gatewaycityca
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Is there anything that will safely absorb hydrogen?
This might be kind of a lame question, but let's say later on I try some experiments with chemical reactions that might release hydrogen...is there
something I can use that will absorb hydrogen gas and combine it with something else to make it non-flammable?
I thought of just passing it into water, but of course it would just bubble out anyway.
I'm sure most people are looking for ways to release hydrogen to use it, but it will be a while yet before I want to play around with
flammable\explosive gases! I'd mainly be interested in reactions themselves, for exothermic experiments. Hydrogen would just be a waste product to
me.
But like I said, I'm not quite ready yet. Maybe in the somewhat near future though.
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Varmint
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Palladium is purportedly capable of absorbing 900 times it's own volume of hydrogen gas.
OK, that's interesting if you have lots of money to buy large volumes of palladium.
If you want to truly dispose or "lock up" excess hydrogen, the only cost effective means I can imagine is to develop a safe way to do a controlled
burn. Even cheaper (and less dangerous) would be to just purge it into a fume hood such that the concentration can never exceed the mimimum required
to form an explosive mixuture with the balance of the air stream.
DAS
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vmelkon
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How much hydrogen are you going to release?
How big is your room?
If your room is 8 m x 8 m x 3 m
Volume = 80 dm x 80 dm x 30 dm = 192000 L of air.
If you release 2 L of hydrogen,
2 L / 192000 L = 0.001% of your air is hydrogen
so you aren't going to suffocate and it isn't going to blow up your house (in my example).
Signature ==== Is this my youtube page? https://www.youtube.com/watch?v=tA5PYtul5aU
We must attach the electrodes of knowledge to the nipples of ignorance and give a few good jolts.
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Zyklon-A
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You could fill up a balloon (or more than one) with all the hydrogen generated, tie it, and set it off safely. But really I don't think there is any
need to attempt to catch it at all, gasses diffuse very fast, and hydrogen fastest of all, so if you leave your door open, the small amount of
H2 that you generate will disperse throughout the house very fast and will not be any problem.
[Edited on 17-2-2014 by Zyklonb]
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Refinery
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The combustible concentration of hydrogen is to my knowledge very large, as wide as 1-99% concentration, but it's weight to volume is as well very
low, where air weight about 1.3 grams per liter, hydrogen weights about 80 milligrams. If you are generating only minor amounts, like few moles, you
can just let it vent off, but if you have a continous source, like catalytic dehydration or dehydrogenation reaction where you generate dozens of
moles of hydrogen, you should check that your apparatus is air-tight and use a tube to lead the hydrogen fumes outside, or then through a water trap
and into an incinerator. Any source of flame, even a candle to the crude extent, would suit for that purpose. Draw another tube from water trap near
the flame and do the reaction. If you live any place where you can dump the hydrogen outside, do it, because hydrogen is very light as mentioned, and
it will just simply rise high to the skies.
I would not suggest filling balloons or other containers with it, because even a minor electric discharge can ignite and rupture it, setting it off
with loud bang. You don't want to do that in a city block. I wouldn't want to do that even in my remote workshop.
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Zyklon-A
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No offence Refinery, but I don't think you have ever set off a hydrogen filled balloon. It doesn't make a very loud sound, more like a poof, you
probably wouldn't even hear it from 50 feet away unless you are looking at it (depending on the size of the balloon). If the balloon contains the
right stoichiometric mixture of oxygen, it will be pretty loud, but just hydrogen, not so much.
[EDIT] https://www.youtube.com/watch?v=f-HkVlq1kcQ
[Edited on 17-2-2014 by Zyklonb]
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Refinery
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Hmm, you may be right. I just saw it easier to use tubing. If you're gonna inflate balloon with hydrogen, you will need to pressurize the system
slightly which may cause trouble if something goes wrong, eg. if you've got a distillation apparatus with dropper funnels and other stuff, they may
pop out of their sockets.
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Zyklon-A
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Well yes, the balloon isn't a practical way of disposing of hydrogen, but even though H2 is very cheap, I would never just through away
large amount of it. At least you get a little fun out of blowing up a balloon... Pressure shouldn't be a big deal, I heard that a balloon (on average)
holds less than .5psig, which isn't much.
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Refinery
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If you got single flask, like aluminium and sodium hydroxide to inflate the balloon, then it'd be no problem, but I understood that the poster has
some kind of apparatus in which he conducts the reaction, so any uncontrolled pressure deviations would pose a risk. I wasn't even thinking the
pressure needed to inflate the balloon in first place so I might have likely popped out some sockets if I were doing that.
On the other hand, if all you want to do with hydrogen is to burn it up, well, there are a lot better solutions for pyrochemistry. Most balanced
reactions produce only 1 mole, or 1 gram of hydrogen, which is quite a good amount for hydrogenations, but very sad for blowing things up, and most
efficient reactions like forementioned Al+NaOH will make only some grams out of one kg of reagents. If you aint gonna need it anywhere, just vent it
out. If you're gonna need it (hydrogenation, perhaps), you're gonna need pressurized equipment anyways.
Hydrogen must be one of the most argued elements there is.  People imagine it can
be just liquefied like nothing and it has superior energy densities compared to just about anything, but the sad scientific facts are anything but an
answer to the world's energy problem. I'd actually rank hydrogen as of the last options for chemical energy production, supply or use.
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organicchemist25
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You would have to be producing A LOT of H2 for it to become a problem. Are you trying to keep it? If not, just exhaust it outside or run a hose of
from a side arm. Also, like someone else said, open windows and doors. That should be good enough. How much do you anticipate evolving/producing?
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gatewaycityca
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Well let's say I was mixing chemicals to make an exothermic reaction, and I was mixing hydrochloric acid with some other substance that might release
hydrogen. Just hot enough to heat up water. I would dilute the acid so it wouldn't be too strong, but if the mixture was inside a small closed
container with a tube or hose to vent the hydrogen, would that be enough to prevent a flammable or explosive mixture? Would a small reaction like
that be enough to be a problem?
What about another mixture in a separate container that releases CO2 at the same time, and then venting that through the first container? That should
reduce the flammability, right?
I guess my point is that right now I'm interested in experimenting with exothermic reactions, and I've been wanting to stay clear of anything that
might release hydrogen...but if there is a safe way to deal with it, then I might not be so nervous about it. If I understand right, hydrogen is
mainly dangerous if it's under pressure or if it gets too concentrated?
[Edited on 2-17-2014 by gatewaycityca]
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vmelkon
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Not sure what all the fuss is about. Like I said, if you have a gigantic room and you are going to release 1 or 2 L, who cares.
If you are making H2S, phosphine, HCN or something like that, fine, get yourself a glovebox or something.
Signature ==== Is this my youtube page? https://www.youtube.com/watch?v=tA5PYtul5aU
We must attach the electrodes of knowledge to the nipples of ignorance and give a few good jolts.
Yes my evolutionary friends. We are all homos here. |
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MrHomeScientist
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Don't worry about it; I'm sure you won't be producing nearly enough hydrogen to be of any real risk. Vmelkon is right. I make the gas all the time
dissolving metals in acids, and I never worry about it being explosive. Do it outside with a fan blowing at it if you're really worried. I tend to do
any reaction that produces any kind of gas outside anyway, because the bubbles throw up tiny droplets of liquid that can get on things or are smelly.
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blogfast25
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@gatewaycityca:
Many of us here produce small amounts of hydrogen frequently. As explained, unless you're producing a lot, simple ventilation is more than adequate,
an extra precaution is to avoid open flame (use electrical hot plate for heating). Hydrogen related fires or explosions in home labs: I've yet to come
across a single reported case. 
[Edited on 18-2-2014 by blogfast25]
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phlogiston
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I have heard of one case where someone was operating a series of chlorate cells. A failing connection inside a cell caused a spark and blew the cap of
the PVC tube that was used as the container. No other damage occurred.
Unless you were planning to do large scale reactions in a small or poorly ventilated space, don't worry too much about it. If you ventilate your
workspace well, you would have to generate massive amounts very quickly to reach a dangerous concentration.
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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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gatewaycityca
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Ok, thanks for your help guys.
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