Distillation by

In practice, simulated distillation by gas phase chromatography is used for the following objectives ... 

Finally, other methods are used to obtain simulated distillation by gas phase chromatography for atmospheric or vacuum residues. For these cases, some of the sample components can not elute and an internal standard is added to the sample in order to obtain this quantity with precision. 

The flash curve at atmospheric pressure can be estimated using the results of the ASTM D 86 distillation by a correlation proposed by the API. For the same volume fraction distilled one has the following relation ... 

Extraction of steam distillates by solvents. The apparatus, depicted in Fig. 11,58, 7, may be employed for the continuous extraction of substances which are volatile in steam from their aqueous solutions or suspensions. Solvents of the ether type (i.e., lighter than water) or of the carbon tetrachloride type (i.e., heavier than water) may be used. A reflux condenser is inserted in the Bl9 socket, whilst flasks of suitable capacity are fltted into the lower B24 cone and the upper. B19 cone respectively. For extraction with ether, the flask attached to the upper. B19 cone contains the ether whilst the aqueous solution is placed in the flask fltted to the lower B2i cone the positions of the flasks are reversed... 

Reflux 1 ml. of the ether with 5 ml. of freshly distilled, constant boiling point hydriodic acid (Section 11,49,2), b.p. 126-128°, for 2-3 hours. Add 10 ml. of water, distil and collect about 7 ml. of liquid. Decolourise the distillate by the addition of a httle sodium bisulphite, and separate the two layers by means of a dropper pipette (Fig. 11,27,1). Determine the b.p. of the resulting iodide by the Siwoloboff method (Section 11,12) and prepare a crystalline derivative (Section 111,42). 

Place 45 g. (43 ml.) of benzal chloride (Section IV,22), 250 ml. of water and 75 g. of precipitated calcium carbonate (1) in a 500 ml. round-bottomed flask fltted with a reflux condenser, and heat the mixture for 4 hours in an oil bath maintained at 130°. It is advantageous to pass a current of carbon dioxide through the apparatus. Filter off the calcium salts, and distil the filtrate in steam (Fig. II, 40, 1) until no more oil passes over (2). Separate the benzaldehyde from the steam distillate by two extractions with small volumes of ether, distil off most of the ether on a water bath, and transfer the residual benzaldehyde to a wide-mouthed bottle or flask. Add excess of a concentrated solution of sodium bisulphite in portions with stirring or shaking stopper the vessel and shake vigorously until the odour of benzaldehyde can no longer be detected. Filter the paste of the benzaldehyde bisulphite compound at the pump... 

An alternative method of removing the aniline is to add 30 ml. of concentrated sulphuric acid carefully to the steam distillate, cool the solution to 0-5°, and add a concentrated solution of sodium nitrite until a drop of the reaction mixture colours potassium iodide - starch paper a deep blue instantly. As the diazotisation approaches completion, the reaction becomes slow it will therefore be necessary to teat for excess of nitrous acid after an interval of 5 minutes, stirring all the whUe. About 12 g. of sodium nitrite are usually required. The diazotised solution is then heated on a boiling water bath for an hour (or until active evolution of nitrogen ceases), treated with a solution of 60 g. of sodium hydroxide in 200 ml. of water, the mixture steam-distilled, and the quinoline isolated from the distillate by extrsM-tion with ether as above. 

Diethylene glycol method. Place 0-5 g. of potassium hydroxide pellets, 3 ml. of diethylene glycol and 0 5 ml. of water in a 10 or 25 ml. distilling flask heat the mixture gently until the alkali has dissolved and cool. Add 1-2 g. of the ester and mix well. Fit the flask with a thermometer and a small water-cooled condenser in the usual way. Heat the flask over a small flame whilst shaking gently to mix the contents. When only one liquid phase, or one hquid phase and one solid phase, remains in the flask, heat the mixture more strongly so that the alcohol distils. Identify the alcohol in the distillate by the preparation of the 3 5 dinitrobenzoate (Section 111,27,2). 

Step 4. The steam-volatile neutral compounds. The solution (containing water-soluble neutral compounds obtained in Step 1 is usually very dilute. It is advisable to concentrate it by distillation until about one-third to one-half of the original volume is collected as distillate the process may be repeated if necessary and the progress of the concentration may be followed by determination of the densities of the distillates. It is frequently possible to salt out the neutral components from the concentrated distillate by saturating it with solid potassium carbonate. If a layer of neutral compound makes its appearance, remove it. Treat this upper layer (which usually contains much water) with solid anhydrous potassium carbonate if another aqueous layer forms, separate the upper organic layer and add more anhydrous potassium carbonate to it. Identify the neutral compound. 

Other Organic Processes. Solvent extraction has found appHcation in the coal-tar industry for many years, as for example in the recovery of phenols from coal-tar distillates by washing with caustic soda solution. Solvent extraction of fatty and resimic acid from tall oil has been reported (250). Dissociation extraction is used to separate y -cresol fromT -cresol (251) and 2,4-x5lenol from 2,5-x5lenol (252). Solvent extraction can play a role in the direct manufacture of chemicals from coal (253) (see Eeedstocks, coal chemicals). 

The process operates at 1 kPa (10 mbars) and 450 kW of power. When the condenser temperature reaches 580°C, the power is reduced to 350 kW. Cooling water is appHed to the condenser, throughout distillation, by means of sprays. Normally distillation takes 10—12 hours and the end point is signified by an increase in furnace temperature and a decrease in vapor temperature to 500—520°C. At this point the power is turned off and the vacuum pump is shut down. Nitrogen is then bled into the system to prevent oxidation of 2inc. 

CycIohexanediamine s commercial origin is its presence as a minor 0.1 <1% coproduct of hexamethylenediamine [124-09-4] produced by hydrogenation of adiponittile [111-69-3]. Fractional distillation by up to four columns in a series is routine commercial practice to purify nylon grade acychc diamine the cmde cycloahphatic diamine requires further refining before use as a specification intermediate. 

It can be found in animal tissues (1), in vegetables and fmit (2,3), or in spring water (4), and has also been identified in meteorites (5). It is formed in alcohohc fermentation (6) and in the chemical and biochemical oxidation of fats. Succinic acid is present in amber (7) Succinuni) and can be obtained by distillation, by which method it was first isolated by Georgius Agricola in 1550. 

Distillation By-Products. Of the CTO distiHation by-products, ie, pitch, heads, and DistiHed TaH Oil (DTO), only the last, a unique mixture of rosin and fatty acids, has significant commercial value. Pitch and heads are used as fuel the former has a fuel value of 41,800 kj/kg. TaH oil heads have outstanding solvent properties, but also have a bad odor, which is hard to remove. They contain a relatively high fraction of palmitic acid which can be recovered by crystallization. 

An alternative to TBP distillation is simulated distillation by gas chromatography. As described by Green, Schmauch, and Worman [Anal. Chem., 36, 1512 (1965)] and Worman and Green [Anal. Chem., 37, 1620 (1965)], the method is equivalent to a 100-theoretical-plate TBP distillation, is veiy rapid, reproducible, and easily automated, requires only a small microliter sample, and can better... 

S-DlmethyK trattn (2). A mixture of 6,7-dlmethyKetralln 1 (18.0 g, 0.11 mol) and HjSOa was heated under stirring to 80°C and maintained at this temperature for 15 min, then at 25°C for 24 h. The mixture was diluted with water and distilled with superheated steam. From the distillate by extraction with EljO and distillation there was obtained 4.5 g of 2 (24%), bp 110-115°C, no - 1.5530. 

The yield is determined by weighing the cold trap before and after distillation of methylenecyclopropane. Any small amounts of tetra-hydrofuran carried into the methylenecyclopropane trap are eliminated in a subsequent distillation. By proton magnetic resonance analysis the checkers found that no tetrahydrofuran reached the cold traps the spectrum (dichloromethane) shows a triplet at S 1.00 and a quintuplet at S 5.35 in the ratio 4 2. 

In light ends distillation, by contrast, the number of compounds present is usually less than 30 and may be as low as 3 or 4. Thus, the feed to a light ends distillation tower can be described in terms of the percentages of the various individual compounds present. 

Doherty, M., and G. Buzad (1992). Reactive Distillation by Design. The Chemical Engineer (27 August), sl7-sl9. 

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