Selenide Fluorides

A bright gray LaSeF was obtained by low temperature (600 to 650 C) synthesis of LaFg and La2Se3 in evacuated vitreous silica ampules. The material was intermediately ground and pressed to tablets. The reaction product probably is orthorhombic, with lattice parameters a = 7.709, b =10.08, c = 6.402 A Z = 8 D25p = 6.16, D -aic = 6.323 g/cm. For a table of the indexed powder pattern, see the paper, Schmid, Hahn [3]. 

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The spinel structure is found among a very large number of oxides AB2X and also in a limited number of sulphides, selenides, fluorides and cyanides of the same composition, some of which are recorded in table 8.09. The cubic unit cell of this structure is shown in fig. 8.21 and contains 32 X ions. Each A ion is tetrahedrally co-ordinated by four and each B ion is octahedrally co-ordinated by six X neighbours, and each X ion is bound to one A and to three B ions. The co-ordination may therefore be summarized thus ... 

The most extensively studied oxide selenides belong to the M202Se type data on preparation and crystallographic properties dominate this section. Main topics of the sections on selenites, selenates, and associated alkali double compounds are the preparation of the compounds and their thermal decomposition. The selenide halides, especially the selenide fluorides of the type MSeF, show very interesting crystallographic properties. Main topics of this section are the polytypes of YSeF. 

Binary Compounds. The fluorides of indium are IrF [23370-59-4] IrF [37501-24-9] the tetrameric pentafluoride (IiF ) [14568-19-5], and JIrFg [7789-75-7]. Chlorides of indium include IrCl, which exists in anhydrous [10025-83-9] a- and p-forms, and as a soluble hydrate [14996-61-3], and IrCl [10025-97-5], Other haUdes include IrBr [10049-24-8], which is insoluble, and the soluble tetrahydrate IrBr -4H20 IrBr [7789-64-2]-, and Irl [7790-41-2], Iridium forms indium dioxide [12030-49-8], a poorly characteri2ed sesquioxide, 11203 [1312-46-5]-, and the hydroxides, Ir(OH)3 [54968-01-3] and Ir(OH) [25141-14-4], Other binary iridium compounds include the sulfides, IrS [12136-40-2], F2S3 [12136-42-4], IrS2 [12030-51 -2], and IrS3 [12030-52-3], as well as various selenides and teUurides. 

Hydrogen cyanide Calcium cyanide Potassium cyanide Sodium cyanide Hydrogen fluoride as F Hydrogen peroxide Hydrogen selenide as Se Hydrogen sulphide Hydroquinone... 

Hydrogen fluoride Hydrogen selenide Hydrogen sulphide... 

In lithium chloride, bromide and iodide, magnesium sulfide and selenide and strontium chloride the inter-atomic distances depend on the anion radius alone, for the anions are in mutual contact the observed anion-anion distances agree satisfactorily with the calculated radii. In lithium fluoride, sodium chloride, bromide and iodide and magnesium oxide the observed anion-cation distances are larger than those calculated because of double repulsion the anions are approaching mutual contact, and the repulsive forces between them as well as those between anion and cation are operative. 

Abrasion and corrosion protection for germanium, magnesium fluoride, cadmium telluride, zinc sulfide, and zinc selenide IR windows. 

Hydrogen cyanide Hydrogen fluoride Hydrogen selenide Hydrogen sulphide Methyl bromide (bromomethane)... 

Using the periodic table if necessary, write formulas for the following compounds (a) hydrogen bromide, (b) magnesium chloride, (c) barium sulfide, (d) aluminum fluoride, (e) beryllium bromide, (/) barium selenide, and (g) sodium iodide. 

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