Abstract: A process for the deposition of particulate material of a desired substance on a surface includes: (i) charging a particle formation vessel with a compressed fluid; (ii) introducing into the particle formation vessel a first feed stream comprising a solvent and the desired substance dissolved therein and a second feed stream comprising the compressed fluid, wherein the desired substance is less soluble in the compressed fluid relative to its solubility in the solvent and the solvent is soluble in the compressed fluid, and wherein the first feed stream is dispersed in the compressed fluid, allowing extraction of the solvent into the compressed fluid and precipitation of particles of the desired substance; (iii) exhausting compressed fluid, solvent and the desired substance from the particle formation vessel at a rate substantially equal to the rate of addition of such components to the vessel in step (ii) through a restrictive passage to a lower pressure whereby the compressed fluid is transformed to a gaseous

Abstract: A valve assembly for dispensing a measured quantity of a gelatinous semisolid material into a receptacle comprises a cylindrical housing provided with a piston actuatable to move through the throughbore of the housing to a cap provided with a cylindrical sleeve. Mounted within the sleeve is a hollow valve body connected to a sealing member having an end of circular cross-section and a slidable hollow cylindrical body provided with an orifice whose cross-section is substantially equal to that of the end of the sealing member. The barrel is connected to the valve body by springs. In the valve closed position the end of the sealing member is situated in the barrel orifice, preventing the dispensing of the gelatinous material; in the valve open position the barrel is pushed away from the sealing member, allowing the material to be dispensed. The barrel returns to the valve closed position after the material has been dispensed.

Abstract: A method for the reproducible production of nonuniform distributions of polymolecular association clusters, each of the clusters comprising a plurality of a species A in association with a single species B, is disclosed. Species A is preferably a photographic dye and Species B is preferably a silver halide particle. The method comprises: (a) mixing a suspension of particles of species B in a vessel; (b) flowing a portion of the suspension through an isolated reaction zone; (c) introducing species A into the isolated reaction zone; and (d) returning the portion of the suspension including the introduced species A to the vessel. In another aspect, the invention relates to an apparatus for carrying out the foregoing process.