Talk:Chlorine/Archive 1

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Article changed over to new WikiProject Elements format by maveric149. Elementbox converted 10:59, 23 Jun 2005 by Femto (previous revision was that of 05:25, 23 Jun 2005).

Chlorine safety
I was just having a read. It is worth noting that chloride ions are used by the body to regulate mucus thickness in our lungs. As the ion concentration increases, our lungs begin diluting the mucus. Chlorine is known to cause pulmonary edema (water on the lungs / drowning - a problem seen in patients who have inhaled a dangerous quantity of the gas), and this is aided by chloride donors, like chlorine and hydrogen chloride, 'tricking' the body into thinking more and more water needs to go into the mucus. The opposite is true of people with cystic fibrosis, who suffer from mucus that is too thick and which clogs their airways. —Preceding unsigned comment added by 109.156.92.39 (talk) 22:40, 14 January 2011 (UTC)

Information Sources
Some of the text in this entry was rewritten from T7.html Los Alamos National Laboratory - Chlorine. Additional text was taken directly from, USGS Periodic Table - Chlorine, from the Elements database 20001107 (via dict.org), Webster's Revised Unabridged Dictionary (1913) (via dict.org) and WordNet (r) 1.7 (via dict.org). Data for the table was obtained from the sources listed on the main page and WikiProject Elements but was reformatted and converted into SI units. --

Gas image
I noted the comment "gas, doesn't look like much" with the picture provided. The best pictures I've seen of chlorine are from leaking railroad cars. See http://www.hazmat101.com/, click on the 'files' link in the colored bar at the top and look at the power point file in the November 2003 section titled "Rail tank car chlorine leak photos". The last slide is especially good - the yellow-green color is particularly good. Also note the gas hanging to the ground and not pluming into the air.swc 21:30, 4 October 2005 (UTC)

I can check with my employer about getting a good photo in the lab of both liquid and gas phases.


 * Impressive photos are always good, so do if you can. But Chlorine it's self isn't all that colourful or dramatic as a gas. I think most expect to see a comic book style, thick, green cloud; I expected it to be more green and solid in colour before using it the first time. In reality, the photo is dead on; it's quite pale yellow with a green tinge, even in high concentrations. — Preceding unsigned comment added by 109.149.155.12 (talk) 13:35, 26 June 2011 (UTC)

Chlorine-36
The Cl-36 (36Cl) info at has several differences from that in. (SEWilco 07:18, 12 May 2005 (UTC))

Subsurface production by muon capture of 40-Ca? Where do the muons come from in such scenario? --Shaddack 18:44, 23 November 2005 (UTC)


 * Muons are generated in the atmosphere due to reactions between cosmic rays and air molecules. Muons have a relatively low interaction cross section with matter and can penetrate quite deeply. Many underground neutrino detectors count only neutrinos coming from below (and thus having passed through a few thousand km of Earth) because there is too much muon background from above. Icek 19:40, 24 March 2007 (UTC)

although people don't know it ,but when chlorine is unleashed it distorts the ozone layer. for more info or that didn't answer your q email me at email address removed —Preceding unsigned comment added by 24.180.201.93 (talk) 14:33, 12 May 2008 (UTC)

Chlorine + Alcohol = Explosion?
Is this true? --Arima 02:03, 25 November 2005 (UTC)
 * Well, chlorine is a powerful oxidizing agent, and alcohol burns in an oxygen atmosphere, so I see no reason why it wouldn't burn in a chlorine atmosphere. I suppose you'd get alcohol to explode in chlorine the same way you'd get it to explode in oxygen: mix alcohol vapor or aerosolized alcohol with pure chlorine gas, then provide an ignition source.  The required temperature might be low enough for spontaneous ignition at room temperature, but I don't know.  --Carnildo 19:14, 25 November 2005 (UTC)


 * You might be referring to that (in)famous video where some young idiots have a plastic bottle in which they "add the chlorine to the alcohol" and "shake it up hella good" (and nearly kill themselves with the resulting explosion, it looks like). However, what they're probably using is the kind of so-called "chlorine" used in pools as disinfectant, which is actually sodium hypochlorite. And it does seem to explode pretty well. --Bob Mellish 19:38, 25 November 2005 (UTC)


 * (Note: edited my comment above to change sodium hyprochlorite to calcium hypochlorite, with the comment "Re-Corrected by SINYpyro."
 * 1) Please don't change other people's comments on talk pages.
 * 2) There are a number of bleach-type compounds commonly but incorrectly called "chlorine", including both calcium and sodium hypochlorite. --Bob Mellish 17:13, 13 March 2006 (UTC)


 * I'ts sad how many people there are out there who change what people have written. I feel for you. --Ruff 04:06, 28 July 2006 (UTC)


 * From the video, it appears to be some sort of pressure explosion, not combustion. Anyone know what the reaction/gas produced is?


 * I have a feeling that it is hydrazine, but I'm not in the least sure. Ruff Bark away!  20:59, 25 August 2006 (UTC)

Hydrazine is unlikely because there was no nitrogen compound involved in the experiment. 151.197.54.195 16:10, 24 February 2007 (UTC)
 * Hydrazine is definately believable, a friend and I have been messing around with chlorine/alcohol quite a bit lately, and the resulting gas is highly flammable (like rocket fuel =]) I can also verify that it causes an explosion, but only because of the release of the gas, and I think it's a similar reaction to the chlorine/ammonia one that produces hydrazine.

Looks like references are the order of the day here?
It seems to me the first task for the collaboration is references. I can see about asking my Chemistry teacher if he knows any good, you know, chemistry books that'll have a bunch of detail on Chlorine, because they'll probably just repeat what's already in this article yet it'll certainly go a long way. However, thinking about Chlorine, could not the more social aspects of chlorine be emphasized, you know, maybe a picture of a pool with chlorine used to keep it clean, more detail on how chlorine was sometimes used in gas form as a weapon of war in WW1 if I remember correctly, etc. etc., all that stuff kind of is notable for Chlorine after all. Homestarmy 21:36, 1 May 2006 (UTC)


 * I added some information about chlorine and WWI from the Use of poison gas in World War I article. It has an OK amount of info but there is still a long way to go. As a suggestion I think we should model it after some of these articles: Acetic acid Helium, Hydrochloric acid, Technetium. Tarret 00:31, 2 May 2006 (UTC)

Safety (a.o.)
This is an article about an important element, chlorine. It has been rated A-class. But it has accumulated much information which is anecdotal (mainly concerning safety, but also about external organizations/suppliers). As was done with aniline, hydrazine and hydrogen sulfide, much of that infomation has been removed, or compacted into one or two sentences. For more safety data one can consult an MSDS sheet. --Dirk Beetstra T C 22:15, 13 August 2006 (UTC)

Diaphragm cell electrolysis
The following request was placed on the main page by user 72.27.87.149 (talk) at 00:50, 6 February 2007. I'm moving it to the talk page (see below). Karl Hahn (T) (C) 13:57, 11 February 2007 (UTC)


 * Please give step by step method for this extraction process

1) The starting material is saturated brine (salt = NaCl solution), sometimes obtained by drilling a well into an underground salt dome and circulating water through this well. Ca and Mg contaminations are removed by precipitation with sodium carbonate. The brine is fed into the anode compartment of the cell, where chloride ions release the extra electron to the anode and are converted to chlorine gas. Anode and cathode compartment are separated by an asbestos diaphragm, which is formed directly on the wire screen cathode by a paper making technique (pulp of asbestos slurried in water and filtered on the cathode screen). It has the consistency of several layers of wet paper towels. By pumping brine into the anode compartment, the liquid level there is raised 10 to 30 cm above the level of the catholyte, causing a slow percolation of brine / anolyte through the diaphragm. Masstransport is both hydraulic and electric driven : Most important is that the hydraulic flow (percolation) should be enough to prevent the electricly driven transport of OH- ions from reaching the anode compartment, where they would cause side reactions (hypochlorite formation). Both driving forces for Na+ ions are in the same direction (toward the cathode); for Cl- ions it is in opposite directions (i.e. electric potential pulls Cl- toward the anode), but percolation is predominant, resulting in a catholyte containing 10 % NaOH plus 16 % unreacted NaCl. Cathode reaction is decomposition of water into hydrogen gas and OH- ions. The OH- ions together with Na+ ions coming through the diaphragm form NaOH. As the catholyte is evaporated, much of the NaCl contaminant precipitates and is recycled. The final product still contains about 1 % NaCl plus some hypochlorite and chlorate, limiting its usefulness.151.197.54.195 16:02, 24 February 2007 (UTC)

Modern use as a Chem. weapon?
Suggest somebody with more time and knowhow than I look into this. http://news.yahoo.com/s/ap/20070221/ap_on_re_mi_ea/iraq Appears to be the second or third such use of Chlorine gas as a chemical weapon by terrorists/insurgents. —The preceding unsigned comment was added by 71.194.57.200 (talk) 01:38, 22 February 2007 (UTC).

Downgraded article quality
Thoughg this article is good in all other ways I feel that the amount of references is insufficient for thje size of the article and the article should use the cite web citation template. see Argon for more details. 74.116.113.241 18:00, 14 March 2007 (UTC)

Chlorine as a chemical weapon
I've seen the use of chlorine as a chemical weapon has been mentioned in world war I but it needs to be mentioned as separated segment in this article mentioning also the recent use of chlorine during suicide attacks in Iraq (march 17).

thank you Minako-Chan* 20:55, 17 March 2007 (UTC)

B-Class
GA class is not part of project assessment scales, and GAs are not tracked by WP Bot 1.0. The assessment level has been set to B class. --Cryptic C62 · Talk 21:11, 28 March 2007 (UTC)
 * Then why do the templates still take a GA rank assessment? Homestarmy 21:12, 28 March 2007 (UTC)
 * Reverted as per the WP Bot discussions. --Cryptic C62 · Talk 02:55, 13 April 2007 (UTC)

The WP:Chem assessment was the predecessor (actually THE original) of the current widely used assessment. Good Articles have been invented much later, as a qualifier to B-Class, just as FA is to A-Class. Since the Chemicals wikiproject has been about only the core worklist for two years up until recently, we stuck to not using the GA class in our assessment. For the core worklist, we formally still do. Wim van Dorst (Talk)'' 20:15, 14 April 2007 (UTC).

A-Class
This article is of high quality. I propose it for promotion to A-Class on the our WP:Chem A-Class peer review page. Please comment/support. Wim van Dorst (Talk)'' 20:20, 14 April 2007 (UTC).

Yes. I agree. Extremely good for people who want to know about Chlorine. Ian.bjorn (talk) 06:10, 2 October 2010 (UTC)

Industrial Scale Production
I work in such a plant and I am willing to provide as much detail without divulging trade secrets about the operation of such a facility. It is my second attempt at editing here so please edit/rewrite so it looks professional.
 * Actually your contribution is excellent, I read it only a minute or so after you put the first part in. It could use a little bit of wikification, but the meat of the contribution is what counts, and it's spectacular. Trusilver 07:35, 30 June 2007 (UTC)


 * Content is great. But, is it more applicable in chloralkali process rather than here? --Rifleman 82 10:17, 30 June 2007 (UTC)

I also have worked in Chlorine plants using the diaphram process. In your discussion of the uses of Hydrogen Gas you have missed one of ther primary uses of Hydrogen. This off gas is used to fire boilers. The am produced is critical to concentrating the dilute caustic to a marketable 50% strength. —Preceding unsigned comment added by 199.72.78.161 (talk) 15:29, 8 April 2009 (UTC)

Power efficiency
It is stated that "The amount of electrical energy required to produce a given amount of chlorine is fixed by the nature of the electrochemical reaction. Any energy savings, therefore, can only be made by improving the efficiency of the process and reducing ancillary energy use.".

The electrical power efficiency of electrochemical processes is the product of the current and voltage efficiencies and both may be substantially less than unity. The current efficiency may approach unity in many processes but the voltage efficiency will typically be less than unity in industrial processes. The voltage drop has several components (electromotive force, overvoltage, electrolyte resistivity, lead resistivity, contact resistivity etc). Some of these (typically lead resistance and other external drops) may be excluded from the calculation of voltage efficiency and included in the "ancillary losses".

The statement ought to be replaced by information on the typical current and voltage efficiencies and the nature of these losses as well as information on the external (outside the cell) ancillary losses and their causes. —Preceding unsigned comment added by 90.239.71.36 (talk) 09:52, 25 July 2010 (UTC)

Chlorine as a chemical weapon
The sub-headings "World War I" and "Iraq War" seem out of place in the "Applications and uses" section. The use of chlorine as a chemical weapon is already discussed in the "History" section. Perhaps it would be appropriate just to provide links to "World War I" and "Iraq War" under "History" and move the text on these items from "Applications and uses" to the linked articles. Indeed, chemical warfare is hardly a significant application of chlorine nowadays, even if hostile acts involving Cl2 do still occur occasionally. FranklinJ 11:24, 20 August 2007 (UTC)

GA Review
Re-reviewing this article, which was originally reviewed on December 9, 2005, to see if it continues to meet the GA criteria. After a few minor revisions, I believe it continues to meet the criteria, and it will be kept. However, there are a couple of gaps in the referencing and citations (nothing too major), that should be addressed. Inline citations are notably absent from the isotopes section, and the industrial production section. Cheers! Dr. Cash 18:53, 8 September 2007 (UTC)

Chlorine and cancer
A subject for investigation:

Could cholorine in drinking water contribute to the high rate of cancer in our society? I'm told that the EPA says drinking and showering in chlorinated water increases your risk of cancer by a whopping 93%. Is it true? That cancer is an illusive health concern concurrent with the nearly universal use of cholorine to disinfect drinking water may be a cause and effect relationship that has been overlooked, understated, or ignored.

Could there be better ways to disinfect our water supply? As a former backpacker, small amounts of tincture of iodine were used to disinfect water from suspect sources. Since a small amount of iodine is healthy for a functioning thyroid, this could be an improved way to treat our municipal water supplies. Flouride has been added to some drinking water to reduce tooth decay. Why not use it or iodine to disinfect with? If chlorine is causing cancer as alleged and seemingly indicated, this needs attention.

Chemotherapy, radiation treatments, and all else used to combat cancer are not prefered means if cancer can be reduced or controlled by removing chlorine from our water supply.

Al Williams, Oak Harbor, Washington 4.242.141.9 11:49, 10 September 2007 (UTC)

Because both iodine and chlorine are halogens, which are powerful oxidizing agents. Iodine is convenient to carry around as it is a solid but can be made into a solution. Iodine is, relative to chlorine, very uncommon. Iodine compounds (iodides) are very expensive, whereas chlorine compounds (chlorides) are s cheap as evaporating seawater. From there, you run electricity through a solution and generate chlorine gas and lye, which if the vessel is built correctly can be seperated. If allowed to mix, you make bleach. Also, chlorine can evaporate from water while iodine cannot. Large amounts of iodine are not good for you.

Fluorine is the most reactive element. It is added to water as compounds that are not oxidizers. Fluorine gas itself is insanely hazardous to produce, store, and transport. Fluorides are extremely toxic above the trace quantities used to slow tooth decay. Fluorine also reacts with essentially everything including water, turning itself into(non-disinfecting) fluorides and probably rapidly into insoluble calcium and magnesium fluoride. By comparison, chlorine dissolves forming small quantities of hypochlorous acid (powerful disinfecting agent)by dissociation. It tends to form small amounts of chlorinated hydrocarbons like chloroform which are not exactly healthy.

I would like to see where you quoted that statistic from. Has it occured to you that if this were between two populations, it is likely that the one with no chlorine and less cancer was having quite a few deaths and shortened lifespans from contaminated drinking water before the people could develop cancer? It may be a statistic, but it's flawed logic.

Dormroomchemist (talk) 02:18, 1 April 2008 (UTC)

Chlorine portrayed as an evildoer ?
the bad uses of chlorine are put first in this article. i love chlorine, it is my favorite element on the perioidic table except for fluioirine but thats ok, and it is sad that such a great element as Chloioirine gets such a bad name in the first few paragraphs of this article. yes wikipedia is very nice, and i know that, but chlorien is such a great element and this is so sad that it is portrayed as an evildoer in the first few paragraphes of this article. —Preceding unsigned comment added by 161.97.198.122 (talk) 17:04, 1 November 2007 (UTC)

While I have no personal feelings towards the element itself, it does seem to make more sense to focus on its chemistry and physical properties first. I think this article could benefit from some re-ordering of items. —Preceding unsigned comment added by 69.159.212.16 (talk) 14:39, 21 December 2007 (UTC)

I have reordered its use in wars to the "Application" section. It seems more suited here. Hwwever, now the history section seems a little lacking. To any expert on it, it would be appreciated if you would expand this section. —Preceding unsigned comment added by 69.81.137.234 (talk) 00:36, 16 January 2008 (UTC)

valence electrons?
Now you said that Chlorine has 7e-, but im not getting the concept of valence electrons. If Chlorine has 7e- then how many valence electrons do the transition metals have?(If they even have the same number of e-)

68.37.65.33 00:16, 13 November 2007 (UTC)

The number of valence electrons any transition metal has depends on its group number, just count the number of rows over for most of the elements.

Also a confusion of my own, how does a chlorine allergy work, isn't chlorine in small mounts an essential substance in the human body? 24.65.87.238 (talk) 00:57, 10 January 2008 (UTC)

Chlorine allergy?
It seems ridiculous to me that chlorine would be an allergen. Such people could not consume salt at all, and would have no stomach acid. Is it possible that the allergy the article refers to is actually an allergy to Chloramine, which is also commonly used as a disinfectant (but is less corrosive than chlorine)? Scythe33 (talk) 03:39, 2 March 2008 (UTC)

I also question the 'allergen' claim, as chlorine is an essential element for animal life. (Gastic acid and salt). If the claim is related to pure Cl and not HCl or salts, then it's really more an issue of toxicity than allergy.Tysalpha (talk) 15:42, 4 March 2008 (UTC)

Okay... I am not used to adding comments here. But I want to say I was reading this page and saw the bit about the allergy. I once did an allergy test at an hospital and I found out I am allergic to chlorine. This means, according to my personal experience, that I get a stronger response to chlorine (just the gas, ofcourse... not the element or chloride ion in compounds like salt) than most people. Whenever I swim in a swimming pool with chlorine in it, my eyes will get irritated after just an hour or so and breathing gets harder. I also get nauseous from the 'smell' of bleach-like cleaning stuffs. I do not have any problem with drinking or touching tap water. Maybe, tap water doesn't have chlorine in it where I live (Netherlands) or it has so little I don't even feel it, or, the reason I made this comment: this piece on wikipedia might be wrong. - 10 March 2008 —Preceding unsigned comment added by 145.97.222.38 (talk) 19:05, 10 March 2008 (UTC)

Suggest deleting link to 'Computational Chemistry Wiki'
When I visited this site it's a base install of media-wiki with no content and no configuration. It smacks of someone with good intentions putting their site out there as a resource but not following through to make it a site of actual merit that would justify a link in the article. I am not going to remove it myself as it may be that this site is in some sort of server or formate transition and perhaps in the past if has been something of value. I'm commenting so that it might come to the attention of those who would know and make a good judgment call. —Preceding unsigned comment added by 12.216.233.199 (talk) 17:29, 4 April 2008 (UTC)


 * There used to be some good stuff there, but apparently their database crashed or something like that. I don't know how long they've had this problem, but I noticed it a few weeks ago. --Itub (talk) 12:02, 8 April 2008 (UTC)

Economics of Chlorine production
I can't remember where, but I once read that the PVC and other chlorinated products are relatively cheap because chlorine is the unavoidable co-product of NaOH/KOH production, and there is no environmentally safe way to dispose of it other than to turn it into things like PVC and bleach etc. Certainly, water purification is major user of "raw" chlorine gas, but this application doesn't consume enough to keep up with the supply produced as a byproduct of lye production. So chemical companies figured out that they stuff this excess chlorine into plastic (PVC), pesticides (DDT, cyclodienes, etc.), and aromatic (PCBs) and thus created markets for these products. Or at that's the story I've heard. This might be totally wrong, and I can't for the life of me remember where I read this, but it does sound plausable—after all, what are you going to do with all that Cl2 you get as a byproduct of the Chlor-alkali process. Anyone have any info on this? Yilloslime (t) 19:03, 15 May 2008 (UTC)

To do
I have ordered the sections and expanded the history. I have moved all the info of the production into a separate article. Now the production section needs to be trimmed greatly. Nergaal (talk) 17:58, 8 July 2008 (UTC)

Chlorine cracking
The mentioned cracking of Steel is due to chloride not chlorine.
 * Swimming Pool Roof Collapse
 * STRESS CORROSION CRACKING OF STAINLESS STEELS IN SWIMMING POOL BUILDINGS
 * For the polymers (acetal) resigns I have to get a reference.--Stone (talk) 13:54, 10 July 2008 (UTC)
 * gives the facts.--Stone (talk) 14:00, 10 July 2008 (UTC)

There is no citation to support the claim that the acetal fitting crack originated at "injection moulding defects". This is misleading at best when the probable cause is residual stress due to torque applied when making up the pipe connection.12.4.26.248 (talk) 16:15, 10 July 2009 (UTC)

FA Review
Hey guys! I think this article should be submitted for FA review. What do you think? Wii Wiki (talk) 15:12, 10 July 2008 (UTC)


 * That's exactly the plan, but it is not ready yet. Some sections need to be expanded, some contracted, and it needs more references. If all goes well, and thanks to the efforts of Stone and Nergaal, I expect that it will be submitted as a FA candidate sometime this month, but it would be premature to submit it right now. --Itub (talk) 15:16, 10 July 2008 (UTC)

There is a lot todo:


 * Reference for rock salt usage 3000 B.C., I can only finde something about Hallain dating back into iron age 1300 B.C. Salt mining is really underground and not like all other not water soluble ores, where you start at the surface and follow the ore into the underground. --Stone (talk) 17:02, 10 July 2008 (UTC)


 * Let's be productive. I have added a todo template at the beginning of the page. If there is something you notice missing and you don't have the time to do it within a few hours, add it there. Nergaal (talk) 17:57, 10 July 2008 (UTC)

chlorine is in your pools —Preceding unsigned comment added by 206.78.225.15 (talk) 18:15, 14 August 2008 (UTC)


 * Count me in. I originally de-stubed this article and might as well help bring it to FA. --mav (talk) 04:02, 25 August 2008 (UTC)

Chlorine and Thyroid disease
Perhaps there can be some discussion about chlorine and it's effects on the thyroid. It's not often written about, but thyroid disease is increasing in this country. Why? I don't know. It's hard to get answers from physicians, basically they don't know. But I have read about the possibility of the use of chlorine as one of the offenders. It competes with iodine blocking its uptake to the thyroid. Any thoughts? —Preceding unsigned comment added by Navarr16 (talk • contribs) 00:08, 17 September 2008 (UTC)

I don't get this....
-"Along with fluorine, bromine, iodine and astatine, chlorine is a member of the halogen series that forms the group 17 of the periodic table - most reactive group of elements."- I will admit that I don't have a PhD in chemistry, but aren't the Alkali Metals the most reactive elements?545lljkr (talk) 22:35, 1 January 2009 (UTC)

No. Halogens are reactive enough to for diatomic molecules.


 * Alkali metals are reactive in a different way-they are reducing agents. Halogens are oxidizing agents. Fluorine is an extremely powerful oxidizing agent that can ignite methane without a spark! --Chemicalinterest (talk) 19:45, 8 September 2010 (UTC)

Wrong info under history
Under the stuff about hydrochloric acid and aqua regia, it directly contradicts sourced information in Aqua Regia.

Fix this.

--Heero Kirashami (talk) 16:35, 4 January 2009 (UTC)

I see another major problem with this article. It contradicts directly with the article on hydrochloric acid as to who discovered it, how, and when. I do not know which is right, but it should be fixed either way. 208.102.107.81 (talk) 01:04, 17 December 2009 (UTC)

Why no mention of controversy over environmental impacts of industrial uses of Cl?
It's curious to me that the article makes no reference to significant North American and European controversy over the environmental consequences of industrial chlorine chemistry (esp. via inadvertent production of poorly characterized mixtures of persistent organochlorine byproducts and degradation products). The controversy dates to at least the early 1990s. International environmental NGOs have published reports on the subject; the International Joint Commission published a 1992 recommendation for a phase-out of chlorine; Springer published a major treatise on the subject in 1999 ; MIT press published a major treatise on the subject in 2000 ; and I have written a social science doctoral dissertation on the subject. A search of version history turns up nothing. Thoughts? --HowardJeff (talk) 05:19, 21 March 2009 (UTC)

hardness and strength
the brine is tested for hardness and strength. Is the hardness the water hardness (calcium carbonat concentration in water) hard water and the strenght is the concentration of salt in the solution. --Stone (talk) 18:44, 23 April 2009 (UTC)

Biological Role of Chlorine
I think this article needs a "biological role" section. Considering Chlorine's abundance in the human body (9th most abundant, beating out Sodium) and its abundance in the Earth's oceans, isn't it likely that Chlorine has a biological role? Free hydrochloric acid is found in the stomachs of all healthy normal human adults. Eldin raigmore (talk) 17:30, 16 May 2009 (UTC) Also, some research physicians and/or physiologists have said (sorry, I have no references) that, in salt-sensitive hypertension, there's evidence to suggest that perhaps the Chlorine ion has as much importance as the Sodium ion. The articles on many elements do have a "biological role" section; among them, Oxygen, Vanadium, Phosphorus, Sodium, Cobalt, Arsenic, Cadmium, Potassium, and Magnesium. Even the articles about some elements with no known biological role, or whose only known roles are toxic, or of research-value only, or in therapy rather than in normal biochemistry, have such sections. So I think this article needs a "biological role" section. Eldin raigmore (talk) 17:05, 16 May 2009 (UTC)

Hypochlorous acid missing
Please add a link to this page ( http://en.wikipedia.org/wiki/Hypochlorous_acid ) to the section dealing with Compounds / Acids. Thanks. 213.250.246.158 (talk) 19:42, 16 January 2010 (UTC)
 * Added. Materialscientist (talk) 06:38, 17 January 2010 (UTC)

Please remove strikeout from "OX" in NFPA 704...
The NFPA 704 template includes "Other=&lt;s>OX&lt;/s>", which is silly; the symbols are W (reacts badly to water) or OX (is an oxidizer). It should be just "Other=OX". Thanks. 71.41.210.146 (talk) 07:33, 28 January 2010 (UTC)
 * Agreed and changed. Materialscientist (talk) 07:51, 28 January 2010 (UTC)

Monograph info about the chemical....

 * http://md1.csa.com/partners/viewrecord.php?requester=gs&collection=TRD&recid=20070650322609MT&q=allintitle%3A+monograph+food&uid=789086877&setcookie=yes

--222.67.211.208 (talk) 11:56, 2 March 2010 (UTC)
 * http://scholar.google.com/scholar?as_q=Monograph+Chlorine&num=10&btnG=Search+Scholar&as_epq=&as_oq=&as_eq=&as_occt=title&as_sauthors=&as_publication=&as_ylo=&as_yhi=&as_sdt=1.&as_sdtp=on&as_sdts=5&hl=en

History
There is a disagreement as to whether or not Hydrochloric acid was known to the alchemist Jābir ibn Hayyān (Geber) at around 800 AD. The article states: "Hydrochloric acid was probably known to alchemist Jābir ibn Hayyān (Geber) around 800 AD" and this sentence is attributed to the book: ''Pereira, Jonathan (1854). The elements of materia medica and therapeutics, Volume 1. Longman, Brown, Green, and Longmans. p. 387. http://books.google.com/?id=RXEhAAAAYAAJ&pg=RA1-PA387.'' I have done a quick google search and it seems that this statement is backed up by several other sources. However, an editor is persistently removing the reference saying that it is confusing Geber (800 AD) with Pseudo-Geber (1300 AD). Maybe this is true but since I can find information elsewhere that suggests otherwise I think it is better to discuss it here to find out the actual truth before removing anymore valid references. Polyamorph (talk) 11:45, 14 August 2010 (UTC)
 * Given that there are references that refute the above reference, which are cited at the hydrochloric acid article, and given that the inclusion of that particular sentence about history is not critical to the chlorine article even if it were correct, it is appropriate to delete it. The author Materialscientist was the one who originally inserted it. As Materialscientist has a record as a responsible author, and has been active at Wikipedia in recent days, I expect that he will agree with me that his refererence is weak and it's appropriate to delete the sentence. Seanwal111111 (talk) 12:44, 14 August 2010 (UTC)
 * The reference is not weak, it looks like a reliable source to me. The only weakness comes in the fact that author writes "was probably known" which isn't a clear statement of fact. However, you have done nothing to prove it is not true and nothing to validate that your assumption that they are confusing Geber (800 AD) with Pseudo-Geber (1300 AD). Show me a reference that makes this clear and I will be happy to agree with you. The fact that you have removed the reference again despite this talk only shows you wish to participate in an edit war rather than discuss the true validity of the statement. I see that hydrochloric acid cites those references but occasionally wikipedia articles do contradict each other. Citing that article as being more accurate than this one is not a valid argument. Google "history of hydrochloric acid" and you will find references that back up both stories. I'm not an expert on the history so cannot comment on which one is more accurate without performing further research. But I do know that it is better to settle disagreements in talk space rather than article space. Also I did not know that materialscientist added the link but the fact that they did only reinforces in my mind that the reference is valid. Polyamorph (talk) 16:56, 14 August 2010 (UTC)
 * Also the reference that you seem to like (Ladislao Reti Chymia, Vol. 10, (1965), pp. 11) is not exactly definitive stating "Partington thinks that it was apparently unknown until the sixteen century" - another way of saying they don't know...Polyamorph (talk) 17:03, 14 August 2010 (UTC)
 * Also you are happy to keep the cited statement "Before 1400 AD, aqua regia, a mixture of nitric acid and hydrochloric acid, began to be used to dissolve gold" in the article. So hydrochloric MUST have been known before the 16th century. Either that or this reference is also incorrect? No I don't think it is, I think it is more you are trying to push your POV by removing valid references which is wrong. Polyamorph (talk) 17:41, 14 August 2010 (UTC)
 * There is honest and historic confusion about Jabir/Geber in 1854 it was widely believed that all the works were from the same hand. However this is no longer the case. This is a good source for info on the mineral acids(I have some others on the historic confusion) Aqua regia was not made by mixing acids. Forbes deals with "scientific" discovery ( that is; making it on purpose, publishing the results, and that it is repeatable by others) as well as "alchemical" efforts. I am glad that some one else is interested in this. J8079s (talk) 20:07, 14 August 2010 (UTC)
 * As much as I respect your view and your appreciation of the confusion that might have been in place in 1854, can we discuss the point regarding the accuracy of the reference in question that has been deleted from this article and the subsequent 2003 citation within this article that suggests hydrochloric acid was known prior to the 16th century? I'm sure that there was an historic confusion but does that really mean the Pereira 1854 citation and the Hoover 2003 citations are incorrect? Was hydrochloric acid unknown before the 16th century? If not, references should not be deleted willy nilly just to push POV. Polyamorph (talk) 20:33, 14 August 2010 (UTC)
 * (1)The method by which Pseudo-Geber obtained aqua regia is described at . It was by adding salammoniac to a distillate of vitriol. He didn't possess hydrochloric acid; he possessed aqua regia.
 * (2)The book 260-page book The Works of Geber is viewable online at . A search of the book's text for the word "hydrochloric" turns up zero results.
 * (3) The book 600-page book A history of chemistry from the earliest times by James Campbell Brown (1920, downloadable) contains the word "Geber" on 29 different pages and the word "hydrochloric" on 28 different pages. But the two words never appear in connection with one another. One of the reasons why "Geber" crops up on 29 different pages is that when a particular chemical under historical discussion was known to Geber, the author likes to mention that historical fact. The book History of analytical chemistry by Ferenc Szabadváry (books.google.com previewable) has the word "hydrochloric" on 73 different pages and the word "Geber" on 7 different pages. Once again, there's no connection reported.
 * (4)The expert article at http://www.jstor.org/pss/27757245 says "Concerning hydrochloric acid all historians are agreed that we have no clear reference to its preparation in the Middle Ages, and that its discovery was not till the end of the 16th century." That article is specifically dedicated to the topic of the history of hydrochloric acid. It totally trumps a passing comment by a non-expert writing way back in the year 1854 -- non-expert because he's writing about medicine not chemistry in book The elements of materia medica and therapeutics.
 * (5)Repeating myself from earlier, it is completely harmless to the chlorine article to delete the sentence that hydrochloric acid was problably known to Jābir or Pseudo-Geber, even if the sentence is true. The reason to delete it is that it is very likely a falsehood. Seanwal111111 (talk) 21:51, 14 August 2010 (UTC)
 * I disagree that if the sentence is true that it would not worthy of inclusion, the first known use of a substance is a certainly notable. But since there is no strong evidence that the Pereira (1854) reference is true and there is not at this time an alternative reliable citation then I think you are correct that it should not be included at this time. Polyamorph (talk) 07:02, 15 August 2010 (UTC)

Sorry for belated reply. The arguments of Seanwal111111 can be beaten with wikipedia policies (NPOV, include all views, what is WP:RS and what is not, we should not interpret the sources, etc., etc.) but frankly I am not keen to commit my time to that, even though I added that reference. The main reason is that the original writings (or what we think they are) of Geber are so obscure that I do not believe their interpretation can be conclusive in this matter. Materialscientist (talk) 07:20, 15 August 2010 (UTC)
 * This particular reference (which does meet WP:RS does seem to suggest Hydrochloric acid was known to Geber in the year 800. And there are plenty of other sources that come up if you perform a simple google search. It seems that there are conflicting views. To be perfectly neutral we should state that some sources attribute the discovery of Hydrochloric acid to Geber in 800 AD and other sources suggest it was first known from the 15th to the 16th century. i.e. I think we should present both cases. As such I have striked out my comment above. Polyamorph (talk) 11:28, 15 August 2010 (UTC)
 * Well, if you are up to this task .. The article to start with is hydrochloric acid, where references to Geber were deleted by Knight1993 on 21/22 June 2010. I believe the pseudo-Geber story is important (i.e. that one should separate the original Arabic sources of Geber and the Latin books which are attributed to pseudo-Geber). I also don't know whether one should consider the early aqua regia as a use of HCl or start with the pure HCl - elements discoveries are usually counted from pure substances since minerals and alloys were known for ages. Materialscientist (talk) 11:39, 15 August 2010 (UTC)
 * I can give it a go when I get a chance. But ideally I would like agreement with Seanwal111111 since I do not wish to participate in any kind of edit warring. Polyamorph (talk) 11:50, 15 August 2010 (UTC)
 * I would first write a neutral version of the history section. You don't need anyone's agreement for having such a section, as it is auto-protected by the NPOV policy, but there might be disagreement on details (facts and references). Materialscientist (talk) 11:55, 15 August 2010 (UTC)
 * I've made a start here User:Jdrewitt/Sandbox2. Let me know what you think. I added the etymology section because this was removed in its entirety during the purge by Knight1993. I think it should be included but it does require references. Not sure if there are actually enough reliable references that support the view that some authors think Geber actually discovered pure Hydrochloric acid (the chemistrydaily.com site seems to be yet another mirror of wikipedia), they mostly seem to be hinting his use of aqua regia instead. Polyamorph (talk) 17:22, 15 August 2010 (UTC)
 * Actually, I found some more references that attribute the discovery of pure hydrochloric acid to Geber add have added them to my draft history section. So at the very least we have to clarify this misconception. Polyamorph (talk) 18:11, 15 August 2010 (UTC)

Every thing in its place
 * 1) This page is "Chlorine" the history of hydrochloric acid doesn't belong here (see for the mainstream view)I suggest deleting "The most common compound of chlorine, sodium chloride, has been known since ancient times; archaeologists have found evidence that rock salt was used as early as 3000 BC and brine as early as 6000 BC.[7] Before 1400 AD, aqua regia, a mixture of nitric acid and hydrochloric acid, began to be used to dissolve gold.[8]  Upon dissolving gold in aqua regia, chlorine gas is released along with other nauseating and irritating gases, but this wasn't known until much more recently." unless a citation can be found for "Upon dissolving gold in aqua regia, chlorine gas is released along with other nauseating and irritating gases, but this wasn't known until much more recently." such a source would need to show that someone noted the smell (gas) before 1774.
 * 2) Discussion the history of hydrochloric acid should continue there Talk:Hydrochloric acid
 * 3) The historicity of Geber and Jabir needs to take place on their talk pages.
 * J8079s (talk) 21:04, 15 August 2010 (UTC)


 * I agree with those comments by J8070s.
 * I took a look at the draft by Jdrewitt and its references. Here are comments on the references:
 * Myers, R L (2007). Needs to cite his own source, and doesn't do so. Worse than Wikipedia!
 * Datta, N C (2005). This in turn is citing the source named in its footnote 3, an article published in Iranian Journal of Chemistry. Here's a good sign of how terribly ill-informed that source is: Datta cites it as his source for the statement "the alembic is his [Jabir Ibn Hayyan's] great invention." Whereas the medieval Arabic alembic was essentially identical to the 3rd century Greek alembic, as detailed in RJ Forbes's book on the history of distillation (and partly summarized by me just a few weeks ago at Talk:Distilled_beverage).
 * alhewar.org. Says "Jabir is credited with the discovery of red oxide", meaning iron oxide I presume. Whereas several types of iron oxide are in Dioscorides (Book 5). Alhewar.org doesn't distinguish Jabir from Pseudo-Geber. Also alhewar.org has no credentials. I couldn't care less about a source's credentials when the source is making sense to me and is able to back up its assertions about Jabir by quoting from Jabir's writings, but this source doesn't do that.
 * Pereira, Jonathan (1854). One shouldn't cite a NOT-HISTORY reference manual about DRUGS to support a historical statement about chemistry; one should cite a HISTORY of CHEMISTRY book.
 * Not a valid argument - that book contains referenced history section for most its chemicals and is published in 1854 - it does not need to be "historical" in its title. Materialscientist (talk) 00:33, 16 August 2010 (UTC)
 * The book's treatment of hydrochloric acid is 9 pages long and only one paragraph of that is about the history. Similarly its treatment of chlorine is 8 pages long with just one perfunctory paragraph addressing the history of the human knowledge of chlorine. The book's author, Jonathan Pereira, was a pharmacologist, not a historian. And he doesn't cite is sources for his comments about the history of hydrochloric acid or chlorine. So it's a very weak reference. Seanwal111111 (talk)
 * Hugo Bauer (2009). That book by Bauer was published in English in 1907, not 2009, and the German original is of some earlier date (downloadable @ Archive.org. The date is pertinent because today's historians of chemistry don't make the mistake Bauer did. Bauer says "it is certainly more than doubtful whether everything ascribed to Geber does really come from him" but nevertheless goes on to speak of "Geber" as if Jabir and Pseudo-Geber are one and the same. That's a big mistake -- on the order of 500 years of mistake.
 * Norton, S (2008). This non-professional source is entirely based on pages 18 and 61 of Thompson (see below), and the latter is online so the former is devoid of all value as a source.
 * Thompson, C.J.S. (2002). This year 1932 book is online at . In its presentation it fails to distinguish Jabir from Pseudo-Geber except to say in passing "he was the reputed author of a great number of works but many of those which have come down to us in latin are said to be spurious."
 * Which is exactly what pseudo-Geber is about. Note that the book is of 1932 and even now, there is no absolute proof on pseudo-Geber, only a plausible evidence. Thus I would not blame authors who phrase this so. Materialscientist (talk) 00:33, 16 August 2010 (UTC)
 * An earlier version of this book was published by the same author back in 1897 under the title The mystery and romance of alchemy and pharmacy (downloadable). The 1897 version says without qualification and without reference that hydrochloric acid was "discovered" by "Geber" an Arabian, and Geber embodied his researches in his book Summa Perfectionis. The 1932 version, which is improved, was published in 1932 under the title The lure and romance of alchemy and reprinted in 2002 under the title Alchemy and Alchemists. Although improved, this version is still a mass-market book for a casual reader, still lacking references, still not not an authoritive source for anything. Seanwal111111 (talk) 11:23, 16 August 2010 (UTC)
 * All of the above are poor-quality references. Repeating myself, I agree with J8079s that Chlorine is not the page to be talking about this historical stuff in any case. Seanwal111111 (talk) 21:17, 15 August 2010 (UTC)
 * Being the responsible for the changes we are discussing, I must say I took my time to inform myself about the history of alchemy and the Geber problem. In the process I learned that many discoveries credited to Jabir(latinised as Geber) were in fact discovered by an anonymous european alchemist(Pseudo-Geber) who admired Jabir and used his name. Some moder scholars even doubt Jabir ever existed!!!
 * I think that since Berthelot´s work in the subject, most science historians agree that this european alchemist existed, and that the most important works attributed to Jabir were in fact done by him. Take aqua regia, for example. It was long thought to be a Jabir discovery, but now it´s known it is a Pseudo Geber discovery. Those authors who say otherwise don´t recognise the existence of pseudo geber (you will not find any mention to him in those works, because they deny his existence!!).
 * Anyway, I agree that this article is not the right place to discuss this. Maybe in the Jabir or the alchemy articles. Or we could even create a new article about the controversy (the is plenty of material about it). Of course, remarking the majority view that Pseudo Geber really existed. And about the hydrochloric acid, I wouldn´t trust what some books say about its medieval origins. This reliable work by Ladislao Reti dedicated exclusively to this topic says it wasn´t discovered in the Middle Ages. Not all books are realiable. Take the distillation of alcohol: you can find tons of books that claim it was first distilled by the arabs or the chinese. But historians like Sarton, Lynn White, Forbes and Holmyard agree it was first distilled in 12th century Europe. Regards--Knight1993 (talk) 00:27, 16 August 2010 (UTC)
 * Since we started discussing this here, and it is relevant to the history section of this article, then for continutiy purposes it should stay here unless we all agree to move the talk. You can always provide a link from talk:Hydrochloric acid if you feel it is mising some audience.
 * Some of you are missing the point. The point is that there seems to be a misconception over when hydrochloric acid was discovered and whether or not it was discovered by Geber. In my draft history section for the hydrochloric acid article I make this clear from the onset and cite references as evidence that some authors are confused on this issue. (Note after the first two sentences the section is not dissimlar to that edited by Knight1993) You may not like these references but nevertheless the confusion that those authors have is clear, so we're not making it up. However, I also say these are likely to be false and following this I make it clear that most academics believe the discovery of hydrochloric acid to be much later. I see nothing wrong with this, it is basically dispelling the myth that Geber discovered the substance which I thought is exactly what you want? This whole "I'm right, you're wrong" attitude is pising me off, please act more responsibly and actually consider other peoples views. All what the new section does is point out the possible confusion that some authors, and perhaps readers of the article might have over the geber discovery and point out that this is likely not to be true. What's so wrong with doing this. You can't brush under the carpet the fact that some people are confused by this. Polyamorph (talk) 06:44, 16 August 2010 (UTC)
 * BTW that "pissing me off" bit wasn't aimed at you Knight1993, even though it follows your comment. If there are no valid reasons why I cannot include the draft history section I will upload it to the hydrochloric acid article. All though as materialscientist says I don't need anyones permission to do this but I want to make it clear I will not tolerate an edit war. Polyamorph (talk) 08:47, 16 August 2010 (UTC)
 * AGF please - criticism helps a lot to write better, and the above criticism is constructive. I've already learned much history from this event and am grateful to Seanwal111111 for that. Materialscientist (talk) 08:52, 16 August 2010 (UTC)
 * Sorry my bad, yes its true, I know more about the history of hydrochloric acid than previously, which was basically zero. :) Polyamorph (talk) 09:14, 16 August 2010 (UTC)

References There seems to be an issue with the references that I have used. They do meet the guidleines at WP:RS but anyway the point of the references are to show where some authors have the misconception that geber discovered hydrochloric acid, this is the point. I have not added them as evidence that Geber made the discovery. I agree with Seanwal111111 that the authors are incorrect but that in no way makes them invalid citations for the point I am making which is that there are some authors and people in the world that think hydrochloric acid was discovered by Geber. I think that it is important that we clarify that this is not the case. Surely you agree? Polyamorph (talk) 11:35, 16 August 2010 (UTC)
 * I agree. A short clarification at the beggining of the history section is more than enough. Just a question: when you say "Geber", are you refering to the arab or the european Geber? Because the authors who support the medieval discovery thesis are divided in these two groups.--Knight1993 (talk) 18:01, 16 August 2010 (UTC)
 * The arabian Geber. See the draft section here: User:Jdrewitt/Sandbox2. This is for the history section of the hydrochloric acid article. As I said it is essentially your (Knight1993) version of the section but I have added two sentences at the beginning with respect to the misconception. Feel free to comment on the draft/and or make changes. If you think it is suitable I will upload it to the hydrochloric acid article and any further discussion can take place there if needed. Best regards Polyamorph (talk) 18:17, 16 August 2010 (UTC)

Close discussion I have updated the history section in Hydrochloric acid per my version at User:Jdrewitt/Sandbox2. I will also remove the short statement in this article relating to the history of hydrochloric acid per J8079s request since they are not relevant to the history of elemental chlorine. I thank everyone involved in this discussion for their contributions and if there are any remaining issues please discuss them on talk:Hydrochloric acid page. Cheers Polyamorph (talk) 07:19, 17 August 2010 (UTC)

editing the Physical Properties box
I can't quite find the way to edit items in the box. The formatting of the melting-point and boiling-point info needs a tweak, since the strings for the Fahrenheit temperatures are wrapping to new lines after the negative signs. I tried tweaking the template for the box, adding spaces between the "F=" and the value (such as -150.7). No change was evident in the preview, however, so I abandoned that attempt.

It should be simple to discover, but...? Silverhill (talk) 01:17, 25 February 2011 (UTC)
 * Looks fine on my PC. Such changes are to be fixed in the parent template. You can try posting at its talk page (bold editing the parent template without understanding its coding has proven to be risky). Materialscientist (talk) 01:41, 25 February 2011 (UTC)
 * It looks OK to me too, using Firefox (3.6.13). The problem may lie with IE7, even on the wide-screen monitor I was using. I'll just let the sleeping dog lie, of course.

Thanx for the response, sir/ma'am! Silverhill (talk) 04:16, 27 February 2011 (UTC)

Useless information
"Compounds with oxygen, nitrogen, xenon, and krypton are known, but do not form by direct reaction of the elements." Is this a joke?
 * Joke, where?
 * Xenon and krypton are noble gases. Maybe that was over my head. 128.83.139.31 (talk) 23:45, 5 October 2011 (UTC)

Came to this page looking for valence information, found nothing. 70.124.61.238 (talk) 04:17, 18 September 2011 (UTC)
 * Have a look into the box to the right ("oxidation states") and "Compounds" section. Materialscientist (talk) 04:26, 18 September 2011 (UTC)
 * Ah, so that's what an oxidation state is. It was a gap in my learning that I knew I had to look into further, though I didn't know it answered the valency question. Thanks for your help! 128.83.139.31 (talk) 23:49, 5 October 2011 (UTC)

What the EFF?
i noticed something odd. in the french version of this article, in the last section entitled health effects, the english version says something completely opposite to what the french version says. basically the english version says that when used at specified disinfection levels chlorine is "not a major concern for human health". the french version says "Son utilisation pour la désinfection de l'eau potable ou des piscines génère des sous-produits dangereux, dont certains gazeux comme les trichloramines ou NCl3, particulièrement au contact de la sueur et l'urine[16].. Certains sont toxiques, d'autres peuvent entraîner des défauts de naissance, d'autres encore sont génotoxiques, et enfin certains sont des cancérogènes connus". translated roughly, this says "its use for disinfecting potable water or pools generates dangerous by-products and gases like trichloramine or NCl3, particularly in contact with sweat and/or urine. Certain are toxic and can bring about birth defects, others are "genotoxic", and also carcinogenic." the 2 versions are clearly conveying something very different. which version contains more truth? either the english one is glossing over relevant health effects or the french article is overplaying the alarmist position. — Preceding unsigned comment added by 70.26.252.146 (talk) 23:33, 1 November 2011 (UTC)

Edit request on 28 March 2012

 * The density of chlorine is 3.2 kg/L not 3.2 g/L. This article has the wrong units.

130.18.234.229 (talk) 21:10, 28 March 2012 (UTC)


 * Better check your sources. A gas with 3.2 times the density of water? I think not. LeadSongDog come howl!  22:06, 28 March 2012 (UTC)

Oxidation states
There's a table listing the oxidation states of chlorine at Chlorine. It lists ethylaluminium sesquichloride, EtAlCl2, as example of chlorine in the +2 oxidation state, without providing a reference. I think this is nonsense. This compound contains chloride, Cl(−1), as a bridging ligand. I would have removed the entry on sight, but I just wanted to check no-one intended it to be there for any reason. --Ben (talk) 10:17, 29 May 2012 (UTC)

File:Chlorine liquid in an ampoule.jpg to appear as POTD soon
Hello! This is a note to let the editors of this article know that File:Chlorine liquid in an ampoule.jpg will be appearing as picture of the day on August 11, 2012. You can view and edit the POTD blurb at Template:POTD/2012-08-11. If this article needs any attention or maintenance, it would be preferable if that could be done before its appearance on the Main Page so Wikipedia doesn't look bad. :) Thanks! — howcheng  {chat} 23:00, 10 August 2012 (UTC)

Chlorine and Dr. John Snow
I removed the incorrect statement that claimed Dr. John Snow added chlorine to cholera-contaminated water from the Broad Street pump. The incorrect information comes from a book originally written by George C. White and now published by the consulting firm Black and Veatch Ref: Black and Veatch Corp. (2010). White's Handbook of Chlorination and Alternative Disinfectants. Hoboken, NJ:Wiley. first page, Chapter 9. White never provided a reference for his claim and a careful reading of the three major chronicles of the Broad Street pump epidemic never mentioned the event. Refs: Hemphill, Sandra. (2007). The Strange Case of the Broad Street Pump: John Snow and the Mystery of Cholera. Los Angeles:University of California; Johnson, Steven. (2006). The Ghost Map: The Story of London’s Most Terrifying Epidemic and How It Changed Science, Cities and the Modern World. New York :Riverhead Books; Vinten-Johansen, Peter, Howard Brody, Nigel Paneth, Stephen Rachman and Michael Rip. (2003). Cholera, Chloroform, and the Science of Medicine. New York:Oxford University. This error has been widely repeated on many websites which likely obtained the inaccurate information from this Wikipedia page.

The likely reason that White got it wrong in the first place is that chlorine in the form of chloride of lime or calcium hypochlorite was used to "disinfect" the streets surrounding the Broad Street pump neighborhood. This was common practice in mid-19th century England due to the accumulation of filth and miasma-producing decaying putrefaction. Here is a quote that explains what really happened:

“An oil-shop puts forth a large cask at its door, labeled in gigantic capitals ‘Chloride of lime.’ The most remarkable evidence of all [of the severity of the cholera attack], however, and the most important, consists in the continual presence of [chloride of] lime in the roadways. The puddles are white and milky with it, the stones are smeared with it; great splashes of it lie about in the gutters, and the air is redolent with its strong and not very agreeable odour….The fact is that the parish authorities have very wisely determined to wash all the streets in the tainted district with this powerful disinfectant; and, accordingly, the purification takes place regularly every evening.” Refs:  Vinten-Johansen, et al., Cholera, 296; quoted from The Times:  “The cholera near Golden Square,” Times (15 September 1854). Drinkingwaterdoc (talk) 16:51, 14 August 2012 (UTC)


 * Yes. Snow is well known for removing the handle of the Broad Street pump (which was pumping up contaminated water from the Thames), but you make a good case for him not using chlorinated lime or calcium hydroxide/calcium hypochlorite (which was confusingly called chloride of lime). It's hard to prove a negative, but if nobody mentions Snow, we can't. Your quotes, however, do show that the public health authorities DID use the stuff in this way for the London epidemic, and that's as good for a line or two in this article as the Snow quote. We don't care WHO here, we care about WHAT (specitically elemental chlorine and its uses). So you get two points for removing an incorrect statement, but minus one for not replacing it with a correct statement that you had three sources for. S  B Harris 17:27, 14 August 2012 (UTC)


 * Good point. I will add a sentence or so with the three references. Sorry to nitpick but the Broad Street pump was contaminated from a cesspool right next to the well.  Vinten-Johansen, et al., have a great discussion of how the contamination of the well occurred on pages 283-5 and 360. Drinkingwaterdoc (talk) 17:54, 14 August 2012 (UTC)


 * Another confusing point is that the test Snow used in 1849 to distinguish the water from the two companies in London was a chloride ion test: one company's water intake was much further up the Thames, so had much less NaCl from tidal seawater. This made it a good proxy test for London sewage (barring the ever-present risk of post-intake contamination), but not for sewage from further upstream.
 * On 30 June 1890 J Soc Chem Indust carried an item here on pp.643-4 reviewing a paper by F. Nissen "The disinfecting action of chloride of lime". The review gave credit to Koch in his paper "On Disinfection" for the first bacterial testing of chloride of lime, but that was on anthrax spores. Nissen then in 1890 disclosed further tests of CaCl solution on cholera, typhoid, anthrax, staph, and strep, establishing the necessary concentrations and contact times, but essentially confirming Koch's result. LeadSongDog come howl!  19:44, 14 August 2012 (UTC)


 * Again remember that "chloride of lime" is not calcium chloride CaCl2. It is bleaching powder, calcium hypochlorite, or chlorinated lime. See here. Calcium chloride is no more bacteriocidal than sodium chloride is (which is to say, it isn't at all). It's the free chlorine that does the job. S  B Harris 20:39, 14 August 2012 (UTC)
 * Sure, the question that took some time to be understood was just how free chloride comes to be free. The Nissen paper is available, but Springer wants US$39.95 for access to a paper that's in the public domain. It oughta be illegal. Anyhow, my German is near nonexistent.  clarified it much later. LeadSongDog  come howl!  21:22, 15 August 2012 (UTC)

Chlorine's being carried by bases (calcium or sodium hydroxide) is just a disproportion reaction to chloride (-1) and hypochlorite (+1). Hypochlorite is stable (more or less) in base, but equilibrium always liberates some free chlorine, since that escapes from the mix as a gas, so even if it's not favored in free energy, the diffusion of one product away drives the backreaction to completion eventually. So these things are always slow releasers of elemental chlorine, and hold a lot more available elemental chlorine per unit of solution than simple chlorine solution in water. That's the entire "trick" of chlorine bleaches. Of course this can be sped up, as the less basic you make hypochlorite, the more it's driven to water and elemental chlorine (one reason they are so fanatical about pH in swimming pools). The sudden back-reaction away from disproportionation to 0 oxidation state and free Cl2 gas happens when people go to low pH by adding bleach to acidic drain cleaners, and gas themselves in their bathrooms. I made a lot of chlorine experimentally that way in my boyhood, using it to gas outdoor red ant beds, and many other fun reactions. S B Harris 21:37, 15 August 2012 (UTC)

NFPA 704
Shouldn't the NFPA 704 fire diamond be on the table on the side like it is with most chemicals? Njaohnt (talk) 17:56, 17 November 2012 (UTC)

Wrong figure?
The reputable site www.epa.gov/ttn/atw/hlthef/chlorine.html has it that

"Chlorine has a suffocating odor; the odor threshold is 0.31 ppm"(7)

reference: (7) J.E. Amoore and E. Hautala. Odor as an aid to chemical safety: Odor thresholds compared with threshold limit values and volatilities for 214 industrial chemicals in air and water dilution. Journal of Applied Toxicology, 3(6):272-290. 1983.

Yet this page, perhaps a mistake with the decimal point, says it smell onyl at > 3ppm, out by x10. — Preceding unsigned comment added by 46.7.75.29 (talk) 09:48, 8 December 2013 (UTC)

Status of article
Why is it that this article can't be edited (at least by IP users), yet there is no explanation or announcement of this fact placed conspicuously near the top of the article? 178.38.163.83 (talk) 05:52, 16 December 2014 (UTC)
 * The page was protected last December 8, because of vandalism . This is noted when one tries to edit/view_source (this difference also indicates the protection status). -DePiep (talk) 12:42, 16 December 2014 (UTC)
 * Thanks for the tip. I understand now that a lock only sometimes appears on the main article page, but it's always visible if you follow the "view source" link. 178.38.100.126 (talk) 23:36, 17 December 2014 (UTC)

Hydrophilic nonreactive
The half-life of this hydrophilic nonreactive isotope makes it suitable for geologic dating in the range of 60,000 to 1 million years.

How can one isotope of an element have chemical properties (hydrophilicity, nonreactiveness) that differ significantly from those of another isotope? 178.38.100.126 (talk) 23:30, 17 December 2014 (UTC)


 * It can't. I suspect that the sentence means Cl-36 is hydrophilic (like all chlorine) then after decay becomes Ar-36, which is non-reactive. But it's not at all clear. I think a few descriptors will have to be removed till the original writer can clarify or provide a ref. S  B Harris 00:35, 18 December 2014 (UTC)


 * Bravo. Thanks. 89.217.13.95 (talk) 00:01, 19 December 2014 (UTC)


 * ahh.. is this material liquid on room temperture?? just a.. curious.. here.. thanks. 175.223.23.115 (talk) 16:48, 29 April 2015 (UTC)


 * No. Plant surfer 17:33, 29 April 2015 (UTC)

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Commercial conflict of interest
Your edit isn't ok in my opinion, because ist is very valuable and educational. This image is a featured picture too. Did you read the describtion? All things are "commercial products" ...! I'm not a seller or other commercial contributor. Best regards, the image owner :-) --Alchemist-hp (talk) 20:40, 9 February 2016 (UTC)


 * I think there is a clear commercial conflict of interest here, advertising in WP by stealth. Plant surfer  20:45, 9 February 2016 (UTC)


 * "commercial conflict" between whom??? No seller or contributor is named. No a seller webside is named. ... --Alchemist-hp (talk) 20:47, 9 February 2016 (UTC)


 * Other real commercial side: Mercedes-Benz ;-) --Alchemist-hp (talk) 20:50, 9 February 2016 (UTC)
 * The second image of liquified chlorine (in plastic) is redundant. I also wonder if it is not stealth advert but the main thing is that it is a just wasted space and conveys nothing.  --Smokefoot (talk) 21:10, 9 February 2016 (UTC)


 * Sorry, it conveys yellow liquified chlorine under pressure. The image describtion say us the conditions. It isn't nothing? Other opinions? --Alchemist-hp (talk) 21:29, 9 February 2016 (UTC)


 * I don't really have an opinion about whether the image is redundant or unnecessary, but the suggestion that there is a "clear commercial conflict of interest here" or even a "stealth advert" seems completely unfounded. -- Ed (Edgar181) 21:37, 9 February 2016 (UTC)
 * +1 thanks, --Alchemist-hp (talk) 21:38, 9 February 2016 (UTC)
 * Sorry. but the sealed ampoule is also under pressure.  Is there something special about 7.4 bar vs the ambient pressure of the ampoule (probably a couple of bar)?   --Smokefoot (talk) 21:39, 9 February 2016 (UTC)
 * The inside pressure in an ampoule of liquified chlorine under room temperature is about ~7.4 bar. You know it! You can read it from a phase diagram data table about chlorine. --Alchemist-hp (talk) 21:45, 9 February 2016 (UTC)
 * So why do we need two images then? --Smokefoot (talk) 21:57, 9 February 2016 (UTC)
 * The first one is under pressure and room temperature, the other one is cold ​−34.04 °C = ​−29.27 °F under room pressure. The first one is a sample for viewing purposes, the other one is only temporary visible and available in a laboratory. But you know this too! --Alchemist-hp (talk) 22:06, 9 February 2016 (UTC)
 * So, we have a second image with other temp & press. As Smokefoot says, why two images? Why not 1M images by 'all' temp & press options? So far, possible commercial issues aside, I see no need for this redundant second image. -DePiep (talk) 23:31, 9 February 2016 (UTC) (Note: I was invited to this topic by Alchemist-hp on my talkpage)
 * I don't see the need for a second image, but neither do I see any advertising here. Double sharp (talk) 23:57, 9 February 2016 (UTC) (also similarly invited)


 * So as far as I can tell the first image is Chlorine gas. The image in question is liquid chlorine.  These are different phases of the same substance, exhibiting different physical characteristics and properties.  There is no question that it is useful for the readers to have images of both liquid and gaseous Cl.  As for the "commercial conflict", there is no evidence of this whatsoever...Polyamorph (talk) 22:28, 11 February 2016 (UTC)
 * I see the second "liquid" chlorine image now (sorry I didn't scroll down far enough and thought we were discussing the very top image of chlorine gas). Well there is a redundancy issue here, not much point in having two images showing the same thing, but the original reason for removing the image (commercial conflict of interest) is nonsense. Polyamorph (talk) 22:32, 11 February 2016 (UTC)

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Semi-protected edit request on 7 April 2016
The NOAA Database of Hazardous Materials lists a health hazard of 4 for Chlorine, not 3. The fire diamond in the "Health effects and hazardsHealth effects and hazards" needs to be changed.

https://cameochemicals.noaa.gov/chemical/2862

Reubenmorais (talk) 02:21, 7 April 2016 (UTC)


 * Thanks for spotting this. Although in the first pdf I opened it is 300Ox. But in all others including your link it is 400Ox.--Stone (talk) 09:39, 7 April 2016 (UTC)


 * - Please attribute edits made by request in the edit summary. Thanks. fredgandt 02:32, 8 April 2016 (UTC)

Semi-protected edit request on 3 September 2016
I want to change volts in to volts

Maarten2071 (talk) 17:44, 3 September 2016 (UTC)
 * ❌ we only link the first use, and the first use is linked, to link them all would be Overlinking- Arjayay (talk) 18:04, 3 September 2016 (UTC)

Semi-protected edit request on 29 November 2016
Minor error in the isotope section It reads "The most stable bromine radioisotope is 36Cl." but should read "The most stable chlorine radioisotope is 36Cl."

Prof. William White, Earth and Atmospheric Sciences, Cornell University William White (talk) 16:22, 29 November 2016 (UTC)
 * Yes check.svg Done  JTP ( talk • contribs) 15:49, 30 November 2016 (UTC)

The cathode reaction is not correct.
In the Production section, electrolytic process, the equation of the reaction that is taking place at the cathode of a sodium chloride electrolysis cell is not correct:

2H+ + 2e- -> H2

The correct reaction is:

2H2O + 2e- -> H2 + 2OH-

The first reaction has a potential of 0V by convention while the second has a potential of -0.8277V: the energy consumption of the whole cell is thus much higher in the second case. This is important because the process is often described as an energy intensive process. This equation also shows how the hydroxide ions of sodium hydroxide are formed.

Miloud90 (talk) 01:14, 26 April 2016 (UTC)
 * Corrected. Thank you! Double sharp (talk) 13:58, 16 December 2016 (UTC)

Inverted redox reaction or opposite potential
In the Chlorine Oxides section, a table lists some redox half reactions involving chlorine oxoanions. The reactions are oxidation reactions (electrons are on the right side of the reaction equation) but the proposed potebtials are reduction potentials. Either the reactions must be inverted or the potentials replaced by their opposite number.

Miloud90 (talk) 19:26, 26 April 2016 (UTC)
 * Corrected. Thank you! Double sharp (talk) 13:58, 16 December 2016 (UTC)

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Semi-protected edit request on 1 May 2017
I would like to have added to the section "Use as a weapon" that: According to RT (and AP) on 15th April 2017 IS used a chlorine gas missile against US-backed Iraqi troops in western Mosul, Iraq. (source: https://www.rt.com/news/384862-mosul-chlorina-attack-report/) According to RT (and various other outlets) on 17th April 2017 IS used a chlorine gas missile against Iraqi troops. Iraq's Joint Operations Command stated on facebook that neither of the attacks caused any casualties. (source: https://www.rt.com/news/384995-isis-chemical-gas-attack-mosul/) Thank you. 201.214.75.115 (talk) 18:03, 1 May 2017 (UTC)


 * I think this would fit better under Use of chemical weapons in the Syrian Civil War; the article might need re-shuffling to account for operations in Iraq but it's effectively a single conflict. It's too much detail for this article. Power~enwiki (talk) 22:57, 25 May 2017 (UTC)

Semi-protected edit request on 24 December 2017
For grammar's sake, requesting the change of "(chlorine dissolved in pure water, which was cheaper chlorinated lime solutions)" to "(chlorine dissolved in pure water, which was cheaper than chlorinated lime solutions)", change bolded for ease of identification for editor. Affected heading is Applications:Sanitation, disinfection, and antisepsis:Semmelweis and experiments with antisepsis. Thank you! Kaerea (talk) 21:49, 24 December 2017 (UTC)
 * Yes check.svg Done Gulumeemee (talk) 23:42, 24 December 2017 (UTC)

Semi-protected_edit_request_on_28_March_2018
An edit request wrt the NFPA hazard diamond ended up here at the infobox talkpage. I strongly suggest to keep it there. - DePiep (talk) 15:54, 28 March 2018 (UTC)

Semi-protected edit request on 5 November 2018
Chlorine is not in the group 17 it is in group 7. Please change this as it can get many people in trouble and could end in failed exams. Thank you for reading this. Yours Sincerely PoisonGS PoisonGS (talk) 19:43, 5 November 2018 (UTC)


 * ❌ see for example Group (periodic table): group "17" is correct, in the modern unambiguous numbering system. Maybe you meanty to writte group "VII" (in Roman numeral system), which was correct until circa 1930, but afterwards that group was named "VIIB" (or "VIIA" depending on your chemical organisation). To prevent failing exams, you should study this A/B issue because there also is a grouop "VIIA" ("VIIB" elsewhere then) that does not have chlorine, but man­ga­nese (modern group number: "7" ouch). Best advice: 1. use the modern numbering 1–18, 2. use the Roman number value as oxidation state for that group (which is the background of that group numbering), and 3. outsmart your teacher with this knowledge. -DePiep (talk) 19:55, 5 November 2018 (UTC)

Semi-protected edit request on 13 December 2018
Replace the word 'crustal' in the article with the word 'crystal'. SheepWillPrevail (talk) 07:05, 13 December 2018 (UTC)
 * ❌ "Crustal" is correct (the described deposits are in the Earth's crust). Double sharp (talk) 07:25, 13 December 2018 (UTC)