What is chlorine?
Chlorine is commonly found in nature, but almost always in combination with other building blocks. Chlorine's structure makes it very reactive (its outer shell is missing just one electron), which makes it attractive to other atoms and molecules. Because it is so reactive, it is very useful to chemists, engineers and other people involved in making things we use every day. When combined with other chemical building blocks, chlorine can change the nature of a substance, and build or improve a product.
Chlorine chemistry is deeply woven into the fabric of our lives. In 1774, in his small experimental laboratory, Swedish pharmacist Carl Wilhem Scheele released a few drops of hydrochloric acid onto a piece of manganese dioxide. Within seconds, a greenish-yellow gas arose. Although he had no idea at the time, he had just discovered chlorine. The fact that the greenish-yellow gas was actually an element was only recognized several decades later by English chemist Sir Humphrey Davy. Until that time, people were convinced that the gas was a compound of oxygen. Davy gave the element its name on the basis of the Greek word khloros, for greenish-yellow. In 1810 he suggested the name "chloric gas" or "chlorine."
What happens to chlorine when it enters the environment?
Chlorine is one of 90 natural elements, the basic building blocks of our planet. To be useful, an element must be relatively abundant or have extremely desirable properties. Chlorine has both characteristics. As a result, over the course of many decades of careful research and development, scientists have learned to use chlorine and the products of chlorine chemistry to make drinking water safe, destroy life-threatening germs, produce life-saving drugs and medical equipment, shield police and fire fighters in the line of duty, and ensure a plentiful food supply.
One of the most effective and economical germ-killers, chlorine also destroys and deactivates a wide range of dangerous germs in homes, hospitals, swimming pools, hotels, restaurants, and other public places. Chlorine's powerful disinfectant qualities come from its ability to bond with and destroy the outer surfaces of bacteria and viruses.
First used as a germicide to prevent the spread of "child bed fever" in the maternity wards of Vienna General Hospital in Austria in 1846, chlorine has been one of society's most potent weapons against a wide array of life-threatening infections, viruses, and bacteria for 150 years. Chlorine opens doors to thousands of social and public health benefits. Each time you drive your car, drink a glass of water, wear vinyl rain gear, take vitamins or put on perfume, chlorine is working for you.
Some people are surprised to learn that chlorine works for the environment, too.
- Chlorine is an important component in the development and manufacture of materials that make vehicles lighter, thereby increasing gasoline mileage.
- Crop protection chemicals that depend on chlorine result in far higher crop yields, thereby relieving pressures to convert to agricultural use rainforests and other ecologically important lands.
- Chlorine even plays an important role in harnessing solar energy, purifying the silicon found in grains of sand and helping transform them into solar panel chips.
In so many ways, chlorine is part of the bedrock of sustainable development efforts and other central tenets of modern environmental protection.
Because Chlorine is highly reactive, it is usually found in nature bound with other elements like sodium, potassium, and magnesium. When chlorine is isolated as a free element, chlorine is a greenish yellow gas, which is 2.5 times heavier than air. It turns to a liquid state at -34°C (-29°F), and it becomes a yellowish crystalline solid at -103°C (-153°F).
Order Free Materials from the Chlorine Chemistry Council®
These easy-to-read, full-color brochures illustrate chlorine's beneficial role in our everyday lives with vivid text and photographs. Please click on the links below to go to their page, you'll be glad you did.
Teacher Education Materials
The Chlorine Chemistry Council® (CCC) is proud of its commitment to science education. Through our partners we have supported the development of several modules and classroom activities that can help teachers when discussing chemical elements and the environment in their classrooms.
The History of Chlorine
Chlorination has played a critical role in protecting America's drinking water supply from waterborne infectious diseases for 90 years. One of the first known uses of chlorine for water disinfection was by John Snow in 1850, when he attempted to disinfect the Broad Street Pump water supply in London after an outbreak of cholera...
Natural Chlorine? You Bet!
Most people know that table salt, a natural mineral essential for the proper functioning of our nervous and muscular systems, is sodium chloride. But many would be surprised to know that...
Life Wouldn't Be the Same Without It
This 13-page booklet provides an overview of the following six brochures that highlight the different aspects of chlorine chemistry's societal benefits. An all-purpose, general tool to communicate several benefits of chlorine chemistry, the brochure also provides useful quotations from physicians and health officials on the significance of chlorine chemistry.
Chlorine and Drinking Water: Here's to Your Health
Chlorine's water disinfection capabilities are unmatched. This brochure describes chlorine's key role in providing safe drinking water, in addition to facts about chlorine's role in cleaning up natural disasters.
Chlorine: Enhancing Everyday Life
Many people are unaware of the many products made with the help of chlorine chemistry. From microprocessors and wires in computers to vinyl siding, windows and plumbing pipes in homes, this brochure depicts chlorine's diverse role in producing hundreds of products we rely on every day.