General Description
A colorless or yellow solid with a pungent odor of chlorine. Melting point about 104°F. Boiling point 266°F (begins to sublime below melting point). Density 4.9 g/cm3. Soluble in alcohol. Toxic by inhalation and a strong irritant to the eyes and mucous membranes.
Reactivity Profile
OSMIUM TETROXIDE(20816-12-0) is incompatible with hydrochloric acid andeasily oxidized organic materials. Contact with other materials may cause fire. . Reacted explosively with1-methylimidazole [J. Chem. Soc., Dalton Trans., 1979, 1084].
Air & Water Reactions
Soluble in water.
Health Hazard
TOXIC; inhalation, ingestion or skin contact with material may cause severe injury or death. Contact with molten substance may cause severe burns to skin and eyes. Avoid any skin contact. Effects of contact or inhalation may be delayed. Fire may produce irritating, corrosive and/or toxic gases. Runoff from fire control or dilution water may be corrosive and/or toxic and cause pollution.
Potential Exposure
Osmium may be alloyed with platinum
metals, iron, cobalt, and nickel; and it forms compounds
withtin and zinc. The alloy with iridium is used in
the manufacture of fountain pen points, engraving tool;
record player needles; electrical contacts; compass needles;
fine machine bearings; and parts for watch and
lock mechanisms. The metal is a catalyst in the synthesis
of ammonia; and in the dehydrogenation of organic compounds. It is also used as a stain for histological
examination of tissues. Osmium tetroxide is used as an
oxidizing agent, catalyst, and as a fixative for tissues in
electron microscopy. Other osmium compounds find use
in photography. Osmium no longer is used in incandescent
lights or in fingerprinting.
Fire Hazard
Non-combustible, substance itself does not burn but may decompose upon heating to produce corrosive and/or toxic fumes. Some are oxidizers and may ignite combustibles (wood, paper, oil, clothing, etc.). Contact with metals may evolve flammable hydrogen gas. Containers may explode when heated.
First aid
Move victim to fresh air. Call 911 or emergency
medical service. Give artificial respiration if victim is not
breathing. Do not use mouth-to-mouth methods if victim
ingested or inhaled the substance; give artificial respiration
with the aid of a pocket mask equipped with a one-way valve
or other proper respiratory medical device? Administer oxygen
if breathing is difficult. Remove and isolate contaminated
clothing and shoes. In the case of contact with substance,
immediately flush skin or eyes with running water for at least
20 minutes. For minor skin contact, avoid spreading material
on unaffected skin. Keep victim warm and quiet. Effects of
exposure (inhalation, ingestion, or skin contact) to substance
may be delayed. Ensure that medical personnel are aware of
the material(s) involved and take precautions to protect themselves.
Medical observation is recommended for
2448 hours after breathing overexposure, as pulmonary
edema may be delayed. As first aid for pulmonary edema, a
doctor or authorized paramedic may consider administering a
drug or other inhalation therapy.
Incompatibilities
Osmium tetroxide is a strong oxidizer.
Reacts with combustibles and reducing materials. Reacts
with hydrochloric acid to form toxic chlorine gas. Forms
unstable compounds with alkalis.
Chemical Properties
Osmium is a blue-white metal. It is found in
platinum ores and in the naturally occurring alloy osmiridium.
Osmium when heated in air or when the finely
divided form is exposed to air at room temperature, oxidizes
to form the tetroxide (OsO4), osmic acid. Osmium
tetraoxide is a colorless, crystalline solid or pale-yellow
mass. Unpleasant, acrid, chlorine-like odor. A liquid above
41°C.
Chemical Properties
Osmium tetroxide is a strong oxidant. Numerous organic
substances reduce it to black osmium dioxide (OsO2) or to
osmium metal.
Chemical Properties
solid with an unpleasant odour
Waste Disposal
Consult with environmental
regulatory agencies for guidance on acceptable disposal
practices. Generators of waste containing this contaminant
(≥100 kg/mo) must conform with EPA regulations
governing storage, transportation, treatment, and waste
disposal.
Physical properties
Pale, yellow crystalline solid; chlorine-like acrid odor; monoclinic crystals having terahedral structure; density 5.1 g/cm3; melts at 40.6°C; vaporizes at 129.7°C; sublimation begins below its boiling point; vapor pressure 11 torr at 27°C; critical temperature 405°C; critical pressure 170 atm; moderately soluble in water, 7.24 g/100mL at 25°C; soluble in most organic solvents.
Uses
Osmium (VIII) tetraoxide (Os8+ + 4O2-→ OsO4) is a yellow crystal and probably the most
important compound used as an oxidizing agent, as a biological stain in microscopy, and to
detect fingerprints.
Uses
Osmium tetroxide is used in histopathological laboratories
to stain the adipose tissue and as a stabilizing agent in
scanning electron microscopy. In the chemical
industry, it is used as a catalyst in the organic synthesis,
particularly as the oxidizing agent in olefin-to-glycol conversion
(546, 567). In the past, osmium tetroxide in the form
of aqueous solution was used in forensic medicine to examine
fingerprints. Osmium tetroxide is also used in
medicine to treat rheumatoid arthritis.
Uses
Oxidizing agent, particularly for converting olefins to glycols. Catalyzes chlorate, peroxide, periodate, and other oxidations: P. N. Rylander, Organic Syntheses with Noble Metal Catalysts (Academic Press, New York, 1973) pp 121-144. As fixing and staining agent for cell and tissue studies.
Definition
ChEBI: An osmium coordination entity consisting of four oxygen atoms bound to a central osmium atom via covalent double bonds.
Preparation
Osmium tetroxide is obtained as an intermediate during recovery of osmium metal from osmiridium or other noble metal minerals (See Osmium). In general, oxidation of an aqueous solution of an osmium salt or complex, such as sodium osmate with nitric acid, yields the volatile tetroxide which may be distilled out from the solution. In the laboratory, the compound can be prepared by oxidation of the osmium tetrachloride, OsCl4, or other halide solutions with sodium hypochlorite followed by distillation.
Osmium tetroxide may also be produced by heating finely divided osmium metal in a stream of oxygen or air at 300 to 400°C.
Production Methods
Osmium tetroxide is obtained by heating, at 300–400°C,
finely divided osmium metal in the stream of air or oxygen
(546). Commercially, it is received during osmium
smelting and platinum annealing. Osmium tetroxide
may also be produced by oxidizing osmium with aqua regia
or nitric acid. It is often formed at room temperature
from osmium metal powder.
Hazard
Osmium tetroxide is poisonous by all routes of exposure. The vapor is an eye irritant and can produce tears and damage. The vapor also can cause upper respiratory tract irritation.
LD50 oral (mouse): 162 mg/kg
LCLO inhalation (mouse): 40 ppm (104 mg/m 3)/4 hr.
Flammability and Explosibility
Noncombustible
storage
In
particular, all work with osmium tetroxide should be conducted in a fume hood to
prevent exposure by inhalation, and splash goggles and impermeable gloves should
be worn at all times to prevent eye and skin contact. Osmium tetroxide as solid or
solutions should be stored in tightly sealed containers, and these should be placed in
secondary containers.
Purification Methods
It is VERY TOXIC and should be manipulated in a very efficient fume cupboard. It attacks the eyes severely (use also face protection) and is a good oxidising agent. It is volatile and has a high vapour pressure (11mm) at room temperature. It sublimes and volatilises well below its boiling point. It is soluble in *C6H6, H2O (7.24% at 25o), CCl4 (375% at 25o), EtOH and Et2O. It is estimated by dissolving a sample in a glass-stoppered flask containing 25mL of a solution of KI (previously saturated with CO2) and acidified with 0.35M HCl. After gentle shaking in the dark for 30minutes, the solution is diluted to 200mL with distilled H2O saturated with CO2 and titrated with standard thiosulfate using starch as indicator. This method is not as good as the gravimetric method. Hydrazine hydrochloride (0.1 to 0.3g) is dissolved in 3M HCl (10mL) in a glass-stoppered bottle. After warming to 55-65o, a weighed sample of OsO4 solution is introduced, and the mixture is digested on a water bath for 1hour. The mixture is transferred to a weighed glazed crucible and evaporated to dryness on a hot plate. A stream of H2 is started through the crucible, and the crucible is heated over a burner for 20-30minutes. The stream of H2 is continued until the crucible in cooled to room temperature, and then the H2 is displaced by CO2 in order to avoid rapid combustion of H2. Finally the crucible is weighed. [Grube in Handbook of Preparative Inorganic Chemistry (Ed. Brauer) Academic Press Vol II pp 1603 1965, Anderson & Yost J Am Chem Soc 60 1822 1938.] § Available commercially on a polymer support.