Halogens are elements in the group seven of the periodic table which includes fluorine, chlorine, bromine, iodine, and astatine but the astatine is not always referred to in most books. These elements are very reactive and they exist as diatomic molecules and they also have low boiling and melting point. Compounds are two or more elements chemically combined together.
Halogens can be produced by the reaction of a solution of a halide ion with a substance that has a higher oxidizing agent. A.J. Ballard was the first scientist to make Bromine in 1826 by simply reacting Cl2 solution that is dissolved in water with bromide ions.
2 Br-(aq) + Cl2 (aq) Br2 (aq) + 2Cl-(aq)
Bromine is reddish and like wisely orange in colour with a choking odour. Bromine is used to prepare flames of fire extinguisher and insecticides, bromine are mostly extracted from sea water which is done in four different stages;
- Firstly reduce the reaction of halogens with water by acidifying the sea water with sulphuric acid which leads to loos of bromine then chlorine will be added to displace the bromine in the solution.
- Extract the vaporised bromine.
- A concentrated solution of hydrobromic acid is produced by mixing sulphur dioxide gas with bromine in presence of fresh water which reduces the bromine to bromide.
After the production of fluorine it was discovered that fluorine is a very reactive and poisonous gas and it is yellowish brown in colour. Fluorine was later found to be used for plasma etching in semiconductor manufacturing and can also be used to produce halons.
Chlorine is known as a powerful oxidizing reagent with a pale yellow-green gas at a room temperature and pressure having a choking smell and is used in bleaching (that is a chemical that removes colours or whitens). As a common disinfectant, chlorine is used in swimming pools to keep them clean and it kills the germs and bacteria in the pool and it is often used in drinking water as well as to purify. Chlorine was discovered by Carl Whillem Scheele in 1774 and Humphry Davy named it in 1810 derived from chloros meaning green referring to the colour of the gas.
Chlorine can be extracted from chloride through oxidation and electrolysis industrially with the equation bellow
Chlorine can be dissolved when it is mixed with water and it can also escape from water and then mix with air. When mixed with water, chlorine reacts with other chemicals then it combines with inorganic and organic materials in water but when it reacts with inorganic materials it forms chloride salt and when it reacts with organic materials it forms chlorinated organic chemicals.
Chlorine is used in the manufacture of organic chlorine compounds, the most significant of which in terms of production are 1,2-dichloroethane and polyvinyl chloride.
Iodine is bluish-black in colour and even if its melting point is 113.5°c it's still a solid at room temperature and pressure, it is the least reactive element among the halogens apart from astatine, it shows some metallic characteristics even if it is a non-metal and it is soluble in water. In 1811 iodine was discovered by Bernard Courtois who named the element after a Greek word called lodes meaning violet. Iodine in nature appears in iodide ions and found in mineral soils.
In conclusion, halogens are used in halogen lamps to be sealed in an in envelope with an inert gas to produce a lightning and halogens are also used in water fluorination, bleach, dry cleaning, and in agricultural fumigant.
- Properties of chlorine from lenntech which can also be available at http://www.lenntech.com/periodic/elements/cl.htm
- another similar copy of the industrial preparation of chlorine can also be found at http://www.tutorvista.com/search/industrial-preparation-of-chlorine-by-electrolysis
- also an industrial use of chlorine from tutor vista.com http://www.tutorvista.com/search/industrial-use-of-chlorine
- the full characteristics and uses of iodine found from chemicool from the website http://www.chemicool.com/elements/iodine.html
- get a copy of the uses of halogens from highway agencies through the website http://www.halogenonline.co.uk/halogenweb/jsp/About/uses.jsp
- click on the following link to get the preparation of iodine from web element http://www.webelements.com/iodine