The action of hydrogen peroxide on photographic gelatino-silver halide emulsions

1. The sensitometric characteristics of photographic plates exposed to hydrogen peroxide and developed are strikingly similar, both for time of exposures, time of development, and intensity i.e., concentration). Characteristic curves similar to H. and D. curves were obtained, including a period of “reversal.”2. A tentative theory of the action of hydrogen peroxide is suggested. It is supposed that the decomposition of peroxide is chemi-luminiscent, short wave-length radiation being afforded at the surface of the silver halide grain, and particularly at check the hypothesis that these nuclei consist of colloid silver.The authors desire to express their thanks to Mr. R. F. Quirk and Mr. E. Huberth for painstaking assistance in the experi- mental work, and to Miss Anber J. Benedict for making the pH measurements.     

The development of the solarized latent image

An investigation has been made of the development of the solarized latent image with p-amino-phenol, pyrogallol and hydroquinone developer without potassium bromide, and with a series of hydroquinone developers containing potassium bromide from 0.002N to 0.269N solution. These developers represent a series with different reduction potentials. The investigation was restricted to a pure silver bromide emulsion.It was shown by the application of the Bravais-Pearson method of determination of the correlation coefficient that A. H. Nietz' straight line proportionality between density and the logarithm of the potassium bromide concentration holds in general for normal exposures, but that in extreme cases of exposure and development, deviations from the straight line proportionality are detectable. This proportionality holds only in a limited way for the solarization region. At the threshold of the first reversal of the solarization there is no correlation at all.The criterion that a family of curves has, or has not, a tie-point was investigated by the determination of the correlation coefficient between density and gamma. It was shown that the tie-point of the solarization curves moves toward the origin of the distance/log E axes with increasing content of potassium bromide in the developer.     

The blackening of photographic plates by positive ions of the alkali metals

A short review is included of previous work on the blackening of photographic plates by positive rays and rays of an analogous nature.The blackening of Eastman x-ray plates, by positive ions, has been measured as a function of the energy of the ions of Li, Na, K, Rb, and Cs. The energy of the ions required to produce a photographic density of D = 0.3 with a one minute exposure at a current density of 1.32 × 10^?8 amperes per cm.² ranged from 1420 electron-volts in the case of cæsium to 860 electron-volts in the case of Li⁷. Approximately 10⁵ ions are required at these energies to render developable one silver-halide grain. For a threshold density, D = 0.04, under the same conditions the energy ranged from approximately 920 to 460 electron-volts for Cs and Li⁷ respectively.Sensitivity comparisons were made between x-ray plates and process and schumannized process plates. Potassium ions with an energy as low as 137 electron-volts were recorded on Schumann plates, and it is possible that positive ions of one-third this energy can be recorded.