Is pencil lead magnetic? 1

[Skogsgurra]

Yes, I know. It isn't. Or, rather, diamagnetic - a magnet repells graphite.

But:

http://gke.org/pub/files/Grafit magnetisk.JPG

Here a piece of drawing pencil lead is attracted by a Neodym magnet. I cannot understand this, it is beyond grasp of an EE.

Any good answers?

Gunnar Englund

http://www.gke.org

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Half full - Half empty? I don't mind. It's what in it that counts.

 

[patprimmer]

Modern pencil leads in pencils that feed the lead through a metal guide tend to be a polymer matrix with graphite filler I think, simply because the advertising says something like polymer enhanced or whatever.

Maybe some static in the polymer. Seems very unlikely though. I would think that much graphite would be a pretty good antistatic.

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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[MintJulep]

Perhaps the pencil had been used to write heavy metal?

 

[Skogsgurra]

Hey! Careful now. I told my friends to have a look here to find the answer. I even put a link in their blog. They expect correct behaviour and a scientific explanation.

I appreciate your humor, MJ - but not sure they do. Order, please! At least for a few hours...

I know - this will make it worse. But I tied. Didn't I?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Skogsgurra]

tried

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[cloa]

Better question for the Physics Forum

http://www.physicsforums.com/

 

[btrueblood]

At a guess - there is probably a small amount of iron contaminant in the graphite, present as Fe₃C - which is ferromagnetic. Might be interesting to see if the same piece of graphite "sticks" to a weaker field permanent magnet...I'd think you might find a way to calculate how much iron carbide is present...but don't feel up to that kind of math before the first cup of coffee kicks in.

 

[swall]

Adding to btrueblood's post, the "lead" is a mix of graphite and clay. Many clays (like the red clay in the southern U.S.) are iron bearing.

 

[EdStainless]

My hunch is iron oxide. It is black and common, it would not surprise me to find enough of it in the mix to measure.

= = = = = = = = = = = = = = = = = = = =
Plymouth Tube

 

[Skogsgurra]

Ben, you forget that I am in GMT+1.

OK. I will be looking for pure graphite. Hmm.. where did I put that Merck sample..

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Skogsgurra]

If I grind that sample (the one in the photograph) how do I test for iron? Any easy chemical test? (I do not posses a gas cromatograph)

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[patprimmer]

My normal test for iron is to put it near a magnet ;-)

Regards
Pat
See FAQ731-376 for tips on use of eng-tips by professional engineers &

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for site rules

 

[btrueblood]

Gunnar, no I'm talking about _me_ needing coffee, not you.

Swall's comment is a good one. Not sure about iron oxide contaminating graphite - but I was thinking about the pyrolysis stage of graphite production, which is generally a reducing, not oxidizing, environment. I suppose if the graphite is later hot- or cold-pressed, it might pick up some iron by abrading tool surfaces.

Time for more coffee.

 

[Skogsgurra]

I need that, too. Coffee. Always.

Yes, I reread and understand now.

I have a test tube. And HCl and H2SO4 and then some gear (a visitor discovered that in our scrap house this sommer). Can I test for iron with that? If I ask Missus for baking powder and such things? Vinegar, perhaps?

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[blacksmith37]

I think the variety of answers depends on the definition of "pencil lead"; Without something like an ASTM spec for it, it can contain about anything (eg FeO, Fe3 04).

 

[Compositepro]

I think you will find this article on "ferromagnetism in lead graphite pencils" relevant.

http://arxiv.org/ftp/arxiv/papers/1107/1107.1662.pdf

 

[IRstuff]

My 0.5mm pencil lead is completely uninterested with a magnet

TTFN

FAQ731-376
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[Skogsgurra]

IR

That is what I had hoped for, also. But my thin leads all jump to the magnet. I have searched the attic and I have found a box with carbon "things". Wife told me that her grandfather was active in the graphite business and made electrodes for the steel industry. He also sold something he called "Cylinder Dew" that was used for steam engines. So, there is a welth of graphite to test. I even found something that I thought was nitroclycerin, but it is an oil/graphite emulsion. I will try that also in a magnetic field. A truly dark night and some black magic awaits my innocent and white soul.

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Skogsgurra]

Compositepro! What a relief! Love you! Now, my soul can remain white and innocent another night. Thanks a lot!

Gunnar Englund

http://www.gke.org

--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

 

[Guest102023]

I just can't resist getting up and looking for a lead pencil and a magnet.