Feb., 1954
FILTRATION OF MONODISPERSE ELECTRICALLY CH;\RGEDAEROSOLS
X lo4 Hendricks has postulated that about 20% of the total surface of kaolinite is on the lattice edges,s8 which leads to a comparable value for a natural gradation of Peerless kaolinite, namely, 4 X lo4 cm.2/g. If the monovalent exchangeable ions are involved in protein adsorption, and if they are on the edges of the kaolinite particles, the area per ion1’ is 16 A.z. Thus a protein molecule may cover many surface exchange sites. This comparison of figures rests on the assumption that the molecules of protein do not unfold during the adsorption process. Unfolding a t airliquid interfaces a t least can lead to protein denat~ration,~O and we have found that eluted lysozyme is active. Hence, the globular state of the adsorbed molecule seems probable. The problem is not unambiguous. If we assume that the molecule unfolds on the mineral surface, and adopt39the area per mg. protein as ca. one m.2 (which is typical of proteins), 26 mg. of protein would cover 26 X IO4 which is comparable to the total surface area. of the kaolinite particles, namely, ca. 19 X lo4 On this basis, the area per molecule is ca. 2,500 A.2. Ileenan, et al., find 80 per exchangeable ion if averaged over the entire surface and the protein molecule in the unfolded state would still cover many exchange sites. Another reason for believing that the adsorbed molecules are st8ill globular is that if they were elongated the actual (38) 6. B. Hendricks, I n d . Ene. Chem., 37, 625 (1945). (39) H. B. Bull, Advance8 i n Protein Chem., 3, 95 (1947).
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surface area covered would expectedly be far less than that of the kaolinite particles for reasons of steric hindran~e.~OThe data of Claesson and Claesson, showing a decrease in maximum adsorption of a linear polymer with increasing molecular weight, illustrates this point of view. Elution of Lyso~yme.-Otliers~~-~~ have shown that lysozymea2 is strongly adsorbed to kaolin, cellulose, charcoal, et8c. As is seen from Fig. 4, it is possible to elute lysozyme with suitable change in pH or addition of salt, as demonstrated by ultraviolet absorption spectroscopy. Preliminary observations indicate that lysozyme may also be eluted with ethylamine hydrochloride and that the eluted enzyme is fully I n the adsorbed state, lysozyme is inactive toward Micrococcus Z y s o d e i ~ t i c u s . ~Gieseking, ~ et al.,4s have shown that, the addition of clays to enzymes in solution decreases the enzyme activity. It is possible that most of the residual enzyme activity in these systems is due to unbound enzyme. Acknowledgments.-The author wishes to thank Dr. D. E. Williams for aid with the sodium analyses. (40) E. L. Markor and ,J. H. van der Waals,
J. Colloid Sci., 7 , 535
11 9.52).
(41) L. K. Wolff, Immunitatsforach, u. e m . therapg, 60, 88 (1927).
. (London), B93, 306 (1922). (42) H. Fleniinp. Proc. R O T /Soc. (43) I. Biiganovskaya and Z. W. Jerrnol’era, Acta med. U.R.S.S., 1, 248 (1938). (44) We are indehted t o Dr. R. Feeney for the bio-assays. (45) M. AI. Mortland and J. E. Gieseking Proc. Soil Sci. S O C .A m . 16, 10 (10.52).
I
FILTRATION OF MONODISPERSE ELECTRIC-ILLY CHARGED AEROSOLS’ BY GUYG. GOYER,~ RUTHGRUENAND VICTORK. LAMER Department of Chemistry, Columbia University, New York 27, N . Y . Received Mag 66, 1965
Uniform particle size liquid aerosols were charged electrically by passage through a wire to cylinder corona discharge. The unipolar droplets carried a positive charge ranging from 25 to 150 electronic charges depending on the intensity of the charging field (5-18 e.s.u.) and the radius of the aerosols droplets ( 0 . 2 5 4 5 5 ~ ) . Charge and radius were det,ermined with a Millikan-type oil drop apparatus. The maximum theoretical charge was not obtained and a distribution of charge on uniform particle size particles waR observed. Factors affecting the incompleteness and non-uniformity of charge in the present procedure are: electric winds, turbulent flow, non-uniform velocity of flow and charging times, inhomogeneity of the field gradient. Although a completely uniform charge was not obtained, a sufficiently well defined charge range was obtained for the particle radii studied, t o yield reproducible filtration a t a given size as a function of the average particle charge. Filtration of charged dioctyl phthalate monodisperse aerosol droplets through Chemical Corps No. 5 filters was studied a t two linear velocities, 2.7 and 28 cm./sec. An appreciable decrease in penetration is observed upon charging. As would be expected, this decrease is larger a t smaller linear velocities. The time of transit of the charged particles through the filter layer is an important factor. The effect of charges on filter penetration is larger the Rmaller the droplet, size.
Introduction The theory of electrical charging of conductive and dielectric spherical particles involves two distinct mechanisms : charging by diffusion, important at smaller sizes (
