METHOD OF PREPARING SILVER BROMIDE/IODIDE PHOTOGRAPHIC EMULSIONS Russian patent published in 1997 - IPC

FIELD: chemical photographic industry. SUBSTANCE: silver bromide/iodide photographic emulsions are prepared by way of controlled two-jet emulsification using simultaneous introduction into ammonia-containing water-gelatin solution No.1 of (i) aqueous solution No.2 containing potassium bromide and iodide with 1-7 mol.% of iodide based on total halide content and (ii) silver nitrate aqueous solution No.3 in amount 30-90% based on total volume of solution No.3, whereas remaining volume of solution No.3 is introduced simultaneously with potassium bromide solution No.4. Distinguishing feature of invention is that, when first 50-80% of solution No.3 based on its total volume is being added to solution No.1, solutions No.3 and 2 or No.4 are introduced with constant rate at constant pBr value equal to 3.3-3.7, whereupon pBr is reduced by 0.3-0.5 and maintained constant until simultaneous addition of solutions No.3 and 4 with the same volume rate is completed. EFFECT: optimized parameters of procedure. 2 tbl