EXCHANGE OF TANTALUM IN SOME HF-HC1 MIXTURES
Jan., 1951
13
great difference in anion exchange behavior of niobium and tantalum.2~1s~1* I n species I11 the oxide ion has probably been replaced by fluoride ions. This would make plausible the great dewhere D Ois the observed distribution coefficient, crease in K s with decreasing HC1 concentration D1,D2 and D3 those of the "pure" species and Tr and the decrease in E as species I11 is formed and T the concentrations of niobium in the resin since it would give a mechanism for a decrease in and solution, respectively, setting (HF) = j negative charge on addition of fluoride ions. and combining equations (13), (14) and (13) Acknowledgment.-It is a pleasure to acone obtains knowledge the valuable technical assistance of D O (DI DpK12.f~f D3KIZK23f"+"')/(l f Ki2.f" Mrs. Hazel Templeton and to thank Messrs. K12Kza.f~~~') (16) J . East, F. W. Manning, P. P. Williams and t h e In the limits, i. e., when the two reactions do not Instrument maintenance group under R. E. Toucey for the assembly and the maintenance of overlap, equation (16) reduces to the electronic equipment, Mr. F. King for the Do = (Dl D2K12f")l(l K12P) construction of the automatic scanner, and Dr. and G, E. Boyd for many valuable discussions. Do = ( 0 2 D3Kz3fn')/(l K ~ 3 . f ~ ' ) (17) Summary HC1 data could not be fitted to equaThe 9 1. The behavior of zirconium(1V) and niotion (16) taking n = l and n' = l. Satisfactory agreement was obtained using n = n' = 2 as bium(V) on the anion exchange resin Dowex-1 shown by the solid line Fig. 4 which represents was studied in a number of HF-HC1 mixtures, 2 . Separation of the two elements is excellent the calculated values. The constants D L = 413, D2 = 1.0,D3 = 60, K 1 2 = 1.3 X I O 4 and under a number of conditions. Although zirconium is usually eluted first, the elements can be = 1.23 were evaluated by trial and error. They can only be considered rough approxima- eluted in reverse order under some conditions. 3. Attempts have been made to interpret the tions in view of the limited number of data available. An analogous calculation for the 3 M data in terms of ionic species and their equilibria. HC1 data was not attempted since the slight In the case of niobium a t least three species were increase in E a t very high H F concentration observed in 9 M HC1 differing by two fluoride suggests the formation of a fourth species. How- ions each. The first two species, existing a t low ever, i t is apparent that K23 must be a t least a fluoride concentration, are probably oxygenated. factor of 10 smaller in 3 M HC1 than in 9 M (18) In ref. (2) this difference was attributed to a difference in HCl. Since niobium is known to form oxygenated charge between the niobium and tantalum complexes and it was that the more strongly adsorbed tantalum carries a greater ions (of the type NbOX,+3-n) l7 i t appears reason- assumed negative charge. This was equivalent to the assumption that able to assume that species I and I1 contain one the cross-over point P would occur at chloride concentrations so coordinated oxide ion. This would explain the high as to be practically unattainable in aqueous solutions. As
Defining
+
+ +
+
+
(17) A. F Wells, "Structural Inorganic Chemistry," Clarendon Press, Oxford, 1945, p. 424.
pointed out above, this assumption now appears very unlikely.
OAKRIDGE,TENN.
RECEIVED MAY15, 1950
-
[CONTRIBUTION FROM
THE
OAK RIDGENATIONAL LABORATORY, CHEMISTRY DIVISION]
Anion Exchange Studies. 11. Tantalum in Some HF-HC1 Mixtures1 BY KURTA. KRAUSAND GEORGE E. MOORE I n the previous paper2 results on the anion exchange behavior of niobium and zirconium in HC1-HF mixtures were given. This paper will deal with a similar study of tantalum and the subsequent one will deal with protactinium and a general discussion of the separation of the triad niobium, tantalum and p r o t a ~ t i n i u m . ~ Experimental Details of the general experimental procedure were given earlier.2 Suffice i t t o repeat that the studies were carried out with Dowex-1 columns of ca. 0.023 sq. cm. cross-section a t 25 * lo. (1) This document is based on work performed for the Atomic Energy Commission at Oak Ridge National Laboratory. (2) K. A. Kraus and G. E. Moore, THIS JOURNAL, 78, 9 (1951). (3) For a preliminary communication on the separation of niobium and tantalum see K. A. Kraus and G. E. Moore, i b i d . , 71, 3855
(1949).
Talg2tracer (0-emitter, TI,%= 117 d.)4 was used, obtained by slow neutron bombardment of spectroscopically pure tantalum metal. Identity of the tracer was checked by standard radiochemical techniques. Elution rates were determined by monitoring the effluent and by direct scanning of the columns. Results and Discussion The results of the experiments are summarized in Table I where the molarities of HC1 and HF of the eluents are given and the observed values of the elution constant ET^ defined2as ET^ = d A / V (1) where d is the distance (cm.) the band maximum moves after passage of V ml. of eluent through a (4) Information from "Table of Isotopes," by G. T. Seaborg and I. Perlrnan, Rev. M o d . Phys., 20, 585 (1948).
VOl. 73
KuRr A. KRAUSAND GEORGEIs. l l o t , ~ ~ :
14
column of cross-sectional area A sq. cin. In the last column of Table I are given calculated values of the formal first order elution constant E $ . a defined as EB = ET,/(CI-)
(2)
(parentheses indicate molar concentrations). TABLE I TAXTALUBI I N IIC1-IIF &1IXl’URt8 Acetone was taken as the difference between the formaldehyde and total carbonyl contents, the latter being determined by the procedure of Mitchell, et aZ.9 Water was determined with the Karl Fischer reagent according t o the procedure of Bryant, at d . 1 ° Because of the large number of components in the reaction product, the analysis for water was carried out preferably on the condensate from a duplicate run. The product was condensed directly into the reagent solution held in a collection trap a t liquid nitrogen temperature, and a second portion of the reagent, handled in a similar manner except for exposure t o reaction product, was used as a blank. Free acid was titrated directly and assumed to be formic.
.
Di-t-butyl Peroxide and Oxygen.-The reaction of oxygen and free methyl radicals, the latter (4) Elving and Warshowsky, I n d . Eng. Chcm , Ann1 Ed , 19 1fIl)ci (1947). (5) Skrabal, 2. Anal. Chcm., 119, 222 (1940). (6) Fischer and Schmidt, Bcr., 60, 679 (1926). (7) MacFadyen, J . Biol. Chem., 168, 107 (1945). (8) Bricker and Johnson, Ind. Eng. Chcm., Anal. E d , 17, 400 (1945). (9) Mitchell, Smith and Bryant, THISJOURNAL, 63, 573 i 1 4 1 1). (10) Bryant, Mitchell and Smith, ibid , 62, 3504 (1940).
