Small-Scale Continuous Liquid-Liquid Extraction at Superatmospheric Pressures SIR: Continuous extraction of 1 to 25 ml. of aqueous solutions in order to remove organic chemical solutes has sometimes proved to be a useful analytical tool ( I ) . The method fails when the partition coefficient is distinctly unfavorable. The apparatus described here improves such an unfavorable partition coefficient by operation a t pressures of 16- to 17-pound gage or higher. The increased boiling point of the liquids in the system under these conditions permits operation in what may be a more favorable temperature range. Furthermore, volatile gases (such as ammonia) which tend to decrease ionization of organic amines can be retained in this apparatus and thus also may improve the partition coefficient.
apparatus. After extraction is considered to be complete t h e apparatus is cooled and the pressure released. The tip of A is then broken (the illustration shows this tip after i t has been shortened by much use) and the extract is forced over and out of the apparatus. If completeness of extraction is to be tested, a fresh lot of chloroform may then be sucked in, after which t h e tip is sealed and the extraction continued. The size of this apparatus has been reduced by half in order to utilize smaller volumes and higher working pressures of air or ammonia. The drip cup on the smaller apparatus has only four tips symmetrically placed. I n either case the drip cup and tube C should be equipped with small holes at the top, so that they can be removed from the apparatus by a wire hook.
The apparatus illustrated serves to extract 40 to 45 ml. of aqueous solution when the outside containing tube is 30 mm. in inside diameter by 350 mm. long. The aqueous solution is retained over a layer of chloroform in tube C, which is 25 mm. in inside diameter by 195 mm. long. It is equipped with a tube 4 mm. in inside diameter, which is insealed 50 to 100 mm. from the top (depending on the density of the aqueous solution t o be extracted) and reaches as close to the bottom as possible. Inserted loosely into this aqueous solution reservoir is a cup 20 mm. in inside diameter by 35 mm long, to which arc sealed qeven small tips which terminate in openings 0.5 mm in inside diameter. A largcr number of tips is disadvantageous, as the chloroform which drips through them tends to accumulate unless the spacing is adequate. This is especially true when the density of the aqueous solution is near that of chloroform. The aqueous solution holder, C, is supported out of the boiling chloroform reservoir a t the bottom of the outside container bv a glass rod 8 mm. in outside diameter, which is trifurcated a t its bottom to permit free passage of chloroform through the capillary tube, A . Three indentations (not shown) in the outside container may be used to center C, but they are usually not necessary if the cold finger condenser a t the top of the apparatus is inserted 80 that its tip extends into the cup. As the indentations may tend to weaken the pressure resistance of the outside container, they may well be avoided. The cold finger is retained by a rubber stop er which is securely wired against pressure around the flange a t t l e top of the outside container. Below this flange is sealed an 8- to 10-mm. side arm t o which are attached the pressure source and a suitable gage. During operation the lower end of the apparatus is inserted into a heating bath in order t o boil the chloroform up past tube C, which it heats, and then up to the condensing surface, from which it drips through the aqueous solution and thence out of the insealed tube back into the pool of chloroform a t the bottom of the
LITERATURE CITED
(1) Wayman, M.,and Wright, G. F., IND. EXG.CHEM.,ANAL.ED.. 17, 55-6 (1945).
I;
University of Toronto Toronto, Canada
W. J. CHUTE GEORGE F. WRIGHT
Subgroup of North Jersey Section The third meeting of the -4nalytical Subgroup of the S o r t b Jersey Section, AXERICAS CHEMICAL SOCIETY, v, ill be held February 9 a t 8 P.M. a t the cafeteria of Eimer & Amend, GreenFich & Morton Sts., S e w York, N . Y. The speaker Kill be Harvey Diehl, Iowa State College, who nil1 discuss organic compounds as analytical reagents. P ~ i o rto the meeting there will be an inspection tour of the Eimer & Amend plant a t 5 p . x , followed by dinner in the cafeteria a t 6:15 P X Those wishing to attend the dinner as guests of Eimer & Amend should make reservations with A1 Steyermark, Hoffmann-LaRoche, Inc., Sutley, N. J., not later than February 1.
Fourth Annual Analytical Symposium. Hotel William Penn, Pittsburgh, Pa., January 20 and 21, 1949. Metropolitan Microchemical Society of New York. American Museurn'of Natural History, New York, N. Y., February 25 and 26, 1949. Second Symposium on Analytical Chemistry. Louisiana State University, Baton Rouge, La., March 2 t o 6, 1949. Second Annual Summer Symposium on Analytical Chemistry. Wesleyan University, Middletown, Conn., June 24 and 25, 1949.
Fourth Instrument Conference and Exhibit. Municipal Auditorium, St. Louis, Mo., September 12 to 16, 1949.
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