Amorphous substance

Meconidine, C21H23O4N. This alkaloid was prepared by Hesse and its existence in Japanese opium was confirmed by Machiguchi. It is a brownish-yellow, amorphous substance, m.p. 58°, easily soluble in alcobol, most organic solvents and in alkalis. It gives a green solution with sulphuric acid. The salts are amorphous. Meconidine is said to exhibit a slight tetanising action. 

A crystalline addition product of indole with picryl chloride (i.e. l-chloro-2,4,6-trinitrobenzene), together with an unidentified amorphous substance, were obtained by the action of picryl chloride on indole magnesium iodide, and analogous products were obtained in the reaction between the indole Grignard reagent and 1-chloro-2,4,5-trinitrobenzene. 

A mixture consisting of 8 grams of estriol, 20 grams of succinic acid anhydride and 60 ml of pyridine is heated at 90 C for 4 hours, after which the reaction mixture is poured into water. The aqueous solution is extracted with ether, the ether layer is separated, washed with diluted sulfuric acid and after that with water until neutral, then evaporated to dryness to obtain 14 grams of an amorphous substance. Melting point 82° to 86°C. This drying residue proves to consist of a mixture of estriol disuccinate and estriol monosuccinate, which are separated by repeated crystallization from a mixture of methanol and water. 

Increasing the pH to 10-11 (in the case of Nb - HF solution - pH = 8) reduced the Nb205 concentration in the solutions to 0.5-0.3 g/l and the solid precipitate was identified as a pure amorphous substance, which after thermal treatment was identified as niobium oxide. 

In this section we continue to explore the consequences of the existence of the low temperature excitations in amorphous substances, which, as argued in Section III, are really resonances that arise from residual molecular motions otherwise representative of the molecular rearrangements in the material at the temperature of vitrification. We were able to see why these degrees of freedom should exist in glasses and explain their number density and the nearly flat energy spectrum, as well as the universal nature of phonon scattering off these excitations at low T < 1 K). 

We note first that not all amorphous substances actually exhibit a negative a in the experimentally probed temperature range. In such cases, it is likely that the contraction coming from those interactions in these materials is simply weaker than the regular, anharmonic lattice thermal expansion. Other contributions to the Griineisen parameter will be discussed later as well. 

Solids exist as either amorphous compounds or crystalline compounds [22]. In the latter, the molecules are positioned in lattice sites. Usually, amorphous substances decompose by first-order kinetics, and as such distinguish themselves from crystalline compounds [23]. 

The effect of physical aging on the crystallization state and water vapor sorption behavior of amorphous non-solvated trehalose was studied [91]. It was found that annealing the amorphous substance at temperatures below the glass transition temperature caused nucleation in the sample that served to decrease the onset temperature of crystallization upon subsequent heating. Physical aging caused a decrease in the rate and extent of water vapor adsorption at low relative humidities, but water sorption could serve to remove the effects of physical aging due to a volume expansion that took place in conjunction with the adsorption process. 

Alekhine had mentioned that turanose reacts with phenylhydrazine. Maquenne prepared the phenylosazone and described its precipitation from water in the flocculent or gel condition that is so very characteristic of the substance, but he did not report an analysis. A year after Ma-quenne s publication, Emil Fischer16 examined a small sample of amorphous turanose which had been sent by Dr. Konowaloff of Moscow. Its phenylosazone was prepared in good crystalline form by several recrystallizations from aqueous alcohol the analysis of these crystals proved conclusively the disaccharide formula for turanose which Alekhine had proposed from the analysis of amorphous substances. The writer had occasion recently to prepare turanose phenylosazone in considerable quantity its very characteristic properties and those of the derived phenylosotriazole are described on pages 27 and 28. 

Independent of the growth of ice crystals (Section 1.1.2), which can be observed down to approx. -100 °C, and a possible recrystallization (Section 1.1.3), this chapter describes only such developments or changes of structures that can be influenced by additives. The addition of CPAs to albumins, cells or bacteria influences the nucleation of ice - or at least its growth - in such a way that their natural structures are retained as much as possible. On the other hand, additives are introduced to crystallize dissolve substances. If this method does not help, e. g. with antibiotics, the solution concentrates increasingly until a highly viscous, amorphous substance is included between ice crystals. This condition has disadvantages ... 

CPAs should, at least partially, solidify in the amorphous state. However amorphous state alone does not assure protection. Izutsu et al. [3.4] showed, for beta-galactosidase by X-ray diffraction, that only such additives avoid denaturation, which do not crystallize. A dilution of protein in the solidified protective agent reduces the chance of reactions between the protein molecules. Amorphous substances dry more slowly, which makes it easier to avoid overdrying. 

For example, amorphous clarithromycin was prepared by grind and spray-drying processes, and XRPD was used to follow changes in crystallinity upon exposure to elevated temperature and relative humidity [59]. Exposure of either substance to a 40°C/82% RH environment for seven days led to the formation of the crystalline form, but the spray-dried material yielded more crystalline product than did the ground material. This finding, when supported with thermal analysis studies, led to the conclusion that the amorphous substances produced by the different processing methods were not equivalent. 

The 500 nm size is a limit value crystallites below this size tend to broaden the diffraction peaks in a spectrum, while size distributions above this value produce particularly sharp signals whose half width is a function only of the wavelength of the X-ray beam and the equipment. Signal broadening is at its maximum in materials known as X-ray amorphous substances, featuring particle size distributions below 8 nm. These afford flattened, washed-out spectra of little analytical value. 

At a high degree of supersaturation, the nucleation rate is so high that the precipitate formed consists mostly of extremely small crystallites. Incipiently formed crystallites might be of a different polymorphous form than the final crystals. If the nucleus is smaller than a one-unit cell, the growing crystallite produced initially is most likely to be amorphous substances with a large unit cell tend to precipitate initially as an amorphous phase ("gels"). 

Each particle of a predominantly covalently bonded amorphous substance can be considered as a macromolecule. The surface groups are equivalent to the end groups of macromolecular chemistry. 

The basic modem data describing the atomic stmcture of matter have been obtained by the using of diffraction methods - X-ray, neutron and electron diffraction. All three radiations are used not only for the stmcture analysis of various natural and synthetic crystals - inorganic, metallic, organic, biological crystals but also for the analysis of other condensed states of matter - quasicrystals, incommensurate phases, and partly disordered system, namely, for high-molecular polymers, liquid crystals, amorphous substances and liquids, and isolated molecules in vapours or gases. This tremendous... 

Especially methods of electron microscopy are important at study of X-ray amorphous substances and polyphase nanomixtures which are distributed very widely in the nature such as agate, bauxite, bitumen, coal, natural glasses etc., as X-ray diffraction is almost useless at analyzing such mostly disordered materials. 

Natural stibnite is black orthorhombic crystal or grayish-black powder the compound also exists as an amorphous substance in yeUow-red modification distorted octahedral arrangement density 4.64 g/cm for the natural stibnite and 4.12 g/cm for the red modification melts at 550°C vaporizes around 1150°C insoluble in water (1.75mg/L at 18°C) and acetic acid soluble in hydrochloric acid and caustic soda solution also, soluble in alcohol, ammonium hydrosulfide and potassium sulfide. 

Reddish-brown hexagonal crystal the pentadecahydrate is a dark green amorphous substance while the octadecahydrate is a violet cubic crystal the densities are 3.10 g/cm (the anhydrous salt), 1.87 g/cm (pentadecahydrate), 1.709/cm (octadecahydrate) the anhydrous sulfate is insoluble in water and acids the hydrate salts are soluble in water the pentadecahydrate is insoluble in alcohol, but the octadecahydrate dissolves in alcohol. 

Crystals (or amorphous substances) are also formed in living bodies as a result of biological activities to act as a reservoir for necessary components (for example, amorphous silica in grass cells, and calcium oxalate or inuline crystals in dahlias and begonias), or crystals are formed by excretion processes or due to illness (for... 

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