Silver Deposition In the Diffusion Process

A theoretical explanation is offered to account for the dependence of the density and colour of a silver-gelatin coating on the packing density of the single silver particles. Experimental results concerning the use of silver coatings are communicated.

1. Coatings with a very high volume concentration of silver (>3 per cent) show a high density and a shift of the colour tone to black. The particle size is not of great influence.

2. Coatings with a small volume concentration of silver show a colour tone which depends on the size of the single aggregates and can approximately be calculated according to Mie’s theory.

3. In the experiments performed the addition of blue toners was always connected with the formation of zones with a high volume concentration of silver so that a genuine shift of colour tone cannot be separated from the effect of a high volume concentration. A blue toning effect caused by poisoning of the nuclei also happens and is to be explained.

4. The existence of genuine blue toners remains open. It can only be said to be established when coatings of the same volume concentration and of the same particle size look yellow to brown without additive and blue black with additive.