rhodium

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rhodium

(rō`dēəm), metallic chemical element; symbol Rh; at. no. 45; at. wt. 102.90550; m.p. about 1,966°C;; b.p. 3,727±100°C;; sp. gr. 12.41 at 20°C;; valence +2, +3, +4, +5, or +6. Rhodium is a lustrous, silver-white, chemically resistant metal in the so-called platinum group of metals 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
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. It has a face-centered cubic crystalline structure. It is insoluble in most acids, including aqua regia, but is dissolved in hot concentrated sulfuric acid. Rhodium compounds include halides, oxides, sulfates, sulfites, a nitrate, and a sulfide. The salts form rose-colored aqueous solutions. Rhodium is found associated with other platinum metals in river sands and in compounds in such minerals as rhodite and sperrylite. It is obtained as a byproduct in the refining of nickel sulfide ores mined near Sudbury, Ont., Canada.

The major use of the metal is in alloys with platinum and iridium; it gives improved high-temperature strength and oxidation resistance. These alloys are used in pen nibs, high-temperature thermocouple and resistance wires, bearings, and electrical contacts and as a catalyst. In motor vehicle catalytic converters, it converts the nitrogen oxides in the exhaust into nitrogen and oxygen. The metal itself, because of its brilliance and resistance to tarnish, is used to plate jewelry and the reflectors of searchlights. Rhodium was discovered in 1804 by W. H. WollastonWollaston, William Hyde,
1766–1828, English scientist, M.D. Cambridge, 1793. His wide-ranging scientific achievements include the discovery (1802) of the dark lines (Fraunhofer lines) in the solar spectrum; invention of the reflecting goniometer (an instrument by which the
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 in crude platinum ore.

rhodium

[′rōd·ē·əm]
(chemistry)
A chemical element, symbol Rh, atomic number 45, atomic weight 102.9055.
(metallurgy)
A silver-white metal in the platinum family; sometimes alloyed with platinum for thermocouples or used as a tarnish-resistant electrode posit.

rhodium

a hard corrosion-resistant silvery-white element of the platinum metal group, occurring free with other platinum metals in alluvial deposits and in nickel ores. It is used as an alloying agent to harden platinum and palladium. Symbol: Rh; atomic no.: 45; atomic wt.: 102.90550; valency: 2--6; relative density: 12.41; melting pt.: 1963?3?C; boiling pt.: 3697?100?C
References in periodicals archive ?
Tillage impacts on soil property, runoff, and soil loss variations from a Rhodic Paleudult under simulated rainfall.
Madari B, Machado POA, Tores E, Andradea AG, Valencia LIO (2005) No tillage and crop rotation effects on soil aggregation and organic carbon in a Rhodic Ferralsol from southern Brazil.
The soil of the experimental site was classified as an Rhodic Eutrudox (Food and Agriculture Organization, 2006), with clayey texture (558.
Soil definitions: Rhodic ferralsols with fine texture in hilly to steep areas (frFHS), eutric gleysols with coarse texture in undulating areas (geCU), lithosols hilly to steep slope (ilqHS), chromic luvisols with medium to fine texture in undulating areas (lcMFU), chromic luvisols in moderate to steep areas (lcMS), gleyic luvisols (lg), orthic luvisols in moderate to hilly areas (loMH), dystric nitrosols (nd), cambic arenosols (qc), luvic arenosols (ql), chromic vertisols with fine texture in undulating areas (vcFU), calcic yermosols with coarse to moderate texture and in undulating to hilly areas (ykCMUH), lithosols in hilly and steep areas (ilqHS), luvic arenosols (ql), dystric nitosols (nd), gleyic luvisols (lg).
The soil type at Athens was Appling coarse sandy loam (clayey, kaolinitic, thermic Typic Hapludults), whereas the soil type at Plains was Greenville sandy clay loam (clayey, kaolinitic, thermic Typic Rhodic Paleudults).
The predominant soils are Rhodic Ferralsol and Orthic Ferralsol (Oliveira et al.
Multivariate analysis and geostatistics of the fertility of a humic rhodic hapludox under coffee cultivation.
The soil was classified as a Rhodic Ferralsols (World Reference Base for Soil Resource) Prior to establishment, the field was under conventional tillage using an ox-plough with continuous maize cultivation and no fertiliser application.