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Author: Subject: Copper Tartrate
nlegaux
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[*] posted on 25-12-2014 at 12:42
Copper Tartrate


I haven't been able to find any (useful) information on Copper Tartrate. The only information I could find was on the wikipedia page about Tartaric acid (http://en.wikipedia.org/wiki/Tartaric_acid), where it mentions that tartaric acid forms a complex with copper. Does anyone have any good information on this complex?

Out of curiosity, I added Potassium Bitartrate to a CuSO4 solution (excess of CuSO4). The solution turned a pale blue color. When IPA was added, a pale blue non-crystalline precipitate formed. Is this Copper Tartrate?

Thank you,

nlegaux
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Metacelsus
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[*] posted on 25-12-2014 at 19:20


Tartaric acid and copper are used in the biuret reagent; tartaric acid and copper definitely form a complex. Copper tartrate should be isolable, but I'd prepare it by directly reacting tartaric acid with copper hydroxide.



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Amos
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[*] posted on 25-12-2014 at 19:21


I have made a deep blue complex, similar to the tetraammine copper(II) complex but without any hint of violet coloration, by adding potassium/sodium tartrate to a solution of copper(II) sulfate and heating. The tartrate I believe was produced by adding sodium carbonate to an excess of potassium bitartrate in solution. I wish I had kept some notes on that...



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Paddywhacker
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[*] posted on 25-12-2014 at 20:45


I once made some by dissolving copper(II) oxide in aqueous tartaric acid. The two were in stociometrically equal amounts and the container was heated in a pressure cooker for 30 minutes.

All of the black oxide dissolved to give a pale blue precipitate that was soluble in excess potassium hydrogen tartrate solution. Somebody suggested that I had the basic tartrate salt, but I don't believe that. So the straight salt was only sparingly soluble, but it dissolved in excess tartrate to form the usual complex. The complex should have also been stable to alkali, but I didn't test for that.

A similar experiment with citric acid was similar, but not all of the copper oxide dissolved.
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nezza
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[*] posted on 26-12-2014 at 02:00


Copper sulphate and Sodium potassium tartrate (Rochelle salt) form the basis of Fehlings solution which is a classic test for reducing sugars. The mixture is boiled and copper(I) oxide is formed as a yellow/red precipitate. The tartrate keeps the copper ions in solution in an alkaline solution by complexing with the copper.
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Dr Corvin Ravenden
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[*] posted on 13-9-2018 at 01:34


The easiest way of preparing a crude solution of cupric (copper II) tartrate is to use the old technique used by ancient alchemists in order to clean copper coins.
First boil a concentrated solution (verging on a suspension) of Cream of Tartar (Potassium Tartrate) and then throw in a load of old copper coins whose surface will be coated with a variety of impurities (these are of minor significance) including cupric oxide which will rapidly be dissolved into aqueous solution as a copper (II)-tartrate complex. As time goes by you will observe a) the surface of the coins becoming visibly cleaner and shiny and eventually the solution will turn to a pale blue-green colour demonstrating the presence of copper (II) hexa-aqua complex ions and one assumes in some sort of association with tartrate.
This is a good method for a quick result normally within 30 minutes as it avoids the use of using copper (II) sulphate that however lovely Blue Vitriol is, it tends to mask the colour of the tartrate that is less soluble than the sulphate, hence boiling the coins in an old Teflon coated plan. Copper coins also substitute for normal cupric oxide that can be difficult to find and purchase in some countries.
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[*] posted on 13-9-2018 at 04:47


Quote: Originally posted by Dr Corvin Ravenden  
The easiest way of preparing a crude solution of cupric (copper II) tartrate is to use the old technique used by ancient alchemists in order to clean copper coins.
First boil a concentrated solution (verging on a suspension) of Cream of Tartar (Potassium Tartrate) and then throw in a load of old copper coins whose surface will be coated with a variety of impurities (these are of minor significance) including cupric oxide which will rapidly be dissolved into aqueous solution as a copper (II)-tartrate complex. As time goes by you will observe a) the surface of the coins becoming visibly cleaner and shiny and eventually the solution will turn to a pale blue-green colour demonstrating the presence of copper (II) hexa-aqua complex ions and one assumes in some sort of association with tartrate.
This is a good method for a quick result normally within 30 minutes as it avoids the use of using copper (II) sulphate that however lovely Blue Vitriol is, it tends to mask the colour of the tartrate that is less soluble than the sulphate, hence boiling the coins in an old Teflon coated plan. Copper coins also substitute for normal cupric oxide that can be difficult to find and purchase in some countries.
What kind of countries would CuO be difficult to find? I don't think CuO could be used to make any drugs or explosives.



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Jackson
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[*] posted on 13-9-2018 at 10:21


nlegaux, you said you added IPA to the solution which cause a precipitate. Did the IPA cause the precipitation? Does IPA precipitate all copper salts?
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DraconicAcid
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[*] posted on 13-9-2018 at 12:37


Quote: Originally posted by Jackson  
nlegaux, you said you added IPA to the solution which cause a precipitate. Did the IPA cause the precipitation? Does IPA precipitate all copper salts?


Adding an alcohol to an aqueous solution will reduce the solubility of all ionic compounds.




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