Iodine Complexes in Inert Solvents. I. I2–I2 in Carbon Tetrachloride and in n-Heptane

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Abstract
The shape of the ultraviolet absorption curve for the I2–I2 complex in CCl4 and in n‐heptane, has been obtained by analysis of the ultraviolet absorption of iodine dissolved in these pure solvents. In this analysis it has been necessary to assume that the assumed equilibrium constant, for the reaction I2+I2⇌I2—I2, does not change with the wavelength. In carbon tetrachloride and in n‐heptane the I2–I2 complex absorption maximum occurs near 2935 A, which is in good agreement with the value predicted by the McConnell, Platt, and Ham relation. The heat of formation of this complex in CCl4, has been estimated as 1.96 kcal/mole (within 0.15 kcal) by assuming that its molar extinction coefficient curve does not change with the temperature. The absorption spectrum of iodine dissolved in CCl4 has been extended to 2250 A, and it has been shown that iodine‐carbon tetrachloride solutions obey Beer's law below 2500 A, a region in which there is strong absorption by CCl4 and no absorption by I2–I2.