Different concentrations of potassium thiocyanate (SCN) were used in combination with Iridium (III) hexachloride (Ir) to surface sensitize an octahedral silver bromide emulsion. Surface sensitivity increased by 0.90 log H over the unsensitized emulsion when Ir and SCN were added during sensitization compared to 0.45 log H when the iridium salt was used alone. A decrease of 2.40 log H was observed when an Ir-SCN complex was formed and then added to the emulsion. An increase of 1.05 log H was obtained if gold, thiocyanate and iridium were used. Similar results were obtained using tetramethylthiourea (TMT) or thiodiglycol (TG) instead of SCN. The emulsion was sensitized with S+Au and Au+SCN for comparison. The mechanism of iridium sensitization is discussed based on the experimental results.
Library of Congress Subject Headings
Photographic sensitometry; Silver halide crystals; Iridium; Ligands
Imaging Science (MS)
Paul Gilman Jr
Zuleta, Juan A., "The Effect of S-donor Ligands on the Sensation of Silver Bromide Crystals with Iridium (III)" (1987). Thesis. Rochester Institute of Technology. Accessed from
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