Chromium selenides

The compounds CrSe(cr), Cr3Se4(cr) and Cr2Se3(cr) have been reported in the system chromium-selenium. Cr2Se3(cr) exists in two modifications the low-temperature y phase, which is stable up to 1084 K and the high-temperature a phase. Experimental thermodynamic information is only available for the two polymorphs of Cr2Se3(cr). 

The heat capacity of a-Cr2Se3 was measured in the temperature range 6 to 300 K by Koshchenko, Yachmenev, Zhegalina, Pashinkin, and Danilenko in [90KOS/YAC], The values determined for the heat capacity and entropy at 298.15 K are selected  

The Gibbs energy of formation of y-Cr2Se3 was measured in the temperature range 413 to 493 K using the electrochemical cell 

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Chromium(III) sulfide, CrySs chromium selenide, CrSe chromium(III) telluride, Cr2Tc3 molybdenum(IV) sulfide, M0S2 (molybdenite) molybde-num(IV) selenide, MoSe2 molybdenum(IV) telluride, MoTey tungsten(IV) sulfide,... 

GON/LUK] Goncharuk, L. V., Lukashenko, G. M., Thermodynamic properties of chromium selenide Cr2Sc3, Russ. J. Phys. Chem., 60, (1986), 1089-1090. Cited on page 344. 

Goncharuk LV, Lukashenko GM (1986) Thermodynamic properties of chromium selenides, Cr2Se3. Russ J Phys Chem 60 1089-1089... 

No other oxide phases below MO2 have been established but a yellow hydroxide , precipitated by alkali from aqueous solutions of chromium(II), spontaneously evolves H2 and forms a chromium(III) species of uncertain composition. The sulfides, selenides and tellurides of this triad are considered on p. 1017. 

Ammonium sulphide) Barium sulphide Calcium sulphide Chromium (II) sulphide Copper (II) sulphide Diantimony trisulphide Dibismuth trisulphide Dicaesium selenide Dicerium trisulphide Digold trisulphide Europium (II) sulphide Germanium (II) sulphide Iron disulphide Iron (II) sulphide Manganese (II) sulphide Mercury (II) sulphide Molybdenum (IV) sulphide... 

Caesium selenide, 4265 Calcium polysulfide, 3942 Calcium sulfide, 3941 Cerium trisulfide, 3967 Chromium(II) sulfide, 4245 Cobalt(II) sulfide, 4218 Copper iron(II) sulfide, 4269 Copper(II) sulfide, 4285 Europium(II) sulfide, 4293... 

On-line anion exchange LC/ICP-MS methods for selenium and chromium speciation have been published [30], In studies of selenium speciation in environmental samples LC/ICP-MS and LC/ ESI-MS methods have been used for the determination of both inorganic and organic selenium species [43]. For the determination of methyl selenide, strong anion exchange and RP chromatography have been employed [43], while for the determination of seleno-aminoacids, IP RP chromatography with on-line detection based on ICP-MS has been successfully employed [44],... 

Aluminium and magnesium selenides are very similar light brown powders, unstable in air. Zinc and iron (ferrous) selenides are more stable in air, the zinc compound being citron-yellow and the iron compound black and metallic in appearance.8 The latter becomes brown in air owing to oxidation. Ferric selenide is difficult to obtain pure. Cadmium selenide, which is dark brown, is very stable in colour and is used as a pigment. With thallium, selenium is said to form three distinct compounds,9 but analyses of these compounds have led to discordant results. The selenides of aluminium, chromium and uranium cannot be prepared in the wet way. Nickel selenide, unlike the sulphide, shows no tendency to form a colloidal solution. 

Cadmium chromium(III) selenide can be prepared by the direct combination of the elements or by the reaction of cadmium selenide with chromium(III) selenide. Crystals of cadmium chro-mium(III) selenide have been prepared by flux growth1 in cadmium chloride, by vapor transport,2 and by a liquid-transport method3 with a platinum metal catalyst. The synthesis given... 

Although high-purity cadmium and selenium are commercially available, high-purity chromium(III) chloride is not. Therefore, if high-purity cadmium chromium(III) selenide is desired, it is best to make chromium(III) chloride by passing chlorine over high-purity chromium metal at high temperatures (ca. 1200°C.). 

The ampul is removed from the furnace and opened. Caution. Hydrogen selenide vapors are formed during the washing, and it is advisable that this operation also be performed in a hood. The crystals of cadmium chromium(III) selenide can be washed in water to remove the cadmium chloride. The crystals are black octahedra which vary in size up to about 3 mm. on an edge. The only impurities detected in these crystals by arc emission spectrographic analysis were Mg and Cu, and these are present only in amounts of less than 20 p.p.m. Anal. Calcd. for CdCr2 Se4 Cd, 21.1 Cr, 19.5 Se, 59.3. Found Cd, 20.8 Cr, 17.7 Se, 58.6. 

Cadmium chromium(III) selenide is a ferromagnetic semiconductor with a Curie temperature of 130 K. Crystals grown by this method are p type. Cadmium chromium(III) selenide has the spinel structure with a cubic cell edge of 10.75 A. 

For sulphur nitride, see nitrogen sulphide for selenium, nitride, see nitrogen selenide and for tellurium nitride, see nitrogen telluride. J. von Liebig 26 obtained a brown powder by igniting chromium chloride in ammonia, and he thought the product was elemental chromium. A. Schrotter showed that the product is chromium nitride, Cr2N2 or CrN. 

Caesium selenide, 4259 Calcium polysulfide, 3936 Calcium sulfide, 3935 Cerium trisulfide, 3961 Chromium(II) sulfide, 4239 Cobalt(II) sulfide, 4212 Copper iron(II) sulfide, 4263 Copper(II) sulfide, 4279 Europium(II) sulfide, 4287 Germanium(II) sulfide, 4413 Gold(ni) sulfide, 0116... 

Complexes with S-Donor, Se-Donor, or Te-Donor Ligands. The interatomic distances and valence distributions in the chromium thiospinels have been reviewed.151 Several mixed-metal sulphides, selenides, and tellurides containing chromium(m) have been reported this year, as detailed in Table 2. 

HOMOALLYLIC ALCOHOLS B-Allyldiisopino-campheylborane. Allyl phenyl selenide. Allyltri-/i-butyltin. Chromium(II) chloride. Crotyltrimethylsilane. Diethylftributyl-stannyl)aluminum. (2R,4R)-Pentanediol. Pinacol chloromethaneboronate. Tin-Aluminum. Titanium(lV) chloride. 

Transfer of material from one surface to another is a common phenomenon when surfaces rub against one another, and Rabinowicz suggests that it may be universal in dry contact. Some material combinations are of course much less prone to transfer than others, but Bowden and Tabor describe transfer between a diverse variety of material pairs, inciuding lead selenide and rock-salt, chromium and diamond, tin and platinum, and tungsten, iead or copper and steei. 

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