Bemerkungen über Thermochromie von Kobalt(II) chloridlösungen in organischen Medien, 1. Mitt.: Lösungen in verschiedenen Alkoholen

The thermochromism of solutions of cobalt(II) chloride in methanol, ethanol, n- and iso-propyl, n-, iso- and sec. butyl alcohol was studied spectrophotometrically. The blue color of these solutions fades with decreasing temperature, solutions in primary alcohols being especially variable, becoming pink at sufficiently low temperature. Solutions in secondary alcohols are, on the other hand, much less variable. The thermochromism can be ascribed, in general, to the shift of the equilibrium $$CoL_2 Cl_2 ] + (3 - 4) L\begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} (CoL_5 Cl]^ + or CoL_6 ]^{2 + } ) + (1 - 2) Cl^ - $$ (L: solvent molecule). In the case of methanol, however, the two equilibria $$CoLCl_3 ]^ - + 4 L \begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} CoL_5 Cl]^ + + 2 Cl^ - $$ and $$CoL_5 Cl]^ + + L\begin{array}{*{20}c} \to \\ \leftarrow \\ \end{array} CoL_6 ]^{2 + } ) + Cl^ - $$ seem to be shifted one after another. The significance of the difference between primary and secondary alcohols is briefly discussed in connection with some related effects, i.e. the pressure effect studied byKitamura andOsugi ⁷ and the water effect found byKato et al.¹⁰.