Sciencemadness Discussion Board

Why so many different colours for same chemical

CHRIS25 - 7-4-2012 at 05:04

Please could some briefly explain why there are for example, blue copper chloride, green copper chloride, brown copper chloride and blue-green copper chloride.

I ask because upon checking one of my precipitations with google images I see that most of the copper chloride powders are blue green. Mine is a clear light blue. No greenish tint at all.

This precipitate came from the following reactions.
1. 50% Hcl (8m 24%) and 50% hydrogen peroxide (6%) then pure copper metals submerged in solution with partial dissolving, about 10% loss of metal. The copper chloride from this is too irresponsible for the drain so I saturated the whole solution with sodium bicarbonate until nothing left was fizzing. I then Filtered out of curiosity and washed the precipitate with 50% distilled water and 50% denatured alchohol and let dry. (I am always curious thinking that something is too good to waste)

Thankyou.

Whoops

CHRIS25 - 7-4-2012 at 05:32

Actually this should be copper carbonate. But I made copper carbonate some weeks ago, green.

White Yeti - 7-4-2012 at 07:22

It all has to do with what the Cu+2 ion complexes with in solution. I don't know much about coordination chemistry (I'm more of a biochem person) but the colour of transition metals is dependent on what coordination complex it forms in solution. IIRC CuCl2 can form [Cu(Cl)4]-2 in solution when there is excess chloride, and that complex just happens to be green.

As if that wasn't enough copper can exist as Cu+, and the chemistry is different.

If you want to make yet another colour, try mixing some copper carbonate in some ammonia solution, the resulting complex is a striking deep blue colour.

[edit]
I think it would be easier to answer this question if you posted a picture of the product.

[Edited on 4-7-2012 by White Yeti]

CHRIS25 - 7-4-2012 at 07:45

Quote: Originally posted by White Yeti  
It all has to do with what the Cu+2 ion complexes with in solution. I don't know much about coordination chemistry (I'm more of a biochem person) but the colour of transition metals is dependent on what coordination complex it forms in solution. IIRC CuCl2 can form [Cu(Cl)4]-2 in solution when there is excess chloride, and that complex just happens to be green.

As if that wasn't enough copper can exist as Cu+, and the chemistry is different.

If you want to make yet another colour, try mixing some copper carbonate in some ammonia solution, the resulting complex is a striking deep blue colour.

[edit]
I think it would be easier to answer this question if you posted a picture of the product.

[Edited on 4-7-2012 by White Yeti]


Hallo here is a photo:
Hi, I am clicking on theedit. Also my photo is not uploading. It is below 800 x 2500 it is 400kb iI have tried both jpeg and png, it says in the upload photo section that my photo is there but when I press on Post nothing ever happens.!!!!!!!!

[Edited on 7-4-2012 by CHRIS25]

Hexavalent - 7-4-2012 at 07:48

Photo?

Also, please use the edit feature on posts as opposed to double-posting. Just click on the 'edit' icon on the top right hand of your post box, and re-design the message as you wish.

CHRIS25 - 7-4-2012 at 07:54

Quote: Originally posted by Hexavalent  
Photo?

Also, please use the edit feature on posts as opposed to double-posting. Just click on the 'edit' icon on the top right hand of your post box, and re-design the message as you wish.


Frustrations abound such a simple procedure made so complicated really. I have uploaded hundreds of photos before but nothing is happening here on this forum. The choose file area accepts my photo but it will not take it any further.

DJF90 - 7-4-2012 at 08:35

I understand what you mean by the colours CHRIS - I made some basic copper carbonate by the method in Brauer at work, and I obtained a blue-turqoise material. The commercial stuff I later bought from aldrich was about the same colour, yet you see samples of a malachite colour (malachite itself is the same material in mineral form).

Mine looks similar to this:
http://www.chemmfg.com/copper-carbonate-basic-copper-carbona...

Yet looking through google images most of the samples look like this:
http://www.pyroguide.com/index.php?title=Copper_carbonate_(basic)

Interestingly, I observed that using a large excess of sodium carbonate, a royal blue solution is obtained, which upon stirring for a period at ~80*C plates out a dark material onto the surface of the glass, which I assume is copper (II) oxide? I just found it strange that it plated onto the glass and not precipitate in the bulk of the solution.

[Edited on 7-4-2012 by DJF90]

CHRIS25 - 7-4-2012 at 09:14

Quote: Originally posted by DJF90  
I understand what you mean by the colours CHRIS - I made some basic copper carbonate by the method in Brauer at work, and I obtained a blue-turqoise material. The commercial stuff I later bought from aldrich was about the same colour, yet you see samples of a malachite colour (malachite itself is the same material in mineral form).

Mine looks similar to this:
http://www.chemmfg.com/copper-carbonate-basic-copper-carbona...

Yes I suppose I have copper carbonate again, that actually is what I am supposed to have from making the copper chloride safe to put down a household drain. Mine also looks like this as in your first web page, but the blue is quite paler.

Yet looking through google images most of the samples look like this:
http://www.pyroguide.com/index.php?title=Copper_carbonate_(basic)

Interestingly, I observed that using a large excess of sodium carbonate, a royal blue solution is obtained, which upon stirring for a period at ~80*C plates out a dark material onto the surface of the glass, which I assume is copper (II) oxide? I just found it strange that it plated onto the glass and not precipitate in the bulk of the solution.

[Edited on 7-4-2012 by DJF90]

bfesser - 7-4-2012 at 10:01

<a href="http://en.wikipedia.org/wiki/Coordination_compound#Color" target="_blank">Coordination</a> <img src="../scipics/_wiki.png" /> aside, <a href="http://en.wikipedia.org/wiki/Color" target="_blank">color</a> <img src="../scipics/_wiki.png" /> (perceived) will vary with particle size/shape, <a href="http://en.wikipedia.org/wiki/Hydrate" target="_blank">hydration</a> <img src="../scipics/_wiki.png" />, lighting conditions, impurities, etc.

In my experience, the greeener hues of <a href="http://en.wikipedia.org/wiki/Copper(II)_carbonate" target="_blank">copper(II) carbonate</a> <img src="../scipics/_wiki.png" /> samples contain higher proportions of <a href="http://en.wikipedia.org/wiki/Copper(II)_hydroxide" target="_blank">copper(II) hydroxide</a> <img src="../scipics/_wiki.png" />, the browner&mdash;<a href="http://en.wikipedia.org/wiki/Copper(II)_oxide" target="_blank">copper(II) oxide</a> <img src="../scipics/_wiki.png" />.

See also:
<a href="http://en.wikipedia.org/wiki/Malachite" target="_blank">Malachite</a> <img src="../scipics/_wiki.png" />
<a href="http://en.wikipedia.org/wiki/Azurite" target="_blank">Azurite</a> <img src="../scipics/_wiki.png" />
<a href="http://en.wikipedia.org/wiki/Copper(II)_acetate" target="_blank">Copper(II) acetate</a> <img src="../scipics/_wiki.png" />

I <a href="viewthread.php?tid=14644&page=7#pid240639">recently posted</a> two photos of copper(II) acetoxybenzoate, showing variation of color with particle size/shape.

[Edited on 7/9/13 by bfesser]