Abstract: A mixer for preparing silver halide grains for photographic use has upper and lower impellers housed in a draft tube. The bottom impeller has flat blades for micromixing silver and halide reactants introduced into the bottom of the draft tube. The upper impeller has pitched blades for macromixing the bulk fluid. The impellers are spaced apart at least the distance of their diameters so that the upper and lower impellers operate independently of one another so that micromixing is independent of macromixing. A flow disrupter structurally associated with the draft tube and positioned above the top impeller prevents vortexing of the fluid during mixing. Baffles may be provided in the draft tube to discourage vortexing.

Abstract: A process for preparing an ultrathin high bromide {111} tabular grain silver halide emulsion in a reaction vessel comprising the steps of (a) forming in the presence of a dispersing medium a population of silver halide grain nuclei containing twin planes, and (b) growing the silver halide grain nuclei containing twin planes to form high bromide {111} tabular silver halide grains by the addition of silver and halide ions, WHEREIN the majority of the silver added during growth step (b) is added at a pBr of less than 2.6 and in the presence of a triaminopyrimidine grain growth modifier containing mutually independent 4, 5 and 6 ring position amino substituents, the 4 and 6 ring position substituents being hydroamino substituents. High bromide ultrathin {111} tabular grain emulsions prepared by the process of the invention provide thinner tabular grains than that obtained in the absence of the triaminopyrimidine grain growth modifier.

Abstract: A radiation-sensitive spectrally sensitized tabular grain emulsion is disclosed which exhibits improved speed and contrast. The tabular grains have {111} major faces, contain greater than 70 mole percent bromide and up to 10 mole percent iodide, based on silver, account for greater than 90 percent of total grain projected area, and have an average equivalent circular diameter of at least 3.5 .mu.m. The tabular grains have latent image forming chemical sensitization sites on their surfaces including epitaxially deposited silver halide protrusions of a face centered cubic rock salt crystal lattice structure forming epitaxial junctions with the tabular grains.

Abstract: The invention provides a method of measuring to control silver halide grain formation during nucleation and ripening comprisingcombining a source of silver ions and a source of halide ions to form a suspension of nucleated particles,removing a portion of said suspension,measuring turbidity of said portion,determining floc size from the turbidity measurement,determining the difference between floc size and individual silver halide nuclei size.

Abstract: Silver halide emulsions are disclosed in which at least 50 percent of total grain projected area is accounted for by tabular grains (1) bounded by {100} major faces having adjacent edge ratios of less than 10, (2) each having an aspect ratio of at least 2, and (3) internally at their nucleation site containing iodide and at least 50 mole percent chloride. The emulsions are prepared by a process comprised of the steps of (a) introducing silver and halide salts into a dispersing medium so that nucleation of the tabular grains occurs in the presence of iodide with chloride accounting for at least 50 mole percent of the halide present in the dispersing medium and the pCl of the dispersing medium being maintained in the range of from 0.5 to 3.5 and (b) following nucleation completing grain growth under conditions that maintain the {100} major faces of the tabular grains.

Abstract: Novel tabular grain emulsions and a process for their preparation are disclosed in which silver bromoiodide tabular grains account for greater than 97 percent of total grain projected area and the coefficient of variation of the total grain population is less than 25 percent. This is achieved by forming in a first reaction vessel and transporting to a second reaction vessel a population of silver bromide grain nuclei in the form of regular octahedra having an equivalent circular diameter of less than 40 nanometers and a coefficient of variation of less than 50 percent and in the second reaction vessel converting the grain nuclei into a grain population containing parallel twin planes in more than 90 percent of the grains, so that upon further growth silver bromoiodide tabular grains of desired properties can be realized.