Showing papers on "Chromium published in 1970"
TL;DR: In this article, a technique for studying orientation effects on nearly opaque single crystals with laser Raman spectroscopy is described in detail, and the instrument used in these studies is a Spex monochromator.
Abstract: A technique for studying orientation effects on nearly opaque single crystals with laser Raman spectroscopy is described in detail. The instrument used in these studies is a Spex monochromator. The scattering equations derived are applied to a study of iron(III) oxide and chromium(III) oxide.
192 citations
TL;DR: In this article, it was shown that theoretically unstable Cr (III) species are often dominant in water in solubility equilibrium with the atmosphere and CrO42− is the major form of trivalent and hexavalent chromium in sea water.
186 citations
TL;DR: Boron 1~ and chromium 3E binding energies have been measured for 25 boron compounds and 17 chromium compounds and the data correlate linearly with calculated atomic charges.
Abstract: Boron 1~ and chromium 3E binding energies have been measured for 25 boron compounds and 17 chromium compounds. The data correlate linearly with calculated atomic charges. A linear correlation is also demonstrated for CNDO~calculated atomic charges and carbon 1~ binding energies determined by other workers.
161 citations
110 citations
TL;DR: The crystal structure of [OCr3(CH3COO)6.3H20]-C1 -.6H20 has been determined from three-dimensional diffractometer data using Cu Ke radiation as discussed by the authors.
Abstract: The crystal structure of [OCr3(CH3COO)6.3H20]+C1 -. 6H20 has been determined from three-dimensional diffractometer data using Cu Ke radiation. The configuration of the complex cation consists of three chromium atoms linked to a central oxygen atom in a planar configuration. Each chromium atom is coordinated octahedrally by the central oxygen atom, one from each of four acetate groups and a water molecule. The acetate groups link the vertices of the three octahedra in the complex cation. The anions and those water molecules not included in the cations are disordered and lie in channels along the twofold axes. Their structure is ill-defined, but a reasonable model can be presented in which the cations are linked by a system of hydrogen bonds into zigzag layer3 perpendicular to the c axis.
94 citations
87 citations
TL;DR: In this article, the preparation of nitrides of chromium has been studied in detail, and the antiferromagnetic paramagnetic transformation in CrN exhibits temperature hysteresis and is shown to be a transformation of the first kind.
Abstract: The preparation of nitrides of chromium has been studied in detail. Oxygen free samples of Cr1.000Nx, x ranging from 0.997 to 0.980, have been prepared by equilibrating at temperatures from 850 to 1048 °C in one atmosphere pressure of nitrogen. Results of the temperature dependences of expansivity, lattice parameters, magnetic susceptibility and electrical resistivity of CrN of various compositions are reported. The antiferromagnetic paramagnetic transformation in CrN exhibits temperature hysteresis and is shown to be a transformation of the first kind. The transformation temperature of Cr1.000N0.997 is 286 °K.
Die Herstellung von Chromnitriden wurde ausfuhrlich untersucht. Sauerstofffreie Praparate der Zusammensetzung Cr1.000Nx (x variiert zwischen 0.997 und 0.980) wurden bei Temperaturen zwischen 850 und 1048 °C unter einem Stickstoffdruck von 1 Atm hergestellt. Ergebnisse zur Temperaturabhangigkeit der Ausdehnung, der Gitterkonstanten, der magnetischen Suszeptibilitat und des spezifischen elektrischen Widerstandes verschiedener CrN-Zusammensetzungen werden mitgeteilt. Die Umwandlung vom antiferromagnetischen zum paramagnetischen CrN weist eine Temperaturhysterese auf, die sich als Umwandlung erster Art ergibt. Die Umwandlungstemperatur des Cr1.000N0.997 betragt 286 °K.
82 citations
TL;DR: In this article, the diffusion coefficient and solubility of hydrogen in metal foils were derived by a very sensitive electrochemical method at room temperature, and in some cases with temperatures up to 80°C, for platinum, nickel, tantalum, titanium, zirconium, manganese and iron-chromium alloys.
77 citations
Journal Article•
TL;DR: Magnesium and eight trace mineral elements, manganese, copper, nickel, zinc, lead, tin, cadmium, and chromium, were determined by atomic absorption spectroscopy in 11 known wheats or wheat blends, 20 commercially prepared flours from these wheats, and 25 specially prepared products from the flours as mentioned in this paper.
Abstract: Magnesium and eight trace mineral elements, manganese, copper, nickel, zinc, lead, tin, cadmium, and chromium, were determined by atomic absorption spectroscopy in 11 known wheats or wheat blends, 20 commercially prepared flours from these wheats, and 25 specially prepared products from the flours. The same minerals were determined in ten consumer products from ten different cities. There was significant variation among the five hard wheats in their content of nickel, zinc, lead, tin, cadmium, and chromium. Manganese, copper, zinc, cadmium, and chromium varied significantly in the four soft wheat samples, most of the variation being contributed by a single low mineral wheat. The concentration of manganese, copper, zinc, and magnesium were about the same or lower and nickel, tin, cadmium, and chromium higher in the cake and crackers than in the respective flour from which they were made. Although there were significant variations in the lead, cadmium, and chromium concentrations in most of the market samples of consumer products there was no discernible effect of geographic location on the general mineral content of these products. Whole-wheat consumer products contained greater concentrations of manganese, copper, zinc, magnesium, and chromium than did products made from white flour. The selenium content of amore » small group of wheat blends and products was determined by a colorimetric method. 8 references, 7 tables.« less
76 citations
TL;DR: Li4Cr2(CH3)8· 4 C 4H8O has been determined by three-dimensional X-ray analysis and by IR spectra taken at 100°K and 300°K as mentioned in this paper.
74 citations
TL;DR: The reaction of 2.4.6-triphenylphosphorine with chromium hexacarbonyl in boiling dibutyl ether affords the red-brown crystalline (2.4,6) tricaronyl as discussed by the authors.
Abstract: Die Umsetzung von 2.4.6-Triphenyl-phosphorin mit Chromhexacarbonyl liefert in siedendem Dibutylather rotbraunes 2.4.6-Triphenyl-phosphorin-chrom(0)-tricarbonyl. Die IR-, NMR-und Massenspektren der Verbindung sprechen fur ein π-gebundenes Phosphorinsystem.
(Triphenylphosphorine)chromium(0)tricarbonyl
Reaction of 2,4,6-triphenylphosphorine with chromium hexacarbonyl in boiling dibutyl ether affords the red-brown crystalline (2,4,6-triphenylphosphorine) chromium (0) tricarbonyl. The i. r., n.m.r., and mass spectra of this complex suggest a π-bonded phosphorin ring system.
TL;DR: In this paper, the K β emission spectra of calcium, titanium, chromium, manganese and iron and oxidic compounds of these elements were investigated by means of the fluorescent method.
TL;DR: In this paper, the authors investigated holes in the β-rhombohedral structure and found that there are at least eight holes of sufficient size to accommodate boron or metal atoms in the structure.
Patent•
08 Oct 1970TL;DR: In this paper, a method for preparing silica-containing olefin polymerization catalysts is described, which involves adding an alkali metal silicate to an acid under defined conditions of addition to produce a hydrogel, recovering the gel in the substantially dry condition by employment of an oxygenated organic compound and impregnating the gel with a chromium compound.
Abstract: A method for preparing silica-containing olefin polymerization catalysts, and the process performable therewith, the preparation involving adding an alkali metal silicate to an acid under defined conditions of addition to produce a hydrogel, recovering the gel in the substantially dry condition by employment of an oxygenated organic compound and impregnating the gel with a chromium compound
Patent•
22 Jun 1970
TL;DR: In this paper, an improved version of the chocia catalanguage for FLUORINATION of HALOGENATED HYDROCARBONS is described, which is prepared by TREATING a chocIUM HYDROXIDE PASTE with water or steams before being dined.
Abstract: AN IMPROVED CHROMIA CATALYST FOR FLUORINATION OF HALOGENATED HYDROCARBONS IS PREPARED BY TREATING A CHROMIUM HYDROXIDE PASTE WITH WATER OR STEAM BEFORE BEING DRIED AND CALCINED.
TL;DR: In this article, it has been shown that 1,2,3,4,5,pentamethylnaphthalene (15) and 1.2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 14, 15, 16, 17, 18, 19, 20, 21, 22, 23, 24, 25, 26, 27, 28, 30, 30 and 30, 31, 30] are intermediate molecules of 2-butyne.
Abstract: \\bstract: Reacrion of triphenyltris(tetrahydrofuran)chromium(III) (f) with 2-butyne y'ields, inter alia, 1,2,3,4' tetremerhylnaphthalene (2). A free or metal-complexed tetramethylcyclobutadiene has been exclr-rded as an inter-mediare rn rhis reaction by the observation that 1,2-dimethyl-3,4-di(methyl-rir)naphthalene (6) is not a product of I and 2-burl ne-1,1,1-d3 (3). Examination of the relative yields of 1,2,3,4,5-pentamethylnaphthalene (15) and 1,2,3,' .1.6-pentamerhylnaphthalene (16) tbrmed in reaction of 2-butyne with trio -tolyl-, tri'nr-tolyl-, and trip -tolyltris-(terrahldroiuren)chromium(III) demonstrates thiit a iong-lived aryne-chromium complex is also not an intermedi-atc in fhe:e cyclizations. Labeling and kineric isotope experiments using partially deuterated derivatives of 1 fur-rhcr drse rcdir bcnzyne complexes as intermediates in the tbrmation of 2. The reaction of trimesityltris(tetrahydro-iurrn)chronrrumtlll) with 2-butyne to torm cis-2-mesitylbut-2-ene suggests that an initial step in these reactions may be rnserrron ot'2-butyne into a carbon-chromium bond rvirh formation of an intermediate vinylic chromium reagent (2{r. The additional observations that 2-biphenylmagnesium bromide and trichlorotris(tetrahydrofuran)chro-mrum(lll) relct to form 5-(2-biphenyl)dibenzchromole (29), and that this chromocyclc reacts with 2-butyne to yield 9.lr.t-dimcthylphenanrhrene, impliclte an analogous chromocycle 3,4-dimethyt-5-phenylbenzchromole (34) in the l'ormarron of 2. Taken togethei with further deuterium exchange and labeling experiments. thcse obscrvations lead ro rhc proposal thar the reaction of I with 2-buryne proceeds by initial insertion of one molccule ol'2-butyne into a phcnll-chromium bond of l, cyclization of thc resulting vinylic chromium contpound rvith elimination of benzene to iorm chromocycle 34, anci reaction of the chromocycle with a second molecule of 2-butyne to yield 2 (Scheme VII). rclooliuonrerizetion of acetylene by transition ntetal clitllvsts pror ides the basis for a number of useiul orslnic sl'ntheses.3 Attenrpts to establish mechanisms ior this class of reactions have been hindered by' dif'hculties in identifying the active organometallic catalvsts. Although a variety of structures have been postulated tor these catalysts, it has proved possible to isollte and characterize mechanistically significant reection intermcdiates or by-products in only a small number oi reactions.{'; Precedcnts derived from the ertensir elv explored chemistry of transition-metal acety-lenc conrplexes suggest that these cyclooligomerization reactions are initiated by coordination of one or more molecules of acetylenic substrate to a metal atom or metal atonr cluster of the catalyst. s'6 The process(es) b1' which the coordinated acetylenes are subsequently conr erted to product has been variously suggested to involr e metallocyclic, r'z's ?r-allylic,s\"'e'r0 or cyclo-butadienes' r0-r3 intermediates. or to proceed by a con-certecl \" n-ntulticenter\" rcaction pat[. t t' t3 Of these suggested and not necessarily exclusive mechanistns, only the …
TL;DR: In this paper, the effect of alloying on the behavior of Fe-Cr-Ni base alloys in boiling MgCl2 solutions was investigated, and the most effective alloy additions were found to be aluminum, beryllium, and carbon.
Abstract: This study investigated the effect of alloying on the behavior of Fe-Cr-Ni base alloys in boiling MgCl2 solutions. Alloys included commercial Fe-Cr-Ni alloys; ternary Fe-Cr-Ni alloys to 40% Cr; fourth-component alloys with specific alloy bases; fourth-, fifth-, and sixth-component alloys. The primary experimental measurements were time-to-breaking of wire specimens. In addition, polarization, potential time, current decay, constant potential cracking, and metallographic studies were conducted. Alloys of very substantial improvement in resistance to cracking were found. The most effective alloy additions were found to be aluminum, beryllium, and carbon. Lowering chromium to the 10-15% range was also found to be very effective in preventing cracking. The results are discussed in terms of the slip-step dissolution model of stress corrosion cracking.
TL;DR: A series of octahedral chromium(III) complexes of the type cis[Cr cyclamX 2 ] + (cyclam = 1,4,8,11-tetraazacyclotetradecane; X = Cl, Br, NCS, ONO and N 3 ) have been isolated as crystalline salts as mentioned in this paper.
TL;DR: Several new spinels of general formula A+12A3+12Cr2X4 were prepared, where A+ was Li, Cu or Ag: A3+ was Al, Ga, or In: and X was S or Se.
TL;DR: In this paper, the absolute differential cross sections for elastic deuteron scattering and (d, p) reactions with isotopes of calcium and chromium at incident energies of 10 MeV and for some Ca isotopes at 12 MeV were derived.