Osmium-chemistry » Alloys

One osmium compound we have already heard about is osmium tetroxide. Crystalline osmium is not a compound but only a type of crystallization of the pure element, which is non-toxic up to 400 degrees Celsius due to its chemical properties.

It is formed by the reaction of oxidizing agents such as nitric acid on elemental osmium. Osmium tetroxide is a highly volatile solid that has a strong oxidizing effect.

Unlike most oxidizing agents, oxidation with osmium tetroxide can proceed under stereochemical control. Although it is an expensive and toxic compound, osmium tetroxide has some applications.

For example, it is used in forensic fingerprinting. It is also used to enhance the contrast of cell membranes in electron microscopy.

Another type of compound is the complex compounds of osmium. The so-called osmates are derived from the osmium tetroxide just discussed. These are anionic oxygen complexes.

The complex compounds also exist with other ligands, such as ammonia, cyanide, carbon monoxide and nitrogen monoxide. If the ligand is organic in nature (example: cyclopentadiene), an osmocene can be formed. They belong to the group of metallocenes.

Isotopes

Osmium consists of a mixture of seven stable isotopes: osmium-192 with 41 percent, osmium-190 with 26.4 percent, osmium-189 with 16.1 percent, osmium-188 with 13.3 percent, osmium-187 with 1.6 percent, osmium-186 with 1.58 percent and osmium-184 with 0.02 percent.

The only natural radioactive isotope is osmium-186 with a half-life of about two quadrillion years.

In addition, there are 27 short-lived isotopes, of which osmium-194 has the longest half-life of six years.

The ratio of the isotopes osmium-187 to -186 is used in rhenium-osmium chronometers. These are used to determine the age of iron meteorites.