'-^f$. /<>/ I's/fo^ (3^ MDDC - 903 (LADC - 274) UNITED STATES ATOMIC ENERGY COMMISSION DETERMINATION OF RARE EARTH ELEMENTS IN URANIUM COMPOUNDS by R. C. Hirt N. H. Nachtrieb Los Alamos Scientific Laboratory Date of Manuscript: Date Declassified: J»me 24, 1944 January 31, 1947 This document is for official use. Its issuance does not constitute authority for declassification of classified copies of the same or similar content and title and by the same authors. Technical Information Branch, Oak Ridge, Tennessee AEC, Oak Ridge, Tenn., 4-11-49--750-A4418 DETERMINATION OF RARE EARTH ELEMENTS IN URANIUM COMPOUNDS By R. C. Hirt and N. H. Nachtrieb ABSTRACT The separation of the "rare earth" elements from uranium and its compounds may be obtained by means of an ether extraction, precipitation as fluorides, and purification by way of the hydroxides. The final determination is carried out spectrographically, using a Jarrell-Ash Wadsworth Spectro- graph and an A.R.L.-Dietert Multisource. Dysprosium, gadolinium, samarium, neodymium, praseo- dymium, lanthanum, and cerium were investigated, and their limits of sensitivity and their recoveries from UjOgdetermined. The method may be applied to other "rare earth" elements as well. The procedure used for the separation of the rare earth elements from uranium compounds was that given by H. G. Short and W. L. Dutton in BM -325, with certain modifications to obtain more thor- ough separations. Greater sensitivities were obtained by use of a condensed discharge from an A.R.L." Dietert Multisource instead of a DC arc, and by use of a Dietert Projection-Comparator Densitometer for measuring the relative transmissions of the lines from samples and those of a standard plate. SPECTROGRAPmC DETERMINATION OF RARE EARTH ELEMENTS The spectrographic determinations were carried out with a Jarrel-Ash Wadsworth Automatic Spectrograph having a dispersion of 5.27 A/mm. The electrodes were placed 45 cm from the slit, with a 90 mm spherical quartz lens 37 cm from the slit. The slit opening was 35 microns wide and 2 mm high. Eastman Spectrum-Analysis No. 1 plates were used for photographing the region from 2100 A to 4800 A. Standard solutions of Dy, Gd, Sm, Nd, Pr, La, and Ce of a concentration of 100 micrograms/ml were prepared. These solutions were diluted to make standard solutions of concentrations of lOy/ml and 1 y/ml. Suitable amounts of these solutions were evaporated on 6 mm diameter copper electrodes, on a flat surface freshly cut by a lathe. These were made the bottom electrodes in the spark. An A.R.L.-Dietert Multisource operating off a 230-volt AC line at 19 amperes (primary) was used. 60 microfarads of capacity, 25 microhenries of inductance, and 25 ohms of resistance were in- troduced in the spark circuit. The spark operated at 920 volts, with a 10,000 volt initiator. Expo- sures were for 40 seconds. The resulting spark was found to be quite stable, and the exposure repro- ducible. The S.A. No. 1 plates were developed in Eastman D-19 developer for 3 minutes, placed in an acetic acid short-stop bath for 10 seconds, and fixed in an Agfa acid hypo bath for 3 minutes. The plates were dried in a stream of warm air. A standard plate was made up using 5, 2, 1, .5, .2, .1, .05, .02, .01, and .005 micrograms of each element. The selected lines were photometered on an A.R.L.-Dietert Projection -Comparator Densi- tometer, and the percentage-transmission vs quantity curves plotted. The plates from samples were treated in the same way, and the measured transmissions compared with the graph from the standard plate to determine the amount of the element in question that was present in the sample. MDDC - 903 1 2 MDDC - 903 SENSITIVITIES The limit of detectibility for each rare earth element tested is given in Table 1. Table 1. Limit of Detectibility Element Micrograms Parts per million (10 gm sample) Dy .05 .005 Gd .05 .005 Sm .50 .050 Nd .20 .020 Pr .10 .010 La .01 .001 Ce .10 .010 CHEMICAL SEPARATIONS a. The procedure given below is essentially that developed by Short and Dutton in BM-325. Advantage is taken of the solubility of uranyl nitrate in ether to separate the bulk of the uranium from the rare earth elements. The rare earths are precipitated as fluorides, and purified again by a pre- cipitation as hydroxides to remove Al, Mg, and the last traces of uranium. Details of procedure are not given here; see BM-325. b. Modifications of method of BM-325 1) Three ether -water extractions in place of two. 2) Fluoride precipitate after ignition twice treated with hot concentrated HjSO«. 3) Several rinsings (as many as 5 or 6) of the precipitated hydroxides with 5% NH4OH, found necessary to remove last traces of uranium to prevent the uranium lines ("background") from ob- scuring rare earth lines. Rinsings carried out until no yellow color could be detected on fUter paper. 4) If multiple rinsings failed to remove yellow color, the precipitate was redissolved in HCl, and another precipitation of hydroxides carried out. WAVELENGTHS USED FOR ANALYSIS Table 2 gives the various lines used in the spectrographic analysis, together with their limits of detectibUity and coincident lines. The lines listed which do not have as low a limit of detectibility as the most sensitive lines are used as confirming lines and are also useful when larger amounts of the element are present. RECOVERIES Various known amounts of the rare earth elements were added to 10-gram samples of UjOb These samples were subjected to the separation procedure, and the rare earths analyzed spectro- graphically. Table 3 shows typical recoveries. All samples were 10-grams unless otherwise marked. MDDC - 903 Sample (U, UjOa. etc.) 1+ HNO3 Uranyl nitrate ievap. to dryness + ether (three extractions with 1 ml water) Water layer (contains rare earths, some U, etc.) \ dissolved in HNO3 pp't by HF ^ t Ether layer (contains bulk of uranium) rejected Filtrate (contains U) rejected precipitate (rare earths + C a + Al + some U) evaporated with H^SO^ to remove F t redissolved in HCl, ppt with NH^ OH + salicylic acid (wash ppt several times) ppt rare earth hydroxides dissolved in HCl evaporated on electrode 1 filtrate Ca, Al, and Table 3. Element Micrograms Micrograms added recovered Remarks Dy 10 5 1 .5 5 to 10 not accurate above 5 micrograms 3 to 5 1 .3 to .5 Gd 10 5 1 .5 5 to 10 not accurate above 5 micrograms 4.5 to 5 1 .4 to .5 Sta 10 5 1 5 to 10 not accurate above 5 micrograms 4.5 to 5 .8 .5 less than .6 limit of detectibility .5 Nd 10 5 1 .5 5 to 10 not accurate above 5 micrograms 4 to 5 .7 to 1 .3 to .5 Pr 2 1.2 to 2 Ce 2 1 1.5 to 2 .8 to 1 in 10 milligram sample La 2 1 2 .7 to 1 in 10 milligram sample MDDC - 903 Table 2. Element Wavelength Detectibility Coincident Lines (micrograms) Dy 3531.71 .05 Er 3531.71 Mn 3531.85 3577.99 .05 Mn 3577.88 V 3577.87 3407.80 .05 Fe Pt 3407.46 3408.13 Ce 3407.60 3538.52 .10 V 3538.24 Th 3538.75 3393.58 .20 Fe Cr 3392.66 3393.84 Cr 3392.98 Gd 3422.47 .05 Fe 3422.66 Cr 3422.74 3100.51 .05 Fe 3100.30 Fe 3100.67 3362.24 .05 Ca 3361.92 3350.10 .10 Ca 3350.21 3481.82 .10 V 3482.19 Zr 3481.15 Sm 3592.59 .50 Nd 3592.59 Gd 3592.70 3745.62 .50 Fe 3745.56 V 3745.80 3634.27 .50 Pd 3634.70 Mo 3635.14 4256.40 .50 Nd 4256.48 3568.26 50 Lu 3567.84 Nd 4012.25 .20 Eu Mo 4011.68 4011.97 Ce 4012.39 3851.75 .20 Pr 3851.62 Fe 3852.57 4303.57 .50 Zr 4302.89 3863.41 .50 U 3863.40 Th 3863.39 4156.08 1.00 Mo 4155.58 Zr 4156.24 Pr 4100.75 .10 La 4099.54 Cb 4100.92 In 4101.77 Yt 4102.38 4008.71 .10 Fe 4009.71 Ti 4008.93 4179.42 .20 Cr 4179.26 Cu 4179.51 4118.48 .20 Fe 4118.55 Sm 4118.54 4189.52 .50 Gd 4191.08 Fe 4191.44 La 3949.11 .01 Fe 3948.78 Pr 3949.44 Eu 3949.59 Fe 3949.96 3988.52 .05 Yb 3987.99 Pr 3989.72 3871.63 .05 Fe 3871.75 Dy 3872.12 3794.77 .10 Fe 3795.00 Gd 3796.39 3790.82 .10 Ru 3790.51 Nd 3790.84 Ce 4151.97 .10 La 4151.96 Cb 4152.58 4012.39 .20 Nd Fe 4012.25 4013.82 Cr 4012.47 3801.53 .20 Sn 3801.00 4137.65 .50 Re 4136.45 Cb 4137.10 4186.60 .50 Dy 4186.81 Fe 4187.04 Gd 4184.25 Fe 4184.90 END OF DOCUMENT Digitized by tlie Internet Arcliive in 2011 with funding from University of Florida, George A. 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