dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
ClO2 from H2SO4 + NaCl
Hello,
I want to produce Chlorine Dioxide from Sodium Chlorate (or Potassium Chlorate) + acid + NaCl.
Not to sure how exactly to do it, but most suggestions use Sulphuric acid. Will HCl do instead of the Sulphuric.
What amounts of Chlorate + Acid + NaCl do I use.
Thanks,
Dann2
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
In order to get ClO2 you MUST have chloride as well in the mix. Best is to use HCl in combination with NaClO3 (or KClO3), but you can also use H2SO4,
but then you have to make a mix of NaCl and NaClO3 and add the acid to this. Assure that the H2SO4 is not too concentrated, otherwise you also will
have a lot of HCl in the gas mix.
Keep in mind though that the ClO2 made in this way is very impure. You will get a mix of Cl2 and ClO2. If you want pure ClO2, then you need to mix
chlorite instead of chlorate with HCl or NaCl/H2SO4.
|
|
|
Formatik
National Hazard
Posts: 927
Registered: 25-3-2008
Member Is Offline
Mood: equilibrium
|
|
Here's a procedure cited by Gmelin: The same volume aq. dilute HCl or 2 vol. aq. dilute H2SO4 is added gradually to a flask containing a mixture of 5
parts KClO3 and 12 parts NaCl. The mixture of Cl2 and ClO2 which forms at room temperature, or upon mild heating is lead through a few cubic
centimeters of water to absorb the HCl, and then through a tube containing CaCl2.
From the mixture it is possible to condense the ClO2 so the liquid results and get it pure, as further described in Pebal (Lieb. Ann. 177 [1875]12),
where the procedure is from. But liquid ClO2 is highly reactive, extremely dangerous and bizzarely shock sensitive. Cork and rubber should be avoided
since they initiate ClO2. Strong daylight also does the same.
|
|
|
chief
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
"bizarrely shock sensitive" == high or low explosive ?
How does the ClO2 react with Na2CO3 or NaOH ? To chlorate ? And how with Ba(OH)2 ? To Ba(ClO3)2 ?
Can I avoid the tedious crystallizations of the chlorates this way ? Ba(ClO3)2 directly from the unrefined NaCl/NaClO3-satlmixture of brine, just by
reacting it with HCl and letting the gases bubble through hot Ba(OH)2-solution, which should convert the chlorine as well to chlorate ?? Then I would
have an easy way to Ba(ClO3)2, the "king of chlorates" from the viewpoint of reacting with any sulfate-solution to form insoluble BaSO4 and the
according chlorate ...
That sounds like avoiding several crystallization-steps (first NaClO3 out of brine, then BaClO3 out of some double-decomposition ...) ...
What are the hazards of ClO2 ?
Edit: It seems to be quite explosive as gas: More than 15%wt in air and its sensitive to light ... : http://en.wikipedia.org/wiki/Chlorine_dioxide
Another source states: Explodes above 60 [Celsius] : http://www.zeno.org/Meyers-1905/A/Chlordioxyd
So it usually is handled in solution ... of up to 10 gm /liter ... . Not very much ! Will the initial ingredients (NaClO3 + HCl) react in such low
concentrations as necessary to have only 10 g/l of final solution ?
[Edited on 26-3-2009 by chief]
|
|
|
Formatik
National Hazard
Posts: 927
Registered: 25-3-2008
Member Is Offline
Mood: equilibrium
|
|
| Quote: | | "bizarrely shock sensitive" == high or low explosive ? |
High; trauzl tests place liquid ClO2 between 1/3 to 2/3% of TNT. This and its sensitivity is enough to categorize it (at least the liquid) amongst
primary explosives.
| Quote: | | How does the ClO2 react with Na2CO3 or NaOH ? To chlorate ? And how with Ba(OH)2 ? To Ba(ClO3)2 ? ... |
With OH- or CO3- in aqueous solution you'll get a mixture of chlorite and chlorate. NaClO2 is shock sensitive. Ba(ClO2)2 is explosive. Mixing would
require dilute solutions since, conc. ClO2 solutions also heat up with conc. KOH solutions, a lot of ClO2 is liberated and easily an explosion can
occur, where liq. ClO2 detonates on contact with solid KOH.
| Quote: | | What are the hazards of ClO2 ? |
Generally, it's sensitive to shock, strong light, heat, electrostatic shock. Liquid ClO2 explodes easily from insignificant mechanical disturbances,
e.g. if a drop of it falls from a height of about 20cm into a glass, Brandau (Lieb. Ann. 151 [1869] 346). ClO2 explodes on contact with cork or
rubber, Schacherl (Lieb. Ann. 206 [1881] 69). ClO2 reacts explosively with several materials, esp. organics. The gas also explodes on slight
provocations, so it is vital to have it diluted. Even 10% in air mixtures at 0.1 bar partial pressure can explode from sunlight, heat, or
electrostatic discharge.
|
|
|
JohnWW
International Hazard
Posts: 2849
Registered: 27-7-2004
Location: New Zealand
Member Is Offline
Mood: No Mood
|
|
The stuff is also highly toxic on inhalation, and probably carcinogenic on skin contact, like other oxidizing volatile substances with an unpaired
electron, such as NO2, NO, ClO; and also like O3 which decomposes yielding atomic oxygen, and gaseous F2 and Cl2 and Br2 which easily decompose to the
atomic species.
|
|
|
Formatik
National Hazard
Posts: 927
Registered: 25-3-2008
Member Is Offline
Mood: equilibrium
|
|
Yeah, ClO2 is also highly poisonous. In dilute amounts it does smell pleasant though, unlike Cl2 which smells like hell. ClO2 has a burnt sugar twist
to its halogen odor.
[Edited on 27-3-2009 by Formatik]
|
|
|
dann2
International Hazard
Posts: 1523
Registered: 31-1-2007
Member Is Offline
Mood: No Mood
|
|
Hello,
Thanks alot for answers. Just what I was looking for.
I believe ClO2 is used for poisoning/gassing rats! Not a pretty thought.
Dann2
|
|
|
garage chemist
chemical wizard
Posts: 1803
Registered: 16-8-2004
Location: Germany
Member Is Offline
Mood: No Mood
|
|
Quote: Originally posted by Formatik  |
| Quote: | | How does the ClO2 react with Na2CO3 or NaOH ? To chlorate ? And how with Ba(OH)2 ? To Ba(ClO3)2 ? ... |
With OH- or CO3- in aqueous solution you'll get a mixture of chlorite and chlorate. NaClO2 is shock sensitive. Ba(ClO2)2 is explosive. Mixing would
require dilute solutions since, conc. ClO2 solutions also heat up with conc. KOH solutions, a lot of ClO2 is liberated and easily an explosion can
occur, where liq. ClO2 detonates on contact with solid KOH.
|
I want to add that if one adds hydrogen peroxide to the NaOH that is used to absorb the ClO2, pure chlorite solutions result. This is the industrial
method to manufacture sodium chlorite.
2 ClO2 + 2 NaOH + H2O2 ---> 2 NaClO2 + 2 H2O + O2
If no H2O2 is added, a mix of chlorite and chlorate results, since ClO2 is the mixed anhydride of chlorous and chloric acid.
Sodium chlorite is sometimes said to be "explosive". However, Ullmann says that the solid is not shock sensitive when organic matter is completely
excluded.
NaClO2 is commonly sold as either an 80% solid (rest "stabilizers" according to Ullmann) or an aqueous solution, of which I have some (it is greenish
and smells like ClO2). NaOH is always present in the commercial products since chlorite is more stable in alkaline solution.
Heavy metal chlorites, like lead and silver chlorite, are insoluble and highly explosive. The yellow lead and silver salts are characteristic for
chlorous acid.
ClO2 free from Cl2 can be made is reducers like SO2 or methanol are added to the aqueous H2SO4 + NaClO3 reaction. I cite Ullmanns Encyclopedia on
manufacture of ClO2 (diluted with enough air to be nonexplosive) as an intermediate to NaClO2:
| Quote: |
5.2.3. Mathieson Process
Sulfur dioxide is the reducing agent in the Mathieson process. The main overall reaction is as follows:
2 NaClO3 + H2SO4 + SO2 ¾® 2 ClO2 + 2 NaHSO4
Solutions of sodium chlorate and sulfuric acid are added continuously to a relatively large, cylindrical, lead-lined tank (primary reactor) from the
top. Sulfur dioxide, diluted with air, is introduced through gas diffusion plates at four points in the bottom of the tank. The reaction mass
overflows to a smaller secondary reactor of similar construction. The generated chlorine dioxide still contains some unreacted sulfur dioxide; it is
stripped from the reaction mass by air and then washed in a scrubber packed with Raschig rings. The scrubber is installed on top of the primary
generator, and the fresh sodium chlorate solution serves as a washing liquid on its way down to the primary generator. The mixture of chlorine
dioxide, air, and chlorine coming out of the scrubber goes to the absorption tower.
5.2.4. Solvay Process
The Solvay process uses methanol as reducing agent. The main overall reaction is as follows:
2 NaClO3 + CH3OH + H2SO4 ¾® 2 ClO2 + HCHO + Na2SO4 + 2 H2O
The reaction between sodium chlorate, methanol, and sulfuric acid takes place in two jacketed, lead-lined steel reactors. The chemicals are added to
the bottom of the first vessel and flow by gravity from one reactor to the other. Each vessel has its own supply of methanol and air. The two reactors
are operated at different temperatures and chlorate concentrations. Up to 70 % of the reaction is completed in the first reactor. Additional methanol
and up to 10 % of the total acid requirement is fed to the second reactor; the conversion of chlorate is then more than 95 %.
|
As a lab procedure, oxalic acid is commonly used as a reductor, the resulting ClO2 is then automatically diluted with CO2. For details see Brauer.
But this is not too useful since the CO2 would result in carbonate if absorption in NaOH/H2O2 is desired.
|
|
|
chief
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
If I just want a mild disinfecting solution of the ClO2: Will the reaction occur if eg. 1 l H2O with 20 g NaClO3 and maybe 20 g HCl is mixed ? Or has
it to be done with the concentrated educts and then dissolved in H2O ?
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
The last thing is better, but the dilute solutions also will do. The reaction will be slow in that case. You can see the formation of ClO2, the liquid
becomes bright yellow.
|
|
|
chief
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
I tried it: Conc. brine directly from electrolysis, HCl (together 100 ml), given into 400 ml of medium-hot water. NOthing yellow even after 2 hours,
no chlorine-like smell, no hypochlorite-like bleaching-action ... . It failed so far !
Sure It should work ???
|
|
|
woelen
Super Administrator
Posts: 7977
Registered: 20-8-2005
Location: Netherlands
Member Is Offline
Mood: interested
|
|
How long did you do the electrolysis and what current was running through the cell? Keep in mind that electrolysis is a slow process. Suppose you were
running at 1 A, then you need almost one week to obtain 1 mole of chlorate! At 10 A you still would need 16 hours or so to get 1 mole of chlorate.
With these figures I also assume no loss of chlorine by bubbling of chlorine gas out of solution and no loss of chlorate and hypochlorite by
back-reduction at the cathode. So in practice the times needed will even be somewhat longer.
[Edited on 3-4-09 by woelen]
|
|
|
chief
National Hazard
Posts: 630
Registered: 19-7-2007
Member Is Offline
Mood: No Mood
|
|
The stuff is conc. solution of 50% NaCl/ 50% NaClO3, which I confirmed microscopically, by the indexes of refraction (1.5442 NaCl, 1.5151 NaClO3) (and
the cell was run for a week at 70 A, consuming 6 self-made 13mm-PbO2-Anodes).
Also I did, in between, some other experiment: The dried salt-mixture of the mentioned composition,
==> which indeed acts as oxidizer (for testing this I mixed _raw_ particles with some saw-dust, nothing finely milled, small amount, so no danger)
==> and contains therefore real chlorate
was mixed with H2SO4 in presence of water:
==> A plastique-jar with 400 ml H2O (warm)
==> a raw piece (maybe 10-20 g) of the chlorate/chloride-mixture into it, so it would be on the ground, the 400 ml H2O above it
==> H2SO4 (20-30 ml) (this time H2SO4, because _this_ should be capable ) conc. (96 %) was added, in a way that it sunk directly to the ground,
where the NaClO3/NaCl-rock was waiting for it, so that the stuff could react in better concentration, but safely shielded and throttled by the 400 ml
H2O above it, which would take up any runaway automagically and also would dissolve the ClO2/Cl gas-mixture.
What happened was that initially a slight chlorine-smell appeared, but then nothing followed. No result, as above with the HCl-acid. Maybe that there
is some minimum conc.-requirement ?
[Edited on 3-4-2009 by chief]
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
