fornium elements would be predicted to sorb at least as efficiently as californium from 0.01M "OB. Europium, californium, and uranium elute essentially quantitatively in the 10M H N 0 3 fraction, as expected for the trivalent and hexavalent ions. The elution curves of Am(III), Cm(III), and Eu(II1) are essentially identical. Plutonium showed the lowest decontamination factor of the actinide elements. The small loss of plutonium to the americium product probably is a reflection of the strong sulfate complexation, which lowers the distribution coefficient for Pu(1V). About 82% of the initial plutonium eluted in the 10M "0, fraction. About 90% of the initial berkelium eluted in the 10M HNOI fraction. The separation of cesium from americium is striking. Less than 10% of the cesium added to the column eluted with 10M HNOa. Cesium exhibits a stronger affinity for zirconium phosphate than many multivalent ions. It is noteworthy that no separation of cesium from americium is attained in the extraction chromatographic method ( 4 ) recently developed. A number of other elements not evaluated here are known to sorb efficiently from 0.01M H N 0 3 like curium. Among these elements are strontium, ruthenium, zirconium, niobium, and iron.
without the necessity to resort to vacuum or high pressure techniques. The method is simple, fast, and requires few manipulations-advantages for glove box or hot cell work. Other attractive features of the zirconium phosphate-nitric acid method are that it is considerably less corrosive than the earlier fluoride systems developed (1-3), and it is more selective for americium than the lanthanum fluoride (2), calcium fluoride (3), or extraction chromatographic (4) methods. We have used the new method as a satisfactory tool for the purification and isolation of americium in solutions containing other actinide (111, IV, VI) ions, lanthanide (111, IV) ions, cesium, and various other ions. A practical problem which often arises in the final purification of curium nuclides is the removal of small amounts of contaminating americium. The zirconium phosphate method described here offers a promising approach for achieving that separation. In process work the most common interferences encountered are chloride ion and a-hydroxyisobutyric acid. These interferences may be eliminated by evaporations with concentrated nitric acid. ACKNOWLEDGMENT
APPLICATIONS
The author gratefully acknowledges the help of F. Nelson and H. 0. Phillips for useful discussions of inorganic exchangers.
The zirconium phosphate cation exchanger for the separation of americium from a number of other elements is valuable both to the analytical and preparative chemist. The column operates at room temperature with relatively high flow rates
RECEIVED for review September 25, 1970. Accepted November 20, 1970. Research sponsored by U. S. Atomic Energy Commission under contract with Union Carbide Corporation.
I AIDS FOR ANALYTICAL CHEMISTS Rapid and Efficient Method for Removing Viscous Polymer Solutions from Nuclear Magnetic Resonance (NMR) Sample Tubes Alex Jakab Research Laboratories, The Goodyear Tire & Rubber Co., Akron, Ohio 44316
WE ROUTINELY analyze polymers by NMR and we have found that the use of solvents, strong acids, cleaning solution ( I ) or pyrolysis to clean the sample tubes is not always successful. We have devised a method for removing these viscous polymer solutions from the sample tubes which is simple and relatively rapid, and increases the lifetime of the sample tubes. We utilize a nonsolvent to precipitate the polymer in situ, in conjunction with a stirring rod made from a copper wire formed into a closed-loop on one end. The diameter of the loop is slightly smaller than the diameter of the sample tube. The copper wire facilitates the mixing of the viscous solution and the nonsolvent, and at the same time provides a nucleation site for the precipitation of the polymer. Our experience has been limited to polybutadienes and polyisoprenes in CCll or benzene, and our procedure is as follows : (1) N. W. Jacobsen, J. Chern. Educ., 47, 507 (1970).
The polymer solution usually fills the bottom inch of the cylindrical sample tube. Sufficient methanol is added to fill the sample tube. The copper loop is inserted and the mixture gently agitated by an up-and-down motion of the stirring wire. The precipitated polymer, which adheres to the copper loop, and any polymer clinging to the wall of the tube are removed by lifting the copper wire loop slowly out of the tube. The liquid remaining in the tube now has a much lower viscosity-essentially a CC14 (or benzene)-methanol mixture, so it can be poured easily from the sample tube. If the precipitation is incomplete, as indicated by only a slight change in the viscosity of the original sample, the nonviscous upper layer is decanted and fresh methanol re-introduced. A distilled water rinse, followed by a half dozen acetone rinses of both inside and outside of the tube, and drying in an air-oven at 70 "C completes the procedure. RECEIVED for review August 26, 1970. Accepted October 8, 1970. ANALYTICAL CHEMISTRY, VOL. 43, NO. 3, MARCH 1971
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