Colloids and Surface Behavior W. 0.MlLLlGAN AND G. S. MILL The Rice Insfifufe,Houston, rex.
T
HIS review is concerned with selected portions of the field of theoretical and applied colloid chemistry. The topics of ion exchange, high polymers, and catalysis are adequately covered in other reviews and are not dealt with here extensively. Only a few of the aspects of adsorption are included.
General A biographical sketch, including a portrait and a sunimary of the contributions of the late Herbert Freundlich (1880-1941), was published by Reitstotter ( I S ) . Zocher (16) has presented a historical review of tactosols and mesophases, in commemoration of the work of Freundlich. Sir E. K. Rideal received the 1955 medal of the Society of Chemical Industry, and a brief biography and portrait have been given ( 3 ) . The recipient of the first Kendall award in colloid chemistry, H. N. Holmes, has published his award address (7), which describes the growth of colloid chemistry in the United States. Hauser ( 6 ) has presented a brief history of colloid science, including photographs of selected leaders in this field. The third Kendall award in colloid chemistry went to Victor K. La Mer. The 29th National Colloid Symposium was held in June 1955 a t T h e Rice Institute, Houston, Tex., and it has been announced that the 30th symposium will be held a t the University of Wisconsin, Madison, Wis., in June 1056. General reviews concerned with specific aspects of the field of colloid chemistry have appeared. For example, Kitchener (9)has reviewed the recent progress in the colloid chemistry of surfaces and macromolecules as applied to oil and color chemistry. Krause (10) has reviewed the importance of colloids and trace elements in catalysts. Several new books on colloid chemistry of recent publication are of interest: a volume of adhesion and adhesives ( 1 ) inrludes several reviews presented a t symposia held in Cleveland, Ohio, and London. Books have appcared on paper chromatography (d), emulsions (d), a brief textbook of colloid chemistry (8), application of colloid chemistry to biology and medicine (11), solubilization (I??), and chemisorption (14). Volumes I1 and I11 in a ereries on catalysis (6), edited by Emmett, have been published and contain reviews by sevcral authorities in this field.
Adsor pt ion ADSORPTION APPARATUS
An automatic apparatus for recording adsorption and desorption data has been patented by Van Nordstrand ( 6 A ) , ~ h reco ommends t h e device for the measurement of adsorption of gases boiling below 120' C . on finely divided or porous solids. Titreous silica and other types of torsion balances continue to be applied t o adsorption determinations. Rowers and Long (2-4) describe a microbalance for use a t low temperatures. Bering and Serpinskir ( I A )have employed a high sensitivity silica microbalance t o determine the adsorption of nitrogen on sodium chloride crystals, whereas Day ( S A ) has offered further improvements in a vacuum torsion balance employed in sorption measure-
602
ments on polystyrene. Day claims that his apparatus is capable of a more accurate calibration and a reduction in the overshoot error resulting from radiometric forces. Gregg ( 5 A ) bas described an excellent electromagnetic sorption balance capable of operation in the temperature range of -200" to 1200' C. -4 radiotracer technique has been developed by Dillon and Farmworth ( 4 A ) for the measurement of the adsorption of carbon-14 labeled carbon dioxide on the (110) and (100) faces of single crystals of metallic nickel. Waldnian and McIntosh ( 7 A ) have constructed a new apparatiis for nleasuring the dielectric constants of adsorbed gasep at, frequencies as high as 100 mc. The troublesome question of adsorbed mater vapor on the walls of vacuum systems has bren improved by Wilson (8,4), who reacts the water with methylchlorosilane vapor.
Adsorption Isotherms THEORY OF ADSORPTION
-+
.4n adsorption equation in the forin A' = A / [ l exp ( - k c ) ] has been offercd by Krishnaniui ti ( S s B ) ,in which N is the number of adsorbed molecules, A is the adsorption at saturation, c is the equilibrium roncentration, and k is a constant. Krishnainurti enumerates some definitions of conditions for which his equation approximates the Freundlich, Langmuir, and R E T (Types I11 and V) equations. Zel'dovich ( 7 ? B ) has again discussed the Freund'lich equation, and has attempted to offer a theoretical basis for it. He has developed an integral equation for adsorption on a heterogeneous surface and offers an approximate solution. -411other statistical derivation of the BET equation has been piesented by Keii ( S S B ) , who treats the cases of finite and infinite numbers of adsorbed layers and suggests, as have others, that the Huttig isotherm has no physical significance. Hill (??6B)has continued his detailed ti eatment of corresponding states in multilayer step adsorption (see below). Tests have been proposed by Aston and others ( S B )for a simplified general model of adsorption of rare gases on solids, and Everett (I9B)has revieu ed the adsorption of vapors by solids, including a therniodynaniic treatment of the Langmuir adsorpt,ion model. Honig and Rosenbloom (88B)have discussed the use of interpolation theory in the anaIysis of gas adsorption systems. Interactions betn een adsorbed molecules have continued to attract attention (ZOB, PPB, d7B, 41B, 60B, 66B, 6 i B , 74B). The statistical mechanics of an assembly of water molecules in a potential field provided by a polymer network hap been discusscd by Enderby (18Bl, and a statistical treatment of broadly heterogeneous surfar es has been considered by Keler and Roginskil (32B). A mathcmatical paper has been published by Regak and Sniirnov ( 5 g B ) , n-ith special reference to flow systems involving powdered solids Ratcs of adsorption have rereived some attention, Kwan (40R ) offering a new rate equation. Landsberg (42B) refers to a logarithmic rate law in chemisorption and in oxidation processes. Other rate equations have been discussed by Timofeev (?OB) and Shelechnik (64B). The time of adsorption and oscillation has been studied by Kruyer ( 3 9 B ) , n h o offers expressions tle-
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
Vol. 48, No. 3
COLLOIDS rived from a statistical mechanical treatment. He suggests for mobile adsorption: t = t o exp ( - A H , / R T ) , where t refers to is the heat of adsorption a t 0' K., and to is composed tinie, ma af partition functions. ADSORPTION ISOTHERMS OF GASES ON SOLIDS
Adsorption isothernis for numerous adsorbates on various adsorbents have continued to accumulate more rapidly than the theoretical interpretation thereof. A number of examples of some typical isotherms are given in Table I. CHEMISORPTION
The data on chemisorption have continued to grow. Baker and Kideal ( 6 B ) have observed that chemisorption on metals is characterized by the occurrence of dipole moments perpendicular to the surface, thercby resulting in a change in the work function which can be evaluated from measurements of contact potentials. Loebenstein and Deitz (47B) have measurcd the chemisorption of oxygen on carbon adsorbents, and Weller and Volts (76B) have obtained isotherms and isobars for hydrogen and oxygen chemisorbed on rhromia. The interaction of oxygen with clcan metal surfaces has been followed by Idanyon and Trapnell (43B). These investigators studied both the amount and rate of oxygen, hydrogen, and carbon nionoxide adsorbed on films of rhodium, molybdenum, tungsten, and iron. Bonch-Bruevich ( 1 l B ) has presented a mathematical disciission of chemisorption on defect crystals, and Vol'kenshtein (TIB ) has considered electron processes in chemisorption and has suggested (72R) that two types of homopolar bonds are involved, one being a weak monoelectron bond and the other being a strong dielectron bond.
Application of Adsorption Isotherms STEPWISE ADSORPTION ISOTHERMS
Table 1.
Typical Adsorption Isotherms
Adsorbent
Adsorbate Elements
Refs.
Ahrniinum, molten Nz (6dB) Binary hydrocarbon mixtures (cf. dB. 64B) Carbon Carbon, activated Hn0 (17B) Carbon black CsHs, CHnOH (678) Carbon black N; 16B) Charcoal, activated Hn0 Charcoal, activated Rn carrier gases 06B) Charcoal, activated Ha0 4- CaHrCl (9B) Charcoal added metallic Hn' 01, CO (48B) salts (1%) Chromium, molten N1 Chromium, solid Na Cobalt CO Ha Germanium CO: COa, Ni, H t , Ne, A, Kr, HnO Inorganic Alumina HnO, organic vapors Alumina-chromia gels Hz. Oz Alumina-silica ~ e l s Na' Aluminum aoa& H2O CaHrOH Barium sulfate Aariuni sulfate N2 CHIOH, C1Hia,Ht0 Clay Clay, bentonite CaHs. HzO, SO,, N H I Clay, montmorillonite HzO Clay, montmorillonite NP.On, CaHs, CHIOH, CnHoOH, tert-C4H~O Germanium dioxide HnO Class, microspheres (CHdzO 4- CHCL Glass, plane surfaces HzO Magnesium oxide HnO A Nickel, reduced Nickel oxide 02, c o , co2 Nickel oxide films on nickel 0,. co. cot metal Quartz Nt Silica gel CaH6 Silica gel Na
+
+
[%:
Silica gel Silica gel Silica gel Silica gel Silica1 gel 4- diatomaceous earth Siliceous material Silver nitrate Sodium chloride Zeolites, chabazite
Triethylamine CsHs, CHaOH Hz0. organic vapors
Zeolites, chabazite, and mordenite Zinc oxide
A, Hn, NI, 03 in the presence ( 7 B )
Hz0
CsHs
(37B) (36B) (66B) (66R) (#OB)
X e CHd, C He,
~2l,'n, C;m
of NHa or HIO Ni Organic Cellulose acetate Organic vapors Cellulose acetate NO1 Cellulose nitrate films Organic vapors Insulin. crystals HCI Organic solids NH: Poly(viny1 alcohol) acetate co- Ha0 polymer Proteins HnO
(@Jw
The interesting and troublesome question of the existence and interpretation of stepwise adsorption isotherms continues to attract considerable attention. I n the last review (2%') the the present authors pointed out that considerable work would be required to elucidate this phenomenon. Attention was called to work by Corrin and Rutkowski (8C), who attributed steps o b m v e d by others to failure to attain equilibrium. More recently, Corrin ( 7 C ) has obtained adsorption isotherms for heptane on ferric oxide a t three temperatures a t equilibrium pressures ranging from 0.05 to 70 microns of mercury. The claim is made for precise and reproducible results. No first-order phase transition was observed, and previously reported transitions were attributed to an experimental artifact and t o the very slow rates of adsorption a t the low pressures. Corrin i s of the opinion that the existence of first-order transitions for adsorbed films on solids is doubtful. This view is supported by Tykodi (SSC, 29C) who believes that discontinuities are only observed on a shorttime basis, whereas completely continuous isotherms are ob-
served on a long time bask, a consequence of the slow rate of attainment of equilibrium. However, Clark (6C)has obtained both adsorption and desorption isotherms for krypton on graphitized carbon black a t 70.2' K. with no evidence of hysteresis. Definite vertical discontinuities were observed a t two prewures0.0005 and 0.4 p/po. The steps are attributed to the formation of the first and second layers and agree with an equation given by Singleton and IIalsey. The theoretical approach has been
W. 0. MILLIGAN is professor of chemistry at The Rice Institute where he conducts research on the surface chemistry and physics of colloidal systems, including catalysts. H e is chairman of the National Colloid Syniposium and editor of Proceedings of the National Clay Minerals Conference. His activities in ACS affairs include the advisory committee to the Chemical Corps and the editorial board of Journal of Physical Chemistry.
G. S. MILL, a native of England, received his Ph.D. from Queen Mary College, University of London. His thesis was concerned with adsorption from solution. H e was a research chemist for The British ThomsonHouston Co. and served for several years in the British Army. H e is currently the Humble Oil and Refining Co. post doctoral fellow at The Rice Institute.
March 1956
INDUSTRIAL A N D E N G I N E E R I N G CHEMISTRY
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FUNDAMENTALS REVIEW considered by Hill ( S 6 R ) , who has made calculations employing Clark’s data (6c). The question of reversibility in physical adsorption has been discussed by Pace and others (S4C) in connection wit,h the heats of adsorption of methane, argon, and lirypton on rutile crystals. I n view of the conflicting evidence concerning stepvcisc isotherms, the present authors again suggest that a large amount of very careful work is needed in order to elucidate this phenomenon. MEATS
OF ADSORPTION
Several investigators have exhibited a continued interest in heats and entropies of adsorption. De Boer and Kruyer ( 4 C ) have computed the entropies of adsorption for polar gases, such as methyl chloride, ethyl chloride, propyl rhloride, and ammonia, adsorbed on charcoal. It was conchided that the molecules are mobile and are able to rotate freely; however, water molecules on the same adsorbent are localized below room temperature but are mobile a t higher temperatures. Isoteric heats, differential molar entropies, and diffeiential free energies of adsorption have been reported for several hydrocarbons on rutile by Schrieber and McIntosh (26C). Reyerson and Brand (25C) have calculated the heats of adsorption of bromine on silica gel. Beebe and Dell have reported heats of adsorption for ammonia (QC), methylamine (QC), and sulfur dioxide (SC) on carbon surfaces. Calorimetric heats of adsorption of hydrogen, oxygen, carbon monoxidc, and nitrogen on iron films have been measured by Bagg and Tompkins ( I C ) . Additional heats of adsorption have been reported for argon on potassium chloride (3SC), water on spheron and graphon (ZK’),and benzene vapor on active charcoals ( 1 3 3 . Kwan and Fujita (16C, I 7 C ) and Drain ( I I C ) have discussed the thermodynamics of adsorption, and others have considered various aspects of the subject, including surface regions (14C), hydrophilic heterogeneities (15C), interchange of energy in collision ( S I C ) , and swelling phenomena (88C). ADSORBATE PROPERTIES
Dielectric properties of water adsorbed on alumina and silica gels have been reported by Le Bot and Le Montagner (18C, IQC) and hlcIntosh ( 6 C ) has continued his investigations in this field. It was observed by Melkonian and Reps ( S I C ) that isotope displacement can occur in adsorption and desorption of the systems €€T-&, CHd-CDa, and neon isotopes adsorbed on silira gels at low pressures and temperatures. The growth of crystalline layers on foreign surfaces has been followed by Singleton and Halsey (d7‘C). Eischens and others (lac)have continued their work on the infrared spectra of carbon monoxide chemisorbed on copper, platinum, nickel, and palladium. The results show bands attributed to carbon monoxide bonded to single metal atoms. Optical investigations ( I U C ) , self-potentials in thin films (SC), passivity (SOC), and x-ray studies of the adsorption of water on porous vitreous silica (SOC) have attracted interest.
Pore Size and Surface Area PORE SIZE
A new type of molecular sieve has been described by Dacey and Thomas ( I l l ) ) , who have measured adsorption isotherms for water, pentane, and nitrogen on saran charcoal. These investigators also determined the rates of adsorption of several hydrocarbons and found the results to be consistent with Ficks’ diffusion law. Rarrer ( 4 0 ) has continued his excellent pork on the flow of gases through microporous media. Hysteresis properties of gases adsorbed on iron powder (SOD) and proteins ( 6 D ) have been reported. Several investigators have determined pore sizes and other capillary effects in materials such as silica gel ( d D , brD, d8D), zirconium dioxide (320), calciiim and mag-
~-
nesium oxides (33D), collagen and leather (S5D), carbon rods ( S I D ) , titanium dioxide (12D), and active carbon ( I 4 D , 2 4 0 ) . The relationship between pore size and surface area has recently been discussrd by Voigt and Tomlinson ( S Q D ) ,and E’olman and Shereshefsky (16D) have studied liquid-vapor equilibrium in microscopic capillaries, employing nonaqueous systems. SURFACE AREA
The application of adsorption isotherms and, in particular, the RET equation to numerous porous and nonporous materials has continued, and almost every publication concerned with the experimental deterniination of the adsorption of gases and vapors on solids contains details of surface area mcasuiements Two general reviews of the subject have appeared : Langemann @UD) has dealt with the inathematiral computation of the specific surface of dispersoids, and Dubinin ( I S D ) has discussed and compared the principal methods used in the measiirernent of surface areas. The related topic of particle size determination is treated in another section, and a short discussion of surface area ineasurenients by adsorption from solution is given in the appropriate section. I n addition to the above, details of publications in which the determination of surface areas of varioup substances are a prime concern are given in Table 11.
Table II.
Surface Area Measurements
Substance Alumina, amorphous Alumina, calcined Alumina, chromatographic Carbon black Finely divided solids Havoypite, ailica gel, carbon black Metallic films Nickel oxalate Nitroguanidine Powders Powders Soils Titanium dioxide
Method Adsorption Adsorption -4dsorption Adsorption Gas flow Low-angle x-ray mattering Oxygen adsorption Air permeability and optical Air permeability and microscopic Air permeability Ilarkins-Jura eutropy Mechanical analysis Water adsorption
Refs.
($ID) (SD) (8D)
(POD) (1D) (6D)
(lbD,1 8 0 ) (1OD)
(1OD) (1fiD)
Adsorption Involving liquid Interfaces ADSORPTION FROM SOLUTION
I n previous years, the majority of publications in this field have been concerned mainly with the recording of new data for binary liquid-adsorbent systems and the application of new or existing isotherms to these data. During the past year, however, many workers have turned their attention to more fundamental aspects of the subject-namely, the merhanism, nature of, and factors controlling selective adsorption from solutions. Graham (d6E) has continued his woi k on the characterization of physical adsorption systems, and by determining fieparately the adsorptions of two dyes of similar molecular dimensions, one basic and one acidic, he was able to demonstrate the separate effects of pore size and surface aridity upon the adsorbent capacities of activated carbons. Gilcs and others (2626E) have studied the mechanism of adsorption of a variety of organic compounds in various organic solvents on thin films of 7-alumina and have postulated such mechanisms as salt formation, ion exchange, hydrogen bond formation, chelation, and “bridge bonding” to explain the observed results. Hydrogen bonding has also been invoked by Ulackburn and Kipling (10.5’) to explain the observed adsorptions of several binary mixtures on charroal, and, from a study of the adsorptions of a variety of organic compounds in various organic solvents on nylon and wool fibers, Chipakatti and othrrs ( I @ ) concluded that organic molecules containing hydroxyl groups are also absorbed by hydrogen-bond formation. Strazhesko and Tartakovskaya (8SE) have investigated the mechanism of the adsorption of hydrogen chloride from various
~
solvents on activated carbon and conclude that adsorption from polar solvents is electrochemical in nature, but adsorption froni nonpolar solvents is more complex. The majority of the proposcd mechanisms in this type of work appear to be mainly in the nature of ad hoc explanations but are not to be discouraged, since they may well form the basis for broad generalizations concerning the nature of selective adsorption. Dickey (17E)has repeated his earlier work on the prcparation of specific adsorbents for predetermined substances under conditions that give a more reproducible and more pronounced effect. Complete descriptions of the methods of preparation are given-i e., the fornzation of silica gelA in the presence of organic dyes- -together with a full discussion of the observed results. I n earlier work the specific adsorption properties of such gels were explained by postulating that the surface structure of the gel had been modified so that i t closely resembled that of the adsorbed dye, a view which was supported by Ilaldeman and Emmett ( S S E ) . Dickey has modified this view and attributes the specific adsorption properties to the formation of what he describes as “attraction-favoring configurations.” Nonetheless, the comments of the authors in the previous review (2SC) still stand. As in past years, several Publications have appeared concerning the adsorptions of the homologous series of fatty acids. Blackburn and Kipling ( I l E )have studied their adsorptions from aqrieous solutions on charcoal and have obtained results which indicate that the molecules are adsor bed with the major axis parallel to the surface and the --COOEI groiip perpendicular to the surface. Guasta1l:i and GiiaPtalla (SOB) have studied the adsorptions of the same systems on a paraffin surface and found that in this case the value of the Traube coefficient is smaller than the usual value (2.6 compared with 3.0); an alternation in the adsorptions of the aliphatic acids from aqueous solution on carbon, paralleling the alternation in their melting points, was reported by Morrison and Miller (60E). Surface area measurements of powdered calcium carbonate (84E, 85E) and of clays and rocks (55E) have been carried out by liquid-phase adsorption methods, and although such studies often yield valuable information, too mnch reliance should not be placed on the results obtained, since the effects of solvent adsorption are often neglected. Adsorption and exchange in metal-mctal ion systems have been reviewed by King ( 6 I E , 52E), who has also presented new data for the silver-silver sulfste system, obtaincd by a radiotracer technique. Other studies on the adsorption of ions include the adsorption of sulfate ions (38E)and of iodide ions (44E) on iron, the adsorption of acids, alkalies, and salts on qnartz and silicates ( I Z E ) , and the adsorption of cesium ions (.%‘E) and of cupric ions ( M E ) on filter paper. The adsorption of colloidal or suspended particles from liquids has received attention from a number of workers (533, 7OE, 89E), and l’hansalkar and Vold (67E, 9OE) have described a tracer method for the determination of the deposition of carbon on cotton from a suspension of carbon particles in solutions of sodium dodecyl sulfate. Further studies on multi~nolecular adsorption from solution have been made by Wansen and Hansen (35E), and Puri and others ( 6 9 K ) have studied the effect of different water contents of the adsorbent (silica gel and carbon) on the adsorption of various alcohols from aqueous and toluene solutions. A comprehensive review of the industrial uses of adsorption for the isolation of solutes has been made by IzinaIlov and others ( @ E ) , and Dryrlen and K a y (19E) have derived equations for the kinetics of batch adsorption and desorption which agree with the observed data for the system water-acetone-carbon. Other studies in this field include a theoretical analysis of the kinetics of adsorption of neutral molecules on an electrode whme potential is a sinusoidal function of time ( 9 E ) , a study of
March 1956
COLLOIDS
_ _
the competitive adsorption from aqueous solutions of hydrogen and nitriles on platinum ( d d E ) , a demonstration of the dynamic nature of adsorption from solution (28E),data for the adsorption of the system benzene-cyclohexane on silica gel (83.?3), the adsorption of a number of polar organic compounds froin benzene on steel ( S I B ) , and the adsorption of a number of ternary liquid systems on carbon (543). I n addition, heats of irnniersion of clays (81E,91E) and of dust (68E)in water and of rutile and graphon in organic liquids ( 3 7 3 ) have been reported.
ADSORPTION AT AIR-LIQUID AND LIQUID-LIQUID INTERFACES
Minassian-Saraga (57E49E) has carried out an extensive study of adsorption and desorption a t liquid surfaces, using solutions of lauric arid in 0.0liV hydrochloric acid and has surceeded in verifying the Gibbs adsorption equation. Indirect support for the Gibbs equation hxs also been offered by Guastalla and Guastalla (29E)and by Ghosh and Rakshit (24E). A theory of adsorption from ideal binary mixtures of completely miscible liquids has been presented by Elton ( d I E ) , in which it is shown that the surface activity coefficients of the components a t the liquid-air interface should vary linearly with the bulk mole fraction. Experimental data which suppurt the theory are also presented. I n addition, he has extended the theory to include adsorption a t the liquid-solid interface with similar theoretical results, but no experimental confirmation is yet available. Radiotracer techniques for the study of adsorption a t the solution-air interface have been described by two groups of workers (18E, 76E), and the Gibbs equation has been applied to thc calculation of the force-area characteristics of sodiuni dodecyl sulfate at the air-water interface ( M E )and the calculation of the adsorption of various vapors on mercury surfaces (6E-8E). Only a few publications of adsorption a t liquid-liquid interfaces have appeared. Hutchinson (,$$E)has reviewed the properties of filnis a t oil-water interfaces, and Netter and Ohlenbusch (61E) have derived a theoretical relation between the interfacial potential, surface tension, concentration, and pH value for the adsorption of higher fatty acids a t the liquid-liquid interface. Corkbain ( 1 5 E ) has studied the absorption of sodium dodecyl sulfate a t the decane-water interface, and Gerovich investigated ( W E ) the adsorption of aromatic hydrocarbons a t the niercurysolution interface.
SURFACE FILMS O N LIQUIDS
Apart from a few reports of new apparatus and techniques, little advance has been made in this field during the past year. Inokuchi (4323) has described an improved, accmate film balance, and Allan and Alexander ( 2 3 ) have developed a sensitive direct float balance for the measurement of very low surface pressures. A new technique for compressing surface films (78E), a rotational viscometer for measuring the viscosities of surface films (ZOE), and a radiotracer terhniqiye for the study of uniinoleeular films ( 7 6 E ) have also h e n reported. Some interesting results were obtained by Ries and Kimball (7,9E),who have developed several techniques for the examination of surface films by the electron microscope, hTic>rographs of films of n-hexatriacontanoic acid, taken below the concentration of a monolayer, show islands or aggregates of irregular size and shape surrounded by bare areas. At higher suiface pressures, the aggregates have become continuous and the bare portions discontinuous, while a mirrograph of the collapsed film shows several flat fiberlike structures. On the basis of these micrographs the authors have suggested a mechanism for monolayer collapse which appears to be reasonable. Some comments on the work have been made by Pankhurst (&?E), and these have been answered by Ries and Kimball (738).
INDUSTRIAL AND ENGINEERING CHEMISTRY
605
FUNDAMENTALS REVIEW ~~
-
droxide has been studied many timee in the past, and in all cases an increase in particle size on aging has been reported. It is probable that the former authors actually observed large aggregates (serondary particles) only and did not divern the smaller primary particles of \I hirh the secondary particles are composed, whereas the latter author resolved the primary particles and observed their increase in size. Kolarov (12F) has described an improved method for preparing metal hgdrosols by the Bredig method, in which one of the electrodes is mounted in an A electrical vibrator, thus maintaining a continuous arc, and Mach ( 1 3 ’ ) ha5 described a modification of the Svedberg method for the preparation of metal organosols by which it is claimed that 90% of the metal is reduced to 10-.4. particles. 1-arious patents conrerning the pieparation of silica and alumina hydi osols and organosols have also been filed ( S F , 7F-,W, 18F). The preparation of nickel hydroxide sols containing different particle sizes has been described by Feitknecht anti others (5F),and the particle size distribution in these sols has been studied by Hedert ( I F ) . Suito and others have 0 continued their study of the morphology Figure 1. Electron micrographs of monolayer films of hexatriacontanoic acid; and composition of colloidal particles shadows are light, and arrows indicate direction of chromium shadowcasting(72E) ( 1 6 F , 17F), and Iwasaki and others (10F) A. Blank, no film C. At 25 dynes per crn. have studied the equilibrium existing D. After collapse 6. At 15 dynes per cm. between ionic and colloidal silicic acid in solutions of sodium silicate. A flotation method of separating colloidal particles from their Several workers have studied the effects of salts on various monolayers (SdE, 65E, 86E-88E), Archer and La Mer ( S E , 4s) euspension medium has been described by hfokrushin (14F). The method consists in adding grlatin to the sol and agitating, have measured the rate of evaporation of water through monowhen the particles pass entirely into the foam produced. He layers, and Davies and Rideal ( 1 6 E )have continued their work claims that a total separation was achieved for numerous sols on the penetration of ions into charged films. Shewmaker and of met,als and metallic hydroxides and sulfides. others (8OE)have studied the spreading of benzene and various Various properties of colloidal dispersions have been studied, alkyl benzenes on water, and as in the past years a considerable including flow properties ( I l F ) , coloration ( 6 F ) , and the formanumber of new surface pressure area measurements for a whole tion of ultrafine films on the surfares of colloidal solutions of variety of compounds have been reported ( l E , 6E, lSE, S6E, certain hydroxides ( I 6 F ) . 38E-41E, .45E-47E, QQE,60E,56B, 64E, 7lE, 7dE, W E , 79E).
lyophobic Colloids
lyophilic Colloids and Macromolecules
Extensive studies on the mechanisnl of formation of colloidal particles of titanium dioxide, silicic arid, arsenious sulfide, aluminum hydroxide, vanadium pentoxide, and gold have been made by Berestneva and Kargin with the aid of the electron microscope ( 2 F ) . They found that the initial particles formed were spherical or shapeless amorphous units which broke up, on aging, into more numerous crystalline units. Many micrographs illustrating these changes are shown, and a brief review of earlier work is given. Somewhat different results were obtained by Feitknecht ( 4 F ) ,who studied the formation of colloidal dispersions of hydroxides and hydroxy salta. He found that the primary particles of these sols were amorphous, partly ordered, or fully crystalline. On aging, the amorphous and partly ordercd particles became crystalline, but, in apparent opposition to the work described above, with an increase in particle size. The only sol studied by both workers was aluminum hydroxide, and both workers found that the primary particles of this material were amorphous. However, the aging of sols of aluminum hy-
An authoritative historical review of the colloid science of natural rubber latex has been presented by Hauser (3G). The swelling of gelatin in water has been studied in detail by R’inther ( I e G ) , whose work applies mainly to the first step in swelling. He made measurements of the extinction spectrum from a gelatin interference plate as a function of time in the presenre of water. Equations were developed for the rate of swelling, and thc conclusion was reached that 84% by volume of the water may be adsorbed almost instantaneously, the remainder diffusing only slowly. Schiifer (1OG) has briefly reviewed macromolecular rhemistry, and Staudinger (11G) has discussed the deVel0pnJellt of macromolecular concepts, a subject in which he played an important role. R6my (SG) has suggested a relationship between morphology and macromolecular structure, and Llopis (5G)has discumed the application of the physical chemistry of surfares to the study of macromolecules. The kinetic and optical properties of marroniolecules have received a great deal of atten-
COLLOIDS tion and are dealt R-ith in the appropriate sections. Other topics n hich have received attention include the hydration structure of macromolecules (4G), isotopic tracer techniques in macromolecular chemistry (%), and interrupted two-strand model for deoxyribonucleic acid ( I G ) , specific heats of macromolecules (6G), the thermodynamics of dilute solutions of macromolecules (8G), and the iufluenre of hydrophilic colloids on the miscibility of phenol and water ( ? G ) .
Association Colloids and Colloidal Electrolytes Although numeroiis ahsociation colloids and colloidal electrolytes have bern studied duiing the past year, only a few sclected topics arc included here. A comprehensive review of the inorganic phosphates has been made by Callis and others ( Z H ) , who have shown that certain condensed phosphates consist of long chains of alternate phosphorus and oxygen atoms held together by covalent bonds, n ith degiees of polymerization ranging from 2 to 20,000. Thermodynamic propci ties of polyelectrolytes have been discus& by PIIarcus ( 1 0 H )and by Stigter ( 1 4 R ) ,and critical micelle concentrations have been considered by RIysels and conorkeis (1111,1 6 H ) and by Yhinoda ( 1 2 H ) . TIermans ( B H ) has pointed out that theoretical arguments suggest that all micelles i n a given soap solution need not approach the same size and henve suggest8 a distribution of niicellar wights. Other asperte of association colloids and colloidal electrolytes have been offered by Bsharah (1H), Eigen and Schrarz ( J H ) , Eitel (4H), Gill ( 6 H ) , Gregor and others (GZI, 7 H ) , Katchalsky and 3lichaeli ( 9 H ) , Staiiff (1311), and Stigter ( 1 5 H ) .
Gels
-4 relatively large niimber of publications still continue to appear on the subject of the Lirsegang phenomenon. Tanagihara (,97J, 2 8 J ) has determined the product of the ionic concentrations of the diffusing ions in the rhythmic precipitation of bilver and lead chromates in gelatin and has found that they greatly exceeded the corresponding solubility products. This is evidence in favor of the supersaturation theory of Ostwald. The same author ( 8 9 J ) has also studied the effect of magnetic fields on rhythmic precipitation and found that very strong fields (>lO,OOO gauss) are necessary to cause noticeable shifts in the rings. Empirical relations concerning the distances betwcen rings have been reported (16J, ,94J), and Packter ( 2 0 4 has studied the effect of crystallinity on rhythmic precipitation. Castro Itamos and Nosti Vega ( 6 J ) have reviersed the properties of silica gel and its iridustrial applications, and preparations of series of silica gels having different pore sixes and surface areas have been described ( 5 J , 7 J ) . Patents concerning the preparation of silica gels for specific purposes have been filed (19J,2 / 3 4 , and Hurd and Laning ( 1 5 J ) have published an interesting series of photographs shoning the action of sodium hydroxide on silica gel. Milligm and Richardson ( 1 7 J ) have studied the magnetic snsceptibilities of the dual hydrous oxide system nickel oxide-alumina, and Amid and others ( 2 J ) have studied the phenomenon of magnetic dilution in alumina and silica gels impregnated with manganese dioxide. The elastic properties of gels have received considerable attention during the past year, and many measurements on a variety of gels under various conditions are available ( I J , S J , ,$J, 9J-14J, 215, 25J). Improvements to existing apparatus for measuring the elastic properties of gels have been niadc by Hastewell and Roscoe ( B J ) , and an absolute method of nieasiiring the rigidity modulus of gelatin gels has been described ( 2 S J ) . In the latter, the grl is formed over mercury in the nide arm of a U-tube (radius r ) . A known air pressure ( p ) is applied to a length ( t ) of the gel, and the rise of mercury ( h ) in the capillary arm (radius a) is measured. The rigidity modulus ( 9 ) is then given by g = pr'/8ta2h, provided that 1 >> r.
March 1956
Other properties of gels receiving attention include coefficients of swelling ( 2 2 J ) and of thermal expansion (1BJ).
Aerosols I.arge numbers of publications relating to the preparation, properties, and applications of aerosols continue to appear. A method of dispersing liquids by the application of an electrical potential to droplets issuing from a capillary tube has been given by Drozin ( I I K ) ,and Amelin and nelyakov ( 1 K )have describcd a technique for regulating the dispcrsity of liquid aerosols prepared by the condensation method. The formation of a vaporosol of amorphous ferric hydroxide has been reported ( 2 6 K ) ,and patents relating to the manufacture of aerosol generators have been filed (d4K, SOK). Several techniques for the sampling of aerosols have been described ( l S K , SdK, S5K, @K), and a number of studies toncerning particle size tlistnbutions have been made. The latter include studies of aerosols of inorganic acids (15K),the theory of size classification of air-borne dust clouds by ehitriation ( 4 2 K ) , the relation betwcen falling spred and partirle 5ixe in dnst clouds (20K,38K, S9K), and descriptions of two light-scattering methods ( I Y K , 2 7 K ) and the diffusion battrry method ( S 7 K ) for the determination of particle size. I n addition, a theoretical study of the light scattering of a polydisperse dust clond has been made by Ellison ( 1 2 K ) . Gibb and others ( 1 4 K )have made an electron-optical euaniination of particles of silica dust and found that the outer layer of the particles is amorphous and is separated from the inner rrystalline core by a layer of minute crystallites. Other electron microscopic studies of aerosols have been reported (BK, d d K , 28K, S 4 K ) , and Rlanson ( 2 9 K ) has made an x-ray diffraction study of d v e r iodide aerosols. The destruction of aerosols has also received some attention. Avy and Raillbres ( & K )have studied the effcctiveness of filter papers for stopping aerosols. Their results are given in tabular form, and a discussion of the factore involved is included. Filtration by fibrous media is the subject of a review by Chen ( 9 K ) , and the removal of aerosols from air streims by wet fiber beds has been studied by Berley and coworkers ( 6 1 0 and of foam6 by Yano and others (44K). Studies on the coagulation of aerosols by foreign vapors are also available ( 2 K , SK, 10K). Two experimental studies of the dktribution of electrical charges in charged aerosols have been reported, and approximately the same conclusions Mere reached by both authors ( I B K , SJK). The numbers of positively and negatively charged droplets were found to be equal, and the distributions of charges on the droplets were found to be in agreement with the theory of statistiral distribution of charge. Other studies on electrically charged aerosols a w e made by Kraemer (25K). A number of publications of specialized topics relating to aerosols r h i c h may be of intrrest include a number of papers presented a t the Symposium on Process and Equipment for Air Pollution Control held a t the 126th meeting of the A ~ I E R I C A N CHEMICAL SOCIETY in New York ( s l K ) ,a review of radioartive aerosok ( b S K ) , a study of the composition of hydroscopir particles in the atmomhere ( 4 1 K ) ,an account of the military aerosol research and development program (40K),a report by the aerosol scientific committee on flammability tests of self-pressurized aerosol containers ( 5 K ) , a description of containers for small quantities of aerosols ( 1 9 K ) ,an analysis of thc reported aeroeol accidents during the period 194i-53 ( 7 K ) , and discussions on aerosol paints (16K), aerosol lublicants ( S I K ) , and odor problems in aerosoh ( S 6 K ) .
Emulsions Stability investigations have been the subject of the greatest number of publications reported in this field. Neogy (161;) has
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FUNDAMENTALS REVIEW studied the effect of electrolytes on the stability and zeta-potentials of water-uylene emulsions using various stabilizers. His results indicate that the most important factor in the stability of emulsions is, as amuld be espected, the strength and conipactness of the film surrounding the dispersed globules. The phase inversion of emulsions has been the subject of a study by Kremnev and KuIbina (14L); oil-in-water emulsions \T ere first broken and then reversed by the addition of increasing amounts of salts. The resulting emulsions were stable but could be broken R ith water. The spontaneous growth of the size of droplets in oil-in-u ater emuhiom to a limiting size distribution aas termed limited coalescence ( S S L ) . A required condition for the phenomenon was the presence of a water-dispersible colloid or finely divided solids of high molecular tccight. The limiting size, nhich was approached exponentially, was proporlional to the oil volume and the colloid partide size and inversely proportional to the concentration of the colloid. A number of studies on the use of various emiilsifying agent8 have been made. Barium sulfate has been used to stabilize both oil-in-water and \+ater-in-oil emulsions of benzene and aqueous solutions of sodium salts of the fatty acids (ZGL). The type of emulsion formed depended on the contact angle of the aqueoiis phase with barium sulfate. For contact angles less than 90" oil-in-water emulsions were formed, but with contact angles greater than 90", water-in-oil emulsions were fornird. Bentonite has also been usrd as the cmnlsifier of both oilin-water (21L) and water-in-oil (g21,) emulsions depending on suitable pretreatment. For the stabilization of the former, the bentonite was treated with acetone-formaldehyde iesin, and for the latter a cation surface-active agent was used. I n view of the work described above it is highly probable that the function of this pretreatment was to change the contact angle of the bentonite with the aqueous phase. Kremnev and KuIbiria have studied water-in-oil emulsions stabilized by alkali oleates ( 1 s t ) and also the effect of the length of the hydrocarbon chain of the stabilizing molecule on the dispersity of oil-in-water emulsions (12TJ). The use of salts of alginic acid as emulsifiers of benzenewater mixtures has been studied by Kovodranov and Tagusheve (17L),and Sanders and coworkers (25L)have described a h j tlrometer method of measuring the stability of emulsions. T h r relation between the dispersity of an emnlsion and the molecular nature of the emulsifier has been studied by Spivakova (69L)in an investigation of the condition of spontaneous forniation of highly dispci se, concentrated emulsions, and Kremnev and Ravdel (16L)have given a theory of the mcrhanisni of emulsification. A theoretical treatment of the development of emulsions created by self-nucleation using the absolute rate theory has been given by Wakeshiina ( S I L ) , and an account of the effect of selective wetting on the formation of emulsions has been given by Dvoretskaya (3.5). VoyutskiK and others (SOL) have studied the mechanism of separation of the disperse phase of emulsions during filtration through fibrous nirdia. They recommend that for the best separation of water-in-oil emulsions the fibrr filters should possews a degree of hydrophility high enough to cause coagulation of t h e water phase but low enough to prevent clogging of the filter. The electrical characteristics of emulsions are dependent only in part on the electrical properties of the components-many other factors such as particle shape anti distribution have important effects (2SL). Howe and Pearce ( 7 L ) have studied the electrical dehydration of tar emulsions, aiid measurements of emulsion viscosities were made by Sherrnari (Z7L, 68L). Preparations of specific emulsions which are of interest include a method of emulsification of sodiuin in inert liquids such as toluene and kerosine (dOL) and the preparation of emulsions of nitroglywrinc in water (2L). A simple method of emulsification, which consists in dropping the liquid to be dispersed slowly into a vibiating wire spiral on the surface of the dispersion me-
608
dium, has been described by Kremnev and Bhranitsova ( I l r J ) , a patent for an emiilsifier has been filed by Wiegand (S$L), and Rose has reviewed the use of ultrasonics in the preparation of emulsions (24L). Attempts to eliicidate the mechanism of emulsion polymerizytion reactions still continue, but a definite thcory has yet to appear. Order of reartion studies on the alkali saponification of polyacrylic ester ( 1 8 L )and of polg(viny1 acetate) (191,) have been made by Okamiira and eoworkere, and both reactions neie found to be of the second order with respect to the concentrations of estei and alkali. The effect of the charge on the colloidal part of soap solution on the rate of polymeiization of styrene in emiilsion has betn studied by Fermor and PeKzner ( h L ) ,and particle counts in several reactions have been made by Wiiitgen 'and Neveling (35L). Yurzhenko and Tsvetkov (361,) have made a theoretical study of the effect of promoters and emulsifiers on the rate of emulsion polymerization and have derived a forrniila for the rate of the reartion. Aiticles devoted to specialized topics thal have appeared during the past year include revieas of drilling eniulsions (5L, S&), skin creams (SL-IOL),the i i s ~of cationic emulsifiers in cosmetics ( 6 L ) , and the development of erniilsifiers for agricultural pesticides (1L).
F0ams The majority of publications in this field h a w been concerned p i t h studies on the stability of foams. Nakashima ( 1 1 M ) has described a new method of measiiring foam stability, and Mokrushin and others ( 9 M )have studied the influence of solid metal carbonates and sulfates on the stability of foams. Pozin and Tiimarkina ( I S M ) found that the heights of t h r foams formed, under standard conditions, by various soap solutions increased with the corresponding surface tensions and viscosities. They further stiidied the effect of gases on these foams and found that they mere depressed by soluble gases but unaffected by insoluble gases (14df). Studies on the foaminess of aqueous solutions of sodium salts of the fatty acids have been reported ( Z M , 1 9 M ) , and the effect of alcohols on the foaminess of soap solutions has been studied by Nakagaki and Shinoda ( 1 O M ) . Epstein and others ( 6 M ) have pioposed a theory of the slow drainage of foams They suggest that the phenomenon is due to an ordered surface structure of considerable rigidity. Severe steric limitations are placed on the combinations that can produce such films. J,ong rhains that readily adlineate favor the process, but widely divergent chain lengths, branching, and the presence of nonterminal functional groups in geneial are unfavorable. Intcresting Iesults have been obtained by Ross and Cutillas ( 1 6 M ) from a study of the transmission of light by stable foams. They found that the fraction of light transmitted increascd rapidly for 30 to 40 minutes after formntion of the foam and thereafter increased slowly. I n the first stages the film consisted of spherical bubbles separated by relatively thick layers of liquid. As this liquid drained away a trausition to a system of polyhedral bubbles separated by thin plane films took place. The slow increase in light lransniission after this transition had finished WRV caused by the diffusion of gas in smaller bubbles a t higher pressures into larger bubbles a t lomeer pressures nith R consequent reduction in interfacial area. A rcview of the usrs of flotation for the concentration of minerals has appeitred ( 4 I f ) , and the use of foams in the separation of colloids has been deseiibed elsewhere ( 1 4 F ) . A number of patents relating to foam-inhibiting agents ( I M , 8M, 1 8 M ) , foam-promoting agents ( 1 6 M ) ,and fire-fighting foams (5Af, 1 2 M ) have been filed, and a study of the physical chemistry of firefighting foams and foaming agents has been made by Chang ( S M ) . Industrial processes for the manufacture of foam glasses have becn dcseribed and reviened by Schulz (17M), and Hubscher ( 7 M ) has discussrd their propelties and structurr. Most foam
INDUSTRIAL AND ENGINEERING CHEMISTRY
Vol. 48, No. 3
COLLOIDS glasses are of the polyhedral type with closed cells. The most important mechanical properties of foam glass are its machinability, its low volume-weight, and high thermal insulation capacity combined .with a relatively high mechanical strength.
Stability of Colloid Systems Coagiilation stridies have again received a great deal of attention, Xharin ( 1 7 X ) has deduced and given an approximate solution of a differential equation for the rate of slow coagiilation, and has proposed a new thermodynamic equation for stable colloidal suspensions. An experimental study of the slow coagulation of arsenic(II1) sulfide sols has bren made by Bhattacharya and Bhattarharya ( 3 N ) by a viscometric method. The time of coagulation %as taken as that at whirh there was a point of inflection in the viscosity-time CUIVC. Teiah and others have continued their noik on the coagulation of hydrophobic sols in statu nascendz %-it11a stud3 of the influence of ionic size and valence of the counterion on the coagulation rate ( 2 7 N ) . I n addition, they have compared the coagulation phenomena of dialyzcd and freshly prepared silver iodide sols (22X). Other coagulation studies have been made on sols of ahimiriuln and iron hydroxides (fS.Y, l&v,.%A7), silver halides ( f S N ) ,arsenic(II1) sulfide ( Y N ) , and tin(1T) oxidc (28-\‘). The flocculation of colloids by mixtures of electrolytes has been studied by Doucet and Watelle (11N). They found that if al and a: are the characteristic flocculation activities for t n o electrolytes and ui and u: their activities in a mixture causing flocculation under the same conditions, then the relation ( a : / a l ) (a;/az) = 1 held for all the systems which they studied and a130 the cases found in the literatim where the activities weIe reported. -4similar equation in terms of concentrations was found to hold only when the valences of the coagulating ions were all the same Sundaram and COM orkers have studied the gelation of a number of systems by a light scattering method. I n the case of sodium stearate in octyl and decyl alcohols, they found that the particles decrcased in size and anistropy during gelation (SA‘), whereafi in the casc of sols of aluminum molybdate and thorium arsenate the size and nnisotiopy of the particles increased (ION). The effect of hydrogen ion conccntration, silica concentration, and t e m p e r s ture on the time of gelation of sols of silicic acid has been studied by Sen and Ghosli (23-V, Z4n’), and hlalik and coworkers have made an extensive study of the sol-gel trandormation of the ferroand ferricyanides of some metals (doh’, $ I N ) . Other studies have been made on the gelation of gelatin (ZN),vanadium pento d e (IZ-V), and others (Q4V, 1 8 N ) , and Sloan has made a comprehensive study of the aging of precipitated barium sulfate and the alum precipitate used in the clarification of trirbid water (26N). The theory of the stability of lyophobic colloids is the subject of a monograph by T’erwey and Overbeek (2RAV),and Dahlgren (SiV) has made a theoretical analysis of the breakdown of thixotropic materials. A study of the “steiir protection” of gold sols by the adsorption of flexible macromolecules was made by Heller and Pugh (15A’). They found that increasing concentrations of polyethylene glycols protected the sols from coagulation by potassium chloride up t o a constant polymer concentration and that the protcctive action increased with the size of the polymer. The stability and thixotropy of montmorillonite suspensions have been studied by BuzAgh ( S N ) , and Vogel and Hahn have reported that suspensions of solids can be stabilized in water by thc product of a reaction between a basic oxide (or hydroxide) and an amphoteric oxide (or hydroxide) or a weak acid such as silkic acid (SON). Xxamplrs of such stabilizing agents are ferrites, aluminates, and chromites of magnesium and calcium. The lyotropic ion series ( I N ) and peptization ( 1 9 N ) have also received some attention, and Vold ( S I N ) has solved the eqna-
+
March 1956
tions for the London-van der Waals forces of interaction between anisometric colloidal particles. She found that the energy varied as T-“, where T is the distanee of separation. The order of attractive energies was found t o be plates > rectangular rods > cylinders > spheres, and n was found to vary in the same tlirection from 3 to 1. I n addition, Bierman has made a mathematical investigation of the electrostatic forces between nonidentical colloidal particles ( 4 N ) .
Kinetic Properties OSMOTIC PRESSURE AND DIFFUSION
-4new method of detcrmining small osmotic pressures has been described which incorporates the osmometer cell into an interferometer system, the osmotic pressure being calculated from observations of thc rate of passage of interference fringes in the system ( 2 2 P ) . High accuracy is claimed for t h e method. -4 new osnionieter designed especially for the study of high polymers has been described (QOP)and also modifications of t w o existing osmometers for the same purpose (I@‘, 64P). A number of reviews of various aspects of osmometry have appeared. Among the more outst:mding of these is a presentation of the subject in modern terms by Hildebrand (4SP). Special emphasis is placed on the concepts involved; thermodynamic, relations are discussed, and the role of entropy in the process is explained and formulated in detail. Mark (SOP) has reviewed the high-temperature osmometry of polymer solutions, and osmosis between an organic liquid and rc-ater or an aqueous solution has been reviewed and applied to colloidal and macromolecular solutions by Duclaux and Cohn (2SP). Errors occurring in osmometry, such as solute permeation and thosc due to adsorption, have also becn discussed and methods of correcting for them suggested ( I S P , 24P). Measurements of osmotic pressures of protein solutions (QP), high polymer solutions (44P, 52P), and polyelectrolyte solutions (/,SP) have been reported, and Wood and Phillips have described some anomalous osmotic pressure results which they have obtained with benzene solutions of certain coal-tar fractions (Q7P). This behavior is manifested by the appearance of a maximum in the osmotic pressure-concentration curve, which tends to disappear a t higher temperatiires. Donnet and Roth (25P) have described a method of preparing osmotic membranes for use with polydisperse poly~ners,in which cellulose membranes, swollen with water, are caused to shrink in a controlled way by treatment with methanol. This also causes t h r pores to shrink, producing impermeability to polymers of low molecular weight. The preparation of semipermeable cellophane membranes and the control of their swelling have been discussed (4P), and T e r a z a m and others ( S S P , 86P) have carried out a series of studies on the formation of semipermeable membranes by wator-insoluble salts. They called them membranes “crystal Reniipermeable membranes,” since they appear to be formed by the gathering of minute crystals into a thin layer in the supporting medium. Only a few diffusion studies on colloidal systems have been reported during the past year. Pakshver and Bykova (74P) have studied the diffusion of sodium hydroxide, methylene blue, and glycerol in aqueous solutions through hydrocellulose films. I n all cases it was found that the rate of diffusion increased with time because of s n d i n g of the membrane. Coefficients of diffusion of electrolytes in agar gels (32P) and polyelectrolytes in salt free solutions ( 6 d P ) have also been reported. SEDIMENTATION AND THE ULTRACENTRIFUGE
A most interesting advance in this Geld has been the description by Beams and others (7P, 8P, 2SP) of an equilibrium ultracentrifuge in which the rotor is magnetically suspended in a vacuum. The rotor is accelerated to operating speed by means of
I N D U S T R I A L A N D E N G I N E E R I N G CHEMISTRY
609
FUNDAMENTALS REVIEW
Figure 2.
Ultracentrifuge with vacuum chamber removed
(8 PI
fields on the rate of diffusion of metallic atoms in and through metals (JOP). Studies on Sedimentation under the influence of gravity have rcceived considerable attention during thc past year. A simple, automatic particle-size analyzer has been described by Yagi (98P). The apparatus automatically records the sedimentation of powders finer than 74 microns. For reliable operation] the density and viscosity of the suspension medium should be such that Stokes’ law holds for the particles. The particle-size distribution is obtained by differentiation of the recorded sedimentation curve. Richardson and Zabi (77P) have studied the effect of concentration on sedimentation and liquid-solid fluidization of uniformly sized particles greater than 100 microns in diameter and found that the effect could be correlated in terms of porosity, the ratio of particle diameter to tube diameter, and Reynolds number. The sedimentation vclocity and diffusion of a solvated substance have been treated mathematically by Cheng (ZOP),and 1300th has carried out a theoretical examination of the electrical effects accompanying the steady fall of solid, charged, spherical particles under gravity in an electrolyte (1dP). A similar examination, together with a discussion of the climination of the eIectroviscous effect in sedimentation, was also carried out by Elton and Hiisrhler (28P). The occurrence and theory of sedimentation of salts in liquids together with new data for 12 inorganic powders in water and in 18 organic liquids, has been discusscd by Wolf and Kurts (95P). The same authors have d s o given an account of the thixotropic (or otherwise) properties of these sediments (96P). Several measurements of viscosities of sedimenting suspensions have been made ( g y p , 4 l P , 67P, 63P), as have measurements of sedimentation volumes of various inorganic powders in a variety of liquids (19P, 47P-49P, 68P). VISCOSITY
a flexible shaft connected to an air turbine. When operating, the shaft is disconnected and the rotor coasts freely during sedimentation, which is observed with a modified Jamin interferometer. The speed of the rotor, which decreases a t the rate of about 1 r.p.s. per 3 days a t a pressure of 10-6 mm. of mercury, can bc determined t o 1 part in 106, the temperature to 1 part in 104,and the fringe shift to 0.03 to 0.05 fringe, which results in a three-significant-figure precision over the entire molecular weight range above 100 when the equilibrium method is used. Other instrumental advances in this field include descriptions of an air-driven, air-floated capillary tube ultracentrifuge ( S I P ) , a centrifuge permitting continous observation of the spinning tube (6dP), and a new electrically driven laboratory centrifuge capable of speeds up t o 20,000 r.p.s. (94P). The use of the ultracentrifuge in the determination of molecular weights has been reviewed in some detail by Frydryck (33P), and reports of molecular weight determinations of various macromolecules (15P, 45P, 65P) and silicotungstic arid ( 1 P ) are available. The possibility of determining molecular weights of colloidal particles by ultracentrifugation in an electric field has been discussed by Schelud’ko (78P),and a method of determining molecular weights and sedimentation constants simultaneously has been described by Klainer and Kegeles (54P). Baldwin has continued his work on boundary spreading in sedimentation 0 t h and Dcsieux have discussed the velocity cxpeiiments (W), correction of sedimentation constants for hydrostatic pressure (7%’P), and Ray and Deason have described some experiments R-ith a sheared boundary centrifuge cell (76P). Cheng and Schachman have described the application of the ultraccntrifuge to the measurement of the conipressibilities of solids ( B l P ) , and Ogston has presented a mathematical treatment of sedimentation and solvation in multicomponent systems ( 7 0 P ) . Other studies involving the use of the centrifuge include a study of centrifugal filtration (73P) and a study of the effects of high centrifugal
610
This year has seen the appearance of a considerable number of descriptions of new viscometers of improvements t o existing viscometers. A detailed description of all of these is out of place here, and since none of them appear to be particularly outstanding, they vi11 only be mentioned by name. The types descrihcd include the Stormer viscometer (ZgP, 98P), the rotational or Couette viscometer (SP, l o p , 11P, 27P, S6P, 69P), thc cone and plate viscometer (58P, 61P), the IIdppler viscometer (66P), the Ubbelohde viscometer (89P), the master viscometer (88P), the torsion viscometer (17P, 8 l P ) , a bar viscometer (86P), electrical viscometers (13P, 4 2 P ) , microviscometers (SBP, gap), a melt viscometcr (5OP), and a stioboscopic viscometer (99P). In addition, the calibration of viscometers in absolute units has been discussed by Weiss (9SP). By an analysis of previously reported data, Orr and Blocker ( U P ) have shown that the viscosity of a suspension of spheres, from the lowest to the highest concentration, can be rcprescnted by a modification of the Einstein equation: q = vo/(l ack) whrre q and 70 are thc viscosities of the suspension and the pure liquid, respectively, c is the volume fraction of the particles, and a and k are constants. Measurements of the viscosities of suspensions of glass spheres have been made by Sweeny and Geckler (84P) who found that their results could be best represented by the relation proposed earlier by Mooney: q / T 0 = exp [3.5c/( 1 k c ) ] where k is a constant and the other symbols have the meaning given above. Mooney and Hermonat (67P) have shown that a better agreement between this relation and euperiment can be obtained in certain cases if a correction is made for the presence of an adsorbed layer of the liquid on the glass spheres. The electroviscous effect has been reviewed in detail by Harmsen and otheis (39P). They pointed out that the phenomenon possessed distinct features that could he related to thc classical electroviscous effect, the apparent volnme increase of
-
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INDUSTRIAL AND ENGINEERING CHEMISTRY
v0i. 48,
,
,
,
,,
NO.
3
COLLOIDS
. . . A remarkable magnetically suspended centrifuge has been perfected the dispersed particles, and higher-order effects caused by the interaction between particles and therefore becoming more marhed with increasing particle concentration. The variation with conductivity of the constant in the Einstein relation for viscosity has been determined for suspensions of carbon spheres in solutions of hydrochloric acid and potassium chloride (59P). In all cases it was found that the constant had a much higher value than the theoretical figure of 2.5 and increased with the conductivity of the suspension. A considerable number of measurements of viscosities for a variety of colloidal systems have been reported. They include measurements on clay suspensions (SOP), colloidal iron silicates (SOP), aluminum soaps (87Z‘), polyelectrolytes (5P, SP), and a wide range of macromolecular solutions (18P, Sap, S8P, 51P, 5 8 P , 75P, 79P, 83P, 912’).
Electrokinetic Properties The majority of publications in this field have been concerned with the varioiis aspects of paper electrophoresis. An extremely comprehensive review and bibliography of the subject has been presented by Hanot (17’Q) and a somewhat smaller review by Ostronshi (31Q). Several improvements t o techniques have been described; these include an apparatus which features cooling and drying of paper in situ (8Q), an apparatus which permits the simultaneous execution of several determinations ( l Z Q ) , an apparatus for automatic coloration and extraction of the paper strips (SOQ), a new migration chamber for which many advantages are claimed (35Q),and a new technique for the hanging-strip method which eliminates the distortion sometimes encountered during drying ( 4 1 Q ) . A new stain for paper electrophoresis-i.e., Light Green SF in place of bromophenol bluehas been suggested by Rideout and Prichard ( S S Q ) . The use of this stain does not require washing of the st,rips with alrohol or their preparation with mercuric chloride. Paper electrophoresis separations of condensed phosphates ( S 4 Q ) and the strychnine alkaloids (Z5Q)have been described, and PuEar (3SQ) has reported that for paper electrophoresis in a moist chamber, the thickness of the electroljte layer ( t ) , the cross sectional area of the paper ( q ) , and the width of the strip ( p ) are related by the equation p = q / t . I n addition to the above, studies on the cffect of electroosinosis on paper electrophoresis ( 4 3 Q ) and electro-osmosis in paper electrochromatography (IOQ,4 S Q ) have been reported. A new electrophoresis cell for dual analysis has been described by Corey and Oreskes (79) and a method of extending the duration of descending-boundary preparative electrophoresis bv two to five times has been suggested by Sorof and O t t (SSQ); thr latter was achieved by interposing a single, large, steep gradient of sucrose- Le., an electrically neutral substancebetween t h e bottom section of the cell and the fraction to be isolated. An interesting variation of the conventional electroseparation technique has been described by Kolin ( S S Q , 33Q). By the combination of a conductivity gradient with a p R gradient ions can be separated according t o their isoelectric pII values instead of their mobilities. The separation of hemoglobin from cytochrome-c was effected in this way. Measurements of zeta-potentials of glass particles (ISQ, 1 4 Q ) , silver iodide sols (16Q1, and the dispersed phase in petroleum eniulsions (30) have been made, and Borisov has discussed the effect of the electrokinttic properties of the surfaces of minerals on their tendency t o undergo flotation ( 4 Q ) . Egerer and Landsberg ( 9 Q )have given a mathematical treatment of electrophoresis and electrosedimentation in nonaqueous suspensions, and their conclusions agreed with experimental data for the alkaline earth
March 1956
carbonates and alumina in organic solvents. The purification of bentonite by an electrophoretic method, in which the iron content is reduced to 0.14%, has been described by Takeuchi (3QQ);Fridrikhsberg and Gutman have studied electrophoresis through collodion membranes (1l Q ) , and Mysels and coworkers have continued their work on tracer electrophoresis (27Q, 38Q). Electrophoretic mobilities of glass particles (SQ), glass and polystyrene spheres ( I Q Q , ZOQ), and soap micelles (37Q) have been measured, and other electrophoretic studies have been made of metalloproteins (5Q,SQ),and tanning materials uranyl salts (IQ), (16Q).
Membrane equilibrium has also received some attention. The properties and uses of permsclective membranes have been reviewed by Melkerson (SSQ), and a similar review by Ongaro deals with ion exchange membranes (Z9Q). The preparation of strong-acid-type collodion-base membranes by casting membranes from collodion solutions containing sulfonated polgstrene was described by Neihof (S8Q). Alternatively the sulfonated polystyrene was adsorbed from aqueous solution onto preformed collodion membranes. The porosity of the membranes and the charge density of the walls of the pores could be varied at will. Kobatake ( H Q ) has presented a treatment of the electrokinetic phenomena and membrane potential by the thermodynamics of irreversible processes based on hydrodynamics, and Koz’mina and Shkodina ( 2 4 Q ) have studied the electro-chemical activity of nigrosine-collodion membranes of various structures and their use in electrodialysis. The distribution of electrolytes across a semipermeable membrane in the presence of arsenic trisulfide sol has been studied by Trivedi and Patani (4OQ), and the permcability of cellophane membranes to sodium dodecyl sufate solutions has been studied b y Harrap and O’Donnel(18Q). They report that on equilibrium dialysis in the presence of salt, sodium dodecyl sulfate does not distribute itself equally across a cellophane membrane when the total concentration is above the critical micelle concentration. They conclude that these results support an earlier hypothesis that the solution inside the dialysis bag contains micelles and single ions, whcreas that on the other side of the membrane contains single ions only.
Surface and Interfacial Tensions and Wetting The surface energies und surface tensions of solids have received more attention than in the past years. Nicolson (S3R) has made calculations of siirfacc tensions in crystals of the sodium chloride type. I n the cases investigated the surface tension was greater than the corresponding surface energy by a factor of about five, and experimental work in support of this resnlt is described. Zadumkin (59R) has adopted Born’s formula for the surface tension coefficients of sodium chloride-type ionic crystals to metals by substituting electrone for negative ions and obtained the formula u = B D / A where D is the density, and A the atomic veight of the metal, and R has the value 7.87 x 103 erg em. The formula agrees with experimental data t o within 5 to 10%. Theoretical considerations of surface energetics together with data from previous experimental determinations of surface energies and new data for sodium chloride have been disciissed by Benson ( 6 R ) . Jones and others (IOR) have reported that the surface energy of atomized sodium chloride is abnormally high, and the basic meaning and significance of interfacial surface forces in the building up of solid materials have been discussed by Auerbach (4R). Sato (39R,4012)found that the lowering of the breaking strength
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FUNDAMENTALS REVIEW of brittle solids--e.g., waxes-with wetting by different liquids varied with the surface tension of the liquid. Kc was able to derive theformula CT~ = - o , / ( A F / F ) , where u,and u8are the surface tensions of the solid and liquid, respectively, F is the breaking strength of the solid, and AF the (negative) lowering of the breaking strength by wetting. A similar equation in terms of Young’s modulus was found t o hold for glass, marblc, porcelain, and other brittle solids (41R, 42R). The surface tensions of liquid metals have also received considerable attention. Taylor (54R) has reviewed several methods for their calculations. Correlation between atomic volume and surface tension yields results which are considerahly lower than those given by other methods, and consequently the valucs are subject to considerable uncertainty. The two mcthods t h a t use heats of sublimation give results that are probably accurate to better than 10%. Figuies are given for the most probable values of the surface tensions of 27 metals a t their melting points ranging from 55 dyne cm.-l for cesium to 2680 dyne cm.-l for tungsten. Calculations of the surface tensions of mercury, arsenic, antimony, and bismuth by a heat of vaporization method have also bccn given by Zadumkin (6OR). A new method for the calculation of surface tensions of liquid metals, based on an analysis of solid state curvatures, has been given by Sangster and Carrnan (37R) and applied to germanium. Two determinations of the surface tension of sodium at its melting point in an atmosphere of argon have been made [Taylor (6322) reports a value of 190.8 dyne rm.-l and Addison and others (1R)a value of 195 dyne cm.-l], and Primak and Quarterman have redetermined the surface tension of liquid potassium (36R). Other surface tension studies on molten solids include measurements on binary alkaline earth borate systems (45R), the effect of dissolved carbon, nitrogen, oxygen, and sulfur on the surface tension of iron (14R),and the effects of sulfates (IUR) and of magnesium oxide (36&)on the surface tensions of molten glasses. With regard t o the experimental measurement of surface tension, an improvement to the oscillating jet method has been suggested by Sutherland (49R)in which the radius and amplitude of the vibrating stream are mcasurcd photographically, and the wave length is determined by using the stream as a series of lenses that focus a point source of light on a photographic plate inclined t o the direction of the stream. -4 new instiument, operating on the principle of the maximum bubble pressure method and with which an accuracy of better than 1 in 200 is claimed, \\as described by Shah and Pathak (44R). Compressed air was forced simultaneoiisly through a stationary tube and first one and then the other of two movable tubes (of different radii) immersed in the test liquid. The apparatus was adjusted so that air bubbled out of the tubes a t the same rate, and the surface tcnsion was computcd from the equation u = Kp(d1 - dz) where K is a constant of the inetrument, p is the density of the liquid, and dl and dz are the depths of the movable tube. A variation of the Wilhelmy technique has been suggested by Guastalla ( I S R ) , and Tawdc and Parvatikar (52R) have published a table for the calculation of surface tension from measurements of sessile drops, in which values of az/rz against h/r in the range 0.5100 to 0.5708 a t intervals of 0 0002 are given. Surface tensions of a number of liquids have been measured, including nitric acid (60R),sulfuric acid (51R),helium (111)( 3 l R ) , solutions of alkali halides in liquid ammonia (47R), barbituric acid solutions (SOR), solutions of alginates (SbR), synthetic glycerides (6R),and members of the honiologous series of paraffins (17R) and of anlines (57R). I n the last piece of work, the surface tensions of the anlines 4ere found t o increase with increasing chain length, whereas the corresponding interfarial tensions against mercury were found to be independent of chain length. An explanation of this phenomenon in terms of interfacial orientation and molecular association is given. Other measurements of interfacial tensions have been reported for the halo-
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genated benzenes against water (28R), the synthetic glyccrides against water (SE), solutions of alginates against benzene (34R), and soap solutions against various alcohols and estets (27R, 68R). The effect of inorganic salts on the interfacial tension a t the watcrmercury interface has been studied by Zeiliger (61R), and Xazi and Desai have continued their work on interfacial tension and complex formation in various binary chloride systenis (21R-25R) and have also studied autocomplex formation in aqueous solutions of copper(I1) chloride by the same method (26R). Empirical equations relating surface tension to temperature (32&),liquid viscosity (46R), and reduced volume of the liquid (5622) have been proposed, and, as i s usual with publications of this type, claims that they are better than eyisting relationships m-ere made. The methods of statistical mechanics have been appiied t o the calculation of density at the liquid-vapor boundary (16R), the surface tension of curved suifaces (29R), and the surface tension betmeen a solution of known composition and a layer not necessarily in equilibrium with it ( 9 R ) . Fordham has also made a theoretical study of surface tension in systems not in equilibrium ( 1 In), and SacrolBa-illathot (3812) has described a method of calculation of the surface tension of scjlutions of molecules of different sizes. A study of the netting properties of organic liquids on high energy surfaces has been made by Fox and others (12R), and, in a publication on wetting behavior as the essence of true capillarity, Schultz (4%) has put forward arguments that capillarity is based on the ability of a liquid to wet the capillary wall and can be explained without the concept of surface tension. Asahara and Goto ( d R , S R ) have continued their study of the relation between contact angles and organic substances on metal surfacee, and a discussion of the factors influencing the magnitude of the contact angle has been given by Valkenburg (55R). The hysteresis of the angle of contact of mercury against steel was shown by Wright to be caused by adsorption on the solid surface, and, in contrast to earlier work, roughness was not found to affect the hysteresis, although the angle of contact was altered (58R) Jech (19R) found that the contact angle between water and a polystyrcne surface was progressively decreased by exposure of the surface to x-rays. No suck effect was observed in a vacuum, and so he concluded that the phenomenon was due t o the formation of ionized air a t the surface. The angle of contact of a moving tungsten wire u i t h mercury was found to vary periodically, thus suggesting, according to Cook and Stone ( 8 R ) ,a nonlinear functional contact force. Other measurements of contact angles have been made by Studebaher and Snow of mater on a series of carbon blacks (4822). A s is alrcady known, the rate of spread of a drop of liquid on a plane horizontal surface is not in accordance with prcsent theories. This anomolous behavior has been attributed by Bielak and coworkers ( 7 R ) to the existence of very thin films extending well beyond the liquid drop, and in support of this view they quote a number of interesting experimental observations. The term “autophobic” has been assigned by Hare and Zisnian (25R)to a class of polar liquids which were found t o have the property of being unable to spread on their own adsorbed films. They attributed this property to the formation, by adsorption, of an oriented monolayer of the liquid having a critical suiface tension lower than the surface tension of the liquid. For surh liquids, a rectilinear relation was found to exist between the cosine of the contact angle of each liquid and the surface tension.
Optical Properties LIGHT SCATTERING
Theoretical aspects of light scattering continue to attract a great deal of attention, Chin and others (85)have derived an integral formula which enables particle sizc distribution in
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COLLOIDS polydispm se suspensions to be computed from transmission measurements of various values of the forward scattering halfangle. Three possible experimental techniques mere disrussed, and in a later paper (9S),experimental results for a polydispeise suspension of glass spheres in water were given. The results nere in good agreement mith the theory. A comprehensive theoretical investigation of the steady state scattering and absorption of elcctromagnetie radiation by dense dispel sions as madc hy Chi1 and Churchill (108). E\perimental confirmation of their analjsis for the case of a dispcision of finite thickness but infinite lateral dimensions has been given by Scott and others (3bS). Keber (408) has made a theoretical study of thr effrct of particlr orirntation of rod-shaped dipoles in an electiic ficid on the intensity of scattered light. The effect n w found to be strongly dependent on the particle length and should be detectable under favorable conditions. Charge effects in light scattering by colloidal particles waa the subject of a short note by Piins and Hernians (SOS), and Cantow has desoribed two methods of obtaining the dependence of lateral scattering on the length and angle of incidenre in the case of large particles (6s).A theoretical discussion of the Einstein-Smolnchomsl,i theoi y of light scatteiing has been given by Hutchinson and Mehose, and it W R Y shown that a more general tieatment of thc throry than that of Debye leads to results which conform well with the behavior of solutions of association colloids (218). The diffiaction approsinlation and exact Mie theory have been compared for difterent sizes of partic,les by Davies (12S), and two rupei iinental confirmations of M e ' s theory have been reported (??OS, 248). A considerable number of light-scattering studies on a variety of colloidal systems have been niade. These include measurements on solutions of soaps (358, S S S ) , poly (methylmethacrylic acid) ( S S S ) , macromolec~iles ( 1 7 8 ) , and sodium dodecyl sulfate ( 2 9 ~ 7 ) ~ suspensions of polystyrene partirlrs (SS), fibrinogen (CS), barium sulfate and lycopodium powders (25S), and casciri particles (158); silver iodide sols (34s);gel-forming systems (25, 5iV, 9Ar, lox);aerosols (18K, 17K, 2 7 K ) ; and milk ( 3 6 s ) In addition to the above described work, several instrumental advances have been reported. The most noteworthy of these is an apparatus for the measurenient of light scattering which has an angular rcsolution of 0 0 2 " in the range 0.05" to 140". Particles in the size range 0.1 to 100 microns can be characterized (25). An apparatus designed especially for the study of solutions of macromolecules has been described (@S), and SedlBEck has suggested se.reinl simple light scattering methods suitable for the routine measurement of molecular w i g h t s and particle size distributions in industrial laboratories (338). A new apparatus for the determination of molecular weights by light scattering has been desciihed b\r Harvey and Cleverdon ( I S & ' ) ,and Mastrangelo and coworkers have proposed a method of evaluating the reliability of routine molecular weight measurements made by light scattering methods (268, 2 7 8 ) .
Particle Size Determinations Particular attention is directed to the Rrztiih Jouinal of Applzed Physics, Supplement 3, which is devoted to the physics of particle size analysis and contains over 30 papers on man) aspects of the subject (12'). Reference has already been made in other sections to some of these papers, and, in addition, other studies on partirle size analysis have been described in the sections on lyophobic colloids, aerosols, kinei ic properties, optical properties, and electron microscopy. Nassenstein ( 7 T ) has reviewed the prescnt available types of equipment for particle size analysis, including dispeisoid analysis, analysis with air or liquid streams and automatic size analysis of microscopic preparations or photomicrographs. Mnkherji and Bnnerjee ( 6 T ) have determined the size of sodium chloride rrystals by studying the rate of their solution as a fiinction of particle diameter, and their results agree with air permeability measurements. Two new methods for the determination of powder dispersions have been described (ST), and MariEid has shown that dispersion analyses with the Andreasen pipet give results in agreement with other methods ( 5 T ) . Particle size distributions by the turbidity method have also been reported (bT, 4Tj.
Thin Films and Solid Surfaces
OTHER OPTICAL PROPERTIES
Optical studies of a variety of surfaces and thin films have been reported. Metz (288) has described several types of optical apparatus for the study of surfaces, and Scott (318) has reviewed the basic optical properties of single layer thin films, both metal and dielectric, x i t h particular reference to their optical constants. DiffereiiceR betn ecn their properties and those of the bulk material are discussed, and in case of metallic films, the Garnett theory is shovin t o give a satisfactory explanation. Harris and Loeb have described the use of the electronic digital computer, 'VC'hirlwintl I, in the evaluation and analysis of optical constants of thin films as functions of transmission and reflectance data (185). Studim on the optical properties of thin films of calcium fluoride (429, tantalum oxide ( 7 S ) , and cadmium sulfide (165) have also heen reported.
March 1956
The structure of the surfaces of various organic liquids has been studied by Kizel (23255) by a light reflection method, and Tockstein and Dvokik (375) have described an apparatus and procedure for measuririg the intensity of elliptically polarized light reflected from a unimolecular surface layer as a function of the degree of compression of the layer. Resnlts for palmitic arid on water show a hysteresis effect analogous to the hysteresis in the surface pressure-area curves. The Orientation of unimolccular layeis of hemin on mater and on fused silica was studied optically by Diibouloz and Hinaldi (138, 148). They found that, the differences of the angles of inridence for maximum polarization for pure water and u-ster covered mith a unimolecular hemin lnyer were constant for a given wave length, indiratiny that the orientation of the hemin layer was always the sanie. In thc case of hcmin layers on silica, t h r differencrs were not found to be constant, indicating a nonreproducihle oiientation ~vliichthey attiihuted to lack of effect of the hydrophilic gr_oups. Streaming hirefiingenre has received some attention. CopiE has described a variation of the Couette-type apparatus for its measurement (IlSj, and Kahn and Lewis ( Z R S ) have iisrd the method to determine the particle size of sodium montmorillonite particles in s:ispension, assuming them to be oblatc spheroids. Other optical studies of colloidal SL stems inrlnde a discussion of of the electrical-optical effects in liquid crystalline solutions of colloidal electrolytes (418) and an application of Beer's law to colloidal suspensions ( I S ) . I n the latter study a theory was developed showing that the absorptivity of a colloidal suspension of fixed thickness is a linearly decreasing function of increasing roncentration.
The preparation, properties, and structure of evaporated metal films havc been reviewed by Allen (IU)and the magnetic properties of metal films by Colombani (14Uj. Another extensive reviemv by Papbe is concerned with the relation between the surfare properties of substances and their catalytic activities ( 3 4 U ) . Il'Chenko (27U) has described the preparation of free (without substrate) metal films; the metal is evaporated onto celluloid, and then to prevent rupture duringremoval theouter rim is made thicker and a thin coating of ammonium chloride, which is latcr removed, is deposited by sublimation in a vacuum. Other descriptions of methods of preparation of thin films are concerned plutonium and uranium (18U), and with barium titanate (16U), plastics (36Uj. Several techniques for investigating thin films and surface layers have been described, including interferometric
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FUNDAMENTALS REVIEW methods (4U, bU, S l U ) and a radiotracer method ( S 6 U ) , and electron microscopic techniques are dealt with in the appropriate section. Holt and King ( S S U ) have reported evidence in support of the view that an incomplete monolayer of silicic acid is present on the surface of silica, and Cario and Kallweit (11 U ) have investigated the growth mechanism of thin films and have interpreted their results in terms of the adsorption theory of Frenkel. Physicochemical properties of the electrical double layer on planar surfaces have been investigated by Bolt ( 6 U ) , and Nandy (52U) has described a rapid graphical method for the estimation of the thickness of evaporated metal films. >!any workers have studied thin films by electron diffraction methods; included among these are thin films of aluminum ( 1 5 U ) , antimony (42U), bismuth ( f O U ) , copper ( S S U , 41 U ) , lithium fluoride (dZU),silver ( 7 U , SOU, 2bU, 4 l U ) , and oxide films on iron and iron alloys (81 U ) . X-ray studics have also received some attention; I,i and Smoluchowski (SOU) have pointed out that submicroscopic irregularities on a solid surface should show up by their effect on small-angle scattering as they may be regarded as particles on a solid substrate, and calculations of intensity effects show them to be observable. Other x-ray studies of thin films were devoted to indium ( 4 3 U ) and selenium ( S S U ) . Electrical studies on thin films of indium oxide ( S g U ) , germanium ( l a U , I S U ) , and tin ( 1 9 U , S Q U ) have been made, and Kaganov and Azbel have derived an expression relating the conductivity of a thin film to that of the massive metal ( S Q U ) . Heat effects on thin f i l m include studies on films of copper (sU, S U , i 7 U , MU),molybdenum disulfide ( S T U ) , silver, gold, and platinum on glass ( 3 U ) , and iron, cobalt, and nickel ( 2 5 U ) . Other studies of thin films and surfaces deal with colloidal and surface phenomena in the preparation of cathode-ray scrcena (&u),crystallization and conversion of thin film of hydroxides ($8U), the disturbance of chemical equilibria in surface layers (873, the effect of surface films on the polarizing angles of pyrite, coal, and fluorspar (40V), and measurements of the magnetization curves of thin ferromagnetic films (9U).
Structure of Colloids and Electron Microscopy
impurities. Several applications of “reflection” electron microscopy have appeared. For example, fibers (W, W ) ,metal surfaces (9V), and oxide films ( 6 V ) have been so examined. Other applications of conventional electron microscopy have included an examination of the following colloidal materials: thin metal films (IiTi), replicas of clays (4V),aluminas ( f d V ) , etched glass surfaces ( f S V ) ,magnesium oxide ( 7 V , 8V), lead azide ( f O V ) ,and latex dispersions (1V ) .
Bibliography GENERAL
(1) “Adhesion
and Adheeives: Fundamentals and Practice.” Wiley, iVew York, 1954. ( 2 ) Block, R. J., Durrum, E. L., Zweig, G., “Paper Chromatography and Paper Electrophoresis,” Academic Press, Xew 2-0i-k, 1954. (3) Chem. Eng. News 33, 3178 (1955). (4) Cor, P., “Emulsions, hlousses, Detersion, Ides Phenomenes de Surface,” Dunod, Paris, 1955. (5) Emmett, P. H., “Catalysis, 11. Fundamental Principles.” Pt. 2, and “Catalysis 111. Ilydrogenation and Dehydrogenation,” Reinhold, New York, 1955. (6) Hauser, E. A., J . Chem. Educ. 32, 2-9 (1955). (7) Holmes, 11. N., Ibid., 31, 600-2 (1954). (8) Jirpensons, B., Straumanis, 51. E., “A Short Textbook of Colloid Chernistry,’’ Pergamon Press. London, 1954. (9) liitchener, J. A., J . Oil & Cdozrr Chemists’ Assoc. 37, 35577 (1954). (10) Krause, A,, WiadomoscI Chem. 8, 374-81 (1954). (11) Kruyt, 11. R., Overbeek, J. Th. G., “Inleiding tot de Physische Chemie, de Kolloidchemie in het Bizonder voor Biologen en Xledici,” 14th ed., H. J. Paris, Amsterdam, 1954. (12) hlcBain, M. E. L., Hutchinson, E., ‘‘Solubilization and Related Phenomena,” Academic. Press, Kew York, 1955. (13) Reitstotter, J., Kolloid-Z. 139, 1-11 (1954). (14) Tragnell, B. A I . W., “Chemiiorption,” Academic Press, Sew York, 1955. (15) Zocher, H., Kolloid-2. 139, 81-5 (1954). ADSORPTION APPARATUS
(1A) Bering, B. P., Serpinekii, V. V.,Doblady Akad. h’auk S.S.S.R.
The topics of structure of colloids, gel structure, and electron micrclscopy were treated extensively in last year’s review ( 2 3 2 ) and, hence, are only considered very briefly here. Cosslett (517) has reviewed recent developments in electron microscopy. Suito and Takiyama ( 1 S V ) have examined Bikini ash by electron microscopic methods and suggest that it is mainly calcite, formed originally from aragonite which was decomposed at high temperatures into calcium oxide, thc latter reacting with carbon dioxide in the atmosphere to form calcite which occluded radioactive
94, 497-500 (1954). @A) Bowers, R., Long, E. A., Rev. Sci. Instr. 26, 337-41 (1955). (3A) Day, A. G., Rept. Brit. EZect. Research Assoc. L/T292, (1953). (4A) Dillon, J. A., E’arnsworth, H. E., J . Chem. p h y s . 22, 1601-5 (1954). (5A) Gregg, 6 . J., J. Chem. Sac. 1955, 1438-9. (6A) Van Nordstrand, R. A. (to Sinclair Research Laboratories, Inc.), U.6. Patent 2,692,497 (Oct. 26, 1954). (7A) Valdman, M. H., RIcIntosh, R., Can. J. Chem. 33, 269-78 (1955). (SA) Wilson, XI. K., Rev. Sci.Ins2r. 25, 1130-1 (1954).
Progress toward more rigorous theory and penetrating experimentation has characterized the field of colloids and surface behavior again during the past year. Thus, studies of lyophilic colloids reflect the recent accomplishments in the physical chemistry of high polymers; those of lyophobic colloids, the recent substantial advances in understanding of the forces between particles and influence of environment on stability. I fExciting prospects of future progress in elucidating the behavior of surfaces of porous solids such as catalysts are provided by the recently initiated spectroscopic studies of adsorbed molecules. Here for the first time if appears possible to study gas-solid interfaces on molecolar scale.”
M. W. TAMELE Associate Director of Research Shell Development Co.
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Vol. 48,No. 3
COLLOIDS ADSORPTION ISOTHERMS
(1B) Addison, W. E., Barrer, IZ. >I J. ., Chem. SOC.1955, 757-69. (2B) AleskovskiI, V. B., T r u d y Leningrad. Tekhnol. Inst. Lensozeta, No. 27, 29-45 (1953). (3B) Aston, J. G., Tykodi, AI., Steele, W. A., J . Phya. Chem. 59, 1053-7 (1955). (4B) Bagley, E. R., Long, F. A , , J . Am. Chent. SOC.77, 2172-8 (1955). (5B) Baker, hl. Alcl)., Kideal, E. K., Nature 174, 1185-6 (1954). (6B) Barrer, R. M., LlacLeod, D. AI., Trans. Faraday SOC.50, 980-9 (1954). (7B) Barrer, R. M., Rees, L. V., Ibid., 50, 852-63 (1954). (8B) Baughan, E. C., Jones, A. L., Stewart, K., Proc. Roy. SOC. (London) A225, 478-504 (1954). (9B) Bering, B. P., Serpinskii, V. V., RulE. Acad. Sci. U.S.S.R , Dzz. Chem. Sci. 1953, 851-9. Bering, B. P., SerpinskiI, V. V., Problemy Kinetiki i Kataliza 7, Statisticheskie Yadeniya v Geterogen. Sistemakh, 383 -409 (1949). Bonch-Bruevich, V. L., Zhur. Fiz. K h i m . 27, 960-7 (1953). Briegleb, G., Scholze, H., Monalsh. 85, 731-58 (1954). Dell, R. M.,Stone, F. S., Trans. Faraday SOC.50, 501-10 (1954). Dreving, V. P., Kiselev, A. V., Likacheva, 0. A., Doklndy Akad. N a u k S.S.S.R. 82,277-80 (1952). Dubinin, AI. AI., Zaverina, E. D., Bull. Acad Sci. Z7.S.S.R.. Diu.Chem. Sei. 1954, 17680. Dubinin, h l . &I., Zaverinn, E. D., Magvar Tudoinanyos -4kad. Kem. Tudomanyok Osztalkyanak Rozlemenyei 5, 35-42 (1954). Dubinin, hl. M., Zaverina, E. D., Serpinskii, V. V..J . Che??l. SOC. 1955, 1760--6. Enderby, J. A., Trans. Faraday Soc. 51, 106-16 (1955). Everett, D. H., I n d . chint. belge 20, 257-66 (1955). Freeman, XI. P., Halsey, G. D., Jr., J . Phus. Chem. 59, 181-4 (1955). Garbntski, U., Folman, hl., J . Chenz. Phys. 22, 2080 (1954). Graham, G., J . Phys. Chem. 58, 869-72 (1954). Green, R. W., Ang, K. P., J . Am. Chem. SOC. 75, 2733-6 (1953). Gross, J. H.. Bauer, W. €I.,J . Phys. Chem. 58,877-80 (1954). Gtibeli, O., Stori, hl., Helv. Chim. Acta 37, 2224-30 (1954). Hill, T. L., J . Phys. Chem. 59, 1065-7 (1955). Honig, J. M., Ann. -V. Y . Acad. Sci. 58, 741-97 (1954). Honig, J. At., Rosenbloom, P. C., Can. J. Chem. 33, 193--202 (1955). Iwakami. Y . ,J . Chem. SOC.Japan, Pure Chem. Sect. 75,1101-3 (1955). Karnaukhov, A. P., Kiselev, A. V., Khrapova, E. V., Doklndy A k a d . Nauk S.S.S.R. 92, 361-4 (1953). Ibid., 94, 915-18 (1954). Keier, N. P., RoginskiI, S. Z., Problemy Kinetiki i Katoliza 7, Statistieheskie Yaeleniya v Geterogen. Sislem,akh (1949), pp. 4 10-35. Keii. T., J . Chem. Phys. 22, 1617-18 (1954). Kington, G. L., Laing, W., Trans. Faraday SOC.51, 287---98 (1955). Kirsch, F. W., Kreiger, K. A,, J . Am. Chem. SOC.76, 4778-82 (1954). Kinelev, A. V., Krasil'nikov, K. G . , Soboleva. I,. N.. DokEady Akad. N a ~ S.S.S.R. k 94, 85-8 (1954). Kiselev, A. V., Kulichenko, V. V., Ibid., 93, 1014(1953). Krishnamurti, K., Research Corr., Suppl. Research (London) 7, (No. 4),925-6 (1954). Kruyer, S., Koninkl. Ned. Akad. Weteneschap. Proc. B58,73-7 (1955). Kwan, T., Bull. Chem. SOC.J a p a n 27, 69-70 (1954). Kwan, T., Freeman, M. P., Halsey, G. D., Jr., J . Phys. Chem. 59, 600--3 (1955). Landsberg, P. T,, J . Chem. Phys. 23, 1079-87 (1955). Lanyon, M. A. H., Trapnell, B. 11.W., Proc. Roy. SOC. (London) A227, 387-99 (1955). Law, J. T., J . Phys. Chem. 59, 67-71 (1955). Ibid., pp. 543-9. Lam. J. T., Francois, E. E., Ann. h'. Y . Acad. Sci. 58, 925-36 (1954). Loebenstein, W. V.,Deitz, V. R., J. Phys. Chem. 59, 481-7 (1955). Man'ko, N. AI., Levin, V. I., Imest. Al;ad. N a u k S.S.S.R. Otdel. Khina. N a u k 1953, 409-18; Bull. Acad. SA. U.S.S.R., Diu. Chem. Sci. 1953, 371-8. Medek, J., Paliria 34, 292-8 (1954). Mignolet, J. C. P., BtdZ. soc. Toy. sci. Lidge 23,422-5 (1954). Myles, W. J., Reiss, IT.,J . Polymer Sci. 1 5 , 243--62 (1955).
March 1956
(52B) Kagasawa, S., TBhokv J . Agr. Research 4, 75-95 (1953). (53B) Orchiston, H. D., Soil Sci. 79, 71-8 (1955). (54B) Ole, F., Moulton, K. TV., Trend h'ng. Z'niv. Wash. 7 (KO I ) , 24-9 (1955). (5533) Ovcharenko, F. D., XeImark, I. E., Slinyakova, I. B., Bykor. S.F., Dopovidi Akad. Nauk L'kr. E.S.R. 1952, 447-51. 15bB) PaDQe.D.. Bull SOC. chim. France 1955. 14-35. (57Bj Poiyakova, h l . hI., Tesner, P. A,, Doklady Akad. N a u k S.S.Jqs.R 93, 855-8 (1953). (58B) Iiazouk, R. I., Mikhail, R. S., J . Phys. Chem. 59, 638-40 (1955). (59B) Regak, S . Y., Smirnov, S . I., Zhur. Priklad. Khina. 28, 2G2 -7 (1955). 460B) Reyerson, L. H., Peterson, L., J . Phys. Chem. 59, 1117-18 (1955). (61B) Ross, S., Clark, H., J . Am. Chem. SOC.76, 4291-7 (1954). (F2B) Baito, T., hlaruya, K., B d . Research Inst. Mineral Dressing and Met. ( J a p a n ) 8, 141-8 (1952). (63B) Sastri, M. V. C., Viswanathan, T. S., J . A m . Chem. Soc. 77, 3987-71 (1955). (64B) Shelechnik, AI. M.,J . A p p l . Chem. U.S.S.R. 26, 93--4 (1953). (65B) Sing, K. S. W., Nadeley, J. D., J . A p p l . Chem. (London) 4, 365---8(1954). (66B) Steele, W. A., Univ. Microfilnrs (Ann Arbor, Mich.) Publ. KO.10,013; Dissertation Abstr. 14, 1941-2 (1954). (67B) Steele, W. A,, Halsey, G. D., Jr., J . Phys. Chem. 59, 57-65 (1955). (68B) Teichner, S. J., Morrison, J. A , , Trans. Faraduy SOC.5 1 , 961-6 (1955). (69B) Tevosov, S.P., Trudy Inst. Khini. Akad. Nauk Amrbaldzhan. S.S.R. 13, 29-36 (1954). (;OB) Timofeev. D. P.. Zhur. Piz. Khim. 27. 1642-9 (1953). i i l B j Vol'kenshtein, F. F., Bull. Acad. Sei. U.S.S:R., Diu. Chem. Sci. 1953, 701-5. (72B) Vol'kenshteyn, F. F., Zhur. Fiz. Khim. 8, 422-32 (1954). (73B) Voltr, S. E., Weller, S. TV., J . Am. Chem. SOC.76, 4701-3 (1954). (74B) TF7ebb,-4. N.,Eischens, R . P., Ibid., 77,4710-13 (1955). (75B) Wellcr, S. W., Voltz, S. E., Ibid.,76, 4695-4701 (1954). f76B) Yamamura, EI., Nnmano, K., J . Sci. Hiroshima Univ., Ser. -4 18, 113-17 (1954). (7TB) Zel'dovich, Y. B., Problemy Kinetiki i KataEiza 7, Statistickskie Y a d e n i y a v Geterogen. Siatemakh, 238-47 (1949). (78B) Zettlemoyer, A. C., Chessick, J. J., Chand, A., J . Phya. Chem. 59, 375-8 (1955). (i9B) Zettlemoyer, A. C., Yu, Y. F.,Chessick, J. J., Ibid., 59, 58892.
APPLICATION OF ADSORPTION ISOTHERMS
(IC) Bagg, J., Tompkins, F. C., Trans. Paraday SOC.51, 1071-80 (1955). (2C) Barrer, R. M., I b i d . , 50, 1074-7 (1954). 13CI Beebe. R. 4.. Dell. R. M..J . Phvs. Chem. 59. 746-54 (1955). (4Cj Boer, J. H., de, Kruyer, S., Koninkl. Ned. Akad. Wetinschap. PTOC.B58, 61-72 (1955). (5C) Channen, E. W., McIntosh, R., Can. J . Chem. 33, 172-83 (1955). (6C) Clark, E., J . Phys. Chem. 59, 1068-9 (1955). (7C) Corrin, M. L., Ibid., 59, 313-17 (1955). (SC) Corrin, M.JJ., Rutkowski, Ibid., 58, 1089-90 (1954). (9C) Dell, R. M., Beebe, R. A., J . Phys. Chem. 59, 754-62 (1955). (l0C) Deryagin, B. V., Zorin, Z.hf.,DokEady Akad. Nauk S.S.S.R. 98, 93-6 (1954). (1lC) Drain, L. E., Science Progr. 42, 608-28 (1954). (12C) Eischens, R . P., Pliskin, UT.A., Francis, S. A., J . Chem. Phys. 22, 1786-7 (1954). (13C) Everett, D. H., Whitton, W. I.,Proc. Roy. SOC.(London) A230, 91-110 (1955). (14C) Flood, E. A., Can. J . Chem. 33, 979-1001 (1955). 115'2) Healev. F. H.. Yu. Y. F.. Chessick, J. J.. J . Phus. Chem. 59. 399-402 (1955). (16'2) Kwan, T., Ibid.,59, 285-6 (1955). (17C) Kwan, T., Fujita, Y., Kagaku 24, 573-4 (1954). (1SC) Le Bot, J., Le hlontagner, S , J . phys. radium 16.79-80 (1955). (19'2) l b i d , pp. 163-4. (20C) Lukesh. J. S., J . Phys. Chem. 59, 669-670 (1965). (2lC) Melkonian. G. A,, Reps, B., 2. Eiektrochem. 58,616-19 (1954). (22c) Millard. B., Caswell. E. G., I,eger, E. E., Mills. D. R., J . Phys. Chem. 59, 976-8 (1955). (23C) Llilligan, R. O., AIil1, G. S., IWD.ENG. CHEM. 47, 614-25 (1955). (24C) Pace, E. L., Dennis, K. S., Greene, S. A., Heric, E. L., Can. J . Chem. 33, 245-50 (1955).
INDUSTRIAL AND ENGINEERING CHEMISTRY
615
FUNDAMENTALS REVIEW (25C) Reyerson, L. II., Brand, R. A., J . Phys. Chem. 58, 873-6 (1954). (26C) Schriebor, I€. P.,;McIntosh, R., Can. J . Chem. 32, 842-57 (1951). (27C) Singleton, J . II., Halsey, G. U.,J r . , Ibid., 33, 184-92 (1955). (28C) Tykodi. K. J., J . Chem. Phys. 22, 1647-54 (1954). (29C) Tykodi, R. J., J . Phys. Chern. 59, 383 (1955). (30C) Uhlig, 11. H., Ann. N . Y.Acad. Sci. 58, 843-54 (1954). (31C) Vines, It. G., Revs.Pure and A p p l . Chem. (Australia) 4, 207-34 (1954). (32C) Young, D. AI., Trans. Faraday SOC. 50, 83841 (1954). PORE SIZE A N D SURFACE AREA
(1D) Allen, J. A., Haigh, C. J., J . A m . Chem. SOC.76,5245-7 (1954). (2D) Avgul, N. N., Dshigit, 0. I[.,Kiselev, A. V., Zhzcr. F i z . K h i m . 29, 316-26 (1955). (3D) Barrer, R. M., Brit. J . A p p l . Phys., Szcppl., KO.3, S41-S49 (1954). (4D) Ibid., pp. S49-S55. (5D1 Bass, A. S..Sternberg, H. RI., Anal. Chem. 27, 808-9 (1955). (6D) Benson, S. W., Riccardson, R. L., J . Am. Chem. Soc. 77, 2585-90 (1955). (7D) Boutillon, G., Prettre, AI., Compt. rend. 240, 1216-18 (1955). (8D) Brussot, II., I.,eRat, B., Makki, N., A n n . chim. ( P a r k ) 9, 477-506 (1954). (9D) Carruthers, T. G., Gill, R. hf., Trans. Brit. Ceram. SOC.54, 59-68 (1955). (10D) Coutts, J. R. H., Brit.J . A p p l . Phys. 6, 90--1 (1955). (11D) Dacey, J. R., Thomas, D. G., Trans. Faraday SOC.50, 740-8 (1954). T . Khim. 28, (12D) Dobychin, D. P., Andrew, Y. K.,Z ~ ~ LPiz. 1405-.-71(1954). (13D) Dubinh, M. M., ProblemV Kinetiki i Kataliza, A k a d . Nauk S.S.S.R., Inst. F i t . K h i m . , 5 , Metody Izucheniya Katalizatora 213-29 (1948). (14D) Dubinin, M. M., Quart. Revs. (London) IX, 101-14 (1955). (15D) Dubrow, B., Nieradka, If., Anal. Chem. 27, 302--5 (1955). (16D) Folman, M., Shereshefsky, J . L., J . Phys. Chem. 59, 607-10 (1955). (17D) Imelik, B., hfathieu, M . V., Prettre, M.,Teichner, S., J . chim. phys. 51, 651-62 (1954). (18D) Kamack, €1. J., Anal. Chem. 26, 1623-30 (1954). (19D) Landt, E., Kolloid-Z. 139, 170-1 (1954). (20D) Langemann, IT.,Chem.-1ng.-Tech. 27, 27-32 (1955). (21D) hfacIver, D. S . , Emmett, P. II.,J . Phys. Chem. 59, 1109-10 ( 1955). (22D) Nikitin, E. N., Doklady A k a d . Nauk S.S.S.R. 89, 1053-6 (1953). (23D) Ibid., 90, 591-4 (1953). 124D) Nishimura, K., Saito, EI., Morita, N., J . Chem. Soe. J a p a n , I n d . Chem. Sect. 58, 5-7 (1955). (25D) Stromberg, R. R., J . Research Natl. Bur. Standards 54, 73-82 (1955). (26D) Trapnell, B. M. W., Trans. Faraduy SOC.51,368-70 (1955). (27D) Utsugi, H., J. C h e n . SOC.J a p a n , Pure Chem. Sect. 75, 631-3 (1954). (28D) Ibid., pp. 1126-30. (29D) Voigt, E. 31..l’omlinson, R . E., Can. J . Chem. 33, 21531 (1955). (30D) Walker, P. I,.,Jr., Rusinko, F., Jr., J . Phys. Chem. 59, 1106-7 (1955). (31D) Walker, P. Id., Rusinko, F., Jr., Rnats, E., Ibid. 59, 245-9 (1955). ADSORPTION
INVOLVING
LIQUID INTERFACES
( l e ) Aenlle, E. O., Mdm. services chim. itat (Paris) 38 (h-o. 2), 139-46 (1953). (2E)Allan, A. J. G., Alexander, A. E., Tra71.s. Faraday SOC. 50, 863--.73(1954). (3E) Archer, R. J., La Mer, V. K., Ann. N . Y . Acad. S c i . 58, 80729 (1954). (4E) Archer, R. J., La Mer, V. K., J. Phys. Chem. 59, 200-8 (1955). (6E)Banks, W. H., Nature 174, 365--6 (1954). (6E) Bering, B. P., Ioneva, K. A., Doklady A k a d . N a u k S.S.S.R. 93, 85-8 (1954). (7E) Bering, B. P., Ioileva, K. A., I a e s t . A k a d . N a u k S.S.S.R., Otdel. K h i m . Nauk 1955, 9-16. (8E) Ibid., pp. 216-23. (9E) Bersins, T., Delahay, P., J . Phys. Chem. 59, 906-9 (1955). (10E) Blackburn, A., Kipling, J. J., J . Chem. SOC.1954, 3819-23.
616
(11E) Ibid., 1955, 1493-7. (12E) Bring, G. G., Jernkontorets Ann. 138, 671-701 (1954). (13E) Caruso. S. C., Uniu. Microfihns (Ann Arbor, hlich). Publ. No. 9963, Dissertation Abstr. 14, 2207-8 (1954). (14E) Chipalkatti, H. R., Giles, C. II., Vallance, D. G. M., J . Chem. SOC.1954, 4375-90. (15E) Cockbain, E. G., Trans. Faraday SOC.50, 874-81 (1954). (16E) Davies, J. T., Rideal, E. K., J . Colloid Sci., Suppl. No. 1 , 1-8 (1954). (17E) Dickey, 3’. H., J . Phys. Chem. 59, 695-707 (1955). (18E) Dixon, J. K., Judson, C. M., Salley, D. J., PubE. Am. Assoc. Adbance. Sci., Monomol. Layers 1951, 63-106 (Pub. 1954). (19E) Dryden, C. E., Kay, W. B., IND. ENG.CHEM.46, 2294-3000 (1954). (2OI:) Ellis, S. C., Idantham,A. F . , Pankhurst, IC. G. A., J.Sci. In.dr. 32, 70-3 (1955). (21E) F’lton, G . A. II., J . Chem. SOC.1954, 3813-18. (22b:) Franklin, T. C., Sothorn, R. D , J . Phys. Chem. 58, 951-3 (1954). (23E) Gerovich, hf. A., Doklady A k a d . N a u k S.S.S.R. 96, 543-6 (1954). (24E) Ghosh, B. N., Rakshit, 9. C., J . I n d i a n Chem. Soc. 31, 817-21 (1954). (25E) Giles, C. H., Mehta, 13. V., Stewart, C. E., Subramanian, 11. V. H.,J . Chem. SOC.1954,4360-74. (2GE) Graham, D., J. Phys. Chem. 59,896-900 (1955). (27F;) Granstrom, M. L., Kahn, B., Ibid., 59, 408-10 (1955). (28E) Grinbere. A. D.. Straahesko. D. N.. Tovbin, M. V., Zhur. Fiz. Khins-28, 81-6 (1954). (29E) Guastalla, I,., Guastalla, J., Compt. rend. 240, 425-7 (1955). (30E) Guastnlla, I,. P.,and Guastrtlla, J., MBm. services chim. &at (Paris) 38 (No. 2), 99---107,(1953). (31E) Hackerman, N., Roebuck. A. H., IXD. ENQ.CHPX46, 1481-5 (1954). (32E) Ihckerman, N., Stephens, S. J., J . P h y s . C h e m 58, 904-8 (1954). (33E) Hrtldeman, R. G., Emmett, P. H., Ibid., 59, 1039-43 (1955). (34E) Hamaguchi, K., M e m . Inst. Sci. and Ind. Research, Osaka Univ. 11, 176-7 (1954). (35E) Hanaon, R. S.,Hansen, R. D., J. Phys. Chem. 59, 496-8 (1955). (36E) Rarrap, B. S., J . Colloid Sci. 9, 522--34 (1954). (37E) Healey, 1.’. H., Chessick, J., Zettlemoyer, A. C., Young, G. J., J . Phys. Chem. 58, 887-90 (1954). (381.:) Hotta, I€.,Bull. Chem. SOC.J a p a n 27, 80-4 (1954). (39E) Ibid., pp. 93-7. (40E) Ibid., pp. 412-16. (41E) Hotta, II., J. Colloid Sei. 9, 504-21 (1954). (42E) Hut,chinson, F;., PubE. Am. Assoc. Advunce. Sei., Monomol. Lauers 1951, 161-74 (Pub. 1954). (43E) Inokuchi, K., Bull. Chem. Soc. J a p a n 26,471--5 (1953). (44E) Iofa, Z. -4,, Roshdestvenskaya, G. B., Doklady A k a d . N a u k S.S.S.R. 91, 1159-62 (1953). (45E) Isemura, T., IIamaguchi, K., Bull. Chem. SOC.J a p a n 26, 425-9 (1953). (46E) Ibid., 27, 125-30 (1954). (47E) Ibid., pp. 339-45. (48E) Izmanov, 5 . A,, Shostcnko, Y. V., Mushifiskaya, S. I
