US 2930747 A
Description (OCR text may contain errors)
March 29, 1960 c. M. JANKowsKl TITRAToR ELECTRODE PAIR Filed June 17, 1957 TITRAroR ELECraoDE PAIR Conrad M. Jankowski, Medinah, Ill., assignor to Central Scientilic Co., a corporation of Illinois Application .lune 17, 1957, Serial No. 666,105
2 Claims. (Cl. 21M-271) This invention relates to an electrode construction in which the electrodes are mounted in pairs for ease of handling and connection.
In the prior art the electrode arrangements employed in titration equipment have been mounted and connected individually, and this has been an annoyance that not only encumbers the actual titration operations but frequently leads to improper connections and erroneous results.
This is particularly true where a single titration appartatus is arranged for use in numerous different titration operations, each of which may involve a different electrode pair arrangement. The consequent frequent handling of the electrodes, which, incidentally, have heretofore been of fragile construction, has resulted in breakage and loss of the electrodes.
The principal object of the present invention is to provide a long-lived, low-cost, metallic electrode pai-r specification and in which like numerals are employed to designate like parts throughout the same,
Fig. 1 is a side-sectional view through one const-ructional embodiment of the invention;
Fig. 2 is a top plan view of the embodiment of Fig. 1; and
Fig. 3 is a sectional View corresponding to Fig. 1 and illustrating a different constructional embodiment in accordance with the invention.
As pointed up briefly hereinabove, the various different titration operations frequently require their own electrode pair arrangements, and the present invention deals With an electrode construction that offers important general advantages that are common to all o-f the individual` ized constructions although the specific details may vary considerably from one construction to another. For example, Fig. 1 discloses the indicator electrode pair construction for a mercaptan titration while Fig. 3 discloses the generator electrode pair for a mercaptan titration.
It is proposed to employ these electrode constructions with a titration apparatus that includes a rigid, polarized mounting socket for receiving the connection terminals and the socket is preferably arranged to support the electrode pair at an appropriate point for immersion in a solution under test that will normally be confined in a suitable beaker. In the usual arrangement, separate sockets are provided for the generator electrode pair and the indicator electrode pair so that the individual electrodes of each pair and the pairs themselves may readily be mounted in a predetermined, Xed relation ship within the solution.
lReferring now to the mercaptan indicator pair of elec- Sites Patent ployed which is, preferably, in the form of a cylindrical rod of machineable material that may be suitably d-rilled for receiving the various parts of the'iinished assembly. As shown, the rod is formed with a pair of small-diameter cylindrical bores or drill holes 11 that open through the lower end of the rod to receive the metal electrodes 12, a socket or large-diameter drill hole 13 that opens through its upper end to receive a terminal cap 14 of molded plastic insulating material that carries the necessary connection terminals 1'5, and a pair of enlarged intermediate bores 16 that connect the small bores '111 to the socket 13, with flexible, insulated lead wires 17 disposed in the larger bores 16 and establishing electrical connections between the electrodes 12 and the connectio terminals 1'5.
'It is important Ito a long-lived electrode construction that the holder be of a material that is chemically inert and non-absorptive in the presence of the solutions in which it is immersed. Furthermore, it should be resistant to mechanical shocks and should present a rigid body that will protect the part-s mounted in it. Finally, `and possibly of greatest importance, it must belreadily capable of forming a liquid-tight seal with the electrodes 12 in order to prevent seepage into the holder body when its lower end is immersed lin the test solutions.'v lf 4these solutions should 'creep up the electrodes and con- -tact the internal connections, internal short circuits may develop, or, in any case, the equipment will deteriorate rapidly. With this in mind, a white ceresin Wax 18 is deposited in molten form in the intermediate bores 16 to further seal the holder against seepage. The wax` is chemically inert in the presence of most solutions.
Polytetrauoroethylene, more commonly 'known under the trade name Teflon is la material that is admirably well-adapted to serve as the holder body. l
In assembling the various parts of the electrode holder, it is preferred to iirst connect the electrodes 12 to the lead wires 17, and this is done yby wrapping one or two turns of Wire around the side of the electrode and softsoldering the parts together. The electrodes are then pushed downwardly through the small bores 11 until they reach the position in which they are shown in Fig/'1, and bores 16 may then be iilled with molten wax, which is allowed to set. The lead Wires are then soft-soldered to the terminal-s 15, and the cap 14 is pressed into the socket 13 until it abuts the internal locating shoulder 29. The cap'is preferably arranged for a force-,fit `within the socket. ln the illustrated form, the electrodes are merely wedged through the bores 11 for a force-fit, and it has been found that with a Teflon body, a substantially perfect seal results and prevents the solution from seeping into the holder. It will be noted that any such seepage must scale the combined lengths of the bores 11 and 16 before any possibility of setting up an internal short circuit arises. l
In the case of mercaptan indicator electrodes the anode may berof platinum and the cathode may be of gold, and in order to prevent incorrect connections, the holder is, in effect, polarized by using a terminal cap of the type shown with an appropriate polarized receptacle. It will be noted that the usual third terminal post 21 ('Fig. 2) is removed so that the cap can fit correctly into its associated polarized receptacle (not shown) in only one position.
Fig. 3 illustrates an electrode construction for use as the generator pair in a mercaptan titration in which case Y both the anode 25 and the cathode 26 may be of silver. The construction is generally identical to that of Fig. 1, and corresponding parts are similarly numbered. The cathode 26, however, is shown threaded to illu-strate an alternative construction that is made possible with the use of a Teflon-like holder body. It has been found that it is possible to form a sharp thread on an electrode and then screw it into the cylindrical bores that are formed in the Teflon body for receiving the electrodes andachieve a 4vacuum-tight seal. This construction zcould have been employed in the Fig. 1 arrangement in -wire 17, and the bottom end of which is formed with a tapped axial bore 28 in which the threaded end of the silver anode 25 is received. With this construction, the anode 25 may readily be replaced by a new one whenever conditions require. In the arrangement of Fig. 3, a washer 29 of Teflon is mounted in an appropriate socket at the bottom end of bore 11 to prevent the solution from eating away the anode socket 27.
In assembly, the socket 27 is first connected to the lead wire 17 and the part-s are passed into the holder from the bottom until the socket is ush with the downwardly facing shoulder 30 that defines the socket -for the washer 29. The cathode 26, however, is again entered downwardly through the bore 11 until the threaded portion comes into play, at which time the exposed lower end of cathode 26 serves as a suitable handle for threading the cathode into its ultimate position. The washer 29 is pressed over the threaded end of anode 25, which may then be screwed into place to bring the washer snug against the shoulder 30. While there may be some initial seepage of solution up the anode 2S, it will not f result in any serious deterioration of the anode socket a liquid-tight seal with the electrodes to prevent seepage into the body. The body rigidly connects the various parts and is itself unbreakable and chemically inert in the various solutions to which it will be subjected.
It should be understood that the description of the 'preferred Vform of the invention is for the purpose of complying with Section 112, Title 35, of the U.S. Code and that the claims should be construed as -broadly as priorv art will permit.
Iclaim: 1. A titrator. electrode pair construction for partial immersion in solutions such as are employed in mercaptan and olefin titrations and comprising a one-piece body of polytetrauoroethylene bar stock, said body having a pair of substantially straight, small-diameter drill holes opening through its lower end, one of said holes being larger than the other, and a substantially straight, large-diameter drill hole opening through the upper end of the body and communicating with both of the small-diameter holes at the upper ends thereof, a socket of precious metal mounted within the lower end of the larger of said smalldiameter holes in force-ht engagement with integral portions of said body -bordering and surrounding the same, said socket having a tapped bore opening axially through its lower end, a consumable electrode of the same material as said socket and having a threaded upper end engaged in the tapped bore thereof, a second precious metal electrode mounted Within the other of said smalldiameter holes in force-tit engagement with integral portions of said body bordering and surrounding the same. with `said integral portions of said body surrounding said socket and said second electrode being under compression to conform to the surface configuration thereof in liquid-tight engagement therewith, said electrodes projecting from the lower end of said body, a cap of insulating material mounted in the said large-diameter hole and carrying a pair of external terminals, and wires totally within said body and connecting said terminals to said socket and said second electrode.
2. The electrode pair construction of claim 1 wherein said body, at its lower end, has a recess surrounding the lower end of the larger of said small-diameter drill holes to form an outwardly facing ring-like yshoulder substantially tiush with the lower end of said socket, and a washer of polytetrailuoroethylene is disposed in said recess in snug-fitting telescoping relation over said consumable electrode and in abutting engagement with said shoulder.
References Cited in the ile of this patent UNITED STATES PATENTS 1,544,052 Avery June 30, 1925 1,829,692- Walker Oct. 27, 1931 2,025,189 Yanchenko Dec. 24, 1935 2,042,534 Krause June 2, 1936 2,208,023 Ellis July 16, 1940 2,691,971 Dutterer Oct. 19, 1954 2,776,940 Oliver Jan. 8, 1957 2,881,125 Waterman Apr. 7, 1959 OTHER REFERENCES Yelton: Transactions of the Electrochemical Society, vol. (1946), pp. 331-339.