edited by
J. DUDLEY HERRON
Isolation of Uranium by Reduction of Uranyl Acetate Timothy Bonsper 50 North Driuc East Brunswick, New Jersey 08816 The isolation of uranium from its salts, chiefly uranium oxide (UOd and uranvl acetate U02(CzHsOz)2 is a complex procedure involving the precipitation of a suitable oxide compound from the acetate by the equation UO~iCzH30d2+ 2Ca + Hz0
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UOa + 2Ca(C2M30d + Hz
Also included in the experiment is the identification of the oxide from the above reaction, and the isolation of elemental 3C0 U uranium hv the equation UOa 3C Ideally, ['r is rerommended that this experiment takc place in the studs of the higher rlcments. I'erhaps after isolating the element, i t could then be used to study the properties of uranium in subsequent labs. This entire experiment, including a one-hour drying period, should, a t the most, take four hours. Special precautions include the wearing of a lead apron by everybody in direct contact with the radioactive equipment. As manv institutions do not have these anrons as rerrular equipment, it may be feasible to perform the experiment as a demonstration. as onlv one nerson then would be reauired to wear the apron. However, if everybody is to do it, suitable ~rotectionmav he obtained bv takine- a remlar - lab apron and molding lead foil over it. When storine the uranium. ;t should be in an air-tieht bottle, with n o m o r e than 1 g per bottle, clearly lahded "URANIUM and "RADIOACTIVE MATERIAL." However, if the uranium is no longer wanted, it and its salts may he disoosed of in one of the followinn wavs: Convert all of rhe acetate and oxide to elemental urani;m; bury it in an air-tight container with the appropriate labels; or contact Radiac Research Corporation, 261 Kent Avenue, Brooklyn, New York 11211. Phone (212) 963-2233. This company is licensed by the Atomic Energy Commission to dispose of radioactive wastes.
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Materials Uranyl acetate, calcium, two Bunsen burners, vacuum flask, 500-ml beaker, thermometer, analytical balance, 0.005-in. lead foil, carbon, distilled water, 6 -in. piece of K -in. diameter glass tubing, centrifuge tubes, six 50-ml beakers, Geiger counter,
Cotton, F. A., and Wilkinson, G., "Advanced Inorganic Chemistry," 2nd Ed., Interscience Publishers, New York, 19fi7. Keenan, C. W., and Wood, L. H., "General College Chemistry," 4th Ed., Harper and Row Publishers, New York, 1971. Masterson, M. J., and Slowinski,E. J., "Chemical Principles,.' 3rd Ed., W. B. Saunders Company, Philadelphia, 1973. Sienko, M., and Plane, R. A,, "Chemistry," 2nd Ed., MeGraw-Hill Company, New York, 1967.
Apparatus
"Y" connectors, copper (11) sulfate, centrifuge, oven, mortar and pestle, and rubber tubing. The total cost of this experiment is estimated to be $20. This does not include standard laboratorv chemicals such as carbon. calcium. and comer (11) sulfate. ~ k uranyl e acetate may be obtained a cost oi$l0/oz from Cenco Scientific Comoanv. . ,. Chicaeo. . . Illinois. cat. number :39114-018,and theO.UU5-in. lead foil, cat. number379RO-011'. ,nay also he ohrainerl from Cenco at the price of $450 Ih.
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Procedure Precipitation of Oxide
Prepare a saturated solution of uranyl acetate by dissolving 7.6 g per 100 rnl of distilled water used. To this solution add UOz(CzHa02)2 enough calcium to completely read all of the acetate. The calcium should be added slowly to the solution to avoid an excessive liberation of hydrogen. When the reaction is complete, centrifuge the resultant precipitate for approximately 20 min to collect all of the precipitate present. When all of the precipitate has been collected, dry in an oven at 100°C for 1 hr. At the end of this time period, scrape all of the precipitate into a clean, dry container and label. Identification of Oxide
Test a small portion of the compound collected with a Geiger counter, first with no protection, and then with a %in. thick sheet of aluminum separating the compound and counter. If the Geiger counter registers both times, it is an indication that beta and gamma rays are being given off, and that in turn is an indication that uranium is present in the sample. The next step is the identificationof the comoaund throueh of the fact that the onlv " solubilitv tests. In lieht " elements involved in the reaction were uranium, oxygen, carbon, hydrogen, and calcium, the list of possibilities is narrowed down to the following: uranyl benzoate uranium dioxide uranyl formate uranyl oxalate uranium oxide
U02(C7H502)2 UOn U02CHz UOdC204) U07
soluble in alcohol soluble in HNOs soluble in acetone soluble in bases soluble in HCI
Into five 50-ml beakers, pour 25 ml of the following: ethyl alcohol, Volume 53,eumber 8, August 1976 / 515
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HNO?. acetone. ammonium hvdroxide. and HCI.,resoedivelv. To each beaker add a small portion octhe precipitate. Identify the ;ompound according to the following table Soluble in ethyl alcohol HNOs acetone HCI NHIOH
Identify as uranyl benzoate uranium dioxide uranyl formate uranium oxide uranyl oxalate
If the precipitate proves tu he an>.rhmgother than ursnlum oxide, the Precipitation of Oxide Swrion of theexperiment must IE repeated until the precipitate is dtfmitdv ident~fiedto be umnium oxrdr. I t , after repeated attempts, the correct compound cannot be precipitated, substitute sodium for the calcium. However, extreme caution must be used when handling scdium to prevent violent reactions with excess liberation of hydrogen. Reduction of U03 With Carbon Seal oneend ufnR-in. pitceofglass tuhing. indiameter. Appnmimately three t w m h s d r h e way up, rhe tut,eshould havcannrnwed nrck r e e ily.1; n YuD hrndshould tnkr up the remainder of the tube. This end should be connected to a 250-ml vacuum flask eontaining 100 ml of a saturated copper(I1) sulfate solution prepared by adding 70.6 g CuS01.5H20 to 100 ml of distilled water. The neck of the glass tuhe should extend beneath the surface of the copper(I1) sulfate solution, which will act as a carbon monoxide filter. Bunsen burners should be located at the positions indicated by numbered boxes. An aspirator should be connected to the flask, and also to the glass tube by means of a "Y" connector. Weigh out approximately 5 g of uranium oxide. Grind with a mortar and nestle until a fine oowder. Reweirh the mound comoound and weigh out three times chis mass in c a r k n . ~ l both d the carbon and
516 / Journal of Chemical Education
the oxide to the class tuhe aeainst the sealed end. Mix well. Turn on the asnirator to evacuate theentire svstem. When the svstem hashen , , evacuated for approxrmalely 15 mi", clamp o f i t he eonnectiun hetween the aspirator and theglass tuhe, leaving theonneeuon between the aspirator and the vacuum flask open. Heat the mixture of carbon and the oxide strongly until gas can he seen evolving. Reduce the burner flame to medium height and continue heating until no more gas can be seen evolving into the flask. Then reheat strongly for another 5 min. At the end of this oeriod. seal the narrowed neck with a burner and detach from the reit of the svstem. This- tube., sealed a t both ends, serves as n container for the uranium, whde protecting it from atmospheric oxygen dunng the cooling process. Ler r w l for 1 hr.Break open the tube, collect the reduced uranium, weigh, and store safely ~
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Calculating Purity of Reduced Uranium Calculate t h e percentage composition of uranium in u r a n i u m oxide b y the following equation atomic mass of uranium X 1M)% = atomic mass of U03 percentage uranium in compound T h e n compute the weight of u r a n i u m i n t h e sample of UOs that was reduced, b y t h e following equation weight of sample X %composition of uranium in UOs T h i s weight should m a t c h t h e weight of t h e uranium b y n o less t h a n 0.1 g. Any difference represents t h e weight of impurities s u c h as unreduced UOs o r carbon. T h i s difference should b e represented i n percent b y t h e following equation weight of impurities X 100% = %impurities weight of uranium
