Column types Vigreux

Separation of liquids whose boiling points are between 5°C and 50 C apart requires the use of an apparatus which gives better contact between the vapour and liquid phases in the distillation column. One of the most common types of fractionating column, a Vigreux column, is shown in Fig. 11.9a. A 50cm long vacuum jacketed Vigreux should allow reasonable separation of compounds which bod 30-40°C apart. 

A Vigieux-type column 60 cm. in length and 2 cm. in outside diameter was used for the fractionation. The submitters state that they have also used a column of similar dimensions, packed with glass helices, for a fractionation at atmospheric pressure. They recommended the Vigreux column under reduced pressure, as used by the checkers. 

The column consists of a glass tube of 13-14 mm. internal diameter, 24 cm. long from lower end to the side arm, which has an internal diameter of 7 mm. It is important that these dimensions be observed in order to avoid polymerization of the product. It has been found in checking that better results are obtained by making indentations in the tube at frequent intervals and at different angles these tend to reduce the number of cinnamic acid particles which are carried over with the vapor. A column of the Vigreux type would no doubt also be suitable. 

The checkers employed a modified Widmer column1 (Fig. 4) that has been used in many organic laboratories, but not officially described. They also used a Vigreux column (50 cm. effective length, 2.7 cm. inside diameter) the first distillation then required ninety minutes, and the yield was 82-83 Per cent. The final temperature of the reaction mixture and observed boiling point will depend upon the type of apparatus used. 

A 60-cm. column of the Vigreux type, with heated jacket and partial reflux head, was found satisfactory by the checkers. Ethyl stearate may solidify in the condenser if a total reflux head is used. Refractionation of the fore-run gives an additional 30 40 g. (10-13%) of pure product. Material containing a few... 

The submitter used a 65-cm. Podbielniak type column equipped with partial reflux head.6 For distillation of the sodium-treated phenanthrene the checkers employed a 6-in. Vigreux column. For the fractionation of the dihydrophenanthrene, the checkers employed a 15-cm. spinning-band column obtainable from Nester and Faust, Exton, Pennsylvania. 

The submitters used a 24-cm. jacketed Vigreux column for this distillation. The checkers used a simple type of Podbielniak column, 50 cm. in length, with heated jacket and partial reflux head after the last of the benzene had been distilled through the column, the following fractions were received ... 

Figure 6. Block drawing of the pilot installation for the production of trichloromethyl chloroformate by exhaustive photochlorination [39] 1 Dryer for gaseous Cl2 (H2S04 cone.). 2 Safety tank. 3 Thermoregulated immersion-type photochemical reactor. 4 Raschig column. 5 Cl2 detection system (1,2,4-trichlorobenzene). 6 Neutralization tank (20% NaOH). 7 Reservoir of 20% NaOH. 8 Buffer to atmospheric pressure (20% NaOH). 9 Active carbon filter. 10 Reservoir of crude trichloromethyl chloroformate. 11 Buffer to normal atmosphere via CaCl2 filter and direct entry for trichloromethyl chloroformate to be distilled. 12 Distillation flask with Vigreux column. 13 Exit to vacuum pump. 14 Solid NaOH filter before pump. 15 Cooling water alarm linked to power supply of the light source. 16 Medium pressure mercury arc. 17 Heater for distillation apparatus. 18 Magnetic stirrers. /T thermometer /P manometer.

Materials. Granular Globe Pearl corn starch (Globe 3005 water content about 10%) was from CPC International. Acrylonitrile (Eastman practical grade) was fractionated at atmospheric pressure through a 15-in. Vigreux column, and a center cut was collected. Ceric ammonium nitrate was Fisher certified ACS grade. PAN homopolymer was Polymeric Acrylonitrile Type A from DuPont. 

The submitters used an 11-cm. Vigreux column the checkers employed a 10-in. column of the same type. 

The rate of heating depends on the type of Vigreux column used, in this case a 20-cm, silver-plated Vigreux column with 4-cm outer and 1 1/2-cm inner diameter. The bath temperature should not be raised above 110°C when using this type of column, to avoid co-distillation of nitromethane (bp at 760 mm, 101°C). Ethanol should be distilled off at a rate of about 10 drops/min. 

The most commonly used types of columns are plate columns, Vigreux columns, packed columns (packed with such materials as Raschig rings, Berl saddles, fibrous glass etc)... 

Many types of fractionating columns have been designed. However, most of these have proved relatively inefficient, and the principal types presently in use are the Vigreux, bubble-cap, packed, spinning-band, and concentric-tube. Each of these will be considered in turn. 

The submitter used an insulated column with a 38 by 1.1 cm. section packed with H-in. copper helices made of No. 26 B S gauge copper wire. He states that a column packed with glass helices is unsatisfactory. The checkers used a 100 by 1.7 cm. Vigreux column. Either type of column shorfld be equipped with a total condensation, partial take-off head. 

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