Present day knowledge on the photographic sensitivity of silver-orthophosphate, silver-Pyrophosphate, and silver-thiocyanate is very poor.
The author succeeded in preparing these emulsions. and examined and measured various chemical, physical and photographic properties.
The manufacturing procedures are the same for ordinaly silver halide emulsions except for several minute changes such as washing which employs dyalysis. The developing and fixing process are also similar to that of silver halide emulsion. Some unique point in these procedure is developing technik of silver phosphate. In this material, very dilute developer will be in good service, moreover, the acidic developer can develop this.
In this paper, the author present several diagrams on characteristic curves of these emulsions, and a table for gamma, sensitivity, and fog values of these.
In addition to these, the solubilities and effective longest wave lengths are determined. The solubility of silver pyrophosphate is 5.7×10^-2g/100g H₂O at 25°C. The longest effective wave length is 561.6mμ for silver orthosphosphate, and 382.2mμ for silver thiocyanate.

View full abstract

It is very important for a maker of photographic emulsion to know the quantity of sulphur compounds in gelatin. It is usually measured by counting bubbles which are formed in a drop of iodine azide solution placed on the surface of gelatin gel. But this method has many defects. 1 The bubbles are not same in their radii, so the number of bubbles does not correspond to the quantity of nitrogen produced by iodine azide reaction. 2 Iodine solution drop placed on a gelatin gel does not always occupy same area. 3 The bubbles may often float up from the gel surface and disappear. This makes it very difficult to count bubbles. In consideration of above defects, the authors devised two new methods. The one has removed the last two defects by dropping iodine solution into a glass ring placed on the surface of gel which contains sodium azide dissolved in it. The other method is a volumetric measurement of nitrogen, using a new instrument with a graduated capillary by which the volume of nitrogen produced by the reaction is measured. Reproducibility and exactness are fairly good.

View full abstract

Photoconductive evidence which is likely to have a direct bearing on the latent image Problem has been obtained by the work of F. C. Toy and G. B. Harrison on large crystals of silver halide prepared by means of fusing.
Photoconductivity has been also demonstrated to occur in actual emulsion by W. West and B. H. Carroll.
Recently M. Tamura and S. Tutihasi have succeeded to prepare silver bromide polycrystalline films by precipitation method at room temperature.
The results of experiments on photoconductive properties of these silver bromide polycrystalline films are given in this paper.
The photocurrents are proportional to the intensity of light in the range which we measured, and have shown proportionality to applied filed strength, up to the maximum used, 40 volts per cm., in white light. No evidence of saturation of these currents has been observed.
The spectral response of photoconductance has exhibited a well-known first band at 460 mμ and an appreciable second band at 640-660mμ.
Dye-sensitization of photoconductivity was also tested but no remarkable effect was observed.
Pressure effect was measured. When the film is put between two silver plates and hammered, it comes to have a tinge of green. This effect is also found when the sample is protected from the direct contact with silver by using cellophane. This greenish film has the notable property that its photoconductance, in the region of wave length of about 400-500mμ, is apparently negative. Such a negative photoconductive effect has never been observed with untreated films in our experiments.
These results are of considerable theoretical interest. Now we think as follows. If crystalline film is hammered, dislocation lines of opposite sign combine and annihilate with a relative large release of energy. This energy excites electrons from filled band to conduction band.
These electrons behave like photoelectrons, and colloidal silver specks are produced accordings to the photographic latent image theory of Gurney & Mott. Thus the film comes to have a tinge of green. If this greenish film absorbs radiation energies and releases photoelectrons, these photoelectrons are captured on the colloidal silver specks. Then colloidal silver speks are negatively charged up. These negatively charged centres may combine with movable silver ion etc. and the electrolytic conductivity is reduced. Thus negative photoconductive effect are caused.

View full abstract

The light source defined in JIS is the combination of a incandescent gas-filled tungsten lamp and a colour conversion filter. The lamp has mono-plane coiled filaments, and is to be burnt at 2660°K (colour temp.) The C-C filter is one of Davis-Gibson's series given in the table 8 in their report.(NBS Misc. Ed. 114) It consists of two cells adjoined, each contains pyridin-aikaline copper solution and acidic copper-cobalt one respectively, and changes the colour of 2660°K radiator to the colour of mean noon sun light.
As none of its spectral characteristics was given in literature, we have computed them in accordance: with Davis-Gibson's calculating method. The relative spectral radiation from Plankian radiator 2660°K is gained from yamanouchi's Table, and the spectral transmission of the filter is calculated from its given concentrations of constituents snd their absorbing coefficients. Integration is carried out numerically by 10 mμ, interval.
The relative spectral energy of 2660°K and the converted one, differences between the true mean noon sun light and the artificial one et al are given in the numerical table and the graph.

View full abstract