Crystal setting

A mixture of 14.1 parts of 1 -benzyl-4-cyano-4-piperidinopiperidine and 40 parts of 90% sulfuric acid is heated on a steam bath for 10 minutes. Without further heating, the mixture is stirred until a temperature of about 20°C is obtained. The mixture is then poured into 150 parts of ice-water and the resultant solution is alkalized with excess ammonium hydroxide solution. The aqueous solution is decanted from the precipitated oil. On treating this oil with 80 parts of acetone, crystallization sets in. After one hour the solid is filtered off and dried to yield 1 -benzyI-4-piperidinopiperidine-4-carboxamide melting at about 137.5°C to MO C. 

The butyl-alcoholic solution is evaporated in vacuo and the residue dissolved with gentle heating in 25 parts by volume of methyl alcohol. 100 parts by volume of acetone are added, the solution filtered and further quantities of acetone added, whereupon crystallization sets in. Yield 12.2 parts by weight of the pure product, having the melting point 177° to 179°C. 

The modification improves performance and is interesting in connection with x-ray emission spectrography (Chapters 7, 8, and 9). It consists in measuring the intensity of tin Ka relative to that of scattered x-rays entering the detector from an analyzing crystal set for the reflection of x-rays 2.2 A in wavelength. As the tin coating becomes thicker, increased attenuation of the x-rays scattered by the iron cause s the intensity ratio to increase more rapidly than does the intensity of tin Ka. Table 6-3 contains performance data for the Quantrol on Method II (modified). The instrument can also be set up to use industrially a modification of Method III. 

Update the crystallization set W(t +i) Activate the supersaturated salts SM tn+i) that are expected to crystallize in the time interval (tn,tn+l)... 

Fig. 27a-c. Electron spin echo envelope modulation of Co(acacen), temperature 4K. a) Nuclear modulation pattern of Co(acacen) diluted into a Ni(acacen) 1/2 H20 single crystal. Crystal setting rotation axis I,

Fourier transform of the nuclear modulation pattern (From R. de Beer1 4)) c) Stick spectrum ENDOR frequencies (AmN = 1, 2) calculated from the hfs and quadruple tensors in Ref. 59 dashed lines ms = - 1/2, full lines ms = 1/2... 

The crude benzotriazole is placed in a 200-cc. modified Claisen flask (Org. Syn. Coll. Vol. 1, 125) and distilled under reduced pressure (Note 2). The yield of white solid (yellow cast) boiling at 201-204° at J5 mm. or 156-159° at 2 mm. is 92-99 g. The product in the receiver is melted over a luminous flame and poured into 250 cc, of benzene. The clear solution is stirred until crystallization sets in after being chilled for two hours, the product is filtered on a Buchner funnel. The colorless benzotriazole weighs 90-97 g. (75-81 per cent of the theoretical amount) (Note 3) and melts at 96-97°. 

Hie present crystallizer set-up is equipped with a pH indicator-controller and a temperature indicator. The temperature in the crystallizer is controlled heat supplied to the feed and liquor recirculated through the absorption tank. 

Due to light scattering, crystalline polymers mostly yield turbid films.Their blends with other polymers are always demixed because polymers are not able to form mixed crystals. Consequently, crystallizable polymers only yield homogeneous blends above their melting point. As soon as crystallization sets in, the components will separate. 

In this way the coordinates of all reciprocal lattice points on the zero layer lying within the area ODBECF are directly determined. Fig. 102 shows the results obtained from a 90° oscillation photograph (Plate VIII) of a gypsum crystal set with its c axis inclined 8 ° to the axis of rotation in spite of the limited precision in the determination of", there is no doubt about where to draw the net. If the remaining. 

The above remarks refer to the symmetries of molecules in crystals. It is very important to remember that the symmetry of a molecule in its crystal setting is not necessarily the full symmetry of an isolated molecule, since, as we have seen, the full symmetries of molecules are not always utilized in forming crystalline arrangements. Suppose, for example, that X-ray and other evidence leads to the definite conclusion that certain molecules in their crystal setting have no symmetry. It does not follow that these molecules in isolation are asymmetric it may be that in isolation they would have axes of symmetry or planes of... 

The reaction flask is removed from the oil bath, and the solution is poured into a 250-ml. beaker to crystallize 10 ml. of benzene is used to rinse out the flask. When crystallization sets in, 50 ml. of petroleum ether (b.p. 35-55°) is added to the warm mixture with manual stirring. After the mixture has been chilled in an ice bath, the product is filtered by suction and washed with 100 ml. of a 1 1 petroleum ether-benzene mixture. It is then removed from the funnel, stirred into a slurry with 100 ml. of the mixed solvent, filtered, and again washed with 50 ml. of the solvent. These washings remove the bulk of the color, and a powdery white product remains. After standing overnight in a warm place, the product weighs 35.5-36.5 g. (74-76%) and melts at 104-105°. It may be purified further by recrystallization from benzene (3.7 ml. per g.). The yield of colorless benzoylacetanilide melting at 106-106.5° cor. is 32-34 g. 

This chapter is concerned with the influence of mechanical stress upon the chemical processes in solids. The most important properties to consider are elasticity and plasticity. We wish, for example, to understand how reaction kinetics and transport in crystalline systems respond to homogeneous or inhomogeneous elastic and plastic deformations [A.P. Chupakhin, et al. (1987)]. An example of such a process influenced by stress is the photoisomerization of a [Co(NH3)5N02]C12 crystal set under a (uniaxial) chemical load [E.V. Boldyreva, A. A. Sidelnikov (1987)]. The kinetics of the isomerization of the N02 group is noticeably different when the crystal is not stressed. An example of the influence of an inhomogeneous stress field on transport is the redistribution of solute atoms or point defects around dislocations created by plastic deformation. 

SEMICONDUCTORS. Materials and devices known as semiconductors have been the backbone of the electronics industry for many years. Semiconductors did not enter the industry in a major way, however, until several years after the vacuum tube (valve) had been well established. In terms of perspective, it is interesting to note that at least one. semiconductor device predated the vacuum tube in the early days of radio communication. This was the then familiar galena crystal and accompanying whisker used in early crystal set radio receivers. 

The still necessary increase in accuracy requires an additional effort. A simultaneous spectroscopy of pionic and muonic hydrogen atoms is planned as the muonic X-rays do not show any strong interaction broadening, but exhibit Doppler broadening similar to pionic atoms. A method was found to measure pionic and muonic X-rays simultaneously. The reduced masses of pionic and muonic hydrogen exhibit almost the same ratio as two lattice plane differences of quartz. With a two crystal set up the pionic and muonic X-rays can be Bragg reflected to the same CCD detector. 

The intrinsic photoconductivity of BaCP crystals sets in at a photon energy of about... 

Reliance Fm, Belingwe belt, Zimbabwe. About 6.5 mm across photo. Olivine crystals set in fine grained to once-glassy groundmass. For details see Nisbet et al. (1987). Photo W. E. Cameron, (b) Alternating iron-rich and carbon-rich shales. White bands are chert this lithology is transitional to banded ironstone. Approximately, 20 cm across picture. Belingwe belt, Zimbabwe. 

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