The chemical element chlorine, named from the greek ‘chloros’ meaning greenish yellow, is a highly reactive halogen that was first discovered in the early 1600s when it was first synthesised. Although it is the second most abundant substance in the earth’s crust, it wasn’t recognised as a pure element until much later in 1810. Chlorine is an essential reaction compound making it one of the most versatile elements discovered. Its uses are of great importance for the production of pharmaceuticals, disinfectant, bleach, insecticides, chemical weaponry in WW1 and WW11, and the balancing of ions in cells of the body.
“Due to its highly reactive state, chlorine is usually found in nature as a compound with other elements such as sodium, potassium and magnesium. When chlorine is isolated as a free element, it is two and a half times heavier than air. It turns into a liquid state at -34degrees and becomes a yellowish solid crystalline at -103degrees.” ( Chlorine Story, American Chemistry Council, n.d)
The most common derivative of chlorine comes in the compound form of sodium chloride, commonly known as table salt, and archaeologists have found evidence that rock salts have been used as early as 300BC. Swedish chemist Carl Wilhelm Scheele is credited to have discovered chlorine as he was the first to prepare and study chlorine in 1774. Scheele recorded this dense, greenish-yellow gas as having a strong choking smell that dissolved in water to give an acid solution; noting that it bleached litmus paper and de colourised leaves and flowers. At the time he believed it was a gas in the form of hydrochloric acid, then known as muriatic acid, but he failed to recognise chlorine as a pure element. It wasn’t until several decades later in 1810 that another chemist named Sir Humphry Davy concluded that chlorine was an element rather than a compound, giving it its name chlorine.
Chlorine is the second most abundant substance in the earth’s crust and the eleventh most abundant element in the lithosphere. “In nature, volcanic eruptions are the sources of great masses of hydrogen chloride, they also contain free chlorine gas. Breaking waves and winds over the oceans produce large amounts of sea salt aerosols in the atmosphere, corresponding to ten billion tons of chloride per year.” (Schmittinger, 2008, pg 15).
Chlorine gas it also produced commercially by the electrolysis of sodium chloride, NaCl, from seawater or brine from salt mines.
Chlorine is used in many everyday consumer products from medicines, antiseptic, disinfectants, foods, solvents, plastics, paints, dyes and paper products. It can come in forms such as powder, granulated and gaseous. In the past chlorine was commonly used to make the anaesthetic chloroform and a dry-cleaning solvent carbon tetrachloride. Both of these chemicals are now strictly controlled as they have been reported to have caused liver damage.
Chlorine gas was used as a WW1 chemical weapon in the trenches and by front line soldiers to take out enemy arsenals but proved unsuccessful as the chlorine has was easily detectable by its suffocating, rotten odour and greenish-yellow colour. As chlorine is polar the soldiers soon discovered they could protect themselves by holding wet cloths over their face to dissolve the gas and reduce toxicity on the body.
“The use of poisonous gases during WW2 was a very real fear as many new gases made an appearance including mustard gas, cyanide, carbon monoxide and cyanogen chlorides. Many of these new gases were far more deadly than chlorine gas, sure and relatively painless. As a result people were issued with gas masks and gas mask drills became a routine.” (historylearningsite, 2015)
Chlorine in its biological role is essential in the regulation of acid-base homeostasis, maintaining electrical neutrality and osmotic pressure of extracellular fluids. Chlorine is present in the cell as a negative ion that reacts with a positive ion, usually potassium to balance the cell, and transports oxygen and carbon dioxide through the blood plasma. Combining it with sodium makes it the most important electrolyte in the body which are needed for conduction of nerve impulses and muscle function. With the loss of electrolytes the muscles can become tensed and contracted, losing their efficiency to perform their function. Chlorine is a component of all body secretions and excretions which results in providing the maintenance of digestive juice ph by both the anabolism (building) and the catabolism (breaking down) of body tissues.
As chlorine is typically found in compound form, a person can easily get their daily intake from salts found in foods products like meat, green leafy vegetables, melons, canned foods, eggs, salt and milk.
“Although chlorine can be stored in the body to an extent in the skin, subcutaneous tissues and skeleton, its supplies are rapidly depleted during hot weather and excessive perspiration. In diseases that produce severe alkalosis, and extended bouts of vomiting and diarrhoea, stored chlorides in the body may become dangerously low. Symptoms of a deficiency in chlorine can result in dry tongue, lost elasticity in skin, muscular cramps, imbalance of fluid levels and a loss of teeth and hair.” (Tandurust, 2008)
Chlorine can cause allergy symptoms such as red, sore eyes, coughing, wheezing, sneezing, running nose and dry skin. Although it is not common if a person experiences headaches, nausea and vomiting and suspects its an allergy to chlorine, it’s important to stay away from chlorinated articles.
Since its discovery several centuries ago, man-kind has been able to further research and discover the important benefits and uses of chlorine in the human body and use in industrial operation. Chlorine in the human body has many important roles in maintaining health and wellness of cell production and homeostasis. Levels of chlorine in the diet usually coincide with sodium intake and can be easily adapted into a healthy diet including plenty of wholegrain, fruits and vegetables; and chlorine deficiency is extremely rare. With its usage in the industrial practice, chlorine will continue to benefit consumers and researchers will find new innovative ways to utilise the chlorine element.
American Chemistry Council (2005-2016). The chlorine story: How Chlorine Chemistry is woven into our lives. Retrieved from http//www.chlorine.americanchemistry.com/what-is-chlorine/chlorine-story
Royal Society of Chemistry (2016) Periodic Table: Chlorine. Retrieved from HYPERLINK “http://www.rsc.org/periodic-table/element/17/chlorine”www.rsc.org/periodic-table/element/17/chlorine
Schmittinger, D. (November 21, 2008). Chlorine: Principles & Industrial Practice. Wiley-vch
Tandurust (February 5, 2008). Function of Chlorine:Deficiency Symptoms and Uses in Daily life. Retrieved from http// HYPERLINK “http://www.tandurust.com/minerals/chlorine-natural-disinfectant.html”www.tandurust.com/minerals/chlorine-natural-disinfectant.html
Trueman, C.N. (March 6, 2015) Poison gas and World War Two. Retrieved from http//www.historylearningsite.co.uk/world-war-two/poison-gas-and-world-war-two