1095
V O L U M E 21, NO. 9, S E P T E M B E R 1 9 4 9 Table 111. Estimation of Uranium in Uranium-Iron Solutions Using Mixed Color Method U Present, Mg. 0.530
0,424 0.318 1.060 1.060 0.530
Fe Added, Mg. 0.025
U Found, Mg.
0.050 0.100 0,100
0.026 0.050
0.540 0.420 0.315 1.080 1.060 0.530
Error, fl.9 -0.9 -0.9 i1.9 10
*O
The mixed color method for solutions containing iron is not recommended where the ratio of iron t o uranium is greater than 1 part of iron t o 5 parts of uranium. With larger concentration of iron, the compensation for interference becomes greater than 50% of the total value.
large number of anions. The method is uot specific for cation solutions but, if necessary, certain of the cation interferences may be eliminated. LITERATURE CITED
Currah, J. E., and Beamish, F. E., -4iv-a~. CHmr., 19, 609 (1947). Hillebrand, W.F., and Lundell, G. E. F., “Applied Inorganic Analysis,” p. 60, Xew York, John Wiley &- Sons, 1929. Rodden, C. J., and Warf, J. C., “Analytical Chemistry of the Manhattan Project, Uranium,” National Nuclear Energy Series, in press. Sandell, E. B., “Colorimetric Determination of Traces of Metals,” pp. 433-8, New York,, Interscience Publishers, 1944. Spedding, F. H., Voight, A. F., Gladrow, E. M.,Sleight, N. R., Powell, J. E., Wright, J. M., Butter, T . A., and Figard, P., Manhattan District, MDDC-411. Swank, H. W., and Mellon, M. G., IND. ENG.CHEM.,ANAL.ED., 10, 7 (1938). RECEIVED December 11, 1948. Based on work performed under Contract
SUMMARY
7405 eng. 26 for the Atomic Energy Project:
A4mmoniumthioglycolate may be used for the accurate estimation of small amounts of uranium in the presence of a relatively
the information covered therein will appear in the National Nuclear Energy Series (Manhattan Project Technical Section) as part of the contribution of the Oak Ridge h-ational Laboratory.
Spectrographic Determination of Impurities in Beryllium and Its Compounds A. LEE SMITH1 AND VELMER A. FASSEL
Zowa State College, Ames, Zowa
A method is described for the simultaneous q u a n t i t a t i v e spectrographic determination of aluminum, calcium, chromium, iron, manganese, magnesium, and silicon in b e r y l l i u m metal and its compounds. The procedure involyes the conversion of the sample to b e r y l l i u m oxide, the addition of graphite powder, tin oxide, and barium hydroxide to the b e r y l l i u m oxide, and the e x c i t a t i o n of this m i x t u r e in a h i g h amperage direct current arc. The m i x t u r e that is added to the b e r y l l i u m serves the dual purpose of stabilizing the arc discharge and providing for good internal standard compensation of excitation variables. The e x p e r i m e n t a l error is about *59’0 of the amount present.
B
ERYLLIGM metal and its oxide are finding increasing
uses in various industrial (18, 18, 98) and nuclear energy (26) applications, but little is known about the effects of impurities on the physical properties of these materials (9, 14, 18, 28). KO analytical methods that are directly applicable to the determination of the common impurities in beryllium-base materials have been reported in the literature. Because spectrographic methods are particularly useful for the simultaneous determination of a number of impurities, it seemed appropriate to investigate the application of this technique to these analyses. The carrier distillation technique (23, 24, 86) has been applied to the spectrographic analysis of beryllium oxide, but this method is not applicable to the determination of important impurities such as calcium, aluminum, and silicon, whose oxides are too refractory to be vaporized satisfactorily during the carrier distillation. This technique is also encumbered by the influence of the manner of preparation of the oxide matrix on the per cent of the impurity which is volatilized and excited during the carrier distillation ( Z ) , 1 Present address, Chemistry Department, Ohio State University, Columbus, Ohio.
EXPERIMENTAL
Reagents. In any analysis for small amounts of common impurities, contaminations from manipulations and reagen te becomes a major Droblem. All chemical work was therefore carried out in platinum ware and only purified acids and ammonium hydroxide were used. The purified hydrochloric acid and ammonium hydroxide were obtained by passing the respective gases into distilled water in quartz containers. The nitric acid was distilled in a quartz distilling apparatus and was stored in quartz containers. Apparatus. The following equipment was used in this investigation: a Jarrell-Ash, Wadsworth mounting, 21-foot grating spectrograph ( I I ) , a water-cooled excitation stand (22), a 250volt direct current arc source of 20-ampere capacity (8), an A.R.L.-Dietert developing machine (21), and an A.R.L.-Dietert densitometer (7). The external o tical system used with thr. spectrograph has been described (87. Preliminary Experiments. The desirability of developing an analytical method applicable to the analysis of both beryllium metal and its compounds required that the samples be excited in a form which could be easily obtained from the metal, oxide, or other compounds. Beryllium oxide best satisfied thew requirements.
1096
ANALYTICAL CHEMISTRY
-
Table I.
Operating Conditions for Analysis of Beryllium Oxide
Composition of sample charge
l.OY0 tin oxide 1 0 . 0 % barium hydroxide 3 3 . 3 % graphite 0 5 . 7 % beryllium oxide 15 mg. Anode (lower electrode) 0.25-inch diameter graphite, 0.75 inch long, drilled to wall depth of 2 mm. with wall thickness of 0.5 mm. Supported on 0.125-inch diameter graphite pedestala Cathodes (upper electrodes) 0.125-inch diameter graphite, 1 inch long and nointed 4hm. 250 volt d.c., 16 amperer 20 seconds 2750-4000 A . 2nd 0 . 0 5 mm. %step sector pattern SA No. 1 4 minutea at 21' C. in Emtman D-19
Weight of charge Type of electrodes
Analytical gap Excitation source Duration of excitation Wave length photographed Order Slit
5 Fabricated from National Carbon Company special spectroscopic graphite rods.
t
'r!,
vaporization behavior of the beryllium and the impurities to be determined eliminated the use of beryllium lines for internal standard purposes. This observation led to further studies on arc stability and rates of vaporization of mixtures of beryllium oxide, powdered graphite, and oxides or hydroxides of other metals whose determination in beryllium was not important. The objectives of this study were to find a metallic oxide or hydroxide which, when added to the beryllium oxide-graphitc mixtures, would fulfill the internal standard requirements mentioned previously. No individual oxide possessed these qualifications, but a combination of tin oxide and barium hydroxide appeared to offer the best possibilities. Figure 1 illustrates the rates of vaporization of several of the impurities as compared to the barium and the tin. A detailed study was made to determine the optimum experimental conditions for the excitation of a mixture of beryllium oxide, powdered graphite, barium hydroxide, and tin oxide. The operating conditions that were selected are detailed in Table I. The graphite-beryllium oxide ratio was not so critical as indicated in the table. The preliminary experiments were performed on mixtures in which the graphite was standardized at 33.3%, while the other components accounted for the remainder. The behavior of the 10% barium hydroxide was similar to a distillation carrier (dS), as the impurities were virtually completely volatilized within the 18- to 20-second
Table 11.
Line Pairs Used in Analysis of Beryllium Oxide
Line Pair
A. AI I 3961.527 Ba I 3993.404
0
0
I
I
I
I
3
6
9
I2
I ' I ' I IS
18
21
Ca Sn Cr Sn Fe
I1 3179.332 13141,809 11 2843.252 12913,542 I 2966.900 Sn I 3032.775 Fe I 2813.288 Sn 1 2 9 1 3 . 5 4 2 Mg I 2781.417 Sn I 2913.542 M n I1 2949.209 Sn 1 2 9 1 3 , 5 4 2 Mn 1 2 8 0 1 , 0 6 4 Sn I 2913.542 Si I 2881.578 Sn I 2850.618
I 24
T i m e in Seconds Figure 1. Distillation Rates of Impurities from Beryllium Oxide-Graphite Mixtures The direct current arc has been the most convenient excitation source for the analysis of inorganic materials, but the poor reproducibility usually associated with this discharge has greatly limited its use for quantitative applications. This poor reproducibility arises chiefly from the large effective excitation temperature variations produced by wandering of the cathode spot and general arc instability, and the fractional distillation effects which institute large variations in the analytical intensity ratio during the excitation unless internal standards with almost identical vaporization characteristics are utilized. The purpose of the preliminary experimental work was to establish the experimental conditions necessary to obtain a stabilized arc of reproducible character and to find suitable internal standards whose vaporization and excitation response were similar to the impurities to be determined. Direct current arcs of currents as high as 18 amperes between graphite electrodes did not provide an electrode temperature high enough to vaporize an amount of the beryllium oxide from the electrode cavities to stabilize the discharge. Furthermore, the formation of a mobile bead of the oxide caused frequent ejection of the material from the electrode cavity. The admixture of powdered graphite satisfactorily eliminated the formation of mobile b e d s but still did not achieve the desired stabilized excitation conditions. Moving plate spectrograms (19) showed that the impurities under consideration vaporized uniformly during the initial period of the arcing cycle, while the beryllium was vaporized during the entire period the sample was being consumed in the arc. Thrse large differences in the
Concentration Range P.p.m.
Excitation Potential Electron voltr
50-2500
3.1 4.3
100-5000
100-5000
18.1 6.1 12.6 6.4 4.4 6.2 4.2 6.4 7.2 -
50-1000
12.6
5-60
4.3 6.4
50-1000 90-500 500-5000
-
6.4
6.4
50-5000
5.1 5.4
Table 111. Precision Data on a Typical Sample Intensity Ratios AI/Ba Ca/Sn Cr/Sn Fe/Sn' Mn/Snb Mg/Sn 3.32 2.14 0.45 0.72 1.37 1.47 3.45 2.31 0.47 0.74 1.40 1.49 3.69 2.21 0.43 0.72 1.29 1.43 3635 SA 2 ,, 2.29 0 . 5 0 0.72 1.40 1.41 , . 2.27 0 . 4 8 0.71 1.39 1.49 SA 1 3.40 2.42 0 . 5 0 0.77 1.38 1.30 3642 3643 SA 1 3.55 2.27 0.53 0.82 1.33 1.42 0.51 0.78 1.47 1.39 2.37 3.50 1.56 0.79 1.39 0.51 3644 SA 1 3.28 2.75 0.74 1.33 1.29 2.45 0.48 3.85 1.64 0.79 1.40 2.50 0.51 3649 SA 1 3.40 0.49 0.73 1.55 1.40 2.45 3.97 3652 3-0 ,. 2.48 0.44 0.67 1.38 1.46 , , 2.66 0.52 0.77 1.37 1.49 , . 2 . 7 1 0 . 5 3 0.80 ' 1 . 4 1 1 . 5 6 Mean %deviation 5 . 1 5.8 5.1 4.7 1.7 4.3 Fe 2 8 1 3 . 3 0 Line pair * Sn 2913.5 Mn 2801.1, b Line pair ___ Sn 2913.5 Plate No. 3606
Plate Type SA 1
Si/Sn 1.77 1.77 1.85 1.64 1.56 1.79 1.81 1.69 1.61 1.83 1.79 2.00 1.73 1.60 1.76 4.8
V O L U M E 2 1 , NO. 9, S E P T E M B E R 1 9 4 9 period during which the barium was vaporizing and stabilizing the arc discharge (Figure 1). The tin oxide was added solely as an internal standard; its concentration was determined by line intensity relationships. KO significant variation of the integrated intensity ratios was observed when the arcing current was varied between 14 and 18 amperes, and when the charge weight was varied between 10 and 20 mg. In selecting the line pairs, consideration was given to their freedom from interfering lines, intensity-concentration relationship, excitation potentials, and proximity to the other lines being measured. A tabulation of the wave lengths (10) of the selected line pairs, the concentration range for which they are applicable, and their excitation potentials ( 6 , 10, 13, 15, 16, 90) is found in Ca I1 3179.332 A. Table TI. Several line pairs such as Sn 13141.809 b. ' Mn I1 2049.209 A. Cr I1 2843.252 b. , and Sn 12913.542 b. show unfavorable Sn 12913.542 b. rxcitation potential relationships; the choice of these pairs was dictated by the other considerations. The data in Table I11 show that the excitation fluctuations in the light source were sufficiently reduced so that the reproducibility for the line pairs with unfavorable excitation charactpriitirs was not seriously imp:tired. Quantitative Calibrations. The synthetic standards for all the impurities except silicon were prepared by dissolving weighcd amounts of distilled beryllium basic acetate (1, 2'7) in 1 t o 1 distilled nitric acid and then adding the proper volumes of standard solutions of the various impurities. The solutions mere evaporated to dryness and ignited to the oxides in a niufffc furnace a t 700" C. The silicon standards were prepared by grinding pure beryllia with silica in a boron carbide mortm and making successive dilutions of this mixture. The other mixture components were incorporated with all the standards by dry grinding in a boron carbide mortar. These standards were then excited and photographed under the conditions detailed in Table I. T h e per cent transmission data from the denhitometric measui emerits were converted to intensity ratios in the usual manner ( 4 , 1 7 ) . Residual corrections, if necessary, were made by the zero-intercept method of Cholak and Story (5). Figure 2 illustrates the working curves obtained by plotting log intensity ratio against log concentration. The aluminum and silicon curves were found to level out a t higher concentrations because of self-reversal of the lines, but no suitable alternative lines could be found in the wavelength region covered. The residual correction mentioned above included the total
1097 Table IV. Comparison of Spectrographic and Spectrophotometric Values for Iron and Manganese Iron Spectrophotometric P.p.m.
Sample
Spectrographic P.p.m.
MS-BL MS-BI MS-BF AIS-BO
560 2880
600 2880
6.9
620
640
240
230
3.2
% 0.0 4.2
Av.
*2,1
concentration of the various impurities in the base berylliuni basic acetate and in the mixture (hereafter called graphite mixture) of powdered graphite, barium hydroxide, and tin oxide The small amount of the impurities present in the graphite mixture became significant when lower concentration of the impurities were measured in actual samples. Because the barium hydroxide and the graphite largely characterized arc discharge, it was found possible to make a sufficiently accurate determination of these impurities in the graphite mixture by exciting the latter under the usual experimental conditions and determining the concentration from the extrapolated working curves. These concentrations were then subtracted from the respc,ctire values obtained when qamples were analyzed. Procedure for Analyzing Samples. Beryllium metal is UOIIverted to the oxide by cautiously dissolving the metal in purified dilute hydrochloric acid, adding an excess of purified ammonium hydroxide evaporating the slurry to dryness, and igniting it a t 700" for 1 hour. Samples of the halide salts are readily converted to the oxide by pyrohydrolysis ( 5 ) , while nitrate and hydroxide samples are converted to oxide by direct ignition. The resulting oxide is ground in a boron carbide mortar with the proper amount of previously prepared graphite mixture and charges of 15 * 1 mg. are weighed into the electrodes and excited as detailed above. The concentrations of the impurities are then determined from the working curves in the usual manner The correction for the impurities in the graphite mixture i p subtracted from the calculated percentage.
6.
DISCUSSION O F RESULTS
Precision data obtained from repeated analysis of the W I I ~ sample are shown in Table 111. Several of the elements which
C O N C E N T R A T I O N , P A R T S P E R T H O U S A N D IN B e 0
Figure 2.
Difference
Calibration Curves for Analysis of Beryllium Oxide
1098
ANALYTICAL CHEMISTRY
LITERATURE CITED
Churchill, J. R., IND. ENG. CEIEM.,ANAL.ED.,16, 653-70 (1944). Cline, W. D.. and Warf, J. C., CC-2723 (June 30, 1945)*. Curtis, C. W., Phys. Reu., 53, 474-81 (1938). Dietert, H. W., and Schuch, J., J . Optical SOC.Am., 31, 54-7 (1941). Fassel, V. A., and Wilhelm, H. A,, Ibid., 38. 518-26 (1948). Geller, G. E., Yavorsky, P. J., Steierman, B. L., and Creamer A. S., J . Research Natl. Bur. Standards, 36, 286 (1946). Harrison, G. R., “M.I.T. Wavelength Tables,” New York. John Wiley & Sons, 1939. Jarrell, R. F., J . Optical SOC.Am., 32, 666-9 (1942). Kawecki, H., TTan8. Electrochem Soc., 89, 229-36 (1946). Kiess, C. C., J . Research Xatl. Bur. Standards, 21, 185-205 (1938). Kjellgren, B., Trans. Electrochem. SOC.,89, 247-50 (1946). McLennan, J. C., and McLay, A. B., Trans. Roy. SOC.Can., 20, 111, 89-120 (1926). Meggers, W. F., J . Research Natl. Bur. Standards, 24, 163-73 (1940). Pierce, W. C., and Nachtrieb, N. H., IND. ENG.CHEM.,A N ~ L ED., 13, 774-81 (1941). Raynor, G. V., J.Roy. Aeronaut. SOC.,50, 390-400 (1946). Richardson, D., “Proceedings of 5th Summer Conference on Spectroscopy and Its Applications,” pp. 64-70, New York. John Wiley & Sons, 1938. Russell, H. N., and Moore, C. E., Trans. Am. Phil. SOC..34 111-79 (1944). Schuch, J . , J . Optical Soc. Am., 32, 116-18 (1942). Scribner, B. F., and Corliss, C. H., J . Optical SOC.Am., 33, 515-18 (1943); J . Research Aratl. Bur. Standards, 30, 41 (1943). Scribner, B. F., and LMullin, H. R., Ihid., 37, 379-89 (1946). Smith, A. L., CC-2941 (June 22, 1945)*. Smyth, H. D., “Atomic Energy for Military Purposes,” Paragraphs 2.10, 2.36, 4.19, 4.20, and 6.22, Princeton, N. J.. Princeton University Press, 1945. Tornkins, F. S.,and Bubes, I. S.,CC-1325 (Feb. 1, 1944)*. arid Tolmsch, L. J., CC-3524 Tomkins, F. S.,Cressman, G. W., (May 27, 1946)*. Van duwers, O., et al., “Beryllium, Its Production and Application,” pp. 5-96, New York, Iteinhold Publishing Corp., 1932. *Scientific reports of the Manhattan Project and the Atomic Energy Commission.
(1) Archihald, E.H., “Preparation of Pure Inorganic Substances.” p. 86, New York, John Wiley & Sons, 1932. (2) Ayers, B. O., and Fassel, V. A., CC-2940 (Dee. 31, 1945)*. (3) Cholak, J., and Story, R. V . . J. Optical SOC.Am., 32, 502-5 (1942).
RECEIVEDOctober 1, 1948. Presented before the Division of Analytical and Micro Chemistry st the 114th Meeting of the . i M E R I C A K C H E M I C A L S O C I E T Y ,St. Louis, Mo. Contribution 30 from the Institute for Atomic Research, Iowa State College. W o r k performed under contract W-7405 eng-82 for the Atomic Energy Commission.
Table V. Element
D a t a from Recovery Experiments Amount Added P.p.m.
Amount Found P.p.m.
Error
7c
could be checked spectrophotometrically were determined by the chemical analytical group, and the results from the two procedures are compared in Table IV. Included in Table V are typical results from recovery experiments in which known amounts of the impurities in question were added to a beryllium oxide base which had been previously analyzed. The results in Tables 111, IV, and V indicate that adequate accuracy and piecision can be achieved b y this method. Table I11 shows that the intensity ratios did not change significantly when the emulsion type n-as varied. It is therefore possible to increase the sensitivity for most elements by using faster plates. The concentration range can also be increased by using a low contrast plate such as Eastman Spectrum Analysis So. 2. The high dispersion of the spectrograph used in this investigation is not an essential requirement for these analyses; the method should therefore be adaptable t o any instrument of moderate dispersion. It should also be possible to extend the method to the determination of most of the metallic inipuriticin beryllium and its compounds. ACKNOWLEDGMENT
The authors wish to thank C. E. Reed for his assistance with the experimental work and A. B. Carlson for performing the spectrophotometric analyses.
Colorimetric Determination of Columbium and Tungsten in High-Temperature Alloys ISIDORE GELD AND JACOB CARROLL Material Laboratory, New York Naval Shipyard, Brooklyn, N. Y .
T
HE authors recently had occasion t o analyze high-temperature alloys containing both columbium and tungsten. The separation of these elements b y classical methods was a difficult and tedious procedure. Because tungsten accompanied columbium in precipitation reactions, i t was most difficult t o obtain a clean-cut separation of these elements, in one precipitation. Hillebrand and Lundell (Y), referring to the separation of the mixed oxides of columbium and tungsten, state, “Extraction of the mixed oxides with ammonium hydroxide or ammonium sulfide, or extraction with water after a fusion with sodium carbonate and sulfur are all unsatisfactory, as are also the boiling of an alkaline solution of the tungstate, columbate, and tantalate with ammonium nitrate or treatment of the alkaline solution with magnesia mixture.” Referring to the separation of columbium
from tungsten, using cupferron in a tartaric acid-sulfuric acid solution, they maintain, “Tungsten is partially precipitated no matter how much sulfuric and tartaric acids are used.” T o avoid such lengthy and tedious separations with their inherent possibilities of error, attention was turned t o eliminating separations of columbium from tungsten by determining both elements colorimetrically from the same solution. A solution of columbium and tungsten in concentrated sulfuric acid (11, 1%’) was found well suited for such colorimetric determinations. I n accordance with the work of Klinger and Koch ( 8 ) , columbium was determined in an aliquot of this solution by means of the yellow percolumbic acid produced by hydrogen peroxide. Titanium interfered by also producing a yellow color with hydrogen peroxide in concentrated sulfuric arid. Thanheiser ( 1 7 ) mini-
