Chlorine is one of the 94 naturally occurring elements on the planet. It is widely distributed in the earth’s crust, water bodies, plants, animals and human beings. Chlorine was first isolated in the late 18th century by Carl Wilhelm Scheele, a Swiss-German chemist. The yellowish-green color of chlorine gas made Sir Humphrey Davey name this chemical “chlorine” (Greek: khloros means yellowish-green). Chlorine gas is a yellowish-green, toxic gas with a choking smell.
Chlorine is abundantly available on the planet. Being highly reactive, chlorine mostly occurs combined with other elements to form compounds. One of the most well-known chlorine-containing compounds is the common salt or sodium chloride. Scientists have discovered more than 2,000 naturally occurring compounds containing chlorine. Because of its abundance and several desirable qualities, chlorine is used for many purposes such as:
- Disinfecting surfaces: Chlorine is excellent in killing germs. It was first used in 1847 as a germicide (a substance that kills germs) for preventing the spread of “childbed fever” in the maternity wards of an Austrian hospital. Over the last 150 years, chlorine has been one of the most preferred agents to limit viral and bacterial infections. It is used as a surface disinfectant in hospitals, households, swimming pools, offices and public places. Chlorine is a preferred disinfectant in meat- and poultry-processing facilities and sewage and industrial waste disposal plants.
- Disinfecting water: Chlorination is a process to make the water fit for human consumption. It prevents the spread of water-borne diseases such as typhoid, cholera and hepatitis A. Chlorination is a simple, inexpensive and effective method to destroy most viruses and bacteria in water. It is, however, not effective in destroying protozoan cysts.
- Manufacturing polymers: Around one-fifth of chlorine produced is used for manufacturing polyvinyl chloride (PVC). PVC is a light-weight and durable plastic used in making water pipes, blood bags, window frames, car interiors, vinyl flooring and electrical wiring insulation. PVC makes vehicles lighter, thereby increasing fuel mileage.
- Pharmaceuticals: Chlorine is used in the manufacture of various drugs including those used to treat diabetes, high blood pressure, high cholesterol, asthma, seizures, cancer and depression. Around 85 percent of pharmaceutical drugs use chlorine or chlorinated compounds during drug manufacture.
- Chemical warfare: Being toxic, chlorine gas was used during World War I.
- Paper and textile industries: These industries use chlorine or its compounds for bleaching paper and textiles.
- Solar energy: Chlorine plays a crucial role in harnessing solar energy. It is used to purify silicon in sand for making solar panels.
- Other uses: Chlorine is used for making several other products including detergents, solvents, paints, antiseptics, pesticides and dyes. Because chlorine is reactive, it is used in labs to make several chemicals for research purposes through redox reactions (oxidation-reduction reactions). Chlorine is also used for manufacturing car batteries, air conditioning refrigerants, phones, tablets and computers.
Chlorine-containing compounds were used in the past for making anesthetics (chloroform) and dry-cleaning solvents (carbon tetrachloride). Their use has been banned due to their toxicity, particularly damage to the liver.
Chlorine is also essential in living organisms including humans because it
- Maintains salt and water balance
- Maintains electrical neutrality in the body (the negative charge of chloride ions balances the positive charge of other ions such as sodium and potassium ions)
- Helps fight infections
- Helps maintain the pH of the body fluids
- Helps maintain blood pressure
- Aids digestion
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Royal Society of Chemistry