What is a dense, non-toxic metal?

Factual Questions
1

I’m doing what essentially amounts to a science fair project. For various reasons, I need to get my hands on a small (500g - 1000g) sample of a dense metal. It needs to be in a simple geometrical shape (i.e. a cube or a sphere, not a misshapen blob), and non-toxic enough for me and other people to handle safely for a few hours at a time. When I say safe, I mean that we should not have to worry about telling people to wash their hands after touching it.

Any recommendations as to what metal I could use, and where I could get a sample of it? I’ve been thinking about using tungsten, but doing some Google searches I can’t seem to verify that it is indeed safe to handle.

2

Gold is very safe: people even eat it in the form of gold leaf. However, 500 or 1000 g is pretty expensive.

Silver is very safe too, and a lot less expensive, but its density is only about half that of gold.

3

A chunk of solid lead is perfectly safe to handle with your hands. Go to places selling saltwater fishing gear. You can generally buy sinkers up a pound or so, or even lead ingots for making your own sinkers if you have a specific shape you want to cast. If you do melt the lead (which is easy to do) and pour your own, do it in well ventilated, place and do not use a pot that will later be used for cooking.

4

How dense do you need it to be? Iron should be safe and cheap enough.

5

It needs to be as dense as possible.

Astro, I never knew that solid lead isn’t dangerous - are you sure about that?

6

Looking at the tungsten page on the Wooden Periodic Table Table website seems to indicate that it should be safe enough to handle.

7

Sure, Absolute simply needs to crack open a couple thousand lightbulbs, harvest the filaments, put them in a pot and melt them (at 3400 °C) into a simple geometrical shape :wink:
Lead is reasonably safe to pick up and carry around without gloves. If it’s old lead, you’ll want to carefully clean off all the crusty oxides and sulphides. You don’t want those ending up on people’s hands.
Another possibility is Zinc, with a density of 7.1 g/cc or so, you can melt it with a blowtorch, or stove. Modern pennies, while copper clad, are made of an easily melted zinc alloy.

8

Absolute, I have a kilogram cylinder of tungsten I could loan you for shipping cost. Email me at sdmb.5.xj10bt@xoxy.net

9

Paging yoyodyne, please pick up the white courtesy phone.

10

Fear Itself, paging Fear Itself…

11

Tungsten isn’t that far out there (I don’t think??). In a recent thread “Where can I buy a gold brick” or similar (hamsters have me search hamstrung at the moment…) a guy posted a link to a place that sold geometric shapes from tungsten. But I didn’t see a price, might cost as much as a new car.

12

Thanks for the offer, but I wouldn’t be able to give it back.

I saw in your other thread that you have it on your desk - I’m presuming it must be relatively safe, then. You haven’t grown a second head or anything, have you?

13

Here they are now :slight_smile:

14

Not anywhere I can see anyway. I think the biggest danger would be dropping it on your foot.

Duke of Rat, I paid $100/lb for it.

15

Bismuth (right next door to lead on the periodic table) is also good–it’s what they use in non-toxic birdshot and fishing weights. You can probably get a bunch of TINY spheres (i.e., shotgun shell loads) from any gun/ammo dealer.

If you’re looking to melt and cast it into a bigger shape … It melts at 273 C, but a quick look at the literature shows the note “When bismuth is heated in air it burns with a blue flame, forming yellow fumes of the oxide.” So it might well combust before you could melt it. IANAChemist. Be very cautious.

16

Haw-haw. I just thought it was odd that yoyodyne could use his personal knowledge of tungsten twice in 24 hours. No biggie.

17

Here’s a metals (including bismuth) supplier, gleaned from about.com ( http://metals.about.com/od/bismuth/ ):

http://www.aimspecialty.com/

Check out their “fusible alloys” blocks! Pretty neat. You could probably order a block of pure bismuth.

http://www.aimspecialty.com/fusible-alloys.html

18

Thanks! I was curious as to the price. Appreciate the response.

19

Heavy metals in the undivided, solid elemental form do not present a significant health risk, since the route of exposure would be dermal. (OK lead can be intramuscular, intrapleural or intraperitoneal in some cases. <–joke) The dermal route is not a significant means of exposure.

Dusts of these metals vary in toxicity. Some are toxic and irritant dusts.

Here are a summary of toxic effects and BULK metal.
Tantalum - non-toxic 16.6 g/cm[sup]3[/sup] - $0.16US/gram
Tungsten - toxic irritant dust - 19.35 g/cm[sup]3[/sup] - $0.02US/g
Rhenium - non-toxic - density 20.53 g/cm[sup]3[/sup] - $1.40US/g
Osmium - forms very toxic oxide - 22.48 g/cm[sup]3[/sup] - $100 /g
Iridium - irritant - 22.42 g/cm[sup]3[/sup] $17US/ g
Platinum - irritant - 21.45 g/cm[sup]3[/sup] - $31US/g
Gold - non-toxic - 18.88 g/cm[sup]3[/sup] - $15US/g
Ruthenium - irritant - 12.30 g/cm[sup]3[/sup] - 2.14US/g Rhodium - irritant - 12.4 g/cm[sup]3[/sup] - ?US/g expensive
Lead - toxic dust - 11.34 g/cm[sup]3[/sup] - $0.001US/g

Tungsten looks like a good choice, but rhenium or tantalum would be nice if you had the $$$. You could probably pick up a kilo of Ta for < $500US

20

I was just yankin your chain :wink: