and discordant results are obtained.
A similar effect has also been observed when ferrous bromide is added to the ferrous chloride solution (Table I). Therefore, the hydrobromic acid is put directly into the reduction flask. Some of the results obtained for the analyzed samples of nitrocellulose and nitrocellulose propellants are given in Table 11. They have been compared with the results obtained by the Desrarda and the nitrometric methods. The results are reproducible within = t O . O Z ~ oof the nitrogen content of the samples and are evidently in agreement with those obtained by the Devarda and the nitrometric methods. The proposed procedure is as convenient as the original ferrous-titanous titration procedure of Shaefer and Becker and seems to be generally applicable for the determination of the nitrogen content of
nitrocellulose and nitrocellulose propellants. ACKNOWLEDGMENT
The author wishes to acknowledge the assistance of Lena Herzog, who carried out much of the experimental work. This paper is published with the kind permission of the General Director of the Israeli Military Industries. LITERATURE CITED
w.IT7., IND.EKG.C m x , ANAL.ED.5 , 152-4 (1933). (2) Becker, W. W., Shaefer, W. E., “Organic Analysis,” Vol. 11, p. 97, (1) Becker,
Interscience, New York, 1954. (3) Brissaud, L., Tranchant, J., Xdm. poudres 36, 315-21 (1954). (4) English, F. L., J.Znd. Eng. Chem. 12, 994-7 11920).
(5) Fleury,
G., Jourdin, P., Mdm. poudres 27, 179-81 (1937). (6) Grodzinski, J., Berkowicz, M., “Determination of the Nitrogen Content of Propellants by the Nitro-
metric Method,” unpublished report, April, 1952. (7) Knecht, E., Hibbert, E., “Xew Reduction Methods in Volumetric Analysis,” 2nd ed., p. 26, Longmans, Green, London, 1925. (8) Liogier, H., Mdm. pozidres 36, 309-13 11954). Liogier,”., Dalbert, R., Tranchant, J., Ihid., 37, 466-8 (1955). Muraour, H., Ihid., 23,250-5 (1928). Parpaillon, N., Ibid., 34, 419-20 (1952). Pitman,’ J. R., J . SOC.Chem. Ind. (London) 2 9 , 982-6 (1900). Shaefer, W.E., Becker, W.W., ANAL, CHEnf. 2 5 , 1226-31 (1953). Tranchant, J., XXVIIth International Congress, Bruxelles, 1954. RECEIVED for review June 11, 1956. Accepted October 1, 1956.
FiItra tion-Precipitation Separation of Barium-140 from Lanthanum-I 40 R. W. PERKINS General Electric Co., Richland, Wash.
b A rapid method i s described for obtaining a continual supply of carrierfree barium- 140. Purified 12.8-day barium- 140 i s soon contaminated by growth of its 40-hour lanthanum-140 daughter. A method was developed for periodically removing lanthanum140 from the barium-1 4 0 by filtering the solution through an anion exchange bed in the free-base form. The lanthanum-140 i s precipitated on the resin and the barium-140 passes through in the effluent. The barium140 was shown to be radiochemically pure by decay and daughter growth rate measurements. The lanthanum140 can be removed from the anion exchange bed by acid elution. Its radiochemical purity was established by decay measurements.
140 mill reach about 1.5% 1 hour after purification. Numerous methods have been used for the separation of barium-140 and lanthanum-140, including formation of lanthanum-140 as a radiocolloid in basic solution followed by filtration 19), ion exchange (1, 2, 7), paper chromatography ( d ) , and precipitation (6) ; however, it was found that filtration of a barium-140-lanthanum-140 solution through a n anion [OH-] column for removal of the lanthanum-140 was a
more rapid and convenient means of obtaining carrier-free barium-140. This separation differs from the lanthanum140 radiocolloid filtration method (9) in that it involves the precipitation of lanthanum-140 on the surface of a resin rather than the filtration of a lanthanum-140 radiocolloid. A barium-140 solution can be repurified by this method as often as necessary to keep the lanthanum-140 below a n interfering level. The lanthanum-140 precipitated on the column may be re-
I
radioisotopic tracer studies, a constant supply of the radiochemically pure isotope is required. I n the case of 12.8-day barium-140 which has a 40-hour lanthanum-140 daughter, it is necessary to have a rapid method of purification, or the lanthanum-140 mill reach a significant concentration before any tracer studies can be made. The p activity of lanthanum-140 in purified bariumpr’ CARRYING OUT
152
ANALYTICAL CHEMISTRY
3 EFFLUENT
Figure 1.
VOLUME,
ML.
Elution of barium-1 40 with water
Column, 4 X 200 mm.; OH--charged Dowex 1 ( 8 % cross linked; 100 to 200 mesh, Lot 3562-18)
same column. For this second filtration and all succeeding filtrations, the solution should be passed through the column twice. This removes any lanthanum-140 which may have formed near the bottom of the column by decay of residual barium-140 and was carried through with the first filtrate. By this Drocedure a column can be used indefi;litel?.. To allow an estimate of the yield for the filtration a 0.050-ml. aliauot of barium-140 was placed on the t i p of an anion [OH-] resin bed, and an elution, with water, was performed. The elution curve obtained, with markers a t 90 and 98yo elution, is shomm in Figure 1. The lanthanum-140 precipitated on the anion resin bed can be removed in a radiochemically pure state. After allowing a barium-140-lanthanum-140 solution to filter through the resin bed, elute the remaining barium-140 by passing 100 rnl. of \\-ater through the column. Dissolve the lanthanum from the anion exchange bed by passing 10 ml. of 6N nitric acid through the column. If gas bubbles form in the resin during the acid elution they may be removed by stirring the resin with a stainless steel wire of small diameter. The effluent contains pure lanthanum-140.
moved for tracer studies by elution with dilute nitric acid. The radiochemical purity of the barium-140 obtained by this method could not be accurately determined by conventional absorption techniques because of the similar beta spectra of radioactive barium and lanthanum. The purity was therefore established by decay and daughter growth rate measurements, and the absence of lanthanum-140 ]vas confirmed by ycounting. REAGENTS
The barium-140 was obtained from the radioisotopes division of Oak Ridge National Laboratory. Decay measurements on the barium-140-lanthanum140 equilibrium mixture indicated no measurable radioisotope contaminants. The column was 4 X 200 mm. and had an exchange capacity of about 3 meq. The ion exchange resin used was Dowex 1 (870 cross linkage 100 to 200 mesh, Lot 3562-13) activated by three alternate washings with IN hydrochloric acid and water. The resin was hydroxyl ion-charged by passing 20 ml. of 1 N sodium hydroxide through t h e packed column followed by water until the effluent was neutral to p H indicator paper.
BARIUM-1 40 AND LANTHANUM-1 40 PURITY
-411 p-counting rate measurements were made on standard mica-window Geiger-Muller counters. Decay-growth measurements were made on aliquots of barium-140 after each of several repurifications. These decay-growth curves were compared with the theoretical curve for barium-140 to determine radiochemical purity. The theoretical curve was calculated using the exponential equation for relating parent daughter growth ( 5 ) and the standard barium140 and lanthanum-140 fl-counting rate correction factors of 1 to 1.04 (IO). I n Figure 2 a decay-growth
EXPERIMENTAL
A 5- to IO-ml. aliquot of barium-140 solution, containing some lanthanum140, which is less than 0.01N in hydrochloric acid is allowed to pass slowly through an anion [OH-] resin bed. The effluent contains radiochemically pure barium-140 and may be used directly for tracer experiments. About 1 hour after purification the beta activity due to lanthanum-140 becomes significant (about 1.574 and may be removed by refiltering the solution through the
l.5t
1.6
a
2 C
1
measurement for a typical purified barium-140 sample is compared with the theoretical curve. A high radiochemical purity is indicated. The lanthanum-140 activity of the purified barium-140 was shown to be less than 0.5% by y-ray measurements a t the lanthanum-140 photopeak (1.56 m.e.v.) on a scintillation y-ray spectrometer. The lanthanum-140, separated from the resin bed by acid elution, was shown to be radiochemically pure by decay measurements over a period of five half lives. DISCUSSION
Carrier-free barium-140 can be rapidly separated from its daughter lanthanum140 by filtering their solution through a n anion [OH-] column, the lanthanum-140 being precipitated on the resin. The separation requires about 10 minutes and the barium-140 may be repurified on the same column an indefinite number of times. Carrier-free lanthanum-140 can be removed from the column by elution with dilute nitric acid. Filtration-precipitation separations of this type should be applicable to many carrier-free separations. Preliminary studies indicate that complete separations of yttrium40 from strontium-90 on anion [OH-] columns, and strontium-89 from barium-140 on anion [Cr04--] columns can be obtained. Since the preparation of this paper, a similar analytical separation of strontium-90 from yttrium-90 has been described (3, 8). LITERATURE CITED
W.E., Parker, G. IT., Tompkine, E. R., h’ucleonics 3 (NO.5),
(1) Cohn,
22-23 (1948). ( 2 ) Coryell, C. D., Irvine, J. W.,Jr., RI. I. T. Laboratorv of Kuclear
Sciences and Engineering, Kuclear Chemistry (Inorganic) Group, Progress Rept. NP-1777, 58 (July 1950) (unclassified). Finston, H. L., Miskel, John, Ann. Rev. Suclear Sei. 5, 274 (1955). Fouarge, J., Anal. China. Acta 12, 231-8 (1955).
Friedlander, G., Kennedy, J. W., “Introduction to Radiochemistry,” p. 109, Wiley, Kew Tork, 1949. Kirby, H. W., Salutsky, SI.L., Phys.
,..I-
Rev. 93, 1051 (1954).
Kruger, P., Coryell, C. D., J. Chem. Educ. 32, 280-4 (1955). Samos, G., Finston, H. L., Brookhaven National Laboratory, unpublished xork. Schn-eitzer, G. K., Jackson, W. M., J. A m . Chem. SOC. 74. 4178-80 (1952).
T I M E
Figure 2. 0
I N
H O U R S
Theoretical decay-growth curve for barium-1 40
Decay-growth measurements for a typical barium-1 40 sample
SchFendiman, L. C., General Electric Co., Richland, Wash., “Stand,; ard Practices Counting Manual, HW-30492 (revised April 2, 1956). RECEIVED for review August 15,1955. ACcepted June 21, 1956. VOL. 29, NO. 1 , JANUARY 1957
153
