width as determined by the sampling rate ( I ). This means that the sampling rate should be chosen to Over sample the signal bandwidth somewhat to most effectively use this approach. Digital filtering can then be applied to the acquired signal to limit the bandwidth to the signal information ( 7 ) .
(2) P. C. Kelly and Gary Horlick, Anal. Chem., 45, 518 (1973). (3) Edward G.Codding and Gary Horlick, SPectroS. Lett. 7, 33 (1973). (4) J. Butterworth, P. E. MacLaughlin, and B. C. Moss, J. Sci. Instrum., 44, 1029 (1967). (5) 1. Coleman, J. Opt.SOC.Amer., 56 (e), IV (1966). (6) B. Widrow, Trans. Amer. hst. Nec. Eng., 555 (1961). (7) Gary Horlick, Anal. Chem,, 44, 943 (1972),
LITERATURE CITED (1) H. V. Malmstadt, C. G. Enke, S. R. Crouch, and Gary Horlick, "Optimization of Electronic Measurements," W. A. Benjamin, k . , Menlo Park, Calif., 1974.
RECEIVED for review July 12, 1974. Accepted August 27, 1974.
Preparation of Pure Xenon Trioxide from Sodium Perxenate Joseph C. Nelapaty, S.J., and Bruno Jaselskis Department of Chemistry, Loyola University of Chicago, Chicago, //I. 60626
Before describing the preparation, the authors wish to point out that solid xenon trioxide, Xe03, is highly explosive which makes storing and handling of the compound hazardous. Acidified solutions (pH < 5 ) of xenon trioxide are stable but pure aqueous solutions decompose on standing and must either be freshly prepared or stored under refrigeration. Xenon trioxide has been used as an analytical reagent for a variety of substances, such as alcohols, ketones, aldehydes, carboxylic acids (1-3), as well as in the synthesis of diols via epoxides ( 4 ) . Since this compound cannot be commercially shipped except by a special courier, it is ordinarily prepared from xenon hexafluoride hydrolyzate as described by Appelman ( 5 ) .The preparation involves the following treatment, with the reagents listed in the order of addition: magnesium oxide, zirconium phosphate, and, finally, zirconium hydroxide which has been washed with nitric acid. A yield of approximately 80% of xenon trioxide is obtained, containing only 0.01M nitric acid as impurity. Small amounts (approximately 20 mg) of high purity xenon trioxide may be obtained by vacuum evaporation of xenon hexafluoride hydrolyzate to dryness, yielding a highly explosive solid which is then dissolved in water. Thus, an alternate and rapid method for the preparation of fresh aqueous xenon trioxide solutions is needed. In the proposed method, aqueous xenon trioxide is prepared from a commercially available sodium perxenate, which is one of the most stable compounds of xenon, and is obtained in almost quantitative yield by passing ozone through a sodium hydroxide solution of xenon hexafluoride hydrolyzate (6 ). Approximately 0.01M xenon trioxide solution is prepared by dissolving 0.2 g of sodium perxenate in 25 ml of triply distilled water. The solution is then passed through a cation exchange column (Bio-Rad AG 50W-X1, H + form) and is eluted with 25 ml of water. Sodium perxenate has only a limited solubility in water (0.025M) ( 7 ) . Hence, xenon trioxide solutions in the concentration range of 0.05-0.10M are prepared by the decomposition of perxenate to xenate upon the addition of powdered Dry Ice, followed by the ad-
354
dition of a previously washed and drained cation exchange resin. In a typical preparation, 1to 2 g of sodium perxenate are placed in a beaker containing 25 ml of triply distilled water. Then the slurry is treated with powdered Dry Ice while the beaker i s kept in a 50 "C bath. Upon the addition of the Dry Ice, the light yellow color deepens and finally disappears. The solution is taken out of the bath, the cation exchange resin (hydrogen cycle) is added, and the solution is stirred until the evolution of carbon dioxide stops. This procedure avoids the breaking of the continuity of the resin column due to gas evolution. The contents are poured into a column packed with the resin, and the solution is passed through the column three times. Finally, the column is eluted with five 5-ml aliquots of water. The resulting solution is approximately 0.05-0.1M in xenon trioxide and amounts to better than 98% conversion efficiency. This pure Xe03 solution will contain H F in the order of 0.002M, when sodium perxenate which was prepared from alkaline xenon hexafluoride hydrolyzate and ozonolysis is used as the starting material. These saiutions may be further concentrated by evaporating off water under reduced pressure.
LITERATURE CITED (1) Bruno Jaselskis, Rec. Chem. Progr., 31, 103 (1970). (2) H. J. Rhodes and M. I. Blake, J. Pharm. Sci., 56, 1352 (1967). (3) H. J. Rhodes, R. P. Shiau, and M . I. Blake, J. Pharm. Sci., 57, 1706 (1968). (4) S. A. Shackleford and G. U. Yven, lnorg. Nucl. Chem. Lett., 9, 605 (1973). (5) E. H. Appelman, "Preparative Inorganic Reactions," W. L. Jolly, Ed., Interscience Publishers, New York, N.Y., 1965, Vol. 2, p 341. (6) E. H. Appelman, lnorg. Syn., 11, 210 (1968). (7) J. G. Malm, B. D. Holt, and R . W. Bane, "Noble Gas Compounds," H. H. Hyman, Ed., University of Chicago Press, Chicago, Ill., 1963, p 167.
RECEIVEDfor review July 19, 1974. Accepted November 1, 1974. The authors wish to acknowledge support by the Petroleum Research Fund administered by the American Chemical Society and by the J e s i . qommunity a t Loyola University of Chicago.
ANALYTICAL CHEMISTRY, VOL. 47, NO. 2, FEBRUARY 1975
