SEPTEMBER 15, 1936
ANALYTICAL EDITION
Acknowledgment The author is grateful to L. P. Hammett for his interest and helpful suggestions throughout this research.
Summary The titration of chloride ion with mercuric nitrate solution using diphenyl carbazide indicator has been found to give accurate results in a definite range of acidity. A probable explanation is given. Mercuric oxide may be used as a primary standard in the preparation of mercuric nitrate solutions. With the method given above, the accuracy of the method is better than 0.3 per cent with ordinary volumetric apparatus.
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Literature Cited Dubsky and Trtilek, Mikrochemie, 12, 315 (1933). Ibid., 15, 302 (1934). Dubsky and Trtilek, 2. a n d . Chem., 93,345 (1933). Heller, Ann., 263,274 (1891). (5) Incze, 2. anal. Chem., 56, 177 (1917). (6) Kolthoff and Sandell, "Textbook of Quantitative Inorganic Analysis," pp. 449-56, New York, Macmillan Co., 1936. (7) Kolthoff and Van Berk, 2. anal. Chem., 71,339 (1927). (8) Slotta and Jacobi, Ibid., 77, 344 (1929). (9) Slotta and Muller, Chem. Fabrik, 7,380 (1934). (10) Trtilek, Collection Czechoslov. Chem. Communications, 5, 302 (1933). (1) (2) (3) (4)
June 18, 1936. RECEIVED
Special Head for Iijeldahl Distillation Apparatus CHAS. E. WEAKLEY, JR. West Virginia Agricultural Experiment Station, Morgantown, W. Va.
U
NITS for Kjeldahl distillations usually are so constructed as to require a glass connecting bulb of some description to connect the flask with the condensing apparatus. Theoretically this setup is all that can be desired, since the connecting bulb holds back any spray from the boiling liquid and breaks up any foaming which may occur. However, the flasks have nothing to hold them securely in place other than a rubber connection a t the top, and most distillations of this kind do some bumping. Figure 1 shows a modified Kjeldahl distillation apparatus which has been successfully used in this laboratory. It consists of a well-known manufactured unit with the addition of special metal heads to take the place of the usual glass connecting bulbs. Figure 2 is a cross section of the head and is self-explanatory. The block-tin condenser tube which comes with this particular apparatus is the right length to be soldered into the head and should extend to within 2 or 3 mm. of the top (soldered cap). These heads are held securely in place by a strip of wood 32 mm. (1.25 inches) wide, sawed off longitudinally through the centers of the 32-mm. (1.25-inch) holes in which the heads are placed. A long screw between each two heads and a t the ends holds them securely in position after they are adjusted properly for height. The wire gauze and glass beads completely break up and return to the flask any spray or foam which may occur. The operation of the unit is very simple: The rubber FIQURE2. KJELDAHL DISTILLATION HEAD (All dimensions in millimeters)
stopper is pushed t o the top of the lower tube, the 800-cc. Kjeldahl flask put in position, and the stopper pushed down with a twist into the neck of the flask, holding,it tightly. Figure 1 also shows supports for the receiving flasks which are very convenient, especially in adjusting the delivery tubes to the proper depth in the acid. If these tubes are made sufficiently large (inverted filter tubes serve nicely) and are kept just under the surface of the acid, there will be no danger of acid sucking up into the condensers because of uneven heating. REC~IVED May 21, 1936. Published with the approval of the Director, West Virginia Agricultural Experiment Station, as Scientific Paper
FIQURE1. MODIFIED KJELDAHL DISTILLATION APPARATUS
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