NOTES
July, 1956
0.8 r;
e 23 0.7 M
0
e
0.6
Si,Bi,
0.5
0
0.1
0.2
0.3 0.4 log 2. Fig. 1.
0.5
0.6
1017
actinium samples could be determined by neutron counting techniques. Pure actinium 227 is only mildly alpha active since 99% of the material decays by ,&emission, but the intensity of a-emission grows considerably as the various radioactive daughters accumulate. Accordingly, the intensity of neutron emission from any light element impurity should grow as more and more of the active daughters are formed. The actinium alpha growth was computed from the available nuclear data.4 The neutron growth was then determined from this alpha growth and from the fluorine neutron yields a t the various a-particle energies in the actinium decay chain.s6 A correction for the limited volume of fluorine that is available for nuclear reztction was applied,’ and it was found that the theoretical neutron emission rate for 17.4 mg. of actinium fluoride (corresponding t o one curie of actinium 227) should grow from about 1,000 neutrons per second immediately after separation of the actinium from its daughters to a maximum of 1.07 X lo6 neutrons per second after 0.7 180 days.
The extension of this treatment to the remaining elements is made difficult by the problem of deciding what constitutes the “covalent” radius of these elements. Gordy used Pauling’s values2 of tetrahedral covalent radii to establish (3), but it is doubtful whether these radii are covalent radii in the same sense as those of the more electronegative elements, since the former have been derived from crystal lattice distances. I acknowledge with gratitude the award of a Senior Research Fellowship from the Ministry of Supply. Thanks are also due to Dr. L. J. Bellamy for several helpful discussions. NEUTRON EMISSION FROM ACTINIUM FLUORIDE BY K. W. FOSTER AND J. G. STITES, JR. Mound Laboratory, Monsanto Ch‘hamicalCompany, 1 Miamiaburg, Ohio Received January 18, 1968
One of the methods developed t o prepare the element actinium is the reduction of actinium fluoride with lithium.2 Since fluorine is an excellent neutron producer when bombarded by a-particles,8 and since actinium 227 and many of its daughter products are a-emitters, it is to be expected that actinium fluoride would be naturally neutron active. Likewise, it is to be expected that any appreciable fluorine traces in metallic actinium would result in detectable neutron emission. Therefore, a study of the neutron yield from actinium fluoride was made, and from the data obtained in this study a method was developed whereby the purity of (1) Mound Laboratory is operated by Monsanto Chemical Company for the United States Atomic Energy Commission under Contract Number AT-33-1-GEN-53. ( 2 ) J. G. Stitea, M. L. Sslutaky and B. D. Stone, J. A m . Chem. SOC., 77, 237 (1955). (3) H. L. Anderson, “Neutrons from Alpha Emitters,” Preliminary Report No. 3, NP-851, December, 1948.
A sample of actinium fluoride, weighing 0.77 mg., was prepared by adding an aliquot of actinium chloride solution to 24% hydrofluoric acid in a special Teflon centrifuge tube. This tube was constructed in such a manner that a small molybdenum cup, pressure sealed to the Teflon, formed the bottom of the tube. The precipitate waa centrifuged into this container, and the container and its contents were removed from the centrifuge and dried. The container was then closed with a special lid, apd the assembly was sealed by an even coating of nickel which was deposited from the thermal decomposition of nickel carbonyl. The sealed assembly was then neutron counted periodically for approximately four months. During‘ this period the radioactivity content was determined by periodic calorimetric analysis.
The sample was found t o contain 0.044 curie of actinium, and it attained a maximum neutron count of 53,400 f 600 neutrons per second. Thus, the neutron emission rate from actinium fluoride was found to be 1.21 X 106 neutrons per second per curie of actinium in equilibrium with its daughter products. This compares favorably with the theoretical value of 1.07 X 106 neutrons per second per curie. Both these values are subject to errors which may be quite large. The theoretical value is based on some rather uncertain neutron yields in the higher a-energy range, and the relation that was used to correct for a finite fluorine volume is empirical and has never been determined accurately for fluorine and actinium. The theoretical value may be wrong by as much as a factor of 2. The experimental value suffers from the fact that the neutron emission rates were determined by comparing the sample with a radium-beryllium standard neutron source. There is no assurance that the actinium-fluorine neutron energy apeotrum is sufficiently similar to the radium-beryllium neutron energy spectrum to give the same over-all detector efficiency. I n addition, the ab(4) Circukr 499, Nstional Bureau of Standards, Septembor 1 , 1950. (5) a. T. Seaborg and I. Perlman, Ram. Mod. Phys., 20, 585 (1948).
(6) E. Seere and C. Wiegand, “Thick-Target Excitation Functions for Alpha Particles,” MDDC-185, September 15, 1944. (7) 0. Sisman, “Development of a Process for Produotion of Radium-Beryllium Sources,” Final Report CNL-17. p. 4, January 28, 1948.
NOTES
1018
Vol. 60
solute value of the standard is not known closer linkage by Scott, et aL1 Ludke, et aL12later showed than 10%. Therefore, the actinium fluoride that this band was associated with the aluminumneutron emission rate determined experimentally oxygen-aluminum linkage rather than the aluminum-oxygen-carbon linkage. To verify this correis probably no better than f 15 to 20%. However, since the neutron emission from the lation, it appeared of value to investigate the infrafluoride sample, and the theoretical growth curve red spectra of several aluminum alkoxides. The agreed quite closely over the growth period, and spectra of aluminum isopropoxide has previously since the theoretical and experimental maximum been reported3 but the spectra of the two other alvalues are of the same order of .magnitude, one can koxides discussed in this paper are not available. conclude that the values that were used for com- The present work indicates that aluminum-oxyputation are approximately correct, and the neutron gen-carbon linkages give rise to absorption beyields obtained by extrapolation from data in tween 1028 to 1070 em.-’. reference six are not unreasonable. Thus, the use Experimental of neutron counting techniques for quantitative Alcohols.-Alcohols were stored over Drierite for two detection of trace quantities of fluorine in actinium weeks, filtered and distilled from calcium hydride. The appears feasible. There seems to be no serious ob- boiling points and infrared spectra agreed with reported jection to extending the technique to the detection data.4 Preparation and Analysis of A1koxides.-The alkoxides of fluorine or other light elements, such as beryl- were prepared according to directions in Organic Reactio~is.~ lium or boron, in any of the alpha-active heavy ele- The boiling points of the alkoxides and analytical results for per cent. aluminum are presented in Table I. ments. We wish t o acknowledge the assistance of Mr. TABLE I R. D. Joyner and Mr. S. R. Orr, who found time ANALYSISOF ALUMINUM ALKOXIDES between their regular duties to prepare the acB.p., “C. (mm.) Alkoxide Lit.8 Found Calcdq” Bound tinium fluoride and to perform the calorimetric assay. We are also grateful t q Dr. H. W. Schamp Isopro13.21 13.22 poxide 140.5 (8) 140 (10) for his assistance with the sealing problem.
*
THE INFRARED SPECTRA OF THREE ALUMINUM ALKOXIDES BY DOSALDL. GUERTIS,STEPHES E. WIBERLEY, WALTERH. HAVER ASD JEROMEGOLDESSOS Contribution from the Walker Laboratory of Rensselaer Polyfechnic Inafitute, Troy, N . Y . , and The Chemicnl and Radiological Laboratories Army Chemical Center, -1Iaryland Keceibed J a n u a v y 2.5, 1966
Infrared absorption near 990 em.-’ in aluminum di-soaps was ascribed to the aluminum-oxygen
Sec. Butoxide 2-Pentoxide
180-181.5 (8) 160 (10)
....
140-150 (10)
10.95 11.03 9.35
9.20
Infrared Absorbance Measurements.-Infrared spectra were obtained on a Perkin-Elmer Model 21 double beam recording infrared spectrometer equipped with rock salt optics. Alcohols were measured in a demountable liquid cell without a spacer. Liquid alkoxides were measured in a fixed liquid cell with a 0.025 mm. spacer and in a demountable liquid cell without a spacer to resolve strong bands. Nujol mulls of the solid alkoxides were measured in a demountable liquid cell without a spacer. Potassium bromide windows7 of the solid alkoxides were also prepared, but hydrolysis of the alkoxides occurred in these cases.
Results and Discussion The infrared spectra of the alkoxides and the spectra of the corresponding alcohol in the region of 8 to 12 p are shown in Fig. 1. Table I1 presents the frequencies assigned to the A1-0-C linkage in the alkoxides studied. TABLE I1
100
50
.o
W
FREQUENCIES (cM.-~) ASSOCIATEDWITH THE AI-0-C I N THREE ALKOXIDES LINKAGE
NUM 12- PEN~OXIDE 12
WAVELENGTH
Fig. 1.-Infrared
14
MICRONS,
spectra of three aluminum alkoxides.
Alkoxide
Assignment, cm.-l
Aluminum isopropoxide Aluminum sec-butoxide Aluminum 2-pentoxide
1058
1033 1070
(1) F. A. Scott, J. Goldenson, 8. E. Wiberley and W. H. Bauer T H E JOURNAL, 68, 61 (1954). (2) W.0. Ludke, 6 . E. Wiberley. J. Goldenson and W. H. Bauer, ibid., 69, 222 (1955). (3) J. V. Bell, J. Heisler, H. Tannenbaum and J. Goldenso?, Anal. Chem., 26 1720 (1953). (4) Am. Petroleum Inst., Research Project 44, Carnegie Institute of Technology, ”Catalog of Infrared Spectral Data,” 1950: Sgectrograms 428, 431 and 436. (5) R. Adams, editor-in-chief, “Organic Reactions,” Vol. 11, John Wiley and Sons, Inc., New York, N . Y., 1944, p. 198. (6) “Beilsteins Handbuch der organischen Chemie,” Band 1. Vierte Auflage, 1943. (7) M. M. Stimson and M. J. O’DonneU, J . A m . Chem. Sac., 74, 805 (1952).
