the concentrations indicated (in peq. per liter) were: potassium 10.0 =!z 0.13; 1.0 i. 0.085; calcium 40.0 f 0.42; 4.0 i 0.42; sodium 1.0 + 0.006; 0.1 + 0.004. Thus accuracy was comparable to that reported for a considerably more complex instrument [Solomon, A. K., Caton, D . C., ANAL CHEW 27, 1849 (1955)l. Detection limits calculated for sodium (0.0001 p,p.m.) and calcium (0.008 p.p.m.) were approximately one tenth of those reported for another recording flame photometer, while for K (0.0034 p.p.m.) the detection limit was that reported (Khisman, M., Eccleston, B. H., ANAL.CHEK 27, 1861 (1955)]. Figure 2 demonstrates the linearity obtainable with the flame emission from calcium solutions of 20 to 100 peq. per
liter. Flame instability appears to be the principal factor limiting accuracy, since the recording system using the 1P21 is drift-free and random fluctuations at the sensitivities used for flame analysis are less than ==I 1%. During routine flame analyses, sample aspiration time is less than 15 seconds, and can be kept to half this time without sacrificing accuracy. The recorder also reduces the tedium of bracketing each unknown with standard solutions when greatest accuracy is desired. Long-term stability was determined by using a Beckman hydrogen lamp with Model B power supply as light source. Drift and random variations a t maximum sensitivity (dynode voltage 1275, load resistor 2.0 megohms) did not exceed & 37, over a period of 8 hours. At
this sensitivity, full scale reading on the recorder (100 mv.) could be obtained with the light passing through a quartz cell filled with distilled water from the hydrogen lamp and Beckman D U at wave length 200 inw and slit 0.35 mni. KOestimate of the amount of stray light a t this tT-ave length was made. ACKNOWLEDGMENT
The development of this photometer was supported in part by the Institutional Grant of the American Cancer Society. The author is indebted to J. C. Lawrence for assistance in che construction of the apparatus. The apparatus is available from J. C. Lawrence, 733 Florales Drive, Palo *41to.Calif.
Gas-Solid Chromatographic Analysis of Fractions from Air Rectification Columns S. A. Greene,' Aerojet-General Corp., Azusa, Calif. are poorly separated from hydrogen. Elution with hydrogen, using charcoal as the adsorbent at liquid nitrogen temperature, permits separation of helium and neon, but nitrogen again is not eluted. However, nitrogen may be eluted by lowering the Dewar, containing liquid nitrogen, from the column and allowing the column to be warm (Table 11). This must be done cautiously, because hydrogen is rapidly desorbed. With this technique, helium and neon may be quantitatively determined; by raising the column temperature, nitrogen can be determined and hydrogen obtained by differences. Separation of the argon fraction is complicated, because argon and oxygen could not be separated on any of the adsorbents a t room temperature in the apparatus described. Lowering the temperature to that of dry ice did not improve the separations. Ry utilizing argon as the carrier and a Molecular Sieve column at room temperature, oxygen and nitrogen can be determined [Kyryacos, G., Board, C. E., - 4 ~ . 4 ~ . CHEM.29, 787(1957)] and argon is determined by difference.
rare gases are obtained from side T streams which are bled from various sections of air rectification columns HE
(Table I). This paper illustrates how these gas mixtures might be monitored and analyzed by gas-adsorption chromatography. The apparatus has been described [Green, S. A,, Moberg, M. L., Wilson, E. hf., ANAL. CHEhI. 28, 1369 (1956)]. The adsorption columns, 10 feet, 0.25 inches in outside diameter, were filled with 20- to 40-mesh activated adsorbents, and wound into 3-inch coils. Adsorbents were Columbia activated carbon, Davison silica gel, and Linde molecular Sieve 5A. Carrier-gas flow rates were BO ml. per minute. RESULTS AND DISCUSSION
The neon fraction could not be successfully separated at room temperature with this equipment and these conditions. If separation is attempted at 100' K, with argon as the carrier, nitrogen cannot be eluted from the column; helium and neon are eluted together, and 1 Present address, Rocketdyne, Canoga Park, Calif.
Table I.
Gas He H*
Composition of Various Streams from Columns
Neon Fraction 18.6 3.0 44.0
CHI
480
0
... ...
34.4
Trice
..
16
...
Kr Xe
Argon Fraction Before After rectification rectification
.. .. ..
ANALYTICAL CHEMISTRY
84
.
.
I
... ...
0.2
3.8 96.0
Krypton Fraction
... ... ...
...
98.0
Trace 1.0
0.1 1.0
The krypton fraction is separated by either of two adsorbents, depending on the amounts of carbonaceous gas, chiefly methane, present in the stream. On silica gel, krypton and methane could not be separated. When methane is not present (argon and oxygen are not separated), eluting with oxygen on a silica gel column, a t room temperature, ~ i lpermit l separation of argon, krypton, and xenon, and oxygen is determined by difference. When methane is present, it is possible to separate all components by utilizing a lIolecular Sieve 5A column and eluting with oxygen. d t room temperature, argon, krypton, and methane are separated. After methane is eluted, the column is immersed in water a t 90' to 100' C. and xenon is eluted 6 minutes after immersion. Tbis technique does not adversely affect the wave form of xenon, which remains symmetrical. Table II. Retention Volumes of Gases with Various 1 0-Foot Columns and Carrier Gases (60 ml./min. carrier flow, lo-foot columns)
Gas He Ne NP A 0 2
Kr CH, Xe
Retention Volume, Cc. A B C D 180 ... ... ... 360 ... ... ... ... 450 ... ... ... ... 150 160 ... 210 ... ... ... , , . 240 540 ... ... ... 660
. , , 840 960 ... Charcoal column a t 77" K, hydrogen carrier. B. Molecular sieve column a t 23' C., argon carrier. C. Silica gel column at 23" C., oxygen carrier. D. Molecular Sieve column 23-100' C., oxygen carrier. A.
