Separation and Determination of Zirconium in Zirconia-Yttria Mixtures by Precipitation with Cupferron E. JUNE MAIENTHAL and J O H N K. TAYLOR National Bureau o f Standards, Washington, D. C. 20234
b A
method is described for the determination of zirconium in zirconiayttria mixtures which is simple, accurate, and applicable to concentrations of zirconia ranging from 4 to 97%. For 1 1 determinations within this range, the mean error was 0.05%; the maximum, 0.15%. Previous literature indicates that precipitation with cupferron yields a zirconia precipitate contaminated with yttria, but quantitative separation is achieved by a double cupferron precipitation. METHODS reported in the literature give at best only fractional separation of zirconium from rare earths. When the need arose for an accurate method of analysis of zirconia in a series of 22 binary sintered zirconia-yttria compacts ranging in composition from 1 to 97% zirconia, a method was sought which would be applicable over the entire range. Separation of rare earths from titanium or zirconium may be accomplished by ion exchange columns ( 2 , 3, 18). However. because ion exchange columns are sometimes not immediately available, it. seemed advisable to investigate other methods which would be applicable. Some of the methods considered involved separation with fluoride, oxalate, selenite, or organic reagents. Precipitation of rare earths as fluorides in the presence of zirconium is reported to be incomplete by Hettel and Fassel (5). If the zirconium concentration is high, separation of the rare earths as osalates may lead to contamination of the rare earth precipitate by as much as several milligrams of zirc.onium (15). Simpaon and Schumb ( 2 4 ) recommend the precipitation of zirconium as the basic selenite j however, occlusion may occur if more than small amounts of zirconium are present. Precipitation of the selenite may also be incomplete in the hulfate media which would result from the necessity of a pyrowlfate decomposition of the zampleP in qpestion. -i numher of organic precipitants for zirconiiim have been reported, among them hcing: tannin ( I f ) , which also requires the ahqence of sulfate; mandelic acid ( 6 ); p-bromomandelic
ANY
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ANALYTICAL CHEMISTRY
acid and p-chloromandelic acid (8); thioglycolic acid (10); .Y-benzoyl-Sphenylhydroxylamine (1)j 5,B-benzoquinaldinic acid ( 7 ) ; and, of course, cupferron. Of theqe the last seemed to be the most promiqing bince it had been proved by many, over a period of years, to give excellent results for zirconium, titanium, etc. t-nder the proper conditions, it appeared that it might be also applicable to the separation of zirconium from yttrium. A number of authors, however, have reported partial precipitation or coprecipitation of rare earths along with zirconium or titanium cupferrate (5, 6, 12, 13, 17'). Therefore, it might be expected that yttrium mould be occluded in a cupferron precipitate containing relatively larqe amounts of zirconium. I n fact, many rare earths are reported to form quantitatively insoluble complexes with cupferron at a p H of 3 to 4 in hydrochloric acid solution ( g ) . The yttrium complex was later prepared in the same way by Wendlandt (16). I t was hoped that Ijy the use of sulfuric acid a t a higher acidity, extensive coprecipitation would be prevented. Since the only other interfering element present, as shown by spectrographic analysis, in the sintered mixtures was a .mall amount of Si02, which can be removed with HF, it seemed feasible to attempt the zirconium-yttrium separation with cupferron in order to determine the extent of contamination. If necessary, corrections could be made on the zirconia precipitate by removal of the contaminating yttria with fluoride or oxalate (4) even though this recovery may not be entirely complete (23). This, however, was found to be unnecessary. The present study chows that, under the conditions deqcribed below, quantitative separation of zirconium from yttrium can be achieved by a double precipitation with cupferron. EXPERIMENTAL
Procedure. Keigh a 0.1- to 0.2gram sample, which has been finely crushed (in an agate mortar), into a large platinum crucible, add 3 grams
of KzS~O~.. Cover and fuse gently a t first, gradually raising the temperature to red heat. Add a few drops of corlcentrated sulfuric acid (to the cooled mass) from time to time as the sulfuric acid is lost through fuming and continue the fusion until the sample is in solution. Leach the melt in 20 ml. of 50% sulfuric acid (v./v.) and transfer to a 400-ml. beaker thoroughly rinsing the crucible and lid with water. Dilute to 100 ml., cool in ice, and sloivly add 25 to 30 ml. of 6% cupferron holution with qtirring. ;idd paper pulp, stir vigorously, and let settle for approximately 5 minutes. Decant and filter with suction through a double filter 1)aper on a platinum filter cone. Transfer the precipitate to the paper and wash y i t h 200 to 300 ml. of cold 10% HCI (v. v.) containing 0.6 gram of cupferron per liter. Agitate the precipitate with a stirring rod gently during each wash, taking care not to tear the paper, permitting the vacuum to pull it completely dry after each wash. Dry the precipitate slowly in a large platinum crucible, then ignite slowly to 500' C. until the organic material is completely destroyed. Cool, add 10 ml. of 50y0 H2S01and 1 to 2 ml. of HF, digest on low heat until the precipitate is in solution, then fume to strong SO3 fumes. Cool, dilute with H20, transfer to a 400-ml. beaker, and add 10 ml. of 50% H2S04. Dilute to 100 ml., cool in ice, and repeat the cupferron precipitation, filtration, and washing: Transfer the precipitate to a weighed platinum crucible and dry slowly. Ignite carefully until the organic material is destroyed, then raise the temperature to llOOo C. and ignite the Zr02 to constant weight. RESULTS A N D DISCUSSION
I n most instances only a small amount of sample of the sintered mixtures was available. Accordingly, the analyses were performed on 0.1 -gram samples for a zirconia content of around 80% or greater, and on 0.2gram samples for smaller amounts of zirconia. ;\lthough the sintered compacts had been previou.;ly ignited to about 1200' C., they fused without difficulty in potassium pyrosulfate with the addition of a few drops of sulfuric acid from time to time. A single cupferron precipitate was found to be con-
Table 1.
Results on Synthetic ZirconiaYttria Mixtures
ZrOn Added, Found,
c/o
Yo
5.25 10.82 26.11 26.67 40.30 40 59 70 14 75 27 79.46 86.20 95.39
5.23 10 86 26.10 26.67 40.22 40 53 70 09 75 21 79.55 86.35 95.40
Mean error,
Rel. error,
0.02 0.04 0.01
0.38 0.37 0.04
0.00 0.08 0 06 0 05 0 06
0.00
Yo
0.09 0.15 0.01
7%
0.20 0 15 0 07 0 08 0.11 0.17 0.01
taminated with an average of 0.4 mg. of either coprecipitated yttria or alkali salts from the pyrosulfate fusion. The amount of contamination was independent of sample size or percentage composition of the mixtures. Yttrium was not detected by spectrographic analysis of the second cupferron precipitate. The method was tested by analysis of 11 synthetic mixture:, of zirconia and yttria ranging in zirconia content from 5 to 95oj,. Blanks were taken through each step of the prccedure. The results, given in Table I , show a mean error of 0.05%. The relative error ranges from 0.38 to 0 00% for samples between 5 and 95%, respectively. A
sample which had been found by a n ion exchange procedure in another laboratory to contain 52.11% zirconia, gave results of 52.03 and 52.09% by the double cupferron precipitation, showing good agreement between the two met hods. Analysis of a single sample may be completed in about 2 days elapsed time, requiring approximately 4 hours of the operator’s attention. Eight samples are a convenient number to be done in any one set. Twenty-four samples may be easily completed in 5 days. The double cupferron procedure would undoubtedly be also applicable to separation of titanium from yttrium and probably to the separation of other rare earths from titanium and zirconium. ACKNOWLEDGMENT
The authors thank Elizabeth K. Hubbard for performing the spectrographic analysis, and Martha S. Richmond and John R. Baldwin for furnishing the sample analyzed by ion exchange which was used as a control, and also for supplying the pure zirconia and yttria used to make u p the synthetic samples. LITERATURE CITED
(1) Alimarin, I. P., Tse, Y. H., Zh. Analit. Khim. 14, 574 (1959).
(2) Codell, M., “Analytical Chemistry
of Titanium Metals and Compounds,” p. 230, Iilterstience, Sew York, 1959. (3) Hettel, H. J., Fassel, V. A., ANAL. CHEM.27, 1311 (1955). (4) Hillebrand, W. F., “The Analysis of Silicate and Carbonate Rocks,” U. S. Geol. Survey Bulletin 700, p. 176 (1919). (5) Hillebrand, W. F., Lundell, G. E. F., Bright, H. A., HoHman, J. I., “Applied Inorganic Analysis,” 2nd ed., pp. 119, 572, 578, Wiiey, New York, 1953. (6) Kumins, C. A., ANAL.CHEM.19, 376 (1947). (7) Majumdar, A. K., Banerjee, S., Anal. Chim. Acta 14, 306 (1956). (8) Oesper, It. E., hlingenberg, J. J., ANAL.CHEM.21. 1509 (1949). (9) POPOV, A. I.,’ Wendlandti W. w., Ibid., 26, 883 (1954). (10) Sant, S. B., Sant, B. R., Talanta 3 , 95 (1959). (11) Schoeller, W. R., Analyst 69, 260 (1944). (12) Schoeller, W. R., Powell, A. R., “Analysis of Minerals and Ores of the Rarer Elements,” 3rd ed., p. 120, Harper, New York, 1955. (13) Scott, ,W. TV., “Standard Methods of Chemical Analysis,” 5th ed., p. 1100, Van Nostrand, New York. 1939. (14) Simpson, S. G., Schumb, W. C., J . Am. Chem. SOC.53, 921 (1931). (15) Gckery, It. C., “Analytical Chemistry of the Rare Earths,” p. 48, Pergamon Press, New York, 1961. (16) Wendlandt, W. W., ASAL. CHEM. 27, 1277 (1955). (17) Wilson, C. L., Wilson, D. W., “Comprehensive Analytical Chemistry,” 1-01. IC, . p. - 499, Elsevier, Amsterdam, 1962. (18) Wood, D. F., Turner, M., Analyst 84, 725 (1959).
RECEIVED for review February 11, 1964. Accepted March 19, 1964.
The Premixed, Fuel-Rich, Oxyacetylene Flame in Flame Emission Spectrometry A. P. D’SILVA,’ R. N. KNISELEY, and V. A. FASSEL Institute for Atomic Research and Department of Chemistry, Iowa State University, Ames, Iowa
b An improved premixed, oxyacetylene burner, which can b e safely operated under fuel-rich conditions, is described. Observafion of the atomic line spectra emitted in the interconal zone of this flame has made it possible to detect, for the first time, analytically useful lines for Ce, Hf, Ta, Th, U, and Zr in a simple flame. Sensitivities of detection for the strongest lines of 26 elements, whose lines are not emitted with significant intensity in stoichiometric hydrogen or l i yd roca rbon-fuel flames, are tabulated.
T
of a fuel-rich, oxyacetylene flame (1-3) has greatly increased the scope of application of Beckmantype burners in flaml. emission spectrometry. However, the high spectral background emitted by this flame has H E USE
limited the detection sensitivities attainable and difficulties have been encountered from encrustation of the oxygen orifice. .1 recent communication ( 4 ) described a simple modification of the standard burner which minimizes these difficulties. The first model provided a graphite premixing channel for the acetylene and oxygen after atomization had occurred. h more refined version of this burner is shown in Figure 1. The stainlmssteel insert in the Teflon barrel offers distinct advantages over the graphite channel. First, there is a reduced tendency for flooding from excess atomized solution since this excess readily drains from the tip into the reservoir. Second, contamination or so-called memory effects, occasionally exhibited by the graphite tube after prolonged use, are also minimized. If
contamination occurs, the tube may be readily cleaned and reused. However, the use of stainless steel requires that greater care be taken to protect the burner tip from excessive heat. Thus, continuous atomization of sample or solvent is required to provide adequate cooling of the burner tip, and the solvent level in the reservoir must be maintained. If stainless steel is attacked by the sample solutions, inserts of other structural materials possessing similar thermal conductivity and stability may be substituted. EXPERIMENTAL
The spectrometer and associated equipment have been previously described (1, s), as has the alignment Present Address: rlnalytical Division, A.E.E.T. Bombay, India. VOL. 36, NO. 7, JUNE 1964
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