LITERATURE CITED
spite the dificulties of end point detection.
(1) Amin, A. hi., Chemist Analyst 44, 17
ACKNOWLEDGMENT
( 2 ) Bastian. R.. AXAL. CHEX 21, 973 (19492. '
(1965).
Bastian, R., Weberling, R., Pallila, F., Ibid., 22, 160 (1950). Blaedel, W. J., Knight, H. T., Ibid., 26, 741 (1954). Cohen, A. I., Gordon, L., Ibid., 28, 1445 (1956). Flaschka, H., JIikrochemie ver. iirikrochinL. ~ c t 40,21 a (1952). Flaschka, H., Huditz, F., 2. anal. Chem. 137, 104 (1952).
The authors wish to thank the Atomic Energy Commission for their partial support of this investigation under contract AT(30-1)-1213. One of the authors, S. J. Gedansky, acknowledges a predoctoral fellowship from E. I. du Pont de Nemoure & Co., Inc.
(8) Goddu, R.F., Hume, D. N., ANAL. CHEM.26, 1740 (1954). (9, Harris. W. F.. Sweet, T. R., Ibid., 24, \ - r
1062 (i952j.
(10) Hiskey, C . F., Ibid., 21, 1440 (1949). (11) "S:ott'[; Standard Methods of Chemical Analysis," 5th ed., vol. 1, p. 822, Van Nostrand, New York, 1939. (12) Siggia, S., ANAL. CIIEM. 19, 923
(1947).
RECEIVED for review September 4, 1956. Accepted December 28, 1956. Pittsburgh Conference on Analytical Chemistry and Applied Spei:troscopy, March 5 , 1957.
Effect of Different Carrier Gases on Retention Times in Gas-Adsorption Chromatography S. A. GREENE and H.
E.
ROY
Aeroiet-General Corp., Azwsa, Calif.
Retention times of eluted gases are markedly affected by different carrier gases on the same column. Carrier gases, which are adsorbed to any extent, occupy more active adsorption sites, reducing the net heat of adsorption of the eluted zone, and thus the retention time. This technique has its exact analogy in liquid partition chromatography, wherein different solvents are used to effect separation.
V
ARIOUS carrier gases have been
used in gas-adsorption chromatography. Nitrogen, helium, hydrogen,
and carbon dioxide have been reported to give good results as far as detector thermal conductivity cell stability and sensitivity are concerned ( 2 ) . The use of different carrier gases has also been found to have a pronounced effect on the retention times of eluted gases on the same charcoal column. The effect of five different carrier gases on the retention times of methane on an activated-charcoal column has been investigated. The efficiency of separation of a loiv-boiling gas mixture, using two different carrier gases, helium and argon, is shown to depend markedly on the carrier gas, as do the retention times of the components.
IC
z W
->:
W
2F-
r
D I S I ~ U S S I O NAND RESULTS
The apparatus and procedure have been described (I). I n gas-adsorption chromatography, one usually uses helium, hydrogen, or nitrogen, inert carrier gases thxt are not adsorbed to any great extent. It was thought thaS the use of a carrier gas which was adsorbed would have iome effect on the separation of gaseous mixtures. More active adsorption sites would be occupied to some extent by the carrier gases, and the retention times of eluted gases would be reduced. Table I shLows the retention times of methane eluted from a lGfoot, 40/60mesh charcoal column a t 25" C., obtained with five dzerent carrier gases. Figure 1 shows the separation of a mixture of soime low-boiling gases, using helium as the carrier gas on the same column. Gases were separated by raising the coluinn temperature from ambient to 170" C. in 45 minutes during elution. Figure 2 shows the separation of a similar mixture, using argon as the carrier gas, by raising the
z
1
W
2: B v)
a a V
W
a
a W
n
a
0
V W
Figure 1. Separation of gas mixture by helium 'elution
a C
J !5"25
45
TIME (MIN.) VOL. 29, NO. 4, APRIL 1957
569
IO
Figure 2. Separation of gas mixture by argon elution
->' I
Y
w
Table 1.
Retention Times of Methane
Carrier Gas Helium Argon Nitrogen Air Acetylene
Retention Timea, Min. 34 22 16 15 5
' a Retention times of methane on a 10foot charcoal column at 25" C., floiv rate of carrier gases is 70 cc./min.
v1
$ 5
a
v)'
W
U
a W
n
n
0
u a W
0 3
column temperature to 160" C. in 35 minutes. The poor response to carbon dioxide is caused by the similarity of thermal conductivity of carbon dioxide and the carrier gas. . The use of argon as the carrier gas permitted the elution of ethane a t 160' C., while, with helium, ethane did not come off even when the column temperature was a t its maximum of 200" C. for 20
TIME
35
(MINI
minutes. Elution with air, nitrogen, or argon also imp *eves the symmetry of the recorded wave forms. A C K N O W I EDGMENT
The research m:is conducted under financial support of the United States Air Force.
LITERATURE CITED
(1) Greene, S. A., Moberg, 11. L., Wilson, E.M.,ANAL.C H E M . , 1369 ~ ~ , (1956). (2) Patton, H. W., Lewis, J. S., Kaye, W. I., Ibid., 27, 170 (1955).
RECEIVED for review August 31, 1956. Accepted November 19, 1956.
Separation of Bismuth from Uranium Using Thioacetamide Precipitation G. A. STONER and H. L. FINSTON Brookhaven National Laboratory, Upfon, N. Y
,This work was initiated to find a suitable means for the removal of bismuth from small amounts of uranium, allowing for a subsequent determination of the latter. It was found that bismuth sulfide could b e precipitated from a homogeneous solution using thioacetamide with no apparent loss of uranium. A rapid, quantitative method for the separation of bismuth from microgram quantities of uranium was obtained, permitting the routine analysis of uranium.
S
on the use of thioacetamide in acid solution ( I , 3) for the precipitation of bismuth have afforded a separation of bismuth which is superior to the coni-entional hydrogen sulfide TUDIES
570
ANALYTICAL CHEMISTRY
or oxychloride nic1,hods. In addition to the general advantages of precipitation from homogeiieous solution, the use of thioacetamitlc permits the precipitation of bismu ;1i sulfide from 2M nitric acid a t elewtted temperatures which would be complicated by the formation of elemer tal sulfur using the conventional hydrogen sulfide gassing technique. The much smaller solubility product constant of bismuth sulfide indicates a more complete removal of bismuth 3s the sulfide than as the oxychloride (j?). The increasing in1erest in the liquid metal fuel reactor systems (4, using solutions of uranium in bismuth as the fuel, has made quantitative separation of bismuth from uranium necessary. Even small amounts of bismuth inter-
fere with most known methods for the determination of uranium in the concentration ranges 10 to 1000 p.p.m. of uranium. Removal of the bismuth as bismuth oxychloride prior to the polarographic determination of uranium results in an extremely large bismuth wave which makes the accurate determination of uranium difficult. Complete removal of bismuth sulfide using hydrogen sulfide gas showed a considerable loss of uranium in the final analysis, probably due to occlusion. Synthetic alloy solutions were prepared from bismuth and uranium enriched in uranium-233 (927- uranium233, 8% uranium-238). The alpha counting rate mas determined for a standard uranium solution. The background contribution from the bismuth
