US2251968A - Process for the production of very pure magnesium from magnesium ores - Google Patents

Description

C. ADAMOLI v PROCESS FOR THE PRODUCTION OF VERY PURE MAGNESIUM FROM MAGNESIUM ORES Filed Sept. 7, 1958 RSQF l/F PLEMz-WmL} In 2) e nfo 7':

jzww m W 2 1 4 P m mi m W 5 M77 F w m M4 W. In 0 L w 27 u 9 5 @f W w W 17v ,7 r w F 0 WWW m m L M m E n Patented Aug. 12, 1941 PROCESS FOR THE PRODUCTION OF VERY .PURE MAGNESIUM FROM MAGNESIUM ORES Carlo Adamoli, Milan, Italy, assignor to Perosa Corporation, Wilmington, Del., a corporation of Delaware I Application September 7, 1938, Serial No. 228,865

In Italy September 11, 1937 23 Claims.

After some early experiments based on reduction by carbon at high temperatures, work on the commercial preparation of metallic magnesium has been carried out almost exclusively in the direction of electrolytic decomposition of fused magnesium chloride. The technical difiiculties are known which must be overcome in such an electrolysis; the chemical and physical difficulties are also known which are met with in obtaining a magnesium chloride which is pure enough to give a metal which is not contaminated by other elements which cannot be removed by further melting operations, and which is sufficiently anhydrous not to give rise to magnesium oxychloride when heated. In spite of all the contrivances which have been introduced into these operations, it is Well known that magnesium cannot be freed from all the impurities which has always been suflicient to impede a use which, without these impurities, could take place on a large scale owing to the exceptionally good mechanical characteristics which the pure metal possesses. It is Well known that less than 0.2% of impurities altogether is sufficient, even When mainly due to iron, aluminum, silicon and chlorine, to cause the elasticity to drop to 70% of the value which corresponds to the pure metal, and to cause the metal to show the chemical instabillty due to which the products made of ordinary magnesium are rapidly altered and worn. For this reason it has been attempted to obtain a pure metal by distilling and subliming it, but when working according to such methods the losses due to the metal which has been consumed in the course of th further melting operations and granular condensations are so great that the cost of a pure magnesium obtained first by the electrolysis of the anhydrous chloride (under the best conditions) and then by distillation orsublimation in a vacuum is so high that it prevents the use of magnesium so obtained in large mechanical constructions.

The process according to the present invention difiers from the above mentioned processes by the fact that electrolysis is not used and that the starting materials are not purified magnesium salts, but ores which are very common in nature, such as magnesite, giobertite, talc, dolomite; that the magensium which is obtained is free from any impurity having its origin either in the ores or in the reagents which have been used, the process being performed in the course of a single direct operation and avoiding the losses of metal which are ordinarily incurred when it is necessary to melt the metal because it is not compact l enough. Finally, the process according to the invention still differs from the other processes by the fact that only a single reagent is used, which is decomposed and regenerated, and that thermal energy is consumed only in amounts corresponding to the heat necessary for liberating and evaporating the metallic magnesium which is produccd.

Heretofore it has not been customary to use magnesium fluoride as the material from which production of metallic magnesium by electrolysis of the molten magnesium fluoride which, furthermore, possesses only a small electric conductivity. Howevenwhen using a distillation process for the production of magnesium, in order to obtain pure metal, the fact that fluorine can readily combine with other elements which have a chemical afiinity for it higher than the aflinity of magnesium for fluorine, has suggested to the applicant the concept that the use of magnesium fluoride, if it were possible to produce it at a low cost, would be highly advantageous for a reduction process as compared with the use of mag nesium oxide the reduction of which, either by carbon or by any other reagent (with the exception of alkali metals which are expensive) takes place at exceedingly high temperatures at which the pressure of the magnesium vapor, the boiling point of which is about 1160 C., is so high that it is difiicult to condense it, while it is oxidized readily; on the other hand the problem of the resistance to wear of the construction materials used for the commercial contrivances which are suitable for this process, becomes thus insoluble.

In the case of silicon great difliculties are also met with because of the formation of oxidized silicon compounds with metallic oxides, the said compounds consuming uselessly a portion of the reducing metal and of the reduced metal, so that no chemical equivalency between the consumed silicon and the produced magnesium can be obtained.

The present invention relates to a process for the commercial production of metallic magnesium from magnesium ores by converting the said ores into magnesium fluoride by means of fluorine introduced once for all into an operating cycle in the form of magnesium fluoride, which is decomposed by the exchange of its fluorine thus producing'vaporized magnesium in a pure condition, which is condensed, and a fluoride of a reducing agent, from which fluoride the fluorine is extracted by any known process and caused to react on a further quantity of magnesium ore in order to form magnesium fluoride which is submitted anew to an exchange reaction with the reducing agent above referred to and so on, the fluorine thus serving in a closed cycle for converting the magnesium of the ore into magnesium fluoride and then for liberating magnesium by the action of the reducing agent and finally for the formation of a fluorine compound which converts anew through its fluorine a further quantity of magnesium from a further quantity of ore, and so on.

The production of magnesium which has been distilled from its fluoride suppposes a reaction of the following kind:

where m is a monovalent metal. In order that it may be carried into eiiect in a commercial manner and under the conditions which have been provided heretofore, this reaction would require the use of an alkali or alkaline earth metal such as sodium, potassium or calcium, the cost of production of which would be high according to the amount chemically equivalent to the magnesium which is to be liberated.

According to the process which forms the subject matter of this invention, the starting material is, therefore, a magnesiferous ore. Natural magnesite, natural carbonate of magnesium called giobertite and dolomite are well suited for this purpose; however, the fundamental operating cycle allows of the use of a material other than a magnesiferous material which is equivalent from the point of view of the process, such as, for instance, talc, steatite or other materials of the same kind. The chemical principles on which the process is based are as follows: (1) The conveying of the fluorine of the fluoride of magnesium into another compound which is such that it renders possible the displacement or the chemically equivalent quantity of fluorine, for instance in the form of hydrofluoric acid adapted for producing further magnesium fluoride; (2) The use as reducing agent of a tetravalent metalloid such as, for instance, carbon or silicon, alone or mixed with other metalloids or metals or present in compounds or combinations of the metallic type, such as carbides and silicid compounds or as alloys.

The accompanying drawing diagrammatically shows in a conventional manner a qualitative bal ance-sheet of the cyclic process according to the invention. Magnesiferous ore enters in the cycle at a; it then meets at b the fluorine of the cycle, e. g. in the form of hydrofluoric acid coming from c, to which is added a small amount of supplemental hydrofluoric acid introduced in the cycle at d to compensate for losses of fluorine. The magnesium fluoride thus formed at b, which eventually is separated from a residue which does not substantially contain fluorine and which is removed from the cycle through e, passes through I in order to be submitted to the action of a reducing agent entering the cycle at g. The reaction produced at it between themagnesium fluoride and the reducing agent delivers on the one hand, vapors of pure magnesium which leave the cycle through i and pass to the condenser and on the other hand, a fluorinated mixture which passes through 1', meets at k the reagent which stantially no fluorine and which is removed through m; the said fluorine to which is added the small amount of supplemental hydrofluoric acid entering the cycle through d, passes through c and at b meets a further portion of magnesiferous ore which is introduced into the cycle at a, in order to form further magnesium fluoride and so on.

In the case of a mixture of metallic and metalloidic reducing agents, there are two parallel reactions, one with the metallic reducing agent and the other with the metalloidic reducing agent, while either the use of the resulting metallic fluoride or metalloidic tetrafluoride are resorted to, as desired, for the regeneration of the fluorine, for instance in the form of hydrofluoric acid. By causing magnesium fluoride to react alone or mixed with other fluorides or oxides (such as oxides of the magnesium itself or with calcium which is contained in dolomite, for instance) on calcium or on calcium silicide, calcium carbide or another silicide or carbide, or on alloys of both metalloids with other elements, the following products are obtained: metallic magnesium which distills, calcium fluoride and a metalloidic tetrafluoride; out of the calcium fluoride and through the known reaction by means of strong acids, or out of the metalloidic tetrafluoride by treating the same by means of water vapour according to the process as described in the Italian Patent No. 355,502, dated September 10, 1937, the hydrofluoric acid is regenerated and is used to form again magnesium fluoride from the ore of the kind which has been used as raw material.

The decomposition of the magnesium fluoride by means of metallic calcium' takes place giving a practically total output according to the reaction:

if care is taken in adding a fluoride such as, for instance, an alkali metal fluoride adapted to maintain the melting temperature of the mass at a sufliciently low degree of temperature during the whole decomposition. For instance, for this purpose, an addition of sodium fluoride can be made which allows the reducing metal to react on the magnesium fluoride at a temperature which is sufliciently low to prevent any gradual distillation of the molten calcium which is added as the operation progresses. The final product which is obtained after the distillation of themagnesium is calcium fluoride with small quantities of other fluorides such as sodium fluoride and from this product the fluorinating reactions are repeated in a continuous cycle by the process which has been described above in the case of the use of calcium carbide.

The decomposition of the magnesium fluoride by means of calcium carbide is one example of the step of displacement of the fluorine of magnesium fluoride. In an iron retort of a suitable type contained in a muiile which'is heated with coal, oil or electricity, carbide of calcium, as available in the market is introduced preferably after having been comminuted to a fine granular condition like sand, and intimately mixed with a chemically equivalent proportion of magnesium fluoride, or preferably with a proportionally larger quantity of magnesium and calcium fluoride, when the hydrofluoric reaction is carried out on dolomite which, as is known, is a natural carbonate of calcium and magnesium. This magnesium fluoride is, for instance, obtained in a stage which will be described later on. A violent reaction takes place at the melting temperature of the magnesium and it is accompanied by a development of heat by which the calcium carbide and the magnesium fluoride are decomposed while causing the formation of magnesium which distills,'and of calcium fluoride which re- When both calcium and magnesium fluorides are present, the calcium fluoride is fan inertingredient. The magnesium vapors which distill are led to a condenser which can be formed of a As to the decomposition of the magnesium fluoride by free or elemental silicon alone, this suitably cooled iron vessel in which a rain of molten magnesium, at 700 C. precipitates from.

the magnesium vapors and the liquid magnesium which has been formed is poured into a mould with the usual precautions well known in the art. At the beginning of charging the material and during the treatment, the retort and the condenser are maintained full of inert gases such as, foninstance, methane, in order to avoid any oxidation of the escaping metal. When the larger part of the magnesium of the retort has been distilled on, which is the case after a time which varies according to the amount of the mass, but which is always short, a good-deal of the calcium fluoride and of the carbon is removed from the bottomof the retort and caused to flow as such into cold water. The calcium fluoride which has been'chilled in this manner can be readily pulverized. It can then be introduced into a mixer and transformed into a paste by being thoroughly mixed with sulphuric acid and then submitted to a 'temperatufeof 150-170 C. until all the fluorine has been removed in the form of gaseous hydrofluoric acid in a dry condition, which is caused to react in another room, for instance in a tower which is inwardly protected by compact burntmagnesite, with a finely powdered magnesiferous ore, preferably a powder of a. natural carbonate of Me or powdered dolomite, which is sprayed out into the room or tower by means of an atomizer together with carbon dioxide. The

, tower can be heated by the hot gases coming from the furnace heating the retort for the distillation of the magnesium; with this heat and with the heat which is produced by the following exothermic reaction, which corresponds to the use of the natural carbonate of magnesium:

and thenmixed with the reducing agent, for I instance calcium carbide, in the manner which has already been hereabove described; The reaction takes place in the same manner when reducing agent is used commercially according to the invention, on the basis of the fact that the silicon in a finely powdered condition and mixed with magnesium fluoride and with quick 'lime in a proportion which is chemically equivalent, causes the distillation of the metallic magnesium at the melting temperature of the mag-' nesium fluoride the reaction being as follows:

2MgFz+Si+2CaO=2Mg+SiOa+CaFz The pasty mass which remains after the magnesium has been removed by distillation is formed of a mixture of silica and calcium fluoride, from which mixture all the fluorine which is necessary for the fluorination of further quantities of giobertite or other magnesiferous ore is obtained by the above described process.

The production of hydrofluoric acid by means of the fluorine which circulates in a closed cycle in the process is based on the .reaction of the sulphuric acid on the mixture which forms the residue of the preceding reaction; in fact, through its reaction on the residue which is obtained after the distillation of the magnesium, the sulphuric operating on dolomite or another magnesiferous ore of the-same kind. 'In the cycle of treatment a chemical equivalent of each of the chemical 1' materials which are used for the reaction con- .sumed these materialsv being calcium carbide'and s.sulphuric*acid, when startingfrom natural-acacbonateof inagnesium- 111708.86 dolomite isused, "the consumption of sulphuric acid is higher due tothe presence of, calcium carbonate in the dolom mite, which ,icalcium carbonateis converted into If a calcium. fluoride inthefluorination of the mag--. nesium carbonates-from the hydrofluoric reaction room'flioiHFig.v ,1) carbondioxide is .removed, w'hichin excess with respect to the proportion of carbon dioxide which is necessary fflior; accompanying the magnesium carbonate or .the'dolomiteinto saidroom.r i is acid produces silicon tetrafiuoride which regenerates the corresponding hydrofluoric acid, for instance by the use of the process according to the Italian Patent No. 355,502.

The reduction of the magnesium fluoride by means of silicon, as well as the condensation of the magnesium, are performed in the same manner as in the first case which has beendescribed for the treatment of'extraction by-means of carbide .of calcium. An apparatus for carrying, out

the operations is shown diagrammatically in Figure 2 of the appended drawing. Theintimate mixture of silicon, magnesium fluoride and quick lime is agglomerated, for instance, by pressure and is introduced e. g. into a suitable cast iron retort I provided with an inner'protecti've lining 2 of compressed and frittedsteatite. Theretort is provided, on the onehand; with'a'conduit 3 for the 'outletof the vaporsof magnesium and, on the other hand, with an outlet [forthe fluid slag. The. charging of the agglomerated product pieces on the moltenmassisjefiected automatical y, for instance, by means of a belt 5, which takes the agglomerated product pieces and discharges them 'onto the molten mass. The

charging. chamber 6 for thefagglomeratedproducts whichtakes the briquettes outwardly a and brings them to themoltenbath of MgFz, ispreferably arranged for this purpose in the form of successive semi-closed, sections by means of partition walls 6a which com e almost in engagementwith the free 'facesof the belt5 andof the materialwhich is conveyedbythesaidjbelt;

the sections .which are formed in this jmanner are fed with fa neutral gas, such as fmthane; at

pheric pressure-at this manners-J0me; "t it 'pheric pressure or at, a neighboring: andfs glitiy- .higher pressure y e fd'eco position of the magnesiu may i possible graduall'yf to remove all t a at least from the IaStfsection,beforethe'ag mst e .p re d s h d, q tb t e imb mass, the air escaping through theffnarrow free by meals. 9

air

intervalsileit between thefwallpartitions, f 5 the sections and the. feeding or material in course-of feeding. Thus "the whole operation is performed m p inert atmosphere 1 d 'at atm' osma aw; ree sil n ves is greatly accelerated when the operation is so carried out that there are present, in the beginning, bases such as lime or magnesium oxide in proportions which are always lower than the proportions which correspond to the chemical equivalence of the amount of the siliconv which is present, while the magnesium fluoride is then gradually introduced after having been mixed with the silicon, while maintaining between them the proportions which represent the chemical equivalency. By using a magnesium fluoride containing oxide of magnesium it is possible to mod 1 erate the intensity of the reaction, which can be explained by the formation, instead of silica, of silicon oxyfluoride; this body'itself can react on the alkaline earth metal fluorides under the conditions of temperature at which the operation is carried out, and by a secondary reaction with n the basis of these equations, it is shown that. the phase of formation of the metallic magnesium is separated from the phase of forma-' tion of tetrafluoride of silicon, the recoverable 'metallic magnesium being completely liberated before the tetrafluoride of silicon can be formed. These analytical interpretations .are given, of course, for the purpose of explanation; others could also be given; it is a fact, however, that the application of this process for the commercial production allows of directly obtaining practically all the metallic magnesium which is con-"' tained in the molten mass, as well as of obtaining, also directly, the silicon'fluoride without it being necessary to pass through an intermediate re-.

action of the sulphuric acid on a silicate and fluoride slag, as explained above for the case where the decomposition of the magnesium fluoride is eflected by free silicon alone. In this case the process and the apparatus for the production hereabove mentioned are modified as regards construction and working of the retort inthat at the beginning of the production the briquettes are "formed of silicon, magnesium fluoride and magnesium oxide and that in the further operation they are formed of magnesium fluoride and silicon without oxide; the flrst briquettesare charged in a single operation at the beginning and the other briquettes are charged successivethe following reaction formula, which is synthetically expressed:

' 2MgF2+Si=SiF4+2Mg Of course, in this operation for the production of magnesium, variations of temperature and of duration, as to the successive phases are alternately met. Thus a cycle of circulation of the fluorine according to a commercial production isv obtained and .silicon is consumed only in an amount which is chemically equivalent with respect to the magnesium which is produced.

The decomposition of the magnesium fluoride by means of calcium silicid represents the mixed type .of operation according to this process by ving rise to a different circulation of the fluoride in the cycle of treatment. The reaction takes place which corresponds to the double exchange between the metallic elements by using a common silicid such as, for instance, calcium silicid which can be produced in large quantities from silica and calcium in an electric furnace at costs which are very suitable for the purpose and on such a basis that its composition is as follows:

about 25 to of calcium, 25 to 70% of silicon.

5 to 10% of iron, these contents corresponding approximately, as regards the relation siliconcalcium, to the formula SiaCa, When leaving the secondary reactions out of consideration one has first a transformation lowing equation: a

(1) SisCa+MgF2=SiaMg+CaFz according to the fol- The light metallic magnesium silicid can be separated and gives magnesium by distillation, while the silicon, as a metallic residue, is recovered in an iron-silicon alloy having still a large silicon content, which can be used directly in metallurgy." It has been found, however, that it is preferable-in many cases to re-use the magnesium silicid itself, preferably at the moment of its formation as a transforming agent for a further quantity of magnesium fluoride, no longer through the double exchange reaction between metals, but through the reaction of formation of silicon tetrafluoride. In this case the reaction which represents the transformations during the different phases is represented by the following equation:

(2) SiaMg+6MgFa=3SiF4+7Mg By this proces the fluoride whichis necessary,

' is obtained partly according to the operative ly at intervals, while the conduits through which the magnesium escapes in a gaseous condition are flrst opened in order to .let the magnesium vapors go to the condensing appliance after which they are closed and the conduits are opened process which'has been described in the case of the use of carbide and for the most part (6/7) by the operative process which has been hereabove described in the case of the use of metallic silicon alone.

The production of metallic magnesium on the basis of the above described process and according to one or the other of its practical applications can be usefully effected also by the useand the conversion of iron and silicon'alloys. It has been found that iron and silicon alloys having a high silicon content can react with the magnesium fluoride in the same manner" as the silicon itself, and also like the silicon which is contained in the calcium silicid, that is to say practically through the totality of their silicon contents.

Between a common silicon and iron alloy containing 60% of Si and 40% of Fe (60/40 alloy) and an also common alloy of iron and silicon containing of Fe and 20% of Si (80/20 alloy), a quantity of silicon is available the reactivity of which can be readily used for the above described process of production of magnesium by the action of its fluoride; by causing the silicon and iron alloy having a high content of silicon to react with the above described mixture of magnesium fluoride and base in a proportion corresponding to that which is necessary for simultaneously obtaining the magnesium and an iron and silicon alloy having a high content of iron, there is from the commercial point of view, the

great advantage that the reaction can be carried out at low temperatures and from the economical point of, view the advantage that a metallic byproduct is obtained which can be readily sold or used; it is thus advantageous to use, instead of silicon, silicon which is contaminated with iron and the price of which is much lower than that of pure silicon. The reaction, chemically expressed according to the equivalencies and according to the above mentioned reaction (R) appears as follows:

6MgF2+169.80 parts 60% Si 40% Fe: 6Mg+ 3SiF4+84. 90 parts alloy (20% Si: 80% Fe) As above mentioned, the process according to the present invention allows of directly using magnesium ores and it is characterized amongst other features in that the magnesium is always produced in a quantity which is equivalent to the fluorine which is presentat the beginning and combined with the magnesium and finally in that neither the silicon nor the carbon practically react by reduction on the oxide, but by a double exchange with the fliiorine.

One of-the remarkable properties of the process according to the invention is that it is carried out at a temperature which is not higher than 1260 C., so that it has marked advantages with respect to the former processes. In the same way iron and silicon alloys containing a reducing metal, such as, for instance, an alloy of iron, silicon and aluminum can be used for binding the fluorine of the magnesium fluoride and if desired of another metal which is combined with fluorine, and for liberating the magnesium. Thus, for instance, 12 tons of MgFz (produced by causing 6 tonsof giobertite to react on the fluorine which has been regenerated in the form of hydrofluoric acid) are treated by means of 4 tons of an alloy of 50% of Si, 35% of Al and 15% of Fe. The reaction will give 4.5 tons of-Mg which will distill, and a residue of an alloy of 60% of Fe and 40% of Si and of a fluorinated mixturecontaining the fluorine of the magnesium fluoride, from which mixture the fluorine will be removed in the form of HF which will be used for reactingon a further mass of 16 tons of giobertite, adding a small proportion of HF for compensating the losses of fluorine which have possibly taken place in the course of the operations.

'In the course of experiments for the commercial application ofthe fundamental means of the above described cyclic process for the production of magnesium, and the modifications, of the said process, the applicant has found that the said process is equally well suited for the manufacture of products formed of pure ma nesium alloyed with other metals by still using the magnesium fluoride and submitting it to the same physico-chemical conversion processes as above described.

In fact, it has been possible to obtain other metals such as ,Li, Ce, Zr, Cd, Pb in the same manner as magnesium and simultaneously with the latter, by the conversion of their compoun with fluorine by means of tetravalent metalloids or of their combinations or alloys with other metalloids, or metals, for instance carbides or silicides. It has thus been possible to obtain binary alloys and also alloys of a higher order having magnesium as their basis with very different relations between the constituents.

The raw material for alloying one or more metals with magnesium can be, for instance, an ore such as blende in the case of zinc, or in a general manner a fluorinated product obtained simultaneously or together with the magnesium fluoride (under the conditions which are indicated above for magnesium) or obtained in a similar manner or added in the course of the cyclic process according to the present invene tion. The production of various alloys of magnesium such as, for instance, Mg-Al, Mg-Sn, by the condensation of magnesium (produced according to the fundamental process as above described) in another metal in a liquid condition or in the body of alloys and more particularly alloys having a low melting point and maintained ina liquid condition in a similar manner, has also been tested with favorable results. This condensation takes place in the manner already described for the condensation of the vapours of magnesium.

Among the binary combinations which can be used the following combinations may be cited, which are quoted with the relative temperatures at which the said combinations, under given proportions, are in liquid condition and miscible with magnesium between defined limits:

"'Ag A1 560"; Ag Cd 630; Ag Cu 780; Ag Sb490; Ag Sn 480; Al Be 650; Al Cu 550; Al Sn 450;

'Al Zn 450; Cu Be 865; Cd Sb 500; Cd Sn 180;

Cd Zn 265; Cu Sb 650; Cu Sn 675; Cu Zn 595; Fe Zn 765; Li Sn 685; Li Zn 520; Sb Sn 425;

In all the cases which have been described hereinabove, magnesium and-its alloys are still obtained byfusing the process which has been described hereabove for the production oi magnesium which is not alloyed with other metals, or still better by using a process which forms an extension of the latter inasmuch as the alloy is obtained during the operation for the production of magnesium and not by a subsequent operation in which magnesium having already been separately obtained in any other manner is alloyed with another metal. By adding a zinc ore, for instance, to the magnesiferous ore which is the raw material, the transformation will take place in a similar manner to and simultaneously with that of the magnesium, and in the flnal' condensation of the metal an alloy of magnesium and zinc will be obtained in the same proportion as that in which these elements are present in the initial ore mixture.

In another case the addition may take place in a subsequent phase after the fluorination of the magnesium ore, by introducing in the cycle a fluoride which is stable but which is reducible under the conditions of the operation, such as cadmium fluoride (CdFz) obtained from cadmium ore; in this case the transformation will' take place according to the same rule, but, of course, one will also obtain in the cyclic recovery of the fluorine the fluorine from the cadmium fluoride, which fluorine will be used for fluori lnating a further quantity of cadmium ore. In the above mentioned case flnally an alloy of magnesium and cadmium is finally obtained. In a similar manner alloys of magnesium with lithium,

alloy with pure magnesium, to make the addition of another metal which has already been extracted in part, by introducing it into the phase of condensation of the magnesium vapors, as is the case, for instance, of alloying aluminum with magnesium; in doing so the aluminum has an' advantageous action as it plays the role of condensing agent at a temperature which is by 200 0. lower than the temperature of condensation when magnesium alone is present.

In this case, aluminum' can also be replaced by one of its suitable alloys; a multiple magnesium alloy e. g. an alloy Mg-Al-Cu thus is obtained. Such magnesium alloys can be furthermore produced by the process which has been described for the production of magnesium which is not alloyed with other metals, even before the phase Qf distillation, as in the case hereinabove described for the alloys of magnesium and silicon;

the latter can be produced directly in the liquid condition and may contain other metals besides' and instead of silicon, no matter whether these metals are introduced as ores with the magnesium ore or as fluorinated compounds or as free metals.

For instance, in the case of the reaction whichhas been hereinabove mentioned for the production of magnesium alone by treating'magnesium fluoride with calcium silicide, the magnesium silicide can be produced intentionally and. obtained as final product rather than in the form of .an intermediary compound. 01' course, the alloy of magnesium and silicon can also contain other metals when the latter have been introduced with sulting from the reducing treatment, treating the silicon tetrafluoride remaining after the distillation of the magnesium to regenerate the hydrofluoric acid, treating a further quantity of magnesiferous ore with said hydrofluoric acid to form a magnesium fluoride, and treating ..said magnesium fluoride with silicon at the temperature of the distillation of the magnesium and in a nonoxidizing atmosphere.

4. A cyclic process for obtaining very pure magnesium which comprises treating magnesiferous ore with hydrofluoric acid to form magnesium fluoride; treating said magnesium fluoride with an alloy of calcium with a metalloid of the group consisting. of carbon and silicon at the temperature of distillation of the magnesium and in a non-oxidizing atmosphere, condensing the magnesium vapors resulting from the reducing treatment, treating the fluorinated product remaining after the distillation of the magnesium to regenerate the hydrofluoric acid, treating a further quantity of magnesiferous ore with said hydrofluoric acid to form magnesium fluoride, and treating said magnesiumfluoride with an allay of calcium with a metalloid of the group consisting of carbon and silicon at the temperature of the distillation of the magnesium and in a non-oxidizing atmosphere.

5. A cyclic process for obtaining very pure magnesium according to claim 4, in which an al- A lay of silicon and calcium is used for the reduction of the magnesium fluoride.

6. A cyclicprocess for obtaining very pure mag nesium according to claim 4, in which an alloy of silicon and calciumis used for the reduction the silicon or with the silicon compounds which are used in the transformation cycle.

What I claimis:

l. A cyclic process for obtaining very pure magnesium which comprises treating magnesiferous ore. with hydrofluoric acid to form magnesium fluoride, treating said magnesium fluoride with calcium at the temperature of distillation of the magnesiumand in a non-oxidizing atmosphere, condensing the magnesium vapours resulting from the reducing treatment, treating the calcium fluoride remaining after the distillation of the magnesium with a strong acid to regenerate the hydrofluoric acid, treating a further quantity of magnesiferous ore with said hydrofluoric acid to form magnesium fluoride, and

treating said magnesium fluoride with calcium at a temperature of'the distillation of the magnesium and in a non-oxidizing atmosphere.

2. A cyclic process for obtaining very pure magnesium according to claim 1, in which calcium fluoride is mixed with the magnesium fluoride submitted to reduction.

of the magnesium fluoride, the proportions of silicon and calcium, respectively, being chemically equivalent to the amounts of magnesium and fluorine of the magnesium fluoride.

.1. A cyclic process for obtaining very pure magnesi'fi'm according to claim 4, in which an alloy of silicon and calcium is used for the reduction of the magnesium fluoride, the total of the silicon and of the calcium of the said alloy being so proportioned with respect to the magnesium of the magnesium fluoride that they are chemically equivalent to each other.

8. A cyclic process for obtaining very pure magnesium, which comprises treating-magnesiferous ore with hydrofluoricacid to form magnesium fluoride, treating said magnesium fluoride with a reducing agent of the group consisting of calcium and the metalloids of the group consisting of "carbon and silicon at the temperature of distillation of the magnesium and in a non-oxidizing atmosphere, condensing the magnesium vapors resulting from the reducing treatment, treating the fluorinated product remaining after the distillation of the magnesium to regenerate the hydrofluoric acid, treating a further quantity of magnesiferous ore with said hydrofluoric acid form magnesium fluoride, and treating said magnesium fluoride with a reducing agent-of the group consisting of calcium and the metalloids of the group consisting of carbon and silicon.

9. A cyclic process for obtaining very pure magnesium according to claim 8, in which the treatment of the fluoride by the reducing agent is carried out at a temperature between the melting temperature of the magnesium fluoride and 1260 C.

10. A cyclic process for obtaining very pure magnesium according to claim 8, in which alkalimetal fluoride is added to the magnesium fluoride in order to lower the temperature of the reaction.

11. A cyclic process for obtaining very pure magnesium according to claim 8, in which a supply of hydrofluoric acid is added to the fluorinated reagent which is used in the operative cycle, in order to compensate for thelosses of fluorine.

12. A cyclic process for obtaining very pure magnesium according to claim 8, in which, to directly obtain magnesium alloyed with other metals, ores of the metals to be alloyed with the magnesium are mixed with the magnesium ore introduced into the operative cycle.

13. A cyclic process for obtaining very pure magnesium according to claim 8, in which, to directly obtain magnesium alloyed with other metals, fluorinated compounds of the metals to be alloyed with the magnesium are introduced into the operative cycle with the magnesium fluoride in the phase in which the latter is formed.

14. A cyclic process for obtaining very pure magnesium according to claim 8, in which, to directly obtain magnesium alloyed with other metals, the metals tobe alloyed with the magnesium are introduced in'a liquid condition into the phase of condensation of the magnesium.

15. A process for obtaining very pure magnesium, which comprises mixing intimately a bath of molten magnesium fluoride with a re ducing agent of the group consisting of calcium and the metalloids of the group consisting of carbon and silicon, heating the mixture at the temperature of distillation of the magnesium and in a non-oxidizing atmosphere, condensing the magnesium vapors which are formed, as they are evolved, on a pure magnesium bath in a molten condition, treating the fluorinated s'lag which forms the residue of the reaction, as it is formed, to form therefrom hydrofluoric I acid, causing said hydrofluoric acid to act on a magnesium ore in order to form magnesium fluoride and introducing said magnesium fluoride into the bath of molten magnesium fluoride in course of reduction.

16. A cyclic process for obtaining very pure magnesium; according to claim 15, in which, .in order to obtain magnesium alloyed with other metals, stable and reducible fluorides of the metals to be alloyed with the magnesium are mixed with the bath of molten magnesium fluoride, the hydrofluoric acid formed from the slag which forms the residue of the reduction reaction being caused to act on a mixture of magnesium ore and of ores of the metals to be alloyed with the magnesium.

17. A cyclic process for obtaining very pure magnesium, which comprises treating magnesiferous ore with hydrofluoric acid to form magnesium fluoride, treating said magnesium fluoride with calcium in the state of a compound with a metalloid of the group consisting of carbon and silicon at the temperature of distillation of themagnesium and in a non-oxidizing atmosphere, condensing the magnesium vapors. resulting from the reducing treatment, treating the fluorinated product remaining after the distillation of the magnesium o regenerate the hydrofluoric acid, treating a further quantity of magnesiferous ore with said hydrofluoric acid to form magnesium fluoride, and treating said magnesium fluoride with calcium in the state of a compound with a metalloid of the group consisting of carbon and silicon at the temperature of the distillation of the magnesium and in a non-oxidizing atmosphere.

18. A cyclic process for obtaining very pure magnesium according to claim 17, in which calcium in the state or calcium carbide is used for the reduction of the magnesium fluoride.

19. A cyclic process for obtaining very pure magnesium, which comprises treating magnesiferous ore with hydrofluoric acid to form magnesium fluoride, treating said magnesium fluoride with a metalloid of the group consisting of carbon and silicon in the state of an alloy with a nonreducing metal at the temperature of distillation of the magnesium and in a non-oxidizing atmosphere, condensing the magnesium vapors resulting from the reducing treatment, treating the fluorinated product remaining after the distillation of the magnesium to regenerate the hydrofluoric acid, treating a further quantity of magnesifeh I ous ore with said hydrofluoric acid to form magnesium fluoride, and treating said magnesium fluoride with a metalloid of the group consisting of carbon and silicon in the state of an alloy with a non-reducing metal at the temperature of the distillation of the magnesium and in a nonoxidizing atmosphere.

20. A cyclic process for obtaining very pure magnesium according to claim 19, in which silicon in the state of a ferro-silicon alloy having a high content of silcon is used for the reduction of the magnesium fluoride.

21. A cyclic process for obtaining very pure magnesium, which comprises treating magnesiferous ore with hydrofluoric acid to form magnesium fluoride, treating said magnesium fluoride with a metalloid of the group consisting of carbon and silicon in the state of an alloy with several metals at the temperature of distillation of the magnesium and in a non-oxidizing atmosphere, condensing the magnesium vapors resulting from the reducing treatment, treating the fluorinated product remaining after the distillation of the magnesium to regenerate the hydrofluoric acid, treating a further quantity of magnesiferous ore with said hydrofluoric acid to form magnesium fluoride, and treating said magnesium fluoride with a. metalloid of the group-consisting of carbon and silicon in the state of an alloy with several metals at the temperature of the distillation of the magnesium and in a nonoxidizing atmosphere.

22. A cyclic process for obtaining very pure magnesium according to claim 21, in which sill-- con in the state of an alloy of silicon, iron and aluminum having a high content of silicon and aluminum is used for the reduction of the magnesium fluoride.

23. A cyclic process for obtaining very pure magnesium according to claim 21, in which silicon in the state of an alloy of silicon, iron and aluminum containing about 50% of silicon, 15% of iron and 35% of aluminum is used for the reduction of the magnesium fluoride, in such a proportion that finally an alloy of iron and silicon containing 60% of iron and 40% of silicon is obtained.

CARLO ADAMOLI.

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