Date of this Version
The first quantitative investigation of absolute phase change was made by Quinckel in 1872. This was followed by that of Wernicke, Wiener, Glan, Hennig, Drude, Koenigsberger and Bender. All these investigations were confined to the visible spectrum except that of Koenigsberger and Bender, who, in addition, measured for a few substances the phase change in the infra-red. So far no measurements of this phenomenon have been made in the ultra-violet.