LITERATURE CITED
(1) Bard, A . J., Herman, H. B., AKAL. CHEJI. 37, 317 (1965). (2) Barradah, R. G., Conway, B. E., Electrochzm. d c t a 5 . 319. 349 11961)
(3) Barradas, R . G:,’ Hamilton, P. ’G,, Can. J . C h m . 43, 2468 (1965). (4) Barradas, R . G., Kimmerle, F. 11,, 47th Canadian Chemical Conferelice, Kingbtoii, Ontario, June 1964. (5) Barradas, R. G., Kimmerle, F. AI., J . Electroanal. Chem. 9, 483 (1965). (6) Barradas, It. G., Kimmerle, F. AI,, Ibid., in press. (7) Blomgren, E., Bockris, J. O’JI., J . Phys. Cheni. 63, 1475 (1959). 18’1 Blomeren. E.. Bockria. J. 0‘12.. Jebch, Ibzd., 65, 2000 (1961). (9) Bockri.-, J. O’IT., Swinkels, D. A. J., J . E l e c h c h e m . Soc. I l l , 736 (1964). (10) Chambers, L. AI., ASAL. CHEM.36, 2431 (1964). (11) Chambers, L. JI.> Miami Talley Laboratorie5, Procter and Gamble Co.,
e.,
Cincinnati, Ohio, private communication, April 6, 1965. (12) Corbusier, P.. Gierst., L.., d n a l . Chim. Acta 15, 254’(1G56). (13) Date, Y . ,S i p p o n Kagaku Zasshi 84, 964 (1963). (14) De Levie, R., J . Electroanal. Chem. 9, 117 (1965). (1.5) Devanathan, M . A. V.,Peries, P., Trans. Faraday Soc. 50, 1236 (1954). (16) Frumkin, A. S , , Damaskin, B. B., “AIodern Aspects of Electrochemistry,’ ’ S o . 3, J. 0’11.Bockris, B. E. Conway, eds., 149, Butterworth, London, 1964. (17) Gierst, L., “Transactions of the Symposium on Electrode Processes,’’ E. Yeager, ed., p. 294, Wiley, New York, 1961. (18) Griffitha, T. S., Jackman, 11. I., Talanta 9, 205 (1962). (19) Herrmann, K. ITr.)’J . Phys. Chem. 66, 295 (1962). (20) Ives, D. J. G., Jam, G. J., “Reference Electrodes,” p. 133, Academic Press, New York, 1961. (21) Kimmerle, F. AI., M A , thesis,
University of Toronto, Ontario, Canada (1964). 1;. ,G.,“Phy&ochemical Hydrodynamics, Prentice-Hall, Englewood Cliffs, N.J., 1962. (23) Meites, L., “Polarographic Techniques,” Interscience, New York, 1955, (24) Potter, E. C., “Electrochemistry,” p. 161, Cleaver-Hume Press, London, 1956. (25) Ileilley, C. X., Stumm, W., “Progress in Polarography,” Vol. 1 , P. Zuman, I. 11.Kolthoff, ed.?., Interscience, New York, 1962. (22) Levich,
F. 11.KIMMERLE R. G. BARRADAS Lash Miller Chemical Laboratories Department of Chemistry University of Toronto Toronto 5, Ontario, Canada RORK supported by the Ontario Research Foundation and a Kational Research Council of Canada Studentship (F.N.K.).
Pressure Changes in Gas Chromatography SIR: The paper by Haarhoff and Van der Linde ( I ) provides an alternative explanation for the results described in my own paper on t h e same subject ( 2 ) . It is certain that the reported pressure pulses in my paper were due t o the viscous effects described by Haarhoff and Van der Linde and not to the partial pressure of the solute, as claimed, and therefore do not support the theory I presented. -1number of experiments have been carried out in an attempt to separate these two phenomena without success and it must be concluded that if a pressure pulse does accompany a solute band down a column then it is insignificant compared with the pressure changes due to viscous effects. As a result of experiments on pressure changes in a column a simple detecting system was developed based on t h e viscous effect of t h e solute band. The apparatus i5 shown in Figure 1. The column, 2 feet 6 inches long and 4 mm. in diameter, with a T junction 4 inches from the end, is packed with 100-120 BS mesh brick dust containing 5% w./w. Squalane. The apparatus is operated exposed, at room temperature, samples being injected by a hypodermic syringe through t h e rubber tubing supplying t h e carrier gas. The side limb and column ends are stopped by ‘/*-inch long glass wool plugs, as shown in the diagram. The side limb is connected to a soap film meter 18 inches long by 4 mm. in diameter by wellfitting rubber tubing. The other end of the soap film meter is connected to a 50-ml. flask fitted with a glass tap. Hydrogen at 5 p.s.i. inlet pressure is passed through the system with the tap turned on. Soap films are set in motion in the flow meter by pressing the soap bulb and the tap is then turned off. 1764
ANALYTICAL CHEMISTRY
Soap film meter
t Syringe
\I Figure 1.
Simple chromatograph using pressure pulse detector
The movement of the soap film slows and finally stops when the pressure in the flask equals that of column at the T junction. If 5 pl. of ether is injected onto the column, there is a slight negative movement of the soap film (2 mm.) which then remains stationary for about 40 seconds until the solute band reaches the side limb. The soap film then rises about 2.5 cm. and then falls again as the solute band passes on through the column. For example with a 10-pl. charge of a 50y0 w./w. mixture of ether and ethyl acetate two pulses, 40 seconds and 60 seconds from the injections, respectively, were produced. The apparatus described above has been used very effectively for demonstration purposes. It is very simple to make from readily available, inexpensive materials and can be effectively
used in schools and universities to demonstrate the simple principles of the chromatographic system. For example, if the dead volume of the column is ignored, log retention volume/carbon number graphs may be determined for a series of low boiling n-paraffins by measuring the time between the injection point and the maximum of the soap film. LITERATURE CITED
(1) Haarhoff, P. C., Van der Linde, H. J., ANAL.CHEM.37, 1742 (1965). (2) Scott, R. P. W., Zbid., 36, 1455 (1964).
R. P. W. SCOTT Unilever Research Limited Colworth House Sharnbrook, Bedfordshire England
