Purification, liquids steam distillation

Steam Distillation. Distillation of a Pair of Immiscible Liquids. Steam distillation is a method for the isolation and purification of substances. It is applicable to liquids which are usually regarded as completely immiscible or to liquids which are miscible to only a very limited extent. In the following discussion it will be assumed that the liquids are completely immiscible. The saturated vapours of such completely immiscible liquids follow Dalton s law of partial pressures (1801), which may be stated when two or more gases or vapoms which do not react chemically with one another are mixed at constant temperature each gas exerts the same pressure as if it alone were present and that... 

To 50 gm (0.50 mole) of vinyl -butyl ether is added 0.25 gm of stannous chloride. After a few minutes the temperature begins to rise to 45°-50 C and then more rapidly to 140°C. The product obtained is a yellowish brown, balsamlike mass. Purification by steam distillation leaves 35 gm (70%) of a viscous, liquid, yellow polymerization product. 

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. 

Common impurities found in aldehydes are the corresponding alcohols, aldols and water from selfcondensation, and the corresponding acids formed by autoxidation. Acids can be removed by shaking with aqueous 10% sodium bicarbonate solution. The organic liquid is then washed with water. It is dried with anhydrous sodium sulfate or magnesium sulfate and then fractionally distilled. Water soluble aldehydes must be dissolved in a suitable solvent such as diethyl ether before being washed in this way. Further purification can be effected via the bisulfite derivative (see pp. 57 and 59) or the Schiff base formed with aniline or benzidine. Solid aldehydes can be dissolved in diethyl ether and purified as above. Alternatively, they can be steam distilled, then sublimed and crystallised from toluene or petroleum ether. 

Because phenols are weak acids, they can be freed from neutral impurities by dissolution in aqueous N sodium hydroxide and extraction with a solvent such as diethyl ether, or by steam distillation to remove the non-acidic material. The phenol is recovered by acidification of the aqueous phase with 2N sulfuric acid, and either extracted with ether or steam distilled. In the second case the phenol is extracted from the steam distillate after saturating it with sodium chloride (salting out). A solvent is necessary when large quantities of liquid phenols are purified. The phenol is fractionated by distillation under reduced pressure, preferably in an atmosphere of nitrogen to minimise oxidation. Solid phenols can be crystallised from toluene, petroleum ether or a mixture of these solvents, and can be sublimed under vacuum. Purification can also be effected by fractional crystallisation or zone refining. For further purification of phenols via their acetyl or benzoyl derivatives (vide supra). 

The complex composition of aqueous environmental sample matrices, especially sewage and marine water samples, and the low concentrations in which the surfactants are generally found, have made it necessary to perform an initial stage of concentration and purification of the analytes prior to its analysis. Traditionally, such steps were carried out off-line with procedures based on liquid—liquid extraction (LLE), sublation or steam distillation, followed by chromatographic clean-up steps. 

Many purification techniques are not practical when dealing with large quantities of material. In general the most useful methods of purification that can be applied to large quantities of material are recrystallization for solids, and distillation or steam distillation for liquids. These techniques have already been discussed in previous chapters. Chromatography should... 

Distillation is the most important method for effecting the purification of liquids. Other methods, such as fractional freezing, counter-current extraction, and chromatography are available. This section will be devoted to the distillation procedures, and the other methods will be discussed in later chapters. Several methods of distillation are known, such as fractional distillation, molecular distillation, and steam distillation, and these will be considered in turn. 

The phosphorus vapour is taken from the top of the furnace (Figure. 4.1), condensed and collected under water. The yellow product is liable to contain As and Sb in quantities up to 100 ppm, as well as some Si, C, Fe, S and F. Decolourisation and partial purification can be effected by filtering the liquid element through active carbon, while repeated washing will reduce the Si content. Steam distillation will reduce the As and Sb content to 2 ppm. Further purification for laboratory use can be done by extraction with dry CSj. 

In steam distillation, a mixture of water and organic liquid distills over. This is used as a method of purification of organic liquids especially those liquids which may tend to decompose at a temperature lower than their normal boiling points. 

Diazotization, Isoiation, and Purification Add 0.07 g of powdered sodium nitrite in small portions to the vial. When the addition is complete, use a drop or two of absolute ethanol to rinse any solid that may stick to the sides of the vial into the solution. Equip the vial with a condenser and heat the mixture under gentle reflux for about 10 min. Add 2 mL of hot water to the vial and equip it for simple distillation. Steam-distill the mixture until about 1 mL of liquid remains in the vial. 

The reaction product, which is a dark reddish-brown liquid, is poured or siphoned (Note 5) into 1.5 1. of water to which 50 cc. of a saturated solution of sodium bisulfite has been added (Note 6). The mixture is distilled with steam (Org. Syn. 2, 80) and the first portion of the distillate is collected separately to remove a small amount of unchanged nitrobenzene. It is necessary to collect about 12 1. of distillate in order to obtain all of the m-bromonitrobenzene. The yellow crystalline solid is filtered with suction and pressed well on the funnel to remove water and traces of nitrobenzene. The yield of crude product varies from 270-340 g. (60-75 Per cent °f the theoretical amount). It melts at 51.5-520 and boils at 117-118 79 mm. This product is satisfactory for most purposes. If a purer material is desired, the crude /w-bromonitrobenzene may be distilled under reduced pressure. The recovery on purification is about 85 per cent. Briihl recorded the b.p. as 1380/18 mm. and the m.p. as 56° for pure wz-bromonitrobenzene.1... 

Figure 21.2 shows the entire low-temperature process in block flow format. Following the reactor and cooler, the liquid EDC is washed, removing unreacted chlorine and catalyst. Product EDC is obtained in two distillation steps drying, where water and a small amount of light by-products are removed and purification, which removes a small amount of heavy by-products. Both of these distillation steps use steam-heated reboilers. 

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