The diazo type process, which is an useful reproducing method, is based on the sensitivity of certain diazo compounds to light. These materials (diazo nium salt etc.) are decomposed by particular light (blue light or ultra-violet rays) absorption, but unexposed diazo compounds produce azo dye with coupler (ex. phenol), in high pH condition and form positive images.
Diazo papers, in present use, are classified by developing or coupling process, one of them, uses solution developer, called moisture type, and another type uses ammonia vapor. Typical diazo papers have, coloring density of 1.0-1.2, sensitivity region of 3000-4500 Å, and printing speed of about 190 m/h for typical copying machines.
Recently, new type diazo papers have been appeared. There are high speed papers, which have three times or more speed than former papers, and heat developing type papers.
Special papers, for reflex printing, making offset masters, using microfilm duplication, also have made for each requirements.

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Tne adsorption of thiourea on silver bromide grains were investigated at pH 5, 7 and 11 by means of iodine-azid and iodine titration analysis. Initial part of adsorption curve at pH 5 showed a typical monolayer-type saturated curve. However the successional increase of thiourea concentration resulted in the newly increase of thiourea adsorbed. The similar adsorption curve was obtained at pH 7, but the point at which the adsorption curve again begun to stand was at lower concentration than the curve at pH 5. At pH 11 the adsorption was monotonously increased with the increase of thiourea concentration without showing monolayer-type adsorption curve. The appropriate formulas of iodine-azide and iodine solutions to be used for the analysis of thiourea were indicated. Finally it was suggested that the phenomena on the adsorption of thiourea on silver bromide might be used for the estimation of size of silver bromide grains.

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Transfered amount of ions or compounds to colloidal particle surfaces from liquid phase in colloidal solution is able to be estimated by using electrophoretic measurement of the colloidal particles. The authors planned to apply the method to the work on adsorption of photographic addition agents, most of which are sulfur-bearing compounds, on silver bromide grains, and prior to the work it was needed to know electrophoretic behaviour of sulfur-content silver bromide grains. Sulfur-content silver bromide sol was prepared by adding sodium sulfide to silver bromide sol of pH 5.5, and the elecrophoretic behaviour of this sol, especially dependence of the electrophoretic mobility on pAg and sulfur-content of the sol, were investigated. Results indicated that electrophoretic mobility and its pAg dependence of low-sulfur-content silver bromide sol were nearly the same as those of silver bromide sol. However, the electrophoretic mobility of sulfurcontent silver bromide sol was decreased with the increase of sulfur-content. It was considered that this phenomenon was due to the change of pH and pAg of the sol with the addition of sodium sulfide into silver bromide sol. It was indicated clearly that when sodium sulfide was added into silver bromide sol the pH and pAg change. The shape of curve showing the relation was step-like, and such a curve has been often experienced by analysts for determination of acid-base titration etc. Discussion and analysis of the curves led to the conclusion that as sodium sulfide was added into the silver bromide, sulfide ions firstly reacted with silver ions in the liquid phase rather than those in silver bromide grains, and after the completion of the above reaction it reacted with silver ions of the latter. In the latter reaction, sulfide ions diffuse from the surface into the interior of a silver bromide grain, forming silver sulfide, and during the process bromide ions diffuse from interior of a silver bromide grain to liquid phase through the surface of silver bromide. The diffusion rate seemes to depend on temperature.

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Electrophoresis of silver bromide sol containing urea and guanidine were studied at pH 3-11 and pAg 3-11. The concentration of these additives was varied at the range of 0-10^-1 mol/mol AgBr. No effect of these additives on the electrophoresis of silver bromide sol was observed. The conclusion was derived that these additives both does not adsorbe on or react with silver bromide.

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The photographic density obtained by developments with overused developers was found to be influenced effectively by the sort or the combination of surface active agents added to emulsions. A cationic surface active agent had desirable effects for a phenidon-hydroquinon developer and undesirable effects for metol-hydroquinon developers. Either a nonionic or a combination of nonionic, anionic and cationic surface active agents, especially the later, had desirable effects for either developers.(Table I, Table II)
Adsorption on silver halide surfaces of a nonionic surface active agent, polyoxyethylene laurylether was further studied, where, for determination of amounts of polyoxyethylene laurylether, a combination of a precipitation reaction by Bi-EDTA-KI solution and a chelate titration of EDTA isolated by zinc acetate solution using Dotite XO as an indicator was adopted, and it was found to be adsorbed as nearly two times moles as an optical sensitizer, 1-methyl-1'-ethyl-cyanine iodide whether bromide ion presents or not.(Fig. 1-3, Table III)
The mechanism of effects of nonionic surface active agent was discussed. It may be adsorbed on surfaces of silver halides at its hydrophilic portion and form adsorbed micelles. At least, at the first stage of a development, undissociated molecules of developing agents may be solubilized to its lipophilic portion. When development starts and a concentration of developiog agents at the hydrophilic portion decreases, the agents may be supplied quickly from the adjacent lipophilic portion of its micelle because, at the equilibrium, the ratio of the concentration of developing agents at the hydrophilic and the lipophilic portion must be constant.

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This report relates to electron-microscopical observations of developed silver grains reduced from silver bromide emulsion. Two methods of specimen preparation, namely, dissolution method and mesh-developing method, were employed for the observation by electron microscope. The specimen prepared by the dissolution method enabled us to recognize the minute structure of filamentary silver which composed of the developed silver grains. On the other hand, the specimen prepared by the mesh-developing method revealed the shape and composition of individual developing silver grains. The filamentary silver, although originating from one and the same emulsion, showed various structures dependent on change of developing agents, while those which had been reduced from three different types of emulsion by one and the same developing agent exhibited a same type of structure.
We conclude that the filamentary structure of developed silver grains is determined by the type of developing agent, but has little dependence on that of emulsion, and that the shape and size of developed silver grains is determined mainly by the type of emulsion. In the case of a practical developer, the structure of filamentary silver is not so distinguishable as in the case of a single-agent test developer. The coarseness of developed silver grains is controlled by the compactness of filamentary silver in the grains which is influenced by the developing action as well as solvent action of the developer, and the length of developing time.
The so-called fine-grain developer displays both solvent action and surface-development action, and structurally the silver grains contained therein are composed of low-compactness little-frizzled big filamentary silver and have large hollow spaces in original crystals. Consequently, one developed grain appears to the eye as if it were a group of few smaller grains.

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