ANALYTICAL EDITION
NOVEMBER 15, 1936
tion or some physical property can then be used for analysis of the fractions, if the cuts are sufficiently sharp. Since the vapor pressure ratio for isobutane-isobutene or butene-l-nbutane is approximately 1.2, i t is obvious that columns having on the order of ten theoretical plates will not be satisfactory since the enrichment factor is less than 7. However, a column like that described in this paper, but with a packed section about 90 cm. (3 feet) long, would have 30 or more plates and an enrichment factor of about 240. This would give the required sharpness and smooth operation, along with a reasonable throughput. Experience with the column described above and other experiments on fractionation in small-diameter columns (22) suggest that a t least some previously described columns, such as those referred to in the first paragraph of this paper, can be considerably improved for purposes of butane-butene distillation by modifying them as follows: 1. Use single-turn glass or wire helices as packing. 2. Relocate the thermocouple junction about 2.5 cm. (1 inch) below the bottom of the condenser. 3. Increase the heat capacity of the condenser by packing it
with lead or copper shot. 4. Sup ly liquid air t o the condenser at a constant rate by a device suegas that described above. 5. Supplement the manually controlled take-off valve by an automatic sintered-glassmercury valve (f 6).
The combined effect of these modifications will be to increase the total time required, but the equivalent number of theoretical plates will be increased a t practical rates of throughput, and irregular variations in the boiling point will be minimized because the direct transfer of heat from the thermocouple junction and its immediate surroundings is made more regular, pressure variations in the column are de-
483
creased, and effjciency of fractionation is stabilized a t a high level.
Acknowledgment The author wishes to acknowledge the suggestions and advice of M. R. Fenske and G. H. Fleming in the development of this apparatus.
Literature Cited Bosschart, IND.ENQ.CHEM., Anal. Ed., 6 , 2 9 (1934). Davis,Ibid., 1,61 (1929). Davis and Daugherty, Ibid., 4,193 (1932). Fenske, IND.ENG.CHEM.,24, 482 (1932). Fenske, Quiggle,and Tongberg, Ibid., 24,410 (1932). Fenake, Tongberg, and Quiggle, Ibid., 26,1169 (1934). Fitch, Nat. Petroleum News, 23, No. 25, 66 (1931). Fleming, G . H., personal communication. Freyand Hepp, IND.ENG.CHEM.,25,441 (1933). Frey and Yant, Ibicl., 19,492 (1927). Hunter, J . P h w . Chem., 10, 350 (1906); International Critiosl Tables, Vol. 3, p. 333. Kistiakowsky et al., J.A m . Chem. Soc., 57, 65,876 (1935). Leslie, “Motor Fuels,” p. 555, New York, Chemical Catalog Co., 1923. Lucaa and Dillon, J . Am. Chem. Soc., 50,1460 (1928). McCabe and Thiele, IND.ENQ.CHEM.,17,205 (1925). McMillan, U.S.Patent 2,005,323 (June 18,1935). Oberfell and Alden, Oil Gas J.,27, No. 22, 142 (1928). Peters and Baker, IND.ENQ.CHEN.,18,69 (1926). Podbielniak,Ibzd., Anal. Ed., 5, 135 (1933). Podbielniak, Ibid., 3, 177 (1931); 5, 119,172 (1933). Rogers and Brown, IND. ENG. CHEM.,22, 258 (1930). Rose, Ibid., 28, 1210 (1936). Schaufelberger, Oil Gas J., 29, No. 16,46 (1930). Wilson, Parker, and Laughlin, J . Am. Chem. SOC.,55, 2795 (1933). RNCEIVED July 29, 1936. Presented before the Division of Gaa and Fuel Chemistry at the 92nd Meeting of the American Chemical Sooiety, Pittaburgh, Pa.,September 7 t o 11, 1936.
Oil Acidity Pipet W. F. DAVIDSON Brooklyn Edison Company, Inc., Brooklyn, N. Y.
T
HE author’s inspection and salvaging of transformer oil often required acidity determinations of many samples. The normal procedure included the weighing of a 20-gram sample, the addition of 150 ml. of benzene-methyl alcohol solvent, and titration with standard alcoholic potassium hydroxide, using alkali blue as a n i n d i c a t o r . Evans and Davenport (1) showed this method to be superior to the contemporary tentative A. S. T. M. procedures. The apparatus described below, however, may be adapted for use in the current tentative A. s. T. M. Designation D18827T by making it with the proper capacities for oil and solvent. When there was a large number of samples the weighing seemed tedious and time-consuming. An investigation of the specific gravities of a considerable number of used transformer oils revealed slight differences, and suggested a simpler means of measuring the desired amount for analysis. At
25” C. the average weight of 23 ml. of samples from 20 different transformers was 20.041 grams. The maximum deviation from the mean was 0.133 gram. Since the probable error involved in measuring the sample by volume was considerably less than the error in titration, there could be no advantage in using the more precise weight method. A convenient way of measuring both the sample and solvent may be accomplished with the combination pipet shown in the diagram. The particular feature of this apparatus is its self-rinsing property. The oil sample is drawn into the lower pipet and the oil adhering to the outer side of the tip may be wiped off before introducing the solvent, which is drawn in until the upper pipet is filled. The oil does not mix spontaneously with the solvent, but remains in the lower part of each pipet. When the contents are drained into the titration flask, the oil is washed completely from the pipet by the supernatant solvent. The apparatus may be used subsequently without further cleansing, and contamination is negligible. The use of the special pipet in conjunction with a standard self-filling buret has reduced the time required for acidity determinations to 25 per cent of that required by the old procedure.
Literature Cited (1) Evans and Davenport, IND.ENG.CHEM.,Anal. Ed., 3, 82 (1931). RECEIVED August 29, 1936.
