Abstract In a process for the preparation of a silver halide photographic emulsion containing a major proportion of chloride, about 0.1 mole to about 5 mole percent of iodide and up to about 10 mole percent of bromide comprising precipitating said silver halide in the presence of a hydrophilic colloid, the improvement which comprises precipitating said silver halide into a medium having a pH in the range 5-9 and a pAg of at least about 7.8 by adding to the precipitation mixture, no later than at the end of said precipitation, a weak solvent for silver halide selected from the group consisting of ammonium chloride, ammonium nitrate and magnesium chloride in a quantity in stoichiometric excess with respect to the quantity of alkali metal chloride necessary for the precipitation of the silver halide, this excess being between 4 moles and 180 moles per 100 moles of formed silver halide.
The process of claim 1 wherein the silver chloroiodide or silver chlorobromoiodide emulsion contains a proportion of iodide between about 0.003 and 0.03 mole per mole of silver chloroiodide or silver chlorobromoiodide.
Claim 2
Dependent Claim
27 words
The process of claim 1 wherein the ammonium chloride, ammonium nitrate or magnesium chloride is added to the precipitation vessel before the beginning of the precipitation reaction.
Claim 3
Dependent Claim
28 words
The process of claim 1 wherein between about 45 moles and 95 moles of ammonium chloride is employed for every 100 moles of the final silver halide product.
Claim 4
Dependent Claim
113 words
In a process for the preparation of a silver chloroiodide or chlorobromoiodide photographic emulsion containing a major proportion of chloride, about 0.1 mole to about 5 mole percent of iodide and up to about 10 mole percent of bromide comprising precipitating said silver chloroiodide or chlorobromoiodide in the presence of a hydrophilic colloid, the improvement which comprises precipitating said silver chloroiodide or chlorobromoiodide into a medium having a pH in the range 8-9 and a pAg of at least about 7.8 by adding between 45 moles and 95 moles of ammonium chloride for every 100 moles of the final silver halide product to the precipitation vessel before the beginning of the precipitation operation.