W R e = concentration as a function t of position Z and time t, g./ u = ml.concentration at Z = L and u ' = t = t, g./ml. mean concentration, g./ml. z = concentration at Z = 0, and t = t, g./ml. Reynolds number = d,U'p/p time, sec. interstitial velocity in bed, cm./sec. tube, cm./sec. longitudinal distance in bed, cm. LITERATURE CITED 1. Carberry, J. J., and R. H. Bretton, A.l.Ch.E. JournaZ, 4, 367 (1958). 2. Deisler, P. F., Jr., and R. H. Wiiheh, Ind. Eng. Chem., 45, 1219 ( 1953). based On 3. Ebach, E. A., and R. R. White, A.1.Ch.E. Journal, 4, 161 (1958). 4. Lila, A. W., Ph.D. dissertation, Ohio State Univ., Columbus, Ohio (1959). 5. McHenrv. K. W., Tr., and R. H. concentration at Z = ca and t = t, g./ml. axial diffusion coefficient, sq. cm./sec. diameter of particle, cm. packed bed length, cm. number 1, 2, 3, . . . Peclet number = d, U/DL Reynolds number = d,Up/p Greek e T 5 P P 0 Letters= distance between intersection of 50% points, cm. = wave period, sec. = phase angle, radians = viscosity, poise = density, g./ml. = angular frequency, radians/ sec.Certain assumptions which have previously served as a basis for the conventional equations employed in constant pressure filtration are shown to be in error. It is demonstrated that the specific filtration resistance, the ratio of the mass of wet to mass of dry cake, and the rate of flow, q = dv/de, are not constant as has been assumed. In an example it is shown that q

Expressions are derived in which local porosity in a filter cake is determined as a function of the distance through the cake. Under conditions where the superficial flow rate through the cake is constant and the medium pressure can be neglected, local porosity and the hydraulic pressure are functions of the fractional cake distance.Equations are derived that give the average porosity of a cake as a function of applied filtration pressure.

Electrically conductive blends, containing two immiscible polymers (ethylene vinyl acetate, EVA-19, and copolyamide 6/6.9, CoPA) and polyaniline (PANI), were produced by melt processing. These blends showed a preferred localization of PANI in the CoPA phase, thus enhancing the formation of continuous conducting networks. Electrically conductive PANI-containing filaments produced by a capillary rheometer process at various shear rate levels were studied as sensing materials for a homologous series of alcohols (methanol, ethanol and 1-propanol). All filaments showed a decreasing resistance upon exposure to these solvents. Filaments exposed to methanol, liquid or vapor, exhibited the highest resistance decrease. This behavior was related to the highest polarity of methanol, compared with ethanol and 1-propanol. The filaments' rate of production significantly affects the relative resistance change upon exposure to the various alcohols and their reproducibility.

Electrically conductive blends, containing two immiscible polymers (ethylene vinyl acetate copolymer, EVA-19, and copolyamide 6/6.9, CoPA), polyaniline (PANI), and maleated EVA compatibilizer were studied as sensing materials for a homologous series of alcohols (methanol, ethanol, and 1-propanol). Recent results have shown that the corresponding uncompatiblized blends exhibited a preferred localization of PANI in the CoPA phase, leading to a cocontinuous morphology (i.e., both the CoPA phase and the PANI component located in it are continuous). The concept of the compatibilizer addition was to improve compatibility between the EVA-19 and the CoPA, modifying the morphology of the PANI-containing blend and altering its sensing properties. Extruded EVA-19/CoPA/maleated-EVA/PANI filaments produced by a capillary rheometer process at various shear rate levels were used for the sensing experiments. The filaments displayed high sensitivity levels upon exposure to the various alcohols as well as improved sensing stability and reproducibility at low compatibilizer contents. The sensing properties vary with compatibilizer concentration and are of inferior quality beyond a certain content. The sensing behavior of the compatibilized filaments is compared to the previously reported results for the corresponding uncompatibilized filaments.