1578
ANALYTICAL CHEMISTRY
S.,Helrr. Chim. A&,
20, 927 (1937)l modified with a novel and easily adjusted solvent return. It is illustrated by front and side photographtphs and conmats of the followingparts:
Chamber A containing the solution to be extracted (approximately 8GUmi. volume in extractor illustrated); solvent vapor path, B (approximately 18mm. tubing); standard-taper joints, C and D, for connecting solvent distillation flask and reflux condenser; and extract return assembly, E . E is constructed of 8. pm. tubing except for parts laheled F, which are of IC-mm. tubing. A bulb a t C along with the larger diameter tubing for F eliminates the possibility of the solution in A siphoning into the solvent flask attached to C. H of the SOlUtiOn return pivots on l8/9 ball and socket joints a t I.
separatory funnels. Chloroform is steroids and its specific gravity is high tiou in COntinUoUS extractors, but o boiling point it cannot be used for stei _._"___ ___" tion by heat. Extractors available fc. _"._ suffer from various shortcomings. In the extractor of Cohen (1) the same batch of solvent is rc-used and an equilibrium, depending on the partition ratib between urine and solvent, is eventually attained. The extractors of Cook and Rooks (e) and of Robinson and Norton (6) are not automatic, and tlmt of Dobson and Randall ( 5 ) involves flash evaporation of the urine extract. A modified Hershberg-Wolfe extractor (4), used in this laboratory, operates under reduced pressure and permits the u ~ ofe relatively high bailing solvents for the extraction of heablabile substance8 from aqueous solutions.
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The extractor is evacuated by way of a three-way stopcock, C, connected to theeondenser througha45/50 T joint. Chloroform in the 1-liter round-bottomed flask, B, is boiled in a water bath, heated by the immersion heater, M. The chloroform vapors pass through a bole, E, in the condenser. Water, cooled by the refrigerating unit, K , is forced through the condenser coil by the circulating pump, J. The condensed chloroform trickles through the pores of the fritted disk, A , extracts the urine, and passea through D back into B. Vacuum is supplied by the vwuum pump, N , which is connected through the Cartesian manostat, H , manometer, 0, stopcock, F, and dry ice-acetone trap, L, t o C. More than one extractor can be operated on the same vacuum system.
I n operation a flask containing the extraction solvent is a& tached t o C and heated to boiling. The solvent vapors ascend throuzh B to condenser attached to D. The condensate falls
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boiling flask. K is pi&ed'to a position on the hall and socket joints, where the extract pressure in the return balances the aqueous solution pressure in A and just permits overflow a t
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The stopcock in the extract return may be closed when filling chamber A . This prevents the aqueous solution from rising in the return before extract is collected at the bottom of A . (If solvent is allways added to A before the aqueous solution is added, this stopcock may be eliminated.) The apparatus described is truly universal and within a single piece of easily adjusted equipment is flexible with respect to the volume of solution extracted and the choice of an extracting solvent more dense than water. Furthermore, the apparatus may be constructed with only moderate skill in glass blowing. This equipment has been used extensively in this laboratory for continuous extractions with methylene chloride.
Modified Hershberg-Wolf Extractor. Erich Heftmaun and David F. Johnson, National Institute of Arthritis and M e t e bolic Diseases, Bethesda, Md.
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solvent extraction is widely used for the of urinary steroids because it minimizes emulsion formation and expomre to acid, and gives better yields than shaking in ONTINUOUS
For the extraction of urinary oorticoids 1 liter of urine, ad,iusted to pH 1.0, and 100 ml. of 20% (w./v.) barium chloride solution are Dlaced io the extractor with enough chloroform (ea. 500 ml.) so that the urine level is junt above aisk A . About 500 ml. of chloroform is placed in boiling flask B, water at 7' is circulated through the condenser coil, m d a vacuum of 193 2 mm. of mercnrv is aDDlied. The water bath around the boiline flask is keDt aC42' 3'. Chloroform then boils at, 38' and D&olates
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emulsions are practically ahsent. LITERATURE CITED
L.,J. Lob. Clin. Med., 36, 769 (1950). (2) Cook,E. R.. and Rooks, M. E., Awlgat, 77,274 (1952). (3) Dobson, F., and Randall, S. S., Biochm. J.. 49,399 (1951). (4) Hershbw, E. B., and Wolfe. J. H.,J. Biol. C h m . , 133, 667 (1) Cohen, 6.
(1940).
(6) ~
~ (19511.
bA, M,, i ~and ~i.qorton, ~ J~, M,, , J , EM,+
7, 321
