Prismatic

C), the yield of more than 90% purity L-glutamic acid crystals is very high. The glutamic acid crystals appear as both the metastable a- and stable P-forms. The a-form consists of prismatic crystals which are easy to filter, whereas the P-form needle crystals are difficult to filter. Control of crystallisation conditions of a-crystals are requited (13). The cmde L-glutamic acid crystals are suspended ia water and neutralized with caustic soda or sodium hydroxide. The solution is decolorized with activated carbon to produce a transparent solution and MSG is crystallized under reduced pressure. 

Below 65°C, sodium iodide is present ia aqueous solutions as hydrates containing varyiag amounts of water. When anhydrous sodium iodide is dissolved ia water, heat is Hberated because of hydrate formation, eg, AH = —174.4 kJ/mol (—41.7 kcal/mol), when the dihydrate is formed. At room temperature, sodium iodide crystallizes from water as the dihydrate [13517-06-1/, NaI-2H2 02H2O, ia the form of colorless prismatic crystals. 

Fluorides. Uranium fluorides play an important role in the nuclear fuel cycle as well as in the production of uranium metal. The dark purple UF [13775-06-9] has been prepared by two different methods neither of which neither have been improved. The first involves a direct reaction of UF [10049-14-6] and uranium metal under elevated temperatures, while the second consists of the reduction of UF [10049-14-6] by UH [13598-56-6]. The local coordination environment of uranium in the trifluoride is pentacapped trigonal prismatic with an 11-coordinate uranium atom. The trifluoride is... 

Chlorides. The oHve-green trichloride [10025-93-1], UCl, has been synthesized by chlorination of UH [13598-56-6] with HCl. This reaction is driven by the formation of gaseous H2 as a reaction by-product. The stmcture of the trichloride has been deterrnined and the central uranium atom possesses a riine-coordinate tricapped trigonal prismatic coordination geometry. The solubiUty properties of UCl are as follows soluble in H2O, methanol, glacial acetic acid insoluble in ethers. 

Bromides and Iodides. The red-brown tribromide, UBr [13470-19-4], and the black tniodide, Ul [13775-18-3], may both be prepared by direct interaction of the elements, ie, uranium metal with X2 (X = Br, I). The tribromide has also been prepared by interaction of UH and HBr, producing H2 as a reaction product. The tribromide and tniodide complexes are both polymeric soflds with a local bicapped trigonal prismatic coordination geometry. The tribromide is soluble in H2O and decomposes in alcohols. 

Cyclosporin A forms white prismatic crystals from acetone and is only slightly soluble in water and saturated hydrocarbons, but is very soluble in methanol, ethanol, acetone, and diethyl ether. Optical and nmr data on cyclosporins and x-ray crystallographic data on cyclosporin A and an io do derivative have been reviewed (273,275). 

Pure biphenyl is a white crystalline soHd that separates from solvents as plates or monoclinic prismatic crystals. Commercial samples are often slightly yellow or tan in color. Similady, pure terphenyls are white crystalline soHds whereas commercial grades are somewhat yellow or tan. Physical and chemical constants for biphenyl and the three isomeric terphenyls are given in Tables 2 and 3, respectively. 

Complex carbides are very numerous. Many newer compounds of this class have been discovered and their stmctures elucidated (20). The octahedron M C is typical where the metals arrange around a central carbon atom. The octahedra may be coimected via corners, edges, or faces. Trigonal prismatic polyhedra also occur. Defining T as transition metal and M as metal or main group nonmetal, the complex carbides can be classified as (/)... 

Crystal growth modifiers have been employed to improve filterabiHty and water retention of Ca(OCl)2 2H20, which typically crystallizes as fine plates. Addition of zinc dust or salts produces larger square- and diamond-shaped, untwinned dihydrate crystals (215). Coarse prismatic crystals are obtained by use of carbohydrates and carboxyHc acids and thek salts (216). 

Fig. 14. HTGR fuel elements (a) prismatic core HTGR fuel element (b) cross section of a spherical fuel element for the pebble bed HTGR. Reprinted from [88], 1977 Ameriean Nuelear Soeiety, La Grange Park, Illinois.

Oscine, CgHiaOjN, This substance, for which the name scopolin is in use in continental Europe, was first examined by Hesse and later t Luboldt. It forms colourless, hygroscopic prismatic crystals, m.p. 109 from ether or light petroleum, and boils at 241-3°. cZZ-Oscine has bee resolved into the d- and Z-forms by King by crystallisation of tl d-hydrogen tartrates. The characters of the three forms of oscine and ( their picrates and hydrochlorides are tabulated on p. 87. 

Chelerythrine crystallises from alcohol in colourless, prismatic leaflets, m.p. 207°, containing one molecule of alcohol. The alkaloid absorbs carbon dioxide from the air, becoming yellow. The solutions fluoresce blue when the alkaloid is contaminated with its oxidation product, which is formed by mere exposure of solutions to air. The salts, which are quaternary, are intensely yellow. The hydrochloride, B. HCl. HjO, forms citron-yellow needles, and the sulphate, B. H2SO4.2HjO, golden-yellow needles, sparingly soluble in water the platinichloride, B2. HaPtCl. ... 

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