Constant-Tempe ture High-P Laboratory Autoclave FRED J. DYKSTRA AND GEORGE CALINGAERT, Ethyl Gasoline Corporation, Detroit, Mich.
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D,which prevents s lashing of the liquid up into the reflux condenser, E. The jaclet is heated on the outside by means of strip heaters, F. Suitable connections are made in one ,flange for a liquid and catalyst inlet, G, and in the other for a hydrogen inlet, I , a blow-off valve, J , and a thermocouple, H. This latter is m?de of pure iron tubing containing an insulated constantan wire. NO sheath is used, SO that there is no lag in reading the temperature of the liquid. The fitting of the thermocouple though the flange is illustrated in the insert in Figure 1. The autoclave is rocked 20 times per minute over a 30° arc. The axis, K , is horizontal and perpendicular to the longitudinal axis of the autoclave and at its middle. The hydrogen inlet coil, L,consists of 5 meters of hard-drawn copper tubing 6.5 mm. in outside diameter and 3.5 mm. in inside diameter wound into a coil about 30 cm. in diameter. The water connections to the reflux condenser are brought back near the axis of rotation and connected to the stationary pipes by means of rubber tubing. The entire autoclave is heavily lagged with magnesia lagging, M , including two large caps Wm which are held over the ends of the tube by means of hooks, N . A 6-meter length of ordinary copper tubing, 5 mm. outside diameter, is coiled around the pressure tube within the jacket. The purpose of this coil, 0, is to permit rapid cooling of the thermostatic liquid at the end of a run, since the heavy lagging would otherwise make it necessary to wait several hours before the charge was cooled down to room temperature. The thermostatic liquid is put in the jacket through a plug opening, P, leveled at cock Q, and drained off through cock R. Its temperature is taken with the thermometer, 8. FIGURE 1. CONSTANT-TEMPERATURE AUTOCLAVE
SMALL high-pressure autoclave, particularly suited for liquid-phase hydrogenation, was described by Peters and Stanger The unit is heated electric a b and well lagged on the outside. Stirring is obtained by rocking and the connection to the source of hydrogen is by means of a coil of flexible copper tubing. This design avoids the use Of packing glands, since there are no moving Parts inside the autoclave. Equipment of Similar tYP% but smaller in size, is now available from supply houses as regular laboratory equipment. While well suited for the preparation of many compounds by hydrogenation, autoclaves of this type are not Particularly well adapted to a study of catalysts, especially active cata-
lysts. Whenever the reaction is sufficiently exothermic and sufficiently fast, the amount of heat given off will raise the temperature considerably and accurate data cannot be readily obtained regarding the activity of the catalyst. Furthermore, in cases where either the compound being hydrogenated or the hydrogenation product is subject to thermal decomposition, and in cases where the reaction may take alternative courses at different temperatures, much better temperature control is desirable than can be achieved. with this type of autoclave. The autoclave described below retains all the advantages of the Peters and Stanger design, a t the same time permitting accurate control of the temperature, practically independently of the heat evolved during the reaction. This is accomplished simply by surrounding the reaction tube with a jacket filled with a suitably chosen liquid, which is kept at its boiling point.
DESCRIPTION OF APPARATUS The autoclave (Figure 1) is made of a 122-om. length of seamless steel tubing 50 mm. in inside diameter and 75 mm. in outside diameter, A . This tube is closed at both ends by means of a steel flange, B, and a lens connection of the classical type. A jacket, C, made of standard 5-inch (12.5-cm.) pipe and fittings, is welded to this tube. The jacket is surmounted in the middle by a dome, 383
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FIGURE 2. COMPARISON BETWEEN NEWAND OLD MODELSOF AUTOCLAVES
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This unit has been used a t temperatures up to 280" C. and pressures up to 218 atmospheres. Most of the work was done a t 150" C. and 68 atmospheres pressure using a mixture of ethylene glycol and water as the thermostatic liquid. Under those conditions 1 liter of furfural in the presence of 40 grams of copper chromite catalyst, regardless of activity, can be hydrogenated, maintaining the temperature of the reacting liquid constant within 2" C. a t an equilibrium temperature just above the temperature of the thermostatic bath. The equilibrium temperature is maintained for approximately 70 per cent of the time for the run. Figure 2 demonstrates the difference between the old and
the modified models of the Peters and Stanger type of autoclave. Since no temperature equilibrium was obtained with the old type, comparison between various batches of catalyst was very difficult and of little value when applied to largescale operation in a well controlled autoclave of a different type. The long equilibrium period obtained in the new model makes comparison between various catalysts easy and reliable.
An Improved Fat-Extraction Apparatus
The joints will stand greater water pressure; therefore a greater volume of water can flow through the condenser, thus increasing the efficiency of the condensing surface. The ground joints make a close connection and there is no leakage of water. The brass unions are rigid and individual flasks have no tendency to tip.
ARTHURD. HOLMES AND MADELEINE G. PIGOTT The E. L. Patch Co.. Boston, Mass.
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ous types of apparatus for fat extraction have been d e v e l o p e d , practically all have some features which are not entirely satisfactory. After numerous tests it was found that the e q u i p m e n t best suited for the purposes of this laboratory consisted of extraction flasks equipped with glass siphon cups and copper covers fitted with a coiled blocktin condenser. This apparatus has been FIGURE 1. ASSEMBLYOF APPARATUS described in detail, i n c l u d i n g an assembly drawing, by the Joint Rubber Insulation Committee (1). During the first months that this equipment was in use the block-tin condensers for the different flasks were connected by short pieces of rubber tubing. When new, the rubber tubing was difficult to apply without an occasional slip and knocking together of the flasks, After the tubing had been used for a time, it stretched and was not sufficiently tight to prevent leakage and a consequent loss of the vaporized solvent. In order to obviate this continual inconvenience the condensers were connected with 0.125-inch ground-joint, brass unions, soldered to the ends of the block-tin condenser tubing. Figure 1 shows the fat-extraction apparatus with extraction flasks, condensers, and brass unions completely assembled. The insert shows the construction of the unions and the method of attaching them to the tubing, although it does not satisfactorily illustrate the ground joint. The advantages of using the brass unions in place of the rubber tubing are: The brass unions can be opened or closed more rapidly than a connection can be made with rubber tubing. There is practically no wear on the unions and hence no need for replacement as in the case of rubber tubing.
LITERATURE CITED (1) Peters and Stanger, IND.ENQ. C H ~ M20, . , 74 (1928). RECEIIYED March 19, 1934.
LITERATURE CITED (1) Joint Rubber Insulation Committee, J. IND. ENQ. CNEM.,9, 310 (1917). R ~ C ~ I VApril B D 21, 1934.
Preventing Bumping in Vacuum-Distillations AVERYA. MORTON Massachusetts Institute of Technology, Cambridge, Mass.
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REVENTION of bumping in vacuum distillation may be accomplished by using a flask with ground glass fused into the interior. The apparatus is easy to clean, may be used repeatedly, and is superior in some respects to other devices commonly used in the laboratory. Pyrex glass is powdered in a mortar so that the largest sizes are not more than 1 to 1.5 mm. No attempt is made to separate the powder from the larger particles. Enough of the ground glass is put into a flask to cover thoroughly the lower half of its interior surface, The flask is then rotated in a flame and the desired portion heated high enough t o soften the glass and cause the particles to become attached firmly. It is usually necessary to blow the flask a little to correct major deformations. After annealing, the flask is ready for use. Best results in distillation are secured when the coating of powdered glass is as thick as possible. Distillation is carried out in the ordinary manner using an oil bath. In place of the usual bumping a little foaming occurs which fills the upper half of the flask. After this initial activity the surface subsides at once and remains relatively quiet during the remainder of the distillation. After use the flask is cleaned in the ordinary manner with acids or organic solvents and dried. Repeated use in this manner showed no diminution in its effectivenessin preventing bumping. Re-use without cleaning is possible, but prevention of bumping is not so effective. These flasks are especially serviceable in the distillation of liquids which are sensitive to oxidation from the current of air which is frequently used. They are far superior to the common ebullator tubes. RECEIVED June 20, 1934.
