AUGUST 15, 1939
ANALYTICAL EDITION
Anthraquinone-2,6-disulfonic acid interferes and is estimated together with the 1,8-acid. The method might be developed for mixtures containing 2,6-acid in the presence or absence of l,8-acid. Anthraquinone-2,7-disulfonic acid and anthraquinone-2-sulfonic acid may cause low values for the 1,s-acid. It might also be possible to develop a method for the estimation of anthraquinone-1-sulfonic acid in the preselm? Of anthraquinone-2-sulfonic acid, based upon the principle described.
469
Literature Cited (1) Coppens, f i e c , trav. chim., 44, 907 (1925).
(2) Fierz-David, et at., Helv. Chim. Acta, io, 214 (1927). (3) L a w , J. prakt. Chem. (2), 13% 190 (1931). (4) Mew-, Hans, “Nachweis und Bestimmung organischer Verbindungen,” p. 362, Berlin, Julius Springer, 1933. ( 5 ) Ullmann and Kert6ss, 52, 548 (1919), (6) Waldmann, Dissertation, Prague, 1927. PRESENTED before the Division of Microchemistry at the 97th Meeting of the Amerioan Chemical Society, Baltimore, Md.
A Distillation Capillary A. 0. GETTLER AND J. FINE Washington Square College, New York University, New York, N. Y.
IXTURES of low boiling liquids, in volumes as small as 0.02 t o 0.1 ml., can be fractionally distilled by meang of the apparatus described below.
Preparation of Distillation Capillary A piece of Pyrex glass tubing, A, about 8 mm. in outside diameter, and with 1-mm. n-all, is heated in the blast lamp and drawn out to a capillary, B, somewhat longer than 10 cm., with a uniform inner bore of approximately 2 mm. A 10-cm. section, G, of this capillary is cut off. About 5 cm. from one end, the capillary is drawn out to a much finer capillary, D, 0.25 to 0.5 mm. in outside diameter, and about 7 cm. long. Any excess length is cut off. The end of the finer capillary is sealed by heating in the flame.
The end of the larger capillary is then also sealed, using a small blast flame, and the glass kept soft by holding it in the flame until a hollow bulb about 5 to 6 mm. in diameter (0.06- to 0.1-ml. capacity) forms, E, owing to the increased pressure of the heated air within. The size of the bulb will depend upon the length of time that it is kept in the flame. Excessive heating must be avoided, since this will gradually enlarge the bulb to the poinb of bursting. When cool, the tip of the fine capillary is broken off, The stem of the fine capillary a t a point 1 to 2 cm. from the larger capillary is softenedbyheating in a luminous flame,and bent to an angle of about 45”, F. The distillation capillary is now ready for use. DISTILLING CAPILLARY
L
70 MM.
2 MM.
~
FIGURE 2
c I
Filling the Distillation Capillary The drop of liquid to be fractionated is introduced into the
distillation capillary in the following manner: D
The bulb of the distillation capillary is warmed by immersing for a few moments in boiling water. While the bulb is still warm, the fine capillary tip is dipped into the drop of liquid to be fractionated, and then a cooling bath (solid carbon dioxide and acetone) is applied to the bulb. The decreased air pressure within, due to the cooling, causes the liquid to flow up the fine capillary, down the larger capillary, and into the bulb of the apparatus. Should any of the liquid remain in the stem, it is easily forced into the bulb by shaking the apparatus two or three times, as is customary with clinical thermometers. For a successful distillation the bulb should not be more than half full of liquid. In order to remove all traces of adhering li uid from the fine capillary arm, the arm is carefully warmed, &le the bulb containing the bulk of the liquid is kept in the cooling mixture.
E
F
The Distillation
FIGURE 1
A test tube, 6 cm. long, partly filled with ice water is used to cool the distillate-receiving capillary. For very low boiling liquids (30” C. or less) a small Dewar flask containing liquid air is used.
VOL. 11, NO. 8
INDUSTRIAL AND ENGINEERING CHEMISTRY
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A capillary, 9 cm. long, having an inside diameter just a trifle larger than the outside diameter of the fine arm of the distillation capillary, is introduced into the cooling bath, with its sealed end resting on the bottom of the test tube. The fine stem of the distillation capillary is introduced into the receiving ca illary as far as it will go. The entire setup is held by means of tKe watercontaining test tube during the distillation. The bulb of the distillation capillary is now inserted into cold water contained in a small beaker. The water is then gradually and very slowly heated until a ring of condensate is seen rising u the column and condensing in the receiving capillary. At tgis point the flame should be at once removed, in order to keep the temperature of the water from rising too high. The distillation meanwhile is allowed to continue until a layer not more than 2 mm. thick (0.01-ml. volume) has collected in the receiving capillary. At this point the distillation capillary is quickly withdrawn from the receiving ca illary by means of a glass rod supporting the curved part of the $stillation capillary, and the bulb is quickly placed in the solid carbon dioxide-acetone cooling mixture, in order to suck back into the bulb any liquid remaining in the capillary portion of the apparatus. The receiving capillary containing this first fraction is stored in the cooling mixture until ready for identification tests, such as the boiling point determination. Fractional distillation of the remaining liquid in the bulb is then continued as described above. Not more than 2 mm. of each fraction should be collected in the receiving capillaries. Five to six fractions can be obtained in this way from 0.06 ml. of liquid.
Results Obtained by Fractional Distillation Various mixtures of low boiling liquids were prepared, and small volumes, as indicated in Table I, were fractionated by the method described. The boiling points of the several fractions were determined by Emich’s boiling point micromethod (1). The first fractions contain the lower boiling liquid, and the last fractions the higher boiling liquid, in a form pure enough to be identified by their respective boiling
TABLEI. EXPERIMENTAL RESULTS Mixtures of Liquids Used Ml. 0.02 Ethyl ether 0.02 Acetone
.
Boiling Points
of Pure Liquids
c.
34.5 56.5
Boiling Points ,o Successive Fractions Expt.
c.
1 2
0.03 Methyl alcohol
64.6
1
0.03 Methyl formate
31.5
2
0 . 0 3 Ethyl ether
34.5
1
0.03 Acetaldehyde
21.5
2
0 . 0 3 n-Propyl chloride
46.4
1
0.03 Iso-Propyl chloride
36.5
2
34.5,35.0, 49.5, 55.8 34.5,35.3,43.0,55.5, 56.0 33.0,35.5,37.0,41.5, 60.5,63.5 32.0,33.5,38.6,42.5 63.2.64.0 21.5,21.5,22.0,33.0, 34.0 21.0,21.0,22.5,33.5, 34.0 37.5,37.5,42.5,43.5, 45.0 36.0,37.0,40.5,44.0, 46.5,46.8
points. The intermediate fractions contain mixtures of the two liquids. If it becomes desirable to redistill some of the fractions, they may be introduced into the bulb of the apparatus as described and refractionated. For corroborative identification, since there is no loss of material during the boiling point determination, the liquid in the receiving capillary can be used to determine its molecular weight by the method of Niederl et al. (2).
Literature Cited (1) Emich, F., Monatsh., 38, 219 (1917). (2) Niederl, J. B., Trautz, 0. R., and Plentl, A. A., IND.ENG. CHEM.,Anal. Ed., 8, 252 (1936).
Modified Beilstein Test for Halogens in Organic Compounds DOUGLASS F. HAYMAN Merck & Co., Inc., Rahway, N. J.
T
HE well-known Beilstein test (1) for detecting halogens in organic compounds often gives positive tests for small amounts of halogen when actually none is present-for example, strong positive tests are obtained with certain types of pyrimidines, pyridines, and oxyquinolines (1). Modified tests (2,s) have been described for gases and volatile liquids. A method has been in use in this laboratory for about 5 years which accurately detects the presence of halogens in organic compounds. With experience the operator may approximate the halogen to within 20 per cent of the actual value. The test has never given positive results on any compound not containing halogen, with the exception of materials containing copper. A section of Monel metal tubing 0.9 cm. (0.375 inch) in outer diameter is heated to a cherry red color with a Bunsen burner equipped with a fishtail. The compound t o be tested is brought up to within 1 om. of the under side of the Monel tube. The material decomposes in the flame and the decomposition products are automatically swept up against the hot metal. If the compound contains halogen, a colored flare will appear which may
range anywhere between reen and blue. The approximation of percentage is made poss8.de by taking given amounts of material. The liquids are picked up on a platinum loop; the solids, on a small platinum spoon about 2 mm. in diameter.
It is necessary to learn to judge the amount of flare. Some compounds decompose very rapidly, giving one broad flare for only a n instant, while another of the same halogen content may decompose more slowly and give a narrower flare over a longer period. With experience or the aid of control samples the operator may determine the percentage of halogen to within a very practical limit, so that it is possible, for instance, to differentiate easily between a 2 and 6, 5 and 10, or 25 and 50 per cent value. The method has proved of great value where a rough quick control is desired to follow the course of a reaction. Literature Cited (1) Meyer, H., “Analyse und Konstitutionsermittlung organischer Verbindungen,” 6th ed., p. 166, Berlin, Julius Springer, 1938. (2) Ruigh, Wm. L., IND.ENG.CHEM.,Anal. Ed., 11, 250 (1939). (3) Stenger, Shrader, and Beshgetoor, Ibid., 11, 121 (1939).
