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pally of a combustion chamber so designed as to permit nearly theoretical admixture of air and fuel; a washer or scrubber where the products of combustion are cleaned and cooled to about atmospheric temperature; a drier for removing the water that may come over mechanically with the gas; a compressor or blower equipment for raising the pressure to an amount that the hydrostatic head in the recarbonation chambers will be overcome; and lastly, recarbonation basins provided with gas diffusers for uniformly dif-
Vol. 19, No. 7
fusing the gas into the water. We are concerned with the number of pounds of carbon dioxide absorbed by the water, and therefore accessory to the carbon dioxide plant must be gages, instruments, and other devices which will enable the operator to know just what he is doing. The proposition is largely volumetric, and in larger plants, a t least, recording gages registering the total amount of carbon dioxide that has been delivered to the water over any period of time should be provided.
Vanadium' By J. W. Marden and M. N. Rich RESEARCH LABORATORY, WESTINGHOUSE LAMPCo., BLOOMFIELD, h-.J.
Previous Attempts to Prepare Vanadium
During the present investigation these electrolytic methods for the preparation of vanadium have been tried. It was ERZELIUS1.* attempted to produce vanadium by found that electrolytic deposits containing some vanadium heating the oxychloride in an atmosphere of ammonia. might be obtained if iron were present in the bath, but no According to Roscoe,2 Berzelius obtained, not metallic pure vanadium metal was deposited in this way. vanadium, but vanadium nitride. Roscoe claims to have Although other authors, such as Matignon and Monnetl1I been the first to produce nearly pure vanadium powder by and Hittorf,12 attempted the production of vanadium, Weiss the reduction of the dichloride in very pure hydrogen. His and Aichel'3 claim to have been more successful by their process was very difficult and time-consuming. The di- reduction of vanadium pentoxide with misch metalI4 by the chloride was first specially prepared and finally reduced well-known Goldschmidt process. They obtained 10 grams with hydrogen under very exacting conditions. The process of a silvery white metal with a hardness of 7 , which according lasted from 40 to 80 hours and yielded only from 1 to 4 grams. to them belongs to the arsenic-antimony-bismuth group of Nilsson and P e t e r ~ s o n ,Setterberg,4 ~ Safarik, Moissan, metals. and Helouis' have all atKoppel and Kaufmann15 tempted by various means also investigated the Goldto prepare vanadium metal, Schmidt process, and atVanadium metal has been prepared. Contrary to but, as has been shown by tempted to reduce vanaprevious statements in the literature, this metal is not later authors, their efforts dium pentoxide according like arsenic or bismuth. It is not brittle but may be have not been very successto the equation: cold-worked into wire or other forms. Chemical ful. Moissan, for example, 3%06 10A1 = analyses have been made of the vanadium samples and 6V 5A1203 in his electric furnace oba number of physical properties, such as specific tained vanadium containThe analyses of their prodgravity, electrical conductivity, etc., have been detering a large amount of caructs'showed about 79 per mined. In properties vanadium resembles tantalum. bon or, when he attempted cent vanadium, 2 per cent the reduction with alumiiron, and a considerable amount of silica, insolunum, prepared an impure alloy of vanadium and aluminum. Helouis, using the alu- bles, and oxygen by difference. When using carbon and calcium carbide as reducing agents, they obtained about 88 minum reduction, obtained a lower oxide. Goldschmidt8 showed that vanadium pentoxide could be per cent vanadium, 7 per cent carbon, and 5 per cent oxypartially reduced by the well-known alumino-thermic process, gen. This indicates clearly that the aluminum reduction but difficulty was experienced with this method on account method as proposed by Goldschmidt is unsuitable for the production of pure metal. of contamination with lower oxides, aluminum alloys, etc. Von Bolton16 used a distinctly original method. He made Cowper-Coless claims to have succeeded in producing vanadium by electrolysis. The electrolyte consisted of 1.75 a plastic mass of vanadium pentoxide and paraffin and carparts of vanadium pentoxide dissolved in 2 parts of sodium bonized it. During this process the pentoxide was reduced hydroxide and 160 parts of water, to which 32 parts of hy- to trioxide, which was then directly heated by passage of drochloric acid were afterwards added. The electrolysis the electric current in vacuo. He claimed that it was possible was carried on at 180' F., using a current density of 18 to to separate vanadium oxide into its components by thermal 20 amperes per square foot of cathode surface, the e. rn.f. a t dissociation. His samples thus prepared showed a melting the cell terminals being 1.88 volts. Gin10 claims to have im- point of 1680"C. Von Bolton did not investigate the properproved upon Cowper-Coles' method by using a fluoride bath. ties of his vanadium, as he was then interested only in proThe following equation illustrates the chemical reactions ducing material suitable as a filament in incandescent electric which take place when vanadium trioxide is electrolyzed in lamps-that is, a metal from which a filament could be made which had a melting point above 2000' C. the presence of carbon in molten fluoride: Ruff and Martin" made an extensive investigation of the 6F v103 3C = 2VF3 3CO preparation of vanadium by a process similar to that of Von VFa = V 3F Bolton. When vanadium carbide and vanadium oxide were 1 Received March 4, 1927. Presented before the Division of Industrial mixed, compressed into a rod, and the current passed directly and Engineering Chemistry a t the 73rd Meeting of the American chemical through the rod, vanadium wax prepared which contained Society, Richmond, Va.,April 11 to 16,1927. some oxide or some carbide, depending upon the composition * Numbers in text refer to bibliography at end of article.
B
+
+
+
+
+
+
of tlie mixture. 111 orrlca to gct tlie melting point of 100 IJIT cent vanadium, they deterniiiied the melting points of it serics of samples Iinving 2 to 20 pcr cent carlron and 2 to 20 or 30 per cent oxygen. Tlio rrielting point of vanadiiim d by the presence o? eitlier carbon or oxygen. The age of itnpurit,y uas plotted against the melting points and tlie curves uere extrapolated to zero per cent impurity to find tlie nicltiug point of carbon-frcc, oxygen-free metal. This tiicy found to he 1715" C. The specific gravity was fourid by these authors in the same way by plotting t,he specific gravities of impure samples having known composition and extrapolating the values to 100 per cent purity. These experiments of Ruff and Martin show that it is practically impossible to get vanadiuni free o? both carbon and oxygen. Apparently, vanadium containing oxide cannot be heat.ed in vacw witti the complete elimination of oxygen by thermal dissociation. I'randtl and Manz" describe a series of attempts to prepare pure vanadium by the alumino-thermic process. Their experiments, however, were no more successfnl than those of previous investigators, Edson and McIntosh'* describe a laboratory method said to deposit vanadium from vanadium oxychloride vapor on a heated filament of platinum in MCUO. The method of deposition is the sanie as is wcll known for the deposition of carbon from tetrnchloride vapors where the vapor compound is decomposed by heat alone. The deposits have a smooth, silvery gray appearance, but no analysis of this material is given. Hunter and Jonesza have recently attempted to reduce vanadium chloride with sodium in a closed iron bomb. They claim to have obtnined 95 per cent vanadium metal in the form of a fine powder, but they failed to get any large heads of nretal, which would indicate insufficient heat in the reaction for a t least partial insion. Ductility of Vanadium .s and AicI~el'~ consider that vanadiiirrr hlorigs to thc arseiiie-i~iitiiiiony-iiismnth group of rnet:ils. If this is true, the cleinciit vanadium should not. be c:ipable of
Specimen 721-D.
Structure in rhondium m e l d b e d . concd. "01. 1000 X
It seems interesting blut so niiicli wxk could have been done on this elmiient without any author finding indication of such ductility. Von Bolton states that lie discontinued his wiirk on vanadium after bcat-treating a pressed rod of the lower oxide and carbon. The very extensive work of Iluff and Martin does not ment~iou experiments om the working of vanadium metal. Perhaps tile difiiculty can he traced to the fact that metal innde by Vom Bolton's proccss always contained some oxide or carbide, or to the fact that vanadium, like taiitalinir, is estrenrcly scnsitive to the presence of hydrogen. When soft, niaiieable vanadium is heated in {.lieprcscnce of hydrogen it immediately becomes very brittle aod cannot be worked again without fusion in vacuo to reniove the hydrogen. It is wcll known that, when a tantalum wire is flashed in liydrogen it becomes extremely fragile and cannot be drawn or further rolled. According to Hull*' x-ray crystal analysis shows that vanadium belongs to the center body cubic system as dues tantalmi, which would indicate that this metal should be capable of cold-working. Preparation
Several methods were tried for the production of vanadium, but the simplest proved to hc the calcium-calcium chloride proccss developcd for the production of thorium powder.la The rednction is carried out in a bomb similar to that described in the previous paper and tlie reaction may he represented by thefoilowiug cquatiun: v2013- 5Ca + 5CVC1, = 217 + SCaO.CaCI* For a small charge 175 grams of vanadium pentoxide, 300 grimis of finely milled calcium, and 300 grams of calcium cliloridc arc used. A small piece of potassium or sodium is placed on top of t.hc charge. The function of the potassium or sodium is to clean up the residual air sealed in the bomb before the reduction reaction takes place in which the vanadium is formed. The potassinm or sodium also apparently clcans up any moisture that may he present, thus taking care of any hydrogen which even in small quantities has such a niarkcd embrittling effect upon vanadium. The bomb is
Specimen 721-E.
Etched in
100 X
Microsfrmctwe of Vanadlum
being cold-worked, should have a brittle fractiire, and should be hard. If, on the other hand, vanadium belongs to the group of elements containing tantalum, it should, like tantalum, he comparatively soft, ductile, and capable of being cold-worked into wire, sheet., etc.
then closed and sealed and placed in a wirc-wound resistance furnace and heated to 900-950" C. for one hour, after which it is allowed to cool to room tcmperatnre before opening. The charge is usually removed by ohopping with cold chisels, and as removed from the bomb it is fed a little at a
I-VDUSTRIAL A N D ESGINEERING CHEMISTRY
788
time into a large jar of vigorously stirred cold-distilled or filtered water. It is essential to keep the water cold and also to have vigorous stirring in order to prevent the vanadium from becoming heated during the disintegration of the charge. About 20 liters of water is a suitable volume for a charge of the size mentioned above. When the charge has been removed from the bomb and entirely disintegrated, the stirring is stopped and the residue allowed to settle in the jar. This settling usually requires not more than 2 minutes. The residue is washed about four times with water. Contrasted with thorium, vanadium is soluble in nitric acid but insoluble in dilute hydrochloric acid, while thorium is insoluble in nitric acid but quite soluble in hydrochloric. The vanadium is washed three or four times with 1:8 hydrochloric acid solution, the solution being diluted after each washing and decanted away. The dilute acid dissolves away the lime, leaving the vanadium in the form of beads, varying in size from that of n steel pinhead to rather large beads of 6 to 9 mm. ( l / 4 to 3/g inch) in diameter. These beads are finally filtered, washed with water, alcohol and ether, and dried by placing in a bottle and evacuating at room temperature. The beads are very bright, of a steel-white color, and are soft enough to be hammered. The easiest way to work the vanadium into wire in the laboratory is to place the beads in iron tubes and roll cold until the beads have become sufficiently elongated and squared off for handling. The iron is then removed and the rolling continued to any desired diameter. Annealing under osidieing conditions is beneficial, since vanadium, like other metals, has a tendency to become hard on cold-working. If larger samples are desired the beads may be melted in zacuo by means of the high-frequency induction furnace, or by almost any means where the presence of hydrogen, carbon, or deleterious impurities is entirely avoided. The accompanying photomicrographs of samples of vanadium prepared as described above show the general appearance of the metal. The dark lines shown within the grains do not resemble oxide, but are apparently potential crystalline cleavage planes within the grains and have the same appearance as the grain boundaries. Chemical Analyses Total Vanadium Total vanadium was determined by titration with 0.1 N potassium permanganate solution standardized against Bureau of Standards sodium oxalate. The vanadium was dissolved in nitric .acid and the nitric acid removed by heating with sulfuric acid. The aliquot was reduced with sulfur dioxide and the excess sulfur dioxide boiled off under carbon dioxide. WEIGHTOF SAMPLE (0.1 aliquot) Cram _ .
0.10865 0.10865 0.10865
0.1 N KMnOI SOLN. CC 21.32 21.38 21.17
WEIGHT
OF
FOUND Gram 0,1087 0,1090 0.1079
V
PURITY
Per cent 100.0 100.3 99.4 Av. 99.8
Total vanadium was also determined by direct oxidation. The sample was dissolved slowly in nitric acid in a weighed porcelain dish, evaporated to dryness, and ignited. ORIGINAL WEIGHT Grams 1.0565 1.0183
WEIGHTAFTER OXIDATION Grams 1,8793 1.8111
INCREASE IN WEIGHT PCRITY Gram Per cenl 0.8228 99.30 0.7928 99.28 Av. 99.29
Impurities in Vanadium WEIGHTOF SAMPLEWEIGHTOF SiOr Gram Grams 1,2508 0.0016 1.0238 0.0011
CALCD. AS Si Per cent 0.06 0.05
Iron and other metallic impurities were separated by sodium hydroxide solution. This precipitate contained uranium and some manganese. When ignited the residue was black and was shown t o be less than half iron.
VOl. 19, No. 7
WEIGHT O F S ~ M P L F WEIGHT OF OXIDE Grams Gram 1.2508 0.0036 1.0238 0.0036
METALSCALCD.
AS
Fe
Per cent 0.20 0.24
Attempts were made to determine chromium, phosphorus, and carbon, but no determinable quantities were found. Physical Properties I n general vanadium wire and tantalum wire are very similar in their cold-working properties, particularly in the effect of hydrogen. Several of the physical properties of vanadium have been determined and are given below. It is interesting to note that, as would be expected, cold-working increases the density of vanadium, so that the values determined in this work are higher than those given heretofore. The specific resistance of vanadium is relatively high, but that is also to be expected. The specific heat was also determined, since the value given by Mache**appeared to be too low to give the constant of 6.4 by the law of Dulong and Petit. Density Moissan Hunter and Jones Ruff and Martin Author (cold-worked wire)
5.8 5.53 5.68 6.0
at 20°C. a t 20" C. a t 18.7' C. at22'C.
Maximum possible density calculated by x-ray data from the powder is 6.0.
Specafic Resistance (cold-worked) at 20' C. 26 X 10-6 ohm per cc.
Author
The specific resistance of tantalum is given a s 14 X 10-8, of columbium is given a s 18 X lo-@,and vanadium should in all probability have some value above that of columbium.
Temperature Coe@cientof Resistance 20' to 150' C., a = 0.0028 in formula R = Ro (1
+ at)
Specijc Heat Mache Author
0.1153 0.120
00 to 1000 200 to 1000
c. c.
Meltine Point Yon Bolton Ruff and Martin Author (approx.)
1680' C. 1715' C. 1700' C.
Volatility Vanadium is one of the least volatile metals at its melting point. A sample may be held in the molten condition in high vacuum for a considerable length of time without appreciable blackening of a glass container.
h number of other metals have been prepared in a similar way and some of their physical properties determined. It is hoped to publish these in the near future. Bibliography 1-Berzelius, Pogg. A n n . , 22, 1 (1831). 2-Roscoe, Trans. Roy. SOC.London, 169, 689 (1869). 3-iiilsson and Petersson, A n n . Physik (Wied.), 4, 554 (1879). 4-Setterberg, Oefers K . Akad. Forhandl., 39, 13 (1882). 5-Safarik, Sitzb. Akad. Wiss. Wien, 33, 5 (1858). 6-Moissan, Compt. rend., 116, 1225 (1893); 199, 1297 (1896). 7-Helouis, Bull. soc. encour. i n d . nall., 1896, 446, 906. 8--Goldschmidt, Z . Eleklrochem., 4, 494 (1898). 9-Cowper-Coles, Chem. News, 79, 147 (1899). 10-Gin, Z . Eleklrochem., 9, 831 (1903). 11-Matignon and Monnet, Compt. rend., 134, 543 (1902). 12--Hittorf, Physik. Z., 4, 196 (1902). 13-Weiss and Aichel, A n n . , 337, 380 (1904). Chem.-Zlg., 28, 506 (1904). l4-Muthman, 15-Koppel and Kaufmann, Z . anorg. Chem., 41,352 (1905). 16-Von Bolton, Z . Eleklrochem., 11, 45 (1905). 17-Ruff and Martin, Z . angezu. Chem., 2S, 39 (1912). 18-Prandtl and Manz, Z . anorg. Chem., 79,209 (1913). 19-Edson and McIntosh, Trans, Roy. Soc. Can., 9, No. 3 , 8 1 (1915). 20-Hunter and Jones, Trans. Eleclrochem. Sac., 44, 23 (1923). 21-Hull, Phys. Rev., 20, 113 (1922). ZP-Mache, Ber. ( W i e n ) ,106, (Sa), 590 (1897). 23-Afarden and Rentschler, Ind. Eng. Chem., 19, 97 (1927).
