CHRIS25
National Hazard
Posts: 951
Registered: 6-4-2012
Location: Ireland
Member Is Offline
Mood: No Mood
|
|
Cu Acetate and carbonate and sodium hydoxide
Hallo,
Cu(CH3OO2)H2O + NaOH + CaCO3 + H20 = ?
This mixture is too complex for me to know how to put the correct results on the other side of the equals sign - otherwise I can not balance it
correctly. I just need to know the results I will do the rest myself since that concept of "spoonfeed" is anethema on this forum (I understand) but I
really can not go to chemistry school you know -
Anyway this is a substitute for a Japanese formula for a rather unique patina, (the precipitate falls to the bottom and the top liquid is siphoned and
boiled with Cu Sulphate) it works quite well despite my very acidic copper acetate. I have used this a few times but never once thought to work out
what the chemistry here is. So rather than remain ignorant please could someone give me the results so that I may balance and see if the present
quantities that I use differ from the precise stoichemetry of the reaction. thankyou
‘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)
|
|
|
weiming1998
National Hazard
Posts: 616
Registered: 13-1-2012
Location: Western Australia
Member Is Offline
Mood: Amphoteric
|
|
Quote: Originally posted by CHRIS25  | Hallo,
Cu(CH3OO2)H2O + NaOH + CaCO3 + H20 = ?
This mixture is too complex for me to know how to put the correct results on the other side of the equals sign - otherwise I can not balance it
correctly. I just need to know the results I will do the rest myself since that concept of "spoonfeed" is anethema on this forum (I understand) but I
really can not go to chemistry school you know -
Anyway this is a substitute for a Japanese formula for a rather unique patina, (the precipitate falls to the bottom and the top liquid is siphoned and
boiled with Cu Sulphate) it works quite well despite my very acidic copper acetate. I have used this a few times but never once thought to work out
what the chemistry here is. So rather than remain ignorant please could someone give me the results so that I may balance and see if the present
quantities that I use differ from the precise stoichemetry of the reaction. thankyou |
A mix of Cu (II) acetate, NaOH and CaCO3 in water forms mainly Cu(OH)2, because CaCO3 is extremely insoluble, and Na acetate. Pure, fluffy Cu(OH)2
dehydrates slowly to CuO and H2O, but some of it might also react with the CO2 in the air+ the tiny amounts of CO3(2-) from the CaCO3, to form basic
copper carbonate, which is what makes up the so called "copper carbonate" because of the Lewis acidity of the Cu2+ ion, but that is irrelevant to your
original question.
So, to sum up my explanation, whether the mix was freshly made affect its composition a lot, but a very freshly made mix contains Cu(OH)2, NaCH3COO,
and CaCO3, as well as any unreacted NaOH/Cu acetate.
General equation: Cu(CH3COO)2+2NaOH+CaCO3--->Cu(OH)2+2NaCH3COO+CaCO3(it doesn't react).
Over time in air, a variety of compounds, from CuO to various Cu sulfides to a complex of copper acetates and carbonates (verdigris) are formed.
[Edited on 19-7-2012 by weiming1998]
|
|
|
CHRIS25
National Hazard
Posts: 951
Registered: 6-4-2012
Location: Ireland
Member Is Offline
Mood: No Mood
|
|
Hi welming, great thankyou. I have to leave it for a week, what happens then is that I get an almost clear liquid suspension above a dirty light
brown precipitate. This precipitate must be quite complex because experimenting without the liquid or too little has no effect on a copper piece
dipped in hot solution, but 3 mLs in 100 Mls of water mixed with 1 gram of copper sulphate produces a beautiful straw yellow patina.
(CaCO3 does not react)? Mmm I can see that now, but it must have some minor influence on the solution, maybe what you said that it donates small CO3
ions? Otherwise I will be curious as to why it is included in this recipe.
[Edited on 19-7-2012 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)
|
|
|
bbartlog
International Hazard
Posts: 1139
Registered: 27-8-2009
Location: Unmoored in time
Member Is Offline
Mood: No Mood
|
|
What are the ratios of the ingredients in your formula? Curious how basic it ends up being.
Anyway, CuCO3 is somewhat less soluble than even CaCO3, so I would *think* that under neutral conditions one would end up with calcium acetate (in
solution) and Cu(II) carbonate as precipitate. However, CuCO3 is amphoteric, so with the addition of enough NaOH at least some of it should go into
(or rather stay in) solution as cuprate. And yet your solution is not dark blue... I assume the amount of NaOH added is not a full equivalent to the
acetate?
As for the actual patina, I expect that it's mostly Cu2O. In general, Cu(II) oxidizes Cu(0) so that both end up as Cu(I). The other ingredients may
act to buffer pH or somehow affect the grain size of the cuprous oxide so as to give it the desired color. In general the chemistry of the colored
oxide layer on copper is complex; might be nonstoichiometric compounds involved.
The less you bet, the more you lose when you win.
|
|
|
CHRIS25
National Hazard
Posts: 951
Registered: 6-4-2012
Location: Ireland
Member Is Offline
Mood: No Mood
|
|
Hi, well here are the ingrdients:
Cu(CH3OO)2 @ 6.5g
CACO3 @ 2.25g
NAOH @ 2.25g
H2O @ 100mL
Left for a week.
3mL of the Top liquid drawn out and mixed with CUSO4 @ 1g and boiled.
I decreased the amount of water by 50mL to account for the fact that I can not make the anhydrous copper acetate. I also increased the amount of
clear liuid that you use from the 1mL to 3mL because, once again, my copper acetate is probably not strong enough due to the fact that I can not use
the pure anhydrous starter. All in all I seem to have it right because it works.
Quote:And yet your solution is not dark blue.unquote: No you're right, however it starts off quite pale blue but then moves within a few minutes to
really dirty anddark brown which then precipitates within 12 hours to the bottom, leaving a very subtle murky clear liquid on top. Interesting
though, if I even touch the jar with a gentle bang of a pen the precipitate is so fine that it swirls a bit, a bit like those old-fashioned lava
lamps. So when I draw out some liquid I have to be very careful not to even breath on the jar!
Very interesting what you said by the way.
[Edited on 20-7-2012 by CHRIS25]
[Edited on 20-7-2012 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)
|
|
|
|
![[*]](images/xpblue/default_icon.gif){kind=icon}
