CAUSE OF THE RED COLORATION OBTAINED BY PHOTOLYSIS OF SILVER-HALIDE SUSPENSIONS - A STUDY OF PRINT-OUT EFFECT

When irradiated silver chloride suspensions in polyvinyl alcohol were observed spectrophotometrically, two peaks were found: one at 380 nm and the other at 500 nm. Upon treating the irradiated chloride or bromide suspensions with sodium thiosulfate, the red or violet color disappeared and the peaks merged at 420 nm. It is proposed that the two peaks of the colored suspensions were caused by electric dipole interaction in the silver specks that were bound together by silver halide. When polyoxyethylene (20) sorbitan monooleate was used instead of polyvinyl alcohol, and allyl alcohol was added to scavenge halogen, a peak was found at 280 nm upon irradiation. With further irradiation, the 280-nm peak decreased with simultaneous increase in the peaks at 400 and 550 nm, and an isosbestic point was found upon superimposition of the spectra. It is proposed that the 280-nm peak was caused by small silver clusters, possibly Ag42+, which acted as precursors to the larger silver specks.