Roachburn
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building a filter
I plan on doing a few common experiments you see on the net these days, however, I want to be safe and I don't have a fume hood to filter the
gases.Then I saw a video about making nitric acid and the guy bubbled the excess nitrogen dioxide into a solution of sodium carbonate. Could this be
used to filter out other harmful gasses from other types of reactions. What about using activated carbon in a pvc pipe as a filter. Are there any
other gasses would i not want to try to filter by this method, due to possibly creating other unwanted toxins? Could I use multiple tubes with
different material to filter? For example I could maybe first send it through the activated carbon tube, then bubble into sodium carb or something.
Would I want to change it up depending on the reaction? What other chemicals would be good for filtering gases? I want to be as safe as I can because
for me and I think most others, safety is the most important thing. Whenever I do an experiment, I start off very small to limit the hazards. Then
once I know what to expect from the reaction I scale it up if necessary. If I need a large quantity of something, then I make multiple small batches.
I also always use gloves and eye protection and splash protection or face shield if necessary. I also do as much research on the reaction I want to do
and research any chemical used or created by the experiment. This being said, any further safety advice is appreciated. Some experiments I plan on
doing are: Synthesizing hydrochloric acid, sulfuric acid, and nitric acid. Also alot more of nurdrage's experiments. Some of the gasses I am worried
about are: Cl, H2S, HCl, SO2, NH3, and NO2. Any advice on how to build a good filter that would be good for multiple gases would be great. Also any
advice on things not to mix together would be good. What I mean is lets just say that I make a carbon filter and I do one experiment and trap the
gasses in the tube, then later do another experiment and the gasses mix making an even more dangerous or even explosive substance. Definately dont
wnat that. Thanks.
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hissingnoise
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| Quote: | | Also any advice on things not to mix together would be good. |
Finding simple info like this yourself by a quick websearch would be better don't you think . . . ?
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Roachburn
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The only thing that comes up is not to mix bleach and ammonia, which I already know. I already tried to search for this information. That is how I
found that video on filtering NO2 and using carbon. What I want to do is build a series of pipes with layers of carbon, NaOH, and sodium carb.
solution and hopefully filter out any gas from any possible reaction I would be doing. What I don't know is how effective this will be.I was hoping
someone would know more about these different gasses I have named and whether or not this device I build will be sufficient. Also as this filter gets
used and accumulates different chemicals I don't want anything to react in a bad way. I don't think this is basic everyday knowledge.
[Edited on 3-11-2011 by Roachburn]
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bob800
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Personally, I see no reason to build a complicated multi-stage filter. Just bubble the gas through a gas-washing bottle (of course you will need to
change scrubbing solutions depending on your experiment):
This can be easily made from an Erlenmeyer flask and some glass tubing.
For large amounts of gas, just hook up more bottles to the chain. For most acidic gasses, like HCl, Cl2 (which forms hypochlorous acid when dissolved
in water), SO2, or SO3, use a strong alkali solution, like sodium hydroxide. This is excellent for scrubbing many different gasses. NO2 should also be
neutralized, but I've also heard of urea being used.
<s>For ammonia, use an acid, such as hydrochloric.</s> I believe hydrogen sulfide can be filtered using a bleach scrubber, though you
should be extremely careful, because there have been many incidents of hydrogen sulfide desensitizing the sense of smell. I really would not
recommended H2S production for a beginner.
I do not have experience using activated carbon, but it seems to me that a washing bottle would be much more effective.
A "things not to mix" list would span several pages if everything was included. However, if you are aware of the reaction and its properties, then
chemicals that would otherwise be dangerous to mix can be safely controlled. For example, everyone knows that mixing ammonia and bleach produces
many toxic gasses, none of which are good for your health. But if you keep this in mind and scrub the gasses before they escape, this would be just as
dangerous as mixing vinegar and baking soda.
Even so, sometimes there may be nasty side reactions that you don't know about. Here's a list of some common incompatibilities: http://chemistry.about.com/cs/toxicchemicals/a/aa603003a.htm
Finally, there is no better way to stay safe than to READ. I have learned the most safety info from this forum alone. If you browse around and do some
searching, you will find some of the best safety advice on the net.
[Edited on 4-11-2011 by bob800]
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UnintentionalChaos
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Unless you're fishing for suckback problems, I would strongly advise against using acid traps for ammonia. Cold water is more than sufficient as
ammonia is extremely soluble in it and the risk of suckback is lower.
Department of Redundancy Department - Now with paperwork!
'In organic synthesis, we call decomposition products "crap", however this is not a IUPAC approved nomenclature.' -Nicodem
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bob800
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I stand corrected. 
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Magpie
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Keep in mind that anytime you wish to send a gas through a bubbler, liquid absorber, or particulate solid absorber that that gas must be contained
from the point of generation and conveyed by tubing to said absorber. In many cases that will require that the generation point must be under enough
pressure to drive the gas through the absorber(s). In some cases the absorbtion will be rapid and a vacuum can be created, risking suckback.
Elimination of suckback is the reason why the inverted funnel over a beaker of water is so good. It will readily absorber HCl and HBr.
I'm by no means trying to discourage you from using these techniques. Just be aware of the hydraulics involved and set up your glassware accordingly.
The single most important condition for a successful synthesis is good mixing - Nicodem
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Roachburn
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@ bob800,
A gas wash bottle does seem more feasible than a carbon filter. That link was also very helpful and exactly what I was looking for so thanks for
that. I will definitely give this a shot once I get some decent glass ware. Still saving up for an all glass distillation set so I will have time to
do more research on these future experiments. I cant agree with you more about reading though. I also plan on going back to school again soon and will
probably take some chemistry classes. I forget what video I saw where H2S was a byproduct of the experiment, but it was probably one of the more
advanced that I may end up not doing.
@ Magpie and UnintentionalChaos,
Thanks for the warnings about the suckback. The video on Nitric acid synthesis I saw spoke about something like that. He said the cooling reaction
would cause a vacuum and suck the sodium carb solution into the nitric acid neutralizing it. Couldn't I just have an extra wash bottle right after the
reaction vessel, but leave it empty and not extend the glass tube all the way down to deal with possible suck back? Also could you elaborate on the
funnel method?
Thanks a bunch guys for the info! 
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Magpie
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Quote: Originally posted by Roachburn  | Couldn't I just have an extra wash bottle right after the reaction vessel, but leave it empty and not extend the glass tube all the way down to deal
with possible suck back? Also could you elaborate on the funnel method?
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Yes, the empty wash bottle, known as a trap, is a good idea, commonly used, and is recommended. Here's a link to the inverted funnel method, with
graphics:
http://www.gcsescience.com/pt30.htm
The single most important condition for a successful synthesis is good mixing - Nicodem
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Roachburn
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Say that is cleaver. I'll try it out thanks! I like that web-site by the way. I learned a bunch clicking through the pages, and I always enjoy reading
about the elements!
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Arthur Dent
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My favorite scrubber assembly has been tried ant tested thoroughly and does a very good job:
I have 6 500ml erlenmeyers with a sidearm together in a cardboard box that fits them snugly. All the erlenmeyers are linked together with clear vinyl
tubing to a rubber stopper on top with a glass canule.
In a typical experiment where HCl or Cl is evolved, I link my air-tight lab assembly to the scrubber assembly. The first erlenmeyer is empty, with a
short canule, to prevent suckback, the second is filled with water with a long canule dipping into the water, the third is empty, the fourth is filled
with a solution of NaOH, the fifth is empty and the final one can be skipped and left empty also. The last output is driven through a plastic tube
conveniently driven outdoors.
I feel confident to use this setup with ammonia, HCl, chlorine and solvent vapors, and adjust the scrubber flask contents depending on the gases I
wish to strip-out/neutralize. but I wouldn't use it for anything more noxious (and I have to admit I wouldn't experiment with anything that would
evolve HCN or H<sub>2</sub>S).
I use the six-vessel scrubber assembly when brewing beer, it is connected to my 5 gal. glass fermenting bottle, erlenmeyers 1, 3 and 5 are empty, and
2, 4 and 6 are respectively filled with diluted sulphuric acid, NaOH solution and zeolite. The resulting output is basically stripped of all aromatic
fermentation gases. Why do I go through all this trouble when I prepare a batch of beer or strong spirit? One word: ANTS!
For three years I prepared beer in my basement, and during that period, i had severe ant infestations in my house (it's scary when the floor seems to
be moving!) and when I stopped brewing stuff for a couple of years, the infestations stopped too. With the scrubber, the ant-attracting fermentation
gases evolved by the yeast are absorbed, so problem solved!
This scrubber permits me to do several experiments that I wouldn't be able to do otherwise indoors. I am very limited in what I can do outdoors (I
live in a very busy urban environment with literally 40 or 50 neighboors having a direct view on my back balcony).
Robert
[Edited on 5-11-2011 by Arthur Dent]
--- Art is making something out of nothing and selling it. - Frank Zappa ---
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