titrated. The data indicated that these weak acids had not reacted completely with iodide-iodate. The derivatives of nitric, formic, acetic, pivaiic, adipic, chloroacetic, and tri1:hloroacetic acids had O C H ~ / Fratios ~ of 2.0 + 0.1, in agreement with other analytical results. LITERATURE CITED
(1) Ahlum, C. C., Prx. Chem. SOC.22, 63 (1906); Analyst 31, 168 (1906).
(2) Bishop, J. -4.,Summ, s., Chemist43,96 (lgS4). (3)Kolthoff, I. M., Chem. m’eekblad 23, 260 (1926). (4) Kolthoff, I. M., Belcher. R., “T’olumetric Analysis,” T’ol. 111, “Titration
A‘auk SSSR, Inst. Geokhim. i Analit. Khim. 7, 246 (1956); C . A . 50, 15344 (1956). ( 7 ) Starke, K., J. Znorg. Nucl. Chem., in press.
Institut fiir Kernchemie Universitat Marburg Marburg (Lahn), Germany
Methods: Oxidation-Reduction Reactions,” pp. 276, 342, Interscience, Kew York, 1957. (5) Scott, W. W., “Standard Methods of Chemical Analysis,” 5th ed., p. 2245, Van Nostrand, New York, 1952. ( 6 ) Senyavin, M. M., Sorochan, A. M., T r . Koniis. PO Analit. Khim., A k a d .
KURTSTAAKE
The financial support of the Bundesministerium fur Atomkernenergie and of the Fonds der Chemischen Industrie is gratefully acknowledged.
Determination of Minute Quantities of Nitrogen in Argon b y Gas Chromatography SIR: The object of this investigation has been to find a rapid quantitative method for the determination of nitrogen, both in high-purity argon (N2 concentration: 0 to 50 p.p.m.), and in welding argon ( K2concentration : 50 to 200 p.p.m.). T ? e nitrogen in the gas to be analyzed is accumulated by passing the gas throigh a condenser
column containing Molecular Sieve 5A at a temperature of -80” C. The accumulated nitrogen is then introduced into the chromatographic column by passing an amount of carrier gas through the condenser column, which has first been heated to +loo” C, and the chromatogram is obtained in the ordinary way.
EXPERIMENTAL
Apparatus. The apparatus employed in this study was similar t o t h a t used by Brenner and Ettre ( I ) . Highpurity argon gas was used as the carrier. Procedure. T h e column was prepared in a manner similar t o t h a t of Brenner and Ettre ( 1 ) . Sample gas flow rate was 6 to 10 liters per hour. When an adeuqate amount of gas had passed through the column, the tc.mperature of the column was raised to 30” C. and the sampling valve was closed. The column was then heated to 100” C. for approximately 2 minutes and the sample was introduced into the recording apparatus. iifter 1.5 minutes the condenser column was disconnected by turning the sampling valve. This x a s
Start
/
1
14000
X 16 I3 000
12000 II 000 Fj
10000
P N
9000
0
z
: eo00 5
‘
7000
0
6000
z
5000
E E
J
P =
XI
-400
4 000
”5 U
0 Time,
Figure 1.
5000
’300
2 000
-200 g
P
Minutes
Arialysis of 56 p.p.m. Nz in Ar
Sample volume: 2 liters Condenser column: 0.5 meter, Molecular Sieve SA Cond. column temp.: -80’ C. Fractometer column: 2 meters, Molecular Sieve 5 A Fract. columii temp.: f40’ C. Carrier gas: argon G a s flow: 100 ml./minute Paper feed: 2 cm./minute
2
- 100 g
IO00
n.
1
2
3
4
5
6
7
8
9
1
0
Sample Voi.,Lilers.
Figure 2. Break-through points a t concentrations
-80” C. for
different NZ
(Condenser column) VOL. 35, NO. 9, AUGUST 1963
1311
Table I.
Reproducibility of Analysis of 56 p . p m Nitrogen in Argon Sample volume 2 liters
Peak area, sq. mm.
Deviation from mean value, %
735.0 702.5 686.0 '741.0 721.5 694. 8 716.9
$3.0 -1.6 -3.9 $3.8 +1.1 -2.7 $0.4 $1.6 -2.4 +0.9
725,O 696.4 720.0
p.p,m. A relative standard deviation of ~ + 2 . 3 4 7of~ the average has been calculated, corresponding to a confidence limit of 5.75% for the significance level 57,. Table TI contains data from argon containing 9 p.p.m. of nitrogen. The relative standard deviation is +5.7y0 corresponding to a confidence limit of 12.1%.
Table II. Reproducibility of Analysis of 9 p.p.rn. Nitrogen in Argon Sample volume 2 liters
DISCUSSION
done to obtain a stable base line before the nitrogen peak was recorded. S 2 retention time is 3.7 minutes. RESULTS
The apparatus was calibrated with argon containing known concentrations of nitrogen, from 3 to 350 p.p.m. Figure 1 shows a chromatogram of argon containing 56 p.p.m. of nitrogen. Under the conditions of analysis described, 1 11.p.m. of nitrogen corresponds to 6.4 Sq. mm. of the peak area. Table I shows the reproducibility of the data using a nitrogen concentration of 56
Since it is of importance that all nitrogen should be condensed, a special study had to be made to ascertain that this had been achieved. The peak areas were recorded as a function of the sample quantity. For lower and higher concentrations, straight lines were obtained which changed direction at certain points, depending upon the nitrogen concentration, and the peak area mas no longer proportional to the sample quantity. These points were considered to be breakthrough points. (See Figure 2.) ACKNOWLEDGMENT
The author expresses her thanks to Sten Mogensen, Svenska AB Gasac-
Peak area, sq. mm.
Deviation from mean value, %
112.8 111.3 129.8 130.5 116.0 114.0 130.0 123.9 126.0 115.0 129.2 123.5 126.3 116.4 115.5 118.8
-6.9 -8.2 $7.1 +6.7 -4.3 -5.9
+7.3
472.2 +4.0 -5.1 $6.6 +1.9 f4.2 -4.0 -4.7 -2.0
cumulator, Lidingo, Sweden, for having made this work possible. LITERATURE CITED
(1) Brenner, S . , Ettre, L., ANAL. CHEM. 31, 1815 (1959).
BRITT-IIARIE KARLSSON Chemical Laboratories Svenska AB Gasaccumulator Lidingo, Sweden
Determination of Americium-243 in Curium-244 SIR: The technique of isotopic dilution-mass spectrometry was applied succesqfully to the I1reci.e determination of Am243 in the presence of an approuimately equal quantity of Cm244. This method eliminates a difficult and tedious separation of americium from curium ( 3 ) . I n the irradiation of Pu23gfor the ultimate production of Cf252,irradiated target elements must be chemically processed when the fissile Pu239and P 1 1 2 4 1 are substantially depleted. At this stage, a typical target element contains a mixture of actinides of the following approximate weight per cent:
~
~
2
4
i
0
71 c o
J .heas 17 O r c C I 0 ~4c& ~ C111"4 11 0';
~
ANALYTICAL CHEMISTRY
h 2 41
~
The deterniination of all of these nuclides except .1m*43 was made by chemically separating plutonium from the higher actinides and applying established techniques (alpha counting, alpha pulse analysis, and mass spectrometric isotopic analysis). Since the specific activities of Cm242and CmP44
1312
ionization efficiency of americium was about 50 times that of curium. The mass spectrometer was a triple-filament, surface emission instrument (Consolidated Electrodynamics Corp. Model 21-702). The detection system was modified by adding an electron multiplier. Curium-243, therefore, mould not cause errors greater than 1% in the determination of americium-243 unless present in Cm243/hm243 ratio greater than 1 to 2. Since the conditions of irradiation produced a high ratio of Cm2"
1
Pr12'8
pu"1 Pu941 Pu942
are 1000 times that of Am243,Am243 cannot be determined in the presence of Cm*4*--244by alpha pulse analysis or by alpha-gamma coincidence counting. The chemical separation of americium from curium with quantitative recovery of americium is difficult and tedious (3). Beadle, et al. ( 2 ) determined Am243 in a solution that was free of curium by an isotopic dilution technique with the mass spectrometer. We analyzed known mixtures of Am241and CmZ4'by mass spectrometer and found that the
16 h *~~239-~p,240
~400
a270
ay740
Figure 1.
a,*lC?O
Formation and decay of Pu, Am, and Crn nuclides
