Aqua Regia dissolves Gold – Periodic Table of Videos

Aqua Regia dissolves Gold – Periodic Table of Videos


Aqua Regia, Royal Water, is a mixture of two
acids, hydrochloric acid and nitric acid. The reason
it’s called ‘royal water’ is because it dissolves
gold. Gold has fascinated people for thousands of years because
it doesn’t dissolve in anything, doesn’t
tarnish, always looks nice and shiny, and this was a material
that could dissolve it. So it was really something, the
lion of the acids, like the lion of an animal, king of
the animals! So Aqua Regia is a mixture of hydrochloric
acid and nitric acid, but each of those is a mixture
of something in water, a solution of something in water.
So hydrochloric acid is hydrogen chloride, which
is an atom of chlorine bonded to an atom of hydrogen,
now the importance of this is that when the HCl dissolves
in water the bond between them breaks and you
get chloride ions, Cl-, and H+, hydrogen ions,
and it is the formation of hydrogen ions which makes something
an acid. So when you have the mixture of all
these ions you get quite a soup. Now the exciting thing about
Aqua Regia is that neither of the two acids by
themselves can dissolve gold. Nitric acid doesn’t really
react with gold very much at all, and HCl, hydrogen chloric
acid can’t get a hold of the gold to get the reaction
going. But if you can gold into solution then it can react.
So what happens is as follows: the nitric acid can
attack the gold and a very small proportion of the gold, relatively
few atoms, are persuaded into going into solution
and there is an equilibrium, some are coming off and
an equal number are going back on to the surface. So
if you just have the gold in there it appears to be unaffected.
If you were on an atomic scale you would see atoms
coming off and others going back, but nothing changes.
But when you have the hydrogen chloride there,
the chloride ions can attack the gold and turn them into
a different compound so they can’t go back. So more
and more and more gold atoms come off, until eventually
all of it is converted to another acid, which is an acid
of gold with four chlorine atoms around it. This material
is then quite soluble in water, so provided you don’t
have too much gold it will all dissolve. And once you have
the solution, you will get a brownish solution or greenish
solution depending how much gold is in there. I’ve never seen Aqua Regia because it’s
quite a nasty material, you have to use it in the fume cupboard,
because otherwise, because of these fumes of NO2 and
unless you want to dissolve gold, you don’t usually need
this. It is a pretty good cleaning material if you have
glassware, beakers things like that that you can’t clean
any other way. The sort of last resort is ‘we’ll try Aqua
Regia to see if that’ll do it?’ you know really bang the
dirt. And it sometimes works, not always, depends what
the dirt is. Aqua Regia is Latin, for Aqua is the Latin
for ‘water’ as in ‘aqueduct’ and also we use it in English
and the word ‘aqueous’ and things like that. There
is…and Regia is the Latin for ‘royal’ as in ‘regal’, and
comes from the word Rex which means the word ‘king’ in Latin. Well there is quite a famous story about Aqua
Regia and the institute of Niels Bohr, the Nobel Prize
winner, who had an institute in Copenhagen and at the
beginning of the Second World War when Denmark was still
neutral, two German Nobel Prize winners, Max von Laue
and Frank who had won the Nobel Prize before the
Second World War sent their gold medals for safe-keeping
to Denmark and someone in the lab at, in Denmark,
dissolved them in Aqua Regia and just put the bottle on
the shelf where there were lots of other bottles of
chemicals and they stayed there the whole war because
nobody realised that they were gold and after the war
the gold was recovered, the medals were re-struck and
given back to the Nobel Prize winners.

100 Comments

  1. The analogy that comes to mind for me (which I hope is accurate) is tossing a ball up and down. Say you have a tennis ball, racquet ball, whatever, and you start tossing it up in the air; after which it naturally comes right back down. The hand tossing the ball up is like the nitric acid liberating gold atoms from the rest of them, after which they basically all fall back down and reattach to the "lump" of gold. But adding hydrochloric acid is like a different hand coming in from the side right after the ball is tossed up and catching it before it can fall back down.

  2.  Can Aqua Regia dissolves human flesh? i just wanna build a concentration camp in Iraq (Babylonia futuristically) as i rise to power to rebuild and re-social engineer the country. Any answers?

  3. 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

  4. Wow, so you could potentially rob a bank that holds a lot of gold and dissolve all of it as a way to keep it relatively well-hidden?

  5. But does the lab recovers the gold from this kind of experiments? Despite they might be well stocked in chemicals, I don't think they'd just dissolve gold and throw it to the garbage. How is the recovery done?

  6. sir I have a aqua regia black liquid suspension of gold in aqua regia. I added SMB from Stump Out to precipitate but it did not work. It fizzed, but the SMB fell to the bottom and the black liquid did not precipitate the gold. What should I do now?

  7. 3:33 Isn't hydrofluoric acid the last resort for cleaning glassware? "Aqua Regia didn't work, let's just dissolve the glass away." (Though, I guess if HF somehow didn't work, you could try fluoroantimonic acid. Before that though, maybe you should just consider buying new glassware.)

  8. 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?

  9. Love the professor's computer desktop – the true trait of a genius are messy tables, messy drawers and messy desktops.

  10. I have seen in some other videos that when the gold dissolves in aqua regia, the mixture turns green. It is because of impurities ?

  11. Step 1: get gold
    Step 2: make aqua regia
    Step 3: dissolve gold in aqua regia
    Step 4: bubble ammonia gas through gold solution
    Step 5: profit
    spoilers

    no actual profit, just explosions when dry

  12. Step 1: get gold
    Step 2: make aqua regia
    Step 3: dissolve gold in aqua regia
    Step 4: neutralize the solution
    Step 5: get metal with similar density with gold
    Step 6: make the metal in the shape of gold bar
    Step 7: place the metal in the solution

    Convincing Gold bar that passes all test

  13. This stuff gives off lethal gases, Chlorine, which essentially melts the linens of your lungs due to the reaction with the mucus to form hydrochloric acid.

  14. Why dont you post a video about recovering that gold from Aqua Regia.. (pardon me if it is already been uploaded, I haven't seen yet)

  15. An interesting explanation of why aqua regia dissolves Gold.
    It is also the case though that if strong Hydrogen Peroxide solution is added to Hydrochloric acid, not only will it strip the copper from a printed circuit board, but it will also dissolve the gold.

  16. i've created something that looks like aqua regia, by putting copper in Trichloroacetic acid and boiling it on a stove (liquid turned light cyan), can you explain what i've created.

  17. How about Decon?

    I once heard tell of an organic chemist who had a pair of high-quality quartz UV cells of which he was very proud. He decided to give them an overnight soak in neat Decon to brighten them up a bit.

    The next day, he was angrily accusing everyone else in the lab of having stolen them – until someone pointed out that the black bits at the bottom of his beaker could be rearranged to spell PERKIN ELMER.

  18. Its important to note he's talking about acids in the Bronsted-Lowry definition. There are other types of acids that do not involve the donation of a proton.

  19. Sir I have a ? for you based on many videos I have watched and studied. Is there a new tech that allows anyone to dissolve gold with a citric acid based setup. I watched on where they dipped in cpu boards and with in 15 to 30 sec, the gold was off. No electrolysis applied in action. Very impressive and applicable more than you can imagine if true. looking for this formula for me and others. Can you help in any way.

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