Place a 10-centimeter cube of osmium on your palm and your hand would collapse under the weight — over 22 kilograms. Osmium is the densest naturally occurring substance on Earth. Denser than gold, lead, and even uranium. Its atoms are packed as tightly as the laws of physics allow.
But there is a catch: osmium slowly oxidizes in air and forms tetroxide — OsO₄. This stuff has a sharp chlorine-like smell and terrifying toxicity. Even a microscopic amount of vapor can temporarily blind a person. In fact, the name 'osmium' comes from the Greek word 'osme' — meaning smell.
Osmium is a bluish-white metal belonging to the platinum group. English chemist Smithson Tennant discovered it in 1803 while dissolving platinum ore in aqua regia. The residue that refused to dissolve turned out to be a mixture of two new elements — osmium and iridium.
This metal is extraordinarily hard and brittle. Working with it is a nightmare: it cannot be forged, rolled, or bent without shattering. But in alloys, osmium makes other metals incredibly wear-resistant. Premium fountain pen nibs used to be tipped with osmium-iridium — they wrote for decades without replacement.
WARNING: osmium tetroxide (OsO₄) is an extremely hazardous substance! Even micrograms of its vapor irritate the eyes, mucous membranes, and lungs. It can cause temporary blindness. Metallic osmium is safer, but when heated in air it forms toxic OsO₄. Work with osmium only in a fume hood with full protective equipment. Store in sealed, airtight containers.
Osmium's density is 22.59 g/cm³ — a record among natural elements. A 10×10×10 cm cube would weigh as much as three full buckets of water.
Osmium tetroxide (OsO₄) is so toxic that even microscopic amounts of its vapor can cause temporary blindness and lung damage.
The name 'osmium' comes from the Greek 'osme' — meaning smell. When the metal dissolves, it releases OsO₄ with a sharp, unpleasant chlorine-like odor.
Osmium and iridium were discovered simultaneously in 1803 by Smithson Tennant. Both were hiding in the insoluble residue of platinum ore.
Osmium is so hard and brittle that it is virtually impossible to machine. It cannot be forged or rolled — only powder metallurgy makes it workable.
The isotope ¹⁸⁶Os decays with a half-life of 2×10¹⁵ years — that is 100,000 times longer than the age of the universe. Practically eternal.
| Isotope | Mass (u) | Abundance | Half-life | Decay |
|---|---|---|---|---|
184Os | 183.952489 | 0.02% | stable | — |
186Os☢ | 185.953838 | 1.59% | 2×10¹⁵ years | α |
187Os | 186.955750 | 1.96% | stable | — |
188Os | 187.955838 | 13.24% | stable | — |
189Os | 188.958147 | 16.15% | stable | — |
190Os | 189.958447 | 26.26% | stable | — |
192Os | 191.961481 | 40.78% | stable | — |
Analysis of platinum ore residue