(No Model.) Y C. M. HALL. MANUFACTURE OF ALUMINIUM. No. 400,665. Patented Apr. 2, 1889. % NS2 WWWWWWWWWWWyyyy 2 2 A E. (.S. WA (90.44. vs Sowbuyle. UNITED STATES PATENT OFFICE. CHARIES M. IIAI, I, of OBERLIN, oilo MANUFACTURE of ALUMNIUM. SPECIFICATION forming part of Letters Patent No. 400,665, dated April 2, 1889. Application filed Angust 17, 1888, Serial No. 282,954, (No specimens.) To ?till whom it may concern: ium fluoride to seventy-eight parts of calcium Be it known that I, CHARLES M. IIALL, a fluoride or fluor-spar, the aluminium fluoride citizen of the United States, residing at Ober being artificially prepared by saturating hy lin, in the county of Lorain and State of Ohio, drated alumina with hydrofluoric acid. The have invented or discovered certain new and fluorides of calcium and aluminium unite in 55 useful Improvements in the Manufacture of forming a double fluoride more fusible than Aluminium, of which improvements the foll the fluoride of calcium, and, as I believe, more lowing is a specification. fusible than either constituent alone. In applications filed by me July 9, 1886, and While I prefer to use the double fluoride of February 2, 1887, numbered 207,601 and calcium and aluminium represented by the 226,200, respectively, I have described and formula CaAl,F in carrying out my process, claimed certain processes for the reduction of there are a large number of similar double . aluminium, wherein I employ fluoride salts of * fluorides of the same metals which may be aluminium or double fluorides of aluminium used and which closely resemble the one and electro-positive metals-as, for example, named, and answer almost, if not quite, as well 65 sodium or potassium-in a fused state to dis as a bath for dissolving the alumina. Thus solve alumina, and the alumina is subjected the double salt of the formula CasAl,F has to eloetrolysis when in a state of solution in been successfully employed in the electrolytic the fused salts, thereby reducing aluiminium reduction of aluminium. Whether the bath at the negative electrode, the oxygen going to employed contains proportionately more or .7o the positive electrode. The bath formed of less aluminium fluoride within wide limits. the double fluoride of aluminium and an alka seems to make little difference. line metal, as described in the above applica In the practice of my invention the fluor tion, becomes less efficient after being sub ides abovementioned are placed in the carbon jected to electrolytic action for some time. lined crucible or vessel 1, arranged in the fur 75. This change does not result from any removal nace 2, and subjected to sufficient heat to fuse of aluminium fluoride or of fluorine from the the material. Electrodes 3 and 4, formed of bath, as no fluorine is separated; but a black carbon when pure aluminium is desired, are or dark substance is formed in the bath, ap connected to a suitable electric generator, as . 3o parently from the alkaline constituent of the a dynamo-electric machine. If an alloy is de 8o same, which interferes with a free electrolytic sired, the negative electrode 4 is formed of action and increases the electrical resistance; the metal with which it is desired to alloy the hence it has been found necessary when em aluminium. Alumina in the form of bauxite, ploying the salts named to change the bath anhydrous oxide of aluminium, or any other 35 after a continuous use of the same. suitable form of alumina, preferably the pure 85 The object of the invention described herein anhydrous oxide AlOs artificially prepared, is to provide a bath wherein the reduction of is then dissolyed in the fused bath, and being aluminium from its oxide may be carried on subjected to the action pf the electric current continuously without dinhinution and without aluminium is reduced at the negative elec increasing the electro-motive force of the cur trode 4, and, if said pole is formed of some go rent. heavy metal, forms an alloy with it, which The accompanying drawing, forming apart drops of and sinks to the bottom of the bath. of this specification, is in sectional elevation Oxygen goes to the positive electrode, and a form of apparatus applicable for carrying combining therewith when formed of carbon, out my invention. - forms carbonic-acid gas or carbonic oxide, the 95 In carrying out my invention I prefer to em carbon being gradually consumed. Alumina loy. a double fluoride of aluminium and cal cium having a composition represented by the processis added is to continued. the bath from time to time as the formula CaAl,F. This composition is formed The solution of alumina in the fused bath So by one hundred and sixty-nine parts of alumin of the double fluoride aluminium and calcium ocy 2 . 400,865 is apparently heavier than the metal alumin barium resemble each other very closely and ium, and hence this metal, if-unalloyed, rises may be employed interchangeably in this pro after being reduced and floats on the surface cess-as, for example, the salts represented 55 of the bath, where it is liable to loss by oxi by the formulas. CaAl,F, BaAl,F, and 5 dation on contact with the air or with the SrAlF, may be employed in the same way and positive electrode, where it is subjected to a the salts of strontium and barium, as well as strong oxidizing action; hence when reduc other double fluorides of strontium and ing pure aluminium the crucible 1 is provided aluminium and barium and aluminium, may 6o with a cover, 5, provided with openings for be used in the mannerstated in regard to the Io insertion of the electric conductors and, the double fluoride of calcium and aluminium. escape of gas.from the crucible, and with a The salts of strontium and barium are heavier. partition, 6, of carbon extending down into than the calcium salt, but more fusible, the . the bath and from side to side of the crucibles salt of barium being the most fusible, and ap: 65. and separating the two electrodes. As the pear especially well adapted for the reduction . I5 aluminium is reduced at the negative elec of aluminium from alumina dissolved in them trode alonie, it will rise on the same side of into its alloys with heavy metals, especially the partition with said electrode, and hence copper, the negative electrode in such case will be protected by the cover, and partition being formed of copper. - from any oxidizing influences, the carbonic The double fluorides of aluminium and the Io acid gas and carbonic oxide being formed on alkaline-earth metals, barium, calcium, and the opposite side of the partition. As the op strontium resemble each other and differ from ... eration continues, the cover is removed from the double fluorides of aluminium and the fromtime theto timesurface and of the bath.aluminium removed alkaline metals, as potassium and sodium, in 25 When it is desired to form alloys of alumi that they do not change in efficiency or action nium with iron, copper, or other heavy metal, on being charged with alumina and subjected the negative electrode is formed of iron, to electrolytic action for the reduction of . copper, or other metal with which the alloy aluminium, as...is the case with the double . ... is to be formed. The aluminium, as it is re als.fluorides of aluminium and the alkaline met 8o 30 duced at the negative electrode, takes up a I claim herein as my invention- . portion thereof, and if the electrode is formed 1. As an improvement in the art of manu of heavy metal the alloy, thus formed sinks facturing aluminium, the herein-described to the bottom of the crucible. In forming method, which consists in fusing a combina- 85. alloys with heavy metals the cover and par. tion of the fluoride of aluminium and the . 35 willtition protect may bethe dispensedalloy from with,any oxidizing as the bath in fluoride of an alkaline-earth metal, adding fluences. currentalumina of to electricity the bath so through formed the and fused passing mass, a It maybe stated that means may be used to substantially as deseribed. lower the specific gravity of the bath by the 2. As an improvement in the art of manu 90 4o addition to it of other'salts lighter than the facturing aluminium, the herein - described double fluoride of calcium and aluminium, so method, which consists in fusing a combina that the pure aluminium will sinkin the com tion of the fluoride of aluminium and the bination and thus be protected from oxidation. fluoride of calcium, adding alumina to the 95 Thus by the addition to the bath above de bath so formed, and then passing a current of 45 scribed of about two-thirds its weight of the electricity through the fused mass, substan . double fluoride. potassium and aluminium, tially as set forth. - - (KAF) which is comparatively a very In testimony whereof I have hereunto set light saltisformed a composition lighter than my hand. -- - - - - - - - - - aluminium, which will therefore sink when CHARLES M HALL. 5o reduced and be thoroughly protected. Witnesses: . The double fluoride of aluminium and the W. B. CoRw IN, alkaline-earth metals, calcium, strontium, and - DARWIN S. WoLCOTT, .