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vampirexevipex
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copper silicate?
Hello today i been surfing in the internet and came across a particular compound, Copper Silicate. I searched for its preparation and found little to
no information about it. So, is it possible to make copper silicate from copper and silicate? If it is, then how?
[Edited on 22-02-12 by vampirexevipex]
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weiming1998
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Quote: Originally posted by vampirexevipex  | Hello today i been surfing in the internet and came across a particular compound, Copper Silicate. I searched for its preparation and found little to
no information about it. So, is it possible to make copper silicate from copper and silicate? If it is, then how?
[Edited on 22-02-12 by vampirexevipex] |
1, What is silicate? Do you mean silicon dioxide?
2, Copper silicate cannot be made from copper and silicon dioxide because copper cannot react with non-oxidizing acids
3, The way to make copper silicate is to probably precipitate it (if possible) with a soluble copper salt, like CuCl2 and sodium silicate. If that
doesn't work, then the reaction of Cu(OH)2 with hydrated SiO2 probably will.
[Edited on 31-3-2012 by weiming1998]
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AJKOER
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I would try reacting Sodium Silicate, Na2SiO3, which is available per Wiki as an aqueous solution, with CuCl2:
Na2SiO3 (aq) + CuCl2 (s) --> 2 NaCl (aq) + CuSiO3 (s)
where I am assuming that CuSiO3 will have low solubility.
If you are able to work with molten salts, per Wiki:
"Sodium carbonate and silicon dioxide react when molten to form sodium silicate and carbon dioxide:[1]
Na2CO3 + SiO2 → Na2SiO3 + CO2"
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weiming1998
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A non-molten salt way of making sodium silicate is to react silica gel (found in food packaging, etc) with a concentrated solution of NaOH.
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vampirexevipex
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Thanks in advance! Copper acetate will work aswell right?
Cu(OAc)2 + NaSiO3 -> CuSiO3 + Na(OAc)2
[Edited on 22-02-12 by vampirexevipex]
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jamit
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@vampirexevipex
Can I ask why you want to make copper silicate? There's not much info on this chemical but what's its use in a lab or commercially?
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vampirexevipex
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| Quote: Originally posted by jamit | @vampirexevipex
Can I ask why you want to make copper silicate? There's not much info on this chemical but what's its use in a lab or commercially?
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That's for me to know, and you to find out... shhhhhhh...
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barley81
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Mix solutions of sodium silicate and copper sulfate. Both are cheap and readily available. Use dilute solutions because the solutions don't mix very
well if they're concentrated (a layer of copper silicate will form between the two solutions). The insolubility of copper silicate and other metal
silicates allows the chemical garden experiment to work.
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bbartlog
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It sounds none too stable to me. Should fall apart into CuO and SiO2 at the drop of a hat, assuming it exists at room temperature at all.
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blogfast25
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Whether or not a copper silicate will precipitate from a copper (II) solution and waterglass (Na2SiO3) will depend on the relative solubilities of
Cu(OH)2 and 'CuSiO3' (assuming the copper silicate is a simple one) because a Na2SiO3 solution is strongly alkaline. It's worth a try.
Alternatively you might want to try adding waterglass to a solution of cuprate. Cu(OH)2 is slightly amphoteric and dissolves in strong alkali to form
Cu(OH)<sub>4</sub><sup>2-</sup> (cuprate) anions (cobalt blue). If adding waterglass to a cuprate solution yields a
precipitate then that is likely to be 'a' silicate (but it could be a basic silicate).
[Edited on 31-3-2012 by blogfast25]
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Nicodem
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| Quote: Originally posted by AJKOER | I would try reacting Sodium Silicate, Na2SiO3, which is available per Wiki as an aqueous solution, with CuCl2:
Na2SiO3 (aq) + CuCl2 (s) --> 2 NaCl (aq) + CuSiO3 (s)
where I am assuming that CuSiO3 will have low solubility. |
And just what would prevent the expected product, Cu(OH)<sub>2</sub>(s), to precipitate instead? If anybody has references for anything
like this then post them please. Otherwise stop spreading misinformation.
Copper silicate (which one anyway?) is most likely prepared the way such compounds are prepared, by the solid-solid reaction between CuO and
SiO<sub>2</sub> (in the form of silicagel). It probably requires several millings and repeated calcinations before a reaction with an
acceptable conversion is achieved. I will not even bother looking for references, as I see that nobody even cares for actual data.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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blogfast25
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Nicodem:
A tad harsh, I feel.
I did look for some references and just Wiki mentions "CuSiO3·H2O (also reported as CuSiO2(OH)2)", strongly suggesting synthesis from watery
solution is possible. Barley81's reference to the 'chemical garden' is also relevant, as the formation of these colourful 'stalagmites' is believed to
be due to the formation of insoluble d-block metal silicates.
What would prevent the formation of cupric hydroxide instead of cupric silicate? If the solubility product of the silicate is much lower than that of
the hydroxide, the silicate will preferentially precipitate. It's a plausible hypothesis looking for evidence.
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barley81
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A long time ago, I mixed waterglass and copper sulfate solutions. A hard, crunchy precipitate formed. The texture of it was vastly different from
copper basic sulfate (made by mixing copper sulfate and sodium hydroxide). This is evidence that a different compound was formed, and likely contained
silicate ions.
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Nicodem
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The harshness is on place. I keep seeing more and more threads like this, starting from zero effort and being immediately derailed into idle
speculation based on zero references and zero thought. Always by the same usual suspects. I hate it when this occurs to a potentially interesting
topic.
Anyway, to keep on the topic... What barley81 describes above is probably the only thing one can expect from such a reaction. If you throw a crystal
of CuSO4.5H2O into a diluted solution of waterglass it starts growing blue gelatinous worm-like structures as the diffusion of ions progresses trough
them. I did this as a kid and it was quite entertaining. Other coloured similarly acidic salts do the same. I would not call that insoluble stuff
copper silicate though. It would be expected to be silicagel entraining copper(II) hydroxide if considering the reaction equation. Doubtlessly some
Cu-O-Si bonds might be there at the silicagel surface, but that is far from a compound. Just consider the isoelectronic carbonates. Na2CO3 in water is
less basic than Na2SiO3 yet as far as I know nobody ever succeeded to prepare CuCO3 by its reaction with CuSO4(aq). All you get is Cu(OH)2×CuCO3. I
don't even know how CuCO3 is prepared, if it is a known compound at all, but I'm quite sure it is not made by aqueous precipitation. Same goes for
other salts of acidic metal ions with anions of poor acids. Acids generally do not like to combine with acids to give salts in aqueous media (unless
coordination prevails). They require different, more forcing conditions.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Eddygp
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Although this looks more like a strange hypothetical reaction to form a possible compound, it is possible to look at if from another point of view.
It of course depends on which silicate you want to do ( "copper(I) silicate", "copper (II) silicate" ). As this is not the case, I believe, it would
be useful to look at the formation of other metal silicates, to have ideas.
However, I think the best way would be to put copper(II) nitrate or copper(II) chloride in silicic acid.
EDIT: Wouldn't it be copper silicide? It is far more documented.
[Edited on 31-2012-3 by Eddygp]
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Nicodem
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Barley81 brought to our attention the reaction of acidic colored metal salts with waterglass. I was unaware that it is actually a common demonstration
and has a name: chemical gardens reactions. Those who ever tried it, know that it is a nice visual demonstration with "colored things growing",
especially suitable for kids (it was impressive to me when I was a kid).
I checked a little bit of the literature on it. The products are not metal silicates, so this is not really directly related to this thread, but
nobody seems interested in copper silicates anyway, so I'll stay off topic. There is an educational and review article on the topic that is worth
reading (J. Colloid Interface Sci. 2002, 256, 351–359; freely available here). The mechanism of growth of these structures is quite interesting, relying on diffusion through semi-permeable membranes that the products
form (this strongly influences their complex microscale morphology). The composition of the precipitates depend on the reactants: "The
compositions of two silicate-garden precipitates have recently been studied in detail: those formed from aluminium nitrate [15,16], and from copper
nitrate [17]. The former precipitate is a material with a hierarchical structure on the nanoscale, consisting of silica nanotubes clustered together
over several orders, surrounded by aluminosilicate and aluminium hydroxide. The latter precipitate is more crystalline, being formed in part of
crystalline copper hydroxide nitrate, together with amorphous silica."
Read also:
http://www.rsc.org/Publishing/ChemScience/Volume/2007/01/che...
For pictures see http://chcscienceandmath.blogspot.com/2009/08/crystal-garden...
... a weird one from DOI:10.1209/0295-5075/89/44004
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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Zephyr
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I've found a reference to copper silicate in The Golden Book of Chemistry Experiments
"Making Silicates:
1. Dilute 5ml of water glass (Na2SO3) with 5ml of water.
2. dissolve small crystal of copper sulfate in water.
3. Add a few drops of the water glass to get a blue precipitate of copper silicate."
It's strange that there isn't any other references to copper silicate, but after reproducing this experiment I got a light blue precipitate a promised
the golden book of chemistry
http://openmaterials.org/cache/The%20Golden%20Book%20of%20Ch...
(pg 55, lower left)
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bbartlog
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Although it is not copper silicate but rather calcium copper silicate, the ancient pigment known as Egyptian Blue seems relevant to the original
question: http://en.wikipedia.org/wiki/Egyptian_blue
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blogfast25
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| Quote: Originally posted by Pinkhippo11 | 3. Add a few drops of the water glass to get a blue precipitate of copper silicate."
It's strange that there isn't any other references to copper silicate, but after reproducing this experiment I got a light blue precipitate a promised
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What this proves is that you get a blue precipitate in the conditions described. But copper hydroxide is blue as well. At a very minimum you'd have to
prove there is silica in your precipitate, as evidence the blue precipitate is a silicate of sorts.
Filter off the precipitate and wash it carefully. The following tests would be useful:
1. Heat it: if it goes brown/black it's likely to be Cu(OH)2, which dehydrates quickly by heat to CuO (black). If it goes blue it's likely
to be a silicate of copper
2. Carefully add weak acid to it: it should split into a blue solution (the copper salt of the acid used) and a gelatinous whitish hydrate of silica,
if it is a copper silicate of sorts. If it dissolves completely to a blue solution, it's likely to have been Cu(OH)2
The Golden Book of Chemistry is interesting but not really an authorative source on chemistry...
[Edited on 12-9-2013 by blogfast25]
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Zephyr
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bbartlog, in the wiki article, the procedure for making Egyptian Blue(calcium copper silicate) calls for silica sand,copper carbonate,and calcium
carbonate and temperatures of 800-1000oC!
Cu2CO3(OH)2 + 8 SiO2 + 2 CaCO3 → 2 CaCuSi4O10 + 3 CO2 +
H2O
When making copper silicate you simply mix sodium silicate and water glass
CuSO4+Na2O3Si -> CuO3Si+Na2SO4
this doesn't involve calcium and does not require heat initiation like when making the said "Egyptian Blue".
| Quote: Originally posted by blogfast25 | | What this proves is that you get a blue precipitate in the conditions described. But copper hydroxide is blue as well. At a very minimum you'd have to
prove there is silica in your precipitate, as evidence the blue precipitate is a silicate of sorts |
in answer
to your question blogfast25, the blue solid I described didn't decompose upon heating so it isn't copper carbonate or copper hydroxide.
Also in the "conditions described" what other blue precipitate could form?
Almost all copper compounds are blue/green so the color isn't a reliable point on which to base an argument.
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Nicodem
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| Quote: Originally posted by Pinkhippo11 | When making copper silicate you simply mix sodium silicate and water glass
CuSO4+Na2O3Si -> CuO3Si+Na2SO4
this doesn't involve calcium and does not require heat initiation like when making the said "Egyptian Blue". |
That equation makes no sense chemically. You can't just pretend that reactions in aqueous solutions don't involve water. You can't ignore pKa values
either. I suggest you to read the whole thread and the cited references. All this was already discussed up-thread. There are good reasons for such
products being synthesized by calcination based solid-solid reactions.
| Quote: | | Also in the "conditions described" what other blue precipitate could form? |
Firstly, copper silicate is the last thing one would expect. Secondly, plenty of other blue precipitates could form, like the materials described in
the articles cited above. You would need a powder XRD analysis to prove the presence of copper silicate in that precipitate. Just wishing or expecting
it to be what you want is not enough.
…there is a human touch of the cultist “believer” in every theorist that he must struggle against as being
unworthy of the scientist. Some of the greatest men of science have publicly repudiated a theory which earlier they hotly defended. In this lies their
scientific temper, not in the scientific defense of the theory. - Weston La Barre (Ghost Dance, 1972)
Read the The ScienceMadness Guidelines!
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blogfast25
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PH11:
Whether or not a copper silicate can exist is a different question from to whether such a product can be made from mixing a (watery) solution of
sodium silicate and a (watery) solution of a soluble copper salt.
Solutions of waterglass are quite strongly alkaline, so they contain a lot of hydroxide (OH<sup>-</sup> ions. With Cu<sup>2+</sup> ions these form a blue, insoluble, flocculant precipitate:
Cu<sup>2+</sup>(aq) + 2 OH<sup>-</sup> === > Cu(OH)<Sub>2</sub>(s) (very simply put)
The hydroxide ions come from reaction of the silicate with water. Since as there's plenty silicate there's in principle also enough hydroxide to cause
Cu(OH)<Sub>2</sub> to precipitate out.
You say you heated up your precipitate – what were the heating conditions? Did you at a very minimum drive off most of the water?
By all means also add a weak solution of acid to your precipitate and see what happens. In acid conditions a freshly prepared silicate should yield
hydrated silica.
You're quite a long way from proving what you obtained is a silicate of sorts (and which one).
[Edited on 13-9-2013 by blogfast25]
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Zephyr
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i apologize for not explaining my procedure more thoroughly.
here is my procedure:
1. 0.5 g of copper sulfate if dissolved in 5 ml of water.
2. 1 ml of sodium silicate is added to the copper sulfate solution, a thick blue precipitate is formed.
3. The precipitate is filtered and left to evaporate.
Upon heating at approximately 700oC, the blue solid expands and turns white/gray. water condenses on rim of test tube.
When 1.5 ml HCl is added, the blue solid becomes a bright green liquid. copper chloride maybe?
again sorry for the obscurity the first time, any help is appreciated!
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blogfast25
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| Quote: Originally posted by Pinkhippo11 |
Upon heating at approximately 700oC, the blue solid expands and turns white/gray. water condenses on rim of test tube.
When 1.5 ml HCl is added, the blue solid becomes a bright green liquid. copper chloride maybe?
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The second results strongly points to the precipitate being Cu(OH)2:
Cu(OH)2 + 2 HCl === > CuCl2 + 2 H2O. Solutions of CuCl2 are indeed green.
With a copper silicate, say hypothetically 'CuSiO3', the very weak silicic acid would become displaced by the strong HCl, very simply put:
CuSiO3 + 2 HCl === > CuCl2 + H2SiO3
The silicic acid should precipitate as a voluminous gel of SiO2.nH2O. You didn't observe that.
The second test result is more ambiguous. You claim to have heated at 700 C. But did you also heat to 700 C? In
other words, what temperature did the precipitate reach, approximately? Cu(OH)2 should definitely yield black CuO on dehydration. But it's possible
that your precipitate contained 'trapped' excess Na2SiO3. Then, on heating you might end up with something grayish.
I would suggest to repeat the test using equivalent amounts of CuSO4 and Na2SiO3, not "0.5 g and 1.5 ml" (apples and oranges!) So calculate how many
moles is 0.5 g of CuSO4 (presumably you use the pentahydrate? CuSO4.5H2O) and then work out how much Na2SiO3 that is equivalent to. Make solutions of
these and carefully mix them together.
Edit:
I’m probably barking up the wrong tree myself here. If, as I strongly suspect, mixing solutions of a copper salt with waterglass results in Cu(OH)2
to precipitate then silica MUST also precipitate at the same time, according to the following stoichiometry:
Cu<sup>2+</sup>(aq) + SiO<sub>3</sub><sup>2-</sup> (aq) + 2 H<sub>2</sub>O(l) === >
Cu(OH)<sub>2</sub>(s) + H2SiO3, the latter manifests itself as hydrated silica (SiO2.nH2O)
This is due silicic acid being an extremely weak acid (pKa1 = 9.84, pKa2 = 13.2, Wiki), even weaker than carbonic acid (*). Hydrolysis of the
SiO<sub>3</sub><sup>2-</sup> anion to HSiO<sub>3</sub><sup>-</sup> and subsequently to
H<sub>2</sub>SiO<sub>3</sub> with release of OH<sup>-</sup> ions causes both Cu(OH)2 and hydrated silica to
precipitate out in a 1:1 molar ratio.
So your precipitate does have the same molar ratio CuO:SiO2 as ‘CuSiO3’ but it isn’t actually CuSiO3 because it contains no actual
SiO<sub>3</sub><sup>2-</sup> anions. It’s possible that when carefully washed (sulphate!), dried and subjected to prolonged
heat and mechanical action such a mixture would fuse to something akin to ‘CuSiO3’ but only advanced measuring techniques like X-ray diffraction
crystallography could shed light on that structure. Silicates can be excruciatingly complicated in structure, as the myriad of different silicate
based minerals shows.
(*) in your 'Golden Book of Chemistry' is described an interesting little experiment that shows how silicic acid can be displaced from waterglass by
carbonic acid, proving in a simple way that the latter is a stronger acid than the former.
[Edited on 14-9-2013 by blogfast25]
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unionised
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This observation
"Upon heating at approximately 700oC, the blue solid expands and turns white/gray. water condenses on rim of test tube." proves that it's not copper
hydroxide which would dehydrate to the oxide which is black.
It's probably a complex copper silicate something like this
http://www.ncbi.nlm.nih.gov/pmc/articles/PMC2960335/
and the assertion that it's a mixture of silica gel and copper hydroxide is baseless.
A colloidal "solution" of silica gel is a commercial product used in wine making, so there's no problem with a lack of a silica precipitate.
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