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blogfast25
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Repeat:
What is "copper ammonium hydroxide"? Formula, how to prepare it and what evidence for its existence, please.
Quote: Originally posted by AJKOER  | Perhaps part of the answer is explained by this study of the thermal decomposition stages and intermediate compounds: "Thermal decomposition of the
basic copper carbonates malachite and azurite", by I.W.M. Brown, K.J.D. Mackenzie, G.J. Gainsford...
Still, interestingly, at one stage a mixture containing CuO is referenced.
[Edited on 28-1-2015 by AJKOER] |
What 'part of the answer is explained'?
If you calcine malachite (or azurite) at some point you're going to hit CuO, like night follows day.
The other sources you mention are so low level it's unreal. They still crap on about 'mixtures'. Compounds with composition like xCuCO3.yCu(OH)2 (x, y
are positive integers) are compounds, probably double salts, NOT mixtures.
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AJKOER
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Currently more popular name (but I have issues with its accuracy, discussed below, so I avoid it) for the hydroxide associated with the copper
ammonium complex, for example, is presented in Wikipedia http://en.m.wikipedia.org/wiki/Schweizer%27s_reagent as follows, to quote:
"Schweizer's reagent is the chemical complex tetraamminediaquacopper dihydroxide, [Cu(NH3)4(H2O)2](OH)2. It is prepared by precipitating copper(II)
hydroxide from an aqueous solution of copper sulfate using sodium hydroxide or ammonia, then dissolving the precipitate in a solution of ammonia."
My problem is that apparently there is nothing especially special about the tetraamminediaquacopper (II) cation, [Cu(NH3)4(H2O)2]2+, as one can
actually create (and I do per my galvanic formation of the complex from elemental copper, dilute ammonia and H2O2) in solution any of
[Cu(NH3)4(H2O)2]2+, [Cu(NH3)3(H2O)3]2+, [Cu(NH3)2(H2O)4]2+, or [Cu(NH3)(H2O)5]2+. My search for my prior thread with references, produced the
following in the Energetic Materials section of SM:
| Quote: Originally posted by AJKOER | I noticed recently that dissolving Cu in aqueous ammonia in the presence of H2O2 and NaCl appears to form the insoluble Copper Ammonium chloride,
[Cu(NH3)4(H2O)2]Cl2....
...see "Kinetics and Mechanism of Copper Dissolution In Aqueous Ammonia" available online) .....
Note, as a point of interest, there is actually nothing sacred about the tetraamminediaquacopper cation as detpending on the ammonia concentration in
solution, one could have anywhere from [Cu(NH3)(H2O)5]2+ (the greenish-blue thin layer) to [Cu(NH3)5(H2O)]2+ (a royal blue complex), with the latter
occurring in very concentrated ammonia solutions. Reference: https://docs.google.com/viewer?a=v&q=cache:IjHK0vuBZhcJ:...
.. |
Also, some source state that [Cu(NH3)4(H2O)2](OH)2 is formed only with strong ammonia. This statement is also misleading, in my opinion, as I have at
times seem layers of layers of color in my galvanic cell of dilute ammonia, including royal blue around the copper at the base of the cell. This
anodic zone (the copper source may be several unconnected pieces) is where the oxidation of copper proceeds according to:
Cu + 4 NH3 + 2 H2O --) [Cu(NH3)4(H2O)2]2+ + 2 e-
Reference: "Kinetics and Mechanism of Copper Dissolution In Aqueous Ammonia", at https://www.google.com/url?sa=t&source=web&rct=j&...
So, bottom line, the more technical name possibly implying to some, that it is "the" copper ammine complex is misleading, especially, in my case, if I
am recommending an electrochemical approach to the complex employing dilute ammonia. Now, the older naming convention (which I employ) is not without
issues as it can create confusion when a double salt of ammonia is also possible, but this is not the case for the hydroxide.
-------------
To answer your other comment, I repeat a direct quote, provide above with link, from an obvious authority, in my opinion, on minerals where the words
"and varying portions" is actually applied to natural occurring basic copper carbonate crystals, that are apparently quite beautiful:
"A pseudomorph of malachite after azurite retains the same shape as the original azurite crystal but is composed of malachite rather than azurite. The
pseudomorph is therefore malachite green in color rather than azurite blue.
The chemical formula describing the inversion of azurite to malachite is:
2 [Cu(OH)2 • 2(CuCO3)] + H2O ----------> 3 [Cu(OH)2 • (CuCO3)] + CO2
2 azurite + water ------------------> 3 malachite + carbon dioxide
Mineral specimens containing only azurite, only malachite, and varying portions of each substance exist. The contrast between azurite's intense blue
and malachite's bright green is very pleasing to the eye. Samples in which the transformation process has begun but remains incomplete can therefore
be quite beautiful."
[Edited on 28-1-2015 by AJKOER]
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blogfast25
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| Quote: Originally posted by AJKOER |
To answer your other comment, I repeat a direct quote, provide above with link, from an obvious authority, in my opinion, on minerals where the words
"and varying portions" is actually applied to natural occurring basic copper carbonate crystals, that are apparently quite beautiful:
"A pseudomorph of malachite after azurite retains the same shape as the original azurite crystal but is composed of malachite rather than azurite. The
pseudomorph is therefore malachite green in color rather than azurite blue.
The chemical formula describing the inversion of azurite to malachite is:
2 [Cu(OH)2 • 2(CuCO3)] + H2O ----------> 3 [Cu(OH)2 • (CuCO3)] + CO2
2 azurite + water ------------------> 3 malachite + carbon dioxide
Mineral specimens containing only azurite, only malachite, and varying portions of each substance exist. The contrast between azurite's intense blue
and malachite's bright green is very pleasing to the eye. Samples in which the transformation process has begun but remains incomplete can therefore
be quite beautiful."
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All of this is well known and discussed ad nauseam in the relevant copper basic hydroxide thread in 'beginners':
http://www.sciencemadness.org/talk/viewthread.php?tid=50822&...
Any significant contributions are best parked there.
Wonderful photos of malachite/azurite combinations here:
http://www.bing.com/images/search?q=azurite+malachite&FO...
How does the copper tetrammine complex relate to all this? What diabolical plan do you have in mind? 
[Edited on 28-1-2015 by blogfast25]
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AJKOER
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Actually, I am a few years too late, as what I am suggesting has been recently patented. To quote from the patent, "Direct synthesis of copper
carbonate", US 7411080 B2, Link: http://www.google.com/patents/US7411080 :
"...What is needed is a method of directly forming a variety of basic copper salts from copper metal.
SUMMARY OF THE INVENTION
In a broad aspect the invention encompasses a novel method of synthesizing selected basic copper salts including basic copper carbonate, basic copper
sulfate, and basic copper acetate directly from copper metal using water, an amine (preferably ammonia), an oxidizing source (preferably oxygen), and
a source of anions. Advantageously the reaction takes place in a single reactor. Advantageously the oxidant is a gas comprising oxygen, such as
oxygen, an oxygen/inert gas mixture such as oxygen and nitrogen, air, or any combination thereof. .."
although, I can up with the idea to aid home chemists in their quest for copper salts and such.
[Edited on 28-1-2015 by AJKOER]
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blogfast25
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From that patent:
| Quote: | EXAMPLE 1
A 500-ml beaker with magnetic stir bar was charged with about 300 ml water and 3 g of ammonia (0.176 moles of NH4OH, added in the form of 10 grams of
concentrated aqueous ammonium hydroxide). CO2 gas was bubbled into the solution with agitation until a pH of 8.5 was obtained. The solution was heated
on a hot plate and maintained at temperature of about 50° C. Approximately 20 g (0.315 moles) of copper powder (˜325 mesh) was added to the beaker
under good agitation. The molar ratio of copper to ammonia was 1.8, and the copper loading was 66.6 grams per liter of water. Air was introduced at
the same time. During the course of the reaction the pH increased gradually, so CO2 gas was occasionally introduced to maintaining a pH of around 8.5.
After about 10 hrs no metallic copper was visible, and a slurry of green BCC precipitate was obtained, which held a stable pH of 8.50 without need for
further CO2 addition. No metallic copper was observed. The reaction mixture was filtered to yield a green solid cake and a near colorless filtrate.
The cake, after drying in a 50° C. oven overnight, was found to contain 56.2% copper. The theoretical copper content of basic copper carbonate is
57.48% but commonly 56.0% is as high as conventionally practical to manufacture. The weight mean particle size (“WMPS”, the diameter at which half
of the weight of material is present as particles having an effective diameter which is less than the weight mean particle size) of the basic copper
carbonate precipitate was 15.2 microns and the packed bulk density was 0.70 lbs/ft3. The particle size was determined using a MicroTrac™ S3500/S3000
laser scattering device. The packed bulk density “PABD” was determined using a JEL Stampfvolumeter™ STAV 2003. |
I'm more than willing to believe that. Ammonia acts as a catalyst here because it speeds up the oxidation/solubilisation of Cu(0) to Cu(II).
It's rather funny though how much effort they put into a physical characterisation of their product and how little into a chemical
characterisation! At a very minimum a CO2 and O content determination should be called for.
And of course like all patents it's riddled with *rse covering nonsense by keeping x and y deliberately vague and wide.
Copper metal is also less economical than using copper salts and Azurite this method will not make.
[Edited on 28-1-2015 by blogfast25]
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zed
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Skinflint that I am, I recently used this reaction to treat some wood. The treated wood at Home Depot is just too damned expensive.
I Just rolled some concentrated Copper Sulfate Solution onto some boards with a paint roller, and let 'em soak it in for a bit. The boards showed
little apparent color change.
Then, I dumped a box of Bicarbonate into a bucket of water, dissolved it well, and rolled the boards again. The boards took on a few green
highlights, but no big deal. Thereafter, I set them out, for a few days to let them dry a bit.
Coated them with a deck sealer, let 'em dry again for a few days, and observed they were continuing to "Green".
By the time, I put a final coat of paint on them, they were looking very green indeed. In the grain of the wood, it was taking a little while for
the copper ions and carbonate ions to co-operate into their insoluble magic.
So, there it is....my new front porch. Even done to code, which requires that such exposed woodwork be constructed of rot resistant, or treated wood,
but does not stipulate method of treatment.
I suppose, I'll know how well the treatment actually worked, in twenty-five years or so. If the porch is still present, it was a success. If not,
well...there is a decent chance I will be too dead to care.
[Edited on 1-2-2015 by zed]
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