dently make this Farm-up period necessary. CONCLUSIONS
Mixtures of Freon fluorinated hydrocarbons may be analyzed rapidly, accurately, and conveniently by gas chromatography. The analyses of two mixtures which are available commercially have been studied in some detail; these mixtures are (a) Freon-11 and Freon-12 and ( b ) Freon-12 and Freon114. The studies show that the analyses have 95% confidence limits for the mean of duplicates of about 3~0.5%a t the 50% level for any component. The accuracy is within the reproducibility limits. Approximately 0.5 hour is required to run and to calculate the results of duplicate determinations. I n addition, an analysis for air (noncondensable gases) in Freon compounds and their mixtures has been developed. This method illustrates the applicability of gas chromatography to the determination of components present in low concentrations-e.g., < 0.5’%. Of the operating variables evaluated,
the eluting gas flow rate, the eluting gas pressure, and the current supplied to the thermal conductivity cell xere found to require precise control to obtain reproducible results. ACKNOWLEDGMENT
The author wishes to acknowledge the valuable technical suggestions offered by G. H. Patterson and S. S. Lord, Jr. Most of the data reported were obtained with the assistance of W. 0. Augustin. LITERATURE CITED
Callear, A. B., Cvetanovic, R. J., Can. J. Chem. 33, 1256 (1955). Coull, J., IND.ENG.CHEM.,ANAL. ED. 14,459 (1942). Drew, C. M., McNesby, J. R., Smith, S.R., Gordon, A. S., ANAL.CHEY. 28, 979 (1956). Du Pont de Kemours & Co., Inc., E. I., Organic Chemicals Dept., Wilmington, Del., “Kinetic” Tech. Memo. Nos. 8. 11. Ibid., KO. 19. Gow-Mac Instrument Co., Bulletin TC-953.
Griffiths, J., James, D., Phillips, C., Analyst 77, 897 (1952).
(8) James, A , , Ibid., 77, 915 (1952). (9) James, A., Martin, A,, Biochena. J. (London) 50, 679 (1952). (10) James, A., Martin, A., Smith, G., Ibid., 52,238 (1952). (11) James, D., Phillips, C., J . Chena. SOC. 1953, 1600. (12) James, D., Phillips, C., Ibid., 1954, 1066. (13) Janak, J., Mikrochim. Acta 1956, 1038. Lichtenfels, D., Fleck, S., Burow, F., ANAL.CHEM.27, 1510 (1955). Minter, C. C., Burdy, L. Jf. J., Ibid., 23, 143 (1951). Parmelee, H., Refrig. Eng. 59, 573 (1951). Patton, H., Lewis, J., Kaye, W., ANAL.CHEM.27, 170 (1955). Ray, N., J. Appl. Chem. (London) 4, 21, 82 (1954). Sullivan, L. J., Lotz, J. R., Willingham, c. B.. ANAL.CHEhi. 28, 495 (1956). (20) Van de Craats, F., Anal. Chzm. Acta 14, 136 (1956). (21) Webb, G. 9., Black, G. S., IND.ENG. CHEM.,ANAL.ED. 16, 719 (1944). RECEIVED for review March 13, 1956. Accepted September 4, 1956. Contribution S o . 203, Jackson Laboratory. Pittsburgh Conference on Analytical Chemistry and Applied Spectroscopy, Pittsburgh, Pa., February-March 1956; Delaware Chemical Symposium, Newark, Del., February 18, 1956.
Interpretation of Areas Used for Quantitative Analysis in Gas-Liquid Partition Chromatography L. C. BROWNING and J. 0. WATTS Research and Development Department,
b Gas-liquid partition chromatography is applied to the quantitative analysis of water-ethyl alcohol-diethyl ether, carbon tetrachloride-acetone, ethyl alcohol-chloroform, and carbon tetrachloride-chloroform solutions. In solutions in which the difference in thermal conductivity of the components is small, areas under the curves obtained may b e used to determine weight per cent directly. In cases where the thermal conductivities differ considerably, percentages calculated directly from areas do not give correct weight per cent values. In these cases, however, division of the individual areas by the thermal conductivity of the compound allows calculation of the weight per cent from these “reduced” areas with fair accuracy. This empirical correction is applied to the systems studied, and to one previously reported.
I
partition chromatography for the quantitative analysis of liquid and gas solutions using thermal conductivity cells as the N THE USE OF GAS-LIQUID
1 Present address, American Instrument Co., Silver Spring, Md.
24
ANALYTICAL CHEMISTRY
U. S.
Naval Powder Factory, Indian Head, Md.
sensing elements, it is generally assumed (5) that the recorded response for the individual components is closely proportional to the mole per cent of the components, provided certain conditions are fulfilled: that the thermal conductivity of the carrier gas differ greatly from those of the components, and the thermal conductivities of the component be not too different. I n systems in which helium or hydrogen is the carrier gas, and the components are similar in nature, these conditions are met to a close approximation. I n quantitatively analyzing waterethyl alcohol-ether solutions it was found that the areas under the curves could be used directly to obtain weight per cent rather than mole per cent. Since this work was started, two excellent articles have appeared on the application of gas-liquid partition chromatography to the determination of hydrocarbons (1, 9). The areas under the recorded curves in these cases were also found to be proportional to the weight per cent of the components, although this fact was not emphasized. I n view of the importance of these results, the analyses have been extended
to four additional two-camponent sy6tems having components of varying thermal conductivities and molecular weights. The results reported here are for solutions of water-ethyl alcohol-diethyl ether, water-ethyl alcohol, carbon tetrachloride-acetone, ethyl alcohol-chloroform, and carbon tetrachloride-chloroform. Results from Dimbat, Porter, and Stross (1) have been included. EXPERIMENTAL
Thermal Conductivity Cells. Two types of thermal conductivity cells were used. The first was a Victory Engineering Corp. M142 thermistor cell, modified by boring a hole through one side of the cell block, so t h a t the sample and carrier gas passed directly over the thermistor. The reference side of the cell was not modified, and in this case the carrier gas passed through a T in the cell block. The second cell was constructed here (Figure 1). The block is stainless steel, and has two passages drilled through it for passage of the carrier gas and carrier gas plus sample, respectively. Thermistors (Victory Engineering Corp. A22) were inserted in the block a t right angles
to the gas passages, and held in place
