Chlorine

Chlorine is a halogen gas with the atomic number 17 in the periodic table of elements. Its chemical symbol is Cl, the name is taken from the Greek word chloros = yellow-green. It is a yellow-green, strong and pungent smelling gas and is the 11th most common element in the earth's crust. It was first produced in 1774 by the Stralsund-born chemist Carl Wilhelm Scheele (1742-1786) by the action of hydrochloric acid on manganese dioxide, but it was not until 1810 that the elemental nature of chlorine was recognized by the English chemist Sir Humphry Davy (1778-1829). Chlorine is practically non-existent in elemental form, it is mainly found in seawater or in numerous salt deposits as sodium or potassium chloride. Chlorine is used in many different ways in technology. A number of products and uses are briefly mentioned: hydrochloric acid, iron chloride, potassium sodium chloride, chlorobenzenes, chlorinated water (0.4-0.5%), chlorinated lime, silver chloride, phosgene, polyvinyl chloride (PVC), chlorinated hydrocarbons (CFCs), which are now banned due to their harmful effects on the ozone layer, and chloroform. Chlorine is also used as a disinfectant for drinking water and swimming pools and as a bleaching agent (paper, textiles). In the body, it is found as chloride, i.e. in combination with other elements. Sodium chloride (table salt) is the most common and best-known compound. Pure chlorine, which is found in the air in a concentration of more than approx. 0.5%, is already lethal to humans. And even concentrations of 0.001% chlorine in the air we breathe have initial pathological effects, particularly on the respiratory tract. The MAK value (maximum workplace concentration) is 1.5 mg per cubic meter of air. For those who are particularly interested, it should be mentioned that chlorine gas was used as a poison gas near the town of Ypres in Flanders during the First World War (1914-1918), resulting in many deaths and numerous soldiers, some with lifelong injuries.

Functions in the body

Together with sodium, chloride is responsible for fluid distribution and osmotic pressure in the body. Chloride is also a component of stomach acid. Like sodium, chloride is mainly found in fluids outside the body cells, for example in the blood fluid, but not in the blood cells. There it regulates the flow of fluid between the cells (osmosis). Chloride is also important for maintaining the acid-base balance. In the stomach, chloride forms stomach acid (hydrochloric acid) together with hydrogen. This acid is produced in the parietal cells of the stomach. It plays a decisive role in the breakdown of food proteins. Chlorine and sodium are also responsible for the formation and transmission of nerve impulses.

Foods containing chlorine

The main intake of chlorine is through the consumption of table salt (common salt) from industrially produced foods and through salting at home. Around half of our daily salt intake comes from bread and baked goods, and around 30 percent from meat and sausage products. Cured and smoked meat products, salted and smoked fish, many canned foods and ready meals, cheese and cheese cookies, potato chips and salted nuts are particularly high in salt. In contrast, fruit and vegetables, pulses, unsalted nuts and vegetable oils are low in chlorine. Many German water supply companies do not chlorinate their drinking water at all. However, the option of very rapid chlorination is still available for emergencies. In the Federal Republic of Germany, the maximum permissible concentration of chlorine (and other substances) in drinking water is regulated by the Drinking Water Ordinance, which came into force on January 1, 2003. In § 11 of the ordinance, the Federal Environment Agency is tasked with publishing a corresponding list of the various substances with their limit values. According to this "List of treatment substances and disinfection processes in accordance with § 11 Drinking Water Ordinance", the maximum permitted concentration of free chlorine in drinking water is 0.3 mg per liter. As chlorine combines with various substances in drinking water, especially to form trichloromethanes, a limit value has also been set for these combined chlorides. Measured at the consumer's tap, it is 50 µg per liter of water.

Deficiency symptoms

A chloride deficiency is rare. Persistent vomiting or severe diarrhea can lead to a loss of stomach acid, especially if a low-chloride diet is consumed. Heavy sweating can also lead to a lack of chloride. Chloride deficiency leads to disturbances in the body's acid-base balance (alkalosis), which can be associated with shallow breathing, muscle cramps and cardiac dysfunction. The symptoms are similar to those of sodium deficiency.

Overdose

Food contains a large amount of chloride in the form of table salt. Due to this and many other salt-containing foods, the chloride intake of most people in western industrialized countries is therefore far in excess of their requirements. Excess chloride is generally excreted in the urine and through sweating. However, high salt consumption (sodium chloride) can lead to or increase high blood pressure in some people. However, an overdose via drinking water is not to be feared. This is partly due to the low limit of 0.3 mg of free chlorine per liter of water, but mainly because most water suppliers do not (or no longer) chlorinate drinking water.

Demand

The German Nutrition Society (DGE) estimates the minimum requirement of chloride for adults to be around 830 mg per day. On a molecular basis, this corresponds exactly to the sodium requirement. When sweating heavily, sodium and chloride requirements increase proportionally.

Requirements for sport

A dosage of 3 to 5g per day via food is absolutely sufficient.