IODINE, (Greek taric violet coloured,) I=126. This elementary substance is contained in minute quantity in sea water, and some mineral but enters more largely into the composition of cer tain sea weeds, chiefly found on the western coasts of Ireland and Scotland; a minute trace has also been found in cod liver oil, and in the yellow sap of the " Indus fetediseimue." Iodine is chieflymanufactured in Glasgow, fromkelp. (See "Kelp.") This is lixiviated in cold water, and the solution gradually evaporated, when the various salts which it contains, and which are less soluble than the iodides, crystallize and are removed in succession. The dark mother liquor which remains contains the iodides. From these the iodine is separated by distilling the liquid with sulphuric acid and black oxide of manganese. The iodine passes over as a violet coloured vapour which condenses in the alembic and neck of the retort in lon,g pointed crystals of a dark colour, opaque, and having a metallic lustre.
These are washed out with a little water, and dried with blotting pa per. The process is minutely described in Dr. Graham's Elements of Chemistry.
Iodine is sparingly soluble in water, but dissolves readily in alcohol and ether. The commercial sample may be purified by disssolvinc, it in alcohol and precipitating it with water. The impurities, or aduf terations, are principally plumbago, sulphide of antimony, and black oxide of manganese, all of which are insoluble in alcohol. Iodine is dissolved by solutions of the alkaline iodides.
Iodine is extremely volatile when moist. At 120° it rises rapidly into vapour, at 220° fuses, and at 350° boils and produces dense violet coloured fumes which crystallize in brilliant plates and acute octohedra. The aqueous solution of iodine does not evolve oxygen when exposed to sunshine, nor has it bleaching properties.