Please read Pt I if you have not already.
We will start with a tub full of copper(ii) chloride, which has crusted over with unanticipated crystals. I added some water to remove the crystals and form an aqueous solution again. I can assume that there was not enough water present to fully dissolve all of the copper and chloride ions. This is because my acid was fairly concentrated. I added about 100ml of water. The greenish color was still fairly dark and hard to see through.
The goal here will be to turn iron into copper. I am also working up to turning lead into gold. Just joking, the goal will be to add iron and then have a reaction where the iron and copper swap places. This is known as a single replacement redox reaction. Then, I will have the pure copper that I want extracted from the malachite ore. Presently, that copper is in copper(ii) cations in the solution. We want pure elemental (native) copper with no charge as the product. The reaction is fairly simple:
Fe + CuCl2 -> Cu + FeCl2
The iron will be replaced with copper and the solution will contain iron(ii) chloride (or ferrous chloride). This is where I went wrong previously, adding iron filings. It was impossible to know when the reaction was done. I also did it all in one step so if anything did change, I could not see through the carbon dioxide gas bubbles. After some time and investigation, I realized I had an incomplete replacement reaction and my elemental metal was part copper and mostly iron. My solution was a strange mixture of iron and copper chlorides that kept changing colors and other weird things.
The answer is fairly obvious, it turns out. Sand the zinc galvanizing off of some nails and drop them in the solution. An iron nail and a copper crystal are easy to distinguish. After a short time, I could see copper growing around where the nail was being eaten away, creating cinnamon-like tubes of pure copper. Success!
I kept adding nails, confident that any unreacted iron would be obvious and I could just remove it. This way I would be sure to yield every atom of copper (more or less). I began to think about the copper(ii) chloride, and wondered if I could completely react it to a pure solution of iron(ii) chloride instead of a mixture due to limiting reagents. The answer is also simple: more iron nails!
I can do this because it so happens that Iron and excess HCl react to give me hydrogen gas and (voila!) iron(ii) chloride. So I kept throwing nails in until they were not changing. Then I knew all reactions had ceased. By the way, I had previously calculated that 50ml of 31.5% HCl was enough to react all of my copper (and then some).
Fe + 2HCl -> H2 + FeCl2
Two notes of warning: Perform the reactions outside or in vented areas. You do not want hydrogen gas in your house or near sparks. This is what happened to the Hindenburg. Also, ensure the galvanized nails are well-sanded so that zinc is not present in the reaction. Make sure the nails are iron or carbon steel and not some other metal. The amount of carbon in steel is small and won't impact the reaction.
When all reactions were complete, my solution was very pale and I had obviously reacted as much iron as possible:
While still reacting, I did play around with decanting the solution periodically to check my copper. Check this out!
I could not resist pulling a little bit of copper out and trying to melt it in a crucible with a propane torch. the melting point of copper is too high at 1983F. It only partially melted, and definitely oxidized on the outside to a black CuO (the mineral tenorite in nature). I also got the characteristic green flame of copper. You can clearly see copper crystals forming here as it heated and cooled. More on that later, they look better under a microscope.
Back to the final mess in my tub. I decanted the hydrated iron(ii) chlorate into a beaker for later use. I used a coffee filter and funnel and some distilled water to catch and clean any solid metal. The unreacted nails (iron) were simple to remove. I now have this solution for future experiments and some nice copper that I was able to crush in a mortar (like cinnamon again) and weigh.
Remember my goal was 10g or more. Well, I scored a whopping 12g! That is over a 90% yield, including the impurities of the mineral itself. There is no way my copper would be this pure or have yielded so high with smelting, although that is a cheaper way to go in mass quantities and you don't have corrosive by-products (known in the trade as pickle liquor).
Thanks for reading,
Paul
p.s. It has come to my attention that some people would like to repeat these experiments without the hassle of finding the chemicals and/or having to buy too much, etc. I will try to keep an Ebay store alive (seller: cinnabarminerals) that offers low cost and related material for the purpose of enabling education. I will title offerings "Brave New Chemist Science Pack - (related Blog post name)." You can always comment and ask where to buy certain equipment too.
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