Physico-chemical mechanism of the argyrophil III reaction.

Because there are several points of physico-chemical similarity between the argyrophil I reaction (formation of metallic silver grains by reducing groups of the tissue) and the argyrophil III reaction (formation of metallic silver grains by reducing groups existing in a dissolved state) a similarity between their mechanisms is also assumed. The electrochemical half processes of the argyrophil III reaction (i.e. the transformation of tissue-adsorbed reducing molecules into their oxidized form, and the reduction of silver ions to silver atoms) take place separately in space, while the electrons released in the former half reaction are transported by the semiconduction bands of the tissue to the catalytic points where the metallic silver grains are forming.