February 15, 1942
ANALYTICAL EDITION
(28) Kolrhoff. I. M.,and Lmgnnr. .I. J.. "Polnromaphy". New York, Iniwrricnre Puhlid~ers. ~ w i . (29) Kolthofi, 1. 11.. and Pda. Y . D.. J . Am. C h m . Soc.. 61. %402
,-"-",.
,1070,
(30) (31) (32) (33) (34) (35) (36) (37) (38) (39)
(40) (41) (42)
(43)
(44)
Ibid.. 62, 3332 (1940). Lingane, J. J., Chon. Reo., 29. 1 (1941). Lingane, J. J., and Davis, 0. L., I . B i d . Chem.,137, 567 (1941). Majer, V.. Z . Elektrochem., 42, 120 (1936). Ibid.. 42, 123 (1936). Michaelis, L., Chem. Rea., 16, 243 (1935). M"ller, 0. H.. Am. J . Physiol.. 133, P393 (1941). MuUer, 0. H., Ann. N. Y . Aoad. SCi., 40, 91 (1940). MWW, 0. H., cam. ~ m . 24.95 , (1939). Miiller, 0. H., Cold Spring Harbm Symposia Quant. Biol.. 7, 59 (1939). Miiller. 0. H.. Collection Cmchoslw. Chm. Commun.. 6 , 269 (1934). Miiller. 0. H.. J . Am. Chon. Soc.. 62, 2434 (1940). MUer. ~ ~ 0. .~ H.. . ,J ~. . C .h m . ZdumEian., 18. fi5. 111.. 172. 227. 320 I, ,.941). These papers havebeen oombined in "The Polmogr8.Dhic Method of Analysis", No. 2 in the series of "Contributions to Chemical Eduoation", Easton, Penna., J . Chon. Edumtirm, 1941. Miiller. 0. H., and Baxmbergeer, J. P., J . Am. Chon. Soa. 61, 590 (1939). Miiller, 0. If., and Baumbergeer. J. P., Tmns. Electmchem. Soc., 71, 169 (1937). ~~
~
105
(45) Ibid.,71, 181 (1937). (46) Miillen 0. H., and Phillip%R. A., Am. J . Phttsid., 129, P426 (1940). (47) Neuberger. A., Z. a d . Chem.. 116, 1 (1939). (48) Semerano, G.. and Chisini. A,, Gau. d i m . ital.. 63, 802 (1933). (49) Shike.ta, M.. and Tachi, I., Colledkn Csechoslou. C h m . Corn, mun.. 10, 368 (1938). (50) Smith, L.I.. Kolthoff, I. M., Wsweonek, S., and Ruaff, P. M., J . Am. C h m . Soc.. 63, 1018 (1941). (51) Spalenka. M., Collection CzedLoslm. Chon. Cmnmun.. 11, 146 (1939). (52) Stackelberg, M. v., Z. Eleklmdon., 45, 466 (1939). (53) Strubl, R.. Colledion Czechoslou. C h m . Commun.. 10,475 (1938). (54) Vitek. V.. Ibid., 7, 537 (1935). (55) Waldsohmidt-Leite, E., and Mayer, K.. Z . phwiol. Chon., 261. 1 nnnn\ A I'""",.
(56) Winkel, A,, and Proske,G., B e . , 69, 693. 1917 (1936). (57) Winder, R. J., J . Cellular Comp. Physiol., 17, 263 (1941). (55) Tolfe, J. K.. Fieser, L. F.. and Friedgood, H. B., J . Am. Chem. Soo., 63, 582 (1941). (59) Wolie, J. K.. Hershberg. E. B.. and Fieser, L. F., J . Biol. Chem.. 136, 653 (1940). PBE~ENTED before the Divisions 01 Agricvltural snd Food Chemistry, Biological Chemistry. and M e d i e i d Chemistry. Symposium on New Anhlyti~alTools for Biological and Food Researah. at the 102nd Meeting of the Aurmnmm Camrrronr, SOOI~TT., Atlantic City, N.J.
Determination of the Aniline Point of Dark Petra BRUCE B . CARR AND M. S. A G R U S S , Th
T..
HE American . Society for Testing Materials has defined amhne point (1) as the minimum equilibrium solution temperature for equal volumes of aniline and oil and has pub-
lished a method for determining the aniline point by observing the temperature at which a 50/50 mixture of oil and aniline becomes turbid upon cooling. Since the use of the A. S. T. M. method is limited t o oils of less than 8 A. S.T. M. color (I), the authors have developed a method for determining the aniline point of dark oils based on the visual observation of a thin film formed on the glass wall of the apparatus. Previous investigators have observed the clouding of a thin film of aniline and oil and have made use of this principle t o determine approximate aniline points. The method described by the Institution of Petroleum Technologists (5') suggest3 that the aniline point of dark oils can usually be determined with suitable illumination or by observation of the thin film of the mixture which is washed up on the sides of the tube during stirring. Dom (8)utilized-the sharp break in the viscosity temperature curve t o indicate the aniline point, but resorted t o an approximate method for dark oils in which a drop of the hot solution was observed under a microscope. VanWijk and Boelhouwer (6) and Matteson, Zeitfuchs, and Eldredge (4) make use of the variation in transparency to infrared radiation.
Description
tus
ists essentially of a The anmratus shown in I doulilc jiiketcd Pyrex test tu1... .pie-junctiun Cnlqiere o n ~ t m t a ntlermoruuplc cemented IO the inner wall of the rube. The aniline-oil minurr i s stirred by swvinqng the apparatus bark and forth over a midl arc in such a miwncr that the contents from-one end of the tube to the other, alternately covering and cxpwinI: the thcmoeouple attidied td tlic n n l l of t h e tube. This stirring action may be neromplish~din a m n n h of n a y s ; ihe autl.ors clamped rhc apparatus to 3 vwtir4 nrm wlrich i i n i v o t ~ da t its lower rud. The a r m is mwed bwl, and forth ibont 25 times per minute by a slow-speed motor geared down
...~.. I
Nn
t o tnxs speed.
A
m a n :[-watt uant ana miem
~ s clampea e
on
of 0 t o 15 millivolts. An i n s t m e n t calibrated to 0.01 millivdt should be used if greater than 0.5" F. ac+,cy is desired. The inner tube (Figure 2) is 15 mm. m outside diameter and 125 mm. lone (not includine the standard-taDer mound-dass joint which i s sealed t o the %OD of the tube tb hold the stt,ppei-). Tlrc triple themcx.cc;uple jurietions lire brought l n t u thc ruLe through two s ~ ~ sholrj;yhich ll are locarnl about 90 mm. from t1.e bottom ui t h e t11')c. Il!e iunvtirins are remrxrrd to cover more of the tube surface and ckmented in place 6 t h air-
INDUSTRIAL AND ENGINEERING CHEMISTRY
106 220
1
I
1 FIGURE
I
3
DARK OIL ANILINE POINT APPARATUS CALIBRATION CURVE
Vol. 14, No. 2
Precision The precision of this test is limited mainly by the precision with which the potentiometer can be read, since the potentiometer reading a t which the film around the thermocouple becomes cloudy is highly reproducible. Duplicate determinations by different operators check within 0.5" F. The accuracy of the test depends largely on the thermocouple calibrations or the overall calibrations of the apparatus. The authors used constant-temperature ( * 0.025' F.) viscosity baths to ensure accurate calibrations; however, a periodic check should be made on the calibration. If the apparatus is carefully calibrated and corrected as shown in Figure 3 an accuracy of +0.5' F. should be easily attainable.
TABLE I. COMPARATIVE RESULTS Iraterial
A . S. T.M . Aniline Dark Oil Point Method
F.
FIGURE3 drying Insalute cement. The inner tube is su ported in the jacket by means of a second ground-glass standari-taper joint. The outer jacket is a double-walled tube 6 cm. in outside diameter and 19.5 cm. long, the inner surface of which is ground a t the top to form half of the ground-glass joint which supports the inner tube. The jacket is vented near the top. A short section of glass tubing (not shown in the photograph) should be attached to the outer jacket just below the clamp to aid in blowing cold air through the jacket if this is necessary. A clamp is provided to hold the apparatus on the stirring meclianism.
Kerosene Kerosene Kerosene distillate Kerosene distillate Cracked gasoline No. 3 furnace oil 85 viscosity neutral 180 viscosity neutral Blend fuel oil in neutral Blend fuel oil in neutral No. 6 fuel oil (black), operator 1 N o . 6 fuel oil (black), operator 2 Still bottoms (black) . . Black oil 700 E. P. gas oil (8 plus N. P. A . color) 20 gravity bottoms (Sweet Lake crude-black) Operator 1 Operator 2 ODerator 3 28 i r a v i t y topped crude (Koscmiinion crude-black) Operator 1 Operator 2 Operator 3
120 161 168 159 97 150
203 216 209 212
...
... ... ..
... . .
F. 120.3 161.2 168.0 158.7 07.0 149.5 203.0 216.3 209.2 "12.0 168.7 168.8 150.4 146.0 118.0 221.0 221.2 221.3 178.6 178.7 178.2
Operation
Discussion
Three cubic centimeters each of oil and aniline are pipetted into the inner test tube; the glass stopper is inserted and fastened by means of a rubber band. The apparatus is then clamped in a nearly horizontal position and the flame and stirring device are started. As the mixture is heated the inner tube should be vented at least every 50" F. The aniline point is taken as the temperature at which a cloudy film first appears on the glass wall surrounding the thermocouple junctions as the mixture is cooled from above its solution temperature. The rate of cooling should be controlled as specified in the A. S. T. M. procedure; however, when using a millivoltmeter, which may be read instantly, instead of a potentiometer the rate of cooling was found to have very little effect. The apparatus may be easily cleaned by pouring a suitable solvent into the tube and evacuating into a trap through a glass tube of small diameter. The oil sample and aniline should be prepared as described in the A. S. T. M. procedure.
The simplicity in design and construction of the apparatus makes it available a t very little cost to any laboratory which is equipped with the necessary millivoltmeter or potentiometer. In ease of operation and time consumed the method is comparablewith the proposed A. S. T. M. method for light-colored samples. The method is applicable to black stocks such as No. 6 fuel oil and most still bottoms; however, in the case of heavy tars the film may not be translucent even after 50 per cent dilution with aniline. If the solution temperature is below room temperature the aniline point may be determined by blowing cold dry air through the outer jacket, or by a method (4) involving the use of a standard diluent having an aniline point around 140' F. The aniline point of a 50/50 per cent by volume mixture of sample and diluent is determined, the aniline point of the sample then being obtained from a curve showing the relation between aniline points of oils and oil diluent blends. The aniline point of very black samples could presumably be determined in the same manner.
Calibration At high temperatuie, the temperature gradient through the apparatus becomes so large that a small correction must be added to the potentiometer reading, representing the temperature difference between the glass wall and the liquid film on the glass. This correction, which varies from about 0.5" F. at 150' F. t o 2.5" F. at 215' F., was obtained by determining the aniline point of several light-colored oils in both the A. S. T. M. and the dark oil apparatus. A calibration curve for the apparatus is shown in Figure 3. The broken curve is the thermocouple calibration curve.
Table I gives a comparison of the results obtained by the A. S. T. RI. method and the dark oil apparatus on a series of light-colored samples, and also shows the check results which are obtainable by different operators on samples of black oil. The blends of No. 6 fuel oil in 183 xiscosity neutral were made t o bring the neutral to an 8 A. S. T. M. color.
Literature Cited (1) Am. SOC. Testing Materials, "Standards on Petroleum Products and Lubricants", Appendix 2, p. 14, Sept. 1940. (2) Donn, Leon, IND. EXG.CHEM.,ANAL.ED., 9, 202 (1937). (3) Inst. Petroleum Tech., "Standard Methods for Testing Petroleum and Its Products", 3rd ed., Serial Designation F. 0. 23, 1935. (4) Matteson, Robert, Zeitfuchs, E. H., and Eldredge, K. R., IND. ENG.CHEM.,ANAL.ED., 13, 394 (1941). (5) VanWijk, W. R., and Boelhouwer, J. W. M., J . I n s t . Petroletun Tech., 24,598 (1938). PRESENTED before t h e Division of Petroleum Chemistry a t the 102nd M e e t ing of t h e AMERICAN CHEMICAL SOCIETY, Atlantic City. 3 . J.
