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Is pencil lead magnetic?

Is pencil lead magnetic?

Is pencil lead magnetic?

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

But: http://gke.org/pub/files/Grafit%20magnetisk.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
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

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
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RE: Is pencil lead magnetic?

Perhaps the pencil had been used to write heavy metal?

RE: Is pencil lead magnetic?

(OP)
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
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

(OP)
tried

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

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.

RE: Is pencil lead magnetic?

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.

RE: Is pencil lead magnetic?

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

RE: Is pencil lead magnetic?

(OP)
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
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

(OP)
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
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

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.

RE: Is pencil lead magnetic?

(OP)
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
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

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).  

RE: Is pencil lead magnetic?

(OP)
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
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

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

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

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

RE: Is pencil lead magnetic?

0.5mm Pentel HB leads, no interest in magnets either.

Cpro, the paper is interesting, but the result (which they say correlates to increasing defects in graphite crystalline behavior) could also be explained by rising iron content in the lead samples.

RE: Is pencil lead magnetic?

(OP)
This is what we found in the attic: http://gke.org/pub/files/Graphite%20oil%20and%20Cylinder%20Dew.jpg

The wood blocks contain bottles with an oily liquid. There are textile shock absorbers and we naturally thought it was Nitroglycerine - Alfred Nobel's Manor and Laboratory is just five or six miles from us - but it is a harmless emulsion of collodial graphite in oil, the so called Cylinder Dew. The little tin bottle also contains Cylinder Dew - the friction proofing of those days. The other items are graphite in different shapes. From rods via little 'pearls' to granulate. There are also disks and other shapes.

An interesting find.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

I didn't read the paper too carefully. I noticed the mention that lattice defects in the graphite can cause ferromagnetism, but there was also discussion of iron in the clay and other additives. Like many scientific papers, it left me wondering what point the authors were trying to make (other than publishing another paper). There were data of interest, however, such as some commercial leads are magnetic.

 

RE: Is pencil lead magnetic?

(OP)
Same here. But my friends were duly impressed and the discussion is closed.

The blog lady asked me to say that Mint Julep made her ROTFL. And, that lady isn't easily impressed. She is - among other things, also a basket-ball coach.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

Interestingly, I've got two types of lead from the same manufacturer, Bazic standard 0.5-mm lead and what they call "Ceramics" lead.  The latter is mildly attracted to a magnet, but the former is not.  However, the attraction is pretty weak, barely enough to hold up its own weight.

TTFN

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RE: Is pencil lead magnetic?

(OP)
Yes, very weak. That is what it should be in a materiel like that. The diamagnetic materials (repelled by magnets) show very weak forces and the paramagnetic ones, except 'magnetic material' are also quite weak.

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

RE: Is pencil lead magnetic?

"the discussion is closed."

Nice try, Gunnar.   

RE: Is pencil lead magnetic?

Graphite has a magnetic suseptibility of -0.6 [10(-6)cgs]

 

Thomas J. Walz
Carbide Processors, Inc.
www.carbideprocessors.com

Good engineering starts with a Grainger Catalog.    

RE: Is pencil lead magnetic?

(OP)
Thanks, negative susceptibility would mean that graphite is repelled by a magnet? Is it?

Gunnar Englund
www.gke.org
--------------------------------------
Half full - Half empty? I don't mind. It's what in it that counts.

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