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CHRIS25
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New Measurements
Firstly I have to apologize. The blue that I kept measuring was the Blue-Green; good news is that the green is indeed green, and the Real Blue I have
now added to the tests. So now some comprehensive data.
All weights of carbonate aimed at 6 g
Sulphuric 8 mL + 8 mL water (this is 6.5 times more than the stoichiometric requirements)
Photos demonstrate how I did the reactions and the second photo you can see the completed reaction After all measurements taken - naturally.
----------------------------------------------------------------BLUE-------------Blue-Green---------GREEN
Weight Beaker empty----------------------------------138.61-----------------133.81-----------138.9
Weight Beaker + CO3----------------------------------144.61-----------------139.87-----------144.98
Weight Bker + empty TestTube + CO3--------------159.63---------------155.03-----------160.06
Weight Bker + TestTube + Acid + CO3--------------186.7-----------------182.61-----------188.05
Weight Bker + empty TestTube After reaction-----183.6-------------------181.75----------187.68
------------------------------------------------CO2 loss -------3.1----------------------0.86------------0.37
OBSERVATIONS:
The blue produced a huge amount of fizzing so much so that I could not add the whole test tube in all at once like the other two. Also the blue
turned into this gel-like precipitate.
Adrian kindly sent me a PDF: A Renaissance of Color: Particle Separation and Preparation of Azurite for Use in Oil Painting by
Michael Price
"......Azurite is sky
blue below 30 μm, becoming paler as
the particle size decreases. It is dark blue
with a slightly greenish hue from 40 to
60 μm, similar to the hues of modern
cobalt blue....."
Just a tiny quote that confirms what you said earlier about particle size. He goes into detail describing how he controls the colour of the pigment
by controlling the partical size of this copper carbonate and even has electron microscope images detailing everything.
RE the copper nitrate: Does this answer your question? It is quite crystalline but looks slushy here, I forgot to sharpen the image in order to
replicate the actual nitrate.
‘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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Erm, is it just me, or do all the three samples look equal, and Turquoise ?
The nitrate looks Blue.
[Edited on 18-12-2014 by aga]
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CHRIS25
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Yep and no it's not you, Green turns to blue with sulphuric and blue turns to green in linseed, (also what that article said). And here is another
fascinating piece of data from http://www.galleries.com/malachite
".....Malachite is an impostor of its own. It frequently pseudomorphs the closely associated mineral azurite. A pseudomorph is a mineral specimen
where the original mineral has been chemically replaced by another mineral, but the outward appearance is still retained. The transformation is
fascinating and sometimes leaves a nearly perfect azurite crystal shape that is actually malachite. Often the transformation is incomplete and leaves
a blue/green mineral specimen unlike any other".
‘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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So the Carrier oil is the Key then ?
If i dunk my batch of Malachite (which is slowly going green) into Linseed oil, it should be a Green colour ?
Does that take Time or is it pretty quickly obvious ?
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blogfast25
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Chris:
First off. Like aga, I have difficulty distinguishing the colours of these products. Very similar to me. I expected larger differences.
Second. Your Cu(NO3)2 looks perfect. No problems at all. Very nice, indeedy.
Third, I’m convinced the good people of galleries.com have got the wrong end of the stick: it’s Azurite that can morph into Malachite, not the
other way around! For Malachite to ‘pseudomorph’ into Azurite 3 mol of Malachite would have to absorb at least 1 mol of CO2 (at STP, that’s 24
L!) at ATMOSPHERIC pressure. The CO2 pressure in the air however is still much lower than 1 atm because air only contains 0.039 % of CO2! With all due
respect but these people may be excellent mineralogists but not chemists.
The weight percentages now come out respectively as 51.7; 14.2 and 6.08 w% CO2. The first is way too high, the two others really a bit too low. Let me
think about this some more before I try and make sense of it. You’ve put too much work into this to shoot it down without due consideration.
Quote: Originally posted by aga  | So the Carrier oil is the Key then ?
If i dunk my batch of Malachite (which is slowly going green) into Linseed oil, it should be a Green colour ?
Does that take Time or is it pretty quickly obvious ? |
Yes, the carrier makes a lot of difference and that should become apparent immediately after mixing. Sunflower oil can be used for a test, if you
haven't any linseed oil.
And how come this *.pdf wasn't also sent to moi?
[Edited on 18-12-2014 by blogfast25]
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CHRIS25
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Ok Ok Guys, there seems to be some communication mis-wired, or you have colour management issues on your monitors, but I doubt the latter.
The solution in the jars is DURING the reaction and had changed colours to the point that they were the same colour except for the Gel like reaction
which was clearer and had lost its colour. I only showed these because dear old Gert advised me that I should not allow any spray to escape and use a
volumetric, and after removing the lids I was surprised to see how much spray would have been lost, especially from the far left.
The second photo shows the reactions AFTER completion, and the two on the right are ALMOST/VERY CLOSE to the same colour, the far right having changed
from GREEN to BLUE, but with a tiny tiny hint of green hue visible
These new photos show the three different carbonates that I used for the tests: THEY ARE IN EXACTLY the same order as all the above images. IE: Green
far right, green-blue middle, blue far left.
[Edited on 19-12-2014 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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That's much better, Chris, thank you.
Tomorrow I'm wrapping up my Azurite experiment although there is still some blue copper nitrate left. It's gone on for long enough now.
Rummaging through the recesses of my dark mind yesterday, I had an idea.
The overall reaction equation for the Azurite experiment was:
3 Cu(NO3)2 + 3 CaCO3 + H2O === > Cu3(CO3)2(OH)2 + 3 Ca(NO3)2 + CO2
What if we were to replace all nitrate by sulphate and all calcium by sodium?
The reaction equation would then be:
3 CuSO4 + 3 Na2CO3 + H2O === > Cu3(CO3)2(OH)2 + 3 Na2SO4 + CO2
The advantages of using these reagents are clear:
1. CuSO4 is cheaper than Cu(NO3)2. With calcium, Cu sulphate could not be used because CaSO4 is insoluble.
2. The source of carbonate ions/CO2 is now water soluble, instead of CaCO3, which is not.
I think the insolubility of limestone is what makes this reaction very slow (at least at these low temperatures).
I expect the (modified) reaction to proceed similarly, with Malachite being formed first, then the Malachite converts to Azurite because of the high
CO2 pressure, but faster.
Replacing the ingredients mol for mol should lead to the same pressure build up.
So tomorrow I will load solid CuSO4.5H2O and a saturated solution of Na2CO3 in the correct ratio into the PET bottle and hopefully Azurite will also
form but faster this time.
[Edited on 19-12-2014 by blogfast25]
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CHRIS25
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Reference the brain-wave above - Did you not advise against using a powder?
Not that beforehand I know what difference this makes, but re-reading Bauer I was struck by the fact that he mentions Chalk. Now I did some searching
and discovered that Chalk is in fact a product of biological secretion type calcium carbonate, whereas Limstone (generally speaking there are
exceptions in Fossilecerous Carbonate), anyway limestone from a quarry is normally known as Chemical calcium carbonate, this is over-simplified, but
on further reading I got the impression that the two are more different than I first thought. As I said probably nothing, but at least this is new to
me.
As for your suggestion above, since I have just made a huge amount of Copper nitrate, I will be getting a second and a third bottle now, one for
Seashells, one for limestone, and one to follow what you are recommending above.
The PDF list on the rock compositions gave the following:
Azurite: 25% Carbonate, 69% copper oxide and Water 5%
Malachite: 20% carbon dioxide, 72% Copper oxide and water 8 %
Why would they list the carbonate composition for azurite yet replace that with the carbon dioxide composition for malachite? According to the same
source Azurite metamorphs to malachite at the loss of Hydroxyl groups, I don't see how this is so when one looks at the formulas for both, especially
since it appears that it is the composition of carbon dioxide that has the strongest influence on its character?
[Edited on 19-12-2014 by CHRIS25]
[Edited on 19-12-2014 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:
I advised against powder in the case of limestone (CaCO3) because I was using an excess (with respect to stoichiometry) of CaCO3. Had I used powdered
CaCO3, the unreacted CaCO3 would have ended up with the Azurite, impossible to separate the two.
But Na2CO3 is highly water soluble, so any excess will be washed out of the Azurite when I clean it up.
Using CuSO4 and Na2CO3 I expect the Malachite to form very quickly, then it will convert to Azurite at unknown rate when CO2 pressure is achieved.
Wait and see, I guess…
Re. limestone/seashells etc, what is important in the preparation re. Brauer is that one uses CaCO3, not where that CaCO3 comes from.
Ultrapure synthetic CaCO3 would work the same as more natural forms like the ones you listed.
The theoretical amount of CO2 in pure, anhydrous Azurite, Cu3(CO3)2(OH)2, is as follows: MM of Azurite is 3 x 63.5 + 2 x 12 + 8 x 16 + 2 =
344.5 g/mol. CO2 content of 1 mol Azurite is 2 x 44 g/mol = 88 g/mol. W% CO2 = 88 / 344.5 x 100 = 25.5 w%.
Not sure why they revert to ‘carbonate’ either.
The pseudomorphing reaction of Azurite to Malachite is the following reaction in reverse (left is Malachite, right is Azurite)
3 Cu2CO3(OH)2(s) + CO2(g) < === > 2 Cu3(CO3)2(OH)2(s) + H2O(l)
After that absorption of H2O/loss of CO2 the 'new' molecule then rearranges itself to a new structure (that of Malachite, that is where these stories
of Azurite mysteriously turning into Malachite come from).
I can’t put it more objectively than that...
[Edited on 19-12-2014 by blogfast25]
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blogfast25
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Well, the Azurite experiment was an epic failure.
I opened the bottle and it fizzed like mad, including the slurry: lots of CO2, so far, so good and as expected.
I sieved off the chunks of limestone, washed and dried and weighed them but there was hardly any weight loss at all: not good.
Then the precipitate was Buchnered off which appeared blue but lost all colour on washing: the blue had simply been caused by
unreacted copper nitrate in the supernatant. I washed this filter cake with two portions of acetone and dried it at 100 C for 1 h. I got about 8 g of
this white powder.
I performed the CO2 determination as above and… found no fizz whatsoever, not even a bubble!
My working hypothesis is that it is calcium sulphate, due to residual sulphate in my copper nitrate. I may test this hypothesis. With so much CO2
around, calcium would otherwise stay in solution as Ca(HCO3)2.
So that was a damp squib, sadly.
In the next experiment, 75 g of CuSO4.5H2O powder (0.3 mol) and 32 g of Na2CO3 powder (anh.) (0.3 mol) were loaded into a 600 ml colourless and clean
PET bottle and dry-mixed by shaking. 100 ml of water was added and the bottle quickly capped and then shaken. Green Malachite and CO2 (the bottle
stiffened up considerably) were formed immediately:
2 CuSO4 + 2 Na2CO3 + H2O === > Cu2CO3(OH)2 + 2 Na2SO4 + CO2
I now live in hope that the captured CO2 and resulting pressure will convert the Malachite to Azurite, over time. At least Malachite did certainly
form this time...
[Edited on 20-12-2014 by blogfast25]
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CHRIS25
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| Quote: Originally posted by blogfast25 | Well, the Azurite experiment was an epic failure.
My working hypothesis is that it is calcium sulphate, due to residual sulphate in my copper nitrate. I may test this hypothesis. With so much CO2
around, calcium would otherwise stay in solution as Ca(HCO3)2.
[Edited on 20-12-2014 by blogfast25] |
How did you make your copper nitrate then? you must have used copper
sulphate to make the nitrate? I am just boiling down some copper nitrate at this moment, used copper and nitric acid. So I will still go ahead and
repeat your attempt but will think about what other parameters might be changed, if any. Not that I can improve on this, except that I won't get any
sulphate.
[Edited on 20-12-2014 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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| Quote: Originally posted by CHRIS25 | | Quote: Originally posted by blogfast25 | Well, the Azurite experiment was an epic failure.
My working hypothesis is that it is calcium sulphate, due to residual sulphate in my copper nitrate. I may test this hypothesis. With so much CO2
around, calcium would otherwise stay in solution as Ca(HCO3)2.
[Edited on 20-12-2014 by blogfast25] |
How did you make your copper nitrate then? you must have used copper
sulphate to make the nitrate? I am just boiling down some copper nitrate at this moment, used copper and nitric acid. So I will still go ahead and
repeat your attempt but will think about what other parameters might be changed, if any. Not that I can improve on this, except that I won't get any
sulphate.
[Edited on 20-12-2014 by CHRIS25] |
Yes, I started from CuSO4, precipitated it as Cu(OH)2, filtered and washed (but obviously not enough!), then dissolved it in nitric acid and boiled
down to a known final volume.
The identity of the mystery non-fizzing white precipitate as CaSO4 was just confirmed as follows. The material was treated with an excess of saturated
Na2CO3 solution at about 70 C for an hour with magnetic stirring. This would cause the CaSO4 to convert to the much less soluble CaCO3:
CaSO4(s) + Na2CO3(aq) === > CaCO3(s) + Na2SO4(aq)
The slurry was then filtered and the filter cake washed with copious amounts of hot DIW, then a smidge of acetone. It was dried on filer at 100 C for
an hour.
Treated with 50 v% H2SO4 this dry filter cake fizzed like mad, with white CaSO4 precipitating:
CaCO3(s) + H2SO4(aq) === > CaSO4(s) + CO2(g) + H2O(l)
So that proves it's mainly CaSO4.
I'm not convinced the sulphate in the copper nitrate was the cause of the failure of this first Azurite experiment, but can't rule it out either. I
have much more faith in the newest experiment.
[Edited on 20-12-2014 by blogfast25]
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CHRIS25
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Just found this: http://www.sciencemadness.org/talk/viewthread.php?tid=3623#p...
[Edited on 20-12-2014 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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Interesting that others have been working on Azurite here on SM.
But there's little there we don't already know.
Interesting tidbit about the copper phosphate, presumably Cu3(PO4)2 or possibly a basic phosphate.
The thread confirms again that there is considerable confusion with regards as to what converts to what but it is now firm and clear
in my mind that Malachite is the stable version and that by water and high pressure CO2 it can be converted into metastable Azurite. The latter then
slowly or more rapidly converts back to Malachite in the presence of water and other conditions being 'right'.
[Edited on 21-12-2014 by blogfast25]
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CHRIS25
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Yes I agree, and if these people can make it, http://www.kremer-pigmente.com/en/search.html?keywords=azuri... we can. I also homed in on the copper phosphate.
But I have this as well: Add copper sulphate to a Concentrated solution of sodium carbonate at 45 - 64c for an azurite, and copper sulphate to the
bicarbonate at the same temp for a green. I will try this tomorrow or the next and post results, however the former will turn to malachite within 2
hours apparently. We'll see. In fact have just gathered a number of recipes, it's going to be a busy week I think. will post images and results as
they are completed.
‘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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Blimey! At those prices we should get cracking, presto! 
It's unlikely that Kremer actually produce anything themselves though, I'm fairly sure they are traders only, not producers. Going by their website
they may do some pigment mixing but I think that's about it.
I'm running a test with an excess saturated Na2CO3 solution, about 50 C, CuSO4 solution stirred in with high speed mixing. See what gives later on...
Update:
So 106 g anh. Na2CO3 (1 mol) was mixed with 265 g of water and magstirred and heated to about 50 C until all carbonate had dissolved. Similarly 25 g
of CuSO4.5H2O (0.1 mol) was dissolved in about 200 g of water, to about 30 C.
The sodium carbonate solution stirring speed was then increased to maximum and the copper sulphate solution added to it slowly. The colour changed to
a deep blue, so for about 5 ms I thought ‘Bingo!’ But it wasn’t to be: on filtering the filtrate ran a deep blue and it’s caused by cuprate
anions: Cu(OH)<sub>4</sub><sup>-</sup>(aq). I’ve seen this anion form many times and it’s caused by the strong alkalinity
of the saturated sodium carbonate solution. The deeply intense blue of cuprate makes estimating its concentration difficult.
But there was much precipitate too, which Buchnered reasonably well, was washed a few times with DIW and two minimal rinses of acetone. This product
looks far more green than blue to me and is now drying at 100 C for 1 h. I will determine CO2 content later on.
Update 2:
Ok, this is another failure: on drying this product went to a dark green, then developed black patches. These are due to Cu(OH)2 dehydrating to black
CuO. Here’s a photo comparing it to a standard light blue circle printed with my inkjet:
This is crappy Malachite, in short. Not worth determining CO2 content on.
And it further confirms my opinion that Azurite cannot be prepared by atmospheric pressure precipitation from a cupric solution and a soluble
carbonate/bicarbonate.
Here's also 'the real deal' (from Russia):
http://www.alibaba.com/product-detail/Azurite-pigment_106375...
[Edited on 22-12-2014 by blogfast25]
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aga
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The stuff i made is closer to the Russian True Blue, yet not exactly the same colour.
Copper Sulphate + Sodium Sulphate.
I've been waiting over a week for it to go Green, and it hasn't.
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blogfast25
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Do use emoticons to underline your jokes! 
Seriously though, determine CO2 content as I showed above, to establish identity of the material.
[Edited on 23-12-2014 by blogfast25]
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blogfast25
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Chris:
What you should do is run one of your tests in such a way that you can measure what I wrote above:
Quote-
Malachite:
2 Cu<sup>2+</sup>(aq) + 2 CO<sub>3</sub><sup>2-</sup>(aq) + H<sub>2</sub>O(l) === >
Cu<sub>2</sub>CO<sub>3</sub>(OH)<sub>2</sub>(s) + CO<sub>2</sub>(g)
So for every 2 mol of carbonate 1 mol is shed.
Azurite:
3 Cu<sup>2+</sup>(aq) + 3 CO<sub>3</sub><sup>2-</sup>(aq) + 2 H<sub>2</sub>O(l) === >
Cu<sub>3</sub>(CO<sub>3</sub><sub>2</sub>(OH)<sub>2</sub>(s) + CO<sub>2</sub>(g)
So for every 3 mol of carbonate 1 mol of CO2 is shed. (Of course Azurite cannot be prepared that way).
Unquote-
By weighing everything carefully and measuring the weight loss after reaction, the molar ratio of carbonate used/CO2 lost can be established.
Mass balances don't lie: if the molar ratio was 2 (or close), what you precipitated was Malachite, it simply cannot be otherwise stoichiometrically
speaking.
In any case, if that paper on M/A stability shows us one thing it's that in ordinary precipitation conditions pH will ALWAYS be (way) too high for
Azurite to form.
Reading that paper reinforces my belief that Debray had the right idea and that it's me who is doing it wrong.
[Edited on 24-12-2014 by blogfast25]
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DJF90
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| Quote: Originally posted by blogfast25 |
So 106 g anh. Na2CO3 (1 mol) was mixed with 265 g of water and magstirred and heated to about 50 C until all carbonate had dissolved. Similarly 25 g
of CuSO4.5H2O (0.1 mol) was dissolved in about 200 g of water, to about 30 C.
The sodium carbonate solution stirring speed was then increased to maximum and the copper sulphate solution added to it slowly. The colour changed to
a deep blue, so for about 5 ms I thought ‘Bingo!’ But it wasn’t to be: on filtering the filtrate ran a deep blue and it’s caused by cuprate
anions: Cu(OH)<sub>4</sub><sup>-</sup>(aq). I’ve seen this anion form many times and it’s caused by the strong alkalinity
of the saturated sodium carbonate solution. The deeply intense blue of cuprate makes estimating its concentration difficult.
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Change the order of addition...
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CHRIS25
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It would appear from further reading that Pressure does not play such an important role in the formation of Azurite - reading about the Delphi bronze
statue confirms this (contrary to one of Brauer's reported methods, and we do not know what other variables were present in that situation). But also
I found the following PDF on the stability of malachite and azurite, it seems also that precipitating azurite from solution requires a slightly acidic
environment PH 6.5 yet the malachite can also precipitate at this PH but will definitely precipitate above this level. Furthermore the PDF
demonstrates that it is carbonate/bicarbonate levels that are the key factor in bringing around azurite and not the CO2, CO2 certainly plays a role
indeed, but it is not the main role as is demonstrated by the Delphi bronze statue where it was not until neighbouring stonemasons work with limestone
began that the statue was covered in a thin film of calcite and a blue on the statue appeared, in the presence of CO2 from the grounds beneath. The
CO2 alone did not cause the blue otherwise it would have remained that colour down through the years. Rather the calcite dust increased the pressence
of the CO2 and influenced PH favourably.
These are just some very sketchy conclusions from a brief read of the two sources.
I will get round to further experiments after I have digested the information in more detail.
[Edited on 24-12-2014 by CHRIS25]
Attachment: Azurite Malachite CO2 effects.pdf (366kB)
This file has been downloaded 509 times
Attachment: Azurite Analysis Delphi.pdf (677kB)
This file has been downloaded 442 times
[Edited on 24-12-2014 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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Nonsense.
| Quote: Originally posted by CHRIS25 | It would appear from further reading that Pressure does not play such an important role in the formation of Azurite - reading about the Delphi bronze
statue confirms this (contrary to one of Brauer's reported methods, and we do not know what other variables were present in that situation). But also
I found the following PDF on the stability of malachite and azurite, it seems also that precipitating azurite from solution requires a slightly acidic
environment PH 6.5 yet the malachite can also precipitate at this PH but will definitely precipitate above this level. Furthermore the PDF
demonstrates that it is carbonate/bicarbonate levels that are the key factor in bringing around azurite and not the CO2, CO2 certainly plays a role
indeed, but it is not the main role as is demonstrated by the Delphi bronze statue where it was not until neighbouring stonemasons work with limestone
began that the statue was covered in a thin film of calcite and a blue on the statue appeared, in the presence of CO2 from the grounds beneath. The
CO2 alone did not cause the blue otherwise it would have remained that colour down through the years. Rather the calcite dust increased the pressence
of the CO2 and influenced PH favourably.
These are just some very sketchy conclusions from a brief read of the two sources.
I will get round to further experiments after I have digested the information in more detail.
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I'm studying the B.W. Vink one, great find BTW!!! In that pH < 7 lies the rub of course, as it is basically impossible to create carbonate rich
conditions at that pH because of:
CO32- + 2 H+ === > CO2 + H2O
Hence Debray's reasoning to increase carbonate concentration by high pressure CO2. Debray experiment is certainly on the correct side of pH = 7, i.e.
slightly lower.
Chris, while it may well be true that Azurite may be formed at lower pressure, Le Chatelier's Principle still holds for:
3 Cu2CO3(OH)2 + CO2 < === > 2 Cu3(CO3)2(OH)2 + H2O
... because the 'consumption' of CO2 reduces the overall pressure of the system and that's how equilibria operate.
Re. Delphi: does the Delphi paper PROVE Azurite was formed? I've yet to read it.
Edit: Plutarch, wow, that's 1 century AD! It's like a testimony on the colour of Jesus' sandals!!! In short: unverifiable...
[Edited on 24-12-2014 by blogfast25]
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CHRIS25
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I read "quickly' and have not yet gone through this slowly and digested, but I certainly get the sense that a big part of the statue colour turned to
azurite, and that a blue patina may have been applied then lost again. Plutarch writing around 100 AD roughly comments on the statue's beautiful
blue, and this was 400 years After it was made. The various analysis of this statue conclude (roughly, briefly) that Plutarch's observations were a
clear sign that an azurite patina had formed as a direct result of building and restoration work during his time close by the statue, the position of
the statue also giving it excellent opportunity to turn blue, something to do with CO2 vents from underneath in the limestone bedrock and the calcium
carbonate dust that would have settled on the statue during the nearby works. But this is just my first impression of a quick read Gert.
What does B.W. Vink one mean?
Quote - In short: unverifiable...? The paper verifies his observations quite ingeniously.
[Edited on 24-12-2014 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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The first pdf you linked to. I've only just begun reading it. There's more information it than anything else I've come across so far on
Azurite/Malachite, so it's a great find, ta. Need to take time to digest it properly.
The Delphi paper relies heavily on the M = green and A = blue dichotomy and we all know how subjective the colour of Malachite really is. The latest
pure sample I produced yesterday, while wet could pass for green OR blue, easily. People would fight over that colour, trust me.
[Edited on 24-12-2014 by blogfast25]
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CHRIS25
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Well, here is some last quick minute data from the 4 tests that I did, now dried.
(I like my own nomenclature)
AZ 1:
(0.05 mol Cu sulphate +50 ml water) + (0.02 mol Na carbonate + 50 ml water) yielded a clear blue, subjectively, much bluer than the three below (but
not azurite of course)
AZ 2:
(0.05 mol Cu sulphate +50 ml water) + (0.05 mol Na carbonate + 50 ml water) yielded a clear blue-green
AZ 3:
(0.05 mol Cu sulphate +70 ml CARBONATED water) + (0.02 mol Na carbonate + 100 ml water) yielded a clear blue-green BUT more green than AZ 2 (Also,
there are green patches developing in this one the same colour as AZ 4. This was washed by the way in carbonated water several times)
AZ 4:
(0.06 mol Cu sulphate +50 ml water) + (0.02 mol Na carbonate + NO water) yielded a clear Green
‘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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