Aniline Point Determinations with DarkColored Oils A Circulating Test Tube A. A. WILLIAMS AND E. W. DEAN Standard Oil Development Company, Standard Inspection Laboratory, Baj-onne, N. J.
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X I L I X E point determinations of transparent oils are commonly made in a n air-jacketed t’est tube as recommended b y Tizard and Varshall (4) and prescribed by the American Society for Testing Materials (1). When dark oils must be tested, visual observation fails to detect turbidity in layers of liquid 20 to 25 mm. t’hick,and various ot.her schemes have been proposed and used.
ventional apparatus and procedure but not absolutely opaque when dissolved in a n equal volume of aniline and observed in layers approximately 2 mm. thick. It has proved entirely adequate for existing needs with the simple accessories that are described herein and is considered more convenient and accurate for light-colored oils than the apparatus prescribed by the A. S.T. M.
Donn ( 2 ) proposes determining the temperature at which a break occurs in the viscosity-temperature curve. \-an Wijk and Boelhouwer ( 6 ) and Matteson, Zeitfuchs, and Eldredge ( 3 ) detect changes in transparency to infrared radiation. Makeshift methods, such as decolorizing the dark oil with adsorbents or diluting with water-white distillates of known aniline point and calculating on the basis of assumed additivity, have also been used. The writers have been favorably impressed with the method of Matteson, Zeitfuchs, and Eldredge, but note that it does not permit direct measurement of the temperature of the thin layer of oil that is under observation. The circulating test tube developed by the authors, prior to the appearance of the publication by Matteson and his associates, avoids this disadvantage and it might be practical to modify their apparatus to permit its use.
Apparatus The tube is in the form of a U, with a cross tube connecting the two arms about halfway up. The cross tube is flattened in the middle to form a “cell” about 1 to 2 mm. thick and about 20 mm. wide. A tube of proper dimensions to hold 18 to 20 ml. of a mixture of equal volumes of aniline and oil is shown in Figure 1. A piece of sheet metal with the edges rolled and an aperture 10 mm. in diameter in the center, as shown in Figure 2, is fitted to the U-tube with the aperture directly back of the flattened part of the cross tube. The tube could, if desired, be insulated or en-
The circulating test tube described below was devised primarily to permit testing oils which were too dark for the con-
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FIGURE 1 (Left). DESIGN AND CONSTRUCTION OF CIRCULATING TESTTUBEFOR ANILINEPOINTDETERMINATIONS
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8 RHEOSTAT
I MOTOR
Dimensions in millimeters
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FIGURE2. DESIGNAND CONJ i OF METAL SHIELD HOLD~NQ GLASSTESTTUBE FIGURE 3. ASSEMBLY OF CIRCULATING TESTTUBE, METALSHIELD, AND ACCESSORIES Dimensions in millimeters 63
STRUCTION
INDUSTRIAL AND ENGINEERING CHEMISTRY
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TABLEI. AGREEMENTBETWEEN ANILINE POINTS AS DETERMINED WITH CIRCEL.4lING TESTTUBEAND A. S. T. M. METHOD AND APPARATUS Product
co1ol.a
A. S. T. 11.precipitation naphtha 25 s 9 Stoddard solvent 25 s V. M. 6 P . naphtha 25 t s Kerosene 25 S Kerosene 25 s Motor gasoline 17 S 1.5 u Pale Diesel fuel oil No. 2 domestic fuel oil 2.0 u Pale Diesel fuel oil 2.5 c Pale Dieeel fuel oil 3 . 5to 4 . 0 U Dark Diesel fuel oil 11’2 T-R Filtered cylinder oil 1 / z T-R )/E T-R Hydraulic oil s/s T-R Dark Diesel fuel oil 1/4 T-R Dark Diesel fuel oil About 1/1 T-R Dark Diesel fuel oil Coastal black lubricating Darker than 1/1 T-R 011 Steam cylinder stock (unDarker than 1/4 T-R filtered
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Aniline Points A . S. T. AI. New method
c.
58 fi
57.1 54 5 64 7 71.1 45.2 67.2
5s.o
62.2 58.5 53.6 124.0 Too opaque Too opaque Too opaque Too opaque
c.
58.4 57.5 54.6 65.0 71.0 45.0 67.1 58.2 62.4 58.8 53.7 124.0 97.0 57.8 56.0 55.6
Too opaque
82.5
Too opaque
131.5
4 S,Saybolt color; E, A. S.T . MI.-Unioncolor; T-R, TapRobinson color. 8 U is approximately the same as 1 T-R.
been tried out, over a considerable period of time, in routine service in their own and several associated laboratories. I n the present case this has not been done, as i t is felt t h a t information should be released promptly regarding the basic principle of the circulating test tube, and that improvements in the details of construction and operation will result from its broad use. There is a widespread need for a n aniline point method which retains the simplicity and convenience of the A. S. T. M. apparatus and procedure but which is applicable to moderately dark colored oils.
Literature Cited (1) Am. SOC.T e s t i n g Materials, Designation D 611-11 T. (2) Donn, Leon, IND.ENO.CHEM.,ANAL. ED., 9, 202 (1937). (3) Matteson, R., Zeitfuchs, E. H., and Eldredge, K. R., Ibid., 13, 394 (1941). (4) Tizard, H. T I and Marshall, A. G , J . SOC Chem. Znd.. 40, 20-6 (1921). (5) Van Wijk, W. R., and Boelhouwer, J. W.M , J . Inst. Petroleum Tech.,24, 598 (1938).
closed to ensure a more gradual change of temperature, but the results obtained have been so satisfactory that there is a doubt as to the justification for more complicated apparatus.
Method of Operation In operation, the tube is clamped to an ordinary ring sup ort An auger-type glass stirrer of the type suggested for the S: T. M. method is insert’edin one side of the U with the helical section located at the junction of the cross tube and the U. The stirrer is connected to a variable-speed motor. A suitable device is a fractional horsepower motor equipped with a speed-reducing gear and a rheostat. A thermometer is inserted in the opposite side of the U-tube with its bulb immersed in the liquid. The volume of liquid should be such that ihs surface is about 2 mm. above the level of the thin part of the cell, when the thermometer and the stirrer are in position. A microscope lamp is located with the spot of light directed on the aperture in the metal shield. The aniline-oil mixture may be conveniently heated by directing a small flame against the bend of the tube, or other means of heating the mixture may be employed, if desired. Figure 3 is an illustration of the apparatus, assembled, ready for use. In testing very transparent products the turbidity point can be observed in the body of the tube or in the cell without the aid of artificial light, and for dark products the observation is made in the cell with t,he aid of a spot light,.
Electronic Relays J
SUTTON REDFERN The Fleischmann Laboratories, Standard Brands Incorporated, New York, N. Y.
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Scope The tubes at present available have cells about 2 mm. thick and permit the testing of oils which are considerably too dark for color determinations with either the A. S. T. M.Union or the Tag-Robinson colorimeter. The results shown in Table I indicate, in a general way, the scope of these tubes when turbidity is observed visually. Their range can undoubtedly be increased b y employing infrared radiation, and some additional latitude may even be attainable with visual observation by decreasing the thickness of the cells. It is obvious that the necessity of keeping the liquid in rapid circulation limits this possibility.
Accuracy The figures in Table I indicate that the apparatus and procedure, described herein, give results that do not differ from those of the A, S. T. RI. method b y appreciably more than the 0.2’ C. which is considered normal reproducibility for the latter. The writers usually defer the publication of papers describing analytical methods and apparatus until they have
Vol. 14, No. I
S
EVERAL electronic relay circuits have been described in
the chemical literature ( I - L ~ ) ,but all have certain undesirable features which have been largely eliminated in the circuit here described. Electronic relay circuits are useful in all cases where i t is desirable to use a small controlling current of the order of a few microamperes. The use of such a small current prevents arcing a t the control contacts and consequent fouling. The sensitivity of the control can usually be increased, especially with bimetallic type thermoregulators. If, in addition, the control contacts are subject to mechanical vibration it may also be desirable to introduce a time-delay into the circuit in order t o prerent chattering of the relay contacts. Only one of the circuits (4) referred to makes any provision for a time-delay. This circuit uses the heating time of the tube filament to produce a time-delay but is not a true electronic relay circuit, in that the circuit uses a rectifier tube instead of a n amplifier tube, and the entire filament current, 75 milliamperes, passes through the control contacts. The usual condenser connected across the relay coil really acts as a filter condenser and not as a delay condenser. The circuit herein described uses a diode beam-power amplifier tube with a separate, independent, rectified grid-bias voltage. The importance of a n independent grid voltage supply has not, in general, been appreciated. I n the usual circuits such as those of Hawes and lJ7addle and Saeman, the controlling grid voltage is obtained by the cathode-biasing method. This has two disadvantages in relays. (1) The grid-bias voltage is subtracted from the total voltage available to supply the plate voltage, which may then be too low to derive much power output; ( 2 ) this method makes i t impossible to cut the plate current off completely, since some current must flow at all times in order to produce a negative grid-bias. This continuous current %owing through the relay may cause the relay to stick or fail t o open. Higher-priced, low-difierential relays can be used but are unnecessary.
