INDUSTRIAL AND ENGINEERING CHEMISTRY
October 15, 1932
445
(5) Selvig, W. A,, Bur. Mines, Rept. Investigations 3003 (1930). LITERATURE CITED ( 6 ) Selvig, W. A., Bur. Mines, Tech. Paper 8, revised, 42 (1929). (1) Am. Soo. Testing Materials, Standards, Part 11, pp. 551-6, 1927. (2) Fieldner. A. C., Selvig, W. A., and Parker, W. L., J. IND.ENQ. RH~CH~IVED December 21, 1931. Presented before the Division of Gas and CHIDM., 14, 695-8 (1922). Fuel Chemistry at the 83rd Meeting of the American Chemioal Society, (3) Jones, M. C. K., et al., Ibid., Anal. Ed., 2, 325-8 (1930). New Orleans, La.,March 28 to April 1, 1932. (4) Remmey, G.B.,J. Am. Ceram. Soc., 14, 358-84 (1931).
Improved Distillation Trap EDWARD S. WEST,Washington University School of Medicine, St. Louis, Mo.
T
HE diagram represents a trap for use as a connecting bulb in Kjeldahl distillations which has been found superior to the ones in common use. It was originally used in a still for conductivity water and is now employed by the writer wherever an efficient distillation trap is required, It has the advantage of operating entirely without spattering and of efficiently removing fine spray from the vapors. The apparatus is easily made. I n operation, vapors pass up the inner tube, through the side holes at the end, and are deflected down through the wet narrow annular space between the inner tube and cap. The vapors again change direction a t an angle of 180 degrees and pass out between the wet walls of the cap and bulb. Condensed liquid returns to the boiling flask through a hole a t the bottom of the inner tube near its seal to the outer tube. The space between the walls of the inner and outer tubes, around and above this hole, must be sufficiently narrow to hold by capillarity a column of water which will prevent steam blowing through it. The dimensions given are satisfactory, but may be varied rather widely except that the space between the inner and outer tubes must not be too wide, nor the return hole too large, and the exit holes a t the end of the inner tube must be large enough to allow passage of the vapors a t a low pressure to prevent blowing through the return hole. Traps with practically any desired efficiency may be made by simply lengthening the inner tube and cap. This apparatus may be obtained from Arthur H. Thomas Company, Philadelphia, Pa.
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‘INNER TUBE TO HAVE 8 HOLES- 27,DIA.
I.D. OF TE~TTUBL NOT LE55 THAN 151
CE DETWELN MALLS T LE55 THAN ‘Ill, IN INNER TUBE
RECEIVED July 26, 1932
An Identification Test €or Oxalic Acid EARLER. CALEY,Frick Chemical Laboratory, Princeton University, Princeton, N. J.
SINCE
4 several carboxylic acids form more or less insoluble calcium salts, the usual calcium oxalate precipitation test for oxalic acid is not an especially distinctive means for identifying the acid, and may lead to confusion in certain instances. The following specific precipitation reaction for free oxalic acid is based upon the fact that sodium oxalate is sparingly soluble salt, whereas the normal sodium salts of practically all other known carboxylic acids are freely soluble in water. Dissolve 0.10 gram of the solid organic acid in 2.0 cc. of cold water and add 1.0 cc. of approximately 6 N sodium hydroxide solution. Shake the mixture vigorously for 1 or 2 minutes. The separation of a white crystalline precipitate indicates oxalic acid. The proportions of weights and volumes given were those found to give the optimum results in a series of experiments bearing on this point. Any marked deviations from these details may vitiate the test. The weights and volumes may,
of course, be reduced in proper proportion in case a sample as large as 0.10 gram is not available for examination. This reaction is not of value for the detection of oxalic acid in mixtures, but is intended solely as a simple identification test for the free acid in order to distinguish it readily from other solid, water-soluble, carboxylic acids. Tests made on a number of such acids using this procedure yielded negative results even when samples larger than 0.10 gram were taken. Among those examined were the following representative ones: citric, crotonic, glycollic, maleic, malic, malonic, mandelic, succinic, and tartaric. As far as the writer has been able to determine, the only carboxylic acid that will give a precipitate in the above test is dihydroxytartaric acid. However, it is not likely that confusion could arise from this source in view of the unstable character of this acid and the special means required to obtain it. RECEIVED September 8, 1932.
