Blind Angel
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Hydrogen chloride from hydrogen and chlorine gas
I thought aboute making HCl with H2 and Cl2 but when I asked to my chem teachers she told me that i would be too dangerous and make a big explosion.
So 2 questions came:
1 - Why%
2 - Is there anotehr way to do it%
[Edited on 24-1-2014 by ScienceSquirrel]
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lucifer
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H2 and Cl2 will react violently if exposes to UV
See experiment http://chemed.chem.purdue.edu/demos/main_pages/22.10.html
Much saver to produce HCl is:
When Chlorine Water (i.e. a solution of chlorine gas in water) in a flask inverted in a basin of the same liquid is exposed to bright sunlight, the
Chlorine is decomposed and a solution of Hydrochloric Acid remains.
H2O + Cl2 ==> HCl + HClO
The Hydrochloric Acid, HClO, is not very stable and the solution readily decomcomposes, especially when exposed to sunlight, yielding Oxygen.
2 HClO ==> 2 HCl + O2
So don’t need the H2
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rikkitikkitavi
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Industrially , HCl is made by burning H2 and Cl2 in a burner made out of quartz, one of the few materials resistant to hot HCl gas (flame temperature
is very high)
Multiple failsafe devices are also used to monitor the flame, so that the feed is shut off instantly if the flame goes out.
Note that a Cl2+H2 flame is hard to see , beacause little light is emitted in the visible range, much like a H2+ O2 flame.
For the same reason the burner is always placed in the open, with only a roof to shelter it so an explosion will only destroy the burner itself.
From this it is quite clear that building such a device is not a simple task.
/rickard
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Blind Angel
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Chlorine Water
Like the one in swimming pool?
(Saturate water with pellet then applying the process described)
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Polverone
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Different products are used to chlorinate swimming pools. Not very many of them would be a good starting point to make HCl. If you want HCl and can't
just buy it, I suggest that you look at some of the fertilizer information rickard has been posting. Or are these just theoretical questions?
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Blind Angel
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A bit of the two siince i dont have any budget.
Thx I will look on fertilizer i have at home
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madscientist
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Hydrochloric acid could be prepared from pool chlorine - the solid calcium hypochlorite type.
The calcium hypochlorite would be heated to decomposition, and the gas generated, probably Cl2O (see the "hypobromite" thread for why I
think hypochlorites decompose in such a manner - I'm not 100% certain that my hypothesis is correct), is bubbled through water, yielding a solution of
HCl and HOCl. The hypochlorous acid would then be decomposed into hydrochloric acid via the method previously suggested.
I weep at the sight of flaming acetic anhydride.
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madscientist
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I meant to say "a solution of HOCl", not "a solution of HCl and HOCl". My fingers sometimes seem to have a mind of their own...
I weep at the sight of flaming acetic anhydride.
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Marvin
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H2 + Cl2 can be done at home quite safely, its just a question of knowing how. If you mix several litres of both gases and apply UV, a spark or a
match you will get a sizable explosion, how ever a test tube of the mix, or of hydrogen/oxygen is considered quite safe.
The trick is to collect both gasses seperatly from the electrolysis cell, have them both jet close to one another in a small container having trapped
air over the water you want to make aq HCl from. Next to the jet can be aranged a spark circuit of the type from gas ovens, not of the piezo type,
producing a spark every 0.5 to 2 seconds.
Important things to note. The combination container is kept small volume and at any point contains mostly inert gas (nitrogen from the air at the
start of the experiment, the gas mix will fractionally, and unavoidably have hydrogen in excess which will remove the oxygen), even if the jet fails
to ignite at any point and it fills with explosive insoluable gas mix, the resulting pop will be too feeble to damage anything. In the event of no
ignition at all the gas will simply bubble out of the liquid in small amounts and diffuse into the air. Its very hard to create an electrolysis
cell/power supply powerful enough to make a long burning jet, it will probably burn in a series of tiny pops, the heat of the flame is simply not an
issue at this scale. The volume of gas produced by the system will not be a threat to anything provided this is done with reasonable ventilation,
required anyway becuase of the HCl/Chlorine.
Making the cell to produce the H2 and Cl2 is slightly more difficult, the anode needs to be graphite and will erode fairly quickly in the high
hydroxide concentrations. Keep the gas connections short and thin and ignition wont be a problem even in the event of a small amount of
contamination. Try with a fairly low current power supply to start with, say a few amps, and if the amount of HCl is too small, work your way up.
A good design for the cell would involvethe liquid around the cathode dripping out of the cell, containing most of the hydroxide produced, while
saturated salt solution drips into it. If a suitable material for a diaphram could be found this would help a lot, and enable the salt to be
completely decomposed into sodium hydroxide and chlorine. If HCl is the main goal, this is not really a problem and a diaphram would increase the
resistance of the cell, salt is very cheap and a simple cell with two vertical electrodes works fine. The liquid will get quite hot, contain sizable
amounts of hydroxide and will attack glass slowly. You can make the whole cell out of glass, but it will end up having a 'frosted' look and wont be
useful for anything else. A sheet of white paper behind the cell will alow the colour of the chlorine to be seen and when it starts to fade the
solution can be discarded for more concentrated salt solution.
Build the cell well enough so it doesnt require babysitting. Exposure to small amounts of HCl/Chorine over long periods are the only major risks in a
well thought out cell. Good insulation out of something that will not be wet by water will insure that splashes of solution wont short the spark gap,
this is only mildly anoying due to loss of HCl.
I would strongly suspect that heating a hyperchlorite will only produce oxygen in anything other than useless amounts. Heating hyperchlorite solution
in the prevailing alkaline conditions only produces a little oxygen and some chlorate in higher concentrations and at higher temperatures. Attempting
to oxidise hyperchlorites with peroxides for example only produce oxygen. The only way to get chlorine from them is by making a
hyperchlorite/chlorine solution acidic. Cl2O might be persuaded to form in an acidic solution with no chloride ions, but not in alkaline. I'm
currently unaware of any major exceptions to this for bromine, but I'll check the thread anyway.
Water doesnt dissolve much chlorine, hyperchlorite forms a very weak acid, so this is not present in anything but tiny quantities and the amount and
concentration of HCl you could make by explosing this to sunlight would be nothing short of miniscule. Sunlight catalysed reactions only work in
preperative amounts if they initiate a free radical chain reaction, which wont happen in aq solution. It could be decomposed in other ways but this
isnt going to work for concentrated HCl solutions.
The only way round burning H2 and Cl2 I can see is by generating it from salt and some other acid, maybe from acetic, but organic acids are very weak
and this doesnt seem likley to work for conc HCl.
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khlor
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So, Gentlemen,
If I would be mad enough to carry out such experiment. I mean, get H2 and Cl2 put each one in a separated flask, find a way to put them together under
sunlight I could make fine and almost pure HCl, is that right? with, of course, the risk of an explosion. and if everything goes right(well what can
goes wrong? - being ironic) I could make the resulting gas pass through destilled water and get my hydrogen chloride in solution.
well for me sounds fair enough to give it a try. since I just need UV light and not necessarily heat from a flame to burn the mixture.
I don't know but I really would like to try this.
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elementcollector1
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Technically, yes - but do you understand what an 'explosion' is?
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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phlogiston
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Quote: Originally posted by khlor  |
well for me sounds fair enough to give it a try. since I just need UV light and not necessarily heat from a flame to burn the mixture.
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I am surprised you find this an important consideration. The technical difficulties involved in generating, storing and handling the gasses are much
worse than what method you will use for igniting the mix.
And I would certainly not rely on sunlight. You don't want to have these gasses or the mixture accumulate if it doesn't reliably ignite on a clouded
day.
Youtube link:igniting Cl<sub>2</sub> + HCl<sub>2</sub> in a quartz test tube with a UV LED
[Edited on 24-1-2014 by phlogiston]
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"If a rocket goes up, who cares where it comes down, that's not my concern said Wernher von Braun" - Tom Lehrer |
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khlor
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Now the thing gets interesting... I live in brazil, and the UV LED here has the name of "black light LED" I suspected some times, but I didn't gave
importance, not until now. now I realise I do not need sunlight to trigger the reaction. but I believe the real reason you show the video is because
you wanna show the technical dificulties when you are dealing with glass and explosive mixtures isn't? but anyway the video was very, very
interesting.
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blogfast25
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| Quote: Originally posted by Marvin | | The only way round burning H2 and Cl2 I can see is by generating it from salt and some other acid, maybe from acetic, but organic acids are very weak
and this doesnt seem likley to work for conc HCl. |
Conc. H2SO4 displaces HCl (which of course is volatile, that helps a lot) in NaCl easily. There are quite a few descriptions on the forum for H2SO4(l)
+ NaCl(s) === > NaHSO4(s) + HCl(g) based HCl generators, with good percentage yield on modest heating of the mixture.
It once was (maybe still is to some extent) a major industrial route to HCl.
[Edited on 24-1-2014 by blogfast25]
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AJKOER
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First, I suspect your Chemistry teacher is more of an educator than a chemistry professional (perhaps the reason why many countries are rising in
math and science education while others are falling). A case in point, a Hong Kong magnum high school that I once happen to stumble onto online (as a
result of an internet query on a particular reaction that hit on one of their homework pages), was impressive to me by the level of its homework. I
also noted that all the science professors have advanced degrees in their respective fields along with some years of actual commercial experience (a
model to follow, IMHO, if one actually wants its students to excel in science).
Now, one the reasons I make my claim is because if your teacher had advanced studies on the topic of chain reactions, the H2 and Cl2 is one of a few
examples that is often presented. In this interesting particular chain reaction mechanism, the presence of oxygen induces an alternate non-explosive
chain (a source "Chemical Kinetics and Reaction Dynamics", edited by Santosh K. Upadhyay, pages 119 to 120 at http://books.google.com/books?id=nirXFo1S9VkC&pg=PA119&a...). Bottom line, a small amount of O2 will poison the chain preventing a detonation
with uv light.
Second clue, there is at least one company online that markets high purity HCl from the direct combustion of H2 and Cl2 (which is very hot flame, but
not particularly dangerous). The process is obviously more costly and otherwise not commercially viable (in agreement with Blogfast alternate
commercial routes to HCl).
--------------------------------------------------------
Some documentation, on the high school reference, per an old SM thread (link: http://www.sciencemadness.org/talk/viewthread.php?tid=21595 ), to quote:
| Quote: Originally posted by AJKOER | OK, I have actually find a reference via an answer sheet available online as a pdf from one of the 12 Microsoft® Innovative Schools worldwide, and is
the only one in Asia (see http://www.microsoft.com/casestudies/Microsoft-Windows-XP/Fu... ), that confirms my reaction products. To repeat my speculated reaction equation:
2 SCl2 + 4 H2O --> 4 HOCl + 2 H2S --> 2 HOCl + 2 HCl (g) + 2 H2O + 2 S (c) --> 4 HCl (g) + 2 H2O + SO2 + S (c)
or, upon eliminating 2 H2O from the first and last equations:
2 SCl2 + 2 H2O --> 4 HCl (g) + SO2 + S (c)
The attached answer sheet pdf file reference from the Fungkai School (HK) on page 4 states to quote:
" For SCl2 + H2O -> HOCl + HSCl (or accept S + SO2 + HCl )"
....................
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Interestingly and a related to my point, questionable reaction products were cited (I will not reproduce the nonsense here) from one educator's
homework site and have, as its only reputed source, another published educator's textbook. However, the distinguished scholars at The Fungkai School
and I, apparently agree on the products.
[Edited on 24-1-2014 by AJKOER]
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blargish
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I believe that HCl gas can also be made by heating a mixture of solid sodium bisulfate and sodium chloride. This is easy since it is very simple to
obtain both of these chemicals. The reaction is as follows:
NaHSO4 (s) + NaCl (s) --> HCl (g) + Na2SO4 (s)
I have used this method before in preparing hydrochloric acid.
However, I have found the sulfuric acid route to be much more effective at generating HCl.
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