Preparation of a Simple Thermochromic Solid Mlchiel J. M. Van Oort Merck Frosst Canada, Inc., P.O. Box 1005, Claire-Do~al,Quebec, Canada H9R 4P8 The following preparation of a simple transition-metal salt is suggested as an easy, dramatic, and effective laboratory introduction to solid-solid phase transitions, thermochromism, and color changes associated with changes in ligand coordination, suitable for undergraduate students in physical and general chemistry. Thermochromism is the reversible change in color of a compound when it is heated or cooled. There are two classes of thermochromism. The first is a eradual change - in color with increasing temperature, which has been called continuous thermochromism ( I ) . The second is a dramaticchange in color that takes place at a specific temperature or over a small temperature ranee and has been called discontinuous thermoch;omism. ~is'ontinuous thermochromism in inorganic compounds is usually due to a solid-to-solid phase
