Warning: Copper sulfate and formic acid are poisonous.
Wear gloves when handling them.
Greetings fellow nerds.
Some years ago i made silver conductive ink.
A liquid that when applied to a surface and then heated would decompose into metallic silver that was conductive.
A number of electrical engineers have asked if there was a copper analog of the same substance.
While it's not an exact analogue, in this video we'll make copper formate, a useful precursor to copper conductive ink.
We first start with 65g of copper sulfate pentahydrate.
This can easily be bought as root killer, or a pond algae control chemical in garden stores.
You can also make some as i've shown in earlier videos.
Now we add in 250mL of water and stir until dissolved.
This is going to take awhile.
Now in a separate container we get 33g of sodium carbonate.
To this we add 150mL of water and stir until dissolved.
You can also use sodium bicarbonate if you adjust the stoichiometry.
But i prefer sodium carbonate for this since it dissolves more than sodium bicarbonate.
Now we add both solutions together.
What we're making is copper carbonate hydroxide, sodium sulfate, and carbon dioxide gas.
It'll bubble a lot so it might help to stir it and keep it from overflowing.
It's pretty thick at first but as it reacts i find it thins out somewhat.
When the bubbling stops, the reaction is finished and we can now filter out our copper carbonate hydroxide.
Wash out the containers with water for quantitative transfer.
Also wash the precipitate with generous amounts of water to wash out the byproducts and impurities.
You can let it dry on the filter paper if you want but i'm going to use it directly as is.
We transfer the wet copper carbonate hydroxide paste over to another container
and wash down the filter paper with some water for a total volume of about 200mL or so.
To make copper formate we add in formic acid.
I'm using 32mL at first of what i thought was an azeotropic mixture of 77%
We made this formic acid a while back from glycerol and oxalic acid.
Anyway, stirring and turning on heating helps to drive the reaction forward.
The formic acid reacts with copper carbonate hydroxide to make copper formate.
Now I thought it would all react but when it did not i thought i didn't have enough water so i added more.
Turns out I was wrong as it still wasn't reacting so i added in another 20mL of formic acid.
Now it all reacts.
My formic acid must have been very dilute.
I'll probably have to go back and fractionally distill it again.
Anyway, let it cool and evaporate down to 100mL of volume to get crystals.
I don't recommend boiling it down as it will decompose.
I also didn't let to evaporate dry since i want the soluble impurities to remain in solution.
Now we filter out the crystals.
Give them a wash of ethanol then let them dry on the filter paper.
And there it is copper formate tetrahydrate.
So what can we do with this?
If you get a solution of it and heat it up past 200 celsius the copper formate decomposes into copper, carbon dioxide, and hydrogen gas.
Now the copper produced isn't anywhere near as solid or high quality as what was produced with silver conductive ink.
As you can see i can get brief flashes of conductivity, but nothing reliable.
The particles don't seem to be all that well bonded.
But i'm hoping this low level copper is still good enough for something called through-hole plating.
A process electrical engineers use to make printed circuit boards.
But i'll cover that in an upcoming video.
Even if this can't be used as-is, copper formate is still a good precursor to copper conductive ink since it does indeed generate copper.
In fact in the literature there are chemical additives that make it viable.
I'll see if i can find an amateur solution.
If i'm successful i'll make a video on it.
Thanks for watching.
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