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Are there any ways to figure out if the copper foil and mesh I have are pure, as-close-to 100% copper as possible (and as advertised)?

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    $\begingroup$ How pure do you need it? 99% (2 9's)? 99.9999999% (9 9's)? Question without context is meaningless. $\endgroup$ – DrMoishe Pippik Mar 29 '20 at 2:08
  • $\begingroup$ @DrMoishePippik I am a layman– I don't have a good sense of what the difference is, but I just want to know if what I have is an alloy or is mostly pure copper. $\endgroup$ – aroooo Mar 29 '20 at 6:20
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    $\begingroup$ There is no easy or simple home test for copper purity. $\endgroup$ – MaxW Mar 29 '20 at 8:11
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    $\begingroup$ I don´t remember numbers and details, you´ll have to find sth online. But "pinkish" sounds good, purer than your ordinary rain gutter material. $\endgroup$ – Karl Mar 29 '20 at 9:05
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    $\begingroup$ I doubt color could be really useful. First it does not give you any numerical data. And metallic copper sheet are usually superficially oxidized, and covered by black copper oxide. I remember having deoxidized a small sheet of copper by heating it in a Hydrogen atmosphere. The copper so obtained is nearly pink or pinkish ! So the typical brownish color of commercial copper is due to a partial oxidation process. $\endgroup$ – Maurice Mar 29 '20 at 10:12
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As a home tool, but not necessarily a definitive solution, I would suggest the dissolution of your copper metal/alloy in a galvanic cell where the Cu is the anode and as a noble cathode, use a source of graphite.

This approach for the dissolution has been favorably argued in commercial patents in a 1999 U.S. Patent 6,692,632. To quote in parts:

The method is preferably used in synthesis, but can also be useful in the destruction of pollutants etc. In certain embodiments of this nature, the use of external current applied to the system is not necessary, and a simple galvanic cell can be set up...

On copper particularly, for the home chemist, I have demonstrated a so-called Bleach Battery approach as an electrosynthesis path discussed in 'Subject: Experimental Variants of Bleach Battery to Obtain Metal Oxides (like CuO). However, I would replace the cathode, as in the current case as Nickel could be present as an impurity also in your copper metal sample, with very noble graphite in its path to CuO and other metal oxides that may become evident (or be chemically identified).

As the copper can be alloyed with metals like Zinc, Tin, Aluminum, Nickel, Silicon,..., with the first three creating respective oxides from the dissolving a small piece of the copper metal/alloy, potentially revealing distinct metal oxides as, for example, CuO is black, ZnO is white, SnO is blue-black (as produced by heating the tin(II) oxide hydrate, SnO·xH2O where x<1), and Al2O3 varies from white to a clear transparent gel. The metals Nickel and Silicon are expected in their metallic state.

I say, convert a bit of it into metal oxides and proceed from there!

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  • $\begingroup$ How can we estimate the purity of copper from obtaining other metal oxides? $\endgroup$ – Micelle Mar 30 '20 at 6:23
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+If you are in the US ( and many other places)you have copper 101 or 102 ( CDA = Copper Development Association designations), with 99.95 % minimum Cu. CDA says this Cu is what is supplied under the following ASTM Material Specifications- B48, B132 ,B152 ,B187 , B272 , B432 ,and F68 ; all flat Cu products. The same Cu is supplied in other shapes in other ASTM specs. Do you know the ASTM designation of your material ? What is your application where 99.95% + Cu content may not be sufficient ?

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    $\begingroup$ Review of a old ASTM indicates your material is likely B152. The 1981 revision lists several UNS copper grades , all range from 99.90 to 99.99 % Cu. I doubt the chemical requirements changed much since then. $\endgroup$ – blacksmith37 Mar 30 '20 at 2:13
  • $\begingroup$ Excellent answer! I upvoted because, unless one has access to proper spectroscopic analysis instrumentation, home analysis is completely futile. I happen to have a fair bit of copper on hand, including two pieces of OFHC copper sheet: 24"x8"x3/16" and 15"x8"x3/16". Fortunately, copper has to be highly pure for most of its intended industrial purposes. $\endgroup$ – Ed V Mar 30 '20 at 2:36

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