GB1515139A - Method and apparatus for making silver halide photographic emulsion - Google Patents

Abstract

1515139 Silver halide emulsions FUJI PHOTO FILM CO Ltd 9 Dec 1975 [9 Dec 1974] 50487/75 Heading G2C [Also in Division B1] A method of making a photographic silver halide emulsion comprises separately introducing aqueous halide and silver salt solutions with the upper end of a mixing chamber immersed in aqueous peptizing agent solution, agitating them by first agitating means, and expelling the resulting silver halide grains from the lower end of the chamber by second agitating means. In an apparatus the silver salt and halide solutions are delivered through conduits 4, 4' to the top of chamber 3 wherein is rotatable first agitator 11 in a mixing zone 10A formed between baffles 10, 10'; the silver halide grains are expelled downwardly into the body of peptizing agent by a second agitator 12. The agitators 11, 12 may be mounted on the same shaft or on coaxial shafts rotated at different speeds. The mixing chamber may be of circular cross-section as shown, or (preferably) of square or other polygonal crosssection. The circulation rate may be altered by varying the size of the opening 14 or by having exchangeable chamber tops with openings of different sizes. The baffles 10, 10' may consist of rectangular plates partially cut transversely with the cut portions bent in opposite directions through angles of preferably 45 degrees to 60 degrees (see Fig. 8, not shown). The agitator blades 11, 12 may be replaceable. Valves (see Fig. 11, not shown) may be provided with the conduits 4, 4' immediately upstream of their outlets to prevent back flow. In modifications the baffles 10, 10' may be omitted and the first agitating means provided by two oppositely coupled blades (16, 16') Figs. 9 and 10, (not shown); and the second agitation (17) Fig. 12 (not shown) may be below the mixing chamber and of greater diameter. Comparative examples are given disclosing smaller and more uniform grain size.