ce-iuiii. However, no brines were found that contained cesium without rubidium. ACKNOWLEDGMENT
The writer gratefu1.y acknowledges t'he cooperation and assistance of the following Bureau of Mines employees: Cjmthia A. Pearson and Cathy J. Cowden, who aided in ,;he ion exchange qeparations; F. E. Arrnatrong, Gordon I:. Fletcher, and Jerry R. Xbranis, mho advised and aided in t'he radiochemical work. LITERATURE CITED
i1 ) 13(1rovik-Raniaiiova, F., 2'r. Bzogeokhiin. Lab., .-1kad. S n ~ kS S S R 8 , 145 (1946).
(~, 3 ) Collins, A. G.j c'. S. Bur. .IIitces, Rept. Invest. 6047 6 0 4 j (1962). (4) Compston, \V., Jeffery, IT., Ann. N. Y.d c a d . Sei. 91,185 (1961). ~~
~~
(5) Dean, K. C., Sichols, I. L., c'. S. Bur. Mines, Repf. Incest. 5 6 i 5 (1960). (6) Finston, H. I,., Kinsley, 11. T., .\-at(. Acad. sei., S u c l . S'ci. Ser. 3035 (1961).
(7) Fix, R. \Y.>Irvine, J. X., Jr., .\fuss. lnst. P'echnol., L a b . .Yiicl. Sei., Ann. Progr. Re@., June 1, 1 9 j 5 to May 31, 1956. ( 8 ) Gast, P. lY.>=Inn. S. I'. A C C JSci. ~. 91, 181 (1,961). (9) Glendening, B. I,., Parrish, D. B., Schrenk, IV. G., hs.i~.CHEM. 27, 1554 (1955). (10) Nara, T., Bull. Inst. Chem. Xes., Kyoto GniuPrsity 27, 139 (1959). (11) Ishibashi, Fujinaga, T., Iioyania, J . , Saito, T., Buirseki Kuyaku 10, 116 (1961). ( 1 2 ) Kick, H., 2. P$unzenc.rnuhr. D..; I n a h s t
80, 37 (1955). (18) Pnides, A. .4., Rebster, R. K., Geochznz. Cosmochzii~. d c t a 1 1 , 139 (1957). (19) Smit, J. Van R., Robh, \T., Jacobs, J. J , J . Inorg. Sucl. Chem. 12, 104 (1959). (20) Tal-lor, J. lI., rlEC Res Dezel. Rept. HT17-45964,1956. (21) Z y s z c z j nska-Florim, B., Chomik, T.,
Roczntki Pnmtwowego Zakladu 10, 87 (1959).
Hig.
RLCEIVED for review Februarv 13, 1963. hcc
3
Cr -8
c u -?
3 3
Fe-' Fe-'
3
K +'
La
+ J
LiT1 ;\Ig - 2 ?;a +1 K d+ A 1-1+ * Pb ?' Pr - d Pu T 4
Sm - 3 TO, +l Zn + 2 Zr + 4
3 3 3
3 :3 '3 J
3 :i
5 3 0
:1 3 3
mg. 40 2 20 1 40.2 40 9
1%
45 1
0 -0 0 +IO -0 +4
20 0
+o
40 1
0 1 0 6 1 9
Destroys Indicator
22 1 21 5 31.3 33 0 40 I 20 2 20 2 40 2 40 2 40.2 20.3 51.9 40.7 20.2 23.1 20.4 40.2 51.1 21.4
1 +2 I 1 ' 3 '11 1 +12 8 -0 1 0 0 0 0 0 0 0 0 0.0
-0.1 rll.,
+10.4 0.0 +2.9 +0.2
+o.o
+10.9 +1.2
mg. 40 1 20.1 40.1 30 3 40.3 40 3
mg -0 1 -0 1 -0 1 0 0 -0 1 $0 1
20.0 20.3 20 2 20.1 20.2 40.1 20.2 20 2 40 2 40 2 40 2 20 1 40 1 30 2 20 2 23.0 20.1 40.2 40.2 22.0
+0 1
Analyses performed in triplicate. Hydroxylamine hydrochloride, 0.5 gram, added prior t o direct titration.
1262
ANALYTICAL CHEMISTRY
:
PH
Accuracy a n d Precision. Tj-pica1 results obtained from titration of thorium standards are shown in Table I. These d a t a indicate t h a t from 1- to 50-mg. quantities of thorium can be determined by tlie
1.0 2,o 10 0 19.9 29.9
1
-to
0 -0 0 -0 0 0 0 0 0 -0 -0 -0 0
1
0
1
0 1 0 0 0 0 0 1 1 1
0
A2 8 -0 1
-0 0 0 0 +l 6
the direct and the indirect procedures. The results of this study are summarized in Table 11. Cations which cause a mean error greater than twice the standard deviation of the method are considered interferences. Bismuth, cadmium, chromium (II I) , cerium(1V) , copper, cobalt (11),iron(II1) nickel, lead, plutonium, zinc, and zirconium(1V) ions cotitrated when the direct titration was performed a t room temperature. -4lthough in boiling solution aluminum reacts rapidly Fvith EDTA at pH 3.0, it does not cotitrate when the titration is performed at room temperature. Of the cations which cotitrate in the direct titration, only plutonium, zirconium, and cerium(1V) react with fluoride ions to release EDTA and thus interfere Kith the indirect determination. Prior to the direct titration, hydroxylamine hydrochloride is added to reduce cerium(1V) to cerium(II1) which does not interfere with the method. rlcetate, chloride, nitrate, and sulfate ions do not interfere. Fluoride ions in the >ample must be expelled prior to the direct titration. Phosphate ions react nith thorium and interfere with the direct and the indirect determinations. Effect of pH. T h e stability of metal-EDTA complexes is a n inverse function of acidity (18'). Therefore, the number of interfering cations is reduced by titrating a t the minimum pH where the thorium and the copper complexes are stoichiometric. Fritz and Ford (12) found that the Th-EDT.4 complcx was completely formed a t pH 2.3 but that thorium hydrovide began to precipitate at pH 3.5, The sharpest thorium-xylenol orange end point was observed between pH 2.8 and 3.5. The Cu-EDTA complex is stoichiometrically formed at pH 2.7 as shown in Figure 1. Standard EDTA solutions, buffered between pH 1.9 and 3.5, were heated to boiling and titrated with standard copper solution to the PAN end point. In the p H range between 2.8 and 3.5 the PAWend point was rapid and sharp. Selection of Indicators. Visual metyl-dye indicators are frequently used for end point detection in EDTA titrations (2-6). Seven metal indicators were investigated for use in the direct and indirect titrations; xylenol orange. pyroratechol violet, alizarin red S, thoron, PAS, Cu-PAS, and arsenazo. Xylenol orange and arsenazo (3,2arsonophenylazo - 4,5 - dihydroxy - 2.7 naphthalene disulfonic acid) were found to be equally suitable for end point detection in the direct titration. Only P.4K reacted properly as an indicator for the indirect titration. Because reactivity of the PAN indicator complex is sluggish a t room temperature, the in-
I
i_;_
LITERATURE CITED
I
n
100
-
90
-
-
w 60
D:
W 0
2
40 30
-
20
IO
I
I
I
I
(1) Banks, C. V., Proc. U . A'. Intern. Conf. Peaceful Uses At. Energy, 2nd Geneva, AIConf. 28, 918 (1958). (2) Barnard, A. J., J r . , Broad, W. C., Flaschka, H., Chemtst Analyst 45, 86
(1956). (3) Ibzd., p. 111.
( 4 ) Ibid., 46, 18 (1957). ( 5 ) Zbid., p. 46.
(6) Brown, W. B., Rogers, D. R,., Mershad, E. A., Amos, W. R., AXAL. CHEM.35, 1000 (1963). ( 7 ) Buddhaver, S., Anal. Chem. 4 c t a 19, 551 (1958). (8) Cabell, M.J., Analyst 1952, 859. (9) Datta, S. K., Z . Anal. Chem. 148, 267 (1955). (10) Flaschka, H., Abdine, H., ( " h ~ n i i s t
ACKNOWLEDGMENT
25, 1640 (1953). (13) Fritz, J. S., Oliver, R. T., Pietrzyk, D. J., Zbid., 30, 1111 (1958). (14) Haar, K. ter., ilnalyst 77, 559 (1952). (15) Levine, H., Grimaldi, F. S., U. S. Atomic Energy Comm. Rept. AECD3186 (1940). (16) Peshkova, V. M., Gromova, M. I., Slexsandrova, K,AI.. Zh. Anal. Khzm. 17, 218 (1962). (17) Pribil, R., Koros, E., ilfagyar Kern. Folyoirate 64, 55 (1958). (18) Welcher, F. J., "The Analytical Wae of Ethylenediaminetetraacetic Acid," Van Sostrand, New York, (19.57).
The authors gratefully acknowledge the assistance of R. L. Deaton and E. 4. Mershad.
R~~~~~~~ for revien- April 19, 1963. hccepted May 20, 1963.
~
direct titrations must 3e performed in hot solutions (11). Fluoride Demasking. Fluoride masking is commonly used t o eliminate t h e interference of aluminum, zirconium, a n d thorium with direct EDTA titrations. In t h e indirect determination of thorium, ammonium fluoride is used as a dtmasking agent as represented by t h e reaction: Th(EDTA)
n ere treated
with various amount> of ammonium fluoride. The solutions mere heated to boiling and titrated with a standard copper solution to the PSN end point. The results of this study, summarized in Figure 2, indicate that the mole ratio of fluoride to thorium must exceed 10 before the demasking reaction is complete.
+ 4F- F?ThFI + (EDTA)-4
To dotermine the amount of fluoride necessary to demask E D T A stoichiometrically from the Th-EDTA compie.;, standard Th-EDTA solutions
Activation Analysis for Sodium in the Sodium Tungsten Bronzes ROBERT J. REULAND' cind ADOLF F. VOIGT Institute for Atomic Resecirch and Departmenf of Chemistry, Iowa State University, Ames, Iowa
b
The neutron activation method has been applied to the ssdium analysis of the sodium tungsten bronzes. The main obstacle was the large Wls5activity which was simulianeously produced with the NaZ4activity and which interfered with the ccunting of the latter. Destructive activation analyses were investigated in which the two activities were radiochemically separated in reactions of the bronzes with either nitrosyl chloride or bromine trifluoride. Several types of measurements b y nondestructive testing were also tried, and one o f fhese, in which the two Nos4gamma rays were counted in coincidence in a well crystal, was found to have sufficisent precision. The accuracyof the newtron activation
method was established b y analyzing cubic bronzes for which the sodium concentrations were accurately known from x-ray analysis.
s
discovery by Woh!er (6) in 1823, the sodium tungsten bronzes have been the object of many scientific investigations. Their electrical properties have received particular attention, especially in the last decade or so. However, most inveqtigstions of their physical properties have been restricted to those bronzes which crystallize in cubic symmetry (z in Na,WO3>O.4). This restriction has been dictated by the lack of a suitable method for determining the sodium IKCE THEIR
concentration of the noncubic bronzes. I n the cubic range, the 2 value can be accurately evaluated from x-ray powder photographs, according to Brown and Banks ( 1 ) . However, in the noncubic range, it has not been possible to establish a relationship betn.een the lattice contraction and the z value. Chemical analyses of the sodium tungsten bronzes are, at best, troublesome because of the difficulty of bringing the bronzes into soluble form. Thus, although interesting physical phenomena have been observed and are anticipated in this noncubic range of the bronzes, their interpretation in terms of the Present address, Texas Instruments, Inc., Dallae 22, Texas. VOL. 35, NO. 9, AUGUST 1963
1263
