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7440-04-2

Name OSMIUM
CAS 7440-04-2
EINECS(EC#) 231-114-0
Molecular Formula Os
MDL Number MFCD00011147
Molecular Weight 190.23
MOL File 7440-04-2.mol

Chemical Properties

Appearance 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.
Melting point  3045 °C(lit.)
Boiling point  5027 °C(lit.)
density  22,48 g/cm3
solubility  soluble in aqua regia
form  sponge
color  Black
Specific Gravity 22.48
Water Solubility  attacked by aqua regia; barely affected by HCl, H2SO4 [MER06]
Merck  13,6960
Exposure limits ACGIH: Ceiling 2 ppm
OSHA: Ceiling 5 ppm(7 mg/m3)
NIOSH: IDLH 50 ppm; Ceiling 5 ppm(7 mg/m3)
History Discovered in 1803 by Tennant in the residue left when crude platinum is dissolved by aqua regia. Osmium occurs in iridosmine and in platinum-bearing river sands of the Urals, North America, and South America. It is also found in the nickel-bearing ores of the Sudbury, Ontario, region along with other platinum metals. While the quantity of platinum metals in these ores is very small, the large tonnages of nickel ores processed make commercial recovery possible. The metal is lustrous, bluish white, extremely hard, and brittle even at high temperatures. It has the highest melting point and the lowest vapor pressure of the platinum group. The metal is very difficult to fabricate, but the powder can be sintered in a hydrogen atmosphere at a temperature of 2000°C. The solid metal is not affected by air at room temperature, but the powdered or spongy metal slowly gives off osmium tetroxide, which is a powerful oxidizing agent and has a strong smell. The tetroxide is highly toxic, and boils at 130°C (760 mm). Concentrations in air as low as 10–7 g/m3 can cause lung congestion, skin damage, or eye damage. The tetroxide has been used to detect fingerprints and to stain fatty tissue for microscope slides. The metal is almost entirely used to produce very hard alloys, with other metals of the platinum group, for fountain pen tips, instrument pivots, phonograph needles, and electrical contacts. The price of 99.9% pure osmium powder — the form usually supplied commercially — is about $100/g, depending on quantity and supplier. Natural osmium contains seven isotopes, one of which, 186Os, is radioactive with a very long half-life. Thirty-four other isotopes and isomers are known, all of which are radioactive. The measured densities of iridium and osmium seem to indicate that osmium is slightly more dense than iridium, so osmium has generally been credited with being the heaviest known element. Calculations of the density from the space lattice, which may be more reliable for these elements than actual measurements, however, give a density of 22.65 for iridium compared to 22.61 for osmium. At present, therefore, we know either iridium or osmium is the heaviest element, but the data do not allow selection between the two.
CAS DataBase Reference 7440-04-2(CAS DataBase Reference)
EPA Substance Registry System Osmium (7440-04-2)

Safety Data

Hazard Codes  F,Xi
Risk Statements 
R11:Highly Flammable.
R37/38:Irritating to respiratory system and skin .
R41:Risk of serious damage to eyes.
R36/38:Irritating to eyes and skin .
Safety Statements 
S16:Keep away from sources of ignition-No smoking .
S26:In case of contact with eyes, rinse immediately with plenty of water and seek medical advice .
S36/37/39:Wear suitable protective clothing, gloves and eye/face protection .
RIDADR  UN 3089 4.1/PG 2
WGK Germany  -
RTECS  RN1100000
TSCA  Yes
HazardClass  4.1
PackingGroup  II
HS Code  71104100
Safety Profile
Poison by intravenous route. An irritant to eyes and mucous membranes. The principal effects of exposure are ocular disturbances and an asthmatic condition caused by inhalation. Furthermore, it causes dermatitis and ulceration of the skin upon contact. When osmium is heated, it gives off a pungent, poisonous fume of osmium tetroxide. One case of osmium poisoning reported in the literature resulted from the inhalation of osmium, which gave rise to a capillary bronchitis and dermatitis. The tetroxide vapor has a pronounced and nauseating odor that should be taken as a warning of a possibly toxic concentration in the atmosphere, and personnel should immedately move to an area of fresh air. The metal itself is not highly toxic. Flammable in the form of dust when exposed to heat or flame. Slight explosion hazard in the form of dust when exposed to heat or flame. Violent reaction or ignition with chlorine trichloride or oxygen dfluoride. Ignites when heated to l00℃ with fluorine. Incandescent reaction in phosphorus vapor. When heated to decomposition it emits toxic fumes of 0s04. See also OSMIUM TETROXIDE
Hazardous Substances Data 7440-04-2(Hazardous Substances Data)
Toxicity
LDLo ivn-dog: 17 mg/kg SMSJAR 26,131,1826

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