US1077920A - Electrode. - Google Patents

Description

R. H. STEVENS.

ELEGTRODE.

APPLICATION FILED JAN. 27, 1913.

1,077,920, Patented Nov, 4, 1913.

UNITED STATES P TENT OFFICE.

ROYALH. sTEvENs, or sanr LAKE ci'rY, UTAH, assionon 'ro UNITED STATES smnmme, nnrmme & MINING couramr, or PORTLAND, MAINE, A conrona- TIQN or MAINE.

The present invention relates to electrodes,

and more particularly to electrodes for use in electro-plating; electro-metallurgy and for electric batteries and cells. The object of the present invention is to cheapen thegeost of such electrodes, and at the same time -to' provide electrodes which are capable of withstanding the prejudicial effects of the baths in which they are placed, or the heat to which they may be subjected.

lVith the above object in view, one feature of the present invention relates to elec-. trodes for electrolyzing solutions and fused compounds to obtain their anode andcathode products. A narrower aspect of this feature relates more particularly to anodes for use in the electrolysis of sulfuric acid and sulfate solutions in which the anode must withstand the effects of the oxygen liberated at the anode, and in the electrolysis of solutions and fused compounds in which the electric current liberates such gases as oxygen, chlorin, bromin, iodin', fiuorin, cyanogen, and the like, or their compounds at the anode.

Another object of the present invention is to provide cheap and durable electrodes for electric resistance furnaces.

Still another object of the present invention is to provide electrodes for use in electric cells and storage batteries to replace the more expensive platinum and less durable carbon electrodes.

In the drawing, the present invention is illustrated as embodied in an iridium-plated tungsten electrode for use in an electrolytic bath. The iridium plating covers the portion of the electrode which is to be immersed in the electrolyte. While for the sake of illustration, the iridium plating is shown as having an appreciable thickness, it is to be understood that in the actual electrode,

65 the plating is a very thin electro-plating,

Specification of Letters taunt. Application filed January 27, 1913. Serial a... 744,541.

'nrncrnonn.

Patented'Nov. 4, 1913.

lutions, but does not form a good anode.

It is found that the bare tungsten, when used as an anode, does not readily allow the electric current to pass between the anode and the solution. I have, however, found that the tungsten forms a good anode if its surface is rendered conducting by means of a metal of the gold group, and more particularly platinum, iridium, ruthenium or gold. These metals are insoluble in any ordinarysolution and resist almost all reagents. They are non-oxidizable and refractory. Specific claims for the use of iridium in this capacity, and broader claims for the use ofmetals having the characteristics of iridium and platinum are presented in this application. Specific claims for the use of platinum in this capacity are presented in my co-pending application, Serial No; 652,020. One function of the gold group metals is to render the surface of the electrode conducting, and the term conducting, as used in the specification and claims with reference to the surface of the electrode, is intended to refer to the property of the surface of permitting an electric current to pass between the surface and the bath in which the electrode is placed. To render the'surface conducting, it is necessary that the gold group metal be present at the surface of the electrode. This may be done by uniting the tungsten and the gold group metal either by plating the tungsten electrode with the gold group metal, or by alloying the tungsten with the gold group metal. In order to use a minimum of the costly gold group metal, lating is preferable. However, in an a loy,

the gold group metal will still be present at the surface and render it conducting.

.Although plating is preferred, neverthe group meta-l need not be a true alloy. A

the electrode by means of a num ing processes which are known to chemists. I have, however, found that the following processes of plating give good coatin s.-.

When iridium is the plating metal, t e plating is done in an electrolyte composed of iridic or iridious chlorid, parts; disodium phosphate, 250 parts; and ammonium phosphate, 50 parts; all dissolved in 1,000 parts of water. This solution is boiled until all free ammonia is expelled. Water is added from time to time to replace that lost by evaporation. In the solution thus prepared, is placed the tungsten electrode to be plated. It is connected to a direct current electric circuit inwhich the tungsten electrode is the cathode and a wire or plate of iridium is used as the anode. A current of a density of about .05 ampere per square decimeter of the area to be plated, is used until a good plating of iridium is deposited upon the tungsten core.

Then, the iridiumplated tungsten electrode is removed from the plating bath.

W'hen platinum is the metal used for plating, I find that the following process gives a good coherent coating of platinum. An electrolyte is'prepared of platinic chlorid, 5 parts; di-sodium phosphate, 250 parts; and ammonium phosphate, 50 parts; all dissolved in 1,000 parts of water. This solution is boiled until all free ammonia is expelled. Water is added from time to time to replace that lost by evaporation. In the solution thus prepared, is placed the tungsten electrode to be plated. It is connected to a direct current electric circuit in which the tungsten electrode is the cathode and a wire or plate of platinum is used as the anode. A current of a density of about .05 ampere per square decimeter of the area to be plated, is used until a good plating of platinum is deposited upon the tungsten core. Then, the platinum-plated tungsten electrode is removed from the plating bath. The core or form of tungsten need not necessarily be entirely covered with the plating, as, for instance, when the plated elect-rode is to be used to electrolyze a solution, only the portion of the electrode which is to be immersed in the solution need be plated. While these are the preferred processes of plating, it is to be understood that any other plating or coating processes, which will give good coatings, may be employed.

On account of the high cost of the gold group metals used in plating, it is desirable to plate the surface with only a very thin film of the metal. This thin film, however, is sufli'cient to give the tungsten electrode so plated all of the surface conducting propr of platerties of a solid iridium or platinum electrode, and at a rea'tly reduced cost. This thin coating or 1m need not, in general, be a perfectly impervious or continuous coating, because in most baths in which the electrode is used, the tungsten itself is insoluble, so that, eyen if minute cracks or faults occur in the plating film, thetungsten beneath is not dissolved. When, however, the electrode is to be used in baths which would attack the tungsten, care should be taken to carefully. plate the tungsten with an impervious coating of the plating metal.

, Tungsten has a higher melting point than either iridium or platinum,- and consequently, the plated tungsten electrodes may be advantageously used in high temperature work such as resistance furnaces, since the non-oxidizable plating protects the tungstenfrom the oxygen of the air. Since tungsten is practically insoluble in all ordinary acid and neutral solutions, the tungsten electrodes, both bare and plated, may be used in them. The tungsten electrode is particularly adapted for use in sulfate and sulfuric acid solutions, since under all normal conditions, they do not affect the tungsten.

Other metals having the characteristics oftungsten, such as its difficult solubility or its high melting point, may be substituted for tungsten within the purview of the present invention viewed in its broader aspects. For

example, excellent electrodes may be made from tantalum either bare or plated. Tungstenis better than tantalum for use with hydrofluoric acid or fluorid solutions, since the tantalum is attacked by-them, and tantalum is better than tungsten. for alkaline solutions since it resists these solutions betterthan tungsten. Specific claims directed to the use of tungsten are presented in this application. Specific claims directed to the use of tantalum and broader claims directed to the use of metals having the characteristics of tantalum or tungsten are presented in my coending application for electrodes, Ser. No.

44,542, filed of even date herewith. The term difiicultly soluble metal, as used in the specification and claims, is intended to define a metal having the property of being difiicultly soluble'like tungsten or tantalum. The expressions non-oxidizable metal and reagent-resisting metal, as used in the specification and claims, are intended to define a metal having the properties of resisting the action of oxygen and resisting the action of reagents, like iridium or platinum. The expression refractory metal, as used in the specification and claims,'is intended to define a metal having a high melting point.

While the preferred embodiment of the present invention has been specifically described, the present inventionis not limited to its preferred embodiment, but may be embodied in other electrodes within the purview of the invention as particularly pointed out in the following claims 1. An electrode of tungsten plated with a metal'of the gold group. p

2. An electrode of tungsten plated with iridium.

3. An electrode of tungsten plated with a non-oxidizable metal.

l.- An electrode of tungsten plated with a reagent-resisting metal.

5. An electrode of tungsten united with and having its surface rendered conducting by means of a metal of the gold group.

' 6. An electrode of tungsten united with 15 and having its surface rendered conducting by means of iridium. I

7. An electrode of tungsten united with and having its surface rendered conducting by means of a non-oxidizable metal.

8. An electrode of tungsten united with and having its surface rendered conducting by means of a reagent-resisting metal.

ROYAL H. STEVENS.

Witnesses:

GEO. E. YEAnoN, H. P. Mmnnn.

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