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Author Topic: white precipitate formation during CuSO4 preparation  (Read 951 times)

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skilpadderr

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white precipitate formation during CuSO4 preparation
« on: January 11, 2017, 09:31:17 AM »

I make CuSO4 by mixing stechiometric quantities of Cu2O with sulfuric acid and diluiting all whith 3,6% hydrogen peroxide until all the copper is dissolved. the problem is that i noticed the formation of a white and light precipitate.

i was able to separate easily to obtain a pure slution of copper sulfate but i couldn't really get what that stuff is.

the Cu2O was obtained from electrolisys of a NaCl solution at 18 V and sulfuric acid (that should be around 90%) by puryfing a drain cleaner. at first i tought it was CuCl impuritiy from the copper oxide but i get the precipitate even by making the same procedure written upside with pure copper.

i washed the compound many times with water and when dried it took a pale pink color.

thank you, that's my first ever post in a forum, don't worry about me using sulfuric acid because i work on really small quantities with glasses and mask, i apologise for my (hope not so) bad english, and please be kind, this is the first time i write in a forum.

thanks!
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Borek

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Re: white precipitate formation during CuSO4 preparation
« Reply #1 on: January 11, 2017, 11:37:47 AM »

the Cu2O was obtained from electrolisys of a NaCl solution

Please elaborate, no copper in this procedure.
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AWK

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Re: white precipitate formation during CuSO4 preparation
« Reply #2 on: January 11, 2017, 01:37:32 PM »

Just use copper with hydrogen peroxide and sulfuric acid without electrolysis.
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skilpadderr

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Re: white precipitate formation during CuSO4 preparation
« Reply #3 on: January 12, 2017, 05:13:20 AM »

the Cu2O was obtained from electrolisys of a NaCl solution

Please elaborate, no copper in this procedure.

you are right, i was obviously using a copper electrode at the anode
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skilpadderr

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Re: white precipitate formation during CuSO4 preparation
« Reply #4 on: January 12, 2017, 05:17:05 AM »

Just use copper with hydrogen peroxide and sulfuric acid without electrolysis.

i wrote that the precipitate is forming even with this procedure.
anyway my problem is not the formation of that compound, i just want to know what it is!
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AWK

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Re: white precipitate formation during CuSO4 preparation
« Reply #5 on: January 12, 2017, 05:29:18 AM »

The only metals that can accompany copper in its alloys and form white precipitate with sulfuric acid are silver and lead.
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skilpadderr

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Re: white precipitate formation during CuSO4 preparation
« Reply #6 on: January 12, 2017, 05:46:19 AM »

The only metals that can accompany copper in its alloys and form white precipitate with sulfuric acid are silver and lead.

mmh copper was pretty pure (from eletrical wires) but maybe some lead was present in the drain cleaner that i used to obtain sulfuric acid, is this possible?
the original product was a dark solution but after heating it with a bit of hydrogen peroxide it turned perfectly clear and trasparent
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