Chemistry and Mechanism of Sivadjian’s Hygrophotographic System

Paper presented at the “Congres International de Science Photographique” held in Paris in September 1965.

Abstract

J. Sivadjian has described a hygrophotographic method for the measurement af humidity and moisture in which a coating of yellow AgHgl₂, darkened by exposure to light, reverts to a yellow colour in the presence of moisture. Using X-ray diffraction techniques the nature of the products formed at each stage in the preparation of the hygrophotographic compound and its photolysis products have been investigated. The compound AgHgl₂ does not appear to exist. The yellow light-sensitive product is a mixture of mercurous and silver halides together with silver tetraiodomercurate (II), Ag₂Hgl₄. A mechanism for the light-sensitive reaction is proposed involving sensitization of the photolysis of mercurous iodide by silver iodide, and silver tetraiodomercurate (II).

Notes

Paper presented at the “Congres International de Science Photographique” held in Paris in September 1965.