the estimated upper limit of K. Due to uncertainty in estimating D,, as well as to mathematical approximations that have been made, no more than semi-quantitative accuracy can be claimed for K. A more detailed study, not justified at present because of uncertainty regarding estimation of parameters, would require keeping more terms in the expansion, Eq. 11. NOTATION a b C* D 6 H 1 K P* QS QW C R T t X r =l-KF = 1 + K Da/D8 = concentration of water = solubility of HZO in the film = diffusion coefficient = film thickness = Henry's law constant for solubility of water in the film = flux of evaporating water = distribution coefficient for water in air and in film = vapor pressure of water = total evaporation from the film = total evaporation from a pure water surface = gas constant = radius of ring = temperature = time = position coordinate SUb5CrlplS a =air region i = initial condition s = surfactant film region LITERATURE CITED Blank, M. "Monolayer Permeability," Progress in Surface and Membrane Sdence, D. A. Cadenhead and J. F. Danielli, eds., Academic Press (1979). Blank, M., and P. R. Mussellwhite, "The Permeability of Adsorbed M e nolayers to Water,"]. Unlverslty of s0uth.m CalMornla Loo Angd.r, CA 90007 and The phenomenon of reaction rate oscillations in catalytic systems has been the subject of intensive investigations in the last thirteen years. In 1968, Hugo (1968) observed for the first time t h e m e chemical owillations during the exothermic decomposition of N& on a CuO catalyst. Since then reaction rate oscillations have been observed in several other catalytic systems, such as Hz oxidation over Pt foils and wires (Luss et al., 1980; Schmitz et al., 1979) and Pt and Pd supported catalysts (Boudart et al., 1976), CO oxidation Schmitz and Shientuch, 1977), G H l oxidation over Pt films (Vayenas et al., 1980) and N& oxidation over Pt wires (Schmidt over supported and Ul l SUPPOIfed Pt catalysts (carberry et al., 1978 V. U. S. RAO and L. M. POLINSKI et al., 1980). Several comprehensive review papers have now ap peared (Schmitz and Sheintuch, 1977; Slink0 and Slinko, 1978). The majority of the above studies were performed at or near atmospheric pressures and in most cases in a single pellet reactor. Quite recently in our laboratory, reaction rate oscillations have been observed during Fischer-Tropsch synthesis reaction over 13% Fe-precipitated zeolite type catalysts at medium pressures (2.2 X l@ Kpa) in a multipellet Berty CSTR reactor. Some of our observations are summarized in the present publication: The discovery of medium pore zeolites ZSM-5 by Mobil workers (Asgauer and Landolt, 1972) and Nu-1 type zeolite by ICI workers (Whittam and Spencer, 1978) have provided new routes in the indirect liquefaction of a d and its conversion to chemicals zeolites have from the point of view of catalysis, the very important property of solid acidity uacobs, 1977).