The element osmium is detected via its compound osmium tetroxide. Although the detection reaction is specific, it is not recommended due to toxicity.

The test solution containing osmium is dropped onto a filter paper that has previously been moistened with a benzidine or potassium ferricyanide solution. If the benzidine solution was used, the filter paper turns purple. In the case of the potassium ferricyanide solution, a light green coloration occurs.

Nowadays, however, more and more instrumental techniques are being used. Examples are atomic spectrometry, neutron activation analysis and voltametry. With the aid of these methods, more precise determinations are possible.

The extraction of osmium is very complex and usually takes place during the processing of other metals, such as platinum or gold.

Educt for osmium extraction is mostly excavation via platinum mining, but also the anode slime from gold or nickel production. The anode slime is dissolved in aqua regia, which causes platinum and gold to dissolve. The other platinum metals and silver remain.

The silver forms insoluble silver chloride, which can be separated using nitric acid and lead carbonate. It is then melted with sodium bicarbonate and leached out.

Rhodium is dissolved as rhodium sulfate and removed. The residue is melted down together with sodium peroxide, resulting in ruthenium and osmium going into solution. Iridium remains in the insoluble residue.

Chlorine is added to the solution. This produces the volatile substances osmium tetroxide and ruthenium tetroxide.

After the addition of alcoholic sodium hydroxide solution, only osmium tetroxide goes into solution and can thus be separated from the ruthenium tetroxide.

To obtain elemental osmium, it is precipitated with ammonium chloride as a complex.

Finally, it is reduced with hydrogen to metallic osmium.

OsO₂(NH₃)₄Cl₂ + 3 H₂ → Os + 4 NH₄⁺ + 2 Cl^- + 2 OH^-

Osmium is in the sixth transition group in the periodic table. Within this group we find it in the sixth period.

Osmium has the atomic number 76 and an atomic mass of 190.23 u. Its electron configuration is [Xe] 4f¹⁴ 5d⁶ 6s².

Osmium is non-toxic in its crystalline form as long as a temperature of 400 °C is not exceeded. It can be processed or crystallized under inert gas.

Osmium is a blue-white shiny, dense and hard metal that is difficult to process.

It is the hardest of the platinum metals and has the highest density of elements in the periodic table at 22.61 g/cm³.

The crystal structure of osmium is the hexagonal densest sphere packing.

Osmium is a precious metal and therefore not reactive.

It reacts directly only with chlorine, fluorine and oxygen.

If osmium is in a compact form, it is resistant to non-oxidizing acids in water and air.

Finely spread out osmium or osmium on surfaces of fused beads or sintered bars slowly oxidizes to osmium VIII oxide. The name of the compound is osmium tetraoxide, which is harmful to mucous membranes and eyes.

Os + 2O₂ → OsO₄  

After rhenium and tungsten, osmium has the highest melting point of all metals at 3,033 °C.

Its boiling point is over 5000 degrees Celsius. This temperature corresponds to the prevailing conditions in the corona of the sun.

At lower temperatures, osmium becomes a superconductor.

Furthermore, osmium has the largest compressive modulus of all elements.

With a value of 462 gigapascals, it even surpasses diamonds.

The same applies to its abrasion resistance, which is also of this extreme value in nature.

One osmium compound is osmium tetroxide. 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.

Crystalline osmium is not a new compound but only a crystallization type of the pure element, which is non-toxic up to 400 °C due to its chemical properties. The rearrangement of the crystal structure can be compared with the processing of carbon to diamonds, although it is many times more complex and expensive.

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 where it is used in the milligram range.

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

Some other types of compounds are the complex compounds of osmium. The so-called osmates are derived from osmium tetroxide. 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, an osmcen can be formed.

Osmium organochemistry, which is still in its infancy but is developing quickly, could become interesting.