LITERATURE CITED
( 1 ) ilrterburn, J. O.:,Bastian, B., "GETR Neutron Fluxes, General Electric, Atomic Power Ilivision, San Jose, Calif., March 1963, (unpublished). ( 2 ) Benson, P. A,, Gleit, C. E., ANAL. CIIEM. 35, 1029 (1963). (3) Cadle, R . I)., Thuman, W. C., Ind. Eng. Chem. 52,315 (1960). (4) Coryell, C. I)., Chase, J. W.,Winchester, J. W., J . Geophys. Res. 68, 559 (1962). (, 5,) Fukai. 11.. Xeinke, W. Vir.- Suture 184, 815 (1959). (6) Gleit. C. E., Holland, W. D., ANAL. CHEM.34, 1454 (1962).
( 7 ) Goldberg, E . D., Brown, H. S., Ibid., 22, 308 (1950). (8) Grand, J. A., J . Phys. Chem. 63, 1192 (18.5R) \----,-
(9) Haskin, L., Gehl, AT. A . , J . Geophys. Res. 67,2537 (1962). (10) Kant, A . , Cali, J. P., Thompson, H. I)., ANAL.CHEM.28, 1867 (1956). (11) Katcoff, S., ,Vucleonics 18, N o . 10, 201 (1960). (12) Leddicotte, G. W., ~ ~ K ACHEW. L . 34, 144R (1962). (13) Leddicotte, G. W., O.R.X.L. hIaster Analytical Alanual, U. d. Atomic Rept. TID-7015 Energy Comm. (November 1957). (14) Monk, R. G., llercer, A., llownham, T., ANAL.CHEM.35, 178 (1963).
5 ) Xosen, A. W., Schmitt, R. A,) \-asilevskis, J., .4nal. Chim. Acta 25,
10 (1961). 6) Schmitt, R. A,, Smith, R. H., Lasch, J. E., Xosen, A. W., Olehy, D. A,, T*asilevskis, J. Geochim. Cosmochim. iicta 27, 577 (1963). 7 ) Smales, A. A., Geochim. Cosmochim. Acta 8. 300 (19551. 8) Tobias, C. .I.,I h n n , Iample spectra. However. we would also expect other samples to sholv an escess of nitrogen due t o this effect, but this is not observed. The figures for calcium have not been listed. The calculated results showed no consistency at all, being as much as several time3 larger or smaller than the values based on weighing. Furthermore, the omission of the calcium data from the program made no difference in the amounts of the other elements found. Thus. whether the stripping program was run for all six elements or for only five (omit,ting calcium), the same results were obtained. The reason for t'his is evident in the very low value of A , for calcium. I t is less than lY0 of the value for phosphorus at the same energy, and zinc and chlorine also overshadow it. Comparison of the results in the second and third lines for each sample shows that the two computer programs are alniost, equally satisfactory. The ratio of observed to theoretical standard deviations i.3 not unreasonably large when the errors due to flux variation and gain shifts are considered in addit,ion to counting statistics. The two programs take almost the same time on the 113x1 7094, namely, about 5 seconds per sample. The iterative stripping pro-
gram is somewhat. more versatile than t,he simultaneous equation program in that it contains subroutines which are readily adapted to simpler problems. Also, because it is more closely analogous to graphical procedures for resolving spectra. t,he radiochemist can be of more help in diagnosing malfunctions in the program. The improvement in the simultaneous equations results over those previously reported can be explained by these changes: the smoothing of data to fit theoretical decay curves improves the statistical accuracy in the standard coefficients; the control of temperature in the detector and of gain in the ampli-
fier provides more reproducible data in duplicate irradiations; the preparation of samples by mixing the solutions used for standards eliniinates the difficulty of reconciling possible errors in chemical or spectrographic analyses previously used as a basis for comparison.
ACKNOWLEDGMENT
R e appreciate the valuable contributions of R. E. Greenwood, who explored the problems which might be encountered in a computer program, and of Sandra P. Guldman, who coded the IBM programs.
Determination of Radioactive Lisuid Scintillator
LITERATURE CITED
(1) dnders, 0 . U., Beamer, JV. H., .ISAL. CHEII.33, 226 (1961). ( 2 ) Breen, J$-. l l . >Fite, L. E., Gibbons, I).> Wainerdi, It. E., Trans. A m . .Vucl. SOC.4, 244 (1961). (3) Gilmore, J. T., Hull, U. E., A s . 4 ~ . CHEX 35, 1623 (1963). (4) Gilmore, J. T., Hull, 11. E., Ihzd., 34, 187 (1962). ( 5 ) Gilmore, J. T.,Hull, 1). E., Fries, B. A,, 6th J$70rld I'etroleuiii Congress, Section V, Paper 19 (1963j. (6) Ku>-kendall,JV. E., FTaiirerdi, It. El., Trans. d m . .YucZ. SOC.3 , 93 (1960). ( 7 ) Salmon, L., AVucl. Inslr. :Ilethotls 14, 193 (1961).
RECEIVEDfor review January 0 , 1964. Accepted July 15, 1964.
Noble Gases with a
DONALD L. HORROCKS and MARTIN H. STUDIER Chemistry Division, Ar!gonne National Laboratory, Argonne, 111.
b The disintegration rates of the radioactive noble gases RnZz2,Xe131m, and K P have been measured with a toluene-base liquid scintillator. This was practical because of the high solubility of the noble gases in the aromatic hydrocarbons used as solvents in liquid scintillators. The distribution coefficients, the ratios of the concentrations of the noble gases in the liquid scintillator to the space above C., it, were measured. At - 1 5 " these were 5 and 32 for xenon and radon, respectively, The differential pulse height spectra of the light output of the liquid scintillator with dissolved radioactive noble gases are shown.
L
SCIXTILLATORS have been used to obtain ihe absolute disintegration rates of beta (8, 12) and alpha ( 6 , 7 , I O ) emitting nongaseous nuclides. The fact that the heavier noble gases are appreciably soluble in the aromatic hydrocarbons commonly used as solvents in liquid scintillators ( I , $ , Q , I I ) makes practical the quantitative determination of radioactive noble gases in liquid scintillators. IQCID
EXPERIMENTAL
Apparatus. The detection and recording equipment consisted of a multiplier phototube i D u M o n t 6292), cathode follower preamplifier, linear amplifier, and multichannel analyzer. [See previous works (4, 6).] The saniple holder-light guides were Lucite
/SMALL LIGHT GUIDE for 0 2 5 mi Liquid Scintillotor (0)
Figure 1.
LARGE
LIGHT GUIDE far IOrnl,Liguid Scintillator
(b)
Light guides-sample holders
cylinders. For small samples a cylinder 1 inch in diameter and ' I 2 inch long with a 7-nim. sample well drilled parallel to the faces waq used (Figure l a ) . For large sampleq a cylinder l 7 inches in diameter and 1' inches long nith a 32-mm. sample well drilled parallel t o the faces was used (Figure l b ) . The light guides were completely painted with a TiOs reflecting paint ( 7 ) except for one face which as coupled to the face of the multiplier phototube. Optical coupling was attained n i t h a clear silicone grease betv een the light guide and multiplier phototube and a clear silicone fluid in the sample well. The samples and multiplier phototube were maintained, for most of this iTork. in a freezer a t - 1.5' C. Liquid Scintillator. The liquid scintillator used in this work consisted of 7 grams of 2,5-diphenyloxazole, PPO, and 0.5 gram of 1,4-bis-2-(4methyl - 5 - phenyloxazolyl)benzene, RI,-POPOP, in 1 liter of toluene. Sample Preparation. The samples were prepared as follows: The desired amount of liquid scintillator was placed in the sample container and flushed with argon to remove a n y dissolved oxygen. This was cooled
to liquid nitrogen temperature and evacuated. X given volume of noble gas, with radioactivc tracer, was condensed onto the liquid scintillator at, liquid nitrogrn temperature, and the sample container wa.q flame sealcd. The sample is n-armed and equilibrated a t the temperature of the experiment (room temperature or -15' c'. in the freezer). Two saniple containers, one for 0.25 ml. and the other for 10 nil. of liquid scintillator, were employed. For the 0.25-nil. size a 6-nini.>thin-n.alled, glass tube served as thc liquid containcr. On top of this n-a. a 2-mni. i.d. capillary tube for reduction of the iliace above the liquid scintillator. The 10-nil. size sample container.; were made from 30nim. o.d. g1as.W tubing. 'The small neck was for sealing the containers and reducing the silace abo\-e the liquid scintillator. The small bize containers were used for determining radon and xenon. Hon-ever. becau*e of thc high energy electrons from Kr5j, I:,,:,, 672 k.e.v., the larger size container was used to minimize wall effect?. The distribution of nohle gases between the liquid scintillator and the space above it was nieawred for 0.25 ml. of liquid scintillator in saml)le containers as >holm in Figure 2. The shorter container? w r e Iirepared from the original tallezt container by freezing the xenon and radon Ivith liquid nitrogen and successively sealing off I)art.>of the container tube. The ca1iillar>- tube made possible a minimum space above the liquid scintillator in the final samlile. I t alw reduced the geonietry for excitation of the hquid rrintillator by c'lcctrons and alpha particks producwl in the gas phase hy the decay of Xpl3lrn VOL. 36, NO. 11, OCTOBER 1964
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