How to determine purity of copper

Gold Refining Forum

Help Support Gold Refining Forum:

This site may earn a commission from merchant affiliate links, including eBay, Amazon, and others.

Shark

Well-known member
Joined
Jun 8, 2014
Messages
2,922
Location
Alabama
Having read with interest the recent thread on the testing of the purity of silver

http://goldrefiningforum.com/phpBB3/viewtopic.php?f=41&t=25954

4metals method was very interesting and seems pretty straight forward. It has me curious if there is such a method that could be used for copper. Something fairly quick, and can give a base indication if it is with in the 3N or better range.
 
A very sensitive ohm meter (would need to be able to measure +/- 1 nano-ohms) will tell you whether the copper is pure, since very minute amounts of contaminants quickly increase the resistance of copper.

One could use a resistivity meter to measure the resistance of the copper metal per unit length and cross-sectional area and compare that to the known resistivity for electrolytic purified copper, which I believe is about 17 nano-ohms per meter.

Edit: clarified and simplified
 
I was hoping for a wet method as I am more curious about copper powders. I will have to research a more sensitive meter as I know mine won't come close to nano-ohms.
 
I picked up a copy of Engineering Metallurgy (Stoughton, Butts & Bounds-4th Edition) today, it has a great explanation of of the resistivity test. I need a lot better meter and a way to make the wire to test it.
 
It may be helpful to know, assuming most of the impurity is iron, that copper 9999 will be attracted to strong magnet, while 99999 will be rejected. The magnet in the drawing has 18000 gauss
 

Attachments

  • copper rejection.jpg
    copper rejection.jpg
    139.7 KB · Views: 101
It may be helpful to know, assuming most of the impurity is iron, that copper 9999 will be attracted to strong magnet, while 99999 will be rejected

Trouble is .99 or even .90 will likely be magnetic as well so it can only indicate very high purity.
 
Shark said:
I was hoping for a wet method as I am more curious about copper powders..

I may have found something worthy of mention. It is the ASTM standard procedure.

From what I gather, it is basically dissolving the copper and precipitating its standard impurities. Silver as chloride, antimony, arsenic, and selenium as bromides.

It is supposedly for determination of anode purity, for 97%-99% purity, or for blister copper. So, it may be of little use for testing 2 more significant digits on your cathode deposits.

It looked like the reagents needed would be easily accessible though
 

Attachments

  • ffa2529b0bde30cc76cef08c5311c5b9.pdf
    76.5 KB · Views: 12
I will have to read that a few more times, but it sounds like it may be pretty close. Thanks for the pdf.
 
Back
Top