The photographic properties of silver sulfide: Part 2. The print-out effect-chemical aspect

Abstract

This paper is, in itself, a summary of a large number of experimental facts, each one of which has perforce received less than its proper meed attention. A summary of such a collection can be made only by a process of elimination, designed to give prominence to the more interesting items. Of these, the following have been chosen: 1. (1)Silver sulfide is sensitive to light and accumulates metallic silver when illuminated under solutions containing free silver ion. 2. (2)This is a general phenomenon but is exhibited best in solutions of sodium silver sulfite and of sodium silver nitrite. 3. (3)The yield of silver is not related stoichiometrically to the quantity of silver sulfide or the wastage of sulfur. 4. (4)This “photographic effect” is altered profoundly by gelatin and changes of pH. 5. (5)The silver sulfide is sensitive to the whole visible spectrum, and far into the infra-red. 6. (6)There is a marked reciprocity failure which differs in direction and degree for the sulfite and nitrite solutions. 7. (7)The effect in nitrite solution shows an apparent negative thermal coefficient. 8. (8)The mechanism of the reaction in nitrite solution is thought to be relatively simple; that in sulfite solution is known to be complex.