NOTES
Sept., 1951 and were removed by filtration, yield 24 mg. The product was obtained in almost quantitative yield in a second experiment in which the reaction mixture was cooled after the oxidation had gane to CompIeticm. After drying in vacuum, the crystals melted, not sharply, at about 135-145' and gave a a a b w in a m a t with the dihydrate of the expected oxidation product. A n d Wed. for C d i & . W & (316.3): C, 53.16; W, 6.37. Found: C, 62.56, 52.68; H, 6.38, 6.26. The crystals were insoluble in cold alcohol, cold acetone and hot or cold chloroform. Recrystallization did not occur from warm alcohol, but occurred slowly when water was added t o the solution obtained by boiling with acetone. NATIONAL BUREAUOF STANDARDS~~ WASHINGTON 25, D. C. AND %UTHERN REGIONAL RESEARCH LABORATORY l4 NEW ORLEANS19, LOUISIANARECEIVED FEBRUARY 2, 1951
4487
and 2 above. It seems reasonable, although this has not been proven, that the Itnitrite!J and isulfit&'radicals in the complexes are joined by NS bonds. The formation of so4- from hydroxylamine disulfonate, for example, may therefore be considered to take place in the following way. i
H
o-d,': > BaR2it follows that ~ B ~ R ,= ) the mole fraction mBaRJ(muorR, rnBoRJmuoaI, where m represents the moles of each cation in the resin phase. The concentration exchange constant, K,,., is defined as
+
L. = ( ~ B ~ R S ()~ ~ U O ~ H ) / ( ~ U O , R * ( ~ B ~ + +(3) ) whence
-& .&x. (Y’UOI(N~OO~)~/Y+B~(NO~):’ (4 where y represents the mean activity coefficients About 1931 it occurred to Vanselow that cation of the ions of the specified electrolytes. It follows exchange reactions could be utilized for investigation of activity coefficients in mixed electro- from equation (4) that l y t e ~ . The ~ method was applied experimentally to Y ~ B ~ w o ~ )= : (L./&)‘/I X Y*UOnWOr)a (5) the barium-cadmium exchange reaction with ben- The thermodynamic constant, K8, is obtained by a tonite. Fair agreement between experimental and plot of the experimentally determined values of K e x calculated activity coefficients was found. In pa- against some function of electrolyte concentration per I of this seriesI4it was suggested that Vanse- and extrapolating to infinite dilution. The activity low’s approach could be applied even more success- coefficients of uranyl nitrate are exactly those of its fully in conjunction with the synthetic organic cat- aqueous solution. Therefore, the only unknown in ion exchangers and carrier-free radiotracers. The equation ( 5 ) is the activity coefficient of the barium potentialities of this technique for elucidating the salt. role of trace metals in biological systems are of parExperimental ticular interest. This communication presents the Ten-ml. volumes of uranyl nitrate solutions (PH varied results of measurements on the activity coefficients from 1.9-2.4 containing carrier-free ‘QBa were added to of carrier-free I4OBa++in uranyl nitrate solutions by weighed samples (0.05-0.5 g.) of the uranyl saturated form of Amberlite IR-1 (Rohm and Haas Co., Philadelphia, Pa.). the use of uranyl form of the cation exchange resin, The mixtures were shaken until the absorption of ‘MBa Amberlite IR-1. reached a constant value. Assay for ‘QBa was made by The equilibrium reaction between tracer Ba and precipitating the tracer with added barium chloride carrier and counting the radioactivity of the mounted precipitate the cation exchanger is BY JACK
Ba”+
+ UOsRz
SCHUBERT’
BaRz
+ UOnC+
E
(1)
i n which R is the insoluble anionic part of the ex-
_
_
JF Fig. 1. ~
(1) This investigation was performed under the auspices of the Manh a t t a n District at t h e Clinton Laboratories during t h e period December, 1944, to January, 1945, Oak Ridge, Tenn , a n d reported in CN1873 aud CN-2563 in Januirr), l W j , and February, 1945, respectively. ( 3 ) Argonne National Laboratory, 1’. 0 . 130s 5207, Chicago 80, Illinois. (3) A. 1’. Yanselow, Trirs J ~ J C K E I A I . , 64, 1307 (l9:32). J. Schubrrt, J . P h y s . Colloid f / i c ? i f . , 62, :HO f10-183.
with an end-mica window G. M. counter tube. All of the radioactive measurements were made on a strictly relative basis, thus minimizing errors due to decay, self-absorption, scattering, etc. The U02R2 contained 1.19 millimoles of UOef+ per gram of oven-dried resin. The air-dried resin, 60-80 mesh, contained 15.5% moisture. The concentrations of uranyl nitrate in solution a t equilibrium were determined gravimetrically by ignition of measured aliquots to UaOs.
Results and Discussion The experimental and derived data are summarized in Table I. The value of Ka = 14 was obtained from a plot of log &=, versus d m and an extrapolation to infinite dilution. We can arrive independently at an approximate value of K , by in serting in equation (4) the known activity cocacient of barium nitrate in a dilute binary solution of the same ionic strength. This procedure for p = 0.03 givesKa = 15. The y f of B;t(NO& in tlie ternary solution is greater than its value in the binary solution. This effect is similar to that found by Harned’ for strong acids. The accuracy of the ion exchange method for measuring activity c d c i e n t s in mixed electrolytes can be improved by the use of monofunctional ex( 5 ) A P Vanselow, Soil Sci , 53, 95 (1932). JOURNAL, 69, (6) G E. Boyd, J Schubcrt and A W Adamson, THIS 2818 (1947). (71 €I S Harned and B B Owen, “The Physical Chemistry of I:lertrolytic Solutions,” Rcinliold Pub1 Corp.. New York, N Y , 1843, p t33
