detected in solutions of this particular process, these elements are often present in uranium wastes. Radium will be eliminated in the hydroxide precipitation and traces that do carry will be eliminated very effectively in the final extraction of ionium ( 2 ) . Decontamination of ionium from polonium was excellent: 0.02, 0.03, 0, 0.03, and 0.02% in fire experiments. Solutions containing 7.6 X lo4 alplia counts per minute per milliliter of polonium-208 were analyzed using the ionium procedure. Analysis of the various separated fractions in the procedure indicated that essentially all of the polonium was in the oxidized supernatant solution from the lanthanum fluoride precipitation. Thus, polonium behaves like uranium, neptunium, and plutonium in the procedure. As quadrivalent polonium readily carries on lanthanum fluoride from nitric acid solution, the polonium may be in the sexivalent fluoride-soluble state in the presence of potassium dichromate. dpproximately 50% of the protactinium originally present remained in the supernatant solution as a fluoride soluble complex upon the precipitation of lanthanum fluoridc. If protnctiiiium-231 is pres-
ent, the ionium should be stripped from the 0.5M 2-thenoyltrifluoroacetone-xylene by stirring with an equal volume of 2M nitric acid for 5 minutes. Ionium strips quantitatively, leaving the protactinium in the organic phase. Typical decontamination data for protactinium in four experiments (including the final strip with Z M nitric acid) gave 0.03, 0.20, 0.07, and 0.05%. A 2iM nitric acid solution containing 6.5 X lo5 gamma counts per minute per milliliter of protactinium-233 mas analyzed in 1-ml. aliquots by the ionium procedure. The final 2M nitric acid strip solution was counted for protactinium-233 gamma radioactivity using a scintillation counter having a sodium iodide crystal. Although it is rarely necessary, the last traces of protactinium may be removed by re-extracting the 2M nitric acid strip solution with an equal volume of 0.5-$1 2-thenoyltrifluoroacetone-xylene for 5 minutes. Americium and curium are readily eliminated along with the lanthanum carrier when the ionium is extracted with this reagent. The method should prove useful in the carrier-free isolation of thorium isotopes. Although the procedure has been used specifically to determine
ionium in uranium fluorination ash, it should be useful for the determination of ionium in various waters and rocks. Ionium may be isolated from complex mixtures of elements by lanthanum hydroxide and fluoride carrying, followed by extraction with 2-thenoyltrifluoroacetone-xylene. I n analyzing materials containing natural thorium, a final alpha energy analysis should be performed t o differentiate ionium from other thorium isotopes. LITERATURE CITED
(1) Ballou, S . E., Hume, D. S . ,National Nuclear Energy Series, Division IV, Vol. 9, 1755-7, McGraw-Hill, New York, 1951. (2) Hagemann, F., J . Am. Cheni. SOC.,72, 768 (1950). ( 3 ) Koshland, D. E., Jr., Oak Ridge National Laboratory Unclassified Rept., CN-2041 (Jan. 8, 1945). (4) Potratz, H. A., Los Alamos Unclassified Rept., LA-1721 (Sept. 10, 1954). (5) Rickard, R. R., Oak Ridge National Laboratory, Oak .Ridge, Tenn., private communication. RECEIVEDfor review October 23, 1957. hccepted January 27, 1958. Oak Ridge National Laboratory is operated by the Union Carbide Nuclear Co. for the U.S. Atomic Energy Commission.
Detection of Thorium and Uranium JAMES S. FRITZ and EVELIN CARLSTON BRADFORD Institute for Afomic Research and Department of Chemistry, Iowa Sfate College, Ames, Iowa
b Simple qualitative tests for thorium(IV) and uranium(V1) are proposed, based on color reactions with the reagent arsenazo. EDTA is first added to mask foreign metal ions. Uranium(VI) is separated from thorium(lV) by extracting uranyl diethyldithiocarbamate into benzene.
T
exkting methods for detecting thoriuni in aqueous solution are by it:, spectra, fluorescence, and color reactions with organic indicators. A test tube flame test has a sensitivity of 800 p.p.ni. ( 2 ) . Direct spectral analysis using t'he porous cup electrode technique achieves a sensitivity of 35 p.p.m. ( 2 1 ) . Flame photomet'ry a t its best wave lengbh requires a niininiuni thorium concentration of 100 p.p.ni. (21). The fluorescence of thorium with 1 - amino - 4 - hydroxyanthraquinone has been proposed as n qualitative test for thorium (18, 19). The sensitivity is good, but numerous ions interfere. The indicators, alizarin (17),3-alizarinsulfonic acid (9, IC), I-(0-nrsonophenylHE
3 - (2 - arsonophenj-lazo) - 4>5 - dihydroxy - 2,7 - naphthalenedisulfonic 1,8-dihydrox\--3,6-naphthalenedisulfonicacid (arsenazo) forms a violet color acid (4) give sensitive qualitative with thorium and a blue color with tests but are lacking in selectivity, uraniuni(T'1). If uranium(V1) is present especially n ith respect to zirconium. or is to be tested for, a preliminary exhIany qualitative tests for uranium traction of uranyl diethyldithiocarhave been proposed. The fluorescent bamate is carried out. The aqueous method involves observation of the layer is then tested for thorium, and unknown on a fused alkali fluoride the organic portion is tested for uraunder ultraviolet light (1, 10, 1 1 ) . nium(V1). This is a sensitive test, but some metals interfere. Extraction methods have THORIUM TEST increased the selectivity of qualitative tests for uranium in aqueous solution. In the p H range of 1.7 to 3.0. thoMost of these involve extraction of rium can be titrated quantitatively n-ith uranyl nitrate into ether (15) or uranyl EDTA using arsenazo indicator. At diethyldithiocarba~nate into chloroform higher pH values, the violet thorium(7, S), although several other schemes arsenazo complex remained even after have bpen used (13, 16, 20). A good a considerable excess of EDTA had summary of the chemical tests for been added. This was made the basis uranium is given by Kenger and Duckof the proposed qualitative test for ert (17). thorium. Sufficient EDTA is added The qualitative tests proposed for to complex all interfering metal ions thorium and uranium(T'1) are simple, present in the sample. The p H is sensitive. and selective. I n aqueous adjusted to approximately 8 and arsesolution containing (ethylenedri1inito)nazo solution is added. Only thorium tetraacetic acid (EDTA). the reagent and a fen- other metal ionc: give a
azo)-2-naphthol-3,6-disulfonic acid (3,6, 6, l a ) , and 2,7-bis(4-sulfonaphthylazo)-
VOL. 30, NO. 6, JUNE 1958
1021
positive test (violet color), The test is sensitive t o very low concentrations of thorium. Apparatus. Test tubes, 7.5 cm. long and approximately 5 mm. in inner diameter, were made by sealing t h e small end of a medicine dropper. Reagents and Solutions. Arsenazo. Prepare a 3 X l O - 4 M solution from purified 3-(2-arsonophenylazo)-4,5-dihydroxy - 2,7 - naphthalenedisulfonic acid (Eastman Organic Chemicals). Purify the commercial material by slowly adding a saturated aqueous solution to a n equal volume of concentrated hydrochloric acid. Filter the orange precipitate, wash with acetonitrile, and dry for 1 to 2 hours a t 110’ C . Benzene, reagent grade. EDTA. Prepare a 0.05M aqueous solution from the reagent grade disodium or diammonium salt of (ethylenedinitri1o)tetraacetic acid. Pyridine. Mix 1 volume of reagent grade pyridine with 29 volumes of water. Sodium diethyldithiocarbamate (Eastman Organic Chemicals). Triethanolamine (2,2’,2”-nitrilotriethanol). Mix equal volumes of 1M triethanolamine in \ d e r and 0 . 5 X nitric acid. Thioglycerol (Evans Chemetics, Inc., New York, N. Y.). Prepare a 0.0851 aqueous solution. Procedure. Adjust t h e acidity of t h e test solution so t h a t i t is in t h e p H range from 1 t o 3. Place 1 drop of test solution in a spot plate. 4 d d in succession 1 drop of EDTA, 1 drop of triethanolamine buffer, and 1 drop of arsenazo. A violet color indicates the presence of thorium. If uranium may be present, add sodium diethyldithiocarbamate and estract as in the uranium procedure. Then test the aqueous layer for thorium. Results. T h e limit of identification of thorium by this procedure is about 5 y. If a considerably larger volume of test solution is used, 5 y of thorium can be detected a t a dilution of 1 to 500,000. The approximate p H range from 7.5 to 8.5 was optimum. Known solutions were prepared which contained 0 or 5 y of thorium per drop and 400 p.p.m. of a foreign metal ion. Of some 40 metal ions tested, only beryllium, chromium(III), and uranium(V1) interfered. lnterference from uranium(T’1) can be avoided by a preliminary extractive separation Tvith diethyldithiocarbamate. At the level of 400 p.p.m. no interference was encountered from any of the following: Ag +I, Ce +4 Ga +.;
The effect of diverse anions was also
1022
ANALYTICAL CHEMISTRY
studied. Fluoride, oxalate. silicate, tungstate, and vanadate interfered. Borate interfered onlv if the concentration was greater than 0.01,U. Phosphate (0.05M) reduced the sensitivity of the test somewhat. Molybdate, sulfate, and tartrate did not interfere. URANIUM TEST
Uranium(T’1) forms a blue complex with arsenazo over a wide pH range. Like the thorium complex, it will form even in the presence of complesing agents such as EDTA and tartrate. A selectire qualitatii-e test for uraniuni(VI) can be carried out by adding EDTA to mask foreign metal ions, and then adding arsenazo to form a blue color with uranium. Thorium and a few other metals interfere iyitli this test. A nearly specific test for uranium can be acconiplished by first extracting uranium(V1) as the diethyldithiocarbamate from an aqueous solution containing EDTA. The nonaqueous layer is evaporated and then tested for uranium by adding a drop of buffer and a drop of arsenazo. Although EDTA preyents the estraction of most metals, bismuth, copper, cobalt, mercury, d y e r , and tin are extracted along n-ith the uranium. Addition of a drop of thioglycerol just before the arsenazo pel-ents these met,als from interfering with the uranium test.
none of the following ions interfered with the test: Ae+I. Al+3. Ba+2. Bef2. Bi-3. Ca+2.
The effect of various anions on the detection of uranium n-as studied. Small amounts of phosphate (0.005M) do not interfere, but larger concentrations (0.02531) interfere with the uranium test. Although 0.025M tetraborate may be present, 0.05Y tetraborate interferes. Vanadate (0.05M) causes the uranium test to be negative. No interference is encountered from 0.05M bromide, chloride, fluoride, iodide, molybdate, perchlorate. sulfate, tartrate, thiocyanate, or tungstate. LITERATURE CITED
(1) Adler, H. H., P. P. -4tomic Energjf Commission Rept RME-4073 (1956). ClaFki A. R., J . C‘hein. Edlic. 13, 3834 (1936). Clinch, J., L4na1. Chin,. Acta 14, 162-71 (1956). Datta, S. K., Z . anal. C‘henz. 150, 347-55 (1956). Kuznetsov. V. I.. Comwl. /,end. acad, s c ~ C.R.‘S.S. . 31, 898-900 (1941). \
I
(6) Kuznetsov, V. I., J . Gen. Chenz. C.S.S.R. (Eng. Trans1 14,914-19 (1944).
( 7 ) Lacoste, R. J., Earing. 11. H., Wiberlv. S.E.. A \ A L C H m r . 23. 871-4 (i951).
Procedure. Adjust the acidity of t h e test solution so t h a t it is in t h e p H range from 1 to 5. Place 1 drop of test solution in a small test tube and add in succession 1 drop of E D T A , 1 drop of pyridine solution. and 5 to 10 mg. of sodium diethyldithiocarbamate. Add 8 t o 10 drops of benzene and shake vigorously. TTlien the layers have settled, draw off the benzene layer with a medicine dropper or pipet having a narroLv diameter. Transfer the benzene layer to a rrarni spot plate, evaporate to dryness, and add 1 drop of triethanolamine. If ;ig”l, Bi+3; C O - ~ , Cu+2, or Sn-4 may be present in the original test solution, add 1 drop of thioglycerol. Then add 1 drop of arsenazo. A blue or blue-violet color indicates the presence of uranium(T’1) ; a pink color constitutes a negatiye test. Results. The limit of identification of uranium by this procedure is about 6 y. If a considerably larger volume of test solution is used, 6 y of uranium can be detected a t a dilution of approximately 1 to 400,000. KnoTvn solutions lvere prepared that contained 0 or 6 y of uraniuni(TT) per drop and 400 p.p.ni. of a foreign nietal ion. Of 38 metal ions tested, none gave a positive test in the absence of uranium. .kt the lei-el of 400 p , p m
’
(8) AIalissa, H., Miller, F. F., Illikrochemie w r Jfikrochim. ; I d a 40, 63 (1953). (9) Murphy, T.
Current
I
