1
L
-
7
Figure 1 .
-
Figure 2.
TIME, MIWTES
B
A. 6. C. D.
Air Ether Acrolein Water E. I-Butanol
Analysis of furfural on column A A. Air 6. W a t e r C. Ether D. Furfural E. Phenol F. in-Cresol
quantities in the ether solution, but not enough to obscure acrolein on the chromatogram (Figure 2). Ether overlaps formaldehyde on column 13; hence a resin containing both acrolein and formaldehyde requires separate aldehyde determinations. The acrolein/ 1-butanol peak area factor (1.58 i 0.11) was determined by adding known amounts of acrolein to an acrolein-free low inolecular weight formaldehyde rebin in neutral aqueous solution and extracting the aqueous solution with ether. When acrolein was added to a strongly alkaline solution of rebin, only a trace showed up on the chromatogram, presumably because the acrolein homo-
Analysis of acrolein on column
ACKNOWLEDGMENT
polymerized (3) or reacted rapidly with phenolic resin. This analytical method has been applied to resins prepared with varying ratios of acrolein or furfural to phenol as well as to phenolic r e i n s prepared with mixtures of formaldehyde and acrolein. Phenol-furfural resins thus require only column A; phenol-acrolein resins require both .A and B. Phenol-furfuralformaldehyde and phenol-acroleinformaldehyde resins also require both columns; however, separate aldehyde determinations are necessary with the latter. Free furfural has, in the past, been determined by the titrimetric bisulfite method (1, 2 ) .
The author acknowledges support for this work from the Oronite Division of California Chemical Company. LITERATURE CITED
(1) Brown, L. H., Ind. Eng. ('hem. 44,
2673 (1952).
( 2 ) Ihnlop, A . P., Trimble, F., I r u . ENG.CHEM.,ANAL.ED. 11, 602 (1939). (3) Gilbert, E. E., Ihnleavy, J J., J . A m , Chem. SOC.60. 1911 (1938).
(4) Maksorow, B. I-.,Andrianow, K. A , , Ind. Eng. Chem. 24, 827 (1932). ( 5 ) Stevens, hf. P., Perrival, 1). F., ASAL. CHEM.36, 1023 (1964). M. P. STEVESS] California Research Corp. Richmond, Calif.
Present address, Dept. of Chemistry, Robert College, Bebek P. K. 8, Istanbul, Turkey.
Gravimetric Determination of Sodium with Radiotracers SIR: The most, commonly used method for the determination of macro amounts of sodium is precipitation with zinc uranyl acetate ( 2 ) . Although this method yields accurate results under optimum conditions, its use has been limited by the need to regulate closely such experimental variables as concentration of sodium, volumes of sample and reagent, and temperature. The lengthy period required for quantitative precipitation of sodium zinc uranyl acetate has also been detrimental to routine application. This method is readily adapted to radiotracer techniques because exchange of sodium ii;otopes can be accomplished easily and comldetely. Deviations from qmntitative precipitation of sodium can be detected accurately by 168
ANALYTICAL CHEMISTRY
measuring the recovery of sodium tracer and the result can be corrected accordingly. This communication describes an evaluation of this standard method with the help of radiotracers. .A modified procedure that resulted from this evaluation is presented below. This procedure accelerates the determination of sodium by eliminating the need for a protracted precipitationdigestion period. EXPERIMENTAL
Apparatus. Radiometric measurements were made with a single or multichannel pulse-height analyzer equipped with 3- X 3-inch NaI(T1) crystal.
Reagents. Sodium-24 (15.0 hour) was obtained from the Oak Ridge National Laboratory, Oak Ridge, Tenn., as NaCl solutions. Sodium-22 (2.6 year) can be obtained from Nuclear Science and Engineering Corp., Pittsburgh, Pa., or .Atomic Corp. of I m e r i r a , Panorama City, Calif., as XaC1 solution. Other reagents were prepared according to the directions prescribed by Furman ( 2 ) . Recommended Procedure. This procedure is a modification of the one described by Furman ( 2 ) . Evaporate the neutral solution of the sample, containing no more than 10 nig. of S a c 1 and free from interfering ions, to as small volume as possible without causing separation of salts. Add sufficient tracer to yield 105 counts per minute. Heat the zinc uranyl acetate reagent to
approximately 75" C. and then add 10 nil. of the reagent to the sample solution. Stir well and allow to stand until the mixture is a t room temperature (approximately 30 minutes). Filter by suct,ion through a dried and weighed fritted glass filter. Rinse the beaker with the wash solution (957, alcohol saturated with the triple acetate) and wash t,he precipitate with the same solution. Wash the precipitate once with ether to remove the alcohol and 1)ull air through the filter for 1 minute to remove the ether. Dry the outside of the crucible and count the sodium activity of the precipitate by placing the crucible on the 3- X 3-inch K a I crystal. Reweigh the crucible to obtain the weight of precipitate. Calculate the radiochemical yield by dividing the activity of sodium in the precipitate by the total activity of the initial tracer. The total activity of the tracer is determined by evaporating on a small circle of filter paper an aliquot of the sodium tracer equivalent to that used in the analysis, placing the paper on the frit of a glass crucible, and counting under the same conditions used for the samples. The weight of the precipitate is divided by t'he radiochemical yield, and the corrected weight is multiplied by 0.01495 to produce the weight of sodium. RESULTS A N D DISCUSSION
When the method described by Furman (2) was used to precipitate 1 mg. of sodium and NaZ4tracer a t room temperature (23" to 25" C.), only 77% recovery was found by gravimetric and radiometric methods after 0.5 hour of aging. The recovery increased to 85%, S9%, and 97% after 2.5, 5, and 16
A
8 $? 8 0 1
f
A
8
I
I 0
70
0 0
60 GRAVIMETRIC
25OC 0 , O 75OC A
RADIOMETRIC 25OC 0,m 75OC A
0.5
Figure 1 .
1.0 1.5 V O L U M E , ml
Effect of volume of sample
1 mg. of N a , 1 0-ml reagent, 2.5 hours aging
hours, respectively; however, 24 hours of aging was required to ensure quantitative precipitation. I n addition, the amount of sodium being precipitated was observed to affect the degree of recovery after specified aging timesLe., the percentages of 0.5, 1.0, and 2 mg. of sodium precipitated in 3 hours were 73, 87, and 91, respectively. A constant volume of sample, 1 ml., is specified in the standard method because of the possibility of loss of precipitate through partial solubility of sodium zinc uranyl acetate ( I ) . Although results obtained from gravimetric and radiometric measurements
agreed closely when a sample voluine of 1 ml. was used, the agreement was poor when the sample volume was 0.5 ml. or 2.0 ml. (Figure 1). These discrepancies indicated an additional source of error-coprecipitation of reagent with the triple acetate. Much better correlation between gravimetric and radiometric measurements, as well as greater recovery of sodium, can be achieved by adding the reagent a t an elevated temperature and allowing sodium zinc uranyl acetate to precipitate as the system cools to room temperature (Figure 1). As a result of t,hese experiments, we recommend the modified version of this standard method wherein radiotracers are included for yield correction, and the zinc uranyl acetate reagent is preheated to improve the purity of the precipitate and to increase the recovery of sodium. The time required per analysis is decreased significantly and the accuracy increased, thereby enhancing the usefulness of this method for routine analysis. LITERATURE CITED
(1) Barber, H. H., Kolthoff, J. iM., J . Am. Chem. SOC.50, 1625 (1928); 5 1 ,
3233 (1929). (2) Furman, N. H., "Standard Methods of Chemicals Analvsis." Vol. I. ww. 13-14, \'an Nostrand, New York,'19'69 W. J. Ross
Analytical Chemistry Division Oak Ridge National Laboratory Oak Ridge, Tenn. RESEARCX sponsored by the U. S. Atomic Energy Commission under contract with the Union Carhide Corporation.
Determination of Lanthanum in Actinide-Lanthanide Mixtures by Isotopic Dilution and Mass Spectrometry SIR: We have successfully applied isotopic dilution and mass spectrometry to the determination of lanthanum in highly radioactive solutions of americium, curium, and rare earths. Conventional gravimetric or titrimetric techniques either lacked specificity for lanthanum or involved chemical separations that would have required use of extensively shielded analytical facilities. In the pilot scale test of the CmZ4' separations process at the Savannah River Plant, lanthanum was added early in the process as a carrier to increase recovery of the trivalent actinides. The feed solution to the Tramex process ( 4 ) that separates the actinides from the rare earths therefore contained about 1 gram of curium and 30 g a m s of lanthanum per liter. T o evaluate the performance of the pilot
scale operation, it was necessary to determine curium-lanthanum weight ratios that ranged from 0.03 to 1000 in process samples. EXPERIMENTAL
A quantity of pure La203, 2.16% enriched in La1%, was obtained from Oak Ridge National Laboratory. A nitric acid solution of known lanthanum concentration was prepared from this material for use as the internal standard. Isotopic analyses of lanthanum samples before and after isotopic dilution were made with a single-stage surface einission mass spectrometer, Cugsolidated Electrodynamics Gorp.> Model 21-702, equipped with an electron multiplier and vibrating reed electrometer for the detection system. Magnetic scanning was used and a correction (5) for mass
discrimination of the electron multiplier was applied to the results. To avoid interference from I3a1Sn (6.31y0 thermal neutron fission yield from Pu239) (S), a single filament surface ionization source was used and the L a 0 + peaks at masses 154 and 155 were measured. With this type of source, lanthanum evaporated as L a o + , whereas barium did not evaporate as the oxide ( I ) . A small amount of borax added to the samples enhanced the formation of L a o + . To reduce radiation exposure, the Trames feed solution was diluted by a factor of lo3 with 1M HXO,. Equal aliquots of the dilution were pipetted into four glass vials, and a known quantity of the enriched lanthanum standard solution waf then added to each of two of these vials, Finally, equal aliquots of the lanthanum standard were pipetted into two additional vials. The solutions in each VOL. 37, NO. 1, JANUARY 1965.
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