# Is there a compound denser than the densest element?

I'm musing about how to give students an intuitive feeling about density by letting them lift a same sized volume of different materials, e.g. 1 liter of water, a $10 {\times} 10 {\times} 10 \, \mathrm{cm}^3$ cube of iron, lead etc. So far, the densest material accessible and affordable to a teacher would probably be mercury (I certainly remember my chemistry teacher letting us lift a small bottle, maybe $100 \, \mathrm{mL}$, makes for an unforgettable impression).

Do I have any chance of getting anywhere above the $13 \frac{\mathrm{g}}{\mathrm{cm}^3}$ of mercury? I sorted the elements in the Wikipedia Density article. Gold and Platinum require to win the lottery first. A liter of Plutonium needs connections to evil people, plus a lot of safety measures, so is right out :-) Osmium? Rhenium?

Are there elements or compounds denser than mercury usable for a demonstration? Are there heavy metal compounds that can be denser than the metal itself or is there a physical constraint prohibiting such a property? (I don't want to look at the far ends of a $p$/$T$ phase diagram, standard temperature and pressure is okay).

• I would use tungsten, although it is very expensive. I would go to a stockist and explain the situation - they may let you borrow some as you will do well to break there slab of Tungsten... – MoonKnight Apr 4 '13 at 13:55
• Tungsten has a specific gravity of about 19 and is now used in some men's jewelry. In nuclear and particle physics collimators and absorbers are sometimes made of "heavymet" which seems to be a generic name for tungsten--other stuff alloys which are heavier than pure tungsten (but cheaper than iridium and osmium and easier to machine than pure tungsten). The exact composition seems to vary from source to source. The collimators used in JLAB HallC while I was doing my dissertation work there were 90% W 10% CuNi and had a specific gravity of 17. – dmckee Apr 4 '13 at 13:56
• Off topic, but you might want to include a bottle of dry cleaning fluid. In a sealed bottle this looks much like water but has a density 60% greater. It feels quite uncanny to handle because you don't expect it to weigh as much as it does. – John Rennie Apr 4 '13 at 14:50
• I have two practical concerns. If you use the same volume for everything, 1 L of iron is going to be 17 pounds. That might be okay, but the mercury will weight 30 pounds, and the tungsten will weigh 42 pounds. My other concern is cost and safety: that much mercury looks like it will cost about $8000, even if they'll sell you that much. And I don't know how to safely handle that much. – Colin McFaul Apr 4 '13 at 15:48 • You may also buy tantalum - denser than mercury - for$185 per pound, metalprices.com/p/TantalumFreeChart – Luboš Motl Apr 4 '13 at 16:26

Here is a table I made for you listing the elements with a density higher than $10 \frac{\mathrm{g}}{\mathrm{cm}^3}$ and their approximate price per kg:

I couldn't find any prices for Einsteinium or Actinium and some of the other prices might come from poor sources, but take it as a rough guide.

Now you only have to figure out how much you need and your budgetetary constraints, and choose the densest you can afford. As I have learned from the political debate in the US, teachers are apparently raking in big cash, so I suggest you go with osmium or rhenium.

Note: Some of these might be unsuitable/infeasible for other reasons than their price.

• BTW, how could find prices for things like Californium, Berkelium or Curium? – MyUserIsThis Apr 4 '13 at 20:04
• @MyUserIsThis For the ones I couldn't find on commodity market sites I just googled "price of X" and tried to find a rough consensum among at least a couple of sites that seemed fairly legit. That worked quite well for most of them. – jkej Apr 4 '13 at 22:02
• @MyUserIsThis With the right licensing (which varies from country to country) you can call a supplier and order the stuff. In the US the suppliers get them from the government who separated them as part of nuclear bomb making activities. Of course, I have never even talked to anyone who used those materials in quantities that you would express in grams, much less kilograms. I've always been interested in the price per millicurie. You can get nanocuries of many radio-nuclei (including transuranic isotopes) without a license. That's enough for demos. – dmckee Apr 4 '13 at 22:03
• @jkej can you please point me to somewhere that I can buy tungsten for anywhere near \$35 per kg? I need to buy some quantity and I have not found it lower than \$100 per kg – themirror Aug 12 '13 at 6:55
• As a rejected edit noted, osmium forms toxic osmium tetroxide when exposed to the oxygen in air (ref wikipedia). Do not suggest it!!! – Art Brown May 7 '14 at 1:47

There is a rather lovely looking set of spheres available now through an indiegogo campaign - these are 1 kg objects of different densities. It is a more visual way of driving home the message that you wanted to show with your demonstration:

At $890 for the set it is beautiful, but rather expensive for a science demonstration - more something for a CEO's corner office. However, there is a set of "density cubes" you can buy on Amazon - probably more in line with what you are looking for. It is sold by Midwest Tungsten Service (in case the Amazon link rots). Here, the volume is constant but the different densities make it interesting. Note - the title says "Tungsten carbide" (density$\rm{15.6~ g/cm^3}$) but the engraving suggests "tungsten" (density$19.3 ~\rm{g/cm^3}$). At$130 for the set it is less out-of-reach.

DISCLAIMER: I have no relationship to either of these vendors and am providing the links purely as a convenience to people visiting this site. These links may not last...

I'm not sure if you want to stray from the 1 liter amount or not but searching via Amazon it seems there is a company selling spheres of quite a few different metals. They have tungsten, steel, brass, chromium, etc.

See here and here

• The amount is not set in stone, but if I could get the range of weights from "I can pitch it like a baseball" to "crushes my toes when dropped"...5kg total? At 20g/cm^3 that would be 1/4 liter. – Jens Apr 5 '13 at 7:23

## protected by Qmechanic♦Feb 19 '14 at 1:03

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