I. The acceleration of oxidation caused by the least refrangible end of the spectrum

Abstract

In a paper contributed to the Philosophical Magazine in January last, I expressed an opinion that Chastaing’s idea regarding an acceleration of oxidation being caused by red light might prove true in regard to the oxidation of the photographic image, and elsewhere that Becquerel’s coloured spectra and Draper’s reversed spectra might be explained on the same principles. Owing to want of time until this last week, I have been unable to investigate the matter, but can now affirm that such is the case as regards oxidation of the photographic image. Silver bromide, free from contamination, emulsified in collodion, which had been previously carefully purified, was spread on a plate, and exposed to diffused light. It was then submitted to the action of the solar spectrum, while immersed in a solution of potassium permanganate, or hydroxyl. When the strength of the permanganate, or hydroxyl, was correct a reversed image of the least refrangible end of the spectrum was obtained, an increase in oxidation taking place when the red rays acted, the reversal taking place somewhere near D, extending into the ultra-red.