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Author: Subject: The Smell of Iron, Copper
chemoleo
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[*] posted on 22-4-2006 at 18:47
The Smell of Iron, Copper


Today I dealt with an iron sulphate solution, and was immediately struck with the strong smell of it. It sticks to my fingers, almost pollutes the whole room, even though I only touched a few dry iron sulphate crystals. Hand washing makes no difference, the smell is still there, if not stronger. I am trying to remember if blood smells like that, and I think, to some extent it does.
Interstingly, I remember from handling copper sulphate, that it has a similar smell, albeit by far not as intense.
Now, I could rationalise the taste of it, even tiny quantities, but smell? What makes the iron so volatile that it can be smelled?
It seems quite paradoxical, since FeSO4 is a nice solid, and ionic, so it won't produce any noteworthy gaseous quantities.

What produces the smell? Guesses, input anyone?




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[*] posted on 22-4-2006 at 19:09


You may have inhaled small particles as dust, which have now lodged in your nasal passages. It sounds like the compund may have some affinity for bonding to tissues if you can still smell it on your fingers. You may also be a person who is particularly sensitive to the smell. To me copper sulphate has no smell, and iron sulphate only barely so, and my sense of smell is otherwise normal as far as I can tell.

Z
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[*] posted on 22-4-2006 at 19:14


Yes, I agree that this may well be the case, thanks for pointing this out. However, the smell is distance-related, the further away the less intense. My fingers actually smell less by now.

Anyway, I was more after why a non-volatile compound such as FeSO4 could be smelled in the first place. Have a sniff at a solution of it. But then, I suppose you could argue that aerosols are generated, which can be smelled....lets see if the FeSO4 tube smells after not having it disturbed it for a while.




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[*] posted on 22-4-2006 at 21:34


Iron has a very noticeable smell to me as well. There is often a metallic taste as well, no surprise there. Iron -sulfur compounds are very strong. Even regular rust and iron filings or grindings have a smell too. After spreading an iron garden supplement the smell is overpowering, and even seems to accelerate body odor. The area where I live has very alkaline soil due to calcium carbonate in the water, so iron has to be added to many plants. There is a chelated iron compound that works well, and after adding it to water it smells just like blood, and is a very red color. It is always the last thing to do, just before heading to the shower.

I have not noticed as much smell with copper compounds, although there is some sort of acrid taste to many of them. I developed a very sore throat after handling a very small amount of cupric acetate. I realized it was a fine powder and thought I was being careful. I'll be much more careful in the future.
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[*] posted on 22-4-2006 at 21:40


Sorta on this topic, you ever notice metal has a slight smell as well? I'd like to know why that smells, as well as why some compounds smell as well.
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[*] posted on 22-4-2006 at 22:41


I've noticed that iron, copper, and probably nickel have smells. It doesn't work for clean metal though- I think it has to have been touched, which may suggest it's catalyzing a reaction with something in the fingerprint or dead skin or whatever.

After sanding copper and handling it with bare hands, I smell nothing. Immediately on handing pre-touched copper, I smell the distinctive odor.

U.S. nickels (75% Cu, 25% Ni) I think have a somewhat sweeter metallic smell, which may suggest nickel has a somewhat different odor.

My CuSO4 and FeSO4 don't smell, at least I don't remember the iron smelling, but as pure crystalline compounds I would hope they don't. After say, soaking your hands in solution or fine crystals and your own sweat, I can imagine lots of stuff would happen.

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[*] posted on 22-4-2006 at 23:46


Hmm, I have noticed this smell too while handling copper(II) acetate. At first I thought the smell was due to the vinegar smell, but on comparing a vinegar solution and the copper(II) acetate, the Cu(Ac)2 stands out with a distinct metallic smell not quite unlike that of iron, as pointed out by Chemoleo. After sniffing on this stuff for a while, you can get dizzy, and I've noticed that after that, my sense of smell for other stuff is sort of deadened for a day or more.



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[*] posted on 23-4-2006 at 01:37


I have noticed this too with iron sulfate, although not as intense as you describe.
I can think of two explanations for this, except from the possibility of particles (which doesn't explain that your fingers smelled).

One: Iron, when it contains carbon, forms (along with the usual cementite) a special sort of carbide in which the carbon atoms exist as chains. If the iron is dissolved in an acid, this carbide hydrolyzes into a mixture of gaseous, liquid and solid hydrocarbons. I have read this in a big chemistry book, the Hollemann- Wiberg.
Ever noticed how there is a really strong smell when you dissolve steel wool in dilute HCl or H2SO4? It cold be due to those hydrocarbons.
And the carbide can also slowly hydrolyze with aerial moisture, which explains the smell of metallic iron.
Iron sulfate might simply be contaminated with those smelly hydrocarbons.
I'd be interested if totally carbon- free iron also smells when dissolved in HCl or H2SO4.

The second theory: Iron might (in very small traces) form a volatile tetroxide, just like Osmium. This must have an extremely powerful smell, if modern chemistry has until now failed to prove its existence.




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[*] posted on 23-4-2006 at 03:55


Maybe carbonyls? Many metals form volatile compounds with carbon monoxide. Diketone complexes with metals can also be volatile.

[Edited on 23-4-2006 by Eclectic]
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[*] posted on 23-4-2006 at 04:26


Common metals contain always some quantities of sulfur, phosphorus and arsenic. Although quantities are usually very small , these substances can make very smelling compounds. This is at least one of reasons why metal stinks when reacted with acids but maybe certain compounds of those non-metals are also cause of generic metallic smell?

[Edited on 23-4-2006 by chromium]
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[*] posted on 23-4-2006 at 06:08


Thanks for all the interesting replies, and ideas.
I checked the FeSO4 solution that I prepared yesterday, and the smell is gone, even if my nose is like 2 cm above the liquid surface.
So FeSO4 on its own isn't volatile (doh!), and the smell becomes intense once I shake the solution, and have a sniff again. Aerosols? Clumsy me got a drop or two onto my fingers again, and now they reek like crazy! So not aerosols. Conflicting evidence. Hmmmm.
Sniffing the analytical grade FeSO4*7H2O container (dry), the smell of iron is definitely there, albeit weaker.

Yes, I also noticed, the metals themselves smell, like 12AX mentioned.

I find it peculiar that noone tried to work this out. Potentially it has some interesting outcome...particularly if they are volatile products of iron!




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[*] posted on 23-4-2006 at 07:02


Interesting question, and one I have wondered about before. Google didn't give me an answer.
The smell from disolving metals in acid is, as has been said, mainly due to things like AsH3, PH3 etc formed by nascent hydrogen reducing impurities in the metal.
The metal salts themselves, like CuSO4 and FeSO4 don't smell- hardly suprising because they are involatile.
On the other hand (Forgive the pun) when they come into contact with skin they do produce an odour. The same smell is produced by handling Cu coins etc.
I can only presume that either
Cu and Fe produce volatile salts with some component of skin or
They catalyse some reaction involving some component(s) of sweat and air to give a compound with a characteristic smell.
My guess would be the second option because volatile salts are rather rare. (and also because Cu (II) and Fe(III) both have oxidising properties so it's reasonable that they both form the same product and thus pretty much the same odour.)

I guess the next stage involves skin, FeSO4, and a mass spectrometer. I can provide the FeSO4, can anyone else help with the other items? :-)
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[*] posted on 23-4-2006 at 14:29


Speaking of coins, if anyone remembers when they had silver in coins, the US 90Ag/10Cu coins had a distinctive 'silver smell', which I always thought was from the sulfide. Even silver spoons and other silver had the same smell.
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[*] posted on 23-4-2006 at 16:31
I am quite sensitive to the smell of ferrous ion


I have worked with ferrous sulfate in my lab and I notice the ferrungous odor quite easily. My baby daughter was anemic a few months ago and the doctor prescribed ferrous sulfate drops. The drops had the pale green color and smelled even stronger than my technical grade ferrous sulfate. My daughters ferrous sulfate had glucose or some other sugar to help with taste. Maybe there is a carbohydrate reaction with the iron through perspiration.



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[*] posted on 24-4-2006 at 20:17


Hmm, sulphate esters?



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[*] posted on 24-4-2006 at 21:03


I haven't noticed a smell from copper or its compounds, but iron has a strong smell. Also, you can taste iron in juice that has sat in steel cans for a few days and in some molasses (the label claims it contains 20% of the daily value for iron, almost certainly as Fe(III)).

I have also noticed a smell with aluminum. Interestingly, indium smells like aluminum, only stronger. It is very soft, and after handling it, I noticed a metallic tinge on my fingers. Perhaps the metal flakes become airborne and react with water or acids in the nose to form ions.
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[*] posted on 25-4-2006 at 05:27


I can smell copper coins - might be my imagination but I think they smell more when wet (??) and or dirtier.
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[*] posted on 25-4-2006 at 06:54


The effect of copper smelling is quite common to me as well. If I handle copper coins, but also other copper objects, then I notice a certain smell. The same is true, when I bring my finger in contact with copper salts. With metallic copper, I only notice the smell, when the copper object is oxidized. A brand new 5 eurocents coin does not give any smell to me.
With iron (rust, metal, ferrous and ferric salts) I have a similar thing. The smell, however, is quite different to me, compared with the smell of copper.
With silver, I also notice a smell, again, different from copper and iron.
With nickel, I do not notice any smell, nor do I with gold, bismuth, zinc, and aluminium.

I think that the smell is due to reaction of the skin (or some of the solutions in the cells, sweat, etc.) with the metal ions, not with the metal itself. That explains, why clean copper does not provide the smell, while oxidized (dark brown) copper and also its salts do give a smell on my hands. The smelly compound probably is some organic compound, which, however, is different for copper, silver and iron.




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[*] posted on 24-5-2006 at 17:13


I was working with some cerium today, now that smells horrible after you touch it. I have noticed the iron smell, but no other metals had a smell to them previously, however cerium...terrible stuff...

Neutrino, I remember that thread as well, and was also unable to find it.




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[*] posted on 24-5-2006 at 18:49


Quote:
Originally posted by chemoleo
Today I dealt with an iron sulphate solution, and was immediately struck with the strong smell of it. It sticks to my fingers, almost pollutes the whole room, even though I only touched a few dry iron sulphate crystals. Hand washing makes no difference, the smell is still there, if not stronger. I am trying to remember if blood smells like that, and I think, to some extent it does.
Interstingly, I remember from handling copper sulphate, that it has a similar smell, albeit by far not as intense.
Now, I could rationalise the taste of it, even tiny quantities, but smell? What makes the iron so volatile that it can be smelled?
It seems quite paradoxical, since FeSO4 is a nice solid, and ionic, so it won't produce any noteworthy gaseous quantities.

What produces the smell? Guesses, input anyone?

I think you have contracted an incurable disease and you must die. Sorry.

it´s called "stinky fingers" btw.



[Edited on 25-5-2006 by Organikum]
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[*] posted on 25-5-2006 at 06:48


The strongest source of this smell that I know is the creek that runs past my house.
The soil around here is highly acidic, lots of soluble aluminium and the creek runs through a rich patch of iorn pyrite. The iorn pyrite in distilled water or dissolved in HCl does not smell as stongly as the creek or fingers after spilling the acidified solution on them.
I definately favour the theories put forward by chloric1, woelen and unionised.
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[*] posted on 25-5-2006 at 07:09


A while back I was at a theater where I sat on the balcony, the balcony had copper rails and the rails had very typical smell reminiscent of ozone... Any theories on that?



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[*] posted on 27-5-2006 at 22:56


Copper oxides/nitrides have the smell you are describing. I recently went to pick up a batch of black copper oxide for a large target and noticed the pungent smell right away.


interesting stuff.
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[*] posted on 28-5-2006 at 04:38


My copper oxide doesn't smell, but then I pyrolyzed it (as part of the production), too.

Tim




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[*] posted on 19-10-2006 at 04:43


This seems to be the answer:

http://www.sciencedaily.com/releases/2006/10/061018150716.ht...
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