Sciencemadness Discussion Board

Copper Pyrophosphate?

AlbinoMoose308 - 18-1-2021 at 19:46

I'd like to make some copper pyrophosphate (Cu2P2O7) for electroplating but I don't know how. I've got potassium pyrophosphate. Would a double replacement be appropriate? I can't seem to find information on the solubility of the copper salt...

Taking all suggestions
thanks :)

[Edited on 1-19-2021 by AlbinoMoose308]

Bedlasky - 18-1-2021 at 22:32

Yes, double displacement is possible, but add excess of copper salt. Pyrophosphates are very good ligands for divalent cations, so if you add excess of pyrophosphate, you get soluble complex.

Another option is thermal decomposition of ammonium copper phosphate (which can be made by precipitation from aqueous solution).

[Edited on 19-1-2021 by Bedlasky]

AlbinoMoose308 - 18-1-2021 at 23:44

Ammonium copper phosphate...
That could be prepared by adding copper oxide to a solution of monoammonium phosphate, right?
Do you think ABC type dry chemical from a fire extinguisher would work for that? (should be ~60% pure, the rest being ammonium sulfate) I happen to have a few pounds of the stuff handy. I could try that out tomorrow!

[Edited on 1-19-2021 by AlbinoMoose308]

vano - 19-1-2021 at 02:59

A few years ago I made sodium pyrophosphate from Na2HPO4. As far as I can remember very little pyrophosphate was dissolved in the water, which is very bad for the exchange reactions. I saw in a Chinese source that copper sulphate and sodium pyrophosphate are obtained, of course it is possible, but it is difficult when a few grams are dissolved in a liter of water. Copper pyrophosphate has light green colour.

Bezaleel - 19-1-2021 at 04:36

But as copper precipitates the (P2O7)4-, more of the ammonium salt should dissolve, unless the formed Cu2P2O7 sticks to the ammonium salt, preventing it to dissolve. Some agitation might help?

Bedlasky - 19-1-2021 at 12:24

Bazaleel: Where do you see ammonium ions in the reaction between potassium (or sodium) pyrophosphate and copper sulfate?

Vano: I didn't have issues with dissolving pyrophosphate. But I did it just once in the test tube when I made Mn(III)-pyrophosphate complex.

vano - 19-1-2021 at 12:58

Tetrasodium pyrophosphate Solubility in water. From Wikipedia.
2.61 g/100 mL (0 °C)
6.7 g/100 mL (25 °C)
42.2 g/100 mL (100 °C)
This compound dissolves quite a large amount in boiling water. It's enough. However it dissolves poorly in warm water. I meant that.

Did you mean manganese ammonium pyrophosphate? This is a different reaction. Here manganese goes from 2 to 3. Copper pyrophosphate is made by the exchange reaction. I made pyrophosphate from Mn oxide, phosphoric acid and ammonium dihydrogen phosphate.

Bedlasky - 20-1-2021 at 11:26

Vano: No, I don't mean NH4MnP2O7. I mean soluble complex [Mn(H2P2O7)3]3-. It's formed by oxidation of Mn2+ by permanganate in the presence of pyrophosphate in acidic solution. Mn2+ can be also oxidized in the presence of orthophosphate, but you need high concentration of acid.

This reaction can be used for manganometric determination of manganese using potentiometric determination of equivalence point.
Quote: Originally posted by vano  
Tetrasodium pyrophosphate
Did you mean manganese ammonium pyrophosphate? This is a different reaction. Here manganese goes from 2 to 3. Copper pyrophosphate is made by the exchange reaction. I made pyrophosphate from Mn oxide, phosphoric acid and ammonium dihydrogen phosphate.


Manganese goes from 4 to 3 (if you use as starting point MnO2, you can also use Mn2O3 or MnO(OH)).

[Edited on 20-1-2021 by Bedlasky]

vano - 20-1-2021 at 11:52

I do not know why I wrote 2. Can you tell me what color the solution was?

Bedlasky - 20-1-2021 at 17:33

Red.

rockyit98 - 20-1-2021 at 23:47

Disodium pyrophosphate can buy as food additive as buffering agent and as ingredient in leavening agents. Solubility in water 11.9 g/100 mL @ (20 °C) some what more than Tetrasodium pyrophosphate.try that.