The quantitative IR spectroscopic determination of structural OH groups in kyanites

Abstract

Kyanites from different occurrences show in the near IR two relatively strong absorption bands at 3 380 and 3 270 cm−1 due to OH stretching frequencies. The integral molar extinction coefficient is 3201 · Mol−1 · cm−2. A quantitative IR spectroscopic microtechnique based on Beer's law allows to determine small amounts of structural OH groups in (100) cleavage plates of a few tenths mm in size proved to be free of inclusions and hydrous alteration products. There exists an obvious relation between the occurrence of the kyanites studied and their equivalent H2O+ content ranging from < 0.005 to 0.180 wt.%.