The fog formation by dyes has been discussed from quantum-chemical viewpoints, and suggested to arise from the electron transfer from the dyes in the ground state to silver halide grains. Based on this mechanism, factors influencing the fog formation have been suggested. An application of the superdelocalizability (Sγ) for the estimation of the degree of fog formation by dyes is proposed. The relations of the fog formation by dyes with the Ag⁺ complex formations and with the basicities of the dyes have been discussed in relation to the Sγ of the dyes. Sγ of cyanine dyes was calculated by use of the HMO method. It has been found that with larger Sγ for dyes, there is larger fog formation, and that Sγ of dyes is, therefore, useful for the estimation of the degree of fog formation by dyes. These results support the adequacy of the mechanism of fog formation by dyes in this work.

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The stability of a negative and a positive silver iodide sols, in the presence of of gelatin, was measured at various pH's and ionic strengths by the method of Ottewill and Watanabe, and from the stability curves obtained, the flocculating action of gelatin on the silver iodide sols was discussed. Four samples of gelatin obtained by fractionating a lime-processed gelatin were used in the flocculation experiments. In general, the sol stability increases slowly or remains constant with an increase in gelatin concentration up to a certain concentration, and then decreases rapidly. After reaching a minimum value, which suggests the flocculating ability of the gelatin at a given condition, the stability rapidly increases again. A remarkable stability minimum is observed for the negative silver iodide sol at a pH lower than the isoelectric point of gelatin, or for the positive silver iodide sol at a pH higher than the isoelectric point.

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For the purpose of contributing to the basic study of photochemical process, photochemical reaction of Cr (VI) oxysalts such as dichromate and chromate compound with reducing agents, polyvinyl alcohol and several alkyl alcohols in the aqueous solution was investigated.
In the dilute aqueous solution of these Cr (VI) oxysalts, the photoactive species is acid chromate ion, HCrO₄^- and chromate ion, CrO₄^2-, has no photosensitivity. The two charge transfer bands of acid chromate ion;λ_max 350 and 440 mμ, give rise to the photoreduction reaction of Cr (VI) to Cr (III). The quantum yields of reduction of Cr (VI) to Cr (III) at 365 m, eC are smaller than 0.5 in these experimental conditions.
It is confirmed by spectrophotometry that the photoreduction products of Cr (VI) is Cr (III) complex ion in in the aqueous solution. During the photoreduction of Cr (VI) the reducing agents are oxidized and 3 mol of oxidized form of reducing agent is produced for 2 mol of Cr (VI).
By spectrometric and electron spin resonance method at -196°C, it is observed that during the photoreduction process of Cr (VI) to Cr (III), it exists an intermediate valence state of chromium (Cr (V) or Cr (IV)).

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The reaction of reactive couplers with polymers is often accompanied with the hydrolysis of the coupler. This has led us to the study of the alkaline hydrolysis of typical reactive couplers carrying the dichlorotriazinyl group. About 26% of chlorine was replaced by hydroxyl in aqueous sodium carbonate, while 50% of chlorine was replaced in aqueous sodium hydroxide. The reaction is first order in coupler. The rate constants differ from each other to a small extent, which is explained in terms of the electronic effects induced by the substituents adjacent to the triazinyl nucleus.

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This paper discusses the reaction of typical reactive couplers carrying the dichlorotriazinyl group with polyvinylalcohol. The replacement of second chlorine atom was enhanced by the presence of polymer, and the conversion ratio went up to 60%. From the comparison of the reaction ratio, it became evident that the hydrolysis of coupler was depressed by the presence of polymer, the reaction of coupler with polymer proceeded predominantly, and 60 to 85% of coupler reacted with polymer. The optimum conditions for the reaction with polymer exist in the range of 30° to 40°C.

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For the purpose of measuring the sharpness of a radiographic image, we have recently manufactured a metallic test chart consisting of lead and aluminum foils.
As a result of testing of this chart, it was found that this chart gave a very large contrast, being as large as 0.9 compared to the value of about 0.5 for conventional test chart of evaporation-type. It was also confirmed that the incident angle characteristic for an oblique incident radiation of this new test chart was superior to that of the conventional evaporation-type test chart. Further, using this newly-made test chart, the image quality for several kinds of the X-ray films was evaluated.
From the results obtained we were able to find quantitatively how the MTF, that is, an evaluating measure of sharpness would be affected when the thickness of film base, the γ-value of film, the velocity of developing treatment, the granularity, etc., were changed.

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