Photoacoustic infrared spectra (250–10 000 cm−1) of partially deuterated kaolinite #9

Partial deuteration of kaolinite #9 was accomplished by grinding lumps to a size of 9 μm and refluxing a D 2 O suspension for periods ranging from 8 to 146 h. Photoacoustic infrared spectra were obtained and compared with previously published infrared and Raman spectra of undeuterated kaolinite and with infrared spectra of deuterated kaolinite. Data from this investigation indicate an extent of deuteration of about 20%; with the exception of the OD stretching bands near 2700 cm −1 , most of the bands observed are attributable to undeuterated kaolinite. The infrared band at 2718 cm −1 , which was previously assigned to uncoupled inner surface OD stretching, is the analogue of the 3684 cm −1 band observed in Raman and photoacoustic infrared spectra of undeuterated kaolinite. The results support assignment of the 3684 cm −1 band to uncoupled inner surface hydroxyl stretching vibrations.