[ch0psu3y]

Hi everyone,
I wasn't sure where to put this topic so I hope this is the appropriate place. Anyways, is there anyway to fool Archimedes 'golden crown' trick so that gold and the fake crown would displace the same amount of water? I thought maybe you could synthesize an element to have the same density but I really don't have any idea if that would work or if that's even possible.

For those who don't know about the golden crown, here's a link to the story: http://www.math.nyu.edu/~crorres/Archimedes/Crown/CrownIntro.html

[enahs]

I do not know about the metallurgy or practicality of this (and I know it not possible in Archimedes time). But Tungsten and Gold have nearly the same density, very close. If it is possible from a metallurgical standpoint to make a crown out of mostly tungsten with just the coating in gold, it could easily fool the water displacement method. If you follow the calculations on the site you linked, but use the density of tungsten, we are talking about many thousandths of a millimeter difference in water level.

[Mitch]

All man-made elements decay, and would give off particular identifying radiation.

[ch0psu3y]

All right, thanks a lot guys.   

[billnotgatez]

Were Copper, Gold and Lead all known at that time in history?
Can an alloy be created of any of these?

[Arkcon]

Were Copper, Gold and Lead all known at that time in history?
Can an alloy be created of any of these?

The story goes that a dishonest goldsmith substituted silver for gold.  To get away with it he'd need something denser than gold, cheaper than gold, to counteract the lower density of silver.  Look here, http://en.wikipedia.org/wiki/List_of_elements_by_density and you can see, there is no such element.  Of course, the original poster's link tells us, that Archimedes didn't likely have testing equipment with sufficient accuracy to make the legend workable.  So the discussion is completely academic.

[billnotgatez]

Are you sure lead is not denser than gold?

[Arkcon]

I have never measured them, but the list on wikipedia puts gold far above lead, that seems to bear out anecdotal evidence -- it appears in historical accounts and fictional stories, that you can't easily steal lots of gold, it is just too heavy.

There is also the osmium/iridium controversy.  From their atomic masses, they should be among the densest elements.  But we have to conjecture, based on their crystal structure, which will "pack the most atoms" into a given space.  Experimentally, its hard to get a big enough hunk of these elements, because they're so costly.  The difference is at the second decimal place, so a small error in measurement can screwup the result totally.  In the CRC I have, the debate extends, to whether or not the ingot of osmium or iridium is cast, or rolled and forged.

Once I was given a bunch of aluminum pieces that I had to clean for black anodizing (google it).  I found one tiny, thin piece -- the size and thickness of my fingernail, and I asked, "This one too?  Is it aluminum, or steel?  'Cause if its steel, it will be ruined in the anodizing bath."  But no one remembered what the piece was made of.  So I did the Archimedes trick -- determined its volume by how many cc it displaced in a graduated cylinder half full of water, dried it, and weighed it.  I did not get exactly the density of aluminum, but it was way closer to aluminum than steel. 

The Archimedes test only works for things far apart in density.  How far?  Depends on the accuracy you need -- which makes the story all the more important for chemists everywhere.

[billnotgatez]

From
http://www.chemicalforums.com/index.php?page=periodictable

Atomic Weight of Copper: 63.546
Atomic Weight of Silver: 107.868
Atomic Weight of Gold: 196.9665
Atomic Weight of Lead: 207.2

[enahs]

Larger Atomic Weight does not equal larger density.
True large mass is required for larger density (with a set volume), but the volume is also critical.

Gold is denser then Lead, Mercury is also denser the Lead.*

*STP

[pantone159]

Densities (g/cm^3) from Emsley, The Elements, 3rd ed.

Copper - 8.960
Silver - 10.500
Gold - 19.320
Lead - 11.350
Tungsten - 19.300

So lead isn't even close to as dense as gold, but tungsten is right there.  Tungsten, however, was not discovered until 1783 and so not available in Archimedes' time.

[billnotgatez]

I knew we should be using gold bullets.


Unfortunately density is not in the posted periodic table.

[Arkcon]

I knew we should be using gold bullets.

Funny you mention those, in the old TV miniseries "Centennial", an Arapaho chief finds the small flakes of gold in a stream, and with no other use for a shiny golden metal, works it into balls for his rifle.  It's so perfect for the application -- so malleable, that he doesn't even have to melt it like lead, he notices just from some flakes its obvious density, making for better stopping power (what's he going to take down, a North American elephant?)

I wondered, does he need more powder, and can the rifle take the strain?  All questions to ask, but anyway, uranium is only 'bout 1 gram/cc3 lighter than gold, so depleted uranium slugs work just fine as a tank killer, with the added benefit of being pyrophoric.

(Benefit defined on which side of the barrel you're standing, of course)

[billnotgatez]

From
http://www.science.co.il/PTelements.asp?s=Density

No  Wt        Name            Density  Discovery
76  190.23    Osmium     Os   22.6     1803
77  192.217   Iridium    Ir   22.4     1803
78  195.078   Platinum   Pt   21.45    1735
75  186.207   Rhenium    Re   21.04    1925
93  237       Neptunium  Np   20.2     1940
94  244       Plutonium  Pu   19.84    1940
74  183.84    Tungsten   W    19.35    1783
79  196.9665  Gold       Au   19.32    ancient

[Arkcon]

Now from the contemporary list, you see how to short change someone on a solid gold ingot, just hollow it out a fill it with platinum.  Heh.  But platinum wasn't known in Archimedes's time.  It gets its name from the Spanish conquistadors, who panned for gold, and saw "little silver" -- platina.  Honest people tossed it back in to ripen into real silver (not kidding) the dishonest adulterated gold with it.  Problem is, it was hard to melt by the technology of the time.