January 15, 1933
INDUSTRIAL A N D ENGINEERING CHEMISTRY
(8) Dox, A. W., and Keidig, R. E., Agr. Expt. Sta., Iowa State Coll. Agr. Mech. Arts, Research Bull. 7 (1912). (9) Duclaux, E., “Trait6 de Microbiologie,” Vol. 3, p. 385, Masson,
Paris, 1900. (10) Edelstein, F., and Csonka, F. V., Biochem. Z., 42, 372 (1912). (11) Eyre, J. W. H., Brit.Med. J . , 1900, 11, 921. (12) Fred, E. B., and Peterson, W. H., J . Infectious Diseasss, 27, 539-49 (1920). (13) Freudenreich, E. de, and Jensen, O., “Annuaire agricole de la Suisse,” Part 4, Berne, 1906. (14) Harden, A., J . Chem. Soc., 79, 610-28 (1901).
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(15) Jensen, Landw. Jahrb. Schweiz, 18, 319-405 (1905). (16) McIntosh, J., and Smart, W. A M., Brit. J . Exptl. Path., 1, 9-30 (1920). (17) Mudge, C. S., J . Bact., 2, 403-15 (1917). (18) Richmond, H. D., and Miller, E. H., Analyst, 31, 318-35 (1906). (19) Selieber, M. G., Compb. rend., 150, 1267-70 (1901). (20) Susulri, S. K., Hastings, E. G., and Hart, E. B., J. Biol. Chem., 7, 431-58 (1910). (21) Woodman, A. G., and Burwell, A. L., Tech. Quart., 21, 1 (1908). R ~ C I D I VJune E D 2 , 1932
Automatic Titrating Devices K. HICKMAN AND C. R. SANFORD, Eastman Kodak Co., Rochester, N. Y.
T
HE paper industry has a very real need for a recording titrator, for a device which will determine the total acidity of alum baths, wash waters, etc. The present potentiometric recorders do not entirely meet the need, which is for an indication of reserve acidity and not for the potential of hydrogen ions. Further, it is found that total acidity and potential are not simply or constantly related to one another under working conditions in a paper mill. The problem has been approached in two ways: directly, by the mechanical manipulation of solution volumes; and indirectly, by the diffusive mixing of parallel liquid streams.
The means chosen for securing the performance is illustrated in Figures 1 and 2. The first requisite, a timing unit to control the sequence of events, is provided by bulb A and appendages ( 2 ) . When the bulb, which is fed with water or the unknown (dilute solution) under approximate control from tap B, has filled to level c, the solution passes over siphon C, loading the mercury column, D, which completes
DIRECTMECHANICAL TITRATOR
-4repeating cycle has been secured which comprises the following operations: (a) A sample of standard volume is withdrawn from the unknown liquid. (b) The sample is discharged into a reaction vessel together with a smtable quantity of indicator solution. ( c ) The mixture is observed b an optical device which (d) Controls the addition of tge second component, the estimating fluid, in volume sufficient t o reach neutrality, and (e) Activates a en t o record the volume on a chart. cf) The titratel solution is discharged t o waste, the chart moved t o a new position, and (9) The cyrle repeats.
FIGURE2. VIEW OF SET-UPOF TITRATOR
a circuit through the electrode, E . The current actuates a magnetic valve, F , which allows the contents of the reaction vessel, G, to pass to waste. Soon after the emptying of G, bulb A should be full enough for its contents to siphon rapidly down tube H , unload mercury column D,and refill the reaction vessel. During the passage of this unit volume of fluid, a constant and repeatable suction impulse (negative pressure X time of flow) is exerted a t each point in the column, notably a t points I and J, from which tubes communicate with constant-level reservoirs of reagents. Through one tube a chemical color indicator (phenolphthalein, methyl red, etc.) is imbibed. The other tube is used only when pure water is fed to bulb A , and its purpose is to admit a predetermined quantity of the liquid to be titrated. Thus, OF DIRECT MECHANICAL TITRATION two general levels of solution strength can be manipulated, FIGURE 1. DIAGRAM
ANALYTICAL EDITION
66
the side arm accommodating liquids containing from about 2.6 to 80 per cent of reactive material, the bulb being reserved for more dilute solutions. The reaction vessel, G, is in two parts, a large bulb, g, and a smaller one, g’, which communicate with one another by the centrally fixed lower tube, K , and the ecc e n t r i c a l l y placed return tube, IC. In g’, the stirring paddle, rotated by the motor, 11,is stopped temporarily through relay 1, which is o p e r a t e d in tandem with valve F each time the vessel e m p t i e s . The solution is monitored by the 100-watt projection lamp, M , and the light-sensitive element, N . FIGURE 3. DIAGRAM OF RESince it is a change of intenCORDING MECHANISM sity which is being observed during titration, a way must be devised to make N inoperative when the vessel is empty and is thus in its most transparent condition. I n lieu of a mechanical shutter, the larger bulb is allowed to serve as a lens when full, concentrating the light from M on to N which otherwise remains relatively dark. The cycle of operations is now continued by the electrical train in connection with N . Leaving for the moment the exact nature of the receiving element, we may assume that the action of light is to generate a current sufficiently large to operate a relay. A fraction of a second after G is full, the entrained bubbles rise to the surface, the stirrer starts and cell N provides an e. m. f. just sufficient t o operate, through relays, a solenoid valve, 0, and the pen of the re-
FIGURE4.
ARRANGEMENT OF OPTICAL NISM WITH PHOTRONIC C E L L
MECHA-
corder. Valve 0 admits the standard titrating liquid from a constant-level supply, Q, through a calibrated valve, R, and a fine tube, S, to the smaller bulb, g’, where it is rapidly dispersed into the main body of the solution. The mixing lag i A 1 to 1.5 seconds. The admission of titrating liquid under standardized conditions allows us to suppose that time and volume become mutually convertible. Hence, by recording time of addition with constant subtraction of 1.5 seconds, we record volume. The time measurement is accomplished by allowing a clock-driven pen to be actuated in series with the admission valve, so that the moment the liquid enters the reaction vessel the pen starts traveling over the chart. The admission continues till a color change is reached, when the light, becoming partially obscured by the solution, ceases to provide the minimum actuating current, the titrating liquid
Vol. 5 , No. 1
is shut off, and the pen returns to zero. The master flow through B is arranged so that the reaction vessel shall be emptied soon after the completion of titration, enabling the events to repeat. RECORDING MECHANISM. A Telechron clock motor with shaft rotating a t one r. p. m. is mounted, field magnet downwards on a pivot, as shown in Figure 3. On the shaft is a small roughened wheel which can engage with the rubber facing of a quadrant, the opposite end of which carries the recording pen. The clock rests by gravity in its idle position a little to the left of the vertical, and is brought into contact with the quadrant by a lever and magnet when the latter is energized during titration. The quadrant is weighted to return the pen to zero when the magnetic pull ceases. The chart for the records is carried in a clock whose drum rotates once an hour or once a day. The records consist of a series of vertical lines (arcs) of lengths corresponding to the volume of solution addition. If the lines are drawn close together, their upper limits provide a curve of the variations . . _in composition of the unknown liquid. OPTICALM E C H A N I S MIt. is plain that a gas-filled photo-cell and commercial amplifier can be adapted directly to this service and, therefore, only three alternative devices which haie been used successfully in the place of such a cell will be described, The new cell marketed by the Wes- F I G U R E 5. C R U D E GAS ton Electrical Instrument Corp., the photronic cell, has proved very satisfactory for titrations where detection is required of a color change visible to the eye. The diagram in Figure 4 shows the preferred arrangement. The cell is connected in series with a microammeter and a Weston contacting galvanometer, Model 30-H, 300 ohms internal resistance, 250 microamperes per mm. deflection. The controlling spring about the pivot is twisted so that the needle is held against that contact pillar which is not in use, requiring a comparatively heavy current to effect contact with the live pillar. (If this precaution is not taken the galvanometer may stick.) An adjustable resistance, carried in the lamp circuit, is set so that contact is just established when the reaction vessel is filled with clean water. The output terminals of the galvanometer are connected in series with a 6-voh battery and a Weston Mercoid relay, type 630, 6-volt, Series 118. The duty side of this relay operates the circuit for the solenoid titrator valve and the recording clock magnet. The detail adjustment varies with the nature of the titration. When standard alkali is being run against unknown acid with phenolphthalein as indicator, a green screen (Wratten filter No. 59) is used between the vessel and the photronic cell; 95 to 100 volts across the 110-volt lamp, yielding 175 microamperes for operating the contacting galvanometer. Development of a pink color during titration reduces the current ultimately to about 80 microamperes, but the end point is considered reached a t 165 microamperes, and a t that point the contacting galvanometer breaks the circuit. Many solutions which are too discolored to permit titration with the usual indicators transmit freely in the infrared. The nickel wire bolometer described elsewhere (1) is responsive to long-wave radiation, and can thus be used as a monitor provided a suitable indicator is available. The development of a colloidal precipitate has been found to be a simple way to absorb the infra-red, and the metals of analytical group 3 have been studied t o discover an indicator for acid --+alkali titrations. Whereas aluminum and chromium salts are useless and iron salts poor, a mixture of ferric and aluminum chlorides gives a sharp end point.
pinges on the receiving surface the gas expands, moving the diaphragm into electrical contact. Any gas in excess of the minimum required passes out through the bubbler
ANALYTICAL EDITION
68
would occur sharply in one cup in a series of twenty, but only when individual stirring was provided and the jets were kept scrupulously clean. The method was impracticable in this primitive form.
Vol. 5, No. 1
paddles which engage in the slip stream without being directly hit by the jet. From the float the liquid is discharged by a distributing pipe into the compartments, and, during any considerable period of time, is supplied to each compartment in an equal quantity. The tortuous path taken by the liquid insures mixing, and the point of neutrality is decided in one or two compartments, with a consequent error of not more than 2 or 4 per cent. A lamp is hung above the float chamber, and the compartments are numbered on the bottom in reverse writing so that the titration can be read in a mirror placed beneath the apparatus. NOTEON SOLENOID VALVES The valves mentioned earlier in the paper are constructed cheaply from skeleton solenoids obtained commercially. Type CR-9503l a. c. 1-inch stroke, 1-pound pull is adapted for the plunger to compress, or release from compression, a piece of soft rubber tubing, which thus forms the simple acid-proof body of the valve. The solenoid is then wound with wire of a size appropriate to the voltage and purpose. A typical unit is shown in Figure 10.
FIGURE10. TYPICALSOLENOID UNIT
A satisfactory instrument was constructed utilizing a circular chain of cups and a rotating solution divider for the second reagent. In Figure 9 the chain of cups is shown built into the space existing between two concentric Kodaloid cylinders (3). The channel is divided into fifty compartments which rise from a sloping spiral platform. The liquid is admitted into the top pocket through a calibrated jet fed from a constant-level vessel, and flows from compartment to compartment, over one barrier and under the next, until it has traversed the entire chain, whence it flows to waste. The second liquid, which should be the more dilute, is supplied, also at constant speed, to a float which rotates in a central pool of water maintained in circulation by a jet buried beneath the surface. The float is fitted with short pendant
LITERATURE CITED Hiokman, K., J. Soc. Motion Picture Engrs., 17,591 (1931). Hickman, K.,Trans. Sac. Motion Picture Engrs., 26, 37 (1926). Hiokman, K., and Hyndman, D., J . Franlclinlnst., 207,231(1929).
RECEIVED August 6, 1932. Communication 497 from the Kodak Research Laboratories. 1
General Eleotrio Catalog No. 29.
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An Adjustable Stopcock Remover R. W. WESTERMAN, 496 W. Brentwood Ave., Detroit, Mich.
A
FROZEN stopcock in a piece of apparatus is always an annoyance and frequently causes loss of considerable time and money if the apparatus is broken in trying to remove the plug from the body of the stopcock. Allison ( I ) describes a stopcock remover which has been used by the writer to considerable advantage. A patented device (3) is also made and sold. Both of these have the disadvantage of having the chucks or receptacles as a series of fixed sizes, and difficulty is experienced in getting a chuck to fit properly the particular stopcock at hand. ) The writer has devised and used an adjustable chuck which is much more satisfactory. C o m p l e t e success h a s been attained so far in removing plugs from a great many sizes and kinds of badly frozen stopcocks without breaking a single one. I n the adjustable chuck made by the writer, the two sections of the chuck are FIGURE1 adjusted to fit the shoulder of the outside of the stopcock exactly, the handle of the plug remaining loose between the two sections of the chuck. I n this position the chuck and stopcock are placed between the jaws of a vise or C-clamp so that a light steady pressure may be applied to the chuck and the shoulder of the stopcock on one side, and to the small end of the plug on the other side. A block of wood may be used a t the end of the plug to prevent chipping. The rounded shoulder of the cock will be strong enough to withstand the pressure from the soft metal (brass)
of the chuck. The light pressure thus applied will soon loosen the plug from the body of the cock. If necessary, the removal may be aided by warming the body of the stopcock with hot water or a match flame. Where alkaline solutions have caused the sticking, the method of Ardagh (g) may be useful. He uses alternate suction and pressure on dilute hydrochloric acid around the stopcock. The writer has never had to resort to this procedure. Adjuitable chuck
/
woden
pin
/
FIGURE 2
Figure 1 shows the essential parts of the chuck-1, main body which may be fastened to the stem of a C-clamp; 2, hinge; 3, movable section held in position by the screw; and 4,a compression spring between the main body and the movable section. Figure 2 shows the chuck used in a vise. This chuck may also be made to fit on the commercial stopcock remover. LITERATURE CITED (1) Allison, V. C., J. IND.ENO.CEBIM.,11, 468 (1919). (2) Ardagh, E.C.R., Can. Chem. Met., 9,137-9 (1925). (3) Swift, C.K., U.S. P a t e n t 1,453,895(May, 1923). R E O E I Y August ~D 24, 1932.
