When the AgNO₃ and KBr solutions were added simultaneously and gradually into a gelatin solution maintained at pAg 6.8, it was observed that the growth rate of small crystals was somewhat faster than that of large crystals forwarding to monodisperse precipitate. The observed dependency of growth rate on crystal dimension was interpreted by assuming the growth controlled by diffusion process. The thickness of diffusion layer around the crystals was estimated to be of the same order as the crystal dimension. Some features of the growth controlled by diffusion were refered comparing with the growth controlled by surface nucleation.

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The dyes having a strong desensitizing action show the Capri blue effect, which is an increase in blue sensitivity for surface-image formation of a chemically unsensitized emulsion at very low concentrations of dyes, although internal image is desentized. At higher concentrations of dyes, the surface sensitivity falls again as the concentration of the dye is increased. The Capri blue effect at low concentration may be caused by electron-trapping by an isolated dye molecule adsorbed physically on silver halide surface, followed by combination of the electron with silver ion. The desensitization at higher dye concentrations arises from electrontrapping by dye aggregates and the subsequent recombination of the electron with positive hole. The effect of oxygen on the Capri blue effect and the desensitization by dyes at low light intentities may be explained by the slow electron-trapping of oxygen and the acceleration of it by dyes.

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1) The photographic effects of many acetylenic compounds were reported in term of the desensitizing, antifogging and supersensitizing effects.
2) The different behaviours of acetylenic compounds in the emulsion or in the prebath from that in the developer was explained by their low rate of the adsorption on silver bromide grains and the adsorption to the gelatine layer.

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The adsorption of hydrophillic polymers on the mercury electrode by tensammetric measurement was compared with the results of turbidity measurement to silver halide grains. It was found experimentally that the results from the both measurements agree well for adsorption character. Therefore, it is considered that the turbidity measurement has close connection to the adsorption character of hydrophillic polymers on silver halide crystals.

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This paper describes an enzymatic method of producing gelatin, a method which consists principally of solubilizing the so-called insoluble collagen fibers with a proteolytic enzyme into the form of monomeric collagen molecules. A proteolytic enzyme with a broad specificity, for example, Pronase (a proteolytic enzyme from Streptoniyces griseus), very easily hydrolyzes, in the presence of CaCl₂, the specific parts of collagen fibers, in which intra- and inter-molecular crosslinks of collagen exist. Therefore, the solubilized molecules consist mainly of a-chains (a constituent polypeptide chain of a collagen molecule) in the case of calf skin and of α-and only small amounts of β-chains (two a-chains are intra-molecularly crosslinked into a β-chain) even in the case of steer hide. Gelatins, which contain only a few n-chain molecules, can be obtained after desalting and inactivating the enzyme only by the heat denaturation of the collagen molecules.
The gelatins thus prepared are of a single-chain character and have the high rigidity modulus of the gels, low intrinsic viscosities, and a narrow distribution of molecular weight.

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The powder X-ray diffraction patterns of photographic films often reveal the preferred orientations of silver halide crystals in the coated layers. The effects of various factors controlling the orientation, i. e. the shapes of silver halidecrystals, the binders, and the coating and drying methods were examined. It was concluded that the preferred orientation is caused mainly by the contraction in the direction of thickness of a coated gelatin emulsion containing flat (or generally speaking, not round) grains. Though it may seem somewhat strange, the regular cubic grains also show a strong tendency to orientation. It seems that the orientation of silver halide grains in a film is a sort of memory of some of the coating processes by which the film was made.

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