Sublimation products

For substances with a moderate triple point pressure e.g., benzoic acid, 6 mm., m.p. 122° naphthalene, 7 mm., m.p. 80° ), the simple process described above for camphor will not give a satisfactory yield of a sublimed product. Thus, for example, if naphthalene is heated it will melt at T (80°), and will boil when the vapour pressure is 760 mm. (218°) ... 

It was speculated that perhaps the largest isotope effects may always be associated with smallest retentions. It is also of interest to note that the retention was not affected by annealing at 140 °C. However, an unidentified, sublimable product was produced by thermal treatment in amounts of up to 10% of the radioruthenium, that is, in amounts equal to the retention. 

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). 

In 1881 L. Palmieri thought he detected helium in a yellow amorphous sublimation product from Vesuvius. When he heated it in the Bunsen flame, he was able to observe the D3 spectroscopic line with a wave length of 5875 Angstrom units (69, TO). Although R. Nasini and F. Anderlini were unable in 1906 to produce this line by similarly heating minerals known to contain helium, they believed that, if the helium in Palmieri s mineral was bound endothermally, he might possibly have observed its spectrum in this manner (69, 71). 

After completing chlorination, disconnect receiver 6 with the sublimed product and rapidly transfer it into a dry chamber or a large desiccator filled with dry carbon dioxide. Spill the obtained substance into a weighed drawn out test tube and seal the latter. Weigh the ampoule with the substance and the remaining part of the tube. Calculate the yield in per cent. 

A stoichiometric mixture of 3.478 g. (15 mmoles) of tungsten-(VI) oxide and 11.897 g. (30 mmoles) of tungsten(VI) chloride is placed in the reaction tube, and an excess of 1 mg. of tungsten(VI) chloride per milliliter of tube volume is added. The tube is sealed under vacuum and heated in a temperature gradient of 200/175°C. with the reaction mixture placed in the hotter part of the furnace (Fig. 14). After about 10 hours the reaction is complete, and 15 g. of tungsten(VI) tetrachloride oxide are obtained (98% yield). The analyses of the sublimed product by the H-tube method are somewhat inaccurate, because of the extreme moisture sensitivity of this substance (loss of hydrogen chloride by hydrolysis). Anal. Calcd. for W0C14 W, 53.82 Cl, 41.50 O, 4.68. Found W, 54.20 Q, 41.40 O, 4.46. 

Reaction time Temperature of sublimation No. Sublimated product (37) Yield3 Configuratio ee n Sb... 

In 24 hours about 3-4 mg. sublimed product could be obtained from 50 mg. of crude product. 

More than 40% oil can be achieved by heating the polymer at 25 K min to a final temperature of 700°C [30], The oil obtained is rich in aldehydes, ketones, carboxylic acids, alcohols and aromatic compounds 34% gas and 16% char were also produced. Pyrolysis at 500°C for 30 min leads to 73% gases, 19% solids and 9% liquids [31]. In this case a large amount of sublimed products are observed, which can cause problems by blocking pipes. Table 25.6 shows a comparison of different pyrolysis methods for PET. 

Confirm that equipment can safely operate and contain all product streams, e.g., off-gassing and sublimed products. 

Benzoic acid, known since the 17th century as a sublimation product of gum benzoin, sublimes at 100 °C and is deposited on the surface of the plant as a molecular vapor slight cooling thus leads to the formation of the white hoar frost crystals . 

Bismuth tris(4-methylbenzenesulfinate) (ca. 0.1-0.2 g) was heated in a sublimation apparatus at 200°C/10 -10 mmHg. After 5 h, the crude sublimed product was collected and recrystal-... 

We find it quite easy to isolate the sublimed product without the use of a drybox. The isolation procedure is as follows. The su-blimer is positioned horizontally, the stopper at the top is removed and with (Ar) flowing out of the flask the crystals are scraped from the walls and powdered using a stainless steel spatula. The product is then transfered to a storage flask connected through the side arm. 

Hexacarbonylmolybdenum (80% yield) is obtained by reducing M0CI5 with Cu—A1 (Devarda) alloy at a CO pressure of 150 atm at 100°C . Excellent yields of W(CO)g (86% of sublimed product) are obtained by operating under the more drastic conditions of 300 atm at MOT . 

The hydrazinium salt of pyridine-3,4-dicarboxylic acid monohydrazide or the free acid 1 was heated at 365 -370 °C, at which temperature the melt started to decompose and yielded a nearly colorless sublimable product. The compound was purified by recrystallization (HOAc), or by dissolving it in NH4OH, followed by filtration and precipitation with HOAc to give yellowish or colorless needles mp 365°C. 

Yellow powder or bronze-yellow micalike particles. M.p. 963° (in sealed tube) d 5.018. Heat of formation —51.8 kcal. per mole (25°). Solubility in HgO (g. NiBrg/lOO g. solution) 56.6 (19°C) 61.0 (100°C). Soluble in methyl and ethyl alcohols, acetone and quinoline insoluble in toluene. Crystal structure sublimed product, C 19 type unsublimed product, variable between C 6 and V19 types. 

To lower the friction and mechanochemical wear in friction joints it is possible to use solid lubricants [71] containing fuming-oxides (FO) as an active modifier of nonferrous metals. The solid lubricants represent fine-dispersed sublimation products of lead smelting slag. 

On the other hand, the presence of water during the course of an accident has been demonstrated to wash out and retain sublimation products of fission such as the iodine isotopes. 

Figure 2 Apparatus for simple sublimation at atmospheric pressures. Watch-glass, W, with sample, S, surmounted by filter funnel, FF, with cooling coils, C, glass wool, G, and collected sublimed product, P. A sealing ring, R, is included between the watch-glass and filter funnel.

Figure 1 Simple apparatus for demonstrating the principles of sublimation. S, sample P, sublimate (product) FP, perforated filter paper.

---