Iodine

i o-din, a chemical element akin to chlorine and bromine. It was obtained originally, 1811, from the ashes of a seaweed called kelp, but is now produced more cheaply from an earth abounding in the mountains of northern Chile. A ton of ashes of kelp yields about eight pounds of iodine. The name is Greek signifying "like a violet." The solid is a soft, grayish substance, but its vapor is of a beautiful deep blue. Starch is used to detect the presence of iodine, and iodine is used in many experiments and botanical examinations to detect the presence of starch. A pinch of starch dropped into a glass of water containing a millionth part of iodine turns blue at once. Tincture of iodine--iodine dissolved in alcohol--is a valuable medicine. It is an irritating poison if taken in too large a quantity. Iodine kills the microbes of certain diseases. It is peculiarly valuable as an ointment for rheumatism. It is also used in photography in the preparation of sensitive plates, and in the preparation of coal tar colors. Iodine is a nonconductor of electricity.