The Infra-Red Absorption of Brucite and Some Sulphates; Isotopic Effect

By means of an infra-red spectrometer the structure of the absorption band of brucite [Mg(OH)₂] was studied. The region of greatest absorption was found to be at 2.48{μ}. Besides this maximum there were small maxima of absorption located at 2.40{μ}, 2.30{μ}, 2.14{μ}. The maxima at 2.48{μ}, 240{μ}, and 2.30{μ} correspond approximately in position and absorption to the isotopes of Mg²⁴, Mg²⁵, and Mg²⁶ as found by Aston. The small band at 2.14{μ}, corresponds in position to Mg²⁸. However, this isotope is not given. The work of Coblentz has been examined for the isotopic effect. In the reflection spectrum of nickel sulphate in solution there are two maxima located at 9.15{μ} and 9.50{μ}. The second is more intense. These maxima are probably due to Ni⁵⁸ and Ni⁶⁰. In the spectrum of potassium sulphate there are two maxima, one at 9.00{μ} and the other at 9.40{μ}. The maxima at 9.40{μ} is much more intense. These two maxima are probably due to K³⁹⁺⁴¹ and KR³⁹ taken twice. Other sulphates in solution showed only one maximum. The sulphates of barium, strontium, and magnesium in the solid state also had complex maxima. As the light was unpolarized, these maxima might be due to pleochroism.