The simplest chlorine compound is hydrogen chloride, HCl, a major chemical in industry as well as in the laboratory, both as a gas and dissolved in water as hydrochloric acid. It is often produced by burning hydrogen gas in chlorine gas, or as a byproduct of chlorinating hydrocarbons. Another approach is to treat sodium chloride with concentrated sulfuric acid to produce hydrochloric acid, also known as the "salt-cake" process: [42] NaCl + H 2SO 4 150°C ⟶ NaHSO 4 + HCl NaCl + NaHSO 4 540–600°C ⟶ Na 2SO 4 + HCl The right amount to add varies by product. In general, you’ll need to add about 4 pounds (1.8 kg) of cyuranic acid per 10,000 gallons (38,000 L) of water to reach a level of 10 ppm. It’s recommended to maintain a cyuranic acid level around 50 ppm.

Chodos, Alan (ed.). "This Month in Physics History September 4, 1821 and August 29, 1831: Faraday and Electromagnetism". American Physical Society. Archived from the original on June 15, 2010 . Retrieved 2010-05-08. Magnetic susceptibility of the elements and inorganic compounds, in Lide, D. R., ed. (2005). CRC Handbook of Chemistry and Physics (86thed.). Boca Raton (FL): CRC Press. ISBN 0-8493-0486-5. Now, just follow the manufacturer’s instructions for how much to add to bring it up to your desired level. If you’re still a little confused, you can use an online chlorine calculator to help you with the math. Liquid chlorine vs powder chlorineand 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] This reaction is conducted in the oxidising solvent arsenic pentafluoride. The trichloride anion, [Cl 3] −, has also been characterised; it is analogous to triiodide. [47] Chlorine fluorides Staff (29 July 2004). "On the Western Front, Ypres 1915". Veteran Affairs Canada. Archived from the original on 6 December 2008 . Retrieved 2008-04-08. O'Connor J. J.; Robertson E. F. "Michael Faraday". School of Mathematics and Statistics, University of St Andrews, Scotland. Archived from the original on 2010-02-20 . Retrieved 2010-05-08.

Snelders, H. A. M. (1971). "J. S. C. Schweigger: His Romanticism and His Crystal Electrical Theory of Matter". Isis. 62 (3): 328–38. doi: 10.1086/350763. JSTOR 229946. S2CID 170337569. Chlorine is detectable with measuring devices in concentrations as low as 0.2 parts per million (ppm), and by smell at 3ppm. Coughing and vomiting may occur at 30ppm and lung damage at 60ppm. About 1000ppm can be fatal after a few deep breaths of the gas. [14] The IDLH (immediately dangerous to life and health) concentration is 10ppm. [113] Breathing lower concentrations can aggravate the respiratory system and exposure to the gas can irritate the eyes. [114] When chlorine is inhaled at concentrations greater than 30ppm, it reacts with water within the lungs, producing hydrochloric acid (HCl) and hypochlorous acid (HOCl). Elemental chlorine is commercially produced from brine by electrolysis, predominantly in the chlor-alkali process. The high oxidising potential of elemental chlorine led to the development of commercial bleaches and disinfectants, and a reagent for many processes in the chemical industry. Chlorine is used in the manufacture of a wide range of consumer products, about two-thirds of them organic chemicals such as polyvinyl chloride (PVC), many intermediates for the production of plastics, and other end products which do not contain the element. As a common disinfectant, elemental chlorine and chlorine-generating compounds are used more directly in swimming pools to keep them sanitary. Elemental chlorine at high concentration is extremely dangerous, and poisonous to most living organisms. As a chemical warfare agent, chlorine was first used in World WarI as a poison gas weapon.

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. 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] − Chlorine perchlorate (ClOClO 3) is a pale yellow liquid that is less stable than ClO 2 and decomposes at room temperature to form chlorine, oxygen, and dichlorine hexoxide (Cl 2O 6). [53] Chlorine perchlorate may also be considered a chlorine derivative of perchloric acid (HOClO 3), similar to the thermally unstable chlorine derivatives of other oxoacids: examples include chlorine nitrate (ClONO 2, vigorously reactive and explosive), and chlorine fluorosulfate (ClOSO 2F, more stable but still moisture-sensitive and highly reactive). [54] Dichlorine hexoxide is a dark-red liquid that freezes to form a solid which turns yellow at −180°C: it is usually made by reaction of chlorine dioxide with oxygen. Despite attempts to rationalise it as the dimer of ClO 3, it reacts more as though it were chloryl perchlorate, [ClO 2] +[ClO 4] −, which has been confirmed to be the correct structure of the solid. It hydrolyses in water to give a mixture of chloric and perchloric acids: the analogous reaction with anhydrous hydrogen fluoride does not proceed to completion. [53]