Palladium absorbing hydrogen gas.

[jdurg]

I just have to say that this is the neatest thing I've seen. I recently purchased a one ounce palladium Maple Leaf coin to go with my one ounce ingot of Pd that I already own. Knowing that palladium absorbs hydrogen gas, I decided to see if this was true. I set up a balance using a flat piece of wood and a metal 'triangle' for the wood to balance on. I then put a one ounce sample of silver on one end and my palladium one ounce bar on the other end. The piece of wood balanced perfectly on the metal stand for it. I then went and marked where the balance point was and tried to balance other things to make sure the balance apparatus worked. It did.

 

So I then went and set up an electrolysis apparatus where the hydrogen gas would be directed through some tubing right onto the palladium ingot I have. I did this little 'electrolysis' for quite a while to ensure that a good deal of hydrogen gas would get absorbed onto the palladium. After about five hours of continuous electrolysis, I went and tried to balance the palladium ingot with the one ounce silver ingot. The palladium ingot was heavier! By a good three grams or so, the palladium was heavier than the silver. So it had indeed absorbed a great deal of hydrogen gas. To remove the hydrogen, I went and placed the palladium in a shallow pan of water and heated the water up. You could see small bubbles of gas forming on the palladium as the temperature went up. I heated it until I could see no more bubbles forming, then I went and dried it off and reweighed everything. Once again, the palladium ingot balanced out the silver ingot on my balance.

 

If anybody has some pure palladium metal around, I highly suggest trying this experiment out. It is incredibly neat to see.

[insane_alien]

3 grams?!? thats 1.5 mol of H2! which is around 33.6 litres at STP! thats a hell of a lot.

[MattC]

I know you know this, jdurg, but for any others reading this who don't, he means adsorbed, not absorbed.

[jdurg]

I know you[/i'] know this, jdurg, but for any others reading this who don't, he means adsorbed, not absorbed.

 

Heh. Yeah. I couldn't remember off the top of my head whether it was aDsorbed or aBsorbed. I figured someone would point it out to me.

 

And yeah, the mass increase did shock me, but for the length of time that I had the H2 passing through/onto the metal it didn't seem all too alarming.

[warut]

Very nice experiment indeed, jdurg!

 

I don't know which one is correct: "absorb" or "adsorb." But since the hydrogen molecules go directly into the interstitial space between palladium atoms, not just adhering to the surface of the ingot, I can't see anything wrong with using "absorb."

 

BTW, I've heard that the volume of the palladium will be slightly increased when absorbing hydrogen gas, and the density of hydrogen in palladium can exceed that of liquid hydrogen!

[rakuenso]

isn't this a hydrogenation syn reaction? I'm pretty sure its adsorb

[woelen]

3 grams?!? thats 1.5 mol of H2! which is around 33.6 litres at STP! thats a hell of a lot.

Indeed, a LOT of hydrogen. This means 3 moles of electrons, or almost 300000 Coulombs of charge. Five hours is 18000 seconds, for simplicity let's make it 20000 seconds. Did you really use 15A of current for your electrolysis? That seems a LOT to me.

 

Probably you must have had much more current, because not all hydrogen will be taken up by the palladium. The figures seem a little unbelievable to me.

[akcapr]

If he didnt seal it ffrom air well enough, surely it culd have absorbed something from the air- moisture perhaps? just a guess

[jdurg]

There was probably bits of moisture that found its way in there as I didn't want to heat the palladium up once it had adsorbed the hydrogen. (As it would then give it all back). So my drying methods were to use a paper towel and wipe off the water that was sticking to it. (In order to ensure proper adsorption of the H2, I had everything submerged underwater so as the H2 displaced the water it would adsorb onto the Pd without the Pd being used as an electrode). So yeah, there was indeed some water in there which probably altered the mass a bit. Still, seeing the bubbles coming off the Pd as I heated it up under water was pretty freaking sweet to see.

 

(EDIT: The source of my electricity was an electrical outlet in my house moved through an AC adapter to change the AC current to DC current. I believe over here in the USA we have 110 volt outlets but I'm not sure about the amperage. I just know that it hurts like hell if you get zapped. )

[jsatan]

nice, I've baan wanting to get some palladium to make a Hydrogen cell, but I never got around to looking for it, lol.

Cool none the less

[warut]

At least, the following articles use "absorb" or "absorption":

http://www.iupac.org/publications/pac/1990/pdf/6211x2091.pdf

http://www.psc.edu/science/Wolf/Wolf.html

[LazerFazer]

The source of my electricity was an electrical outlet in my house moved through an AC adapter to change the AC current to DC current. I believe over here in the USA we have 110 volt outlets but I'm not sure about the amperage. I just know that it hurts like hell if you get zapped.

 

Well, the voltage isn't really much of an indicator of current. V=IR, so even though the potential difference (voltage) might be the same, the current can be completely different because of the resistance of the object. For example, the resistance between two points on opposite sides of the body, when dry, is about 10^4 ohms, which I would assume is pretty high compared to that of your AC/DC adapter.

 

And it would be about 16.6A flowing through those wires, making the effective resistance of the adapter and wires only 6.6ohms. Thats pretty low, so forgive me, but I'm a bit skeptical here. (Oh, btw, the clothes dryer in my house only takes 13A, and I think thats the most Amp-hungry device we have).

 

Cheers,

LazerFazer

[woelen]

Yes, I have the same skepsis as you have. I have quite some experience with electrolysis experiments and having a few amps of current already is a lot. With 15 amps of current, the cell would be red-hot, due to resistive effects (dissipation) and the anode of the electrolysis cell would have to be replaced every few minutes, unless it is made of a very inert platinum-tantalum-iridium alloy, but I doubt that such an expensive anode would be used.

 

@Jdurg: I think that most of the increase of weight is due to water, sticking to the piece of palladium. I certainly believe that some hydrogen is absorbed and even if 0.1 mole is absorbed and you heat the sample of palladium under water, then you can see a LOT of bubbling already.

[jdurg]

Well my method of balancing was a simple balance-beam type assembly and there is a chance for some experimental error there. (I do not possess a digital scale which would make it more precise). The big part of the experiment was seeing the gas bubble out as I heated up the palladium under the water. It was pretty neat to see the bubbles forming on the surface.