Sublime, the

The only disadvantage is that the procedure does not give accurate results if the compound sublimes the capillary tube method should be used in such cases, and it may be necessary to employ a sealed capillary tube. This apparatus should find a place in every laboratory. It is... 

In France, Compagnie Europnene du Zirconium (CEZUS) now owned jointly by Pechiney, Eramatome, and Cogema, uses a separation (14) based on the extractive distillation of zirconium—hafnium tetrachlorides in a molten potassium chloride—aluminum trichloride solvent at atmospheric pressure at 350°C. Eor feed, the impure zirconium—hafnium tetrachlorides from the zircon chlorination are first purified by sublimation. The purified tetrachlorides are again sublimed to vapor feed the distillation column containing the solvent salt. Hafnium tetrachloride is recovered in an enriched overhead fraction which is accumulated and reprocessed to pure hafnium tetrachloride. 

Specifications and Packaging. Aluminum chloride s catalytic activity depends on its purity and particle size. Moisture contamination is an important concern and exposure to humid air must be prevented to preserve product integrity. Moisture contamination can be deterrnined by a sample s nonvolatile material content. After subliming, the material remaining is principally nonvolatile aluminum oxide. Water contamination leads to a higher content of nonvolatile material. 

It melts at 39°C and may be purified by vacuum sublimation. The Hquid boils at 233°C to give a monomeric vapor in which the Ti—Br distance is 231 pm. Titanium tetrabromide is soluble in dry chloroform, carbon tetrachloride, ether, and alcohol. Like titanium tetrachloride, TiBr forms a range of adducts with molecules such as ammonia, amines, nitrogen heterocycles, esters, and ethers. 

The use of potassium hexafluorosihcate is preferred over sodium hexafluorosihcate because of the lower tendency of the potassium compound to dissociate the lose sihcon tetrafluoride by sublimation. The addition of potassium carbonate or chloride to the fusion mix further reduces this tendency and promotes completion of the reaction. The reaction is conducted in a rotary furnace operating at 700°C. The product is cmshed prior to leaching with acidified hot water. The hot slurry is filtered to remove the sihca, and potassium hexafluorozirconate crystallizes as the solution cools. 

Acridine (2,3-benzoquinoline) [260-94-6] M 179.2, m 111° (sublimes), b 346°, pK 5.58 (pK of excited state 10.65). Crystd twice from benzene/cyclohexane, or from aqueous EtOH, then sublimed, removing and discarding the first 25% of the sublimate. The remainder was again crystd and sublimed, discarding the first 10-15% [Wolf and Anderson 7Am Chem Soc 77 1608 7955]. 

Adamantyl fluoride (1-fIuoroadamantane) [768-92-3] M 154.2, m 210-212" (dec), 259-260" (dec). Dissolve in Et20, dry over Na2S04 evaporate to dryness and sublime the residue at 90-100°/12mm. Recryst sublimate from MeOH, m 259-260°. [Zh Org Khim 30 1609 1965.] To remove 1-hydroxyadamantane impurity, dissolve in cyclohexane cool for many hours, filter off the hydroxyadamantane, and evaporate to dryness. Recrystallise the residue from pet ether at -77° and sublime in vacuum, m 210-212° dec (sealed tube). [J Org Chem 30 789 1965.]... 

Adamantyl isothiocyanate [4411-26-1] M 193.3, m 168-169". Dissolve in Et20, wash with H2O, dry (Na2S04), evtqjorate and sublime the residue in a vacuum at 140°, and recryst from MeOH. Irritant [Chem Ber 95 2302 1962.]... 

The cooled contents of the 2S0-ml. flask containing ferrous chloride (Note 6) are added to the cold sodium cyclopentadienide solution while passing a stream of nitrogen through both flasks. The combined mixture is stirred for 1.25 hours at a temperature just below reflux. Solvent is removed by distillation, and the ferrocene is extracted from the residue with several portions of refluxing petroleum ether (b.p. 40-60°). The product is obtained by evaporation of the petroleum ether solution. Ferrocene may be purified by recrystallization from pentane or cyclohexane (hexane, benzene, and methanol have also been used) or by sublimation. The 3ueld is 31-34 g. (67-73%) (Note 7), m.p. 173-174°. 

As regards general methods for distinguishing between the alkaloids of opium, mention may be made of the following Kofler and Kofler s study of the micro-sublimation of these alkaloids and the characters of the micro-sublimates the comparison by Maplethorpe and Evers of the picrates of a series of opium bases, comparison of the colour reactions of a series of opium alkaloids, and their behaviour with specific reagents and precipitants. ... 

This table shows that the similarity of the two aglycones is most marked in their salts, but they do not appear to be dimorphic forms giving identical salts, for the melting-points of the bases are unchanged after sublimation, the rotations of the two bases in solution are different, though those of the two hydrochlorides are identical within the limits of experimental error, and all attempts at interconversion of the two bases... 

Many solid substances (camphor, iodine, naphthalene, etc.), are known which are appreciably volatile at ordinary temperatures. Others, such as the metals, are apparently quite fixed, but they probably possess a definite, although very small vapour-pressure, even at ordinary temperatures. Thus, if magnesium is heated to 550° for a few hours in a magnesia boat enclosed in a vacuous tube it sublimes in beautiful crystals on the cool part of the tube. The vaporisation of a solid without previous fusion is called sublimation the vapour-pressure (like the vapour-pressure of a liquid), is definite for each temperature, is independent of i the volume of the vapour space, and increases with rise of temperature. 

The thermodynamic treatment of sublimation is exactly analogous to that of evaporation. Ramsay and Young (1884) have proved experimentally that during sublimation the temperature remains constant, and heat is absorbed for unit mass this is the latent-heat of sublimation, Ls. 

Sublimation. During sublimation, the lattice constituents of the solid are directly transferred to the gas phase without the intervention of liquefaction, though there may be mobile intermediates at the surface of the heated solid. Various features of the sublimation process have been reviewed by Somorjai [18] and by Rosenblatt [19] who included consideration of kinetic aspects. Rhead [ 20] has discussed diffusion processes at surfaces. 

At low pressures, NH3 is desorbed and HC104 is also volatilized. Both may rapidly diffuse from the heated zone and recombine elsewhere on the cool walls of the vacuum envelope as sublimate. The kinetics of sublimation, which may accompany the low temperature reaction [926], have been studied and discussed in detail [931,932]. The rate of this process is deceleratory throughout, empirically obeying eqn. (7) [931]... 

The checkers obtained pure indoIe-3-carbonitrile, m.p. 182-184°, by subliming the product at a pressure of 1.5 mm. (bath temperature 165-170°) and reerystallizing the sublimate from a mixture of acetone and light petroleum ether. The recovery was 84%. 

Examples electron proton neutron, subcritical Having a mass less than the critical mass. sublimation The direct conversion of a solid into a vapor without first forming a liquid, sublimation vapor pressure The vapor pressure of a solid. 

The submitters reported a melting point of 114-116°. The checkers obtained analytically pure material with a recovery of 80% after decolorization with activated carbon and recrystallization from 2-3 ml. of hexane at 0°. The product was also purified with comparable efficiency by sublimation at 85-90° (10 mm.). A small amount of a yellow, volatile impurity was removed from the cold finger before the product began to sublime. The melting point of the product after purification by the checkers was 110-112°. The reported melting point is 114-116°. 

Dichlorodibenzo- -dioxin. 2-Bromo-4-chlorophenol (31 grams, 0.15 mole) and solid potassium hydroxide (8.4 grams, 0.13 mole) were dissolved in methanol and evaporated to dryness under reduced pressure. The residue was mixed with 50 ml of bEEE, 0.5 ml of ethylene diacetate, and 200 mg of copper catalyst. The turbid mixture was stirred and heated at 200°C for 15 hours. Cooling produced a thick slurry which was transferred into the 500-ml reservoir of a liquid chromatographic column (1.5 X 25 cm) packed with acetate ion exchange resin (Bio-Rad, AG1-X2, 200-400 mesh). The product was eluted from the column with 3 liters of chloroform. After evaporation, the residue was heated at 170°C/2 mm for 14 hours in a 300-cc Nestor-Faust sublimer. The identity of the sublimed product (14 grams, 74% yield) was confirmed by mass spectrometry and x-ray diffraction. Product purity was estimated at 99- -% by GLC (electron capture detector). 

Sublimation The change of state from solid to gaseous without going... 

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