was reconfirmed; 3) that the sensitivity gains (S-d/S-o) of cubo-octahedral AgBr emulsions were less than those of cubic ones.