ANALYTICAL CHEMISTRY
484 relatively large amounts of phosgene with little trichloroacetylchloride, the predominant inorganic product being the white niobium oxychloride. I n this reaction carbonization was extensive. Carbon in small amounts is a normal by-product of the chlorination reaction. It seems, therefore, that before any complete mechanism can be written for this reaction a step by step investigation of the kinetics in the case of several different oxides must be effected.
CONCLUSIONS
It now seems evident that with such a reagent as octachloropropane the requisite conditions for a method of attack on the problem of quantitatively analyzing ores of the earth oxide minerals may be anticipated. With the chlorination methods described above a direct attack on the problem of the chlorination and distillation of titanium from niobium and tantalum becomes the neut step in developing this system of analysis.
( A n a l y t i c a l Chemistry o f N i o b i u m a n d Tantalum)
CHLORINATION OF TITANIA AND DISTILLATION SEPARATION FROM HAS been demonstrated that the pentoxides of niobium and I Ttantalum can be chlorinated a t atmospheric pressure using octa-
chloropropane. This reagent and technique have noK been applied to synthetic mistures of these oxides, to which titania and other geochemically associated oxides have also been added. The principal effort has been directed toward finding the conditions under which the titania could be quantitatively chlorinated. Once converted to the low boiling tetrachloride, it iyas planned to distill the titanium a m y from the other higher boiling chlorides as had been done by Ruff and Thomas (31,3&) and by Schiifer and Pietruck (33). A practical quantitative separation of the titanium n-odd greatly simplify the subsequent separation of the niobium and tantalum as well as increase the precision of determination of these elements, regardless of the choice made among the tannin technique ( 5 5 ) ,t'he pyrogallol reaction of Platonov ( 2 6 , 2 7 ) and others ( I d ) , and the indirect methods ( 3 3 ) . Therefore, these studies were concerned as much nith the distillation technique as with the chlorination itself. By a systemat,icvariation of the composition of the oside mixtures, the effect of each oside on the total process was evaluated. APPARATUS, REAGENTS, AKD IKCIDEKTAL ANALYTICAL METHODS
The atmospheric chlorination apparatus was much the same as that employed in the previous investigation except for modifications a t the top which permitted different kinds of take-off. The apparatus consisted of a reactor still pot, a reflux column, and one of the three column heads shown in Figure 1. A was used for straight take-off, B tyas an air-cooled head which permitted total refluu, total take-off, or any desired reflux ratio, and L' was a water-cooled still head which functioned like B except that the total internal surface was very drastically reduced. Conditions of operation of the reactor, column, and take-off in the final procedure were anhydrous to avoid hydrolysis or the formation of hydrates of titanium tetrachloride with attending loss of volatility. The apparatus was dried by heating under moderate vacuum. Thoee parts not heated by the Kchrome resiatance? were lightly flamed. After this treatment, dry air was slov ly admitted to the apparatus through the drying tube attached to the still head. The oxides were always freshly ignited and were placed along with the chlorinating agent in the cooled reactor still pot after the system had been treated as above. The reactor still pot was disconnected momentarily while the reagents v-ere inserted, and then quickly replaced. The system was once more evacuated; meanwhile only the column and the still head were kept hot. The reactor had to be left cold to avoid volatilization of the oetachloropropane. The apparatus was again filled with dry air, after which the reaction was initiated by heating the reactor still pot. This drying technique did not always yield a completely dry system. It is probable that there were always small amounts of water present which did not interfere because they were destroyed during the course of the reaction. When there was more than this minimal amount of water, a white precipitate of titanium tetrachloride monohydrate formed in the moist parts of the
apliai atus. The presence and amount of thia pi ecipitate sewed as a rough CI iterion of the dryness of the apparatus. A large number of titanium determinations were made on the distillates, on the column holdups, and on the reactor-still-pot residues. In general, these determinations were made by transferring the titania arid any other oxides involved to small beakers by Iyashing with water. The last traces of the oxides were remove by rinsing several times with small quantities of concentrated sulfuric acid. The total volume of concentrated sulfuric acid was adjusted to about 10 to 15 ml. The composite solution was then evaporated until fumes of sulfur trioxide were observed. rlny organic matter not distilled or destroyed at this point was eliminated by treating with concentrated nitric acid, followed by boiling to remove any excess. After dilution with water to a volume of about 125 nil., 25 ml. of 3y0hydrogen peroxide were added. The final volume was now adjusted to 250, 500, or 1000 ml., depending upon which of these volumes would give an absarbance value (log loll)of about 0.5. The absorbance was measured at 410 mp in a Beckman DC' spectrophotometer and the amount of titania was computed using the relation: grams of Ti02 = o*0261 where V = final 250 volume, A = absorbance, and the constant term is the reciprocal of the absorptivity coefficient derived per gram of titania. The uncertainty or limit of detection v a s usually about 1 0 . 2 mg. In the case of the residues where the niobium concentration was high, it was usually necessary to a-ork a t the larger volumes in
. 1°/30
'6
JOINT
'0/30B THERMOMEITER
2 M M CAPILLARY
A -
,6MM
TUBING
t
J
TO RECEIVER
8 111 -
TO RECEIVER
PROVIDED W1TW
&
ffU0 W I N O TU96
WATER-CUB
COWD+SER
6MM I D
2 M M CAPILLARY
LL
2MM CPPILLARY
TO
STOPCOW TUBING
RECEIVER
Figure 1. Still Reads
13.
V O L U M E 2 4 , NO. 3, M A R C H 1 9 5 2 order to reduce the absorbance a t 410 mp of the yellow peroxyniobate. This complex does not interfere in low sulfuric acid concentrations, although it absorbs strongly in high acid concentrations. Consequently, the uncertainty in such cases was double the above quantity. QUALlTATlVE EXPERIMENTS
A number of preliminary experiments of a qualitative character served t,o block out in a crude fashion the conditions of reaction and as a guide to the initial at'mospheric studies.
.SI1 these experiments were done in sealed tubes. In the first, 200 nig. of titania were subjected separately to the action of carbon tetrachloride, hexachloroethane, and octachloropropane a t various temperatures up to 300" C. for several hours. The reaction vessel was a heavy-walled horosilicate glass tube, which was evacuated and sealed off after the reagents were introduced. The first important observation was that the titania could not l x chlorinated under these conditions even to a small degree. Tn-o experiinental criteria were used in looking for a possible reaction : tlisappenrance of the white titanium oxide and appearance of a greenish )-ellon- color in the octachloropropane melts. \Yhile'tit~aniuni(IS.) chloride is colorless in the gaseous and liquid states as well as in carbon tetrachloride solution, when an unsaturated chlorocarbon like tetrachloroethylene'is present the solutions are yellowish green. Since this would be the case in the octachloropropane reaction, it \vas estimated that as little as 3 mg. of titanium( I T ) chloride could have been detected. Kiobium and tnntaluni(T) chlorides in solutions with tetrachloroethylene give soniewliat similar colors and could be mistaken for titanium. In viev of the catalytic effect which niobium had displayed in the chlorinat,ion of tantalum oxide ( $ I ) , equal amounts of niobium oxide and titanium oxide were reacted under conditions similar to those employed above. Chlorination of both of the oxides was alinoht coiiipletein about 2 hours a t 300" C. Schafer and Pietruck (,?3)have recently confirnied these results with carbon tetrachloride, using a temperature of 280' and a reaction time of 5 to 10 hours. An at,teinpt was next made to determine the amount of unrcactctl titania in the oxide mixture. A sealed L--tube was used with the reagents placed in one of the arms. After the reaction was complete, the empty arm was chilled d i i l e the other was heated to distill out the volatiles. The tulle \viis cut a t the bend and the residue limb was analyzed for titaiiiuin. JVith niobium present in the tube, the amount of titanium in the residue was small, usually less than 2%. With tantnln-titania mixtures the percentage was higher.
I t was concluded that atmospheric chlorination of titania would require the presence of a chlorine carrier like niobium(V) chloride in fair excess and a temperature of reaction in excess of 250' for several hours. S T U D l E S WITH NIOBIUM(V) O X l D E AND TITANIUM(1V) OXIDE
A group of studies was made a t atmospheric pressure in the distillation unit previously described for the purpose of getting preliminary ideas regarding the over-all separation efficiency of such an apparatus. An oxide mixture containing about 6 % titania and niobia mas prepared. A 0.5-gram sample was taken, ignited, and then placed in a reactor still pot along with 10 grams of octachloropropane and reacted for 3 hours with the column heaters off. This provided a certain amount of refluxing, particularly a t the start of the reaction. As the reaction progressed, however, the column became heated by the vapors from the still pot and some distillation occurred. After the reaction time was over, the still pot was cooled, usually to about 50' C., while the column was warmed up. This allowed distillation to occur. Distillation was for 3 hours with the retctor still pot a t 22j0, while the column was maintained at 175 . The still head, A , was of the straight take-off type. Some typical data obtained in this way are presented in Table TI.
485 Table 7'1. Reaction Hours a C. 250 250 250 250 275 275 275
Straight Take-Off Distillation of Titanium Conditions Distillation 225/175 225/175 225/175 200/125 225/175 225/175 225/175
% of Original Ti02
opg$ai
I n distillate 88.0 92 8 94.1 79.0 97.8 94.4 98.4
KbpOl in
In residue 8.8 2.0 0.0 14.0 2.0 2.0 1.6
Residue 98.8 99.3 97.3 99.6
..
9i:4
Inspection of this table reveals a number of items of considerable interest, which are listed numerically and discussed here as tentative conclusions. About 95% of the titania may be separated by one chlorinntiondistillation treatment, if the reaction is conducted a t 276" and the distillation a t 225/175". If this process were repeated in two stages, 99.7% of the titania should be removed from the niobium even n-ithout any improvement of the method (Conclusion I,. Varying the reaction temperature between 250' and 276' does not materially alter the percentage of titania left in the residue by the distillation treatment. This suggests that these reaction conditions are sufficient for nearly quantitative chlorination (Conclusion 11) and that the cause of the incomplete separations ohserved must be sought in the distillation conditions (Conclusion
111). The lncl, of a material balance for the titanium suggrsts t h a t part of this element is retained in the column (Conclusion K), either as an insoluble deposit on the walls or else dissolved in the small holdup volume. I t cannot be lost by leakage a t the hall joint connecting the still pot to the column, because then niohiurn would also be lost and this mould he reflected in the percentages recovered in the still-pot residue. Moreover, losses of these elements at this point would be seen as a ahite smoke and would also be associated n-ith chlorocarbon vapors which could be smelled. These two indications were not observed. If the titanium i; retained in the column as a hydrate or as hydrolyzed chloride. it becomes necessary to increase the amount of refluxing in ordei to return it to the reactor-still pot for further chlorination. On the other hand if it is dissolved in the normal column holdup, a larger throughput vould be required for its quantitative distillation. I n connection with the holdup considerations an additional point must be kept in mind. d 25-mg. sample of titanium(1V) oxide, as used in the above experiments, converted to its chloride and maintained as a gas would amount to less than 2 cc.-atrnospheres. The total free volume of the reactor and column used was 20 to 30 times greater. To effect quantitative removal of the titaniuni(1V) chloride vapor with such relative volumes of vapor and apparatus requires that some other constituent distill along with it, to carry its vapor out of the column mechanically. This consideration, as well as conclusions I11 and IV, indicates an important role for the volatile chlorocarbons formed in the course of the operation. A final conclusion (Conclusion I-)can be derived from the fact that a lowering of the still pot and column temperatures during the distillation period results in increased retention of titanium in the still pot. This indicates that temperatures somewhat in excess of 200/125' are required for quantitative distillation. Some of these conclusions were tested by one or more individual experiments. Conclusion I was tested using a reaction temperature of 250" and a distillation temperature of 225/175O. The still-pot residue was hydrolyzed and reignited. An aliquot was taken for titanium analysis and found to contain 5.2% of the original titania. The remainder of the ignited oxide was then subjected to a second chlorination-distillation treatment. Again the residue was analyzed for titanium and found to contain about 0.2%, as had
ANALYTICAL CHEMISTRY
486
been predicted. This not only showed that this separation method was capable of quantitative results but heralded the probable success of ti single-stage technique. Thus, the following experimental work was largely concerned with the development of a quantitative single-stage technique. The completeness of titanium chlorination predicted (11) was tested by determining whether all the titanium became volatile after the reaction period was concluded.
A mixture of the two oxides reacted in the usual way for 3 hours. Then the still pot was maintained a t 275'. The column was also kept hot and a t about the same temperature. This resulted in distillation of all the volatile material into the receiver and effectively removed all the chlorinated titanium, niobium, octachloropropane, and its decomposition products. The still pot contained only unreacted oxides and small amounts of carbonaceous material. This residue was ignited, weighed, and then analyzed for its titanium content. The size of the samples was about 0.1 gram with 2 to 3 grams of octachloropropane being used. The titanium in the oxide mixture taken was varied between 10 and 20%. The results obtained are tabulated in Table VII. Table VII.
Completeness of Reaction of Titania
Ti02 in Sample,
Total Oxides in Residue,
Original Ti02 in Residue,
10 16 20
0.18 0.78 32.5
0.0 0.0 0.0
%
%
70
When the sample contains between 10 and 20% titania, complete chlorination is effected. It can be anticipated that all niobium minerals will be fully chlorinated with respect to their titanium. The relatively large amount of oxide remaining in the residue may have resulted from crystals of niobium pentachloride falling into the still pot while the apparatus was being disassembled. No other explanation for that large value can be offered. K i t h the completeness of titania chlorination established, it was clear that the separative difficulties lay in the distillation technique and that a more careful examination of this part of the procedure was necessary in conjunction with the holdup problem (IV). Octachloropropane, Then heated alone, a t 275' C. undergoes a spontaneous decomposition into carbon tetrachloride and tetrachloroethylene. In the reaction still pot not only these chlorocarbons but phosgene and trichloroacetyl chloride were produced as a result of the oxide chlorination. During the reaction these volatile materials refluxed in the uncooled column, gradually heating it until finally some distillation into the receiver occurred. During this reaction period, however, the column temperature never exceeded 150" a t the top and usually was considerably less. The reaction temperature of 275' was just sufficient to maintain this operation as described. If the reaction temperature rose to 300' or 310°,vapor streaming up the column was so vigorous that untrailaed niobium(V) chloride was carried into the receiver and the separation was vitiated. This happened frequently a t this stage of the investigation. It seemed clear, therefore, that a total reflux type of head was needed in order to obviate this difficulty. By keeping the chlorocarbons in the apparatus until chlorination was complete, a refluxing liquid was provided which would not only wash back the metallic chlorides or their partially hydrolyzed forms (due to moisture in the apparatus) during this period, but would then be available as a vapor carried for the titanium. To test this idea studies were made using the still head in B. By adjusting the stopcocks, this head could be set for total reflux or for a high reflux ratio during distillation. The same mixtures of oxides were used as before, the conditions of reaction being 3 hours at0270" and the distillation being performed for 3 hours a t 225/175 . A 0.60-gram sample was used with 10 grams of octachloropropane. During the reaction cycle the apparatus was kept on total reflux a-ith the column heaters off. .After the reac-
tion was complete, distillation was performed using a reflux ratio of about 10 a t the start of the distillation stage. As the volatile chlorocarbons distilled out of the system it became necessary to reduce the reflux ratio repeatedly until a t the end of the distillation cycle virtually a straight take-off was employed. The heating conditions employed in this distillation were those which for the particular apparatus brought the niobium(V) chloride vapors within several inches of the still head.
A number of color changes in the distillate were of considerable practical interest in controlling this step. When the distillation was proceeding in a normal fashion, the yellow color of titanium(117) chloride in solutions containing tetrachloroethylene served as a rough index of the titanium in the distillate. At first the solutions were strongly colored, but as the titanium was removed the distillate increments diminished in color until a t the end stagea they were colorless. However, if any niobium(V) chloride vaporized into the still head and was caught in the distillate, this simple color pattern was obscured, because a very small amount of niobium chloride gave just as intense a reaction as larger quantities of titanium. When the distillation reaction was complete the niobium(V) chloride was drawn back into the still pot by cooling that member, while the column was kept a t its distillation tempeytures. The course of niobium(V) chloride removal from the column may be followed visually. The residue and distillate were analyzed as previously described. The data obtained are summarized in Table VIII. It can be seen that a very considerable iniprovement has r e sulted from the use of this still head. The titania in the r e d u e has been reduced; the retention of niobia in the still pot has improved. On the other hand, there is still a considerable variation in the amount of titania retained in the still pot, particularly on the higher percentage samples. It R as not easy to account for this in the light of the previous data, but possibly the chlorination was incomplete. If so, this defect might be eliminated by a someKhat higher reaction temperature. Table VIII. T i 0 in Oxide Mlxture
% 5
5 5 10
10 20 20
Effect of Refluxing Head on Separation of Titania Original TiOz, % In 1" distillate residue 85.6 0.0 0.0 7i:2 0.0 94.2 1.4 86.0 4.0 .. 0.3
..
1.5
Nb?Oh Original in Residue,
%
99.9 99.8 99.8 99.4
.. .. ..
The lack of a material balance on the titanium is a most pronounced feature of these data. There appeared to be only one way to account for these apparent losses-Le. , through titanium holdup on the extensive surfaces of the new still head. White deposits were often evident in that section of the apparatus and could not be moved into the receiver by the methods of operation employed. It was decided, therefore, to repeat these experiments, increasing the reaction temperature to 290" for 3 hours and eliminating any possible traces of moisture in the still head by flaming during the drying operation. The column holdup was determined for the purpose of obtaining a complete material balance on the titanium. A 0.6-gram sample containing about 5% titania was employed for these studies. The data obtained are summarized in Table IX. Essentially complete material balances are now obtained and the holdup percentages have been materially reduced. The residue, however, still contains about 2% of the titania. The only conclusion which could be drawn was that the volume of vapor carrier was insufficient for total titania removal. Examination of the still-pot residues showed that up to 50% of
V O L U M E 24, NO. 3, M A R C H 1 9 5 2 Table IX. In residue
2.9 Ar.
3.0 1.8 0.5 2.1
487
Complete Material Balance on Titania Original TiOr, % In holdup 0.0 0.9
1.5 0.3
0.7
In distillate 96.0 96.5 9i,1 99.2 98.2
Origins1 Xb201 in Residue, % 99.6 99:8
,.
99.8
the initial charge of octachloropropane still remained undecomposed. Apparently the decomposition reaction practically stopped, once the still pot was cooled and the distillation begun. When the volatiles formed during the reaction period were distilled, no additional amounts were formed to maintain the column operation. On cooling the still pot to bring the niobium chloride down, the small amount of titanium chloride vapor v a s also condensed and therefore appeared in the residue. Several experiments were suggested by these facts. A11 involved large volumes of vapor carriers. The first was to increa'se the size of sample and the quantity of octachloropropane about tenfold. I n this way the volume of the vapor carrier was increased about tenfold. Operating in this way without any apparatus modifications except a small increase in the size of the reactor-still pot, it was found possible to complete the reaction on total reflux in about 6 hours using a temperature of about 260". This lower temperature was required because the still head had a limited capacity for heat dissipation and therefore for total reflux. Distillation was performed with a reflux ratio in excess of 5 until the throughput fell markedly. Then the column was operated Jyith straight take-off until distillation ceased. n'ith these conditions of operation it was found that the stillpot residue was not only quantitatively but spectroscopically freed of the titanium. Therefore this experiment confirmed the need for more vapor carrier and thus provided a most important clue to tht, cause of the previous difficulties. The second group of experiments was concerned with injecting carbon tetrachloride or tetrachloroethylene into the still pot or the rolumn during the distillation in order to increase the volume of the volatile chlorocarhons available for distillation. These did not yield inipioved results, but this p a s probably due to poor drying of the solvents and the relatively crude methods of injection employed. It seems likely that this approach could be suitably developed in spite of these few negative results. The third group of experiments made an attempt to utilize the undecomposed octachloropropane remaining in the still pot for vapor carrier generation. To do this the distillation stage was periodically interrupted by putting the apparatus for a short while on total reflux. Jl-ith a higher temperature on the still pot additional amounts of the octachloropropane were expected to decompose. I n this way the supply of the lighter chlorocarbons could be rapidly reneTyed. The actual operating conditions pmployed during the distillation stage were now as follo~vs: Distillation was performed a t 225/175O for 30 minutes, follon~ed by a total reflux period a t 290 for 30 minutes, then returned to the distillation conditions as before. This type of operation 'u-as continued for 3 hours; this, resulted in three distillation stages and two reflux stages during this period with some time lost due to change-over. In subsequent discussions this type of operation is referred to as the alternate reflux-distillation technique. The same types of sample, apparatus, etc., were used as before in compiling the first three results of Table X, by this technique. These data shorn quantitative removal of the titania from the residue, a substantially reduced holdup, and nearly quantitative recovery in the distillate. The sum of the titania reported for the holdup and the distillate accounted for practically all the titania. Thus the main objective appeared to have been reacahed.
I t was necessary now to decrease the time required for such a separation, and for this purpose the water-cooled reflux head, C, was substituted. This allowed the use of a higher temperature for the chlorination reaction since the heat removal was increased. The final set of operating conditions selected after a number of trials included a I-hour reaction period a t 310", followed by a 3hour period of the alternate distillation reflux technique. The distillation was for 30 minutes a t 235/175", while the reflux time and temperature were 30 minutes and 310",respectively. Operating in this manner and with samples identical with those employed in the previous three determinations resulted in the data listed in the lower portion of Table X. It is evident that not only has there been an appreciable time reduction in this operation but that a substantial gain has been effected in the separation. These and other data of a similar sort establish this technique as satisfactory for this analytical operation. STUDIES OF OTHER OXIDE MIXTURES
Simple mixtures of niobia and titania are very rarely found as such in nature. Usually they are associated with a number of other substances, which are also difficult to separate. These include the oxides of tantalum(V), zirconium( nr), tin( IV), and iron(111). Therefore, the effect of each of these materials on the chlorination and distillation of niohia and titania was investigated. 4 known quantity of each potentially interfering compound vias added to a titania-niobia mixture, and the sample was treated in the usual manner. The effect of the added oxide on the removal of titanium was then determined by determining titanium in the still-pot residue and the distillate. This procedufe was folloned in each rase, except for the iron.
Table X .
Original TiOr. % In In holdup distillate 0.5 98.9 0.3 99.7 0.3 99.7 0.4 99.4 Water-cooled Head
In residue 0.6 0.6 0.3 Av. 0 . 5
Av.
0.0 0 0 0 3 0 0 0 0 0 0 1.2 0 2
XbzOs 500 405 500 500
ui
5 99.2 99.8 100.3 99.2 98.5 98.5 99.0
0.6 1.4
0.3 0.0 0.0 2.4 0.3 0.7
Table XI.
458 400
Alternative Reflux Distillation Technique Original ShzOb in Residue, 70 98.2 99.6 98.5 98.8 99 0 100.0 99.7 100.0 100.0
100.0 99.8
99.8
Separation of Titanium from Oxide Mixtures
Oxides Taken, Mg. TazOs ZrOz Sn0z 97 100 51.2
..
37:s
..
..
..
25
50
25
..
Ti02 33.1 25 25.5 50 25
25
Titania. Mg. In residue In distillate 0.0 32 8 0.0 24.5 0 2 25.0 0.2 49.5 0.0 25 0.0 24.2
The addition of but a few per cent by weight of iron(II1) oxide was sufficient to prevent chlorination of the titania. The niobia was only slightly chlorinated, and formed the oxychloride rather than the pentachloride. The iron, however, appeared to be extensively converted to chloride. It is possible that the iron(II1) chloride exerted a profound catalytic effect on the decomposition of octachloropropane, so that decomposition occurred long before reaction with the niobia could occur. This meant that when distillation was begun, the volatile chlorocarbons distilled out, leaving behind the oxides and iron chloride. No such effect was found with any of the other oxides. The effect of each on the chlorination and distillation of titania could then be studied. Table X I shows the effect of these added oxides. Quantitative
ANALYTICAL CHEMISTRY
488 recovery of titanium is found even in the presence of as much as 22% of tantala. Seven per cent of zirconia and 5% of tin oxide do not interfere. It is highly probable that the zirconia was not appreciably chlorinated during the reaction. In the first place, it is unreactive by itself. Secondly, weight analyses of the still-pot residue from the chlorination of mixtures of zirconia and niobia supported this conclusion. A solvent consisting of 95% anhydrous chloroform and 5% ethyl alcohol has been found to dissolve the metallic chlorides. A slurry of the still-pot residue with this solvent was prepared and filtered, and the insoluble portion was ignited and weighed. The weight of insoluble residue was identical with the weight of zirconia originally taken. Several additional experiments were performed with tin oxide. This oxide in the form of cassiterite cannot be appreciably chlorinated under the experimental conditions of this investigation. However, freshly precipitated stannic oxide (from the hydrolysis of the chloride) which is dried a t from 110’ to 200’ C., can be chlorinated completely, and completely separated by distillation under the identical conditions which are used for the titanium. The oxide form which is so reactive contains less than 2% water (determined by ignition a t 1000’ C,).
DISCUSSION AND SUMMARY The quantitative distillation of titanium and tin chlorides from niobium, tantalum, and zirconium requires nearly anhydrous conditions in the reactor and in the column and in addition requires a distilling vapor to carry the last traces mechanically into the receiver. One method of providing these conditions has been developed in this paper. With this separation successfully accomplished for synthetic oxide mixtures, the path has now been made for developing the opening attack on naturally occurring minerals, separating the iron from the sample and then putting the oxides in a state comparable to that used in this work, so that chlorination and titanium removal may be effected. The quantitative removal of titanium from niobium and tantalum mixtures containing more or less zirconium will also permit simplified determinations on such mixtures or even quantitative separations of these elements. Thus it appears now that this separation is the central part in a new system of analysis for such mixtures of elements and for their naturally occurring minerals.
ACKNOWLEDGMENT The authors wish to express their gratitude to the Office of Naval Research for the financial assistance which it offered in support of this investigation. In addition they would like to acknowledge the contributions of Isidore Adler in spectrographic analyses, Stephen Moros in his assistance in the anhydrous niobium(V) chloride preparation, Gerald Robinson in the chlorination of rhenium, Herbert Rubin in some of the pressure bomb work, and Robert Woke and Michael Yanim in routine analyses necessary to this work. LITERATURE CITED
Alimarin, I. P., and R i d , B. I., T r u d y Vsesoyut.’ Konferents. Anal. K h i m . , 2, 333 (1943). Beilstein, F., “Organische Chemie,” Berlin, Julius Springer, 1941.
Berzelius, J., P o g g . Ann., 4, 6 (1820). Biltz, W., and Voigt, A., 2.anorg. Chem., 120, 71 (1931). Cunningham, T. R., ANAL.CHEM.,20, 233 (1948). Cunningham, T. R., and Furey, J. J., Ibid., 20, 563 (1948). Eckeberg, A., Ann. chim., 43, 276 (1802). Geld, I., and Carroll, J., ANAL.CHEM.,21, 1098 (1949). Hall, R. D., J . Am. Chem. Soc., 26, 1243 (1904). Hatchett, C., Phil. Trans., 92, 49 (1802). Hermann, R., J . prakt. Chem., series of papers beginning with 38 (1846) and continuing to 1872. Hillebrand, W. R., and Lundell, G. E. F., “Applied Inorganic Analysis,” New York, John Wiley & Sons, 1929.
(13) Honigschmid, O., and Wintersberger, K., Naturw~Jsenschaffen, 22, 463 (1934). (14) Karyakin, Y. V., and Telezhnikow, P. M., J. Applied Chem. (U.S.S.R.), 19, 435 (1946). (15) Kharasch, M. S., Jensen, E. V., and Urry, W. H., Science, 102, 128 (1945). (16) Kiehl, S. J., Fox, R. I,.,and Hardt, H. B., J . A m . Chem. Soc., 59, 2395 (1937). (17) Kiehl, S. J., and Hardt, D., Ibid., 50, 1608, 2337 (1928). (18) Klinger, P., and Koch, W., Arch. Eisenhuftenw., 13, 127 (1939). (19) Knowles, H. B., and Lundell, G. E. F., J . Research S a f l . Bur. Standards, 42, 405 (1949). (20) McBee, E., Haas, H., Chao, T., and Welch, Z., I n d . Eng. Chem., 33, 176 (1941). (21) Marignac, J., Ann. chim. phys., 8, 5 (1866); 9, 249 (1866). (22) hlarignac, J., Arch. Sci. Phys. et Nut., 29, 265 (1867). (23) hIeerson, G., Zverev, G., and Zukaova, F., Tscetnye Mefal., 8, 97 (1939). * (24) Koyes, il. A., and Bray, W. C., “System of Qualitative Analysis for the Rarer Elements,” New York, Macmillan Co., 1925. (25) Oshman, V. A,, Zavodskaya Lab., 12, 154 (1946). (26) Platonov, M. S., Krivoshlykov, N. F., and Marakaev, 9.-4., J . Gen. Chem. (U.S.S.R.), 6, 1815 (1936). (27) Platonov, M. S., Krivoshlykov, N. F., and Marakaev, -4.A , T r u d y Vsesoyuz. Konjerents. Anal. Khim., 2, 359 (1943). (28) Quill, L., Editor, “Chemistry and Metallurgy of Miscellaneous
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(1942). (42) Vinogravada, N. A., and Gushtyuk, E. I., Zavodskaya Lab., 11, 223 (1945). (43) Wirtz, H., 2. anal. Chem., 117, 6 (1939). (44) Wohler, F., Pogg. Ann., 4, 6 (1820). (45) Wollaston, W., Phil. Trans., 99, 246 (1809). R E C S I Y E Dreview ~ ~ ~ March 10, 1951. Accepted December 12, 1951. Presented in part before the Division of Analytical Chemistry a t the 116th Meeting of the AMERICAN CHEJIICALSOCIETY,Atlantic City, II. J., and in part before the Fifth Annual Symposium on Analytical Chemistry, Pittsburgh Section, AMERICANCHEMICALSOCIETY,March 1951. Taken from data t o be submitted to the faculty of the Polytechnic Institute of Brooklyn b y Russell H. Atkinson i n partial fulfillment of the requirements for the Ph.D. degree in chemistry, June 1952. A major part of this research was financed through the kind assistance of the Chemical Division, Office of Naval Research.
Determination of Oxygen-Consumed Values of Organic Wastes-Correction In the article on “Determination of Oxygen-Consumed Values of Organic Wastes” [ ~ ~ N A C LH . E X .23, , 1297 (1951)] certain errors ‘occurred which however, do not invalidate any of the statistical interpretations presented. Table I. Statistical Comparison of Methods. On the organic dye waste, sample 1, the 95% confidence limits for the illadison method should be 477 instead of 466. Table 11. Ninety-Five Per Cent Confidence Limits. The data for the first two samples should be: Or anic dye waste o-Resol
Iodate 11.0 3.9
Ingols 16.9 3.0
Madison 48.0
6.9
Permanganate 7.6 5.2
Moore 3.5
1.2
W. ALLANMOORE,F. J. LUDZACE, AND C. C. RUCHHOFT
