however, erratic results were obtained for trace amounts using this technique. Therefore, two procedures for the determination of nickel are recommended; the ammonium hydroxide method for low percentages and the ammonium hydroxide-sodium hydroxide method for higher percentages. I n the spectrophotometric determination of nickel by the ammonium hydroxide method the maximum amounts of iron, copper, and cobalt that may be present in the aliquot are 20 mg. of iron, 0.2 mg. of copper, and 1.5 mg. of cobalt. I n the ammonium hydroxide-sodium hydroxide method the maximum permissible amounts are 15 mg. of iron, 0.2 mg. of copper, and 1.5 mg. of cobalt. More than these amounts cause erratic results. There are no interferences with the neocuproine method for copper ( 2 ) .
I n the cobalt method, on adding the hydrochloric acid to large size aliquots and boiling to destroy the heavy metal complexes of nitroso-R salt, some tungsten precipitates and must be filtered off. Because color is developed prior to the precipitation of the tungsten, this precipitation causes no error. The maximum permissible amounts of iron, nickel, or copper that may be present in the aliquot in which the cobalt color is developed are 15 mg. of iron, 2 mg. of nickel. and 3 mg. of copper. More than these amounts cause low results. The results obtained for iron, nickel, copper, and cobalt in samples of tungsten and tungsten alloys are shown in Table I. The results by the spectrophotometric methods checked the results by classical methods where the range permitted the use of both techniques. The recoveries obtained on
adding standard iron, nickel, copper, and cobalt solutions to tungsten metal and carrying the samples through the procedures were satisfactory (Table
11). LITERATURE CITED
(1) Am. Soc. Testing Materials, “1964 Book of ASTM Standards, Part 32, Chemical Analysis of Metals,” p .
434, Philadelphia, Pa.
( 2 ) Gahler, A. R., ANAL.CHEM.26, 577
(1954).
(3) Gahler, A. R., Hamner, R. M., Shubert,, R. C., Ibid., 33, 1937 (1961). (4) Makepeace, G. R., Craft, C. H.,
IND. ENG. CHEM.,ANAL.ED. 16, 375 (1944). ( 5 ) Rohrer, K. L., ANAL.CHEM.27, 1200 (1955). GEORGE NORWITZ HERMAN GORDON Pitman-Dunn Laboratories Frankford Arsenal Philadelphia 37, Pa.
Rapid Removal of Transuranium Elements from Aqueous Solutions Prior to the Determination of Total Lanthanide Fission Products SIR: The radiochemical determination of total lanthanide fission products in solutions containing high levels of the very radiotoxic transuranium alpha emitters presents a difficult problem to the radiochemist. It is desirable to remove the bulk of the alpha radioactivity before performing conventional radiochemical determinations and nuclear studies of the lanthanide fission products. Such a step is required because of the potential hazard involved in handling large amounts of alpha radioactivity directly. I n addition, a t this installation it is necessary to reduce the alpha content of transuranium solutions before transportation to another laboratory for the determination of the lanthanide fission products. Because of its speed and simplicity a recent amine extraction technique ( I , 5 ) may be used for the removal of transuranium elements preferentially. However, some revision of this method for the multiple batch actinide-lanthanide group separation is necessary. Excess hydrochloric acid must be maintained a t all times in the aqueous phase to prevent high losses of lanthanide elements and precipitation of various metal ions. Also, because the lanthanide fission products exhibit slightly different extractability (5), a yield correction based on a single carrier is not representative of the entire group. Use of a mixed rare earth carrier containing lanthanum, cerium, europium, and yttrium has been found quite .atisfactory. The decontaminated
aqueous solution may then be analyzed for total lanthanide fission products by one of several conventional procedures (2,S, 6) with the applicat,ionof a yield correction. EXPERIMENTAL
Reagents. 30% (w./v.) Alamine 336-S-xylene. Dissolve 300 grams of Alamine 336-S in 1 liter of reagent grade xylene. Pretreat the solvent b y mixing well for 3 minutes with a n equal volume portion of 1 M hydrochloric acid solution. Centrifuge the organic phase for several minutes and decant it into a glass bottle. Alamine 336-5 is available from General Mills, Inc., Chemical Division, Kankakee, Ill. Mixed lanthanide carrier. Dissolve the appropriate amounts of the oxides or chlorides of lanthanum, cerium, europium, and yttrium to give 5 mg./ml. of each metal in 0.1M hydrochloric acid solution. 1i . 6 M lithium chloride-0.2.M hydrochloric acid solution. Procedure. Dilute the sample solution as much as is practical with 0.1M hydrochloric acid solution. h 1000fold or greater dilution of transuranium solutions is often possible. Pipet a suitable aliquot of the sample dilution into a 50-ml. beaker. Pipet 1 mi. of the mixed lanthanide carrier into the beaker. Evaporate just to dryness on a hot plate. Add 2 ml. of 0.1M hydrochloric acid solution. Evaporate just to dryness. Add 2 ml. of 0.1Jf hydrochloric acid solution and again evaporate just to dryness. Add 10 ml. of 11.6.11 lithium chloride0.2M hydrochloric acid reagent, warm
gently, and transfer to a 50-ml. heavy duty glass centrifuge tube. Add 10 ml. of 3070 Alamine 336-S-xylene and extract for 3 minutes. High speed motor stirrers equipped with glass paddles are excellent for performing the extraction. Centrifuge in a clinical centrifuge for 1 minute. Draw off the organic phase by vacuum and discard. Adjust the aqueous phase to about 0.2.11 i y adding 0.16 ml. of 12M hydrochloric acid solution with a 0.2-ml. graduated pipet. Add 10 ml. of 30% Alamine 336-Sxylene and extract again for 3 minutes. Centrifuge for 1 minute and draw off and discard the organic phase. If more extractions are required, repeat with fresh 10-ml. portions of 30% Alamine 336-S-xylene. Do not add additional hydrochloric acid, however, after the second and third extractions. Wash the sides of the centrifuge tube with about 10 ml. of distilled water and centrifuge for 1 minute. Draw off and discard the organic phase, being careful to lose a minimum of the aqueous phase. Precipitate the mixed lanthanide hydroxides by adding 2 ml. of 6 N ammonium hydroxide. Centrifuge for 3 minutes and decant the supernatant solution. Wash the precipitate by stirring well with about 35 ml. of distilled water. Centrifuge for several minutes and discard the supernatant solution. Dissolve the mixed lanthanide hydroxides with about 10 drops of either concentrated hydrochloric or nitric acid. Analyze the decontaminated solution for total lanthanide fission products by one of the conventional procedures (2, 3 , 6) involving a yield correction. VOL. 37, NO. 3, MARCH 1965
419
Table I.
Recovery and Decontamination of Lanthanide Fission Products from Transuranium Elements
s o . of
extracmt ions 2
Transuranium Q radioactivity added, d.p.m. 1.6 x 107
x 107
3
1.6
4
1 . 1 x 109
RESULTS A N D DISCUSSION
The preferential extraction of transuranium elements by tertiary amines is highly dependent on the concentration of hydrochloric acid, lithium chloride, and amine ( 1 , 5 ) . Removal of these heavy elements must necessarily be a compromise with rare earth yield. Preliminary studies indicated best results were possible using the system 11.6.U lithium chloride-0.2M hydrochloric a ~ i d - 3 0 7.Ilamine ~ 336-S-xylene. The amine is pretreated with 1M hydrochloric acid solution to form the amine hydrochloride. Typical data (Table I) obtained using the procedure described above show that a high degree of decontamination of lanthanide fission products from transuranium elements may be achieved in a rapid and simple manner. T o
Total lanthanide fission roduct yiel , 70 83 1 81.6 71.8
a
Transuranium a radioactivity found in lanthanide product, % 1 46 1.69 0.17
50.0
0.007
61.3 73.7
0.01 0.02
determine the lanthanide yields the mixed lanthanide hydroxide was first precipitated to eliminate the lithium which interferes in the final lanthanide oxalate precipitation. The transuranium alpha emitters used for testing consisted of 239Pu (39.473, 241Am (19.9%),244Cm (39.3'27,), and 242Cm (1.4%). High levels of Bk, Cf, and heavier elements were not available for testing, but it is known that they extract considerably better than curium. The number of extractions necessary depends on the amount of alpha radioactivity which can be tolerated in the subsequent analysis. -4t this installation, transuranium alpha radioactivity in the approximate range 106 to lo7 d.p.m. may be used in a conventional chemical hood. Two extractions are often adequate. An incidental advantage in the method is
that the anionic chloride complexes of many fission products and associated elements ( 1 , 4 extract essentially quantitatively with the transuranium elements. Among these are zirconium, niobium, ruthenium, silver, molybdenum, technetium, zinc, iron, cobalt, copper, mercury, nickel, lead, titanium, manganese, palladium, cadmium, tin, antimony, thorium, protactinium, and uranium. Subsequent lanthanide chemistry may thus be simplified. The method is readily adaptable to glove box or hot cell techniques. LITERATURE CITED
(1) Baybarz,
R. D., Weaver, B. S., Kinser. H. B., Nucl. Sci. Ena. 17, 457 (1963): (2) Hume. L). K..Ballou. N . E.. Glend~,~ enin, L.' E., U.'S. At. 'Energy' Comm. Rept. CN-2815 (1945). (3) McCown, J. J., Larsen, R. P., ANAL. CHEM.32, 597 (1960). ( 4 ) Moore, F. L., U. S. At. Energy Comm. Rept. NAS-NS-3101 (1960). ( 5 ) Moore. F. L.. ANAL. CHEM.33, 748 (1961).
(6j-Stevenson, P. C., Kervik, W. E., U. S.At. Energy Comm. Rept. NAS-NS3020 (1961). FLETCHER L. MOORE W. THOMAS MULLINS Analytical Chemistry Division Oak Ridge National Laboratory Oak Ridge, Tenn. RESEARCH sponsored by the U.S. Atomic Energy Commission under contract with the Union Carbide Corp.
Voltammetric Determination of the Monomethylether of Hydroquinone with a Carbon-Ceresine W a x Paste Electrode SIR: The carbon paste electrode was developed by Adams and Olson to find a new electrode material better suited for anodic voltammetry than solid electrodes (3, 4). Other authors have used this electrode to determine trace quantities of metals in water ( I ) , and to study the electrochemical behavior of organic compounds in water (2). Attempts to use the paste electrode in nonaqueous media have been unsuccessful. Organic solvents dissolve enough of the pasting liquid to cause the paste to flake which continuously changes the effective electrode area. I t occurred to us that a paste preparation with melted Ceresine wax might produce an electrode with characteristics of the paste electrode of Adams and Olson, but usable in nonaqueous media. This report describes a specific application of a carbon-Ceresine wax paste electrode to the determination of the monomethylether of hydroquinone 420
*
ANALYTICAL CHEMISTRY
(MEHQ) in methyl monomer (MMA).
methacrylate
EXPERIMENTAL
The carbon-wax electrode (CWE) was prepared by mixing powdered graphite (Acheson Grade No. 38) with melted Ceresine wax in a beaker. This was done by weighing a given quantity of graphite on a . trip balance in a small beaker. Ceresine wax was weighed into a 2-ounce glass jar, and melted on a hot plate with a minimum of heat. The graphite was slowly poured into the melted wax and the mixture was stirred for about 10 to 15 minutes with a glass rod. The hot paste was tamped into a 2- to 3-inch tube (Du Pont Teflon) of about 1/4-inch i.d. to an approximate depth of 'I4inch. Excess paste was removed from the tip of the tube with a Kimwipe and the paste was allowed to cool and solidify. Electrical contact mas made to the paste by filling the tube with mercury. The
electrode was connected to a conventional polarograph through a platinum wire placed into the mercury. All experiments were done in 80% alcohol with 0.lN lithium chloride and 0.05M potassium acid phthalate as the supporting electrolyte. The reference electrode was 1N calomel (NCE). The cell was thermostated a t 25' f 0.1' C. Either a Leeds & Northrup Electro-chemograph Type E or a Sargent Model X X I was used to record all voltammograms. All scans were started from 0 volt. RESULTS A N D DISCUSSION
The CWE was fabricated with different weight ratios of carbon to wax. This was done to determine the effect of electrode composition on the peak current intensity. The methyl ether of hydroquinone (MEHQ) was used as the electroactive species. The data in Table I show that both the peak cur-
