Scalable impeller apparatus for preparing silver halide grains

A scalable apparatus for preparing a predetermined volume of silver halide emulsion in a containment vessel, comprising:

• a vertically oriented draft tube arranged in said containment vessel,
• a bottom impeller positioned in said draft tube for dissipating power into said silver halide emulsion;
• a top impeller positioned in said draft tube above said bottom impeller for producing a pumping rate of said silver halide emulsion, the top impeller being arranged in a spaced relations in said draft tube from the bottom impeller by a distance sufficient for independent operation of said bottom impeller and said top impeller, said bottom impeller having a power dissipation P defined by the equation
• P=ρNpn3D5,
• wherein ρ is density of the mixture,
• Np is the power number,
• n is mixing speed, and
• D is the diameter of the lower impeller;
• and wherein said top impeller has a pumping rate Q defined by the equation
• Q=NqnD3,
• where Nq is the flow number,
• n is mixing speed, and
• D is the diameter of the upper impeller;
• and, wherein scaling from a first volume V1 of silver halide emulsion to a second volume V2 of silver halide emulsion by a scaling factor S=V2/V1 is achieved by changing D according to the equation
• D2=D1S⅓
• wherein D2 is the diameter of said top impeller and said bottom impeller appropriate for said second volume V2 of silver halide emulsion, and wherein D1 is the diameter of said top impeller and said bottom impeller appropriate for said first volume V1 of silver halide emulsion.