iridium


Also found in: Dictionary, Thesaurus, Medical, Financial, Acronyms, Wikipedia.

iridium

(ĭrĭd`ēəm), metallic chemical element; symbol Ir; at. no. 77; at. wt. 192.217; m.p. about 2,410°C;; b.p. about 4,130°C;; sp. gr. 22.55 at 20°C;; valence +3 or +4. Iridium is a very hard, usually brittle, extremely corrosion-resistant silver-white metal with a face-centered cubic crystalline structure. It falls between platinum and osmium in Group 9 of the periodic tableperiodic table,
chart of the elements arranged according to the periodic law discovered by Dmitri I. Mendeleev and revised by Henry G. J. Moseley. In the periodic table the elements are arranged in columns and rows according to increasing atomic number (see the table entitled
..... Click the link for more information.
. It is not certain whether osmium or iridium is the most dense element. Iridium is found uncombined in nature as the metal and in combination with osmium and platinum. It is obtained commercially from osmiridium, a byproduct of platinum production. The metal is used in pivot bearings and in scientific and other special equipment, such as surgical tools. It is also used in making chemical crucibles. Iridium is used principally in alloys. An alloy with osmium is used to make fountain-pen nibs. Alloys with platinum are used in heavy-duty electrical contacts. An alloy of 10 parts iridium with 90 parts platinum is used in the international kilogram standard in Paris. Formerly the international meter standard was the distance between two marks on a bar made of that same alloy; it is now based on the wavelength of a line in the spectrum of an isotope of krypton. Iridium is chemically very unreactive. Pure iridium metal is not attacked by acids or acid mixtures, not even by aqua regia, which dissolves gold. Fluorine and chlorine attack it only at a red heat. It is oxidized slowly at high temperatures. It resists attack by fused bases and by most molten metals. Iridium was discovered in 1804 by Smithson Tennant; it is so named because of its various highly colored salts.

Iridium

 

Ir, a chemical element of group VIII of Mendeleev’s periodic system. Atomic number, 77; atomic weight, 192.22.

Iridium belongs to the platinum group of metals. In nature it is represented by two stable isotopes,191Ir (38.5 percent) and193Ir (61.5 percent). The element was discovered in 1804 by the British chemist S. Tennant (1761–1815) and named iridium (from the Greek iris, rainbow) because of the varied colors of its salts. Iridium is rare in the earth’s crust (1 X 10−7 percent by weight), occurring mainly together with platinum. A silver-white metal, it is very hard and extremely refractory and has high chemical stability. It is included with the other metals of the platinum group, as well as with gold and silver, among the noble metals because of the above properties.

iridium

[i′rid·ē·əm]
(chemistry)
A metallic element, symbol Ir, atomic number 77, atomic weight 192.2, in the platinum group; insoluble in acids, melting at 2454°C.
(metallurgy)
A silver-white, brittle, hard metal used in jewelry, electric contacts, electrodes, resistance wires, and pen tips.

iridium

a very hard inert yellowish-white transition element that is the most corrosion-resistant metal known. It occurs in platinum ores and is used as an alloy with platinum. Symbol: Ir; atomic no.: 77; atomic wt.: 192.22; valency: 3 or 4; relative density: 22.42; melting pt.: 2447?C; boiling pt.: 4428?C

Iridium

(Iridium Satellite LLC, Bethesda, MD, www.iridium.com) A phone and pager service that provides global coverage using handheld phones and low-earth orbit (LEO) satellites. Data access is available at 2.4 Kbps and Internet access at 10 Kbps. Announced in 1990 and completed in 1998 at a cost of USD $6 billion, Iridium was the first global satellite phone service. It originally used cellular partners to provide standard cellphone service when satellites were not required. Iridium LLC went into Chapter 11 in August 1999, and in late 2000, Iridium Satellite LLC was formed to resurrect the system. See LEO and Globalstar.
References in periodicals archive ?
Iridium AxcessPoint Connect will be available to Iridium customers later this year via the company's website at www.
Iridium also plans to selectively expand its network of more than 235+ global distribution partners by adding new service providers in the Russian market.
Since Iridium began transmitting last year, the VLA has discontinued all observations at 1612 MHz.
Iridium Satellite can be found on the World Wide Web at http://www.
Ancient organisms may complicate the job of interpreting the iridium record, the scientists conclude.
Since Desert Storm, we've had an unsatisfied requirement for C2 OTM (command and control on-the-move) and no material solution to date has had such great potential in filling that requirement across such a broad spectrum as Netted Iridium does," said U.
Iridium intends to offer this service in the United States, the District of Columbia, Puerto Rico, the U.
The feedback from beta test platforms has been overwhelmingly positive, and we have a strong backlog of orders from shipowners who recognize the unique value proposition of Iridium OpenPort," said Don Thoma, executive vice president, Marketing, Iridium.
in Houston concluded that the K/T iridium spikes may have nothing to do with the extinctions.
NYC Transit is using Eagle's exclusive SatMAX(TM) repeater technology with Iridium services from WCC to provide multiple, concurrent NYC Transit personnel using standard Iridium satellite phones with fully wireless, non-line-of-sight satellite communications inside key NYC Transit facilities.
and MOSCOW, May 11 /PRNewswire/ -- Iridium Satellite LLC, the world's only mobile satellite services (MSS) operator with truly global coverage, announces it has formed a company called, "Iridium Communications Russia, OOO" to pursue a license for providing MSS services in Russia.
Because iridium has been found at the geologic boundary between the Cretaceous and Tertiary periods in concentrations exceeding typical iridium levels in the crust, some scientists have speculated that a meteorite had slammed into the earth, spraying the planet with a fine layer of meteoric iridium and other debris.