I. Absorption-spectra of iodine

Iodine, as is well known, when in very thin layers, appears red by transmitted light; and when in solution the colour of the liquid depends not only on the amount of iodine contained in it, but also on the nature of the liquid in which it is dissolved. Schultz-Sellack has pointed out (Pogg. Ann. vol. cxl. p. 334) that the liquids in which iodine is soluble may be divided into two classes:— first, those with which it gives reddish-brown solutions, like alcohol; and secondly, those with which it gives violet ones, as bisulphide of carbon; and also that the colours of these two solutions correspond respectively with the colour of solid iodine, when seen by transmitted light, and with that of iodine vapour.