Possible to make free chlorine aqueous solution without Cl gas?

[pippo]

Trying to see if its possible to make a free Cl aqueous by say, mixing some HCl and nitric conc to genetrate Cl2. Then test with thiosulfate to verify Cl2 content, then standardize.

 

Tips/opinions appreciated.

[elementcollector1]

Not the best way to make chlorine solution. It wastes nitric acid, a much more valuable reagent than chlorine water, and a simpler way would still be to bubble elemental chlorine through distilled water in an opaque or possibly amber-glass container (as to prevent disassociation into HOCl and HCl). This will get you a very pure solution of chlorine water, without complications such as excess nitrogen compounds or acids.

[pippo]

Thanks. element. Only thing- I dont have Cl gas. dangerous stuff. I dont care if its not pure- as long as the Cl 2 value is there. Thats the only thing that matters. A bit more of nitric is not an issue.

[John Cuthber]

Unless a little excess NaCl is going to upset things, the easy way is to add dilute HCl to ordinary bleach.

2 NaOCl + 4 HCl --> Cl2 +2 H2O +2NaCl

[pippo]

Unless a little excess NaCl is going to upset things, the easy way is to add dilute HCl to ordinary bleach.

2 NaOCl + 4 HCl --> Cl2 +2 H2O +2NaCl

 

Gees, Johm, that just might be the best way to do this. Thanks, man! Gona try it tomorrow.......

[ajkoer]

Actually, I recommend 'John Cuthber' classic method also.

However, if one is interested in a less conventional, more accessible for some, but more expensive (but perhaps safer in avoiding the storage of strong acids for the home chemists) route to Chlorine (Cl2) which occurs as a reported side product in this proposed method. The chief product of interest, cited in multiple patents (for example, see United States Patent 4380533 at http://www.freepatentsonline.com/4380533.html or, a non-patent textbook reference http://books.google.com/books?id=yZ786vEild0C&pg=PA74&lpg=PA74&dq=dibasic+magnesium+hypochlorite&source=bl&ots=WsG8bHQyX8&sig=XnsYZC6fir8XW61NDm3hvEc_iW8&hl=en&sa=X&ei=jal-UeqrCNLh0wG024GQDw&ved=0CDoQ6AEwBg#v=onepage&q=dibasic%20magnesium%20hypochlorite&f=false ) is dibasic Magnesium hypochlorite Mg(OCl)₂.2Mg(OH)₂ (used in bleaching and sanitizing applications) in which Cl2 is also apparently generated. The bleaching salt is reported to separate out easily.

So, apparently one does not need HCl (impure or otherwise) just NaCl, NaOCl and MgSO4 hydrate (Epsom salt). The process for liberating Cl2 and in more dilute solutions (or, upon addition of H2O to a closed vessel and shaking) would result in chlorine water.

The cited net ionic reaction per the above patent:

3 Mg⁺ + 4 ClO^- + 2 Cl^- + 2 H₂O ➝ Mg(OCl)₂.2Mg(OH)₂ + 2 Cl₂

Or, upon employing NaCl, NaOCl and MgSO4.7H2O, the net reaction could be stated as:

3 MgSO4.7H2O + 4 NaClO + 2 NaCl ---> Mg(OCl)₂.2Mg(OH)₂ + 2 Cl₂ + 3 Na2SO4 + 19 H2O

As NaOCl found in commericial chlorine bleach is basic per the addition of a little NaOH and, at times, Na2CO3, adding acetic acid (or ascorbic acid,..) to adjust the pH to be between 3 to 7 may be required (or the use of a more acidic chloride salt like CaCl2 in place NaCl). Dilution here may not actually be a bad thing as the goal, after all, is chlorine water, however, I suspect that the reaction actually requires a concentrated solution. My logic: the normally weak acid hydolysis of sulfate salt produces, in highly ionic conditons, a higher 'activity level' for the acid (or a lower one for H2O), resulting in the liberation of chlorine. Note, in earlier versions of this patent, a solid hydrated salt to solid reaction is recommended, which is in line with my ionic characterization.

Some may find more interesting a claim from an old sciencemadness thread that Cl2 is generated by the action of bleach (actually a mixture of NaOCl and NaCl due to its creation by the action of chlorine on NaOH) on FeSO4 (see comments by Proteios at https://www.sciencemadness.org/whisper/viewthread.php?tid=1305 ). If confirmed, this reaction bares a strong parallel to the one cited above and is, in line, with my change in 'activity level' argument of the acid salt. [Edit] Some confirmation from the cited thread, page 2, to quote Proteios "from memory the reaction goes best when the FeSO4/ bleach mix is a thick goopy brown mess."
Nevertheless, the general lack of discussion in the literature of this apparently observed reaction suggests that the mechanism of the FeSO4/hypochlorite reaction is not generally well understood (except, of course, now by us, or, at least, so we have an understandable and tentative reaction path which appears to more broadly concur with observations).

Edited April 29, 2013 by ajkoer

[elementcollector1]

Interesting! If this works, that is.