[Edited on 16-2-2013 by K12Chemistry]cAMP - 16-2-2013 at 09:49
I'm not 100% sure, but it seems to me that since we're talking about purely ionic products that are totally dissociated in solution, that the more
electronegative chloride and the more electropositive potassium would reassociate upon evaporation leaving you with KCl and NaI again. Also since
they are both very soluble, you'd have a bear of a time separating them even if they did exchange anions.smaerd - 16-2-2013 at 12:07
Maybe it could happen in acetone? I haven't really checked into the theory then again I doubt potassium chloride is soluble in acetone. Although I
know sodium iodide is soluble in acetone while potassium iodide is only slightly soluble. Think the chlorides is where this would fail.
I'd imagine it requires more energy to form the products then the reactants, then again I haven't done any number crunching on it. Ethalpy, Entropy,
and Gibbs free energy calculations may help lead the way. Then again there's a lot of factors that play into these things, solubility, etc. It may
occur to a small degree.K12Chemistry - 16-2-2013 at 13:31
what about NaOH+KCl -> NaCl + KOH
See i'm trying to making potassium iodide and all I have is sodium hydroxide. I don't have potassium hydroxide. Can anyone suggest a method in which I
can make potassium iodidevmelkon - 16-2-2013 at 18:20
Perhaps try this :
heat NaI and H2SO4 together (or NaHSO4) and drive off the HI gas into a solution of KOH.AJKOER - 17-2-2013 at 05:57
Perhaps try this :
heat NaI and H2SO4 together (or NaHSO4) and drive off the HI gas into a solution of KOH.
This does not work.
If you add H2SO4 to NaI, then you get a very dirty and smelly mix of I2, S, H2S, HI, SO2 and H2O. Iodide is partially oxidized by the concentrated
H2SO4 or hot NaHSO4.AJKOER - 20-2-2013 at 06:20
OK, one could always consider adding Oxalic acid, H2C2O4 to aqueous NaI and filter out the Na2C2O4:
H2C2O4 + 2 NaI (aq) --> Na2C2O4 (s) + 2 HI
then add KOH and you are done.
Note, heating solid NaI and H2C2O4 would most likely form gaseous HI in a parallel reaction to the formation of HCl gas by heating Oxalic acid and
NaCl.AJKOER - 25-2-2013 at 06:37
OK, one could always consider adding Oxalic acid, H2C2O4 to aqueous NaI and filter out the Na2C2O4:
H2C2O4 + 2 NaI (aq) --> Na2C2O4 (s) + 2 HI
then add KOH and you are done.
Note, heating solid NaI and H2C2O4 would most likely form gaseous HI in a parallel reaction to the formation of HCl gas by heating Oxalic acid and
NaCl.
In the aqueous reaction, I should point out that as Oxalic acid will readily reduce aqueous HCl to Cl2 (per Watts) and assuming a similar reaction
with HI (reducing it to I2), one should maintain an excess of aqueous NaI, so slowly add H2C2O4 with stirring.
In general, one should be mindful of the reducing properties of H2C2O4 as, for example, its action on KClO3 will form HClO3 and, with excess Oxalic
acid, further reduce the Chloric acid to explosive and toxic ClO2.
[Edited on 25-2-2013 by AJKOER]woelen - 25-2-2013 at 07:14
[...]In the aqueous reaction, I should point out that as Oxalic acid will readily reduce aqueous HCl to Cl2 (per Watts) and assuming a similar
reaction with HI (reducing it to I2), one should maintain an excess of aqueous NaI, so slowly add H2C2O4 with stirring.[...]
This definitely is not true. Oxalic acid does NOT reduce (nor oxidize) HCl or HI! There are two mistakes in your sentence:
1) You talk about reduction of aqueous HCl to Cl2 or HI to I2. This is incorrect. If HCl is converted to Cl2, then it is oxidized.
2) Oxalic acid cannot oxidize HCl to Cl2, nor can it oxidize HI to I2.
Quote:
Note, heating solid NaI and H2C2O4 would most likely form gaseous HI in a parallel reaction to the formation of HCl gas by heating Oxalic acid and
NaCl.
Does this reaction really occur? I have severe doubts. Oxalic acid, when heated, sublimes easily, even
at just above 100 C it sublimes. I expect that when you heat a mix of NaCl and oxalic acid, that you get mostly vapor of oxalic acid and at most
traces of HCl.
[Edited on 25-2-13 by woelen]AJKOER - 25-2-2013 at 21:45
Woelen:
Thanks for the corrections.
I was speaking from recollection (it is always good to put in your reference) and the correct statement per Watts (see bottom of page 250 link: http://books.google.com/books?pg=PA250&id=lYXPAAAAMAAJ#v... ) is that H2C2O4 acts on Hypochlorous acid (not HCl) to form HCl no less.
More interestingly, per Watts, H2C2O4 acts on Cl2 to form HCl and similarly for Br2 (so forming HBr). So, it may be (speculation) that H2C2O4 acts on
I2 to produce HI.
Now onto the reaction of H2C2O4 and NaCl, another source "The Manufacture of Sulphuric Acid and Alkali: Ammonia-soda, various ...", by Georg Lunge
(link: http://books.google.com/books?id=FnrTAAAAMAAJ&pg=PA246&a... ), claims to have proven that the ignition of H2C2O4 and NaCl produces carbonate
with CO and HCl escaping. This statement is in agreement with Watts as the thermal decomposition of Sodium oxalate is, in fact, carbonate and CO (see
http://www.ncbi.nlm.nih.gov/pubmed/18962335 ).
[EDIT] Here is another source to quote:
"When common salt is distilled with aqueous oxalic acid, a large quantity of hydrochloric acid is evolved. (Berthollet, Statique Chim. 1, 271.) Dry
chloride of sodium or chloride of calcium intimately mixed with hydrated oxalic acid, gives off all its hydrochloric acid when heated, so that the
residue left after ignition consists of carbonate of soda or carbonate of lime. (A. H. Wood, Phil. Mag. J. 5, 445; compare Kobell (J. pr. Chem. 14,
379.)"
So, the reaction with H2C2O4 and NaI may or may not behave similarly with the gaseous formation of CO and HI.
[Edited on 26-2-2013 by AJKOER]woelen - 26-2-2013 at 02:16
Oh yes, I do believe that some HCl and CO can be formed from NaCl and oxalic acid, but I think most of it will escape the mix as vapor. This certainly
is not a viable route to HCl. If it were, then many people would use this as a nice and cheap way of making HCl from cheap and easy to obtain
reagents. I believe that it is just a theoretical reaction, which occurs in trace amounts.
But why don't you try it? You have oxalic acid? Try heating some mix with NaCl and see what happens.AJKOER - 26-2-2013 at 04:20
I am out of H2C2O4 at the moment and I am debating whether to get the dihydrate again or the dry acid. My concern is the dry acid may be more likely
to have a toxic dust issue, as well as more likely to contribute to an explosion as I recall reading that the dry acid has the interesting property
that it can be detonated but, by itself, is stable and non-explosive. So for example, inadequate mixing with a chlorate could locally produce ClO2,
whose subsequent detonation could be a primer for the anhydrous H2C2O4. An inadvertent and sizable detonation is one possible explanation as to how
this property was discovered.
[EDIT]: Found a reference "Bretherick’s Handbook of Reactive Chemical Hazards", sixth edition, page 269, to quote:
"CHETAH, 1990, 184
Surprisingly, even the dihydrate is apparently detonated by a 50 g tetryl booster,
the anhydrous acid is thermally less stable and thus probably more sensitive. There
is, however, no history of explosion."
Link: http://eng.monash.edu/materials/assets/documents/resources/o...
-------------------------------------------
I did find another reference source (see my edited comment above) and, it is claimed, that even the H2C2O4.2H2O liberates HCl on heating. To quote:
"Dry chloride of sodium or chloride of calcium intimately mixed with hydrated oxalic acid, gives off all its hydrochloric acid when heated"
But, it may indeed be that intimate mixing (which is not legal in all these United States) is necessary for a proper reaction. My last batch of the
hydrated acid would make this difficult (very damp).
[Edited on 26-2-2013 by AJKOER]ScienceSquirrel - 26-2-2013 at 07:12
I have my doubts that a mixture of sodium chloride and oxalic acid will react to release hydrogen chloride but sodium hydrogen sulphate will react in
this manner and the first pKa is not that far off;
However your references are very old, 1870 in one case, and to imagine that the reaction could be extended to hydrogen iodide which is a lot stronger
acid.
Why would intimate mixing be illegal in the United States? I also doubt that it would explode at all done on a small scale, say a gram or so in an
open test tube.AJKOER - 2-3-2013 at 14:00
Science Squirrel:
I find the old texts very informative and usually quite accurate on reporting observed products. In fact, in those days, Chemistry appears to be
taught by studying a large range of reactions, and not much (understandably) on theory. I also think this is very important today as noticing (and
studying) a deviation from today's theoretical expectations can be very enlightening, and perhaps lead to new/profitable ideas.
----------------------------------------------------
Now on the H2C2O4.2H2O and NaCl reaction, I believe the concerns expressed by Woelen are valid especially absence thorough mixing, however, otherwise
possible. To be open, some reservations have been expressed previously on this comment (see "Using Oxalic Acid to Make H2SO4,..." at http://www.sciencemadness.org/talk/viewthread.php?tid=18963).
this route for HBr might just work, but for HI probably not. HI is very susceptible to oxidation to I2, it decomposes in the presence of O2,
accelerated by light. according to Brauer you would use hypophosphorous acid instead (a reducing agent). that's what makes red phosphorus so important
=D
edit. actually Brauer reports I2 + H3PO2, the wikipedia reference is wrong. H3PO2 might be overkill, but it probably works too
[Edited on 3-10-2012 by tetrahedron]
So the amount of O2 exposure may be an important factor.
I suspect that Oxalic acid acting on Sodium iodide will also form Hydroiodic acid, as per this source page 182 (https://docs.google.com/viewer?a=v&q=cache:mE02fxIC8rcJ:... ), even Citric acid is apparently so capable of creating aqueous HI.
Now, even if some the HI is reduced to I2 (say by air), then in the presence of excess H2C2O4, upon shaking to capture the Iodine, it is possible that
Hydroiodic acid could be reformed. See the implied net ionic equation at http://www.sciencebuddies.org/science-fair-projects/project_... , namely:
C2O4- + I2 → 2 I- + 2 CO2
I, by the way, completely believe the properties of Citric acid in a boiling concentrated salt solution as ionic water-stressed environments can
increase the 'activity level' of weak acids, or dilute solutions of a strong acids. Now, the heating of the hydrated Oxalic acid with NaCl, for
example, is in my opinion, not too dissimilar from such an ionic water-stressed equilibrium reaction.
