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aga
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My hypothesis is that the Thermochemistry is OK, in that Malachite => Azurite in a CO2 environment reaction Will happen at STP.
Your experiment is using augmented pressure as well as a saturated CO2 environment, implying that the Azurite reaction might only take place if the
Kinetics are agreeable at 5+ atm.
If Malachite + CO2 => Azurite at 1 atm, then case proven.
So a simple experiment would be to make some Malachite, then take half of the sample and subject it to a stream/atmosphere of CO2 for a while.
OK. I think i can do that (famous last words).
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blogfast25
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Aga:
As indicated in my earlier post I think Malachite and Azurite are in equilibrium according to:
3 Cu2CO3(OH)2(s) + CO2(g) < === > 2 Cu3(CO3)2(OH)2(s) + H2O(l)
According to the Le Chatelier Principle, if you increase the pressure in that system it will respond by trying to undo that change. Here it does that
by absorbing some of the CO2. The overall pressure decreases because the right hand side of the equation is much less voluminous than the left hand
side.
What I observe is in agreement with Le Chatelier and that means that applying CO2 in atmospheric conditions will not convert Malachite to
Azurite because there is no driving force.
But by all means prove me wrong, empirically.
[Edited on 15-12-2014 by blogfast25]
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aga
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I'll give it a go and see what happens.
Whether one is right, wrong or simply misled shall be known by said go-ing-happeneing.
[Edited on 15-12-2014 by aga]
I very much like CHRIS25's posts.
So much to actually DO !
[Edited on 15-12-2014 by aga]
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CHRIS25
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@Gert
Quote: ""BTW, that second structure labelled 'carbonic acid copper hydrate' is simply baloney. Plain wrong. The real structure involves Cu2+ ions,
CO32- ions and OH- ions and no water molecules. Going by that structure the copper wouldn't even carry any charge at all!!!"" Unquote
Then I am truly puzzled, would you mind having a look at these, because I do not understand this at all then: Plus the above molecular structure is
listed clearly with the same formula on chemspider, the one you that you use for malachite copper carbonate. Although I do admit they are MISSING a
diagrammatic Carbon atom somewhere.
http://pubchem.ncbi.nlm.nih.gov/compound/3081961?from=summar...
http://www.chemicalregister.com/MALACHITE_CU2_CO3_OH_2/Suppl...
‘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:
BOTH references are WRONG: they start off from the wrong molecular formula of: CH6Cu2O5
But it actually is Cu2(CO3)(OH)2!
CH6Cu2O5 has 4 H too many! That explains why in their faulty structure model the Cu would be chargeless, which is clearly IMPOSSIBLE.
It's good practice to always include a link to any information you're unearthed, so people can check context.
Don't be too surprised by this: science isn't perfect and scientific literature contains errors, often of the 'cut 'n paste' type.
Later today: the suspected role of water in the Malachite - Azurite transformation.
[Edited on 16-12-2014 by blogfast25]
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CHRIS25
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Very surprised by this. But thanks Gert. I have used chemspider quite a lot and thought it a completely trustworthy source for learning.
Ok, I tested both by copper carbonates for copper content. One is thoroughly Blue, the other thoroughly Green. These are the results and the Blue
results really surprised me and have not had time to work out why yet. I tested the blue carbonate a second time believing that I made a mistake
somewhere, no I can not see a mistake.
Everything in Grams, saves an extra key punch!
GREEN:
Empty Beaker and test tube = 110.89
Carbonate weight = 1.02
Beaker/Test tube filled with conc sulphuric plus Carbonate = 126.71
Weight after reaction is completed = 110.98
Copper content = 0.09
BLUE: Test A
Empty Beaker and test tube = 110.85
Carbonate weight = 1.03
Beaker/Test tube filled with conc sulphuric plus Carbonate = 125.44
Weight after reaction is completed = 109.64
Copper content? Something has been added? = 1.21 or not all the acid was consumed?
Blue: Test B
Empty Beaker and test tube = 111.35
Carbonate weight = 1.16
Beaker/Test tube filled with conc sulphuric plus Carbonate = 125.53
Weight after reaction is completed = 109.24
Copper content? Something has been added? = 2.11 or not all the acid was consumed?
The most noticeable thing about these reactions with sulphuric acid was that the Blue carbonate liberated a huge amount of Carbon dioxide, whereas the
Green liberated just a gentle fizz. Compare a firework banger to a firework rocket Also the Green upon completion, stayed green. the Blue however turned a milky white upon completion, whereupon addition of water turned the white
into a blue again.
[Edited on 16-12-2014 by CHRIS25]
[Edited on 16-12-2014 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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aga
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Quote: Originally posted by aga  | | My hypothesis is that the Thermochemistry is OK, in that Malachite => Azurite in a CO2 environment reaction Will happen at STP.
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No. It doesn't.
I made some copper carbonate today and bubbled CO2 through it for a couple of hours.
Nothing happened.
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blogfast25
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Chris:
Interesting what you're trying to do there and decent reasoning but with flaws. I really don't see how the copper content can be deduced from it,
though.
I'm still at work so just wanted to post my water spiel quickly. Will look at your numbers tonight.
The role of water in:
3 Cu2CO3(OH)2(s) + CO2(g) < === > 2 Cu3(CO3)2(OH)2(s) + H2O(l)
Left we have 6 OH ions, 3 CO3 ions and one CO2, right we have 4 OH ions, 4 CO3 ions and one H2O. So it looks like we’ve combined 2 OH ions with a
CO2, to form another CO3 ion and 1 water.
Imagining how 2 OH<sup>-</sup> + CO2 = H2O + CO<sub>3</sub><sup>2-</sup> is really not easy.
Enter… the water.
As we know CO2 is much more soluble in water when under pressure. CO2 in water forms carbonic acid acc. the equilibrium:
H2O(l) + CO2(aq) < === > H2CO3(aq)… (I)
Carbonic acid is a weak acid and its two deprotonations can be summarised as:
H2CO3(aq + 2 H2O (l) < === > 2 H3O+(aq) + CO<sub>3</sub><sup>2-</sup>(aq)… (II)
And now we have a way to eliminate 2 OH ions:
2 OH<sup>-</sup> + 2 H3O+(aq) === > 4 H2O(l)… (III)
Add up (I), (II) and (III) and eliminate redundancies on both sides:
CO2(aq) + 2 OH<sup>-</sup> === > CO<sub>2</sub><sup>2-</sup>(aq) + H2O(l)… (IV)
The water used in (I) and (II) is fully returned in (III), so it act as a catalyst, making (IV) possible.
This is another reason why I don’t believe converting Malachite to Azurite in a dry stream of CO2 will work: presence of water is essential.
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blogfast25
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| Quote: Originally posted by CHRIS25 | GREEN:
Empty Beaker and test tube = 110.89
Carbonate weight = 1.02
Beaker/Test tube filled with conc sulphuric plus Carbonate = 126.71
Weight after reaction is completed = 110.98
Copper content = 0.09
BLUE: Test A
Empty Beaker and test tube = 110.85
Carbonate weight = 1.03
Beaker/Test tube filled with conc sulphuric plus Carbonate = 125.44
Weight after reaction is completed = 109.64
Copper content? Something has been added? = 1.21 or not all the acid was consumed?
Blue: Test B
Empty Beaker and test tube = 111.35
Carbonate weight = 1.16
Beaker/Test tube filled with conc sulphuric plus Carbonate = 125.53
Weight after reaction is completed = 109.24
Copper content? Something has been added? = 2.11 or not all the acid was consumed?
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Chris, you're going to have to describe in more detail what exactly you've done, to try and make sense of these numbers.
The way I see it, you are actually trying to determine the CO2 content of these samples by driving off the CO2 with conc. H2SO4 and weighing before
and after. But without further explanation the numbers don't add up.
For Malachite the reaction would be:
Cu2CO3(OH)2 + 2 H2SO4 === > 2 CuSO4 + CO2 + 2 H2O
For Azurite:
Cu3(CO3)2(OH)2(s) + 3 H2SO4 === > 3 CuSO4 + 2 CO2 + 4 H2O
[Edited on 16-12-2014 by blogfast25]
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CHRIS25
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Ah sorry. Still learning to be more meticulous and in presenting data properly. (untrained in that but training myself as I go along); Ok I weighed
an empty beaker with an empty test tube in it. I then weighed out the copper carbonate. I then poured in to the test tube 11 mL 98% sulphuric acid
and weighed the beaker again that now contains the test tube with acid and the copper carbonate. Poured the acid directly into the carbonate in the
beaker, waited for completion and then weighed the beaker with the completed reaction inside.
The following: CuCO3 + H2SO4 = Cu + H2O + CO2 +SO4
Theoretically since all the dioxide has been driven away we are left with a solution of sulphate ions, water and copper 2+ ions.
Yes this does give us the amount of Copper, and here is how:
We know that in GREEN Test that 126.71 - 110.89 = 14.80 is the weight of the acid I put in. We also know that 126.71 - 110.98 = 15.73 is the weight
AFTER the reaction is completed; logically then 15.73 (After completion) - 14.80 (weight of acid) = 0.93 can only be the Copper content. And I did
this all by myself - pride comes before a knock on the head with a stoichiometric sledgehammer?
PS, I like what you have deduced and demonstrated above, it makes sense to me (that is a miracle you know).
[Edited on 16-12-2014 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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Unfortunately the above is wrong in many ways. I'll try and keep it short.
1. You start from a false premise: your carbonate is a hydroxycarbonate, NOT CuCO3. It makes a WHOLE lot of difference.
2. "CuCO3 + H2SO4 = Cu + H2O + CO2 +SO4" is NOT a reaction equation at all. The correct ones are in my last post (bottom).
3. "We know that in GREEN Test that 126.71 - 110.89 = 14.80 is the weight of the acid I put in"..
Nope. Above that you wrote: "Beaker/Test tube filled with conc sulphuric plus Carbonate = 126.71"
So that difference (126.71 - 110.89) is acid PLUS carbonate, not just acid.
You are, slightly clumsily, trying to determine the CO2 content, by driving it off and doing a weight difference (before - after). That's fine. But do
not believe that from that alone you can determine copper content.
I suggest you run it again, as follows.
1. weigh beaker empty (W1)
2. add about 1 g carbonate and weigh again (W2)
3. Add empty test tube to beaker containing the carbonate and weigh again (W3)
4. Add 11 ml conc H2SO4 to test tube and weigh again with the beaker and the carbonate in it (W4)
5. Empty test tube in beaker, set empty test tube aside (don't clean or wash it!), allow to react. Then add empty test tube back to the beaker with
the reacted mixture and weigh the ensemble (W5).
From these weights can be calculated how much CO2 the carbonate sample has lost, and thus the CO2 content.
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DraconicAcid
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Following that, if you allow the solution to evaporate to give copper(II) sulphate pentahydrate, you can weight that and estimate the copper content
of the original sample.
Please remember: "Filtrate" is not a verb.
Write up your lab reports the way your instructor wants them, not the way your ex-instructor wants them.
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aga
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Currently i have a high pressure experiment running to see if Azurite will be made.
(essentially a copy of blogfast25's, but in copper piping.)
As a test i tried heating the part of the apparatus containing the carbonate using a blowtorch.
Pretty quickly the result was copper/copper oxide as a brown/black residue.
It would appear that Natural Azurite is not formed under great temperatures, so chemical mix and pressure are what remain as the variables.
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CHRIS25
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Tests Re-done
So, the sledgehammer was not that bad considering my infantile reasoning. Anyway, here are the new tests, with the same Pattern of results and same
sort of consistency. The same beaker and test tube was used, washed only after Completion of First test and not in between. The same 10.5 mL 98% acid
used in both tests. Each stage was weighed minimum of 3 times by removing off the scales and placing back on to allow for minor discrepencies and to
double check absolute accuracy. Plus both reactions were allowed to stand for exactly 10 minutes each before final weight was taken.
----------------------------------------------------------------BLUE-----------GREEN
Weight Beaker empty---------------------------------------95.4-------------95.4
Weight Beaker + CO3---------------------------------------96.9-------------96.6
Weight Bker + empty TestTube + CO3----------------112.4-----------112.2
Weight Bker + TestTube + Acid + CO3----------------131.3-----------131.0
Weight Bker + empty TestTube After reaction------131.3-----------115.1
OBSERVATIONS:
The Blue Carbonate produced a plume of smoke in an instant, after completion of reaction a milky white solution which precipitated a white fine
powder, this I deduce to be Anhydrous copper sulphate (which happens to be white and by the fact that sulphuric acid is very hygroscopic).
The Green carbonate produced mild fizzing and clearly this was carbon dioxide. The solution stayed green and it also precipitated a green fine
powdery residue.
Don't ask me to interpret the results - bit fed up with being the forum idiot! But I find the above both interesting and unexpected result from the
Blue. Interestingly I made the above blue with NaHCO3 and the green was made with Na2CO3 but without NaOH. I also
made another blue with just Na2CO3 + NaOH
I made a Blue-green Carbonate by doubling the amount of Na2CO3 but no NaOH added.
Whether any of the above is useful to know I don't know to be honest.
‘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, thanks very much. I will interpret these data tonight. And no, you're not the 'forum idiot', just still a beginner. Rome wasn't built in a day
either.
| Quote: Originally posted by DraconicAcid | | Following that, if you allow the solution to evaporate to give copper(II) sulphate pentahydrate, you can weight that and estimate the copper content
of the original sample. |
Copper sulphate pentahydrate isn't great for gravimetry and he's also got a lot of unreacted conc. H2SO4 in there which would be difficult to
eliminate. It's a recipe for huge errors.
| Quote: Originally posted by aga | Currently i have a high pressure experiment running to see if Azurite will be made.
(essentially a copy of blogfast25's, but in copper piping.)
As a test i tried heating the part of the apparatus containing the carbonate using a blowtorch.
Pretty quickly the result was copper/copper oxide as a brown/black residue.
It would appear that Natural Azurite is not formed under great temperatures, so chemical mix and pressure are what remain as the variables.
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All these copper hydoxycarbonates and hydroxychlorides appear thermo-labile from about 200 - 250 C onwards. But they're more stable than Cu(OH)2 which
starts dehydrating below 100 C, even when still wet.
---------------------
I've found a way to determine the formula of a well-defined copper hydroxycarbonate, say xCuCO<sub>3</sub>.yCu(OH)<sub>2</sub>
with x and y integers, from an accurate determination of CO<sub>2</sub> content. I will give that a whirl tonight or tomorrow.
[Edited on 17-12-2014 by blogfast25]
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blogfast25
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Chris, once again I can’t make head or tails of your numbers: it seems in the first case NO CO2 was lost and in the second case far, far too much.
Something is wrong and I don’t know what it is. You’re right about the white product being anh. CuSO4. I'll be using 50 % H2SO4.
I conducted my own experiment, using this basic copper carbonate.
A 100 ml empty volumetric flask plus funnel was accurately weighed (W1 = 71.00 g). About 4 g of alleged Cu2CO3(OH)2 was added, this gave W2 = 75.04 g.
About 7 ml of water was added to create a slurry and the total weight recorded as W3 = 82.58 g.
Separately 10 ml of 50 v% H2SO4 had been prepared in a measuring cylinder, total weight W4 = 23.65 g. The acid was then bit by bit added to the flask
plus funnel and its content and allowed to react. A blue solution resulted after the fizz and some CuSO4.5H2O crystallised out. The final weight was
W5 = 95.76 g. The weight of the empty measuring cylinder was W6 = 9.66 g.
Photo post-experiment:
Calculations:
From W2 – W1 = 4.04 g we know the weight of copper basic carbonate.
From W6 – W4 = 13.99 g we know the weight of acid added.
From W3 + (W6 – W4) – W5 = 0.81 g we know the amount of CO2 that was released.
The weight percent CO2 in the product was thus 0.81/4.04 x 100 % = 20.0 w%. The theoretical value for Cu2CO3(OH)2 is 19.9 w%.
Now for the determination of x and y.
0.81 g CO2 is 0.81 / 44 = 0.0184 mol CO2, that corresponds to 0.0184 x 123.54 = 2.27 g CuCO3.
The remainder of the 4.04 g of product, i.e. 4.04 – 2.27 = 1.77 g must be Cu(OH)2, or 1.77 / 95.54 = 0.0185 mol.
Gotcha! Because 0.0185 mol Cu(OH)2 / 0.0184 mol CuCO3 = 1 and thus x = y.
So that product does indeed correspond to the formula CuCO3.Cu(OH)2 or Cu2CO3(OH)2
If that Azurite ever finishes (it’s still bubbling away!) I will use this method to estimate composition.
[Edited on 17-12-2014 by blogfast25]
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CHRIS25
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| Quote: Originally posted by blogfast25 | Chris, once again I can’t make head or tails of your numbers: it seems in the first case NO CO2 was lost and in the second case far, far too much.
Something is wrong and I don’t know what it is. You’re right about the white product being anh. CuSO4. I'll be using 50 % H2SO4.
[Edited on 17-12-2014 by blogfast25] |
I can't either ! But this I do know, I did not make any errors in the weights, and I followed a very slow procedure double checking as I went
along. So I have no idea, except that I must have made an obviously very unique copper carbonate! The difference in the reaction dynamics upon
adding the acid give a clue? As I said earlier, the blue one gave an immediate puff of smoke, though probably steam and I will add it gave quite a lot
for such a small amount, whereas the green fizzed away quietly. This is all I can say.
‘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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One BIG problem is for the green one: you lose 15 g, yet used only about 1 g of carbonate!
One word of advice: use 50 % H2SO4, not conc. H2SO4.
[Edited on 17-12-2014 by blogfast25]
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CHRIS25
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| Quote: Originally posted by blogfast25 | The pressure increase that results is governed by the Ideal Gas Law: http://en.wikipedia.org/wiki/Ideal_gas_law
In the case of our reaction we are adding gas to the bottle because the reaction generates CO2, namely 1 mol per every 3 mol of
Cu(NO3)2, at least stoichiometrically speaking.
Since as I know how much Cu(NO3)2 I used (0.3 mol) and what the volume of the bottle is (600 ml, but strictly speaking I need to
account for the volume taken up by the reagents: water, Cu(NO3)2 and limestone) I can use the Ideal Gas Law to predict the end
pressure in the bottle. I designed the experiment to achieve 5 - 8 bar, as prescribed in the method you linked to.
[Edited on 14-12-2014 by blogfast25] |
I've tried finding out the pressure exerted inside a 2 L carbonated water bottle, since I just bought one that actually says 'PET' on the bottom. I
have also tried to understand the ideal gas law and all that maths so that I can work out, as you did, a pressure of 8 bar and how much reactant to
use. Well, needless to say, I can't find answers or work things out here. I simply can not understand how to do those sort of calculations. So for
the first time ever I am asking for the answer: How much copper nitrate could I use in a 2 L bottle without waking up the neighbours in the middle of
the night with a loud bang. How much water should I use and lastly what kind of pressure do you think a 2 L bottle could take anyway?
Also I will be using Limestone flour, this removes any dubious casualties from the equation just in case my own calcium carbonate has other things in
it.
Will re-do that copper carbonate as you suggested in the coming days, this is a week where nothing seems to be going right.
‘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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Third Round Tests
Same Procedure used as previous except Sulphuric acid diluted to 50%, using approx 17 mL (8.5 : 8.5) in each test tube.
Results:
----------------------------------------------------------------BLUE-----------GREEN
Weight Beaker empty-------------------------------------95.8-------------95.8
Weight Beaker + CO3-------------------------------------96.8-------------96.8
Weight Bker + empty TestTube + CO3--------------112.3-----------111.97
Weight Bker + TestTube + Acid + CO3--------------134.65-----------135.22
Weight Bker + empty TestTube After reaction-----134.54-----------135.21
------------------------------------------------CO2 loss -------0.11----------0.01
Ok my measurements and procedure is spot on. No Mistakes not this time. All I can say is that either I should patent my copper carbonate or my
scales are moody. However I must add that I double and re-double the weighing to see if there is any difference. I do notice that just 2 drops of
acid added to the beaker with everything still in there, (I did this at the end to test it), 2 drops change the scale reading from a 0.35 to a 0.67,
very sensitive.
Observations:
The Blue carbonate stayed blue and the precipitate that slowly dissolved stayed blue, the green however surprised me, with dilute acid the green very
slowly (after 5 mins) changed to blue, and the green precipitate also changed from green to blue as it dissolved. The blue did not yield a plume of
steam this time with the addition of acid, both green and blue yielded their dioxide at the same rate.
The whole point of all this is that I am trying to account for the different behaviours between the blue and green carbonates. Both with concentrated
acid and dilute acid, and of course the results. Even if the Green figures are slightly off, the fact is that the blue yielded a lot more carbon
dioxide than the green. And if one looks at the formulas for both blue and green one clearly sees that the Blue has twice as much carbon dioxide to
generate. But why, with concentrated sulphuric acid did the blue not do this? I will do another test using about 5 g of carbonate and compare
concentrated with dilute again just to see whether there is any consistency with those skew-whiff results.
[Edited on 18-12-2014 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, you're definitely getting closer but I think your main problem is one of scale (too small) and possibly some losses you're overlooking. Try
just the blue pigment at a 5 g scale. Make sure none of the fizz (a mist of solution/slurry droplets with CO2) escapes, as that would lead to grave
errors: that's why I used the semi-closed shape of a volumetric flask. You've already experienced the sensitivity of this type of quantitative
experiment, so learn from it.
Can you remind me of the main differences in preparation of the blue and green carbonates? Long thread...
As regards quantities for a 2 L Azurite experiment:
| Quote: Originally posted by blogfast25 |
In a former carbonated drinks PET bottle of 600 ml volume, 0.3 mol of Cu(NO3)2 dissolved in about 100 ml of water and 90 g of small (0.5 - 1 cm)
chunks of clean limestone (about 3 times the stoichiometric requirement) were loaded:
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... simply multiply the quantities I used by 2000/600 = 3.3333. That will develop the same pressure as in my 600 mL bottle experiment (assuming the
method works and the reaction runs more or less to completion). Note that the limestone really does have to be as small chunks, not
powder. Using powder any excess limestone would end up mixed in with the produced Azurite, inseparable from it. By contrast excess limestone
in chunks can simply be sieved out of the reaction products, without contaminating the Azurite precipitate. That's if my reaction ever finishes
because it's still bubbling...
The bottle can withstand approx. twice the pressure the experiment is designed to achieve.
May I ask what Cu(NO3)2 you will use? The Cu(NO3)2 solution should be reasonably neutral (pH no lower than 4 - 5).
[Edited on 18-12-2014 by blogfast25]
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CHRIS25
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Ok Gert thankyou for all that above. Here are my notes:
Na2CO3 + 2NaOH + CuSO4 = Nothing, did not work at all.
Na2CO3 + NaOH + CuSO4 = Blue
Na2CO3 + CuSO4 = Green
CuSO4 + 2NaHCO3 = Blue-Green
CuSO4 + NaHCO3 = Blue (I think, not the colour I am doubting more the method, notes are becoming more organized as time goes
by) And these red lines under my words are annoying, Engalnd infented the spellling and USA should not re-infent itss owne.
Ah copper nitrate, I made it last year, I was even more ignorant then than I am now, so maybe I should re-do another batch?
‘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 |
Ah copper nitrate, I made it last year, I was even more ignorant then than I am now, so maybe I should re-do another batch? |
What physical form is it?
What's important is that you can control the amount of actual Cu(NO3)2 added to the bottle fairly well. Purity is not important. Also, if in doubt,
rather use a little less than too much: it's the amount of Cu(NO3)2 that determines how much CO2 will be developed and thus how much pressure. Too
much could lead to a bursting bottle, not enough and no Azurite may form.
I'm convinced after all this reading and experimenting that all copper hydroxycarbonates formed at atmospheric pressure are of the
Malachite type, no matter how you produce precipitate them. Only CO2 pressure (and water) can lead to the more carbonaceous Azurite.
Another thing that makes me believe this, is in your Brauer (google) reference:
http://books.google.co.uk/books?id=Pef47TK5NfkC&pg=PA102...
… scroll down to where it says:
”Alternate methods [Azurite] a) From a precipitated green basic carbonate under a CO2 pressure of 4 atm.”
In other words, as noted above repeatedly, a slurry of Cu2CO3(OH)2 can be converted with CO2 at 4 atm to Cu3(CO3)2(OH)2 (Azurite), at least acc. this
reference. This weekend I will initiate a test using that method too.
Your CO2 measurements could prove me wrong on my views here (if you get the measurements right, of course!) and I'm almost hoping so.
I think the colour differences you are observing may be due to granulometry differences and other effects, not to fundamental differences in
composition.
For your CO2 measurement woes, using a small chunk of shop bought Malachite, crushed and ground to a powder, could serve as a Standard.
[Edited on 18-12-2014 by blogfast25]
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aga
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Seeing as large quantities are formed naturally, would it not make sense to look up the geological locations in which Azurite forms and deduce the
parameters from there ?
"Found largely in the oxidized portions of copper deposits, it is a secondary mineral formed by the action of carbonated water acting on
copper-containing minerals, or from Cu-containing solutions, such as CuSO4 or CuCl2 reacting with limestones."
Source : http://www.mindat.org/min-447.html
Judging by that data, blogfast25's experiment is bang on the money.
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blogfast25
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Yes, I know about the natural formation process. The experiment may be on the money but it's very slow. Each day I have a look at the bottle and I can
see the supernatant liquid is still quite blue due to unreacted Cu(NO3)2. Bubbles continue to form slowly. I daren't stop the experiment because I
believe as long as there is unreacted Cu(NO3)2 there will also still be unconverted Malachite. Patience is a virtue...
Your reference throws up two more interesting species:
Georgeite: Cu2CO3(OH)2.6H2O, a hexahydrate of Malachite
Chalconatronite: Na2Cu(CO3)2.3H2O, a double salt of CuCO3 and Na2CO3 trihydrate, it seems... This composition is also mentioned in the Google
reference. It would have a significantly higher CO2 content: 31.1 w% (Malachite 19.9 w%).
[Edited on 18-12-2014 by blogfast25]
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