US1893023A - Metallurgical apparatus - Google Patents

Description

3m, 31933. .M G, pom/LEF@ 3,8939923 METALLURGI CAL APPARATUS Filed March 8, 1930 Patented Jan. 3, 1933 MORRIS G. FOWLER, OF CLABKDALE, ARIZONA, ASSIGNOR T COPPER COMPANY UNITED 'V'EQBDE METALLUnGIcAL rumana Application med laren 8,1930. serial No. 434,471.

This invention relates to metallurgy and has for an object the provision ofl improved basic lined metallurgmal'apparatus. More particularly, the invention contemplates the provision of an improved monolithic magnesite lining for metallurgical apparatus and an improved method of lining metallurgical apparatus. The invention further contemplates the provision of a copper converter prol0 vided with an improved monolithic magnesite lining. A further object of the invention is to provide improved material for forming monolithic linings.

Some metallurgical operations require the 5 use of apparatus provided with basic linings for carrying out the processes involved and, in such cases, it is customary to employ linings formed of magnesite. Considerable difficulty is involved in forming satisfactory 0 magnesite linings from commercially available products such, for example, as dead burned magnesite. This material doesnot bond readily except at high temperatures or when diluted with a binder which lowers its 5 softening temperature. High temperatures cause shrinkage of the magnesite, and the addition of suiicient binder to form a suitable bond frequently causes a reduction in refractoriness which makes the resulting product unsuitable.

Satisfactory linings'4 may be formed by applying the magnesite inthe form of bricks 'which have been heated to the bonding temperature of the magnesite during the course 5 of their manu-facture'. 'lihe preparation of such bricks is expensive, and, consequently, linings in which the bricks are employed are costly. g

Lining costs are requentlysuiiciently 1m- 3 portant that the type of process used in some metallurgical operations is governed thereby. Thus, in the case of copper converting, the cost of the linings in cases in which brick linings are used, determines the type of slag i which is employed. The use of a relatively high-silica slag results in injury to basic linings, and, consequently, relatively low-silica slags are generally used. v

While the use of a slag having al low silica content prolongs the lifeA of a converter lining, such slags also produce certain harmful effects.. Low-silica slags retain more copper than high-silica slags, the amount of copper carried by the slag being inversely proportional to the amount of silica contained therein. Considerable diiiiculty is experienced in handling low-silica slags in ladles and in introducing` such slags into retreatment furnaces. Retreatment of low-silica slags also involves some difiiculties. It is dicult to extract copper from such slags,and there is a tendency for magnetite contained therein to separate out and build accretions on the hearth of the retreatment furnace. It is therefore desirable to provide a lining at a suiciently low cost that high-silica slags may be used economically.

Various attempts have been made to reduce liningy costs by substituting monolithic linings for built-up linings of brick. Such lin- 'd'0 ingshave been formed by applying the magnesite in the form of a plastic mass of line and coarse particles to the surfaces to be covered and drying and burning the resulting lining.

In providing monolithic linings for the usual commercial purposes, it is impracticable to heatl the magnesite to temperatures suciently high to cause bonding of the particles because of the size and location of the monolith and because of the tendency of mag- B0 nesite to shrink when heated. Accordingly in providing monolithic magnesite linings it is customary to employ binders which lower the softening point of the magnesite or which themselves provide lmechanical bonds between the magnesite particles.

In forming monolithic linings, it is desir able to provide lining mixtures which may be tamped to provide dense structures which retain their forms until burned and which are suliciently refractory to withstand the temperatures to which they are subjected in service. @ense structures are necessary to provide the necessary mechanical strength and, in some cases, to prevent the penetration of fluids such as molten minerals which cause disintegration of the lining.

In forming monolithic magnesite linings in accordance with the heretofore customary practices, it is frequently necessary to employ an amount of binder or a type of binder which so reduces the refractormess of the resulting lining that it is unsatisfactory7 for the intended purpose in ordertovprovide a mass of lining material which is sufficiently plasticthat it may be readily moulded into the desired form. Considerable diiiiculty has been experienced in providing monolithic linings in .which sufliclently good contact is obtained between the adjacent particles to give satisfacto density and strength `while maintaining satisfactory refractory qualities. Frequently, segregation of the particles of different sizes or the less refractory particles of a linin mixture occurs during the installation of t e lining with the result that a lining of non-uniform density having weak spots is produced. l v

The present invention facilitates the production of monolithic linings having dense, strong structures. The invention further provides for the production of monolithic linings of relatively uniform density without the use of excessive amounts of relatively non-refractory binders.

The present invention is based upon my discovery that particles of commercial magnesite may be made more adaptable for the manufacture of monolithic linings if subected to the action of'an acid prior to being mcor rated in the lining structure. I have foun that improved plasticit ofa mixture of magnesite particles and a inder may be obtained by treating the mixture with an.

acid or by subjecting the ma nesite particles to the action'of an acid be ore the mixture is formed. I have also found that a more intimate contact of the particles may be obtained when magnesite is subjected to the action of an acid prior to being incorporated lin `the lining. .-In general2 a substantially neutral mixture of magneslte particles and a suitable binder may be used advantageously to form highly satisfactory monolithic linings. j

I attribute the increased plasticity to neutralization ofthe relatively strongly alkaline impurities contained in the commercial magnesite. The more intimate `contacts of the particles may be attributed to the increased plasticity of the lining mixture vwhich provides for better contact between the` articles by permitting more uniform disvsemlnation or distribution of the line particles throughout the mass, and, in some meas-v ure, to the fact that the acid etches the surp faces of the magnesite particles and permits better contact of the fine material with the coarse.

As a result of lthe increased plasticity which may be achieved by treating magnesite with acid, lining mixtures: vcontaining rela-l vtivelysmall amounts ofbinders ma he used treatment if the quantities of grains of different sizes which are present, in the lining;

material are carefully popor'tioned so that a dense structure may provided.

The magnesite may be treated with acid in any desired manner and at any appropriate time. The manner and time of treatment of the magnesite with acid will depend to some extent upon the natures of the acid and the magnesite. The acid may be of such a nature that the incorporation of an excess in the lining would produce harmful results, or a particular acid might react with pure magnesite or with impurities contained in commercial magnesite to produce one or more harmful reaction products. If the acid employed and the magnesite are of such lnatures that no re. action product which would produce harmful effects if incorporated in the lining is produced, the acid may be added directly to the lining mixture and no steps need be'taken to remove any excess or the reaction products. On the other hand, if the use of-any particular acid would result in the roduction of harmful reaction products, or 1f an excess ofthe acid would produce a harmful effect, it is advisable to first subject the magnesite to'the action of the acid and then remove any excess acid and/or the-harmful reaction products by washing, or otherwise, before incorporat- All or any desired part of thegrains to be incorporated in the lining may be subjected to the action of acid and the ma esite whichis los subjected to the action'of acid may be com pletely or only partially neutralized.

v Anydesired amount of acid may be employed. The. amount of acid employed will depend .upon the nature of the acid and the results desired. If complete or partial neu-- tralization of the impurities in the .magnesite only is desired, an amount of acid only suffi' cient to accomplish the'desired result should be employed. If etching of the grains is desired an amount 'of acid which is more than sufficient to neutralize the impurities in the lis magnesite being treated should'be employed.

In some in stancesit may be desirable to cause etching of the surfaces of the relatively coarse grains only, and, in such cases, the

coarse grains may be treated separately.

In some instances,rthe acid employed and the magnesite may be of such natures that one ormore reaction products which may be incorporated .advantageously in .the lining may be produced. vFor example, sulphuric acid may be employed as a means for neulas tralizing impurlties and/or etching'the sur- *13 nesium sulp faces of the articles and incorporating magate in the lining. Most commercial magnesite products contain lime, and a mixture of the magneslte with water and a binder such, for example, as lireclay may be strongly alkaline. This is due to the slight alkalinity of the pure magnesite and the strong alkalinity of the lime. When such a mixture is treated with sulphuric acid.

type of acid and the nature of will permit the acid may be added to the mixthe acid acts as a flocculent, increasing the' lasticity of the ireclay and rmitting the use of less fireclay for bon ing purposes. The amount of acid employedcan be varied widely, as even a large excess will be completely neutralized by the magnesite to form magnesium sulphate. The use of excessive quantities of sulphuric acid is not advisable because such a practice would result in the incorporation of excessive quantities of relatively non-refractory magnesium sulphate in the lining.

Some of theI important effects of sulphuric acid when used in the proper proportions are` as follows (l) lt increases the plasticity of a binder, such as fireclay, by neutralizing the alkaline substances in the magnesite. l

(2) -It etches the surfaces of the articles and provides better Contact of the ne material with the coarse, thus increasing the bonding eiect of whatever additional bond is usedwith a consequent increase in mechanical strength. (3) It forms hydrated magnesium sulphate which takes a very strong cold set. The magnesium sulphate may be very widely disseminated throughout the lining mixture.

The incorporation of magnesium sulphate in linings is sometimes desirable because of its property which will cause a. lining in which it is incorporated to take a strong cold set. It loses someof its bonding strength at dehydration temperature, but still bonds magnesite fairly well up to a temperature of about 1500 F. It is particularly valuable as a bond when used with another bond such as fireclay which does not take a strong cold set and bonds with magnesite only at temperatures of from 2000o F. to 2200 F.

According to the present invention, granulated magnesite may be mixed with a suitable bindervvin the wet state and rammed or tamped into place between the receptacle or furnace wall and a suitable form to provide a wall of proper thickness. The magnesite may be treated with acid prior to its incorporation in thevlining mixture, or, when the the magnesite ture during the mixing operation. When the ylining material has been rammed or tamped into place, the form is removed and the wet lining is subjected to heat at'a low temperature for a suiiiciently long period to drive off the major portion of the water contained The most satisfactory therein. The lining is subsequently heated until it reaches a temperature approximating that to which it will be subjected in service or a temperature which is high enough that the charging of a bath or other charge of normal temperature will not cause material damage. It is unnecessary to bring the entire lining up to the maximum tempera ture. Good results can be obtained if only that portion of the lining immediately adjacent the inner surface is thus heated. l

In order that the best results may be obtained 'in forming the refractory lining material of the invention, it is important that the -particle sizes be carefully proportioned. material comprises a mixture of relatively line particles and relativel coarse particles. The coarse particles shou d form the major portion of the mixture. The fine particles should be sufiiciently which the lining is to be used. The relative Aamounts of fine and coarse material to be used in each case will depend upon the characterand sizes of the coarse grains. Suilicient ine material to fill the voids between the coarse desirable, though not necessary, to provide just suflicient line material to fill the voids and permit at least one point of contact of each coarse particle' with every adjacent coarse article.

The y ne material may consist substantially entirely of particles ranging from substantially colloidal particles to 1GO-mesh, and the coarse material may consist substantially entirely of particles to one-half inch or larger. In general, it is advisable to use mixtures of which twelve to twenty-two per. cent of the particles are sutliciently small to pass a 100-mesh screen.

A large proportion of the remaining parti- 20-mesh and 10U-mesh in size should be minimized. In fact, it is desirable to eliminate such sized particles. While any suitable mixture of grain sizes may be used, the best results may be obtained when n0 intermediate sizes are used and when twelve to twentytwo per cent'of the particles pass a 100- mesh screen and the remaining particles are too large to pass a .20-mesh screen. Material in whichV ten to fifteen per cent of the particles are too large to pass a B-mesh screen is very satisfactory. It is desirable to provide material in which the coarse particles are uniformly graded between 20-mesh and one-half inch.

- Particle sizes' have been given in terms particles should be used. It is ranging from 20-mesh iso ofthe Tyler series. Percentages by weig'lltA eA portion of the line material required ,for the are given 'throughout the cification.

term magnesite is used t roughout in the accepted sense, that is, to denote the' commercial calc-.ined products commonly used' for refractory urposes.- A v The mixtures'of particles-of diiferentl sizes may be formed Iin any desired manner.

. number of different' sizes may be` se arately formed and classified and subsequent y mixed f in the proper proportions, or crushing and isf substantially impossible to any mixture of particles of dierent sizesl grindingmay be so eonductedthat very coarse material may be reduced to provide. a mixture containing approximately the correct sizes and proportions in a single operation.y The composition ofthe resulting mixture may be corrected by additions of separately classified particles of the proper sizes. Satisfactory coarse and fine products initial materials to types of treatment designed to produce particleshaving maximum sizes corresponding to the maximum sizes de-l `sizes aswell as a variety of intermediate sizes. If the resulting products are not satisfactory separate additions and/or removal of' parlicles of particular sizes may be made.4

. l Owing to the fact that in crushing or grinding refractory materials an infinite variety ofparticle shapes may be produced., it predict that will result inthe p oduction of a. lining which is perfect wit respect to density. Mixtures of particles within the size limits hereinbefore set forth produce satisfactory linings, and the most satisfactory mixture for 'any particular material or for any particular purpose may be determined readily by means of a few simple tests. For example, small Fim amounts of several different mixtures may be formed into bricks which maybe subjected toconditions similar vto those to which the lining will be subjected, and 'a compari- ,so son of the effects on the different bricks will indicate the mixture which is the Vmore suitable. v f

AnyA suitable magnesite product may be used in forming linings in accordance with used advantageously. -1 Two commercial forms of magnesite, dead burned magnesit prise a'plastic mass-offinely divided solid i5-particles. When a bindercompris'ing solid may be obtained by subjecting the raw or.

the invention. California magnesite may Israelis-'vA lining mixture.

The binder should be selected avoid the incorporation of large amounts of uxing materials 1n the lining. The following binders have been found to be satisfactory amounts by weight noted l Per cent Fireclay 2- 5 Bauxite v 2- 10 A mixture containing bauxite 3 parts f and fireclay 2 parts 2- I10 Molasses 0.5-5.0 Sulphuric acid 0.1-0.5

.when used with granular magnesite in the The lining mixture should contain suii'icient i i Example! Ingredients: l Per cent Maltby magnesit- 91.5 Fireclay 4.0

vVlfater 4.0 Sulphuric acid 0.5

Screen sizes: l

+100 mesh 87.2

-100 mesh 12.8

Analyses o'f materials sic, 2.1.0. nso. cao Mgo Maltby stagnante.V Kasa 0.69 1.72 2.4 81.6 my 66.94 21.3 3.58 es 1.2

Sulphuric acid-specific gravity 1.8.4

Eample II Ingredients: Y Per cem Periclase 96.7 MolassesA 2.0 Water 1.0 Su1phuricacid 0.3 n Screen sizes:

+100 mesh 85.7 -100 mesh 14.3

Analysis of materials.

sio, Aho. Fao. ycao Mge,

Pericles- 2.a 0.a 2.42 2.a; om

I ii

Sulphuric vacid--specific gravity 1.84y

100 mesh -i 16.6

walls l and a sheet metal bottom Wall 11.

1,598,028 5 Enya/mph III Analyses ofmaterlals In edients: l Per een:

5101 A1208 F6108 CBO M80 Crude bauxlte T 4.3 giallcined baum@ ifmfi: @13 2&3 it? 8:?3 83:5 o asses Suumcac1d"""f "v l Sulphuric acid-specific gravity 1.84 VScreen size: I Ewmze VU 10 +100 mesh 88 In edlellts: Per cent ...100 mesh 12 lorra magneslte 86.2 Fireclay 5.3 l Analyse@ anmutende gallcwd bali 5 3 l v u p uric aci 0.1 w sfo: Ano. reno oso Meo S Water y 3 1 creen size:

Sltfa: iti 5313i it i? +100 mesh 84x; Maltbyte 6.34 1.84 7.7 100 mesh- 15.3 20 Sulphuric acid-specific gravity 1.84 l Analyses of material@ ln edients' Emple IV Per cent sm Aho' Feo C80 Mgo ierra ma esite 86.0 Firecny gli 1.7 ifia'fsfI: i z 2:33 lit all 2Q bauxite 2 8 Calcindbuxi 16-0 60.5 10.64 .40 6.0 AgtiLTIIIIII::ijijiji: i3 S11ph11-1= 1111-1111111@ s111111 1.81 Sulphuric acid -4- 01 In utilizing. sulphuric acid in the produc- Screen size: tion of monollthic linings, it is advisable to 30 +100 mesh v- .i 78.0 employ more than enough to neutralize the 100 mesh 22.0 strongly alkaline impurities in the magnesite Analysea of maten-als in order to etch the surfaces of the magnesite particles and providesuicient magnesium sion l Aho, I Fao. I cao Mgo sulphate to permit the lining to take a good 35; cold set. The resulting lining mixtures will sia-m magnesi take at 6 l 7. 9 1 2 5 '82 1 be neutral except for the slight alkalinity due niiixigi''i' 4' to magnesite. When magnesite, a solid bind- Cgelkx-i--e-E- 624` 18' 70 L. 1-6 er and an excess of sulphuric acid are emmud mm 11. 0 12. 5 11. 2 0. 9 1.1 ployed the resulting lining material will con- A0' C'g 13.6 55.0 5.x '0. 5 o o sistessentially of magnesite, solid binder and magnesium sulphate. Sulphuric 'acid-specific gravity 1.84 Magnesite linings formed in accordance Emaqple V with the method of the present invention are In edients, Pe'r een, particularly suitable for use in molten bath .45. dase' 94.7 receptacles such as copper converters, and Gallup gyf: 3 0 when so used give satisfactory service at a Water 2 0 lower cost than brick linings'or` similar mate- Sulphuric acid 0,3 rals. A number of magnesite linings which 50 Analyses of materials served satisfactorily in copper converters showed matte and slag penetration varying Sio. A120. Fao. cao AMao from about one-half inch. to about one and f 'three-quarters inches. Pei-lense a2 0.6, 2.40 0.7 92.3 Linings of the invention have been success- `55 Fksclaymffw 67's 210 M8 0'6 2'6 fully used in copper converters, twelve feet Sulphuric acid-specific gravityll m diameter of the. typ? luusmted m the ac' Eampze VI companymg drawing, 1n which yn edjent's: l Per cent Fig. 1 is a sectional side elevation of a. wellieu-a magnesite 90 0 known type of copper converter provided 60 Gallup fil-@Clay 5 5 with a monolithic lining; and

Sulphuric a.cid f 0 1 Fig. 2 is a section taken substantially along Water 4,4 line 2-2 of Fig. 1. Screen size: The converter comprises a substantially cy- +100 mesh 83.4 lindrical receptacle having sheet metal side 65 The side walls -and bottom of the receptacle are provided with a moLiiolithic' linin 12.

pipe 13 extends through the slde wall 10 and the lining 12 and provides means of communication between the interior of the receptacle and a source of supply ofair under pressure(not shown). -A layer'or lining '17 of bricks is disposed between the sheet metal side wall 1()v and the monolithic lining and ex forms having substantially vertical walls are placed within the receptacle with their vertical walls spaced the proper distances from the vertical side walls of the receptacle. The lining mixture is then placed between the form and the side walls in successive horizontal layers of suitable thickness. Each layer is thoroughly tamped and packed before the next succeeding layer is added. yThe best results have been obtained when the material has been inserted in layers varying from three Ato seven inches in thickness. Layers of greater thickness are difficult to'tamp properly and their use might result in segregation of the coarse particles. The bricks 17 are placed-in position in layers periodically as the lining mixture is inserted. The `tuyre pipes are inserted when the lining has been built to the proper height. The lining mixture is tamped and acked around the sides and above the tuyre pipes. During the tamping, bars or heavypipes maybe inserted within the tuyre pipes to prevent distortion. The force used in tamping need only be sufficienty to insure thorough packing and the production of a dense mass.

The cap is separately lined while inverted. The cap may be lined with the lining mixture of the invent-ion or any other suitable refractory. The caps are not subjected to excessive wear and the cost of their linings'is not of great importance. The joint between the cap lining and the shell lining when the cap is attached may be plastered with the lining mixture of the invention Aor any suitablel plastic mass of refractorty material.

When the lining has been completed a slow wood ire is started. in the receptacle and heating is conducted in this manner until the lining has been well dried. This requires from about eight toforty-eight hours` depending probably upon the heat generated, the thickness of the lining, and the amount of mois- -ture in the lining. When the lining-has been dried satisfactorily in this manner, it is heated by means of a hot oil fire for a suiciently A long period to raise the tem rature of the inner surface ortion thereo to about 2000 F. y This heating may be continued over a period of from elght hours to several days.

The converter should be put in service before any considerable drop in the temperature of the liningtakes place. The usual procedure with respect to copper' converters' may be followed in putting the converter into service. A coating of maetite may be providedl or not as desired. etter service will be obtained if copper is not made within forty-eight hours after the converter is put into operation.

The monolithic linings .of the present inu.

vention are not only satisfactory in service when new, but they may also be quickly and cheaply repaired when portions' thereof are damaged. In patching a damaged monolithic lining it is only necessary to cut away aA sufficient amount of the old lining to provide a rough surface for bonding purposes and apply a suitable amount of the lining mixture to uild the damaged portion to the required thickness.

- ,It is advisable to dry and burn patches in the same manner as new linings prlor to put-l ting the receptacles back in service.

Linings formed in accordance with the present invention are considerably. cheaper than linings formed from refractory bricks according to the heretofore customar practices. Granular material can be o tained v more cheaply than bricks at any desired location. lThe linings of the invention can be installed at a lower cost than brick linings.

The installation of brick linings requires y highly skilledv labor while the installation of y the linings of the invention may be made by` relatively cheap common labor.

The relatively -lower cost of monolithicA magnesite linings ofthe invention permits the use of a moresiliceous slag 1n copper converters even though the siliceous slag attacks the lining. The use of a siliceous slag is not only advantageous because of the lesser' amount of copper carried thereby, but it is more advantageous because a relatively highsilica slag is easier to handle in ladles, easier to introduce into retreatment furnaces, and retreatment is more complete notonly withrespect to the copper extracted but also with respect to minimizing the segregation of the more or lessinfusible and refractory magnet- 1. A molten bath receptacle having amonolithic refractory lining in which about twelve ite which, in the case of less siliceous conto twenty-two per cent of the bonded particles are small enough to pass a 1D0-mesh screen,

all

and the major portion of the remaining particles are too large to pass a 20-mesh screen.

2. A molten bath receptacle having a monolithic refractory lining 1n which about twelve to twenty-two per cent of the bonded articles are small enough to pass a 1GO-mes screen, and the major. portion of the remaining particles are too large to pass a QO-mesh screen and small enough to pass a one-half inch screen.

3. In a method of lining metallurgical apparatus involving the application of a wet mass comprising granular magnesite and a binder to the walls of the apparatus, the improvement which comprises subjecting the mass to the action of a mineral acid to neutralize alkaline impurities contained therein and thereby improve the plasticity of the mass.

4. In a method of lining metallurgical apparatus involving the application of a`wet mass comprising granular magnesite and a binder to the walls of the apparatus, the improvement which comprises subjecting the mass to the action of an acid to improve the plasticity of the mass and thereby provide. for better contact between the articles b permitting more uniform distri ution of t e fine particles throu hout the mass, the amount of acid employed eing not substantially in excess of that required to neutralize alkaline impurities contained in the mass.

5. In a met-hod of lining metallugical apparatus involving the application of a linin mixture comprislng granular magnesite and a binder to the Walls of the apparatus, the improvement which comprises improving the plasticity of the mixture by the addition of an amount of sulphuric acid equal to not more than about 0.5% of the weight of the mixture.

6. In a method of lining metallurgical ap? paratus involving the application of a wet mass comprising granular magnesite and fireclay to the walls of the apparatus, the improvement which comprises subjecting the mass to the action of an acid to improve the plasticity of the mass and thereby rovide for better contact between the particles by permitting more uniform distribution of the fine particles throughout the mass, the amount of acid employed being not substantially in excess of that required to neutralize alkaline impurities contained in the mass. a

7.' In a method of lining metallurgical apparatus involving the application of a wet mass comprisingv granular magnesite and bauxite to the walls of the apparatus, the improvement which comprises subjecting the mass to the action of an acid to improve the plasticity of the mass and 'thereby provide for better contact between the particles by permitting more uniform distribution of the fine particles throughout the mass, the amount of acid em loyed bein not substantially in excess oft at require to neutralize alkaline impurities contained in the mass.

8. In a method of lining metallurgical apparatus involving the application of a wet mass comprising granular magnesite and molasses to the walls of the apparatus, the improvement which comprises subjecting the mass to the action of an acid to improve the plasticity of the mass and thereby provide for better contact between the particles by permitting moire uniform distribution of the ne particles throughout the mass, the amount of acid employed being not substantially in excess of that required to neutralize alkaline impurities contained in the mass.

9. In a method of lining metallurgical apparatus involving the application of a Wet mass comprisingl granular magnesite and a binder to the`walls of the apparatus, the improvement which comprises subjecting the mass to the action of sulphuric acid 4to improve the plasticity of the mass and thereby provide for better Contact between the particles by permitting more uniform distribution of the fine particles throughout the mass, the amount of acid employed being not substantially in excess of that required to neutralize alkaline impurities contained in the mass.

In testimony whereof I at'x m si ature. Mouais G. Fbvvnnn.

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