Chlorine By Natalie Coughlin |
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| The name chlorine comes from the Greek word khlôros,
meaning "green." It was discovered in 1774 by a Swedish chemist named Carl
Wilhelm Scheele. It is the seventeenth element on the Periodic Table. It is classified as
a Halogen. By itself, it has a very distinct odor, although smelling it is not advised. As
a solid, it is green in color. Liquid chlorine is amber in color. Chlorine gas (in low
concentrations) is almost invisible. Chlorine compounds have many very different physical
characteristics. Originally chlorine was used as a fabric bleach, replacing the previous method of leaving fabric in the sun for six weeks. It wasn’t widely used, however, because it corroded the metal machinery and other equipment, but when it was combined with a potash solution it was used more often. Compared to all the other elements, chlorine is the one of the most active. It is rarely found free because it joins almost every element that it meets. That fact is the reason why it is so often found in nature and in products. It makes up about two percent of the total weight of all the seawater on earth. It is in our bodies as well as in our blood. In our stomach, it is combined with hydrogen to form hydrochloric acid to aid in the digestion of food. It greatly decreases the possibility of waterborne diseases when used as a water disinfectant. Chlorine can be found in many different products: laundry bleach, cosmetics, table salt, tents, running shoes, camera film, nylon, soft drinks, school books, computer parts and much, much more. We obtain chlorine through electrolysis. An electrical current is passed through salt water and the positive sodium ions and negative chloride ions are split. The negative chloride ions collect to form molecular chlorine gas. The gas is dried, chilled and is either pressurized or converted into liquid for storage and shipping. Chlorine has a major role in maintaining public health. It is used as a water disinfectant. It destroys life-threatening diseases such as cholera, dysentery and typhoid. Some studies suggest that it can cause certain types of cancer, but scientists say that its many benefits outweigh its possible harm. Worldwide, over 25,000 children die each day because of inadequate drinking water. Sanitary drinking water is so crucial to human existence and many people take it for granted. Our own immune system uses chlorine, bromine and iodide to halogenate and kill invading microorganisms. One very natural biological process is chlorination. Enzymes in our white blood cells oxidize natural blood chloride into active chlorine. This, in turn, kills foreign pathogens (bacteria, yeast, fungi, and even tumor cells). Organochlorine (organic chlorine chemicals) compounds are produced by various organisms and play an important role in the organisms’ survival. Many of these compounds are used in the organisms’ chemical defense (as deterrents, irritants, or pesticides). One marine algae compound (telfairine) is 100% lethal to mosquito larvae at 10 parts per million (ppm). It is related to the commercial chlorinated pesticides. Other organochlorides are hormones. Lentils and sweet peas use 4-chloroindoleactic acid as growth hormones. The German cockroach makes two chlorinated steroids as trail pheremones. The Lone Star tick produces a organochloride as a sex pheremone. A tiny Ecuadorian frog secretes a chlorinated alkaloid that was discovered to be 500 times more powerful than morphine (as a painkiller). It is believed to be used as a defense against birds. |
