Reflux adjustment

The distillate is cooled to about 0° and washed three times with 50-cc. portions of concentrated sulfuric acid cooled to o it is then shaken with 25 g. of anhydrous potassium carbonate until the odor of hydrobromic acid disappears. It is distilled through a i-m. fractionating column at atmospheric pressure, collecting the portion boiling at 91-93 °/76o mm., 88.s 90.5°/728 mm., or under reduced pressure through a 70 x 2-cm. total reflux, adjustable take-off, adiabatic column (Note 3), b.p. 41-43 /i3S mm. The product weighs 525-570 g. (55-60 per cent of the theoretical amount) (Note 4). 

If suitable contact of the liquid potassium chloride and gaseous sodium is maintained, all the potassium can be extracted from the potassium chloride. Proper reflux adjustment assists in maximum utilizations of the potassium chloride, and separation of potassium and sodium in the fractionating section. Reflux ratios are easily regulated by adjusting the electromagnetic pump which returns a portion of the product to the column. Potassium of 99.5+% purity can routinely be produced at a rate of approximately 200 pounds per hour. Any desired mixture of sodium and potassium can be produced by controlling the column operation. 

Scheme J. This scheme directly adjusts the column material balance by manipulation of the distillate flow. The main advantage of this scheme is that it has the least interaction with the eneigy balance. In terms of a McCabe-Thiele diagram, this means that the slopes of the column operating lines can be held constant in spite of energy balance upsets. This independence ftom energy balance upsets is achieved by the scheme s ability to maintain a constant internal reflux even for variations in external reflux subcooling. When the temperature of the external reflux varies, the external reflux adjustment to maintain accumulator level offsets temporary internal reflux variations. If the accumulator level loop responds rapidly, the dis-tuibanoe will not propagate down the column, and the column s overall material balance remains undisturbed.

Fig. 23(C) shows a reflux assembly with a stirrer fitted. The stirrer A is both held in position in the tube B and allowed to rotate freely by the lubricated rubber sleeve C, as described on p. 39, and is connected to a vertical motor above. The extent to which the stirrer dips into the liquid in the flask can readily be adjusted. The condenser (not shown) is fitted into D. This constitutes for many purposes the best type of stirrer. If desired, the rubber sleeve C can be replaced by a metal fitting E for a horizontal drive. The gas-inlet F is closed when not in use.

Fit a three necked 250 ml. flask with a central rubber-sleeved or mercury-sealed stirrer, c/. Fig. 23(c), p. 45, where only two necks are shown, and with a thermometer the bulb of which reaches as near the bottom of the flask as the stirrer allows the third neck will carry at first a dropping-funnel and later a reflux condenser. Place 20 g. (19-5 ml.) of ethyl acetoacetate and 45 ml. of glacial acetic acid in the flask and by ice-water cooling adjust the temperature of the stirred mixture to 5 -7° maintain this temperature whilst adding a solution of 5 4 g. of sodium nitrite in 8 ml. of water slowly from the dropping-funnel during 15 minutes. Continue the stirring for 20-30 minutes, and then... 

Reflux is more easily controlled, since careful adjustment of the... 

Improved results are also secured by the use of a short reflux condenser ( cold finger ), Fig. 11, 56, 22, inserted into the top of the column head the simplest type is shown in Fig. 11, 56, 23. The condenser permits con trol of the reflux ratio by adjusting the rate of flow of water through it. 

Resoles. Like the novolak processes, a typical resole process consists of reaction, dehydration, and finishing. Phenol and formaldehyde solution are added all at once to the reactor at a molar ratio of formaldehyde to phenol of 1.2—3.0 1. Catalyst is added and the pH is checked and adjusted if necessary. The catalyst concentration can range from 1—5% for NaOH, 3—6% for Ba(OH)2, and 6—12% for hexa. A reaction temperature of 80—95°C is used with vacuum-reflux control. The high concentration of water and lower enthalpy compared to novolaks allows better exotherm control. In the reaction phase, the temperature is held at 80—90°C and vacuum-refluxing lasts from 1—3 h as determined in the development phase. SoHd resins and certain hquid resins are dehydrated as quickly as possible to prevent overreacting or gelation. The end point is found by manual determination of a specific hot-plate gel time, which decreases as the polymerization advances. Automation includes on-line viscosity measurement, gc, and gpc. 

In a typical process a jacketed still fitted with a stirrer and reflux condenser in charged with 240 parts 37% w/w (40% w/v) formalin and the pH adjusted to 8.0-8.5 using sodium carbonate solution with the aid of a pH meter. One hundred and twenty six parts of melamine (to give a melamine formaldehyde ratio of 1 3) are charged into the still and the temperature raised to 85°C. The melamine goes into solution and forms methylol derivatives. For treatment of fabrics, paper and leather this product may be diluted and cooled for immediate use. It may also be spray dried to give a more stable product. Cooling the solution would yield crystalline trimethylolmelamine, which may be air dried but which is less soluble in water than the spray-dried product. 

The ROD is similar to a cold feed stabilizing tower for the rich oil. Heat is added at the bottom to drive off almost all the methane (and most likely ethane) from the bottoms product by exchanging heat with the hot lean oil coming from the still. A reflux is provided by a small stream of cold lean oil injected at the top of the ROD. Gas off the tower overhead is used as plant fuel and/or is compressed. The amount of intermediate components flashed with this gas can be controlled by adjusting the cold loan oil retlux rate. 

The tower operates in the same manner as a condensate stabilizer with reflux. The inlet liquid stream is heated by exchange with the gas to approximately 30 F and is injected in the tower at about the point in the tower where the temperature is 30 F. By adjusting the pressure, number of trays, and the amount of reboiler duty, the composition of the bottoms liquid can be determined. 

Primary Chlorides Dry sodium cyanide (30 g, 0.61 mole) is added to 150 ml of dimethyl sulfoxide in a flask fitted with a stirrer, reflux condenser, dropping funnel, and thermometer. The thick slurry is heated on a steam bath to 90° and the steam bath is then removed. The halide (0.5 mole of monochloride or 0.25 mole of dichloride) is slowly added to the stirred mixture, causing the temperature to increase immediately. The rate of addition should be adjusted so that the temperature of the reaction does not go above about 160°. After all the halide is added (about 10 minutes) the mixture is stirred for 10 minutes more, or until the temperature drops below 50°. In the preparation of mononitriles, the reaction mixture is then poured into water, and the product is extracted with chloroform or ether. The extract is washed several times with saturated sodium chloride solution then dried over calcium chloride, and the product is distilled. 

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