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Blind Angel
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[*] posted on 26-4-2004 at 18:05
Metal Solubility and Solvent


I was wondering if copper or any other metal can be soluble in some solvent, I know that they aren't ionic so it's would be hard to dissolve. This bring me to the idea of recrystalize metal, would it form very solid compound? This may sound silly i know, but if it's possible i would like to try, i got a lot of Cu metal powder that i don't know what to do with.



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t_Pyro
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[*] posted on 26-4-2004 at 18:12


Alkali metals like lithium are soluble in liquid ammonia. The dilute solutions are blue in colour, the concentrated solutions copper-brown in colour. The solution has more or less the same chemical properties as the pure metal. It is also a good conductor due to the presence of free delocalised electrons in solution.
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[*] posted on 26-4-2004 at 19:36


maybe you can try to dissolve in DMSO (Dimethyl Sulfoxide) is abit acidic at room temperature. so it could be a good solvent for most metal or metal complex.;)
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Hermes_Trismegistus
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[*] posted on 27-4-2004 at 00:00
Copper sulphate is quite soluble (in water)


Copper sulphate is an intensely blue crystalline that finds use as an anti-fungal and as an etching bath for zinc

I believe you could make the sulphate by treating the copper with sulphuric acid.

but I would not do so. Copper is a very soft and ductile metal, I am sure that a large amount of work went into extraction and the powdering of that metal and just about anything you do with it will be a step back.

So just leave it be, put it into a jar that is just large enought to hold it (to minimize oxidization) with a packet of dry silica gel and leave it be.

If you don't, there will come a time when you will regret using it on something trivial. It always happens that way.

(Trust me......or ask around)

as for solubility of metallic copper, good luck!

How would anything solvate it? there is nothing to grab onto with a metal atom.

No hydrogen bonding, no electronegativity and not even london dispersion forces of any real significance.




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[*] posted on 27-4-2004 at 00:04
P.S.


There will be a tiny bit of solubility no matter what you put it into, but that will relate to the vapour pressure of copper and will not be very significant.

Basically tiny amounts of individual bare atoms will just get kicked off the surface of the copper by the kinetic energy of the vibrating atoms. That happens at an EXTREMELY slow rate.




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[*] posted on 27-4-2004 at 00:55


Well, there's always mercury, which forms liquid amalgams . . . but admittedly it's not the nicest of chemicals!



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[*] posted on 27-4-2004 at 04:10


actually i didn't put much effort in getting the copper, i ask the school to give it to me since they were throwing it away after experiment (like replacement with zinc or something similar, then filtration) :D

The point of this thread is that i would like to recrystalise Copper, not any of is salt, so turning it into a sulfate is effectively a step back :P




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[*] posted on 27-4-2004 at 04:22


No. Copper isnt soluble - as metal - in any solvent known to me. It maybe soluble in some hightemp. saltmelts though.
Copper is soluble is quite a lot of other metals when those are in a molten state :)

But the usual way to get copper metal is by first transforming it into one of its salts and then to precipitate it again a process called "cementation". You can guess in what form copper precipitates from the word.
If you want to get finely divided copper I suggest to form the CuCl2 salt and then to put some steel/ironwool or zincwool into the solution. Dont forget to add some NaCl!
Works like a charm. Promised, thats tried and true.
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[*] posted on 27-4-2004 at 07:01


Another one is, mix CuSO4 with an excess of Vitamin C, and heat it.
CuSO4 is reduced, and you get finest elemental Cu powder.

Crystalline metals... there are possibilities for other metals though. Think Bi, Cd, etc, some of which (the crystalline state) can be prepared electrolytically, in aqueous solutions!




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[*] posted on 27-4-2004 at 07:30


The effort it took to powder the copper was done before you, I wasn't referring to the effort it took you to pick it up and carry it home. But just try and powder soft copper by yourself.....

Quote:
Originally posted by Blind AngelThe point of this thread is that i would like to recrystalise Copper, not any of is salt, so turning it into a sulfate is effectively a step back :P


I know what you are trying to say,
But to be technical about it, metals aren't actually crystals. And that is exactly why you cannot recrystallize them.

They are metals. And it is the defining properties of metals that sets them apart from crystalline solids.

Metals are ductile, malleable, and good electrical and thermal conductors. They interact in covalent bonding and the electrons exist in an "electron sea" shared by all. Elemental metals also have an overall neutral charge.

crystalline solids are brittle and are pretty much the opposite of metals in every other way as well.

I think that where your confusion comes in is that sometimes we refer to the "crystalline structure" of metals.

but that is another story.

and not entirely true.

The only way you could theoretically crystallize a metal as a metal would be to solvate it into a solvent that wouldn't steal electrons.

Like another molten metal, however the observed behaviour is that when that happens, you cannot crystallize it out, metal A and metal B form an alloy and when you lower the temperature of your "solution" metal A doesn't cool down and crystallize out, the mass just fuses together as one indivisible mass.

I guess what I am trying to explain is that you can't get a cat to bark.

Okey Dokey!




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[*] posted on 27-4-2004 at 11:09


Hmm yeah, i see, actually i already knew much of this about crystal, but i wanted to be sure. My idea came from this site which as sort of "Bismuth Crystal", but as i can see it's isn't. So is there a way to do this with all metal or only some, and since I own a lot of Cu i told myselft that maybe i could try with it. Thx anyway :)



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[*] posted on 28-4-2004 at 11:27


Metals, copper included, do form crystals. They have nice well defined structures and lattice constants. You can do Xray scattering to show this. In the case of some metals the crystal structure is obvious when you look at them (the zinc crystals on large galvanised metal objects are usually quite clear).
Granting that crystalising them from a solvent is often troublesome, it can still be done (you need to use another metal as the solvent). The usual way of obtaining nice crystals is to cool a melt slowly.
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[*] posted on 28-4-2004 at 12:10
I disagree.


I beleive your x-ray scattering and lattice formations are actually showing Crystal-like structure that indicates closest packed arrangements that may superficially look like crystals.

But these metal "crystals" lack the ionic character of true crystals.

And that's why a real crystal shatters, and a metal "crystal" just dents.
:P
IMHO




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[*] posted on 28-4-2004 at 12:33
Hmmm...


Isn't the definition of a crystal the formation of regular molecular lattices, with defined space groups that result in the regular 'crystalline' geometric look?

Isn't it this property that allows the X-ray diffraction, in order to work out the 3D structure of the unit cell (the smallest repeating unit in the crystal)? If it wasn't crystalline and regular, X-ray diffraction wouldnt produce interpretable results! Who is to say that crystals are defined by distinct ionic regular patterns?

For instance, in protein science, proteins, which are highly heterogenous molecules, readily crystallise under the right conditions. Crystallisation is defintely not exclusively a result of ionic interactions only, instead it's the packing that matters. Often empty spaces are simply bridged by water/buffer molecules.

Yet these are univerally called crystals, and not regular non-ionic aggregates or something, with no real crystal structure. Same for benzene - it also should crystallise under the right conditions. No polarity present whatsoever.

I dont see why metals shouldnt form crystals (indeed I have seen them myself), and why they are not 'true' crystals. Even though valence electrons can move about freely, there is some order to it - at any instance in time there are electron holes and electrons, which all 'magically' are in equilibrium with each other. This is the same in ionic crystals, such as Na+ and Cl-.

Anyway - the point is - as far as i know, any molecular/atomic arrangement in a repetitive, regular manner, with defined space groups and coordinates, are crystals :)

[Edited on 28-4-2004 by chemoleo]




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[*] posted on 28-4-2004 at 12:39


having said all that please inform me as to what is happening in various acids when say copper salts are formed?

are these not solutions?
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[*] posted on 28-4-2004 at 17:57


They are solutions of the respective copper salts, not of metallic copper.

Metals do form crystal lattices. The ability to form alloys is due to the fact that since transition metal atoms are almost of the same size, they can easily replace each other from their lattice points. The presence of ions is not a necessity for the formation of a crystal. (eg. sugar?)
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[*] posted on 28-4-2004 at 19:38
T_Pyro


I didn't claim that all crystals were formed by ionic solids, but rather that all crystals had an ionic character.

there is a charge differential between the different atoms of the molecules that make up a sugar or protein crystal this would allow for the ordered arrangement. There is none in a pure metal. All of the atoms have an equal charge.

The stronger the ionic character, the faster the crystal formation.
------------------------------------------------------

But I might as well mention the fly in the ointment of my argument. Diamonds.

Diamonds are inarguably crystals, and yet, like a pure metal, they all have an equal charge.

And then there is the fact that diamonds are not stable, but at surface temperature and pressure revert to graphite.
--------------------------------------------------

I am going to try and find a crystallographer to strictly define a crystal for me.

I don't beleive that the single definition of a crystal is closest packed arrangement.
:)

I'm confused.

[Edited on 29-4-2004 by Hermes_Trismegistus]




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[*] posted on 28-4-2004 at 19:41


Look at the site i mentionned upper:
http://www.unitednuclear.com/bismuth.htm




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[*] posted on 28-4-2004 at 20:26


From what i read is due to the oxide layer on the bismuth that create those color, you can refract a peticular color if you want but that's costy. Used for labwork.



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[*] posted on 28-4-2004 at 20:59


crystals:
- a homogenous solid formed by a repeating three-dimensional pattern of atoms, ions, or molecules and having fixed distances between constituent parts, from http://natural-history.uoregon.edu/Pages/web/glossary.htm

Crystals are materials which has its molecules arranged in a specific, highly ordered internal pattern. This pattern is reflected in the crystal's external structure which typically has symmetrical planar surfaces . Many common substances, from salt to sugar, from diamonds to quartz form crystals. - from www.teachinghearts.org/dre00glossary.html

Noun 1. crystal - a solid formed by the solidification of a chemical and having a highly regular atomic structure from http://www.thefreedictionary.com/crystal

From The Structures of Crystals
A M Glazer, Clarendon Laboratory, Oxford, UK:
The crystalline state is the most stable form of all solids and is very common in nature.

Admittedly, the definition of crystals is not clear cut when it comes to permitted space groups.
Check this: http://www.siam.org/siamnews/01-98/gem.htm
The most important bit:
In the early 1980s, Dany Shechtman, a materials scientist at the Technion in Israel and the National Bureau of Standards (now the National Institute of Standards and Technology) in the United States, got some very strange diffraction patterns from an alloy of aluminum and manganese. The pictures very clearly exhibited the forbidden 5-fold symmetry. (To be precise, the symmetry was 10-fold, as if a pair of interdigitating starfish had crept into the field of view.) This couldn't be, Shechtman reasoned, so he repeated the experiment. But the starfish symmetry wouldn't go away. Shechtman then did what any sensible scientist would do: He shelved the result and started asking around.

Also, a little tour in crystallography. http://www.mse.uiuc.edu/info/mse182/t97.html
The apt reader will notice that GRAPHITE is CRYSTALLINE, despite it's homoatomic nature.
The fact that diamond is thermodynamically less stable than graphite does not mean that graphite is not crystalline.

As I already said above - the verification of whether a body is a crystal resides NOT in the closest possible packing. Noone said this.
Instead, it resides in REGULAR packing, with defined space groups.
Noone equally said that something that LOOKS like a crystal really IS a crystal. It is very likely, however, as a regular naturally formed body with defined and reproducible spacial symmetries is equally likely to have defined spacial symmetries at the molecular level, or more precisely, at the level of the unit cell (the smallest repeating unit).

And this is independent of whether it's a metal, non-metal, ionic or non ionic compound, or even antimatter.

I repeat, how do we verify this?
X-ray diffraction is the way to go. If packing is not regular (which equals amorphous), you won't get a distinct diffrication pattern, from which you can deduce the 3 D structure.
Here you got your definition.

I don't know why I bother... you seem to pointlessly resist overwhelming evidence :(

PS as to crystallographers, I can offer you 4 different ones to ask - shall I? :P




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[*] posted on 28-4-2004 at 21:13
Well........that's that then.....


Quote:
Originally posted by chemoleo
I don't know why I bother...
:P

Because you luv me!!!:D

Quote:
Originally posted by chemoleo
you seem to pointlessly resist overwhelming evidence :(
:P

Not so....Look, I just rolled over.:(




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[*] posted on 29-4-2004 at 13:11


Drat, he rolled over before I got a chance to ask about the ionic nature of diamonds.

Anyway, diamonds only happen to be unstable because we are at such a low pressure. There isn't anything magic about STP so you can't argue that there is anything fundamentally wrong with diamonds when it comes to stabillity.
Anyway, there is still most of the rest of that group C to Sn that also form that structure. (In case you were wondering, my central heating has broken down and grey tin is stable).
Come to think of it, tin gives yet more evidence of the existence of crystals; you can hear them grate across one another if you bend a tin bar. Not as convincing as XRD, but a lot easier to do at home.
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