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 ?
Chemical analysis of the Rhodic Eutrudox pH K Ca Mg H+Al SB (Ca[Cl.sub.2]) ([cmol.sub.c] [dm.sup.-3]) 5.08 1.05 3.87 1.81 3.49 6.73 pH CTC C P Cu (Ca[Cl.sub.2]) (g [dm.sup.-3]) 5.08 10.22 15.30 26.60 2.80 pH Zn Fe Mn V (Ca[Cl.sub.2]) (mg [dm.sup.-3]) (%) 5.08 111.00 32.80 4.90 65.85 H+Al (potential acidity); SB (sum of bases); CTC (cation exchange capacity); C (organic carbon); V% (base saturation); Cu, Zn, Fe and Mn extracted by Mehlich Table 2.
Campbell Cecil sandy Clayey, kaolinitic, NT 15 loam, <1% thermic, Typic CT 15 Kanhapludult Belle Mina Decatur silt Fine, kaolinitic, NT+PT 10 loam, <1% thermic, Rhodic NT 10 Paleudult CT 10 Notes: Treatments include conventional tillage (CT), strip tillage (ST), and no tillage (NT).
(2014), who studied a Rhodic Hapludox (Latossolo Vermelho distroferrico) managed for 20 years up to the 0.5 m depth.
Chemical analysis of the Rhodic Eutrudox used in the experiment at 0-5 and 0-20 cm depths [K.sup.+] [Ca.sup.2+] [Mg.sup.2+] Sample pH (Ca[C1.sub.2]) --[cmol.sub.c][dm.sup.-3]-- 0-5 5.10 0.66 6.36 1.07 cm 0-20 4.83 0.42 4.34 0.99 cm H+Al SB CEC OM Sample pH (Ca[C1.sub.2]) --[cmol.sub.c][dm.sup.-3]-- g [dm.sup.-3] 0-5 5.10 4.46 8.09 12.55 25.97 cm 0-20 4.83 5.79 5.75 11.54 20.51 cm P Cu Zn Fe Mn V% Sample pH (Ca[C1.sub.2]) --mg [dm.sup.-3]-- % 0-5 5.10 24.09 8.10 2.01 38.77 162.00 64.46 cm 0-20 4.83 10.58 12.50 1.44 76.65 261.00 49.83 cm H + Al (potential acidity); SB (sum of bases); CEC (cation exchange capacity); OM (organic matter), V% (saturation by bases), Cu, Zn, Fe and Mn extracted by Mehlich-1.
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.
Mujuru L, Mureva A, Veithorst EJ, Hoosbeek MR (2013) Land use and management effects on soil organic matter fractions in Rhodic Ferralsols and Haplic Arenosols in Bindura and Shamva district of Zimbabwe.
Three field experiments were conducted in the 2013/14, 2014/15 and 2016/17 cropping seasons, in Londrina, PR, Brazil (23[degrees] 11' S, 51[degrees] 11' W and 620m above sea level, CfaKopen-Geiger climate, Rhodic Eutrudox soil type, USDA or Latossolo Vermelho distrofico, Brazilian soil classification).