Gold Sensitization Experiments

The paper describes the sensitization of a neutral iodobromide gelatin emulsion by gold thiocyanate. The variables studied were grain size, the stage of emulsion preparation at which the gold additions were made and the amount of gold added. The greatest increase in sensitivity was obtained by adding the gold thiocyanate solution immediately before the second ripening (digestion). The increase was inversely proportional to the grain size. At the same time the gradation was also increased. In two cases the gold solution was added before washing of the emulsions, very little sensitizing was observed, and the gradation tended to fall. The results confirm that a certain relation exists between the increase in sensitivity due to gold thiocyanate and the grain size (or the grain surface).