a b c d e "17 Chlorine". Elements.vanderkrogt.net. Archived from the original on 2010-01-23 . Retrieved 2008-09-12. Chlorine forms four oxoacids: hypochlorous acid (HOCl), chlorous acid (HOClO), chloric acid (HOClO 2), and perchloric acid (HOClO 3). As can be seen from the redox potentials given in the adjacent table, chlorine is much more stable towards disproportionation in acidic solutions than in alkaline solutions: [41] Cl 2 + H 2O Blood (Serum) Chloride Level Test". Archived from the original on 31 March 2009 . Retrieved 30 April 2010. The three fluorides of chlorine form a subset of the interhalogen compounds, all of which are diamagnetic. [47] Some cationic and anionic derivatives are known, such as ClF − Ihde, Aaron John (1984). The development of modern chemistry. Courier Dover Publications. p.158. ISBN 978-0-486-64235-2.

Chlorine is a chemical element with the symbol Cl and atomic number 17. The second-lightest of the halogens, it appears between fluorine and bromine in the periodic table and its properties are mostly intermediate between them. Chlorine is a yellow-green gas at room temperature. It is an extremely reactive element and a strong oxidising agent: among the elements, it has the highest electron affinity and the third-highest electronegativity on the revised Pauling scale, behind only oxygen and fluorine. Of the two, hypochlorous acid is the most effective. The amount of each compound present in the water is dependent on the pH level of the water prior to addition of chlorine. At lower pH levels, the hypochlorous acid will dominate. The combination of hypochlorous acid and hypochlorite ions makes up what is called ‘free chorine.’ Free chlorine has a high oxChlorine dioxide (ClO 2) was the first chlorine oxide to be discovered in 1811 by Humphry Davy. It is a yellow paramagnetic gas (deep-red as a solid or liquid), as expected from its having an odd number of electrons: it is stable towards dimerisation due to the delocalisation of the unpaired electron. It explodes above −40°C as a liquid and under pressure as a gas and therefore must be made at low concentrations for wood-pulp bleaching and water treatment. It is usually prepared by reducing a chlorate as follows: [53] ClO − Although dichlorine is a strong oxidising agent with a high first ionisation energy, it may be oxidised under extreme conditions to form the [Cl 2] + cation. This is very unstable and has only been characterised by its electronic band spectrum when produced in a low-pressure discharge tube. The yellow [Cl 3] + cation is more stable and may be produced as follows: [46] Cl 2 + ClF + AsF 5 −78 °C ⟶ [Cl 3] +[AsF 6] − Wisniak, Jaime (2009) "Carl Wilhelm Scheele," Revista CENIC Ciencias Químicas, 40 (3): 165–73; see p. 168: "Early in the seventeenth century Johannes Baptiste van Helmont (1579–1644) mentioned that when sal marin (sodium chloride) or sal ammoniacus and aqua chrysulca (nitric acid) were mixed together, a flatus incoercible (non-condensable gas) was evolved." In the Deacon process, hydrogen chloride recovered from the production of organochlorine compounds is recovered as chlorine. The process relies on oxidation using oxygen:

This relies on 24/7 running of the pool pump to ensure that every cubic metre of pool water passes through the UV cell at least 4 times in every 24 hours. and Cl 2F +. [48] Some pseudohalides of chlorine are also known, such as cyanogen chloride (ClCN, linear), chlorine cyanate (ClNCO), chlorine thiocyanate (ClSCN, unlike its oxygen counterpart), and chlorine azide (ClN 3). [47] Most products you buy will be for about 10,000 gallons of pool water, so if your pool is larger than that, you will need more product.

Many organochlorine compounds have been isolated from natural sources ranging from bacteria to humans. [57] [58] Chlorinated organic compounds are found in nearly every class of biomolecules including alkaloids, terpenes, amino acids, flavonoids, steroids, and fatty acids. [57] [59] Organochlorides, including dioxins, are produced in the high temperature environment of forest fires, and dioxins have been found in the preserved ashes of lightning-ignited fires that predate synthetic dioxins. [60] In addition, a variety of simple chlorinated hydrocarbons including dichloromethane, chloroform, and carbon tetrachloride have been isolated from marine algae. [61] A majority of the chloromethane in the environment is produced naturally by biological decomposition, forest fires, and volcanoes. [62] The chloride anion is an essential nutrient for metabolism. Chlorine is needed for the production of hydrochloric acid in the stomach and in cellular pump functions. [104] The main dietary source is table salt, or sodium chloride. Overly low or high concentrations of chloride in the blood are examples of electrolyte disturbances. Hypochloremia (having too little chloride) rarely occurs in the absence of other abnormalities. It is sometimes associated with hypoventilation. [105] It can be associated with chronic respiratory acidosis. [106] Hyperchloremia (having too much chloride) usually does not produce symptoms. When symptoms do occur, they tend to resemble those of hypernatremia (having too much sodium). Reduction in blood chloride leads to cerebral dehydration; symptoms are most often caused by rapid rehydration which results in cerebral edema. Hyperchloremia can affect oxygen transport. [107] Hazards Chlorine Microorganisms can be found in raw water from rivers, lakes and groundwater. While not all microorganisms are harmful to human health, there are some that may cause diseases in humans. These are called pathogens. Pathogens present in water can be transmitted through a drinking water distribution system, causing waterborne disease in those who consume it.