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thesmug
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Removal of gasses
I remember reading somewhere that you can get rid of the gasses (say chlorine, for example) produced by a reaction by bubbling them through water,
thereby dissolving them in the water. Does this actually work? And if so, is there any special procedure for this?
Also, this is probably in the wrong forum. If it is, please direct me to the correct one  .
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elementcollector1
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Depends on the solubility of the gas in question.
A better way to get rid of them is by reacting them off - Cl2 into NaOH or Na2CO3 solution, etc.
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Zyklon-A
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This the right forum to post a question like this... Although since it's short, the short questions thread would have been a wiser chose.
For Cl2 I would bubble in though NaCO3 or NaHCO3. It will make NaOCl and CO2.
2 NaCO3 + Cl2 --> 2 NaOCl + 2 CO2. And as a plus you get some NaOCl (sodium hypochlorite AKA bleach)
[Edited on 4-2-2014 by Zyklonb]
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violet sin
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you only have a few posts here so I'll give you some pointers, ok.
did you do a google search of any kind? different types of gas may be absorbed by different means, so unless you need to know about chlorine
specifically, the answer may be different in each case. as a rule it is important to do some investigation first. if you just want a quick answer
for a simple question try the "The Short Questions Thread (4)" https://www.sciencemadness.org/whisper/viewthread.php?tid=25...
navigating from sciencmadness.org main page you see the fundamentals category at the top --> chose the miscellaneous section --> to the green
labeled thread second form top "The Short Questions Thread (4)"
for a search on this site to see if others have asked the same question, select the "search" function on the left of the header bar at the top of the
screen, just below the scimad logo. be careful with spelling also.
read up and report back with a more detailed question or a description of where you have trouble understanding the subject. while your at it, read up
on the forum guide lines for posting please https://www.sciencemadness.org/whisper/viewthread.php?tid=19...
this is in the beginnings section so it's not like you had to provide linked papers for the discussion. but it is kinda poorly worded and broad
question to be answered easily, other than yes, some gasses can be stripped in a number of manners. the real questions start to appear when you look
at it in a bit more detail. how much can be captured in a volume of water/etc.? how efficiently does it absorb in one pass? what is the best
temperature to do it at? will I run into issues with the solution getting sucked back into my reaction vessel? and many many more.
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thesmug
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Ok, it seems, from what you guys have answered, that this isn't a guaranteed way of disposing of gas. I will try some of what you guys suggested.
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elementcollector1
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Again, it depends on what gas...
Elements Collected:52/87
Latest Acquired: Cl
Next in Line: Nd
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Zyklon-A
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Just go to Wikipedia and look at the page of the gas in question, on the right side it will show the solubility data, make a decision based on that. No, it
is not a guaranteed way of disposing of any gas.
[Edited on 4-2-2014 by Zyklonb]
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violet sin
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I believe there is more to it than that Zyklonb. not trying to be rude, just saying teach a man to fish and you won't have to feed him every night.
new members could use more tips on how to find stuff them selves, resources to harness, and such. I don't think jumping to wikipedia and hoping it
has solubility data would be the best route. nor lead to the greatest understanding of the principles at play.
not a BAD way to go per-se for a quick check. just remember new members aren't always aware of many of the things established members use to dig up
data, Google - scholar search, patent search, yes *wikipedia*, short question thread, free e-books and more.
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Brain&Force
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For differently reacting gases, it's best to bubble them through a solution of some sort. Reducers (and some oxidizers) such as nitrogen dioxide and
sulfur dioxide can be bubbled through 30% hydrogen peroxide. Acidic gases like HCl should be bubbled through a base like ammonia and basic gases like
ammonia should be bubbled through an acid like vinegar.
Chlorine can be fixed into solution by bubbling through a solution of a iodide salt. A single replacement occurs and iodide is oxidized to triiodide
while chlorine becomes chloride.
At the end of the day, simulating atoms doesn't beat working with the real things...
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woelen
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The last suggestions are not very practical. They are expensive.
NO2 and SO2 can be scrubbed by a solution of NaOH or even Na2CO3.
HCl and other acidic gases/vapours can also be scrubbed by NaOH or Na2CO3
Ammonia and other basic gases (e.g. vapours of amines) can be scrubbed by dilute acids. Many of them can even be scrubbed by water.
Cl2 can best be scrubbed by NaOH, using iodide is way too expensive.
Mixes of NO and NO2 are harder to scrub. NO does not react with NaOH, but it does react with oxygen from air. very easily. You could pass this into a
big bottle with air and a little amount of a solution of NaOH to scrub it. This construction, however, requires manual handling of the scrubber every
few minutes (depending on the amount of gas produced in the experiment). A workable solution is to use two such bottles and change them every few
minutes as long as the flow of gas still is strong. Yet another option may be to pass in air as well (e.g. using an aquarium pump) and scrub the mix
of air and gas.
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confused
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how about degassing it in a vacuum chamber?
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smaerd
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I'll just mention of the stuff about scrubbing gases I have learned that hasn't already been mentioned here.
Sodium thiosulfate can remove solvated oxygen in water to some extent.
Another way to remove oxygen and other gasses is boiling/vacuum purging followed by sparging with an inert gas(Nitrogen, Argon, etc). For HPLC
solvents Helium seems to be preferred. Another nifty method is by using ultrasound.
Scrubbing gaseous amines can be done by passing the air through calcium chloride. Calcium chloride can also remove some water vapor from air.
Some organic vapors can be scrubbed by passing the effected air through a plug of activated carbon. Seems to work with aromatics such as toluene or
xylene quite well. Very nice tip for stinky reactions and no fume-hood.
Again, of course this all depends on many factors. Concentration of the gas, desired end concentration of the gas, flow velocity, etc, etc, etc.
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Fantasma4500
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NH4OH solution, weak
even if any gas manages to escape the solution the NH3 above the liquid will catch it and form smoke
some hate NH3 and some love it, myself i find it as being the chemical of possibilities
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Zyklon-A
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| Quote: |
I don't think jumping to wikipedia and hoping it has solubility data would be the best route. |
True, although wikipedia does have solubility data on most gasses, it may not have it on all. Moreover, even if a gas is quite soluble, it likely
wont dissolve quickly enough, an exception would be NH4, which the bubbles will collapse almost immediately.
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DraconicAcid
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Quote: Originally posted by woelen  | | Mixes of NO and NO2 are harder to scrub. NO does not react with NaOH, but it does react with oxygen from air. very easily. You could pass this into a
big bottle with air and a little amount of a solution of NaOH to scrub it. This construction, however, requires manual handling of the scrubber every
few minutes (depending on the amount of gas produced in the experiment). A workable solution is to use two such bottles and change them every few
minutes as long as the flow of gas still is strong. Yet another option may be to pass in air as well (e.g. using an aquarium pump) and scrub the mix
of air and gas. |
Would a solution of bleach work? It should oxidize the NO to NO2 easily enough, and the basic solution should turn that into nitrate.
Although one might want to add extra base to it, since you wouldn't want your bleach getting too acidic.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Zyklon-A
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According to Wikipedia, NaOCl(aq), has an Acidity (pKa) of >7.
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testimento
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Depending on the concentration and toxicity of gases. I scrub highly toxic gases into proper solution, like chlorines into NaOH and cyanides into
basic hypochlorite. Less toxic gases I purify with active carbon and then exhaust them outside with line fan. Very large quantities of gases or moist
fumes will consume the carbon so I will exhaust them directly.
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DraconicAcid
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I think you'd better read something other than Wikipedia, such as looking up what exactly pKa is.
Bleach, for those who do not know, is a basic solution of sodium hypochlorite (sometimes calcium hypochlorite). if you were to pass a mixture of
nitrogen oxides through it, the bleach should oxidize the NO and NO2 into nitrate ions, but this will also generate hydrogen ions/consume
hydroxide ions.
H2O + 2 NO2 +OCl- --> 2 H+ + 2 NO3- + Cl-
H2O + 2 NO + 3 OCl- --> 2 H+ + 2 NO3- + 3 Cl-
As the hydrogen ion concentration increases (or, rather the hydroxide ion concentration decreases), the solution becomes more acidic. Under acidic
conditions, hypochlorite ion reacts with chloride ions in solution to give chlorine gas, which isn't any better than the nitrogen oxides we're hoping
to scrub out of the gas mixture anyway.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Zyklon-A
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DraconicAcid, " I think you'd better read something other than Wikipedia, such as looking up what exactly pKa is.''
I know what pKa is.
Sorry, I should have explained better, Wikipedia said "The pKa of NaOCl(aq), is >7.
What I was implying, is, it is just a little basic, like you said.
[Edited on 4-2-2014 by Zyklonb]
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Brain&Force
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Wouldn't this produce aqua regia, and therefore nitrosyl chloride? That's yet another problematic gas.
For NO2, it's best to use hydrogen peroxide. It can be recycled into nitric acid. Water also works for this, but it converts the nitrogen
dioxide to nitric and nitrous acids instead.
As for nitric oxide, I would assume the same would work, but I'm probably wrong on this.
At the end of the day, simulating atoms doesn't beat working with the real things...
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DraconicAcid
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| Quote: Originally posted by Zyklonb | DraconicAcid, " I think you'd better read something other than Wikipedia, such as looking up what exactly pKa is.''
I know what pKa is.
Sorry, I should have explained better, Wikipedia said "The pKa of NaOCl(aq), is >7.
What I was implying, is, it is just a little basic, like you said.
[Edited on 4-2-2014 by Zyklonb] |
Sodium hypochlorite does not have a pKa, as it is not an acid. A solution of bleach will have a pH, which is a completely different measurement.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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DraconicAcid
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Not in dilute aqueous solution, and certainly not if it's kept basic.
| Quote: | For NO2, it's best to use hydrogen peroxide. It can be recycled into nitric acid. Water also works for this, but it converts the nitrogen
dioxide to nitric and nitrous acids instead.
As for nitric oxide, I would assume the same would work, but I'm probably wrong on this. |
That may be right- I'm just not sure how quickly NO will react with either oxidizing agent.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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Zyklon-A
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Well, I just copied and pasted information from wiki, I guess that's why you said, "I think you'd better read something other than Wikipedia".
[Edited on 4-2-2014 by Zyklonb]
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Brain&Force
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http://www.youtube.com/watch?v=2yE7v4wkuZU
Making nitric acid with the NO2 - peroxide method.
At the end of the day, simulating atoms doesn't beat working with the real things...
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woelen
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The gas NO hardly dissolves in water and that makes it problematic. Indeed the oxidation of NO by bleach may work, but even then it may be too slow
(the gas does not dissolve easily, so the main reaction must be at the interface between the gas bubbles and the surrounding liquid). I can imagine
that if the gas is very finely dispersed (e.g. using an aquarium bubble stone) and it is allowed to bubble through a long narrow column of bleach that
it works.
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