Sciencemadness Discussion Board

Is there anything that will safely absorb hydrogen?

gatewaycityca - 16-2-2014 at 23:40

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.

Varmint - 17-2-2014 at 04:39

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

vmelkon - 17-2-2014 at 05:04

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).

Zyklon-A - 17-2-2014 at 06:29

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]

Refinery - 17-2-2014 at 07:33

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.

Zyklon-A - 17-2-2014 at 08:30

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]

Refinery - 17-2-2014 at 09:10

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.

Zyklon-A - 17-2-2014 at 09:38

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.

Refinery - 17-2-2014 at 09:58

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.

organicchemist25 - 17-2-2014 at 10:57

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?

gatewaycityca - 17-2-2014 at 11:47

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]

vmelkon - 17-2-2014 at 12:51

Quote: Originally posted by gatewaycityca  
hydrogen is mainly dangerous if it's under pressure or if it gets too concentrated?

[Edited on 2-17-2014 by gatewaycityca]


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.

MrHomeScientist - 18-2-2014 at 08:13

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.

blogfast25 - 18-2-2014 at 11:14

@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. :cool:

[Edited on 18-2-2014 by blogfast25]

phlogiston - 18-2-2014 at 12:31

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.

gatewaycityca - 18-2-2014 at 17:55

Ok, thanks for your help guys. :)