The Manufacture of Tungstic Acid from Scheelite Citation Wolochow, David (1924) The Manufacture of Tungstic Acid from Scheelite. Bachelor's thesis, California Institute of Technology. doi:10.7907/DAGK-9119. https://resolver.caltech.edu/CaltechETD:etd-07202004-104651 Abstract No Abstract. Item Type: Thesis (Bachelor's thesis) Subject Keywords: Chemical Engineering Degree Grantor: California Institute of Technology Division: Chemistry and Chemical Engineering Major Option: Chemical Engineering Thesis Availability: Public (worldwide access) Research Advisor(s): Unknown, Unknown Thesis Committee: None, None Defense Date: 1 January 1924 Record Number: CaltechETD:etd-07202004-104651 Persistent URL: https://resolver.caltech.edu/CaltechETD:etd-07202004-104651 DOI: 10.7907/DAGK-9119 Default Usage Policy: No commercial reproduction, distribution, display or performance rights in this work are provided. ID Code: 2940 Collection: CaltechTHESIS Deposited By: Imported from ETD-db Deposited On: 22 Jul 2004 Last Modified: 03 Oct 2019 23:22 Thesis Files Preview PDF (Wolochow_d_1924.pdf) - Final Version See Usage Policy. 447kB Repository Staff Only: item control page

FHE MANUFACTURE of TUNGSTIC ACID from SCHSSLITS Thesis by David Wolochow In partial fulfillment of the requirements for the degree of Bachelor of Science in Chemical Angineering. CALIFORNIA INSTITUTS OF T&CHNOLOGY Pasadena, California. 1924, INTROLUCTION, The chief source of tungsten at the present time is wolframite which is a tungstate of manganese and iron. It -is founa in numerous portions of the earth's surface and the various deposits have been more or less completely exploited. In recent years deposits of scheelite, a tungstate of calcium, have been discovered in several countries. In the United States the largest deposits are found in California and Arizona, but these have not yet been worked to any extent. Whatever the ore, the first step in the manufacture of tungsten, after the concentration of the raw ore, is the“formation of tungstic acid, The metel is then ob- tained by dehydration and reduction of the acid. Whereas the complete reduction of the acid with carbon is a comparativly simple process, the preparation of the acid from the ores presents numerous difficulties which have to be overcome before any method can be used commercially. The methods now being used are of three general tynes,- decomposition of the ore by acid treatment, by interaction with caustic alkali, or by fusion with soda ash. The descriptions of these methods which are found in the lit- erature, are of a general nature, as the processes are all patented. They deal almost wholly with wolframite. Be , The object of this research was to develop an indus- trial method for the preparation of Tunsstice acid from Scheelite. | SXPSRIVENTAL PART The scheelite used in this investigation was a sample of concentrates from Arizona. Analysis gave the follow- ing results: L6ss on Ignition 0.33 per eent Insoluble residue 19,28 " oon Tungstic Oxide (WOs) 55.10 " " Iron (Feo03) Alumina (Al:03) 2.85 " " Calcium (CaO) 20.12 +" " Magnesium (Mgo) Trace 97,70 The sample for snalysis was decomposed by repeated evaporation with hydrochloric acid and nitric acids. The undetermined constituents and experimental error amounted to 2.3%. A content of 55.10% tungstic acid (woz) corresponds to 43.7% tungsten (W), 59.4% tungstic acid (HeWOL) and 68.5% calcium tungstate (CaW0O4). Pure Scheelite contains 80.6% tungstic Oxide (WOg) and 19.4% lime (CaO) A number of preliminary tests were first made to determine which of the three gensral methods was best Be for decomposing the scheelite. Concentrated hydrochloric acid attacked the ore only after long boiling. The pre- ‘aipitete of tungstie acid seemed to have an apperent specifie gravity, less than that of the undecomposed material, but complete separation of the two was difficult. Boiling with caustic solutions as strong as 50% NaOH under atmospheric pressure, did not decompose the sample. to any appreciable extent. Fusion of the scheelite with soda ash seemed to be the most promising, and hence it was decided to confine ex- & . perimentation to the development of this method, The procedure consisted of fusing the intimately mixed ore and flux material contained in a fireelay crucible in a small gas-fired furnace, The melt ws lixiviated with water, the insoluble residue filtered off, the clear filtrate concentrated somewhat by evaporétion, and the tungstic acid precipitated by pouring the hot solution into boiling hydrochloric acid. The scid vas filtered off, washed with hot dilute acid (washing with water alpne conMerts some of the acid into the colloidal form which goes through the filter) and the tungstic acid dried to constan¥ weight at 110°C. It was found that best yields could be obtained when 4 4. the molten mix was poured directly into water. This could, however, be successfully done only within a narrow ranze of conditions. The precipitation of the tungstic acid was not complete, but that remaining in solution eould be recovered by neutralizing the acid filtrate with caustic soda, filtering off the precipitate of iron and @lumina, and precipitating a second time by pouring into hot hydréchloric acid. Complete decomposition of the scheelite by fusion was not obtained. The residue remaining after lixiviat- ion always contained tungsten, about one third of which could be recovered as -tungstic acid by treatment with hydrochloric acid, dissolving out the precipitated tunegstic acid with ammonis and reprecipitating with hydrochloric acid, In none of the reactions where hydrochloric acid was used could sulfuric acid be satisfeotorily ‘gub- stituted. The average yield from the more successful runs was 50% tunestic acid and as the scheslite contained 59.4%, the recovery was thus about 85%. ‘The actual data on proportions of mix, time of- fusion, ete., are given in the appended table at the end of the thesis. OUTLINE OF THE PROCESS. The following procedure is recommended: 1. Mix 100 parts of finely ground scheelite with 60 parts of soda ash, and fuse the mixture for an hour at about 800°C, 2. Pour the molten mass into water and heat to ‘boiling with constant stirring. 3. Allow the insoluble residue to settle and pour off the clear solution. —_ 4, Evaporate the solution from (3) until the con- centration of the sodium tungstate is about 20%. 5. Pour the hot concentrated solution into 114 lbs. of hot mariatic acid and §9i1 for 15 minutes, 6. Allow the preGipitated tungstic acid to settle, pour off the acid liquor. . 7. Wash with hot water containing a trace of muriatic acid, filter and dry. 8. Neutralize the acid liquor from (6) with solid caustic soda, boil and filter from any precipitate which may form. oe 9. Pour the filtrate into 50 lbs. muriatic scid and proceed as in (6) and (7). | 10, Wash the insoluble residue from (3) with hot water. These washings are used for lixiviation in (2). ll. Decompose the residue by feats with 125 lbs. muriatie acid. 12. Allow the tungstic acid and residue to settle, pour off the liquid and wash. 13. Dissolve out the tungstie acid with 4.65 lbs, ammonia and filter from the insoluble material. 14, Pour the ammoniacal filtrate into 20 lbs. - muriatic acid and proceed as in (6) and (7). COST DATA. The cost of the materials used and value of the tungstic acid obtained was ealeulated on the besis of 100 lbs. scheelite and on current quotations. The various quantities are itemized separately to show the amounts used in the successive steps in the process. 100 1lbs.Scheelite @ 9.25 perunit .....25.59 60 lbs.Soda ash @ 1.25 per cwt...... 0.75 114 lbs.Muriatie acid 41 lbs.Tungstic Acid —@ 0.80 per cwt...... 0.90 @ 1.25 per 1b...51.25 27.15 16 lbs.Caustic soda @ 3.50 per cwt... 0.55 5.5 lbs.Tungstic Acid 50 los.muriatic acid 0.40 eescccceces 4.55 125 lbs. muriatie acid 1.00 4.65 lbs.ammonia @ .06% per 1b. ~ 0,30 44 lbs. Tungstic Acid 20 lbs.,muriatic acid 0.15 ; eeccseree 9420 1.45 $61.10 ——~—~"29 45 ; Value of product over and,.... 31.65 above cost cf materials 61.10 7. The balance shown above does not, of course, represent a net balance in favor of the process. 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