ANALYTICAL EDITION
250
Vol. 5, No. 4
drawn parallel to F and Kza from the point A = 0 to the point of intersection of the line from F = 0 to K ~ = L 82.1 (the K2.6 value for pure acetic acid). This A line is calibrated upward from 0 to 100. The point P = 0 is located at the oint of intersection of the lines, F = 0 t o K26 = 82.1, and i t . 5 = 84.5 to F = 100. The line P is drawn parallel to KU to intersect the diagonal, F = 0 t o K ~ = s 58.8. The line is calibrated downward from 0 to 100. The A', P', and KIOO lines are located in the same manner. Some convenient unit of division is selected for the Kloo line. The length of line is then measured off from Klo0 = 27.2 to 63.5 = 27.34 units. The line is then located so that the upper end just meets the diagonal extended through P = 0 and Kta = 84.5. The extremities of the A' and P' Iines are then located in the same manner as those of A and P.
used instead of 4/45. The titrations must be done with extreme accuracy. I n the hands of a careless worker, errors may easily arise which would indicate the presence of 5 or 10 per cent of some foreign acid. The pipets and burets should be carefully standardized. All water used should be free from carbon dioxide. The method is rapid and reasonably accurate if properly executed. I n using the qualitative scheme devised here, it is advisable to ignore differences in K ~ OofO less than 0.4 units, which would indicate the presence of approximately 3 per cent of lactic or butyric acids, or 1 or 2 per cent of valeric acid. If the Kloo values are appreciably different from each other, it would be well to check the determinations before spending much time trying to identify any contaminating acids which DISCUSSION may be present. The scheme should be used with judgment. The method of analysis given is based on an approximately Unfortunately no clue will be given as to the nature of any 0.03 N acid solution as a matter of convenience. At least contaminating acids which may be encountered, If signifi2000 cc. of steam distillate must be collected in order to drive cant quantities of such acids are indicated, it is advisable all of the volatile acids over. Usually such a quantity of to take 500 cc. of the solution, distill off 250 cc., and make liquor can be used as to give 2 liters of 0.03 N acid distillate, a new set of determinations on the residue. If the conand the analyses can be made without further treatment of taminating acids are more volatile than propionic acid, the the distillate. two Kloo values will be closer together than they were before, since the impurities distill out faster than do the three acids TABLE IV. DETERMINATION OF ORGANIC ACIDS AT DIFFERENT under consideration. If such an acid as lactic is the conCONCENTRATIONS taminant, the Kloo values will be more divergent than they -ACIDS TAEHINACIDSFOUNDwere before. The ultimate identification, of course, would NORMALITY Formic Acetio ProDionio Formica Acetic Proponic involve the preparation of a derivative. % % % % % % I
25.0 25.0 24.0 0.lb 25.0 50.0 33.3 33.3 32.0 33.3 0.06 33.3 33.3 33.3 33.3 0.06 33.3 33.3 33.3 33.3 34.5 0.02 33.3 33.3 20.0 33.3 21.3 0.015 33.3 66.6 20.0 33.3 20.8 13.3 0.0150 66.6 30.0 20.0 31.4 20.0 50.0 0.020 30.0 20.0 29.5 50.0 0.020 20.0 33.3 33.3 34.5 33.3 0* 020 33.3 Actual amount of formio aoid present, n o determination made. b One-half volume each of ether and acid taken. c Double volume each of ether and acid taken.
51.0 35.0 33.3 32.2 65.2 66.0 48.6 60.5 32.2
@
The effect of concentration of the acids on the determinations is shown in Table IV. Apparently the method holds reasonably well for the ranges of concentration given, but is recommended only for 0.03 N acid, especially for the provisional detection of contaminating acids. More accurate results could be obtained with 0.1 N acids if the method were adapted to that concentration, because larger titration figures could be used-for example, there would be less experimental error involved if figures such as 40/50 could be
LITERATURE CITED (1) Auerbach, F., and Zedin, H., 2. physik. Chem., 103, 161-77 (1922). (2) Dyer, D. C., J . Biol. Chem., 28, 445-73 (1917). (3) Heck, A. F., Soil Sci., 28, 225-32 (1929). (4) MoNair, J. Am. Chem. SOC.,54, 3249-50 (1932). ( 5 ) Olmsted, W. H., Whitaker, W. M., and Duden, C. W,, J. Biol. Chem., 85, 109 (1929). (6) Osburn, 0. L., and Werkman, C. H., IND.ENCI. CHEM.,Anal. Ed., 3, 264 (1931). (7) Ibid., 4, 421 (1932). (8) Truog, E., IND.ENG. CHEM.,7, 1045 (1915). (9) Tsiropinas, F., Ibid., 9, 1110-11 (1917). (10) Werkman, C. H., Ibid., Anal. Ed., 2, 302 (1930). (11) Werkman, C. H., Iowa State College J . Sci., 4, 459-64 (1930). (12) Ibid., 5, 1-3 (1931). (13) Ibid., 5, 122-5 (1931). RECEIVEDFebruary 3, 1933. Journal Paper B96 of the Iowa Agrioultural Experiment Station, Ames, Iowa. Project 67.
Gas Bubbler for Very Small Pressure Drops C. C. FURNAS, Department of Chemical Engineering, Yale University, New Haven, Conn.
I
T IS frequently necessary to have a gas absorber which will operate with a small pressure drop in the gas stream and yet have a small gas volume in the system. Such is often the case where thermal conductivity cells are used for gas analysis. I n such cases, in order to prevent time lag in the analysis it is essential to keep the volume of gas in the apparatus down to a minimum. This rules out the use of solid absorbent towers. If, in addition to the small gas
FIGURE 1. INCLINED ABSORPTION TUBE
volume requirement, it is necessary to have only a small pressure drop through the apparatus, it is frequently difficult to get efficient absorption of one of the gaseous constituents. By using a large glass cylinder nearly filled with liquid, placed on a slight incline, it is possible to obtain sufficient contact between gas and liquid for efficient absorption and the static head to be overcome can be kept very small. The apparatus shown in Figure 1has been found very satisfactory when filled with potassium hydroxide for absorbing carbon dioxide from gases containing 1 to 90 per cent with a gas velocity up to 50 cc. per minute. It has also proved satisfactory when filled with concentrated sulfuric acid for absorbing water from gases saturated at 25" C. RECEIV~D March 27, 1933.
