US3114685A - Electrolytic production of titanium metal - Google Patents

Description

Dec. 17, 1963 M. B. ALPERT ELECTROLYTIC PRODUCTION OF TITANIUM METAL Filed March 20, 1950 United States Patent 3,114,635 ELECTRGLYTKQ PRUBUQTHQN (BF TITANEUM METAL Marshall 3. Alpert, Tomlrinsviile, N.Y., assignor to National Lead Company, New York, NY a corporation of New .lersey Filed Mar. 29, 195i Eler. No. %,752 4 (llaims. (\Cl. 2634-64) This invention relates to the production of titanium metal and more particularly to production of high purity ductile metal by an electrolytic method. More specifically, it relates to an electrolytic method for producing titanium metal of high purity from titanium tetrachloride.

Titanium metal has heretofore been reduced from a salt, for instance the tetrachloride, by direct chemical reduction employing a metallic sodium or metallic magnesium reducing agent. Such methods are described in the literature, for instance the Hunter Process in Journal of American Chemical Society, volume 32, page 330, in 1910, and the Kroll Process in US. Patent No. 2,265,854. While these methods have produced metallic titanium, they sufier from a fundamental economic disadvantage in that the cost of the metallic sodium or metallic magnesium is relatively high and the processes are expensive to operate. Actually, the reducing agent must generally itself be first reduced to metallic form by an electrolytic process from either an oxide or a chloride and this in turn used for reduction of titanium tetrachloride. The total processing cost is therefore considerably greater than if the titanium were reduced primarily electrolytically from a titanium salt.

Production of titanium metal by direct electrolysis on a practical basis has not heretofore been accomplished. Aqueous solutions of titanium tetrachloride apparently cannot be employed since only thin films of impure metal have been reported. Titanium tetrachloride itself is nonconductive, therefore, this salt cannot be electrolyzed directly by itself. Nor can titanium tetrachloride be dissolved and electrolyzed in molten salt baths primarily because of its relatively low boiling point and non-ionic nature which precludes any appreciable solubility at the temperatures required for fusion of the baths.

it is a principal object of this invention to provide a method whereby titanium metal of high purity may be produced electrolytically. A further object of this invention is to provide a method for electrolytic production of titanium metal in convenient form for re-rnelting. A further object is to provide an economical direct method for electrolysis of titanium tetrachloride. These and other obects of the invention Will be apparent from the following complete description of this invention.

This invention in its broadest aspects contemplates electrolysis of a educed titanium chloride employing a molten salt electrolyte in a cell divided into cathode and anode compartments by a porous diaphragm. The term reduced titanium chloride is intended to cover the compounds titanium -trichloride and titanium dichloride. The reduced titanium chloride is soubilized in the portion of the electrolyte in the cathode compartment and may be produced separately and externally of the cell or may, according to a preferred embodiment of this invention, be formed in situ in the cathodeelectrolyte. Passage of electric current through the cell results in passage of chloride ions through the diaphragm to the anode Where they are discharged as chlorine gas and reduction of titanium ions at the cathode Where they are deposited as pure crystals of titanium metal. The constituents of the electrolyte should be selected with a view to melting temperature, corrosive effects, compatibility and appropriate electrical characteristics. They may comprise metal halides or mixtures thereof and it is preferred to employ 3.,ll4fi85 Patented Dec. l?, 1963 the halides of the alkali metals and alkaline earth metals including magnesium and particularly the chlorides of such metals. Mixtures which form low melting point eutcctics are particularly advantageous.

The molten mixture in the cathode compartment may be formed by solubilizing externally prepared TiCl or TiCl or mixtures of these in the molten salt electrolyte, or preferably formed by a preliminary electrolysis step in situ, by reduction of TiCl by modification of the process and apparatus as hereinafter described in detail.

A type of apparatus suitable for producing titanium metal according to the process of this invention is illustrated in FIGURE 1, in which a suitable furnace is provided with heating means such as gas burners 1-1. Disposed Within the heated zone is cell container 12 which is made from a corrosion resistant material such as fused impervious silica and preferably protected externally by a metallic sheath 13 for instance of stainless steel or other metal resistant to the heat effects involved. The cell container 12 is filled or partially filled with electrolyte 14 in which is suspended cathode 15 which may preferably comprise an elongated plate of a noble metal such as tantalum. The anodes 16 may be formed of graphite rods and are submerged in the electrolyte. The cathode is separated from the anode by a porous diaphragm such as by porous cup l7 which surrounds the immersed portion of the cathode to form a cathode compartment.

Cover 18 is provided to enclose the top of the cell and contains means W for admission of inert. :gas such as argon or helium to protect the surface of the molten electrolyte. The space above the electrode compartments is suitably enclosed as by cover 20 and provided with means as pipes 21 for carrying off the chlorine released at the anode.

The diaphragm used in the cell may be constructed of any porous material which will Withstand the temperature and corrosiveness of the salt bath and Will permit the flow of ions but prevent the flow of liquids and gases through the diaphragm. Satisfactory results have been obtained by the use of a fused alumina porous diaphragm. A diaphragm which is capable of passing particles of sizes up to from 1 micron to 20 microns in aqueous media has been successfully employed in the electrolytic process. The upper portion of the diaphragm which extends above the surface of the salt bath may be constructed of non-porous material which will act as a nonporous top section on the diaphragm if desired in order to insure complete separation of the chlorine gas evolved during the entire electrolysis process.

The electrolyte preferably comprises a molten mixture of a halide salt of an alkali or alkaline earth metal including magnesium, particularly the chlorides, which may be employed singly or in combinations. Mixtures which form low melting point eutcctics are most convenient. It is particularly advantageous to employ a mixture of 27 parts of sodium chloride and 73 parts of strontium chloride by weight; such mixture has a melting point of about 569 C., and in addition appears to affect beneficially the character of the deposited titanium metal.

Titanium trichloride and/ or dichloride may be previously obtained by conventional methods such as that described in an article by A. Stahler and F. Bachran, entitled To the Knowledge of Titanium, Berichte der Deutschen Chcmischen Gesellschaft in volume 44, page 2906, published in 1911, and simply mixed with the electrolyte in the cathode compartment and the mixture maintained molten. Alternatively and according to a preferred embodiment of this invention the reduced titanium chlorides are formed in situ in the cathode compertinent to produce the electrolyte in a preliminary electrolysis step. In this embodiment titanium tetrachloride, a common chemical of commerce, is employed as the starting raw material and is treated in a modified form of cell. To accomplish formation of the electrolyte containing reduced titanium chloride, the alkali or alkaline earth metal salt, or mixture is maintained molten in an electrolytic cell partitioned in a manner similar to that illustrated in FIGURE 1. Modification of the cathode arrangement as shown in FIGURE 2 however is preferred.

In this construction the cathode is formed as a hollow tube 22 preferably of tantalum or other noble metal lined for protection with silica liner tube 23. The titanium tetrachloride gas is passed downwardly through tube 23 and on emerging from the open submerged bottom end thereof the TiCL, gas bubbles rise in juxtaposition to the surface of cathode 22. At the same time electric current is passed between the cathode and anode in amount and at a rate proportionate to the rate of TiCl addition to the system so that this compound is reduced either to the trichloride, a mixture of triand dichloride, or completely to the dichloride with liberation of chlorine at the anode. A total amount of electric current required for reduction of the tetrachloride to the trichloride is theoretically one faraday per mole of TiCL; and an additional faraday is required to convert the trito the dichloride. Therefore, 2 faradays per mole theoretically are required to convert TiCL; to TiCl Due to current efficiency, slightly more than the theoretical is actually required which may be in the order of 2.2 faradays per mole. It is preferred to add this amount of current over the period of tetrachloride addition to the cell so that the so-formed cathode electrolyte will consist substantially of TiCl dissolved in the molten salt.

It has been found that the character of the metal produced is affected by the type of reduced titanium chlorides present in the electrolyte during the electrolysis to metallic titanium. Titanium dichloride in the electrolyte produces a coarsely grained deposit admirably suited for remelting to pure metal while the trichloride produces more finely-powdered products which generally tend to absorb more impurities and are more difficult to consolidate into remelted ingot form. It is therefore desirable in order to obtain the best type of final deposit, to conduct the formation of the electrolyte so as to prevent premature reduction to metal, and to reduce the tetrachloride substantially completely to the dichloride. This is best accomplished by regulating the rate of current input to the cell so that the required amount of current is passed during the time that the tetrachloride vapor is being bubbled through the electrolyte. In any event, to prevent premature reduction to metal, the rate of current input should not be faster than the corresponding ideal rate of TiCL, gas flow. Under certain conditions it may be convenient to regulate the current input so that there is slightly less than that required to reduce to TiCl the amount of TiCL; being fed to the cell. After the total amount of TiCl is bubbled through the electrolyte an amount of current sutllcient to complete the reduction of the titanium chlorides to TiCl is added, preferably at a slow rate.

It will be found that the reduced titanium chloride will be miscible in all proportions with the salt mixture. For practical operating efficiency, however, it is preferred to form a cathode electrolyte containing from 1% to 50% by weight of reduced titanium chloride.

After the cathode electrolyte containing the reduced titanium chloride is formed the reduction to metal is conducted. In cases where the electrolyte, containing preferably titanium dichloride, is formed in the cell as described above, the hollow cathode is removed and replaced by the deposition cathode of the type illustrated in FIGURE 1. An additional 2 faradays of current per mole of TiCl are now required to reduce TiCl to metallic titanium and a correspondingly greater amount to reduce any TiCl present.

As previously stated it is desirable to electrolyze to metal the titanium values from a mixed chloride salt bath in which the titanium values are present as titanium dichloride. If the cell is approximately 2.0 volts after 2 faradays per mol of TiCl have been added to the cell, substantially all of the titanium values will have been reduced to titanium dichloride.

In carrying out the electrolysis of the titanium dichloride, the apparatus shown in FIGURE 1 may be successfully employed. Titanium metal is deposited on the metal strip cathode as the reduction to metal proceeds. During the deposition of the titanium metal from the fused salt bath the impressed voltage across the cell should be maintained preferably at about 4.0 volts with a cell of about 2.0 volts. When substantially all of the titanium values have been removed from the fused salt mixture and deposited on the cathode, a sharp rise in the cell from about 2.0 volts to 3.3 volts will be obtained. This sharp rise in the cell may be used as an indication as to when substantially all of the titanium values have been removed from the salt bath.

The cell is operated at a relatively high current density, a typical cathode current density being about 0.8 ampere per square centimeter. Good results may be obtained Within a broad range depending on the cell characteristics and operating conditions, generally between 0.1 and 3.0 amp. per square centimeter. At this current density titanium metal is deposited on and adheres to the cathode as coarse crystalline particles. These particles are coarse-size crystalline granules which usually have an individual particle size greater than 0.15 milli meter. A satisfactory size range from 0.15 millimeter to l.0 millimeter is usually attained. The titanium metal deposit is bulky and it may often be convenient to withdraw the cathode strip from the cell periodically and replace it by a fresh cathode strip so that continued plating of the metal may be accomplished.

The cathode strip containing the titanium metal deposit when removed from the cell should be cooled out of contact with the atmosphere. Means to maintain an inert atmosphere in a cooling chamber above the cathode compartment may be provided to protect the titanium. metal deposit from external atmosphere during the cooling period. After the titanium metal deposit is cooled to substantially room temperature the cathode and deposit are removed and the Ti metal is leached preferably in a weak acid solution, e.g. 10 grams per liter HCl, to dissolve the adhering soluble chloride salts. The granules of Ti metal deposited on the cathode adhere sufiiciently so that the cathode and deposited metal may be removed as a unit from the cell. Subsequently, however, no difliculty is encountered in stripping the metal from the cathode and if desired the complete cathode and deposit may be immersed in the leaching acid and this effects removal of the Ti metal from the cathode surface. The leached titanium metal is then washed with water, dried and melted or otherwise treated or fabricated according to known methods into useful articles of commerce.

In order to illustrate the operation of various embodiments of this invention the following examples are shown:

EXAMPLE I Using the cell shown in FIGURE 1 a fused salt electrolyte consisting of 7,300 grams of strontium chloride and 2,700 grams of sodium chloride were added to the cell. 625 grams of titanium dichloride were added to the salt mixture in the cathode compartment. This mixture was heated to 700 C. An electric current was passed through the cell at 60 amperes with an impressed voltage of approximately 4.7 volts for 4.2 hours. This cell had a cathode current density of about 1.3 amperes per square centimeter and a cell resistance of 0.04 ohm. Titanium metal was deposited on the cathode at the rate of about 0.7 gram per minute and chlorine was liberated at the anode. For operating convenience the cathode was removed every 20 minutes into a cooling chamber provided above the cell and a new strip cathode was placed in the cell and the deposition was continued. The titanium metal removed from the cell was cooled on the cathode in an inert atmosphere cooling chamber provided above the cell and then removed to a leaching tank. The metal deposit was leached in grams per liter hydrochloric acid solution to dissolve the occluded chloride salts. The leaching time was about 30 minutes. The titanium metal fell to the bottom of the leaching vessel, and the solubilized salts were removed by decantation and washing. The washed titanium metal was dried at 100 C. and weighed 188 grams. The titanium metal analyzed 99.5% Ti and the metal possessed a Brinell hardness of 170 after melting. The operating details of the process are summarized in Table I.

Table I Electrolyte salt mixture:

SrCl 7,300 grams. NaCl 2,700 grams. TiCl added to cathode compartment 625 grams.

Time of deposition 4.2 hours.

Temperature of operation 700 C.

Amperage 60 amp.

Impressed voltage 4.7 volts.

Cell EMF. during depositiom 2.1 volts.

Cell EMF. at end of deposition 3.3 volts.

Current density anode 0.068 amp. per sq. cm.

Cathode 1.3 amp. per sq. cm. Diaphragm 0.15 amp. per sq. cm.

Current eificiency 83.5%.

Energy consumption in cell from TiCl to Ti metal 2.85 kWh. per lb. Ti metal.

The above example shows a method for producing titanium metal from a fused salt mixture containing the solubilized titanium chloride. The following example is presented to show a method for the production of fused salt mixture which is employed as the electrolyte in the electrolytic cell.

EXAMPLE II This example shows the formation of the cathode electrolyte containing reduced titanium chloride by reducing titanium tetrachloride electrolytically. The apparatus for producing the fused chloride salt mixture may be carried out in the electrolytic cell shown in FTGURE 1 modified according to FTGURE 2 which provides means for introducing the titanium tetrachloride into the cell, represented as a hollow tube cathode which has an inert silica liner. Titanium tetrachloride vapors were passed through the silica liner in the tube and enter the salt bath at the lower end of the cathode.

10,000 grams of a chloride salt electrolyte consisting of 7,300 grams of strontium chloride, and 2,700 grams of sodium chloride were placed in the cell, i.e. in both the cup 17 and cell container 12, and heated to 700 C. Titanium tetrachloride vapors were added at the rate of 3.2 grams per minute through the hollow cathode into the fused salt bath. Simultaneously an electric current of 2.2 faradays per mol of titanium tetrachloride was added at 60 amperes with an impressed voltage of 3.5 volts. At the current rate of approximately 2 faradays per mol of titanium tetrachloride the titanium tetrachloride vapors were discharged into the fused salt bath at the open end of the hollow cathode and the bubbles formed immediately disappeared as the titanium tetrachloride was reduced to titanium trichloride and titanium dichloride and were immediately solubilized in the electrolyte. The operation was continued for approximately 5.2 hours at which time 1000 grams of titanium tetrachloride had been added to the cell and substantially 100% was solubilized in the salt mixture as titanium dichloride.

The electrolyte at this stage comprising 7,300 grams of strontium chloride and 2,700 grams of sodium chloride contained 625 grams of dissolved titanium dichloride in the cathode compartment.

The hollow cathode was then removed from the cell and replaced with the strip cathode shown in ZFXGURE 1 and the remainder of the electrolysis of the titanium dichloride-containing electrolyte was conducted in the same manner as described in Example I. The operational de tails of the two step process are summarized in Table ll.

Table II FIRST STEPSOLUBILIZING THE TITANIUM VALUES Electrolyte salt mixture:

SrCl 7,300 grams. NaCl 2,700 grams.

Rate of TiCl addition 3.2 grams per minute.

Time of addition 5.2 hours.

Temperature of operatiom--- 700 C.

Amperage 60 amp.

Impressed voltage 3.5 volts.

Cell EMF. at end of addition of TiCL 2.0 volts.

Current density anode 0.068 amp. per sq. cm.

Cathode 0.7 amp. per sq. cm. Diaphragm 0.15 amp. per sq. cm.

Current efliciency Energy consumption in cell 0.79 kwh. per lb. of

TiCl

SECOND STEP-DEPOSITION OF TITANIUM ItIE'IAL TiCl in cathode compartment 625 grams.

Time of deposition 4.2 hours.

Temperature of operation 700 C.

Amperage 60 amp.

impressed voltage 4.7 volts.

Cell EMF. during deposition 2.1 volts.

Cell at end of deposition 3.3 volts.

Current density anode 0.068 a-mp. per sq. cm.

Cathode 1.3 amp. per sq. cm. Diaphragm 0.15 amp. per sq. cm.

Current efiiciency 83.5%.

Energy consumption in cell from TiCl 2.85 kwh. per lb. of

Ti metal.

Combining steps one and two the overall yield of titanium metal was 75% with a current efficiency of 74.6%. The total cunrent consumption in the cell was 5.5 lrwh. per pound or" titanium metal produced from titanium tetrachloride. The titanium metal produced was also ductile and possessed a Brinell hardness of 170.

EXAMPLE Hi This example is presented to show a further embodiment of the present invention. This example was run at a higher initial amperage during the TiCl addition. After the reduced titanium chloride had been solubilized in the electrolyte the amperage was lowered to convert all of the titanium values to TiCl before depositing titanium metal on the cathode.

7,300 [grams of SrCl and 2,700 grams of NaCl were added to the cell. TiCl was added through the hollow cathode at the rate of 5.4 grams per minute. The amperage was held at amps. with an impressed voltage of 4.3 volts for 3.1 hours. The cell EMF. at the end of the TiCl addition was 1.9 volts. The amperage was then cut to 30 amp. with an impressed voltage of 2.8 volts and was continued for 15 minutes until the cell was 2.0 volts which indicated that substantially all of the titanium values were reduced to TiCl During this period no TiCl was introduced through the hollow cathode, however, argon gas was bubbled through the cathode compartment to agitate the electrolyte. The hollow cathode was them replaced with the strip cathode. The amperage was then increased again to 100 amp. with an impressed voltage of 6.0 volts and metal was deposited on the cathode during the following 2.5 hours. Table III shows the operational details of this run.

Table III FIRST STEPSOLUBILIZING THE TITANIUM CHLORIDES Electrolyte salt mixture:

SrCl 7,300 grams. NaCl 2,700 grams.

Rate of TiCl addition 5.4 grams per min.

Time of addition 3.1 hours.

Temp. of operation 700 C.

Amperage 100 amp.

Impressed voltage 4.3 volts.

Cell at end of addition of TiCl 1.9 voits.

Current density anode 0.11 amp. per sq. cm. Cathode 1.1 amp. per sq. cm. Diaphragm 0.25 amp. per sq. cm.

Current efficiency 90%.

SECOND STEP-COMPLETION OF TiClz FORMATION Salt mixture present Same as above.

Rate of TiCl, addition None.

Agitation with argon gas Rapid.

Time of operation 15 minutes.

Temp. of operation 700 C.

Amperage 30 amp.

Impressed voltage 2.8 volts.

Cell E.M.F 2.0 volts.

Current density anode 0.034 amp. per sq. cm.

Cathode 0.35 amp. per sq. cm. Diaphragm 0.07 amp. per sq. om.

THIRD STE-P-DEPOSITION F TITANIUM METAL Salt mixture present Same as above.

TiCl in cathode compartment--. 625 grams.

Time of deposition 2.5 hours.

Temp. of operation 700 C.

Amperage 100 amp.

Impressed voltage 6.0 volts.

Cell EMF. during deposition 2.1 volts. Cell at end of deposition 3.3 volts.

Current density anode 0.11 amp. per sq. cm.

Cathode 2.1 amp. per sq. cm. Diaphragm 0.25 amp. per sq. cm.

Current efficiency 85.1%.

Combining steps one, two and three the overall yield of titanium metal is 75% with a current efliciency of 74.1%. The total current consumption in the cell was 6.86 kwh. per pound of titanium metal produced. The titanium metal produced was ductile and had a Brinell hardness of 160. The metal analyzed 99.6% titanium.

It has been shown by the above examples that ductile titanium metal of high purity may be obtained electrolytically from a titanium salt, e.g. titanium tetrachloride. It has. further been shown that the reduced titanium chlorides, i.e. trichloride and dichloride, are soluble in a fused salt bath and may be electrolyzed directly to titanium metal. Further that titanium tetrachloride may be directly reduced to trichloride and dichloride electrolytically and by such reduction the titanium values are rendered soluble in a fused salt bath electrolyte.

By this process titanium metal of high purity is obtained by a direct and economical electrolytic method. The metal produced is ductile and is obtained in a convenient form for re-melting. It is produced in an efiicient manner and high recoveries of metal are obtained.

While this invention has been described and illustrated by the examples shown, it is not intended to be strictly limited thereto and other modifications and variations may be employed within the scope of the following claims.

I claim:

1. The process of producing high purity ductile titanium metal in solid form in an electrolytic cell having a cathode and an anode immersed in a molten electrolyte composed of a material selected from the group consisting of alkali metal chlorides, alkaline earth chlorides, magnesium chloride and mixtures thereof, comprising dividing said eicetroiyte into separate catholyte and anolyte portions, dissolving reduced titanium chlorides in said catholyte portion only, confining the reduced titanium chlorides to such catholyte portion, providing a passage for chloride ions from the catholyte to the anolyte portions, excluding atmospheric air from the catholyte portion, and passing direct current through the cell between the anode and cathode, thereby depositing titanium metal in solid form on the surface of the cathode.

2. A process according to claim 1 wherein the reduced titanium chloride is dissolved in the catholyte portion by introducing titanium tetrachloride below the surface of the catholyte portion in juxtaposition to the cathode while passing electric current through said cell.

3. A process according to claim 2 wherein the electric current is passed through the cell at a rate of between about 2 to 2.2 faradays per mol of titanium tetrachloride introduction.

4. A process according to claim 2 wherein the electric current is passed through the cell at a rate of more than 1 and less than 2 faradays per mol of titanium tetrachloride addition and an additional amount of electric current is passed through the cell without introducing titanium tetrachloride to complete the conversion of the reduced titanium chlorides to titanium dichloride.

References Cited in the file of this patent UNITED STATES PATENTS 745,958 Ewan Dec. 1, 1903 771,646 Kugelgen et a1 Oct. 4, 1904 1,018,802 Acker Feb. 27, 1912 1,273,223 Hirsch July 23, 1918 1,820,844 Steinbuch Aug. 25, 1931 2,734,855 Buck et al Feb. 14, 1956 FOREIGN PATENTS 13,759 Great Britain of 1904 263,301 Germany Aug. 5, 1913 615,951 Germany July 16, 1935 OTHER REFERENCES Titanium by J. Barksdale, published by the Ronald Press Co., New York, 1949, pages 41-45, 55.

industrial Electrochemistry, by Mantell (1931), page 481.

UNITED STATES PATENT OFFICE CERTIFICATE OF CORRECTION Patent N00 3, 114,685 December 17 1963 Marshall B. Alpert It is hereby certified that error appears-in the above numbered patent requiring correction and that the said Letters Patent should read as corrected below.

In the sheet of drawings lower right-hand corner strike out "Frank J. Schultz"; and for "INVENTORS" read INVENTOR Signed and sealed this 9th day of June 1964.

(SEAL) Attest:

ERNEST W. SWIDER EDWARD J. BRENNER Attesiing Officer Commissioner of Patents

Claims (1)

1. THE PROCESS OF PRODUCING HIGH PURITY DUCTILE TITANIUM METAL IN SOLID FORM IN AN ELECTROLYTIC CELL HAVING A CATHODE AND AN ANODE IMMERSED IN A MOLTEN ELECTRODLYTE COMPOSED OF A MATERIAL SELECTED FROM THE GROUP CONSISTING OF ALKALI METAL CHLORIDES, ALKALINE EARTH CHLORIDES, MAGNESIUM CHLORIDE AND MIXTURES THEREOF, COMPRISING DIVIDING SAID ELECTROLYTE INTO SEPARATE CATHOLYTE AND ANOLYTE PORTIONS, DISSOLVING REDUCED TITANIUM CHLORIDES IN SAID CATHOLYTE PORTION ONLY, CONFINING THE REDUCED TITANIUM CHLORIDES TO SUCH CATHOLYTE PORTION, PROVIDING A PASSAGE FOR CHLORIDE IONS FROM THE CATHOLYTE TO THE ANOLYTE PORTIONS, EXCLUDING ATMOSPHERIC AIR FROM THE CATHOLYTE PORTION, AND PASSING DIRECT CURRENT THROUGH THE CELL BETWEEN THE ANODE AND CATHODE, THEREBY DEPOSITING TITANIUM METAL IN SOLID FORM ON THE SURFACE OF THE CATHODE.

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