The detailed investigations of the reciprocity-failure characteristic of the iodobromide emulsion should be of considerable value, not only for the understanding of the function of iodide, but for the mechanism of reciprocity-law failure. A pure bromide emulsion and iodobromide emulsions containing 2.5 and 7.5 mole percent iodide contents respectively were used. By the admixture of iodide into bromide, the conductivity of silver ions may be changed. Then the high intensity failure part of reciprocity failure curve for bromide emulsion will undergo a change. The experimental results of this study have confirmed the above prediction. It was concluded that by admixture of iodide into bromide the conductivity of silver ions at the sub-surface of microcystal increase, but not at the surface. Therefore, the internal latent image formed easily. It was also concluded that in the iodobromide emulsion the, internal conductivity of silver ions is larger than the surface conductivity, but the reverse is the case in the bromide emulsion.

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A thin silver bromide layer was prepared in molten state between two glass plates. After setting free the bromide crystal glass plates, the surface was smoothened by potassium cyanide solution. The crystal was irradiated by mercury lamp and the printing-out image was observed under the electron microscope. The image took the chain shape and developed as the branch of tree. After 20 min., this growed to about 600Å and 80 min. 900Å The author observed also the effect of the temperature on the printing-out image.

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In 1952 Roman had reported at first time on the rapid development by vanadium ion. Really this was a remarkable work which would give the revolution in the work of positive film development. Therefore the present authors dared to follow this work with Japanese positive films. They tried three methods of dissolving vanadium pentoxide by sulfur dioxide, hydrogen bromide and oxalic acid. That of hydrogen bromide gave the best result. The electrolytic reduction of quadrivalent vanadium to bivalent by lead electrode was of the current efficiency of 40%.
The development was effected at 10, 13 and 15°C and during 10, 15, 20 and 25 sec. The good result was obtained under 15°C during 25 min. The resolving power did not decrease in this condition compared with D-16 developer.
An automatic developer device was designed having the speed of treatment of 2 min. from the beginning of development until the drying.

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