Reproducibility. Fifteen determinations conducted over a period of several days on a sample of scheelite concentrates containing 70y0tungsten trioxide gave a mean molybdenum content of 2.63% with a standard deviation of 0.03.
LITERATURE CITED
Crouthamel, C. E., Johnson, C. E., ANAL.CHEM.26, 1284-91 (1954). ( 2 ) Dick, A. T., Bingley, J. B., Yuture 158. 516 11946). (3) Fishe; Scientific Co., Pittsburgh, Pa., Bull. hfo-301-E. ( 4 ) Ginzberg, L. B., Liir'e, Yii. Yu., (lj
Zmodskaya Lab. 14, 538-45 (1948 I Analyst 74, 281 (1949) (ahstrart) (5) Grimaldi, F. S., Wells, R. C., 1x0 ENG. CHEW,ANAL. ED. 15, 315
(1943). RECEIVED for review December 6, 1956. .4crepted February 23, 1957.
Use of Silica Gel and Alumina in Gas-Adsorption Chromatography S. A. GREENE
and H. PUST
Aeroief-General Corp., Azusa, Calif. ,The use of silica gel and alumina in gas-adsorption chromatography is compared b y analyzing a complex gas mixture. These adsorbents are generally similar, although alumina is superior for light hydrocarbon analysis. Carbon dioxide can b e eluted from silica gel a t a low temperature and can b e separated from near boiling hydrocarbons.
L
work has been done on the separation of gases using ndsorp-
ITTLE
F i g u r e 1. Separation of gases on silica gel column
IO
eral similarity of silica gel and alumina as far as retention times and order of elution of hydrocarbons are concerned. They report poor separation of hydrogen, oxygen, and methane, and somewhat better separation for light hydrocarbons with these adsorbents. A comparison has been made of the heparation of a mixture of some low hoiling gases and a spectrum of hydrocarbons on silica gel and alumina colunins. Silica gel is a versatile column
W
~
W
P
-3L
tion columns packed nith silica gel. Patton and coworkers ( 2 ) note the gen-
Y
packing generally similar to aluniiiiti except in the elution of carbon dioxide, which is irreversibly adsorbed in the latter, and in the position of acetylene. EXPERIMENTAL
The apparatus was described previously (1). Helium carrier gas flow rates were 70 cc. per minute. Columns contained 20 feet of 20- to 40-mesh adsorbents. The alumina used was Alcoa-F1, activated (Alcoa Chemical Products, Aluminum Co. of America) ; the silica gel was Davison Chemical Corp. silica gel-desiccant. The teclinique of programmed heating adsorption columns was used in both cases. RESULTS A N D DISCUSSION
v)
x W
8 0
a
0 0
Figure 2. Separation of gases on alumina column
Figure 1 shows the separation of a mixture of gases on the silica gel column. Column temperature, initially a t 5" C., was raised t o 155' C. in 65 minutes. Good resolution of lower boiling components was obtained, while higher boiling components were not satisfactorily separated. Figure 2 shows the separation of the same mixture in the alumina column under identical conditions. I n this case carbon dioxide is irreversibly adsorbed, but all other components are resolved. It seems likely that when the resolution of air into oxygen and nitrogen is not required, silica gel columns could be used for separations that are usually done on charcoal columns. LITERATURE CITED
Greene S. A., Moberg, M. L., Wilson, E. h.,ANAL. CHEM. 28, 1369 (1956). ( 2 ) Patton, H. W.,Lewis, J. S., Kaye, W.I., Zbid., 27, 170 (1955). '
I 0
65 TIME
LMINJ
for review August 31, 1056. RECEIYED Accepted February 23, 1957. VOL. 29, NO. 7, JULY 1957
1055
