Improved Extractor for Monaamino Acids D. W. WOOLLEY, University of Wisconsin, Madison, Wis.
T
HE extraction of monoamino, monocarboxy amino acids from
neutral aqueous solution with butyl alcohol (1) has been shown to be useful in the isolation of these compounds. One difficulty has been that because of the relatively high temperature required to boil the butyl alcohol, some of the amino acids are converted into their anhydrides. While this difficulty has been partly overcome by reducing the pressure in the extractor, the amino acids which precipitate in the boiling flask adhere to the walls and consequently are still subjected to rather elevated temperatures. The apparatus shown in the diagram eliminates this difficulty, for as the amino acids crystallize in the modified boiling flask, they settle to the bottom of the tubular part where they remain a t room temperature. Since the capillary extends only to the bottom of the heated zone, the lower layer of liquid is not stirred and the extract remains quiescent. Suction from a water pump is applied a t the top of the condenser and is regulated by adjusting a screw clamp on b piece of rubber tubing attached to a side arm a t the top of the condenser. The temperature of the boiling butanol is about 50" C. With this extractor no amino acid anhydrides could be detected in the extract. While this apparatus was developed primarily for the extraction of amino acids, it undoubtedly would be useful wherever it is necessary to extract heat-labile substances from solution with an immiscible solvent.
Literature Cited (1) Dakin, H. D., Biochem. J.,12, 290 (1918)
U
RECEIVEDJune 29, 1937.
Reaction 'of Alcohol-Gasoline Blends to the Doctor Test w. K. McPHERSON
AND LEO M. CHRISI'ENSEN,
The Chemical Foundation of Kansas Company, Atchison, Kan.
0
NE of the common qualitative methods for detecting the presence of mercaptans in motor fuel is the doctoi test. The chemistry of this test has been reviewed by Wendt and Driggs (4) who summarize the reactions as follows :
TABLEI Denaturants: Gasoline
Sweet Sweet Sour Sour Sour Sour Sour Sour
+
2RSH f NanPbOl+2NaOH Pb(SR)2 Pb(SR)s Jr S + PbS 4- (RS)a
That other reactions occur was recognized by Hallett and Sowers (3). Peroxides are known to affect the reaction
a1cohol alrohol alcohol alcohul alcohol
(2J3)*
The commercial distribution of alcohol-gasoline blends led to reports that these fuels give a sour reaction in this test very similar to that obtained with mercaptans or peroxides. In view of these reports a series of tests was made on various substances which are commonly used as denaturants for ethyl alcohol, ethyl alcohol itself, and ethyl alcohol in blends with gasoline. The results of these tests are given in Table I. All blends of gasoline with 40 per cent or more ethyl alcohol show a sour reaction. I n view of these results it is recommended that the A. S. T. M. methods be used for the determination of sulfur in alcohol-gasoline blends. If a qualitative test for mercaptans is necessary, the presence of these interfering substances must be taken into account. The authors have not
sweet sweet sweet Sweet sour
studied these reactions further, since the test is not quantitative and is not generally accepted (1).
Literature Cited (1)
-b. Boo. Testing Materials, Committee D-2, A. S. T. M. Standards on Petroleum Products and Lubricants, pp. 289-97 (1936).
(2) Brooks, B. T.,IND.ENG.CHEM.,16, 588 (1924). (3) Hallett, R. L., and Sowers, W. H., Petroleum &no., I (8), 78-81 (1 axn) \-I"Y,. (4) Wendt, G. L.,and Driggs, S. H., IND. ENO.CHEM.,16, 1113 (1924).
RECEIVIUD July 23,1937.
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