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${\mathrm{}\left(\mathrm{OH}\right)\mathrm{}}_2$] was studied. The region of greatest absorption was found to be at 2.48μ. Besides this maximum there were small maxima of absorption located at 2.40μ, 2.30μ, 2.14μ. The maxima at 2.48μ, 240μ, and 2.30μ correspond approximately in position and absorption to the isotopes of ${\mathrm{Mg}}^{24}$, ${\mathrm{Mg}}^{25}$, and ${\mathrm{Mg}}^{26}$ as found by Aston. The small band at 2.14μ, corresponds in position to ${\mathrm{Mg}}^{28}$. 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 9.15μ and 9.50μ. The second is more intense. These maxima are probably due to ${\mathrm{Ni}}^{58}$ and ${\mathrm{Ni}}^{60}$. In the spectrum of potassium sulphate there are two maxima, one at 9.00μ and the other at 9.40μ. The maxima at 9.40μ is much more intense. These two maxima are probably due to ${\mathrm{K}}^{39+41}$ and K${\mathrm{R}}^{39}$ 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.