Fibrous crystal

Disodium 4-nitrophenylphosphate (6H2O) [4264-83-9] M 371.1 Dissolve in hot aqueous MeOH, filter and ppte by adding Me2CO. Wash the solid with Me2CO and repeat the purification. Aq MeOH and Et20 can also be used as solvents. The white fibrous crystals contain less than 1% of free 4-nitrophenol [assay J Biol Chem 167 57 1947]. 

Silicon disulfide Al2S3+Si02 at 1200°C J >Si Fibrous crystals. Sublimes without melting. Attacked by water ... 

Sikorski, P., Atkins, E. D., and Serpell, L. C. (2003). Structure and texture of fibrous crystals formed by Alzheimer s abeta(ll-25) peptide fragment. Structure (Comb.) 11, 915—926. 

Retrograde metamorphic processes, linked to hydrothermal fluid circulation, finally produced a new mineral assemblage constituted mainly by tremolite-actinolite> epidote + chlorite + quartz + sericite + titanite + hematite. The amphibole appears as green fibrous crystals over clinopyroxene and other anhydrous minerals. 

DNAs are soluble only in aqueous solutions and their fibrous crystals can be prepared by slow evaporation from the aqueous solution. Duplex structures in the fibers have been studied by X-ray diffraction [2,3] and sohd state NMR [4-6]. Orientation of DNA strands by using hydrodynamic flow gradients in the dilute aqueous solution [7,8] and lyotropic liquid crystal... 

As might be anticipated for minerals with chain structures, pyroxenes commonly occur in columnar, prismatic, rodlike, and acicular forms. Enstatite has been found in the form of rosettes of fine-fibrous crystals. Special names such as victorite, chladnite, and shepardite were assigned to different occurrences in this distinctive morphology, possibly because the fibrous aggregates were located in iron meteorites. However, the composition and crystal... 

This product, tan fibrous crystals melting at 161-162°, amounts to 221-260 g. (39-48%) and is sufficiently pure for use in the next part of this preparation. The product may be purified further by recrystallization from benzene. The dibenzo-18-crown-6 polyether separates as white fibrous needles melting at 162.5-163.5° (Note 6). 

Note Fibrous crystals may comprise essentially extended chains parallel to the fibre axis however, macroscopic polymer fibres containing chain-folded crystals are also known. 

Apart from tri- and tetra-phosphates, which, like the familiar pyrophosphates, belong to this group, only calcium pentaphosphate has been obtained in a crystalline form. It is formed as so-called tromelite in the form of plates or fibrous crystals on tempering melts of the corresponding composition at temperatures between 920 and 990°C (136). That tromelite is in fact a pentaphosphate Ca7(P60i6)2 can be proved by paper chromatog-... 

Several isopolymolybdates which have been isolated from solution are polymeric or appear to have structures that do not persist in solution. These include the trimolybdates M2M03O10 XH2O, obtained as fibrous crystals from appropriately acidified solutions. The structures of Rb2Mo3Oi0H2O and RbNaMo3Oio contain infinite double chains of edge-shared MoOs octahedra.42 From more acidic solution polymeric pentamolybdates [MMosOi6H(H20)] slowly crystallize. The structure of the potassium salt reveals a complex three-dimensional network of MoOe octahedra.43... 

In practice the structure of any given polymer sample is by no means as regular as the above classification would imply and in most cases defies description in terms of recognizable structural elements. For example, Wunderlich64 shows examples of cobweb structures which can be found in polymers. Clearly, for the purposes of research specific structures have been identified and studied - but this does not mean that a regular solid of macroscopic dimensions may be contracted with these structures. In polymers therefore, we always have to deal with statistical assemblies of elements more or less precisely defined as e.g. lamellar crystal, fibrous crystals, tie chains etc. 

Calcium polyphosphates of a metaphosphate composition [Ca(P03)2]n have properties and molecular structures which should yield a substance which is refractory in most environments but is rapidly degraded in systems containing active enzymes. None of the known systems of calcium phosphates yield fibrous crystals, although very short acicular crystals have been grown. (2 )... 

Bis[3,4-dimethoxyphenyl] Ditellurium [Hypophosphorous Acid Method]5 A solution of 37.2 g (0.1 mol) 3,4-dimethoxyphenyl tellurium trichloride in 500 ml absolute ethanol is filtered. To the rapidly stirred filtrate 30 ml ( 0.3 mol) of 50% aqueous hypophosphorous acid are added at 20° as rapidly as possible. The solution soon sets to a mass of black fibrous crystals. The crystals are collected by filtration, washed with water, and dried in air yield 95% m.p. 136 139°. 

Much effort has been devoted to investigating the detailed architectures and the construction of spherulites. Early investigations of the crystallization of polymers through optical microscopy (OM) [7,8] posited that polymer spherulites consisted of radiating fibrous crystals with dense branches to fill space. Later, when electron microscopy (EM) became available, spherulites were shown to be comprised of layer-like crystallites [9,10], which were named lamellae. The lamellae are separated by disordered materials. In the center of the spherulites, the lamellae are stacked almost in parallel [5,6,11-15]. Away from the center, the stacked lamellae splay apart and branch, forming a sheaf-like structure [11,13-15]. It was also found that the thicknesses of lamellae are different [5,6,11,12]. The thicker ones are believed to be dominant lamellae while the thinner ones are subsidiary lamellae. 

Silicon disulfide does form fibrous crystals of this sort. 

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