US1524937A

US1524937A - Electrode for electrolytic conductivity cells

Info

Publication number: US1524937A
Application number: US685366A
Authority: US
Inventors: Earl A Keeler
Original assignee: Brown Instr Co
Current assignee: Brown Instruments Co
Priority date: 1924-01-10
Filing date: 1924-01-10
Publication date: 1925-02-03
Anticipated expiration: 1942-02-03

Description

Feb."3, 1925. 1,524,937

" E.A.KEELER ELECTRODE FOR ELECTROLYTIC CONDUCTIVITY CELLS Filed Jan. 10. 1924 .INVENTOR: far! A, /feeler,

ATTORNEY Patented Feb. 3, 13925,

I isaaaai pairs stares Pars-Ni orrica EARL A. KEELER,-OF OAK LANE, PENNSYLVANIA, ASSIGNOR TO'THE BROWN INSTBU- PHILADELPHIA, PENNSYLVANIA, A CORPORATION OF PEN-N1 mnn'r COMPANY, SYLVANIA.

ELECTRODE non ELECTROLYTIC (EONDUCTIVITY cams.

Applicationtled January 10,1924; serial No. 685,366.

To all whom it may concern." j

Be it known that I, EARL A. KEELER, a' citizen of the United States, and a resident of Oak Lane, county of Philadelphi ag State 5 of Pennsylvania, have invented certainnew and useful Im rovement's in Electrodes for Electrolytic onductivity Cells, of which the following is a specification.

The present invention relates to electroto lytic conductivity cells,'-and more particularly to improvements in the electrodes used in conjunction with such cells.

Electrolytic conductivity cells are used to measurethe conductivity of chemical solu-l.

1e tions, to determine the amount of salt, al-

, kali or acid in the solution, and in carrying out this measurement the two electrodes of the cell are immersed in the solution and the resistance to current flow determined by meansof a Wheatstone bridge circuit, which is the more general method of making such determination. The resistance of the electrolytic conductivity cell constitutes one arm of the bridge. In measuring the conductiv- 2 ity of chemical solutions by this method a serious difiiculty arises in that this passage of current between the electrodes, results in the evolution of a gas, which deposits as a thin film upon. the electrode, and produces 0 an eflect known as polarization, and while this deposit is practically invisible it creates sufficient increase in the resistance offered to current flow as to introduce an error into the reading of the conductivity-of the. solu% tion. In other words, this thin film of gas produces an increase of resistance which indicates an apparent. change in electrolytic conductivity of the solution, and therefore indicates an apparent change in the amount 40 I of dissolved materials.

. Various 'meanshave been triedfor minimizing the errors of polarization, one of which is to increase the area of the electrodes so that the current density is reduced and the evolution of gas distributed over a greater area, but this is impractical because of the space required. The more widely used means for reducing the errors due to polajization consists in employing blectrod s 60 which are made of a noble metal, such as platinum, gold or palladium, but even this means has disadvantages, namely, a prohibitive cost if the electrodes are made large enough to fiilfil the requirements oi operation, and if made, as they generally are, relatively small and delicate, they become broken and require constant repairing. The

' noble metals are used .bboause platinum black or other depolarizing Urea-11s can be readily deposited upon theexposed surfiace.

It is an object of the present invention to retain all the advantages accompanying the use otno'bl'emetal electrodes but tosecure the ruggedness and strength necessary to meet the severe requirements of commercial use. It is also an object of the invention to provide an improvedoelectrodefor electroy lo conductivity cells which not only operates in an improved manner but can be manufactu'red and maintained at a relatively low cost.

In the accompanying drawings, Fig. 1 represents a section of' an electrode embodying oneform of the present invention; Fig. 2

represents a side. elevation in part section of one form of an electrolytic conductivity cell employing l electrode of the present invention; Fi .3 r resents a diagram of a circuit by which the conductivity ofkthe solution is measured with a cell embodying. the present invention; and Fig. 4 represents an electrolytic conductivity cell embodyinganother form of the invention partly broken away to show the tlI'OdSL I f I 'Referring to the drawings, one form of the present invention comprises an electrode or terminal 10, which is mounted on a base arrangement of the elec- 11 of porcelain or other suitable insulating material through which a lead wire of the electrode can be conveyed to the electric circuit without making contact or otherwise short qircuiting the other lead of the cell.

For the purpose of providing an electrode of substantial and rugged form, but one tages of the delicate and expensive electrodes '95 which retains all the efliciency and advanmanufactured from a noble metal, such as platinum, gold or palladium, the present electrode 10 is formed of a base metal body strength and ruggedness sothat the electrode will stand jlip under hard usage and 'be unaffected by the necessary frequent 12, ofsuch size and configuration as to give prises a tubular member 18, which has able plating process a coating 13 of platinum, though this is only by Way of example, and it will be understood that the coating so deposited may be of any other suitable noble metal, the result being that the base metal has its surface transformed from one subject to corrosion and unsuited to electroplating and deposition (it-depolarizing film to one resisting corrosion and suited to the deposition of a depolarizing film.

As a means for minimizing the effect known as polarization, namely, the formation of a thin film of gas over the surfa e of the electrode, the body 12, with its coating 13 of platinum or other suitable metal, is subjected to a further electroplating operation in asolution of approximately 3. per cent platinum'chloride in order to Form a film 14 over the surface of .the platinum coating 13, which is known as platinum black, or, in the case of palladium, as palladium black, which film has the property of increasing the surface area of the platinum electrode and of absorbing the gases which are given off when cin'rent passes from one electrode to the other through the solution.

Thus, the complete electrode or terminal is made u of a substantial body part comosed o a base metal and upon which there 1s first an electroplated coating of a noble metal and last an absorbent 'de osit or film, such, for example, as platinum iilack.

In Fig. 2, an electrode 10, constructed and described -in connection with Fig. 1, is shown, mounted axially on a porcelain insulator 15 and in electrical connection with a binding post 16, to which one wire 17 of the electric circuit is arranged to be connected. In this form of cell the second electrode or terminal of the circuit comthreaded connection with the reduced neck of a metal plug 20, which has its body portion exteriorly threaded as shown at 21 for the purpose of connecting the cell to a pipe or other receptacle in'which the liquid under test is placed. This plug 21 is provided.

with a suitable hexagon surface 22, whereby it can be gripped with a wrench for; tightening in place, and also has a stuffing box structure 23 to prevent leakage of the liquid outwardly through the cell. At any suitable location in the metal body of the plug 21, connection may be made for a return wire 24 of the circuit. which includes the conductor 17. In order to bring-the solution under test in the proper relation withthe electrodes 10 and 18,-the electrode 18 is provided with suitable perforations 25 which permit the liquid or solution to circulate freely within the electrode '18 and about the electrode 10. The cell of the character shown in Fig. 2 in operation is located in one arm of aWheatstone bridgecircuit,

as shown at 26, the other arms of which have

resistances

27, 28 and 29 of values sista-nce is made bya galvanomcter 30 in the usual manner. The current from a source 31 is supplied by conductors 32 and 33 to the bridge, thus,"completingthe circuit by which current passes through the cell 26 and by the resistance of this solution in whi h the cell is immersed its conductivity can be determined from a reading of the galvanomcter;

In Fig. 1 another form of the invention is shown in which athreaded plug 33 forms a casing enclosing two electrodes 3-1 and 35. each of theconstruction as described in conjunction with the electrode 10, and the two together torming terminals of the same circuit, which are mounted in spaced relation '\\'ithin a perforated tube 36 through which the test solution .has free circulation. Electrodes 34 and are resp'ectivelyconnccted byconducting leads 37 and 38 to the circuit in which the cell is located. In use, the conductivity cell embodying an electrode or electrodes of the present invention is adapted-to be mounted in a pipe line through which a solution under test is circulating, or it may be located in any suitable container in which is located a solution the conductivity ofwhich is to be determined. The invention may be embodied,

described my invention, I

electric circuit and arranged tobe sub merged in a solution under test, one of said electrodes being formed of a base metal body plated with a noble metal and having a depolarizing film deposited thereon, and a body mounting said electrodes in insulated spaced relation,

'2; In an electrolytic conductivity cell, a

pair'of electrodes forming terminals of an electric circuit and arranged to be submerged-in a solut on under test, one of said electrodes being formed of a base metal body'plated" with platinum and having a platinum black film deposited thereon, and a body mounting said electrodes in insulated spaced relat icn.

3. An electrolytic conductivity cell comv prising a tubular'base metal electrode, a second electrode within saidtubular electrode comprising a base metal body plated with a noble metal and having a depolarizing film deposited thereon, 'a base mounting said electrodes in insulated spaced relation, and conducting wires, respectively connecting said electrodes to an electrical measuring circuit. I

4. An electrolytic conductivity cell comprising a tubular base metal electrode, a second electrode within said tubular electrode comprising a base metal body plated. with platinum and having a platinum black film deposited thereon, a base mounting said electrodes in insulated spaced relation, and conducting wires respectively connecting said electrodes to an electrical measuring circuit.

5. An electrolytic conductivity cell comprising a tubular perforated base metal electrode, a second electrode within said tubular electrode comprising a base metal body plated with platinum and having a platinum black film deposited thereon, a base mounting said electrodes in insulated spaced relation, and conducting wires respectively connecting said electrodes to an electrical measuring circuit.

6. As a new article of manufacture, an electrode for electrolytic conductivity cells comprising a rugged base metal body with a noble metal electroplated thereon and a depolarizing film deposited on said noble metal. I I

7. The method of forming a rugged, substantial electrode for electrol ic conductivity cells which consists of e ectroplating a noble metal coating upon a relatively large base metal body and then depositing a depolarizing film upon said plated metal coat- 1n igned at Philadelphia, in the county of Philadelphia, and State of Pennsylvania, this 29th day of December, 1923.

EARL A. KEELER,