INDUSTRIAL AKD ENGINEERIISG CHEMISTRY
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has been described before ( I , 2 ) . The method previously given by the author (1) has been improved and consists in drying two weighed samples simultaneously in the regular combustion tube with heat from a Pregl drying block, and with a current of nitrogen passing through the tube. The first boat contains the sample for combustion, the nezt boat a sample weighing 15 to 20 mg. The water driven off can be determined with much greater accuracy than by the previous method. Before combustion the larger sample is removed and a carbon-hydrogen determination is made on the smaller sample, the we:ght of which has been corrected for its share of loss of weight on drying.
Determinations by the Dumas Method The special pig has been used without an inner boat for certain lumpy solids, but it has been found more convenient to weigh the material in a copper boat, which later is introduced into the combustion tube eliminating the use of a shaking bottle when the samples have a tendency t o stick to the walls.
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sity of a microbalance giving readings constant to *0.002 mg. over a period of several minutes, (2) determination of the relative hygroscopicity of a substance to find the best method of handling and weighing, (3) a new type of pig and a special technic which makes it possible t o weigh the sample and pig to 10.002 mg., (4)a revised method of handling substances which must not come in contact with the moist air even for an instant, and ( 5 ) the use of the special pig in conjunction with a copper boat for the determination of nitrogen by the Dumas method.
Literature Cited Hayman, D. F., IND.ENQ.CHEY.,Anal. Ed., 4,256 (1932). Milner, R. T.,and Sherman, M. S., Ibid., 8,427 (1936). Pregl, F.,“Quantitative Organic Microanalysis,” ed. by H. Roth. tr. by E. B. Daw, 3rd English ed., p. 54, Philadelphia, P. Blakiston’s Son & Co., 1936. Pregl, F., and Fyleman, E., “Quantitative Organic LMMicroanalysis,” 2nd ed., p. 67, Philadelphia, P. Blakiston’s Son & Co., 1930. Unterzaucher, J., Mikrochemie, 18, 315 (1935).
Summary Methods which have given satisfactory results for drying and weighing hygroscopic substances stress: (1) the neces-
RECEIVED October 20, 1937. Presented before the Microchemical Section at the 94th Meeting of the American Chemical Society, Rochester, N. Y., September 6 t o 10, 1937.
Weighing Tube for Volatile Liquids in Carbon-Hydrogen and Dumas Nitrogen Semimicrodeterminations V. A. ALUISE Hercules Pow-der Company, Experiment Station, Wilmington, Del.
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N TEFE micro- and semimicrodetermination of carbon-hydrogen and Dumas nitrogen according to Pregl ( I ) , volatile liquids are weighed in glass capillaries containing a few crystals of potassium chlorate a t one end and drawn down and sealed at the other (Figure 1). When carrying out a determination the tube is weighed, filled as usual by warming in a flame, and cooled with the long end dipping into the sample contained in a l-cc. beaker. After centrifuging briefly to force the sample into the bend of the capillary, the end is sealed and the tube is reweighed. Both ends are then broken off; the tube is placed in a porcelain boat and promptly introduced into the combustion tube with the open ends slightly elevated and facing the furnace. The U-shaped design shown in Figure 2 has been found more convenient for these determinations. By avoiding the use of potassium chlorate the filling of the capillary is simplified and the sample is expelled much more smoothly. One capillary end is longer than the other t o facilitate handling; the other end is sealed.
Literature Cited (1) Pregl, “Quantitative Organic Microanalysis,” 3d ed., tr. by E. B. Daw, p. 52, Philadelphia, P. Blakiston’s Son & Co., 1937. RECEIVEDOctober 29, 1937.
