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 −

Smil, Vaclav (2000). Enriching the Earth: Fritz Haber, Carl Bosch, and the Transformation of World Food Production. MIT Press. p.226. ISBN 978-0-262-69313-4. Archived from the original on 2015-12-31. What's in your Water?: Disinfectants Create Toxic By-products". ACES News. College of Agricultural, Consumer and Environmental Sciences – University of Illinois at Urbana-Champaign. 2009-03-31. Archived from the original on 2014-09-03 . Retrieved 2009-03-31. 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. Greenwood, Norman N.; Earnshaw, Alan (1997). Chemistry of the Elements (2nded.). Butterworth-Heinemann. ISBN 978-0-08-037941-8. Combined chlorine is the combination of organic nitrogen compounds and chloramines, which are produced as a result of the reaction between chlorine and ammonia. Chloramines are not as effective at disinfecting water as free chlorine due to a lower oxidation potential. Due to the creation of chloramines instead of free chlorine, ammonia is not desired product in the water treatment process in the beginning, but may be added at the end of treatment to create chloramines as a secondary disinfectant, which remains in the system longer than chlorine, ensuring clean drinking water throughout the distribution system.

What Is Chlorine?

Redox systems measure the oxidizing properties of any sanitizer (chlorine) present in the water and are ideal for domestic pools. In simple terms they measure the oxidative power of the pool water and so provide a qualitative estimate of free chlorine which provides a good indication of how water quality has been affected by bather pollution. When chlorine is free to oxidize, sensors generate a millivolt reading, expressed as the oxygen reduction potential (ORP) and the controller responds to the level of voltage generated. The chlorine oxides are well-studied in spite of their instability (all of them are endothermic compounds). They are important because they are produced when chlorofluorocarbons undergo photolysis in the upper atmosphere and cause the destruction of the ozone layer. None of them can be made from directly reacting the elements. [53] There are a few types of powder chlorine: di-chlor, lithium hypochlorite, and calcium hypochlorite. Gribble, G. W. (1994). "The Natural production of chlorinated compounds". Environmental Science and Technology. 28 (7): 310A–319A. Bibcode: 1994EnST...28..310G. doi: 10.1021/es00056a712. PMID 22662801.

Chlorine 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 − If the pool has a UV Cell, the chlorine levels can be reduced to about the same level (0.8 - 1.0 ppm) as the water from your tap (0.5-0.8ppm) It’s also a good product to use for a daily treatment during times of heavy use. How to use liquid chlorine for your poolRezayat, C.; Widmann, W. D.; Hardy, M. A. (2006). "Henry Drysdale Dakin: More Than His Solution". Current Surgery. 63 (3): 194–96. doi: 10.1016/j.cursur.2006.04.009. PMID 16757372. The earliest salt production in the world: an early Neolithic exploitation in Poiana Slatinei-Lunca, Romania". Archived from the original on April 30, 2011 . Retrieved 2008-07-10. Common chemical theory at that time held that an acid is a compound that contains oxygen (remnants of this survive in the German and Dutch names of oxygen: sauerstoff or zuurstof, both translating into English as acid substance), so a number of chemists, including Claude Berthollet, suggested that Scheele's dephlogisticated muriatic acid air must be a combination of oxygen and the yet undiscovered element, muriaticum. [15] [16]

Chlorine is too reactive to occur as the free element in nature but is very abundant in the form of its chloride salts. It is the twenty-first most abundant element in Earth's crust and makes up 126 parts per million of it, through the large deposits of chloride minerals, especially sodium chloride, that have been evaporated from water bodies. All of these pale in comparison to the reserves of chloride ions in seawater: smaller amounts at higher concentrations occur in some inland seas and underground brine wells, such as the Great Salt Lake in Utah and the Dead Sea in Israel. [64] Chloramines & Pool Operation". Centres for Disease Control and Prevention . Retrieved 13 March 2022. Perhaps the most famous application of Labarraque's chlorine and chemical base solutions was in 1847, when Ignaz Semmelweis used chlorine-water (chlorine dissolved in pure water, which was cheaper than chlorinated lime solutions) to disinfect the hands of Austrian doctors, which Semmelweis noticed still carried the stench of decomposition from the dissection rooms to the patient examination rooms. Long before the germ theory of disease, Semmelweis theorized that "cadaveric particles" were transmitting decay from fresh medical cadavers to living patients, and he used the well-known "Labarraque's solutions" as the only known method to remove the smell of decay and tissue decomposition (which he found that soap did not). The solutions proved to be far more effective antiseptics than soap (Semmelweis was also aware of their greater efficacy, but not the reason), and this resulted in Semmelweis's celebrated success in stopping the transmission of childbed fever ("puerperal fever") in the maternity wards of Vienna General Hospital in Austria in 1847. [82] Helmont, Johannes (Joan) Baptista Van, Encyclopedia.Com: "Others were chlorine gas from the reaction of nitric acid and sal ammoniac; … "

Around 900, the authors of the Arabic writings attributed to Jabir ibn Hayyan (Latin: Geber) and the Persian physician and alchemist Abu Bakr al-Razi ( c. 865–925, Latin: Rhazes) were experimenting with sal ammoniac ( ammonium chloride), which when it was distilled together with vitriol (hydrated sulfates of various metals) produced hydrogen chloride. [7] However, it appears that in these early experiments with chloride salts, the gaseous products were discarded, and hydrogen chloride may have been produced many times before it was discovered that it can be put to chemical use. [8] One of the first such uses was the synthesis of mercury(II) chloride (corrosive sublimate), whose production from the heating of mercury either with alum and ammonium chloride or with vitriol and sodium chloride was first described in the De aluminibus et salibus ("On Alums and Salts", an eleventh- or twelfth century Arabic text falsely attributed to Abu Bakr al-Razi and translated into Latin in the second half of the twelfth century by Gerard of Cremona, 1144–1187). [9] Another important development was the discovery by pseudo-Geber (in the De inventione veritatis, "On the Discovery of Truth", after c. 1300) that by adding ammonium chloride to nitric acid, a strong solvent capable of dissolving gold (i.e., aqua regia) could be produced. [10] Although aqua regia is an unstable mixture that continually gives off fumes containing free chlorine gas, this chlorine gas appears to have been ignored until c. 1630, when its nature as a separate gaseous substance was recognised by the Brabantian chemist and physician Jan Baptist van Helmont. [11] [en 1] Carl Wilhelm Scheele, discoverer of chlorine Isolation van Helmont, Joannis Baptistae (1682). Opera omnia [All Works] (in Latin). Frankfurt-am-Main, (Germany): Johann Just Erythropel. From "Complexionum atque mistionum elementalium figmentum." (Formation of combinations and of mixtures of elements), §37, p. 105: "Accipe salis petrae, vitrioli, & alumnis partes aequas: exsiccato singula, & connexis simul, distilla aquam. Quae nil aliud est, quam merum sal volatile. Hujus accipe uncias quatuor, salis armeniaci unciam junge, in forti vitro, alembico, per caementum (ex cera, colophonia, & vitri pulverre) calidissime affusum, firmato; mox, etiam in frigore, Gas excitatur, & vas, utut forte, dissilit cum fragore." (Take equal parts of saltpeter [i.e., sodium nitrate], vitriol [i.e., concentrated sulfuric acid], and alum: dry each and combine simultaneously; distill off the water [i.e., liquid]. That [distillate] is nothing else than pure volatile salt [i.e., spirit of nitre, nitric acid]. Take four ounces of this [viz, nitric acid], add one ounce of Armenian salt [i.e., ammonium chloride], [place it] in a strong glass alembic sealed by cement ([made] from wax, rosin, and powdered glass) [that has been] poured very hot; soon, even in the cold, gas is stimulated, and the vessel, however strong, bursts into fragments.) From "De Flatibus" (On gases), p. 408: "Sal armeniacus enim, & aqua chrysulca, quae singula per se distillari, possunt, & pati calorem: sin autem jungantur, & intepescant, non possunt non, quin statim in Gas sylvestre, sive incoercibilem flatum transmutentur." (Truly Armenian salt [i.e., ammonium chloride] and nitric acid, each of which can be distilled by itself, and submitted to heat; but if, on the other hand, they be combined and become warm, they cannot but be changed immediately into carbon dioxide [note: van Helmont's identification of the gas is mistaken] or an incondensable gas.) But keeping it within healthy levels is simply a matter of testing your water regularly and adding chlorine only when necessary. 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] −