Determination of Tetrafluoroborate with Tetra phe nyla rson ium Chloride niedium porosity. The precipitate is Excess standard TP.1C is added to SIR: Two methods for the determinafirst washed with 3 ml. of cold dilute precipitate tetraphenylarsoniuni tetration of the tetrafluoroborate anion ainnionium hydroxide and then with 30 fluoroborate from the fluoroborate soluhave been reported in the literature: to 40 ml. of a solution ilrepared by tion and the excess is determined a gravimetric procedure (3) using combining 250 nil. of a saturated d u Yitron (1.4-dipheny1-3,5-endanilo-4,5-spectrophotonietrically in the ultration of tetraphenylarsoniuni tetrafluoroviolet . dihydro-1,2,4-triazole) acetate as the borate with 10 ml. of concentrated precipitant and an indirect titrimetric ",OH. After transfer of the precipitate is complete, the precipitate is method (4) using cetyltriiiiethylamEXPERIMENTAL washed with 5 nil. of cold dilute SH,OH. moniuni chloride as a precipitating The precipitate is then dried to constant reagent. The Sitron tetrafluoroborate Tetraphenylarsonium chloride reaweight a t 105" C. is too soluble for a simple gravimetric gent was obt,ained from G. F. Smith IXDIRECT SPECTROPHOTOJIETRIC DEprocedure, and it is necessary to apply Chemical Co. Ammoniuni tetrafluoroTERMISATION OF TETRAFLUOROBOR.~TF: an empirical correction factor.' The borate was donated by the OzarkWITH TP-IC. Five milliliters of soliisecond method has the disadvantage of llahoning Company, Tulsa, Okla. Sition containing 0.02 to 0.04 gram of tron reagent was obtained froin Eastnian requiring standard solutions of three S H a B F a is pipetted into a 25-ni1. voluOrganic Chemicals. different, reagents. metric flask. .idd 5 ml. of concenThe spectrophotometric nieasuretrated SHaOH and 10.000 inl. of ,standCoursier, Hure, and Platzer ( 2 ) have ments were made on a Heckman DLard TPXC (0.06689M). Dilute to 25 developed a method for determination quartz spectrophotometer , equipped nil. and let sit with occasional shaking of borates whic,h involves conversion of with a photomultiplier tube detector. for 1 hour. Take a 5-ml. aliquot of the the borates present to tetrafluoroborate The amnionium tetrafluoroborate supernatant liquid using a pipet with a and extraction of tetraphenylarsonium sample was analyzed piece of filter paper wrapped tightly tetrafluoroborate into chloroform. The method (3) for conili around the tip and held by a rubbt,r The results of this ana boron is subsequently determined band. Dilute to 2 liters and measure Table I. slmtrophotometrically using curcumin the absorbance at 220 m p 2's. a reference The solubility of the tetraphenylas a reagent. made by diluting 1 ml. of concentrated arsonium tetrafluoroborate (TPAB) pre",OH to 2 liters. ~ ~ e t r a ~ h e n ~ l a r s o nchloride i u ~ i i (TPcipitate was determined using a spectroAC) forins a sparingly soluble salt with photometric method developed previtetrafluoroborate ion, which is the basis ously ( 1 ) . The solubility was found to RESULTS A N D DISCUSSION of the two methods reported in this be 4.66 X lo-' molar at 25' C. paper. The spectrum of tetraphenylarsonium The ammonium tetrafluoroborate was .i gravimetric method has been ion was discussed in a previous paper analyzed gravimetrically and by the (1). The indirect method uses an abdeveloped which, because of the solubilindirect spectrophotometric method sorption inaxinium a t 220 m p for the ity of the precipitate, utilizes a conwith TP.1C. The reyults are given in of excess TP.iC. The determination trolled washing procedure. This molar absorptivity at this wive length Tables I1 and 111. The results of the method gives results comparable to is 35,700 liters per mole Centimeter with gravimetric procedure in Table I1 are those obtained with the Sitron proa standard deviation of 220 liters per somea hat lower than the theoretical cedure. mole centimeter. percentage of BF4- in SH4BF4,corThe second method utilizing TPAC is The ammonium tetrafluoroborate responding to a purity of 98.27,. an indirect spectrophotometric method. sample was then analyzed by the two above methods according to the following procedures. Procedures. GRhVIhIETRIC DETERTable I. Gravimetric Determination of MISATION OF TETRAFLUOROBORATE Tetrafluoroborate with Nitron WITH TP-LC. h 10-nil. aliquot of Table 111. Indirect Spectrophotometric solution containing approximately 0.03 % Determination of Tetrafluoroborate with \vt. BFagram SH413Fais taken. Five milliliters 0.06689 Molar TPAC SH4BF,, Wt of Corrected in of l5Jl S H 4 0 H and 5 nil. of water are grams ppt w t . ppt. N H ~ B F I added immediately before precipitating wt. BFj82 51 volume of 0.07M with TP;IC. 1 3770 1 3959 0 3670 sample, Absorb- LIillimoles in 82 60 1 3785 1 3974 0 3670 TPAC sufficient to give a final concengram ance BF4?;H,RFd 1 3963 82 54 0 3670 1 3774 tration of 0.018J1 is added slowly with 82.1 1.254 0,3176 0,03360 stirring. The solution is allowed to LIean 7 BFd- 82 55 81.7 1.260 0.3160 0.03360 Std. dev. 0 05 stand in an ice bath for 1 hour and fil0,2244 80.2 1.587 0,02430 tered on a sintered glass crucible of 81.1 1.578 0.2269 0.02430 0.2772 84 T 0.02843 1.406 83.6 1.418 0.2738 0,02843 0.3176 81.9 1.261 0.03368 0.3148 81.2 Table II. Gravimetric Determination of Tetrafluoroborate as ( C ~ H ~ , ) ~ A S B F ~ 0,03368 1.271 0,3396 81.0 cc 1,182 0,03642 81.0 1.182 0 3396 0.03642 Av weight, BFd'in 82 6 1.518 0.2460 0.02585 Solution \ I t SH4BF4 S o of detns (C6H,)aSsBF, NHaBF, Std dev 82 3 1 522 0 2449 0.02585 81 46 0 14 3 0 1187 1 0 02691 0,2309 80.0 1.572 0.0250ia 81 53 -1 0 02965 1 0 1309 80 0 0.2309 0.02507a 1.572 81 42 0 07 3 0 1097 3 0 02488 LLlean 9; BFa81.7 81 17 0 07 3 0 1244 4 0 02h30 Std. dev. 1 . 3 0 02665 3 0 1178 81 02 0 14 Av. 81 29 5 These samples each contained 0.2115 gram of KF. Each aliquot of solution No. 5 contained 0.2644 gram of KF. (1
2 5 12
ANALYTICAL CHEMISTRY
As in the determination of hexafluorophosphate, fluoride ion did not interfere a t the indicated concentration levels to a significant extent. The results obtained with bot'h methods were somewhat lower than those obtained using the Nitron procedure with the empirical correction factor. When no correction factor was applied to the weight of the Nitron tetrafluoroborate precipitate, the procedures were in agreement. The precision obtained with the spectrophotometric method was rather poor, but was within the permissible precision for a spectrophotometric determination. The relative standard deviation was increased because the method involved taking a difference. Ammonium ion will interfere when
present in large quantities because of a slight absorption a t 220 nip. Using a blank as reference will remove this interference. The gravimetric method using TPAC would appear to have three advantages over the Nitron procedure. TPAC is a much more stable reagent than Nitron, the TPAB precipitate is purer than the Nitron tetrafluoroborate precipitate, and the procedure as developed can be used for smaller amounts of tetrafluoroborate. The ammonium tetrafluoroborate sample was almost certainly not stoichiometrically pure, and development of an empirical correction factor for the TPAC gravimetric method would not seem worthwhile. Also, it is felt that the analytically determined
value using the Nitron procedure is better than the empirically corrected value. LITERATURE CITED
(1) Affsprung, H. E., Archer, T7. S., A y . 4 ~ . CHEM.35, 1912 (1963). (2) Coursier, J., Hure, J., Platzer, R., Anal. ('him. Acta 13, 3T9 (1955). (3) Lange, W.: X e r . 59A, 2107 (1926). (4) Schaack, H. J., Wagner, W., Z. Anal. Chem. 146, 326 (1955). H. E. AFFSPRTTNG V. S.ARCHER' Department of Chemistry The University of Oklahoma Xorman, Okla.
' Present address, Department of Chemistry, University of Wyoming, Laramie, Wyo. WORKsupported in part by the Sational Science Foundation.
Amine Extraction-Spectrographic Determination of Tantalum, Titanium, Tungsten, and Zirconium in Plutonium Sir: Trace concentrations of tantalum in plutonium have been determined by amine extraction-spectrogra1,hic analysis ( 2 ) . This paper describes an extension of that procedure to include the determination of tantalum, titanium, tungsten, and Zirconium. EXPERIMENTAL
The apparatus, reagents, materials, and procedure used were the same as those used previously (2). The only exceptions were the use of a 20% solution of tri-n-octylamine (TnOA) in xylene instead of 50y0 and 6JI HNOs instead of 4 X . The 20y0 solution with 6M H N 0 3 gave plutonium extraction efficiencies greater than 99% in two contactings a t the 10-gram-per-liter level. RESULTS AND DISCUSSION
Plutonium is dissolved in a minimum amount of HC1 and immediately ex-
Table
I.
Effect of Fluoride on TnOA Extraction
70Recoveryo Fluoride
M
Aqueous P h E - - -
Ta
0 0 100 0.001 114 0.01 94 0.1 37 1.0 0 Obtained with amine phase.
Ti
W
Zr
Organic phase Pu
98 96 110 95 75 104 110 96 92 80 81 94 99 94 101 60 97 88 110 30 one contacting of the
tracted into 20% TnOA after adding HN03. Some HCl (no greater than 0.5M) is therefore present during the extraction; concentrations up to l M l however, still produced quantitative recoveries of tantalum, titanium, tungsten] and zirconium. The effect of fluoride on the extraction was studied. Results are shown in Table I. Tantalum extracted in the presence of fluoride, but, even with 1M fluoride] titanium, tungsten, and zirconium did not. Plutonium extraction decreased with an increase in fluoride concentration. The method is based on the assumption that plutonium can be dissolved and extracted without loss of the analytical elements whether they are dissolved or not. The validity of the method is proved if the analytical elementq in solution are shown not to extract and if insoluble forms of those elements are recovered quantitatively in the aqueous phase. The data of Table I show that the ions in solution are not extracted. To test the insoluble forms, the elements were added as insoluble oxides to the aqueous phase and analyzed gravimetrically after the extraction. Excellent recoveries were obtained. The data are shown in Table 11. In addition, spectrographic analysis of the organic phase revealed less than 1 pg. of the added elements. The organic phase was evaporated and ignited a t 650' C. in the presence of germanium dioxide which was then transferred to a crater electrode and burned to completion in a direct current arc.
Table I11 lists the wavelengths of the lines used, their excitation potentials ( I ) , and boiling points ( 3 ) . Siobium whose boiling point and excitation potential are close to those of the analytical elements was chosen as the internal standard.
Table
II.
Recovery of Insoluble Oxides through TnOA Extraction
Added,
Found,
mg.
mg.
Oxide TaL%
Recovery, L7
/G
5 2 5 0 96 2 12 7 12 2 98 8 TiOn 4 6 4 8 104 19 3 19 7 102 ZrOt 8 2 8 1 98 1 15 8 15 5 98 6 \VOsa 10 1 10 4 103 28 5 98 6 28 9 Ignition after the extraction was made in a muffle furnace kept below 700" C.
Table 111.
Element Ta Ti
If'
Zr Nb
Spectrographic Data
WaveWavelength, length, A.
3012 3361 2946 3391 3094
54 21 98 98 18
Excitapotentiori tion potential. tial, e.v. >3 7
io
F,
>5 3 10 7 >8 0
VOL. 36, NO. 13, DECEMBER 1964
Boiling Boiling mint. point, "C. . "C 5425
x- -x_n_ 5930 3580 4927
2513
