Setting the osmium record straight

[JoeLS]

Osmium is the strangest and rarest of the platinum group metals, and if you look it up online you’ll find a lot of information. Unfortunately much of this information is false. This is partly due to one company (which I won’t name) that is attempting to corner the osmium market, and convince the world that only its osmium (which it is selling for about $48,000/oz) is safe to handle. Below is a list of facts about osmium that have been obscured by intentional or unintentional misinformation:

1.Osmium tetroxide (OsO₄) is toxic. Exactly how toxic is uncertain as there have been very few cases of OsO₄ poisoning, and only one death, since the early 19^th century. The main non-lethal effect is temporary blindness. It is not something to play around with. OsO₄ must be handled with extreme care because its low boiling point (129°C) means that it has a high vapor pressure at room temperature, allowing it to drift through air far from its source.

2. Osmium powder reacts with at room temperature to form OsO₄. The reaction is slow, so it would take a relatively large amount of powder, or a long exposure to air, to create a dangerous concentration of OsO₄. Nevertheless osmium powder should be handled with great care and stored in an oxygen-free environment. Sealing it in a mason jar with a desiccant and a new chemical hand warmer works well. The hand warmer scavenges all the oxygen, creating a partial vacuum that keeps the lid securely sealed. I’ve stored Os powder for years in this way without a hint of oxidation.

3. While osmium powder oxidizes, large pieces of osmium formed by melting or high quality sintering do not oxidize at terrestrial temperatures. The reason for this is not completely known, but it most likely involves the lack of reactive, high free energy crystal edges and corners in the larger pieces.

4. It is true, as a certain company claims, that only crystalline osmium is safe to handle, but this is meaningless as all forms of osmium, from powder to large ingots, are crystalline.

5. Large (mm scale or larger) pieces of fused osmium are as safe to handle as any platinum group metal.

6. Except for its tendency to oxidize, osmium is extremely non-reactive. Osmium metal per se does not appear to be toxic.

7. It is not illegal to own osmium.

8. No company has the exclusive right to buy osmium.