Abstract: In the emulsifying process of silver bromide microcrystals in the double-jet apparatus controlled by a microcomputer, a specific quantity of formate was added at different time when the crystal growth to obtain a series of cubic AgBr emulsions in which formate ions were doped into different depths of AgBr microcrystals. The results from measurements of photographic properties of these emulsions showed:1) that the sensitivities of formate-doped emulsions, relative to that of the undoped emulsion as the controlled one, were remarkably increased;2) that the closer to the surface of grains the formate doped in AgBr grains was, the greater the sensitivities of the doped emulsions were;3) that a significant cooperative sensitization of the internal doped formate with the surface sulfur-plus-gold and dye sensitizations was observed;4) that the maximal sensitivity gain (S_max/S₀) of undye-sensitized emulsions was greater than those of dye-sensitized ones;5) that fog densities of all emulsions doped by formate, including those primitive, sensitized by sulfur-plus-gold and by green-sensitive dye, were kept in a reasonably low level.

Key words: chemical sensitization, formate doping, silver halide emulsion