Page 5 - Curriculum Visions Dynamic Book

well to other atoms that great energy has to be applied if they are to be separated from their compounds. This may be just as well, because all of the halogen elements are very dangerous. Chlorine, for example, has been used as a chemical weapon in wartime, and fluorine gas is so hazardous that laboratory demonstrations using it were not even attempted for this book!
As compounds, though, the halogens are harmless, even beneficial. Think of the halogens as health-givers. Iodine salts are essential to prevent thyroid gland problems, fluoride strengthens your teeth, and chlorine salts can be used to preserve food and disinfect water supplies. Halogens also make up
many of the commonly used anaesthetics used in surgery.
Chloroform (a compound containing chlorine) was
one of the early anaesthetics; halothane (a compound containing fluorine, chlorine and bromine) is now used in its place.
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 The use of chloroform provided a major step forward in anaesthetics and allowed surgery to be a less traumatic experience than had previously been the case. Procaine hydrochloride (novocaine) is one of the most widely used modern local anaesthetics, used extensively by dental surgeons. Like other local anaesthetics, procaine blocks nerve impulses that carry pain signals.