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CHRIS25
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Copper carbonate - controlling the colour
A year ago I prepared copper carbonate, one is blue, the other green.
The blue is 2Cu(CO3)(OH)2
The green is Cu(CO3)(OH)2
This mimics azurite and malachite respectively.
My Question is this, A year ago I got these colours by accident, but I want to control the output now. The green I produced underwent oxidation, how,
I have no idea, but the blue did not.
Duh! of corse it did not oxidise, they both have the same amount of valence electrons, so this means that there are Two copper carbonates to one
hydroxide in the blue, but how?
No Answers - just give me something to think about so I could work this out for myself.
[Edited on 26-11-2014 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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DJF90
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Brauer has some conditions you can look at. As I recall, its a matter of temperature and precipitant (carbonate, hydroxide etc). If you heat it too
hot you get copper (II) oxide (been there, done that...). Stoichiometry almost definately plays a role too.
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CHRIS25
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Yes pages 1024 - 1026, very interesting and I am looking into that now. Obviously the way to go I will experiment. But I prepared both the blue and
green in exactly the same manner: From my notes so far back, like this: 50gm Copper sulphate and 35gm sodium bicarbonate gave me green.
Unfortunately no further notes on how I got the blue.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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blogfast25
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Quote: Originally posted by CHRIS25 ![](images/xpblue/lastpost.gif) | A year ago I prepared copper carbonate, one is blue, the other green.
The blue is 2Cu(CO3)(OH)2
The green is Cu(CO3)(OH)2
This mimics azurite and malachite respectively.
[snip]
Duh! of corse it did not oxidise, they both have the same amount of valence electrons, so this means that there are Two copper carbonates to one
hydroxide in the blue, but how?
|
2Cu(CO3)(OH)2 doesn't make any sense, actually. I can see from the page code you're using the rectangular brackets, not the
proper angular ones. Try again? I think it is 2CuCO<sub>3</sub>.Cu(OH)<sub>2</sub>.
Cu(CO<sub>3</sub> (OH)<sub>2</sub> does also not make sense.
Must be Cu<sub>2</sub>(CO<sub>3</sub> (OH)<sub>2</sub>, I think...
Correct about the oxidation though: no further oxidation possible, all credit cards maxed out!
HINT: the bluest one is the one with the highest OH to CO<sub>3</sub> ratio and that reflects preparation conditions, I believe. Try to
use a solution of NaOH + Na2CO3, in the ratio that OH/CO3 occurs in the mineral, as precipitating agent? Just a thought, you know?
[Edited on 26-11-2014 by blogfast25]
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Texium
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I've made a few different shades of CuCO<sub>3</sub> too. I've found that using bicarbonate leads to a greener product than using
carbonate does. I think using a more dilute solution would help produce a greener color too. It all seems to be dependent on the pH of the solution.
At some point I think I'll run an exhaustive test tube scale experiment on the different shades of this compound, and maybe make a video about it to
be posted on the Rador Labs channel.
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CHRIS25
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zts16 - well I will be doing some tests and experiments so expect a post back here at he end of the week. With pictures hopefuly.
Blogfast26 - I see by the chemical formulas for each rock the following:
Malachite = Cu2(CO3)(OH)2
Azurite = Cu3(CO3)2(OH)2
source: http://www.galleries.com/Azurite
So the azurite has the same amount of hydroxides, but one more copper and two more carbonates - I have to admit I am confused now. No problems about
experimenting, I just don't understand the mechanism here.
[Edited on 27-11-2014 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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blogfast25
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Quote: Originally posted by CHRIS25 ![](images/xpblue/lastpost.gif) | No problems about experimenting, I just don't understand the mechanism here.
[Edited on 27-11-2014 by CHRIS25] |
When I think about it, like marble, these minerals are almost certainly metamorphic rocks. They may have started out from the same basic copper
carbonate and then altered in geological processes into the two azurite/malachite variations. If this is so then simple lab synthesis may not be,
erm... simple! During their metamorphosis different conditions of temperature and (high!) pressure would have caused the different chemical
compositions to arise. That's not something that can be controlled by precipitation conditions alone.
http://en.wikipedia.org/wiki/Metamorphic_rock
Try writing the stoichiometrical equations for the formation of azurite and malachite from CuSO4 and mixtures of NaOH and Na2CO3 solutions.
Hint: Malachite can be re-written as CuCO3 + Cu(OH)2, Azurite as 2 CuCO3 + Cu(OH)2.
[Edited on 27-11-2014 by blogfast25]
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blogfast25
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Quote: Originally posted by zts16 ![](images/xpblue/lastpost.gif) | At some point I think I'll run an exhaustive test tube scale experiment on the different shades of this compound, and maybe make a video about it to
be posted on the Rador Labs channel. |
That would be an interesting thing to do. What matters of course is the dry colour of the stuff, not the wet precipitate.
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Texium
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Quote: Originally posted by blogfast25 ![](images/xpblue/lastpost.gif) | Quote: Originally posted by zts16 ![](images/xpblue/lastpost.gif) | At some point I think I'll run an exhaustive test tube scale experiment on the different shades of this compound, and maybe make a video about it to
be posted on the Rador Labs channel. |
That would be an interesting thing to do. What matters of course is the dry colour of the stuff, not the wet precipitate.
| Yes, the samples will be thoroughly dried before making any conclusions. I think I'll also compare the
samples to some copper hydroxide as a sort of control, if I can dry it without having it decompose.
Also, I have a natural copper ore chunk that I got at a rock shop which consists of a mixture of malachite and azurite (mostly azurite), so it seems
like both are formed under the same conditions to a certain extent.
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CHRIS25
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CuSO4+2NaHCO3 = Cu(HCO3)2 + Na2SO4
But the same equation above can also yield: CuCO3 + Na2SO4 + H2O + CO2
YET CuSO4 + equally same amount of NaHCO3 = CuCO3 + NaHSO4 +H2O + CO2 (actually the
bisulphate here would be nice to have as by-product).
As far as the 2 moles to one mole ratio is concerned looking at the first equation that yields the copper bicarbonate is not possible since I read
that it can not exist? so this is essentially a copper hydroxide mix whereas the second equation yields......yep, too many questions. Anyway my
interest deepens, better get up and get moving and get mixing.
Out of interest: I painted some green copper carbonate after grinding and onto watercolour paper, (using linseed oil), it worked beautifully, and
after abrasive action and wetting the paper after 24 hours to see if it would come off - it does not budge.
[Edited on 27-11-2014 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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Quote: Originally posted by CHRIS25 ![](images/xpblue/lastpost.gif) |
Out of interest: I painted some green copper carbonate after grinding and onto watercolour paper, (using linseed oil), it worked beautifully, and
after abrasive action and wetting the paper after 24 hours to see if it would come off - it does not budge.
[Edited on 27-11-2014 by CHRIS25] |
At least the carbonate only decomposes in the presence of heat or water. If you painted an ocean, you'd come back the next day to continue and you'd
see the most morbid thing ever.
Fear is what you get when caution wasn't enough.
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CHRIS25
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‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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blogfast25
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Stoichiometries, for what it's worth:
Malachite:
Na2CO3 + 2 NaOH + 2 Cu<sup>2+</sup> == > CuCO3.Cu(OH)2 + 4 Na<sup>+</sup>
Azurite:
4/3 Na2CO3 + 4/3 NaOH + 2 Cu<sup>2+</sup> == > 2/3 (2CuCO3.Cu(OH)2) + 6 Na<sup>+</sup>
So for Malachite the ratio of carbonate to hydroxide would be 0.5, for Azurite it would be 1. Worth a try...
It would not be hugely difficult to determine approx. Cu content in these precipitates, as these compounds decompose to CuO on calcining quite easily.
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CHRIS25
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((Try writing the stoichiometrical equations for the formation of azurite and malachite from CuSO4 and mixtures of NaOH and Na2CO3 solutions.
Hint: Malachite can be re-written as CuCO3 + Cu(OH)2, Azurite as 2 CuCO3 + Cu(OH)2.))
If that is the answer to what you asked me to do above then no way could I have worked that out.
Also ((So for Malachite the ratio of carbonate to hydroxide would be 0.5, for Azurite it would be 1.)) Don't understand, what is the ratio here? 1
carbonate to 0 hydroxide?
[Edited on 27-11-2014 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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blogfast25
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Quote: Originally posted by CHRIS25 ![](images/xpblue/lastpost.gif) | Also ((So for Malachite the ratio of carbonate to hydroxide would be 0.5, for Azurite it would be 1.)) Don't understand, what is the ratio here? 1
carbonate to 0 hydroxide?
|
For malachite we found Na2CO3 + 2 NaOH, so that is a molar ratio of carbonate:hydroxide of 1:2 (' 1 divided by 2') or 0.5.
For Azurite we found 4/3 Na2CO3 + 4/3 NaOH , so that is a molar ratio of 4/3:4/3 of 1:1 or 1.
These would be interesting ratios to use as precipitant solutions: prepare a solution that contains 1 mol (or multiple of) Na2CO3 and 2 mol (or the
same multiple of) NaOH and add it to a solution of CuSO4. Observe.
Now do the same with solution that contains 1 mol (or multiple of) Na2CO3 and 1 mol (or the same multiple of) NaOH and add it to a solution of CuSO4.
Observe and compare.
[Edited on 27-11-2014 by blogfast25]
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CHRIS25
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Ok, I understood my own but I was thrown by the way you wrote yours ie 4/3 (1.33:1.33 is how I saw that) and I was seeing 2:1 but seeing yours as
0.5. Anyway, phew, sometimes goes over my head, I actually am getting ready to do exactly what you had suggested. A 2:1 and a 1:1. Out of de-ionized
water so will have to wait till tomorrow.
Is it me or did we just take the long windy country road to Dublin?
What is defined as strong glass in this situation, (since I have no idea how to relate to the concept of 5 atm's. 1 = where we live that's it.
"""A solution of copper nitrate is mixed with an excess of pieces
of chalk, and the mixture is placed in a large-diameter tube of
strong glass connected to a mercury manometer. The tube is then
sealed. The azurite forms at room temperature when the liberated
CO2 creates a pressure of 5-8 atm."""
[Edited on 27-11-2014 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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blogfast25
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Quote: Originally posted by CHRIS25 ![](images/xpblue/lastpost.gif) | Is it me or did we just take the long windy country road to Dublin?
What is defined as strong glass in this situation, (since I have no idea how to relate to the concept of 5 atm's. 1 = where we live that's it.
"""A solution of copper nitrate is mixed with an excess of pieces
of chalk, and the mixture is placed in a large-diameter tube of
strong glass connected to a mercury manometer. The tube is then
sealed. The azurite forms at room temperature when the liberated
CO2 creates a pressure of 5-8 atm."""
|
ALL roads to Dublin are country roads. When we drove from Holyhead to Dublin a few years back we were promised a motorway. It didn't come, not until
Dublin either. Or rather, what we had been on, a dual carriage way, was IT. ![;)](./images/smilies/wink.gif)
1 atm is the pressure you'd experience when you dive to 10.33 m, very tolerable. Most ordinary glass wouldn't flinch at that pressure. 5 - 8 atm:
multiply accordingly. At 50 m you already need to decompress to avoid the 'bends'.
Well, actually at 10.33 m you experience 2 atm, one from the air above the water, one from the water itself.
Does that make it more 'real'?
[Edited on 27-11-2014 by blogfast25]
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CHRIS25
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Holyhead? That must have been an amazing trip, a dual carriageway across the irish sea. They only just built a motorway from Cork to Dublin 5 years
ago!
So, on the definition of strong glass in the above for 5 atm. My guess is that a sealed douwe egberts (you know what that is) jar would have to have
a lot of pressure generated by carbon dioxide before it succumbed?
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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CHRIS25
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Preliminary Results of Tests
3 Jars received 150 mLs water each + 0.15mol of Na2CO3 + 0.15mol CuSO4 each. Then each Jar received a 2, 1, and none
NaOH respectively.
Images need no explanation, though the jar with 1mol NaOH began to release CO2 a few minutes after the photos were taken, and the jar with
no NaOH exploded immediately (not literally). The colours are zeer opmerkelijk (noteworthy), Blue to blue green to green.
Will filter and dry, and do some other tests but wanted to post these images straight away.
It must be said that it appears as if not all the copper sulphate has dissolved in the jar with 2mol NaOH. Adding more water made no difference it
appears that precipitating copper carbonate here is suppressed. It definitely seems that the jar with 2mol NaOH Prevents copper carbonate from
precipitating and instead we have a blue-green Copper Hydroxide layer sitting on top of undissolved copper sulphate. Anyway I can filter this and
allow the copper hydroxide to react with the air CO2 to form copper carbonate. See what colour we get.
![CuCarbonate.jpg - 47kB](https://www.sciencemadness.org/whisper/files.php?pid=372643&aid=35475)
[Edited on 28-11-2014 by CHRIS25]
[Edited on 28-11-2014 by CHRIS25]
[Edited on 28-11-2014 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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blogfast25
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That journey did indeed involve a Seacat ferry, traveling on water, not an A-type road. My bad.
I'm a bit at a loss to explain the CO<sub>2</sub> evolutions in 2 and 3. It appears that in those cases a hydroxycarbonate was formed but
why does some of the carbonate convert to CO<sub>2</sub>? It's not clear to me right now.
I can only come up with:
Cu<sup>2+</sup>(aq) + CO<sub>3</sub><sup>2-</sup>(aq) + H<sub>2</sub>O(l) ===>
Cu(OH)<sub>2</sub>(s) + CO<sub>2</sub>(g)
That must be it. But why no bubbles in case 1?
Oh, and I wouldn't recommend coffee jars or jam jars at 5 atm! You'd need at least thick walled borosilicate glass to be on the safe side. Do you have
a link for that Azurite preparation you referenced? (Edit: found it. From Brauer's 'Inorganic Preparative Chemistry'. A Very Authorative source,
indeed)
http://books.google.co.uk/books?id=Pef47TK5NfkC&pg=PA102...
[Edited on 28-11-2014 by blogfast25]
[Edited on 28-11-2014 by blogfast25]
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CHRIS25
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I suppose by looking at the reaction equations the 2mol NaOH solution just makes the copper hydroxide and the sodium and carbonate ions do not
participate at all?
When NaOH is less, or absent the it seems that the reaction proceeds. It was noticeable that the 1mol NaOH solution took about 2 minutes before there
was any liberation of carbon dioxide.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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FYI, here's an old thread that relates some experience on this subject:
http://www.sciencemadness.org/talk/viewthread.php?tid=5529&a...
The single most important condition for a successful synthesis is good mixing - Nicodem
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CHRIS25
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This thread where you said: "...the more carbonate the more green.." is what I have seen. The solution without the NaOH gave more green to the
filtrate. The solution with more NaOH gives more blue. Also the solution without the NaOH yielded plenty of CO2 but with the NaOH no CO2 was
visible, on the contrary I have copper hydroxide layer on top of very deep blue, I presume copper sulphate.
The formula for malachite has less carbonate than the blue azurite. So an apparent contradiction appears which I am certain is no contradiction - I am
unable to understand any of this due to the usual lack of knowledge.
[Edited on 28-11-2014 by CHRIS25]
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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blogfast25
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Chris:
That Azurite preparation method by Brauer could be carried out successfully in a PET C*ke bottle.
This here fellow pumps up a PET drinks bottle to 120 psi with CO2 without blinking: that’s about 8 bar. Other references confirm these values.
https://www.youtube.com/watch?v=X6o561T7N6I
And this one:
https://www.youtube.com/watch?v=ZBJ-Wd5RVGI
180 psi (12.5 bar) and beyond:
https://www.youtube.com/watch?v=D78K3sW-1fA
The reaction equation is:
3 Cu(NO3)2 + 3 CaCO3 + H2O === > 2 CuCO3.Cu(OH)2 + 3 Ca(NO3)2 + CO2
(reaction equation edited: H2O added)
So with each mol of Azurite is produced also 1 mol of CO2. As in the Brauer method we can use that to build up pressure to the needed level.
A 2 L bottle (at STP) contains about 2/24 = 0.08333… mol air. By adding some moles of CO2 we can increase pressure. According the Ideal Gas Law p V
= n R T (with p pressure, V volume, n number of moles, R the Ideal Gas Constant and T the temperature (in Kelvin)) and since as we add the CO2 without
changing neither the volume nor the temperature of the bottle we can say:
p<sub>1</sub> / p<sub>2</sub> = n<sub>1</sub> / n<sub>2</sub>, with p<sub>1</sub> = 1 bar
and n<sub>1</sub> = 0.0833.
If we set the final pressure p<sub>2</sub> at a safe 5 bar, we can calculate n<sub>2</sub> = 5 x 0.0833 = 0.417. Subtract from
that n<sub>1</sub> and the number of moles of CO2 to be added to the bottle to obtain 5 bar pressure is 0.417 – 0.0833 = 0.333 mol CO2.
That also corresponds to 0.333 mol Azurite or about 0.333 mol x 344.6 g/mol = 115 g of Azurite. The reaction would require 3 x 0.333 = 1 mol Cu(NO3)2
and the excess of limestone.
Quite neat!
You meant the filter cake, not the filtrate, right?
[Edited on 28-11-2014 by blogfast25]
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CHRIS25
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That's a whole lot of unfamiliar maths, but the idea is something I would like to try. Just need to find fizz giz tops and a CO2 extinguisher for dry
ice. Thankyou for the links Gert, something new.
‘Calcination… is such a Separation of Bodies by Fire, as makes ‘em easily reducible into Powder; and for that reason ‘tis call’d by some
Chymical Pulverization.’ (John Friend, Chymical Lectures London, 1712)
Right is right, even if everyone is against it, and wrong is wrong, even if everyone is for it. (William Penn 1644-1718)
The very nature of Random, Chance development precludes the existence of Order - strange that our organic and inorganic world is so well defined by
precision and law. (me)
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