Re: Lab 10.1 (reduction of copper ore to copper metal)

[The Home Scientist]

Copper carbonate is just over 50% copper by mass, so depending on how much copper carbonate you used and how strongly/long you fired the crucible you may get anything from small beads/grains of copper metal scattered through the matrix after firing to an actual chunk of copper at the bottom of the crucible. It sounds like you used a relatively small amount and may not have fired the crucible for long. (If you fire it longer/hotter, the grains of copper eventually melt together and form a mass of relatively pure copper at the bottom of the crucible.)

Still, if you fired it hot and long enough for the copper carbonate to disappear, there's copper in that mix. Try crushing the matrix as completely as you can and then mixing/washing it with water. The remaining carbon is much less dense than copper metal, which should settle out to the bottom of the wash, probably as tiny grains of metal.

On Saturday, March 2, 2013 1:03:12 PM UTC-5, jeff warden wrote:

Hi all,

My 10 year old and I just completed this lab but unfortunately can find no copper metal in our crucible.  We followed the procedure carefully but the result in the crucible is jet black carbon.  It appears that the green copper carbonate has just disappeared.  I'm wondering how much metal we should be looking for; perhaps it's so tiny that we're just missing it?  At any rate my kid's pretty disappointed as he was planning on making a copper axe or something.  :-)  Any pointers?

[jeff warden]

OK excellent, thanks.  We'll try again but fire it longer.  The lab specified 15 minutes and we fired for 20.  We'll just let it go for an hour or so and see what we get.  Thanks for the help!

[The Home Scientist]

You are using a gas burner, right? Propane, butane, and natural gas all burn in air at just under 2,000C. Copper melts at around 1100C, so you should have plenty of margin. If you still have problems, you might try using a blowpipe for a few minutes to increase the temperature in the crucible. I had no such problems when I used a butane microburner, so you should probably be okay.

[The Home Scientist]

Incidentally, make sure to position the burner and crucible so that the hottest part of the burner flame impinges directly on the bottom of the crucible.

[jeff warden]

Ahaa, we're using a burner with denatured alcohol, and I guess that was the problem.  I have a hand held butane burner so I'll give it a boost with that this time.  I didn't realize the alcohol burner wasn't hot enough.    Thank you for the help! 

[The Home Scientist]

That's the problem. Even with a blowpipe, an alcohol lamp may not be hot enough. We discussed this issue on page 31 of the book.

[jeff warden]

My apologies for the tardy reply.  The heat was the issue as you said, and using the extra burner did the trick.  We had a great time working through the lab (and figuring out what I missed).  Thanks for the help.