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Dissolving and recrystallizing

Chevron Chemical Co. began commercial production of isophthahc acid in 1956. The sulfur-based oxidation of / -xylene in aqueous ammonia at about 320°C and 7,000—14,000 kPa produced the amide. This amide was then hydrolyzed with sulfuric acid to produce isophthahc acid at about 98% purity. Arco Chemical Co. began production in 1970 using air oxidation in acetic acid catalyzed by a cobalt salt and promoted by acetaldehyde at 100—150°C and 1400—2800 kPa (14—28 atm). The cmde isophthahc acid was dissolved and recrystallized to yield a product exceeding 99% purity. The Arco technology was not competitive and the plant was shut down in 1974. [Pg.493]

In a saturated solution, solute particles are dissolving and recrystallizing at the same rate. It is a state of dynamic equilibrium. There is constant exchange, yet there is no net change. [Pg.494]

In a presentation by Ciurczak [44], it was observed that pure d- and Z-amino acids gave identical NIR spectra, while racemic crystals generated quite different spectra. A paper presented by Ciurczak [45] in 1986 outlines work later completed by Buchanan et al. [46]. In this work, varying percentages of d- and Z-valine were mixed physically and scanned by NIR. The spectra were identical except for particle size-induced baseline shifts. These mixtures were then dissolved and recrystallized as recemic crystals. These new samples were scanned by NIR obvious qualitative and quantitative differences were observed. [Pg.86]

Reslurrying a solid can sometimes be an attractive alternative to recrystallization. Reslurrying is analogous to trituration. Since attention does not need to be paid to dissolving and recrystallizing the product, reslurrying is less labor-intensive than recrystallization. Reslurrying can remove impurities adsorbed to the surface of crystals, and after suitable contact with solvent the product is isolated by filtration. For example, excess p-nitrobenzyl bromide was removed from 21 by... [Pg.243]

Chilean niter deposits are mosdy sodium nitrate, but they also contain 0.3% iodine in the form of calcium iodate, Ca(I03)2. After the sodium nitrate in the niter is dissolved and recrystallized, the remaining solution contains 9 g/L sodium iodate, NaI03(aq). The NaI03 is converted to iodine when it reacts with sulfur dioxide and water. [Pg.412]

At this point, even though dissolving and recrystallizing continue, there is no further change in the concentration with time. The system has reached equilibrium that is, excess undissolved solute is in equilibrium with the dissolved solute ... [Pg.399]

The strength of crystal bridges depends not only on the amount of the dissolved and recrystallizing material but also on the speed of crystallization. At higher crystallization rates a finer bridge structure is formed which results in higher strength (see also Section 5.2.2). [Pg.37]

Fig. 49. Apparatus for dissolving and recrystallizing (the tube attachments o and d can also be located in the center sections). Fig. 49. Apparatus for dissolving and recrystallizing (the tube attachments o and d can also be located in the center sections).
To recrystallize the crude product, it is heated on a water bath with 150 ml. of absolute methanol in the complete absence of moisture. The solution is filtered hot and the pure PO(NHa)3, which precipitates on cooling, is suction-filtered. The mother liquor is discarded because it still contains some chloride. The undissolved crude product remaining is then treated in a sinfillar manner with 200 ml. of absolute methanol. The mother liquor from this crystallization is reused for dissolving and recrystallizing the remainder of crude product, a procedure that requires repetition of the above steps up to three times. The combined crystals are dried in vacuum. The product is chromatographlcally pure. The yield is 26 g. (70%, based on POCI3). [Pg.585]

The trianunonium salt is the most readily obtainable derivative of imidodisulfuric acid, HN(SOsH)2. Since the h5 drolysis of inoidodisulfuric acid is strongly catalyzed in acid solution, the dissolving and recrystallization of imidodisulfates must be effected from neutral or alkaline solutions. The so-called neutral salts, HN(SOsM)2, are obtained in the first case, whereas the basic, or trisub-stituted, salts, MN(S03M)2, are obtained from alkaline solutions. [Pg.181]

Many similarities exist between a saturated solution and a pure liquid and its vapor in a closed flask (see Section 12.2). For the liquid-vapor system, rates of vaporizing and condensing are equal for the solution, rates of dissolving and recrystallizing are equal. In the liquid-vapor system, particles leave the liquid to enter the space above it, and their concentration (pressure) increases until, at equilibrium, the space is saturated with vapor at a given temperature. In the solution, particles leave the solute to enter the solvent, and their concentration increases until, at equilibrium, the solvent is saturated with solute at a given temperature. [Pg.401]

Human bones contain 60-70% (by mass) calcium phosphate. They provide mechanical support but also store the calcium and phosphate ions that are used in the body for a variety of functions. Bones are not permanent structures but instead exist in a state of dynamic equilibrium with their surrounding tissues. Biological apatite is continually dissolving and recrystallizing in the body. This equilibrium state makes it possible to maintain the necessary concentrations of calcium and phosphate ions in body fluids such as blood and saUva. [Pg.367]

Li3P04, whose presence was detected using XRD, would then dissolve and recrystallize to LiFePOa where it would collect on the edges of the pre-existing LiFePOa nanoplates. Thus, is can be surmised that dumbbell LiFeP04 mesocrystal formation is based on a dissolution-recrystallization process with eventually complete phase transformation. [Pg.382]


See other pages where Dissolving and recrystallizing is mentioned: [Pg.463]    [Pg.88]    [Pg.6]    [Pg.66]    [Pg.196]    [Pg.110]    [Pg.476]    [Pg.286]    [Pg.113]    [Pg.96]    [Pg.2083]    [Pg.133]    [Pg.345]    [Pg.352]    [Pg.140]    [Pg.79]    [Pg.187]    [Pg.54]    [Pg.395]    [Pg.33]   
See also in sourсe #XX -- [ Pg.14 ]




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Recrystallization

Recrystallizations

Recrystallized

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