Latent image formation in thallous bromide-gelatin and related systems

Abstract

Latent Image formation made apparent by double decomposition with AgNO(3) and ordinary development has been studied In thallous bromide-gelatin systems. The plates prepared were found to be much faster than those previously made(11), relatively stable latent Image formation and no reduction in capacity for such formation with time being features noted. The type of gelatin used was found to be largely responsible for the speed Increases.The speed of the emulsion was found to be increased by large amounts of bromine acceptors, but small amounts apparently had little effect. Contrary to previous work (11), the presence of Iodide In Increasing amounts decreased the sensitivity of the plate to blue light.The thallous bromide plates were found to be directly sensitive to green light. Reversal was found to take place with red,green and low intensity blue light, but In the case of the blue light such reversals were only found at much higher primary densities and lower intensity values than In previous work. The straight line relation between the bleaching limit and the primary density was confirmed, A general desensitisation effect was found when malachite green and and methylene blue were aided to finished emulsions and an increase of the intensity of light at which the bleaching limit occurred, was observed.A study was made of the latent image distribution in thallous bromide grains, using dichromate bleachers, surface and total developers, and another reversal effect was observed, which was dependent on the Internal image•The Gurney-Mott mechanism of latent image formation is considered to be applicable in general to the thallous bromide system. An approximate general equation was extended and developed.Finally, some preliminary work was done on the possible latent image formation in lead bromide, antimony oxybromide and bismuth oxybromide. In the last case latent image fomation was shown to be present but was capable of development to a much smaller extent than in the thallous bromide system

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