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is this enough hydrogen?

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LAN_403

Easy Target

Wed Nov 28 2007, 06:54PM

Registered Member #1148 Joined: Wed Nov 28 2007, 06:24PM
Location: Clifton, Virginia
Posts: 4

In chemsity class last year me and a friend got the idea that with enough HCl and Mg ribbon in a closed container (we were thinking something like a jolt can) with a pin size hole, we could create enough pressure to ignite the hydrogen gas as it exited the container.
i.e.
2H+ + Mg --> H2 + Mg+2
Unfortuantly, we never got around to buying the HCl, though we did get a lot of the Mg ribbon.
My question is if we do try this, would it be possilbe to create the constant pressure needed to keep the exiting hydrogen constantly ignited? If this is possible, about how long would this last?

Swany

Wed Nov 28 2007, 07:14PM

Registered Member #261 Joined: Mon Feb 27 2006, 12:34AM
Location:
Posts: 22

Ignite the hydrogen via pressure? What makes you think pressure alone will do it? I don't quite follow that bit.

What you can do is react an active metal with HCl (dilute it, it's much to concentrated when you buy it at the hardware store) and bubble it through water to remove any HCl vapor from the H2, then burn that. I would advise against using the HCl/H2 mix, but that is up to you. I would also use Zn as my metal, but if you have Mg you want to use, go ahead. There are just cooler things to do with Mg.

Pressure alone will not ignite it, but H2 does ignite spontaneously in the presense of platinum. Get some Pt wire from a jewlery store, place it at the hole.

Easy Target

Wed Nov 28 2007, 08:34PM

Registered Member #1148 Joined: Wed Nov 28 2007, 06:24PM
Location: Clifton, Virginia
Posts: 4

i wasn't plannig on igniting the hydrogen via pressure, i was going just use a lighter.
i was wondering if there would enough pressure to force the H2 out quickly enough to allow the H2 coming out to continuously burn and not have the flame go out.
sorry about the bad explaination

H2 ignites when in the presence Pt? If i may ask, how?

Bjørn

Wed Nov 28 2007, 09:10PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

Platinium works as a catalyst.

More importantly, how are you going to make sure there is no air in the container?

Easy Target

Wed Nov 28 2007, 09:41PM

Registered Member #1148 Joined: Wed Nov 28 2007, 06:24PM
Location: Clifton, Virginia
Posts: 4

i haven't given thought to that, but i figured that the hydrogen would be ligher then the rest of the air, so i would wait a second, then poke the hole in the top
and the hydrogen would already be there....
what would you suggest?

Bjørn

Wed Nov 28 2007, 10:59PM

Registered Member #27 Joined: Fri Feb 03 2006, 02:20AM
Location: Hyperborea
Posts: 2058

I would normally not do that because of diffusion and unknown factors there might be a combustible mix of hydrogen and air at the top and it might explode in your face.

I would normally collect the gas in a liquid with a funnel like structure that is upside down to make sure there is as little air as possible present.

Dr. Slack

Fri Dec 14 2007, 11:40AM

Registered Member #72 Joined: Thu Feb 09 2006, 08:29AM
Location: UK St. Albans
Posts: 1659

i haven't given thought to that, but i figured that the hydrogen would be ligher then the rest of the air, so i would wait a second, then poke the hole in the top
and the hydrogen would already be there....

When I was quite young, I experimented with electrolysis. I knew enough to get myself into trouble, and nearly knew enough but wasn't quite quick enough to get out of it. I drilled a large glass pickle jar to insert a couple of electrodes, put a hole in the lid, 1/4 filled with diluted battery acid and connected a battery charger for a while. I noticed the H2 coming off the cathode, but didn't see any O2 coming off the anode, I thought "Oh, I had expected some oxygen, but I guess it's all reacting with my brass electrode, I'll try to light the hydrogen".

I struck a match, and looking back on it, I would guess that my perception of time and order for the next few moments was screwed, because in the time it took to move the match the 0.5m to the jar, I thought, or thought I thought, "I wonder what sort of flame it'll produce, I assume there's really no oxygen coming off the anode, hang on a moment, even if there's no oxygen being generated, has the hydrogen coming off flushed *all* of the air from the jar, perhaps I'd better wait a little longer and ..."

It was quite loud. I stood there with an extinguished match, standing in broken glass, dilute sulphuric down my front. Perhaps the metal lid of the jar prevented glass and contents from coming upwards, as I still have my sight. I stripped off, threw clothes into a bath, and managed to get the evidence cleaned up before my parents got home. I then sat and shook in a corner for a while as the reality sank in.

Do something to make sure there's no residual oxygen in the hydrogen before you light it. Collecting over water is good, with minimum dead space in the top of the reaction vessel.

Bryan

Thu Feb 21 2008, 09:35AM

Registered Member #1201 Joined: Mon Dec 31 2007, 08:49PM
Location: NC
Posts: 4

best advice to you as I make hydrogen devices for cars would be use pvc sealed with two stainles steel rods and washers on them. hook up twelve volts you can use vinegar lemon uice or KONH which is the best electrolyte or potassium hydroxide works well too and hook up positive and negative the hydrogen will be comeing have a hold to release the gas into a clear hose an then fill up a 20 oz drink bottle with the gass put in a long tip grill lighter and it will shoot like a botle rocket about 300 feet in the air and make a huge noise. word to the wise only use plastic and anything larger that 20oz bottle will cause serious injury as there is to much hydrogen and oxygen. Never store hydrogen and oxygen blend it's been known to go off near electrical devices when I do it we make it and use it right then. This is a primative solution as in the cars we use a 24 stainless steel plate system called a cell. we use three cells per unit. Have fun be safe Hydrogen is powerful and unstable. you can also try rods in a jar add dishwasher soap and light the bubbles which is cool and safer.

Chris

Thu Feb 21 2008, 08:16PM

Registered Member #8 Joined: Thu Feb 02 2006, 04:34AM
Location: Harlowton, MT, United States
Posts: 214

You could purge whatever it is thoroughly with nitrogen, argon, CO2, R-134a, or some other such inert gas, before generating the hydrogen. That's what I did for my acetylene generator to make sure there was no air in it (I used argon because I happen to have a tank of it).

Also a pinhole is pretty much too small; concentrated HCl and magnesium generates hydrogen rather quickly. If you're trying to make something actually useful you will also want to pass the hydrogen through a dessicator (concentrated H2SO4 works well) to dry it out. Keep in mind that acid/metal reactions are orders of magnitude more expensive per mole of hydrogen generated than other methods like electrolysis of water or catalysis of hydrocarbons.

Weston

Thu Feb 21 2008, 10:36PM

Registered Member #1316 Joined: Thu Feb 14 2008, 03:35AM
Location: Cambridge, MA
Posts: 365

You can produce Hydrogen slowly by just puting magnisum in water. In the 1800's some thing this device you are talking about was sold as a novelty.

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