Osmium
The osmium is the chemical element periodic Tableau whose symbol is Os and the Atomic number 76 . It is appeared as a bluish gray metal and brilliance. It is a Métal of transition pertaining to the Métaux from the group of platinum. It is with the Iridium the natural elements densest on Earth. It is generally found nativement in Alliage with the Platine or iridium. The osmium alloys are employed in particular in the points of pen plucks, the electrical contacts and in other applications where its hardness and its resistance extremes are necessary.
Characteristics
Pure osmium in its metal form is extremely Dense, breaking and of a bluish gray shining even at high temperature, but appears very difficult to obtain. The osmium powder is easier to make, but this one forms Tétroxyde of osmium (Os O), a powerful agent Oxydant and very poison in contact with the air.Because of its high density, osmium is generally regarded as the known heaviest elements natural, very slightly less less heavy than iridium. However, calculations of density since space will be able to produce more reliable results and precis that those current, which are of: 22610 kg/m {{3}} for osmium against: 22650 kg/m for iridium. Their final classification is thus not possible for the moment.
Lastly, this metal at the highest melting point and more low pressure of vapor of the family of platinum. Its states of oxidation are generally +4 and +3, but the states going from +1 to +8 were observed.
Applications
Because of the extreme toxicity of its oxide, osmium is seldom used in its pure state but in the form of alloy with other metals. Those are very hard and, with other metals of the group of platinum, are employed in the points of pen feathers, the needles of gramophones, the pivots of instruments and the electrical contacts.
The alloy of 10 % of osmium and 90 % of platinum is used for the surgical implants like the Pacemaker S and the pulmonary replacements of valves.
The Tétroxyde of osmium was used inter alia in the detection of the digital fingerprints. It is also used as catalyst in organic chemistry.
The isotopic couple Re187/Os187 was used by the team of C. - J. Lively in the years 1970 to date the age from the aggregation of the ground with: 4600 million years.
History
Greek osme which means “odor”, osmium was discovered in 1803 by Smithson Holding with London, England, with iridium in the residues of the dissolution of platinum in Eau levels.
Occurrence
This metal of transition is found in iridiosmium, a natural alloy of Iridium and osmium, and in sands containing of the platinum which one finds in the rivers of the mountains of the the Ural, of the north and the south of the America. It also appears in the nickel ore which one finds mixed with other metals of the family of platinums with Sudbury, in the Ontario. Even if the quantity of these metals found in these ores is weak, the great volume of ore allows an economic profitability.
Composed
OsO: Tetroxide of osmium or tétraoxyde of osmium .
Isotopes
Osmium has seven Isotope S natural, of which five are stable: 187 Os, it 188 Os, it 189 Os, it 190 Os and it 192 Os (more running). 184 Os and it 186 Os have extremely long Demi-vie S and can be regarded as stable also.
187 Os is the son of the Rhénium -187 (half-life 4,56x10 10 years). The Report/ratio 187 Os 186 Os, like the report/ratio 187 Re/ 187 Os, was intensely used to date from the grounds or the meteoritic rocks . However, the most notable application of osmium in the dating was in conjunction with iridium to analyze the layer of Quartz shocked of the Limite K-T which marks the extinction of the Dinosaure S there is 65 million years.
Toxicity, ecotoxicity, risks
The Tétroxyde of osmium is extremely toxic. Concentrations in the air of 10 −7 G/m {{3}} can cause the congestion of the lungs and the damage on the skin and with the eyes.
See too
- Metals of the group of platinum
External bonds
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