Osmium tetroxide
Osmium (VIII ) Oxide
Colorless monoclinic needles
Fixed
4.91 g · cm -3
40 ° C.
130 ° C.
10 hPa ( 20 ° C)
- Moderately in water ( 65 g · l -1)
- Well in many organic solvents such as carbon tetrachloride, ethanol, diethyl ether and benzene
Risk
Not set
15 mg · kg -1 ( LD50, rat, oral)
Template: Infobox chemical / molecular formula search is not possible
Osmium tetroxide (also osmium (VIII ) oxide, osmic acid ), the osmium oxide of the element in its highest oxidation state ( 8).
Representation and extraction
Osmium (VIII ) oxide is prepared by oxidation of osmium by Osmiumlösungen with nitric acid or sodium peroxodisulfate in sulfuric acid. Because of the volatility and toxicity occurs in ampoules sealed in the trade.
Properties
Osmium (VIII ) oxide formed pale yellow crystals having a very low melting point of 40 ° C and a boiling point of 130 ° C. It sublimes at room temperature already. This compound has a penetrating ozone- like odor (Greek osmos = smell) is what inspired the name for the metal osmium. Osmium (VIII ) oxide is very volatile and very toxic; it is readily reduced by organic compounds to a black osmium ( IV) oxide. It dissolves only to a small extent in water, but very good in carbon tetrachloride CCl4. The strong oxidizing agent reacts with the reducing and combustible material.
Osmium (VIII ) oxide having a monoclinic crystal structure with space group C2 (a = 866 pm, 452 pm b = c = 475 pm, β = 117 ° 54 ').
Use
In transmission electron microscopy, it is used as a contrast agent for staining a biological material.
In organic synthesis may be used to oxidize olefins to diols ( dihydroxylation ). Stereoselectively produced a diol with cis- OH groups. Since the reagent is very expensive and toxic, and which reaction conditions have now been improved so as osmium (VIII ) oxide in small quantities as a catalyst is required, while hydrogen peroxide or N-methylmorpholine- N-oxide acting as an oxidizing agent.
Others
On 6 April 2004, the American news agency reported ABC News that the British intelligence believed to have foiled a bomb attack using this substance. Other sources doubt this representation, since osmium (VIII ) oxide is too expensive despite its high damage potential for use as a poison gas.
On May 27, 2011, an accident at the University Hospital Magdeburg, in which an employee of a bottle with osmium tetroxide fell occurred. The entire house one had to be evacuated. However, no persons were injured.