AJKOER
Radically Dubious
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What is the 'Harmless' Smell of Chlorine Bleach, Cl2 or Cl2O?
Here are my thoughts on the chemistry, as outlined in this work for the commercial production of chlorine bleach, per Eq (3), to quote:
(3) Cl2 + Na2CO3 + H2O -> HOCl + NaCl + NaHCO3
Link: https://www.forceflowscales.com/downloads/chemical-safety/hy...
Now, if the Bleach is spilled and open to air/CO2 contact:
CO2 + H2O + 2 NaOCl -> HOCl + NaCl + NaHCO3
which is the same as the right side of Eq (3) and to the extent it is reversible, yes it could be, indeed, chlorine.
However, HOCl may simply just be salted out of its Cl2O:
2 HOCl <--> H2O + Cl2O
as it is long known per Watts Dictionary of Chemistry, that distilling dilute HOCl nearly double its concentration suggesting a heating release of the
Cl2O.
So, which is it, Cl2 or Cl2O?
My guess based on how rapidly the 'chlorine' smell can be eliminated in a bathroom just subject to cleaning with NaOCl upon steaming the room from a
very hot water shower action, that it is Cl2O, but still it also could be Cl2, which does, albeit more slowly, reacts with water.
[Edited on 23-12-2021 by AJKOER]
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AJKOER
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OK, just found a reference, interestingly, reported by Watt’s in his Dictionary of Chemistry, page 16, to quote:
“Properties:- An aqueous solution of HClO smells like Cl2O.”
So, upon the action of CO2, we have hypochlorous acid which smells like dichlorine monoxide and not chlorine.
So, there is apparently two opinions claiming Cl2O and not Cl2.
Albeit, the rest of the world still refers to it as the smell of chlorine.
[Edited on 23-12-2021 by AJKOER]
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AJKOER
Radically Dubious
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Registered: 7-5-2011
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Did find an answer here https://www.quora.com/Does-liquid-bleach-sodium-hypochlorite... by one Chris Pohl with relevant background also noting the smell of NaOCl is one
of HOCl due to an equilibrium reaction, even in alkaline pH.
The latter is a stronger statement than mine, for the record, affirming the possible presence of Cl2O in air.
Also, I should add there many answers trying to mitigate any possible health effects of reputedly chlorine/chlorine bleach exposure. Unfortunately,
Cl2O is not Cl2 or even HOCl, and is actually a more powerful chlorinating agent. Here is am abstract of a study out of Research Gate https://www.researchgate.net/publication/51974676_Assessing_... , to quote:
"Abstract
Cl(2) and Cl(2)O are highly reactive electrophiles capable of influencing rates of disinfection byproduct (DBP) precursor chlorination in solutions of
free available chlorine (FAC). The current work examines how organic compound structure influences susceptibility toward chlorination by Cl(2) and
Cl(2)O relative to the more abundant (but less reactive) electrophile HOCl. Chlorination rates and products were determined for three aromatic ethers,
whose reactivities with FAC increased in the order: 3-methylanisole <1,3-dimethoxybenzene <1,3,5-trimethoxybenzene. Varying solution conditions
(pH, [FAC], [Cl(-)]) permitted quantification of regiospecific second-order rate constants for formation of each product by Cl(2), Cl(2)O, and HOCl.
Our results indicate that as the reactivity of methoxybenzenes decreases, the importance of Cl(2) and Cl(2)O (relative to HOCl) increases.
Accordingly, Cl(2) and Cl(2)O are likely to play important roles in generating DBPs that originate from natural organic matter (NOM) constituents of
somewhat moderate reactivity. As [Cl(2)] is proportional to [Cl(-)] and [Cl(2)O] is proportional to [HOCl](2), ramifications for DBP control measures
may differ significantly for these precursors compared to more reactive NOM moieties likely to react predominantly with HOCl. In particular, the role
of chloride as a chlorination catalyst challenges its traditional classification as an "inert" electrolyte in water treatment processes."
My important take, Cl2O reactivity increases relative to that of HOCl and can play an important role in the formation of problematic disinfection
byproduct (DBP). Also, as NaOCl can be made from the action of Cl2 on NaOH, there exists at least equal amounts of OCl- and Cl- found in common
chlorine bleach, where chloride role in subsequent applications by direct aqueous reactions may be of significance.
The science from the perspective of the possible longer term effects, makes difficult the argument of claiming a totally benign nature of the
associated chlorine smell (namely, Cl2O) as generated from chlorine bleach in air or with direct application on surfaces, especially in the presence
of organic materials.
However more short-term in, say, a hospital setting, having the powerful presence of dichlorine monoxide to address microbes is probably a very good
thing.
[Edited on 23-12-2021 by AJKOER]
[Edited on 23-12-2021 by AJKOER]
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