Steam distillation, rapid

With stirring, 6 g of ammonium chloride (to decompose excess acetylide) is added and the remaining ammonia is allowed to evaporate. To the residue is added cautiously 50 g of crushed ice followed by 150 ml of water the contents are mixed and steam distilled rapidly to obtain the 1-hexyne. The organic layer is separated, dried (magnesium sulfate), and distilled through a short column. 1-Hexyne has bp 71-72° the yield is about 28 g (68 %). 

Sodium i-nitro-2-naphtholate, 13, 78 Sodium perbenzoate, 13, 86 Sodium succinate, 12, 72 Sodium sulfide, 12, 68, 76 16, 72 Soxhlet extractor, 16, 69 17, 74 Stannic chloride, 18,1 Stannous chloride, 17, 10, 11 Steam distillation, rapid, 17, 20 Stilbene, 17, 90... 

B. o-Phthalaldehyde. The a,a,a, a -tetrabromo-0-xylene (344-370 g.) obtained as described above, part A, is placed in a 5-1. round-bottomed flask with 4 1. of 50% (by volume) ethanol and 275 g. of potassium oxalate. The mixture is heated under reflux for 50 hours (a clear yellow solution is formed after 25-30 hours). About 1750 ml. of the ethanol is then removed by distillation (which is stopped before the product begins to steam-distil), and 700 g. of disodium monohydrogen phosphate dodecahydrate (Na2HP04-12H20) is added to the aqueous residue. The mixture is steam-distilled rapidly (Note 4), using an efficient condenser, until 10-12 1. of distillate is collected and the distillate no longer gives a black color test for o-phthalaldehyde 8 when a portion is treated with concentrated ammonium hydroxide fol-... 

A solution of 13.75 g. (0.104 mole) of 2-chloromethylthiophene (p. 80) and 14.5 g. (0.104 mole) of hexamethylenetetramine in 50 ml. of chloroform is heated under reflux for 1 hour. The crystalline precipitate is removed by filtration, washed with ether, and air-dried. This material is then dissolved in 100 ml. of hot water and steam-distilled rapidly. The distillate is acidified with dilute hydrochloric acid and extracted with ether. Distillation of the dried ethereal extracts gives 5.9 g. (51%) of 2-thiophenealdehyde boiling at 187°/630 mm. 

The material to be steam-distilled (mixed with some water if a solid compound, but not otherwise) is placed in C, and a vigorous current of steam blown in from D. The mixture in C is thus rapidly heated, and the vapour of the organic compound mixed with steam passes over and is condensed in E. For distillations on a small scale it is not necessary to heat C if, however, the flask C contains a large volume of material or material which requires prolonged distillation, it should be heated by a Bunsen burner, otherwise the steady condensation of steam in C will produce too great a volume of liquid. 

Steam Distillatioo. A compact and efficient apparatus is shown in Fig, 43. The liquid to be steam-distilled is placed in the tube A and water is placed in the outer flask B. On heating B, steam passes into the inner tube A through the inlet tube C, and steam-volatile compounds are rapidly distilled and collected in the receiver placed at the end of the condenser D. 

To carry out a steam distillation, the solution (or mixture or the solid with a little water) is placed in the flask B, and the apparatus is completely assembled. Steam is passed into the flask B, which is itself heated by means of a small flame to prevent too rapid an accumulation of water, at such a rate that it is completely condensed by the condenser C. The passage of steam is continued until there is no appreciable amount of water-insoluble material in the distillate. If the substance crystallises... 

Sometimes an air bubble enters the tube E and prevents the regular flow of liquid from B the air bubble is easily removed by shaking the rubber tube. The flask A is heated (e.g., by a ring burner) so that distillation proceeds at a rapid rate the process is a continuous one. If the liquid to be steam distilled is lighter than water, the receiver must be modified so that the aqueous liquors are drawn off from the bottom (see Continvmia Extraction of Liquids, Section H, 44). 

Heat a suspension of 22 g. of the diacetate in a mixture of 120 ml. of concentrated hydrochloric acid, 190 ml. of water and 35 ml. of alcohol under reflux for 45 minutes. Cool the mixture to 0°, filter the solid with suction, and wash with water. Purify the crude aldehyde by rapid steam distillation (Fig. II, 41, 3) collect about 1500 ml. of distillate during 15 minutes, cool, filter, and dry in a vacuum desiccator over calcium chloride. The yield of pure o-nitrobenzaldehyde, m.p. 44—45°, is 10 g. The crude solid may also be purified after drying either by distillation under reduced pressure (the distillate of rather wide b.p., e.g., 120-144°/3-6 mm., is quite pure) or by dissolution in toluene (2-2-5 ml. per gram) and precipitation with light petroleum, b.p. 40°-60° (7 ml. per ml. of solution). 

The most popular device for fluoride analysis is the ion-selective electrode (see Electro analytical techniques). Analysis usiag the electrode is rapid and this is especially useful for dilute solutions and water analysis. Because the electrode responds only to free fluoride ion, care must be taken to convert complexed fluoride ions to free fluoride to obtain the total fluoride value (8). The fluoride electrode also can be used as an end poiat detector ia titration of fluoride usiag lanthanum nitrate [10099-59-9]. Often volumetric analysis by titration with thorium nitrate [13823-29-5] or lanthanum nitrate is the method of choice. The fluoride is preferably steam distilled from perchloric or sulfuric acid to prevent iaterference (9,10). Fusion with a sodium carbonate—sodium hydroxide mixture or sodium maybe required if the samples are covalent or iasoluble. 

Liquid pyridine and alkylpyridines are considered to be dipolar, aprotic solvents, similar to dimethylformarnide or dimethyl sulfoxide. Most pyridines form a significant azeotrope with water, allowing separation of mixtures of pyridines by steam distillation that could not be separated by simple distillation alone. The same azeotropic effect with water also allows rapid drying of wet pyridines by distillation of a small forecut of water azeotrope. 

The base may be purified by steam distillation but distillation under reduced pressure is more satisfactory. The oil is dried over 5 g. of solid sodium hydroxide and distilled in vacuo. I he first portion of the distillate may contain -toluidine and must be carefully separated, as it causes rapid discoloration. The 3-bromo-4-aminotoluene is obtained as a colorless liquid of b.p. i20-i22°/30 mm. or 92-94 /3 mm. It solidifies on cooling and melts at 16-18°. The loss on purification is about 15 per cent of the weight of the crude base. 

The reaction mixture is then transferred to a 2-I. round-bottom flask with wide neck, and to this is added all at once 300 g. of cracked ice, and the mixture is rapidly agitated by a rotary motion until the decomposition is complete (Note 7). Sufficient 30 per cent sulfuric acid is added to dissolve the magnesium hydroxide, and the mixture is then steam-distilled until oil no longer collects on the surface of the distillate. The distillate, which amounts to 1500-2500 cc., is saturated with sodium chloride and the upper layer separated. The aqueous layer is extracted with two loo-cc. portions of ether and the ether extract added to the alcohol layer. The ether solution is dried over anhydrous potassium carbonate, filtered, and heated carefully on the steam cone until all the ether is distilled. The crude alcohol is warmed one-half hour with about 5 g. of freshly dehydrated lime (Note 8). After filtering again and washing the lime with a little ether, the ether is distilled and the alcohol is distilled in vacuo from a Claisen flask (Note g). The carbinol distils at 88-93 /18 mm. (practically all distilling at 91°). The yield is 70-74 g. (61-65 P r cent of the theoretical amount) (Note 10). 

It is advisable to begin the steam distillation at once, while the mixture is hot, and to avoid the use of a free flame, which might cause breakage of the flask. If foaming, or too great a volume, hinders a rapid distillation, it is well to decant part of the contents of the flask and to conduct the steam distillation in two portions. 

Methylfurfural may be prepared by a modification of this method, which is more rapid but gives lower yiddsd A solution of 800 g. of sucrose in i 1. of hot water is allowed to flow slowly into a boiling solution of 500 g. of stannous chloride crystals, 2 kg. of sodium chloride, and 4 1. of 12 per cent sulfuric acid in a 12-I. flask. The aldehyde distils ofl as rapidly as it is formed and is steam-distilled from the original distillate after rendering it alkaline witlr sodium carbonate. The product is isolated by benzene extraction of the second distillate and distillation under reduced pressure. The yield is 27-35 g- (10-13 per cent of the theoretical amount). 

If the mixture is not cooled, the reaction will get out of control because of the rapid evolution of chloroform, and some ketone may steam-distil. 

In one process the resulting solution is continuously withdrawn and cooled rapidly to below 75°C to prevent hydrolysis and then further cooled before being neutralised with ammonia. After phase separation, the oil phase is then treated with trichlorethylene to extract the caprolactam, which is then steam distilled. Pure caprolactam has a boiling point of 120°C at 10 mmHg pressure. In the above process 5.1 tons of ammonium sulphate are produced as a by-product per ton of caprolactam. 

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