Gold Coin Dissolving in Acid (Aqua Regia)

Gold Coin Dissolving in Acid (Aqua Regia)


Warning: This reaction produces toxic gases and uses corrosive acids. It should be performed in a fume hood with gloves. Greetings fellow nerds. In this video we’re going to dissolve a gold coin in acid. Here is the coin. It’s a 1/20th troy ounce canadian maple. Now we add 10mL of concentrated 12M hydrochloric acid. By itself the acid does not react with the gold so we add another 1mL of concentrated 15M nitric acid. The mixture is gently heated to speed up the reaction. Eventually the mixture will turn yellow and bubble as the gold starts dissolving. We showed in a previous video that gold will not dissolve in either hydrochloric acid or nitric acid alone. What’s happening here is that the nitric acid is first oxidizing the surface of the gold. Then the chloride ions in the hydrochloric acid reacts with the gold ions to form a complex ion that dissolves away into solution. The nitric acid then further oxidizes the surface and the process repeats. Other oxidants also work but nitric acid is the easiest to work with. The bubbles you’re seeing are nitrogen dioxide gas along with some nitrosyl chloride, chlorine and nitrogen monoxide. This mixture of hydrochloric and nitric acid is also known by the name of aqua regia. Aqua regia does not destroy all metals though. I showed in a previous video that ruthenium is totally immune to aqua regia. Hmm, looks like the reaction is slowing down, I’m going to add another 1mL of nitric acid. Overall what we’re producing in this reaction is chloroauric acid. There is a famous story among chemists: During world war II hungarian chemist George de Hevesy dissolved the gold Nobel Prizes of German physicists Max von Laue and James Franck in aqua regia to prevent the Nazis from finding them. This deep orange solution was what they would have seen on the shelf. All the gold atoms are still there as ions, and they can easily be returned to metal with the proper reducing agent. Looks like the reaction is complete. We have destroyed a gold coin and converted it to chloroauric acid using aqua regia. Leaving it for a few weeks in a desiccator bag we can dry it and produce this solidified form of chloroauric acid. Thanks for watching.

100 Comments

  1. Would a mixture of nitric acid and Hydroflouric acid or nitric and Hydrobromic acid or hydroiodic acid dissolve gold

  2. Hi guys I just I'd like to add something here. Be very careful with nitric acid. It is an oxidizer so keep all flames sparks sources of fire away from it. Oxidizers will significantly enhance the flammability of all fuel sources that it is in contact with.

  3. Oh btw, that looks like a gold maple leaf. Gold maple leaf is a legal tender in canada. Destroying legal tender is illegal.

  4. bleach also works as an oxidant but this releases large amounts of chlorine so a respirator is mandatory, additionally if you want to make pure chloroauric acid it is best to use nitric acid since side products such as sodium chloride is produced which will contaminate the acid. so this is only limited to refining gold 

  5. @NurdRage  Could you take this one step back? I'd like to see the chemical refinement of the ore. It will be a slight challenge because usually gold ore has some other precious metals in them. The old fashion way of grinding and panning seems too laborious, why not let science do the work?

  6. I was able to dissolve gold with HCL and a few prills of Sodium Nitrate.  Was this expected behavior?  Can the reaction be made to occur faster by using Nitric acid instead?

  7. METALS DO NOT DISSOLVE IN LIQUIDS.

    This is a matter of symantics, please, use technical vernacular.

    What we have here is SOLVATION–when a solute (gold) particle leaves tge bulk solid it becomes surrounded by solvent (aqua regia) particles. There is no change in composition, thus, it is a physical process. No dissolving here

  8. Impressive, not into chemistry, but the possibilities are endless.
    I have to stop watching these or I will get hooked.

  9. "It should be performed in a fume hood and gloves."

    I can't help but be a stickler prick and imagine the experiment taking place inside the fume hood and gloves. Please don't kill/yell at me.

  10. Hi I'm trying to get list saying what metals or materials Aqua regia can solve or dissolve.
    There is anywhere some kind of complete list with soluble materials on aqua regia?

  11. Good video sir but the point is what the hell is Aqua Regia I heared so many times in Science Subj.

    Gallium can RIP Apart a Gadgets like smartphone

    Like what you said Aqua Regia is a acid type that ruins metal but in some specific type

    Please give me a specific answer about Aqua Regia please….TY sir

  12. It was found by aqua regia Abu Musa Jabir bin Khayyam. And he is a Muslim.(Türkish) Kral suyunu Cabir Bin Hayyam bulmuştur. Müslüman simyager.

  13. AQUA RGIA was actually prepared by Abu Mūsā Jābir ibn Hayyān (c. 721 – c. 815) and he was a Muslim lived and died in Kufa city/ IRAQ. At the time of his discovery, he named this new acid in Arabic "The royal water الماء الملكي".

  14. It seems to me that it would be easier to dissolve the coin if you did a couple of things. First, use a 1g Maple instead of a 1/20oz. Maple. It's a smaller, thinner coin. Gold is very malleable so you could hammer the shit out of it on an anvil until you get a much thinner coin. It might be too much work to make a foil out of it, but the much larger and thinner piece of gold could be folded up and put into solution. Maybe the whole reaction could be done at room temperature so you wouldn't have to watch it all the time.

  15. 0:50 – The reaction mechanism is wrong! There is formed an atomic chlorine. Which also reacts with gold.

  16. can someone clear my doubt ? in my textbook it is said that 3 parts of conc.hcl and one part of conc.nitric acid to prepare aqua regia …is it wrong?

  17. I smelt with lead, then remove the lead by cupel. Left with a mixed metal button. End result need the gold. I need to remove other metals first, then AR for the gold.Any idea's on how? Thank's

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