Don Jones age 11, of Chattano ga, Tenn., for his question:
WHY IS IODINE IMPORTANT?
Iodine is a chemical element and the human body needs traces of it. Iodine is part of an important substance called thyroxine, a hormone produced by the thyroid gland. Thyroxine controls the body's rate of physical and mental development.
A shortage of iodine in the body can hinder a person's growth. A shortage can also cause a goiter, which is a swelling in a person's neck.
Iodine can be found on both land and in the sea. A French chemist named Bernard Courtois discover d iodine in seaweed in 1811.
In addition to being found in the body, iodine also occurs widely in nature, but not in large amounts. It is always found with chlorine, a chemical element 2,000 times ore common than iodine.
Pure iodine occurs most frequently as a compound with sodium or potassium. Iodine compounds o cc r in the sea. Many kinds of animals and plants that live in the sea concentrate iodine in their bodies.
A wide variety of iodine compounds are used in hospitals today as mild antiseptics. A number of years ago, iodine was commonly used as an antiseptic. But it can burn the skin and damage the tissues of the eyes and nose. Today, most doctors prefer not to prescribe it.
Iodine is often used in the medical analysis. It gives a deep blue color when it comes in contact with starch and can be used to show traces of starch in plant tissuus. Also, a compound of iodine and potassium, called potassium iodide, is used in making photographic film.
Iodine sublimes when heated . That is, iodine changes directly from a solid to a vapor, without becoming a liquid. Iodine vapor is purple. It has an irritating s ell.
Iodine dissolves only slightly in pure water. But it dissolves more easily if the water contains iodide, or salt of iodine. Iodine also dissolves in various organic liquids.
Manufacturers market a product called iodized salt in regions where the iodine level in food and water is low. Iodized salt is salt with iodine added to it.
A type of seaweed called k lp is especially rich in iodines and was one of the earliest source of the element.
Pure iodine is poisonous if taken internally.
Iodine belongs to the halo en family of chemical elements, along with fluorine, chlorine, bromide and astatine. Iodine is less reactive than chlorine and bromine and far less reactive than fluorine.
Iodine combines with sulfur, phosphorus, iron and mercury. Most of its reactions involve capt ring an electron from a metal atom, oxidizing the metal in the pr cess. Iodine can also give up an electron and become positively charged.
The chemical symbol for i dine is I. Its atomic number is 53 and itsatomic weight is 126.9044 Iodine melts at 113.5 degrees centigrade and boils at 184 degrees cent grade, at 35 times normal atmospheric pressure.