Hi everyone welcome back to Cody's lab so in another project the video which probably won't be posted till early next month
I acquired a bunch of sand that had a little bit of fine gold powder in it. You can see here
I've panned it out using a gold pan I
gold is usually very easy to separate from sand because
Gold's high density makes it so that it sinks down to the very bottom. You can actually kind of see that here. How it's
kind of separated in the gradient
But also water as you kind of wash it against the gold
The Gold's high density means that it has a high mass to surface area ratio
but the problem here is that the
Cube law is making it so that the mass ratio is actually
Not that significant. You know a little bit of flowing water
Actually can move this gold around quite easily
You know relatively easily in fact
This is about as concentrated as I could make it before the gold starts washing over the lip of the pan
That you know normally the sand will protect the gold from that happening
But once there's not enough sand to do that then the gold kind of mixes with the sand
And it flows right over the top also know if you can see if I like rock the pan back like this
And let it dry out for a second, and then push it back
And you see some of the gold actually floats on the water
You see that right there, that's surface tension doing that
Despite the fact that gold is nearly twenty times denser than water
you're actually watching it float because the size of the particles are just too small to punch through the surface tension
I can break that up adding a little bit of soap
You can see the particles
swimming around and also by giving a little bit of agitation to push the
gold down below
But that really is a problem if I were to try to continue panning at this I would just lose more and more gold
You can see even over here where the gold looks like it's pretty pure already. I kind of agitated a little bit
You can see that it is trapping quite a lot of sand
normally given the situation
I would either
Put a drop of mercury in there to collect all the gold
or I would just put the whole mass of it into a furnace along with some flux so I can melt the gold into a
Single bead. But today, I really wanted to try using this
This is Clerici Solution, which is made using thallium. Now this is probably worse than using mercury, but
I wanted to know if it works
Yeah
Theoretically it should because this solution weighs about 4 grams for cubic centimeter and the sand down there
Weighs about three and gold of course which is much heavier than four will sink
So let me dry off all this water here and transfer it into a test tube
Let's see what happens when I combine it with a heavy liquid
Let's see if this will make the sand float all right
There's about 2 milliliters worth
Let's get that mixed in there
Now I see what's happened the addition of the sand has caused my solution to crystallize
Should be a simple matter of warming it up to redissolve the crystals
But you can already see that the gold has sunk to the bottom of the test tube
So here we are after warming it up to liquefy the solution you can see that
There is a layer of sand floating on top and a layer of gold
On the bottom. Now the gold still has some black specks in it, and that would be my iron oxides
iron oxide is a bit heavier than the solution so
You can actually see it's kind of separated a little bit, though
See the Gold's on the under you see the Gold's underneath the black sand
So now I'll just pull this off with a pipette. I mean wash this with water to remove the thallium
So there it is everything that was heavier than about four and a half grams per cubic centimeter
That does include the black sand like I mentioned but fortunately that should be pretty easy to remove
Just use a magnet there does seem to be a few non-magnetic grains. That's probably hematite or
some other
heavy mineral
Looks like there might be a few zircon crystals in the mix
But that is pretty much pure gold
Certainly if I melted this down it would melt down into a bead of gold just fine
It'd still need to be refined, maybe run through acid to get rid of everything else, but there you go. It's a mostly pure gold
The Clerici solution is of course completely reusable
I'll just uh
Dilute it with water to lower its density so the sand sinks just as you can see I've done there
And I'll just wash the remaining solution out of the sand
There, after a few washings, I'm left with some clean sand that uh
Should have very little thallium left, so this would be safe to dispose of and
of course I have some really dilute Clerici solution that has maybe got a little bit of dirt suspended in it
I will have to filter and evaporate this down before I can use it again
But that's not really a problem
So let's see how much gold I was able to recover
Okay
Looks like about a tenth of a gram
It's not bad I definitely lost some, but there you go. Hope you enjoyed. I'll see you next time
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