JAXUARY 1.5, 1938
ANALYTICAL EDITION
features, because it is inexpensive and not too difficult of construction, but chiefly because it has proved very reliable and requires very little attention in operation. The auxiliary parts of the system, such as receiving bulbs and storage vessels, are also shown in the diagram. The completed system is all-glass and vacuum-tight. I t operates as a closedsystem partial-condensat ion column. The condenser is double-walled. Within the inner tube copper shot and sheet furnish a heat capacity. In this is embedded a copper tube for the admittance of liquid air, nhich is supplied from a 5-liter container by means of an air pressure siphon. The air is allowed to flow continuously during a distillation, but a by-pass before the liquid air container permits it to escape to the atmosphere. When the pressure in the column rises to a value for which the system has been adjusted, an electrical contact is made in the pressure regulator manometer, and an electrical circuit is closed. This brings the hammer of a relay onto the end of the air escape tube, and liquid air is then forced into the condenser. This lowers the pressure in the column, the electrical contact is broken, and the flow of liquid air stops. By this means distillations can be carried out at any desired pressure from atmospheric down, and the pressure fluctuations during operation are insignificant in regard to the operation of the device for fractional distillations. The column proper is heat-insulated by a vacuum jacket, which is silvered except, for a vertical strip left clear to permit observations of the column. The condenser head is insulated by two concentric glass tubes with an air space between and either silvered or containing a polished metal foil. Tempera-
31
tures are determined by means of thermocouples, one located in'a well at the t'op of the column and the other on the side of t,he pot. Heat is supplied by a vinding of resistance Lvire around a small extension on the base of the pot. In operation a cooled widemouthed laboratory vacuum flask surrounds the pot. In addition to the regulating manometer an evacuated closed-tube manometer is provided for pressure mesurements. . Take-off is adjusted by means of stopcocks. The receiving vessels are arranged in parallel on a manifold. One of these has a thermocouple well in it, and its stopcock is located as shown in the diagram to prevent the accumulation of grease in the bulb. Freezing points and vapor pressures are determined on samples in this vessel, which is surrounded with a heavy-Tvalled copper tube. -4 vacuum flask is placed around the copper tube, and time-temperature XT-arming curves are taken of the sample. Pressures are determined at the same time. A gas density balance (not shown in the diagram) enables the molecular weight to be simultaneously determined. The storage vessels are 12-liter flasks provided with condensing bulbs. The material is condensed in the bulb, the stopcock is closed, and the material is allowed to evaporate into the flask.
Literature Cited (1) Booth and Bozarth, IND. EXG.C m l f . , 29, 470 (1937). 12) Rose, Ibid.,Anal. Ed., 8, 478 (1936). ( 3 ) Wilson, Parker, and Laughlin, S. -4772. Chem. Soc., 5 5 , 2795 (1933). RECEIVED September 6 , 1937.
Devices for Extraction by Immiscible Liquids H. J. WOLLNER
I
AND
JOHN R. MATCHETT, U. S. Treasury Department, Washington, D. C.
N CHEMICAL technology it is frequently necessary to
scrub a solution containing one or more solutes, b y means of an immiscible solvent. The efficiency of transferring a dissolved substance from one of two immiscible solvents to the other is a function of the area of contact developed between the two liquids. The development of very large areas of contact usually requires high dispersion of one of the solvents in the other, frequently resulting in stable emulsions. This condition is further aggravated by the desire for maintaining the quantities of extracting liquid as low as possible-usually a fraction of the volume of the original solution. Where small amounts of the more viscous, solute-bearing phase are intentionally dispersed in large proportions of the less viscous (scrubbing) phase, clean partial separation generally follows when agitation is stopped. However, since it is usually desirable to maintain the extracting phase in smaller volume than the extracted phases, the above condition cannot readily be met in a n intermittent process. The device described below affords rapid and convenient means for maintaining the necessary preponderance of less viscous material, and of making any required number of extractions in a single operation. The device consists of an emulsification chamber and a settling chamber, connected b y two ducts which permit the continuous cycling of the emulsion. Of these two ducts, the first continuously bleeds the emulsified solutions into the settling chamber, where partial separation takes place. T h a t portion which has not clarified is continuously recycled through the second duct back to the emulsification chamber. The clarified extracted solution (previously dispersed phase) is bled off the separating chamber a t the same rate a t which the unextracted original solution enters the emulsification chamber from a previous reservoir.
Inasmuch as the separation is largely a function of the relative densities of the two liquids and the relative densities of the two phases may vary, it was necessary to design two modifications of the device-one for extracting solvents of lower density than the dispersed phase, and the other vice versa.
Solute-Bearing Liquids of Greater Density than Extracting Liquid The emulsification chamber, A , is provided with an efficient stirrer, driven by a high-speed motor, and so designed as to lift the solution from the bottom rather than force it down from above. Suitable baffles are provided to ensure thorough mixing of the liquids. The separation chamber, B , consists simply of a
nG C
FIGURE1
VOL. 10, NO. 1
INDUSTRIAL AND ENGINEERING CHEMISTRY
32
tube, the length and bore of which are chosen with respect to the ease of separation of the liquids involved, both dimensions being increased for liquids which do not separate rapidly. Increasing the bore of the tuhe hastens clean separation, and increasing the length provides added assurance that the partially emulsified interfacial portion will not be withdrawn should the separation, for an reason, momentarily fail to be sharp. On the other hand, it is &sirable that the volume of the tube be small in order to retain a minimum of the phase passing through. The ducts, E and F , provide a path for the circulation of emulsified material. The mixed liquids pass into the separation chamber through tube E. The portion of denser liquid (previously dispersed phase) which separates cleanly remains, and the unclarified balance is drawn back through tube F into the emulsification chamber by the action of the stirrer. The withdrawal tube, C, is arranged as indicated in Figure 1. The height of the riser is governed by the relative densities of the phases involved, and by the relative volumes of each present during an operation. The purpose of the open tube, G, is to p r e vent siphoning. By closing the tube the device may be emptied by siphoning. The feed funnel, D,may obviously be arranged in any convenient manner. Dimensions of the apparatus may be chosen with respect to the use to which they are to be put. The following have been found satbfactory: The emulsification chamber, A , is a 50.c~. round-bottomed flask, provided with indentations a t irregular intervals to act as baffles. The separation chamber, B, is made of 22mm. tubing and is 5 cm. in length. Its top is at the level of the bottom of the flask. The connecting tubes, E and F , are made of 6-mm. tubing. The withdrawal tube, C, is 5-mm. tubing. The head of the riser is 6 mm. above the center of chamber A .
indented a t irregular intervals. The separation chamber, B, is made from 22-mm. tubing and is 10 cm. in length from the bottom to the withdrawal tube, C. The connecting tubes, E and F, are of 6-mm. tubing, and are so arranged that tube E enters the separation chamber below tube F . The withdrawal tube, C, is placed just below the height to which the liquid in chamber A rises when the stirrer is in operation. A point 3 cm. above the bottom of chamber A has been found satisfactory. Stopcock G is for draining the apparatus at the completion of a run. The feed funnel, D, is arranged in any convenient manner.
B Solute-Bearing Liquids of Lesser Density Than Extracting Liquid The device is in all respects similar to that shown in Figure 1, except that arrangement is made a t C for the continuous removal of the upper layer (clarified, extracted, dispersed phase) in the separation chamber, B (Figure 2).
FIGURE 3
For smooth operation the position and speed of the stirrer within chamber A must be carefully adjusted, t o attain a thorough mixing and rapid circulation of the liquids. A constant rate of flow of feed material must also be assured and this must be so regulated as t o maintain a sharp separation of layers in chamber B. If these conditions are met the extractors will operate with very little attention. In order to provide a satisfactory flow of feed material, the device shown in Figure 3 may be used. Water drip ing from the funnel, A , into the bottle, B, displaces air a n x forces the feed material from the reservoir, D, through the tube, E , at a steady rate. Tube E rises higher than the liquid level in the reservoir when it is filled and is pro.vided with a vent to avoid siphoning. More recise control may be had by inserting a screw clamp in the rubier connecting tube, C.
FIGURE 2 Tube E crosses tube F and enters separation chamber B a t a oint slightly lower. This arrangement is not absolutely essential gut tends to allow a more complete withdrawal into the emulsification chamber, A , of the unseparated li uid mixture. A stopcock, G, is provided for the withdrawal of &e contents a t the end of the operation. When the extraction operation is finished an upper layer separates in chamber A . By continuing the stirring after all solution has passed in, this layer may be made very small. I t is recovered along with that in chamber B when the solvent has been withdrawn through stopcock G. The following dimensions have been found suitable: The emulsification chamber, A , is a 50-cc. round-bottomed flask,
Any volume of solution may be passed through either extractor. If more than a single extraction is desired the required number may be accomplished in one operation by connecting the necessary number of devices in series. Multiple extraction, with several solvents, can readily be accomplished in a single operation by setting u p an equivalent number of these devices in series. With this device it has been possible to extract 250 ml. of a saliva solution containing 15 gamma of morphine, and recover sufficient morphine to produce a n excellent crystal identification. RECEIVED September 29. 1 9 3 i
