MARCH, 1938
INDUSTRIAL AND ENGINEERING CHEMISTRY
more dense material is less liable to be carried away by suspension in the backwash. A possible defect of organolites is the low physical strength, since the granules are somewhat soft when wet. A quantitative estimate of resistance to abrasion has not yet been made.
Conclusion Experiments on preparing the acid-insolubilized material on a semiplant scale substantiate the smaller scale work as does actual softening of water in a portable size unit. Although the work cannot be said to have progressed from the experimental stage, the evidence ostensibly indicates that the organolites may be of some utility in the fields of water softening and acid regeneration and also, if selectively absorptive materials are developed, for special cation absorption.
Acknowledgment The author wishes to thank the Ellis-Foster Company and the Newark College of Engineering for permission to publish the data. The Permutit Company kindly furnished zeolite samples, and the Champion Fibre Company the Bindex and chestnut extract.
Literature Cited (1) Adams, B.
A.,and Holmes, E. L., J . SOC.Chem. Znd.. 54, 1-6T
(1935): British Patents 450,308 and 450,309 (July 13, 1936); U. S.Patent 2,104,501(Jan. 4, 1938).
(2) Austerweil, G.,J . Soc. Chem. Znd., 53, 185-9T (1934). 28, 1279(3) Behrman, A. S., and Gustafson, H., IND. ENQ.CHEM., 82 (1936). (4) Bird, P., Colburn, F., and Smith, F., Ibid., 25, 564 (1933). (5) Borrowman. G., U.8. Patent 1,793,670(Feb. 24, 1931). (6) ZEid., 1,994,682(March 19, 1935).
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(7) Burgess, P. S.,and McGeorge, W. T., Science, 64,652-3 (1926). (8) Cerecedo, L.R., Hennessy, D. J., Kaszuba, F. J., and Thornton, J. J., S. Am. Chem. Soc., 59, 1617-22 (1937). (9) Ellis, Carleton, IND.ENQ.CHEM.,28,1141-2 (1936);“Chemistry of Synthetic Resins,” Chap. 14, New York, Reinhold Publishing Corp., 1935. (10) Fischer, F., and Fuchs, W , Brennstof-Chem., 8, 291-3 (1927). (11) Gans, R., German Patent 197,111 (1906);U. S.Patents 914,405 and 943,535 (March 9 and Dee. 14,1909). (12) Hoover, C. P., Ohio Conf. Water Purification, 13th Ann. Rept., p. 40 (1933). (13) Hopkins, E.S., “Water Purification Control,” 2nd ed., p. 162, Baltimore, Williams and Wilkins Co., 1936. (14) Kappen, H., and Rung, F., 2. Pflanzenernithr.DCngung Bodenk,, SA, 345-73 (1927). (15) Kelley, W. P., and Brown, 5. M., Soil Sci., 21, 289-302 (1926). (l5A) Kirkpatrick, W.H., U. 5.Patent 2,094,359(Sept. 28, 19371. (16) McGeorge, W. T.,Ariz. Agr. Expt. Sta., Tech. Bull. 30,181-213 (1930): 31,215-51 (1931). (17) Mitchell, J., J . Am. SOC.Agron., 24, 256-75 (1932). (18) Muller, J. F.,Sod Sci., 35,229-37 (1933). (19) Nordell, E , Mich. State Coll. Agr., Eng. Espt. Stu. BUZZ.61,1525 (1935): reminted bv Permutit C o . (20) N. V. Oc’trooien MaaGchappij “AEiivit,” French Patents 778,922(1935),784,348 (1935),and 805,092 (1936). (21) Scott, W. W., “Standard Methods of Chemical Analysis,” 2nd ed., revised, p. 559,New York, D. Van Nostrand Co., 1917. (22) Sigmond, E., Mutematik. TermBszett. &tesit8, 43,51-78 (Hung.). 79-80 (Ger.) (1926). (23) Sokolov, N., Mitt. staatl. Znst. esptl. Agron., Abt. Ackerbau (Leningrad), No. 20 (1929). (24) Straub, F. G., Univ. Ill., Eng. E s p t . Sta. Bull. 216 (1930). (25) Sweeney, 0.R.,and Riley, R., IND.ENQ.CHEM.,18, 1214-16 (1926). (26) Tiger, H.L.,J . Am. Water Works Assoc., 26, 357-70 (1934). (27) Tiger, H. L.,and Goetz, P. C., U. S. Patent 2,069,564(Feb. 2, 1937). (28) United’ Water Softeners, Ltd., British Patents 450,574 and 450,575 (1936). (29) Way, J. T., J . Roy. Agr. SOC.,11, 313 (1850); 13, 123 (1852). RECEIVED October 22, 1937.
Liquid-Level Control Apparatus I
R. E. HERSH, E. M. FRY,‘ AND M. R. FENSKE The Pennsylvania State College, State College, Pa.
-4
LTHOUGH a number of methods have been devised for automatically controlling liquid levels or liquid-liquid I interface levels, nearly all of them depend on floats a t the surface or a t the interface, or on a differential manometer mechanism to operate a switch or relay. The mechanism is sometimes rather bulky and requires a considerable amount of holdup of the liquids to ensure reliable control. I n this article simple and compact mechanisms are described for controlling interface levels or liquid levels which operate on the differencesin electrical conductivity of the two liquids at the interface or of the liquid and air a t the surface. Such a device for controlling the interface level in a lubricating oil extraction tower using a number of different solvents has been in satisfactory operation in this laboratory for more than a year. The apparatus consists essentially of electrodes a t the interface and a means for utilizing the small current flowing through the solvent to operate a relay which, in turn, regulates the flow mechanism. One method of accomplishing this ,is illustrated in Figure 1. The electrodes are inserted from opposite ends of a specially constructed liquid-level gage on the extraction tower a t a point where the interface between the solvent and oil occurs, the electrode points being any-
‘ Present address, Standard Oil Development Company, Elizabeth, N . J.
where from 0.25 to 0.75 inch apart. To insulate the leads from the tower, 0.5-inch spark plugs with the grounded points removed are used, extensions being soldered or welded to the points protruding through the porcelain. These electrodes are part of a single-stage resistance-coupled amplifier circuit operating on 110 volts a. c. This circuit utilizes a type 37 or 37A three-electrode vacuum tube as an amplifier for operating a relay in the plate circuit. The external circuit then energizes a solenoid valve in the drawoff line from the tower. When the solvent layer is between the electrodes, its conductance is sufficient to produce a large grid-bias, and the plate current, therefore, is too low to operate the relay. However, as the oil builds up and insulates the electrodes from each other, a very weak current flows in the grid circuit through the 5-megohm resistor, and the plate current increases sufficiently to close the relay; whereupon, the solenoid valve is opened and the oil permitted to drain from the tower. The grid leak is indicated in Figure 1 as a variable resistance since, with different liquid-liquid systems, it may be desirable to employ a different size in order to vary the range through which the plate current fluctuates as an aid for positive relay action. However, the flexibility obtainable amounts to only a few milliamperes when the resistance is changed from 5 t o 1
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INDUSTRIAL AND ENGINEERING CHEMISTRY
megohm. The resistors, paper condensers, and tubes can be obtained from any radio supply company. Obviously, a 300-ohm resistance could be substituted for the 40-watt bulb, but the latter serves as an indicator lamp and can be placed at a convenient place where the illumination can be utilized. A suitable relay for this circuit is an electromagnetic relay having
250 ohms
VOL. 30, NO. 3
about 0.5 inch in diameter and 0.75 inch in depth with an open top, forms one electrode, and a metal wire or rod inserted in a glass tube of about 7 mm. diameter forms the other electrode. The glass tube extends almost to the bottom of the cup and the wire to within an inch or so of the end of the tube. The cup is partially filled with water, and the device, suitably supported to provide rigidity, is immersed in the oil, when the level is a t the correct height in the container, to a depth such that the water rises inside the glass tube until it contacts the wire electrode. The device is then fixed in position, and final adjustments are made by sliding the wire up or down in the glass tube. The electrical circuit required to utilize the low currents flowing through the water can be identical with that previously described or with that included in Figure 2 , a modification of the previous method. The circuit shown in Figure 2, using a type 43 vacuum tube, is capable of larger power output and is more desirable where a heavier relay is required. A suitable relay for use in this circuit is one having a 190ohm coil and operating on 10 milliamperes. (Such a relay, capable of breaking 10 amperes, can be obtained from Struthers-Dunn, Philadelphia, as their Type BSBF8-G2.) The total cost of equipment for this circuit is about $15.00.
I
FIGURE1. INTERFACE-LEVEL CONTROL APPARATUS
a 6300-ohm coil and operating on 32 volts and 5 milliamperes (type E, obtainable from the G-M Laboratories, Chicago) ; the points are capable of carrying 1 ampere. The total cost of the equipment, exclusive of the solenoid valve and other tower auxiliaries, is about $10.00. One precaution that should be followed in using a grounded alternating current source is to connect the ground line to the electrode entering the conducting liquid, as indicated in Figure 1, in order to prevent leakage to the apparatus. One method that is used to overcome any differences in potential between the electrodes and the apparatus is to connect the ground line to the apparatus, thereby making the entire tower one electrode, and inserting the other electrode a t any desired point by means of a 0.5-inch pipe fitting and a 0.5-inch spark plug, or other suitable insulator. Another method is to insulate the entire circuit by using a 1:l transformer between the line and the connections to the instrument. The apparatus operates satisfactorily to control interface levels between liquids with small conductances, such as water, acetone, methanol, ethanol, /?,P’-dichlorodiethyl ether, etc. , and nonconducting liquids, such as petroleum oils, gasoline, glycerol, butanol, etc. For the conducting liquids, therefore, the apparatus can be applied to controlling the level in a tank or container, the liquid being used to complete the grid-control circuit; as the level drops, the electrodes, or one electrode and the tank surface, are separated by an air gap. However, with nonconducting liquids somewhat modified electrode equipment is required for adapting the apparatus to liquid-level control. This can be accomplished by a small float which completes the circuit when the level is too high or by utilizing an immiscible conducting liquid as illustrated in Figure 2 . The system is shown as a level control mechanism for an oil receiver where the conducting liquid for the operation of the relay circuit is water. A small iron or brass cup,
FIGURE2. LIQUID-LEVEL CONTROL APPARATUS
Obviously, the applications to which these relay circuits can be adopted are not limited to the cases illustrated here. They can be used t o operate motor-driven valves, vary resistances, ring alarms, control governor speeds, etc. Similarly, the electrodes can be utilized in pressure or vacuum regulatory manometers or in thermoregulators for obtaining positive control with a minimum of mechanical equipment. Sensitive control of pressure or vacuum may be obtained by employing a conducting liquid in the manometer which has a low specific gravity, such as sulfuric acid, and thermostat control may be effected by using a conducting liquid in the thermoregulator which has a high cubical expansion. The actual current flowing through any of these liquids is only a fraction of a milliampere so that no sparking or electrolysis occurs. The instruments, therefore, have a wide application, are quite rugged, need no electrical shielding, and can be compactly constructed for long-time continuous service. RECEIVED September 23, 1937.
