IODINE. This remarkable non-metallic elementary body was discovered by M. Cour tois in 1812. Iodine exists in the water of the ocean and mineral springs, and in marine molluscous animals and sea-weeds ; but it is principally obtained from kelp, or sea-weed which has been burnt for the purpose of ob taining alkali. It is a soft opaque solid, of a blueish black colour and metallic lustre. When moderately heated, it rises in vapour of a vio let colour, and hence its name from the Greek word for violet. On cooling, it again crystal lises unchanged, nor is it decomposed or altered by being subjected to very high tem peratures ; and it has resisted all attempts to decompose it.
Iodine has a strong disagreeable odour and taste ; it stains the skin of a brownish colour, but not permanently. It is readily dissolved by alcohol, hut scarcely at all by water. It is very poisonous. Its characteristic property is that of giving an intense blue colour when added to a solution of starch. It unites with metals to form compounds, which are termed Iodides ; and, like chlorine and bromine, it forms acids both with hydrogen and oxygen.
Iodine, though only obtained in an isolated state of late years, has been long employed as the e eient principle of other preparations and therapeutic agents, namely, burnt sponge and certain mineral waters. It is only since
it has been procured as a distinct principle that its action has been ascertained with pre cision. In the present day it is administered rather in some artificial compound than as pure iodine, owing to its very sparing solubi lity in water. Its value in medicine is very great.. In photographic processes and in other processes connected with the arts, iodine is also very useful.
At the Dublin Exhibition of manufactures in 1850, the Messrs. Bullock, manufacturing chemists of Galway, exhibited specimens of Irish iodine. It appears that iodine is found in largo quantities in the sea-weed which covers the rocks for miles round the west coast of Ireland ; it has been hitherto collected by the peasetns for manure ; but Messrs. Bullock hare found that it will yield incline in sufficient quantity to pay for the extraction. This affords one among many exemplars of the advancing spirit of manufactures in Ireland.