INDUSTRIAL AND ENGINEERING CHEMISTRY
64
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
++ +
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.
Vol. 14, No. I
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.
Electronic Relays J
SUTTON REDFERN
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.
T h e F l e i s c h m a n n Laboratories, Standard Brands Incorporated, New York, N. Y.
1.
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 test-
ing 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,.
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
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.
ANALYTICAL EDITION
January 15, 1942
The advantage of a beam-power amplifier tube of the type 117L7GT is its ability t o provide high-power output at low plate voltages-for example, the 117L7GT will deliver 45 milliamperes a t a plate voltage of 110 volts. I n contrast, Waddle and Saeman used a triode amplifier, 6C5, whose maximum plate current 1s not over 15 milliamperes. Rudy and Fugassi state t h a t a n advantage of the cold cathode, starter anode, gas-filled tube, OA4G, is its ability to supply a higher plate current at 110 volts than a high vacuum tube. This statement is erroneous because almost any beam-power amplifier tube will supply a maximum plate current of 40 to 50 milliamperes, whereas the maximum plate current of the OA4G is 25 milliamperes. With large plate currents available almost any relay on hand may be used. Successful operation has been obtained from a Struthers and Dunn relay designed for a coil voltage of 220 volts alternating current, with a direct current resistance of 500 ohms without the use of an intermediate, highly sensitive relay. Such a relay will handle a 30-ampere load.
65
nected for use with a mercury thermoregulator which closes on rise of temperature. Potentiometer R1 provides a variable negative grid-bias. It is adjusted by closing the control terminals and adjusting R1 until the relay just opens. Too fine an adjustment should not be made, as the line volta e may vary during use. Resistor RS reduces the current controlfed by the relay contacts to a few microamperes. Condenser Cs, with resistors Rt and Rat forms a conventional resistance-capacitance time-delay network.
tFIGURE 3
FIGURE 2
RE
1174 A.C. FIGURE 1.
RI.
RE.
T.
RELAY CIRCUIT
Resistor Relay Control contacts
The relay circuit shown in Figure 1 utilizes the 117L7GT tube which was introduced recently. Serfass (3) has also recently described a circuit which utilizes this tube but has used it in such a manner that the grid-bias voltage is not completely independent of the plate current. The filament of this new tube is designed to be operated directly from the 117-volt alternating current line, eliminating a filament dropping resistor with its resulting inconvenience and power loss. For cla+ty the 117L7GT is shown as if it were two tubes. The diode rectifier section furnishes a fixed, rectified, grid-bias volta e. The beam-power amplifier section uses plate rectification of the alternating current which is filtered by means. 0.f condenser C Iand ~ the relay inductance. As shown, the circuit IS con-
Without Csno time la is present, but with Cspresent there is a definite delay of the refay on both making and breaking the control contacts. Suitable values of Cs have been found to lie between 0.05 and l mfd. It is suggested that as a start a 0.05-mfd. condenser be tried. If this does not give sufficient delay to prevent chattering then 0.1 mfd. or larger should be tried. The delay is proportional to the product of R~CS but is also dependent on the value of Rt and the adjustment. of R1. Of course, if no delay is needed this condenser may be omitted. Resistor RI is a screen voltage dropping resistor whose exact value will depend on the resistance of the relay. The value of R, is chosen so that the maximum rated plate and screen currents of the tube will not be exceeded. This is especially necessary when a relay with a low resistance is used. The correct value of R, is easily determined by connecting a milliammeter in the plate circuit and changing R, until the plate current is not over 45 milliamperes. In some cases RL may be omitted and the screen either connected before the relay or tied to the plate, whichever position gives the lowest necessary plate current. These two positions should be tried before using a resistor. If the relay contacts are to open when the control contacts open, Figure 2 shows the necessary circuit changes. For convenience, Figure 3 shows the bottom socket view of the 117L7GT. A very compact apparatus can be constructed because of the use of only one tube. This circuit can be constructed at a cost of approximately two dollars, exclusive of the relay. Several of these relays have been in service for a considerable time and have given very satisfactory performance. This circuit, which can be used only on alternating current, is not isolated from the supply voltage and there is some danger of accidental shocks when the contact points are touched. However, a 5-megohm resistor in the control circuit greatly reduces this danger. It is, of course, possible to use a transformer t o supply the plate voltage and thus eliminate any danger of shocks, but this increases the cost and the weight of the apparatus.
Acknowledgment The author wishes to express his appreciation t o Quick Landis for his assistance in the design of this circuit.
Literature Cited (1) Hawes, R. C.,IND.ENQ.CHEM.,ANAL.ED., 11, 222-3 (1939). (2) Rudy, Jr., C. E., and Fugassi, P., Ibid., 12, 757 (1940). (3) Serfass, E.J., Ibid., 13, 262-3 (1941). (4) Ibid., 13, 352-3 (1941). (5) Waddle, H. M., and Saeman, E., Ibid., 12, 225 (1940).
