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 At this point the distillation capillary is quickly withdrawn from the receiving ca illary by means of a glass rod supporting the curved part of the $stillation capillary, and the bulb is quickly placed in the solid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
VOL. 11, NO. 8
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 an 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).
