Showing papers in "Clays and Clay Minerals in 1954"

The Relation Between Composition and Swelling in Clays

Abstract: The phenomenon of swelling is associated with the hydration of clay; however, all clays do not swell when hydrated. Steps in the mechanism of hydration and swelling of different types of clays as observed and interpreted by several investigators and some theories proposed as to the cause of hydration and swelling are reviewed. The concept of clays as colloidal electrolytes that dissociate to a greater or less extent when dispersed in water seems to explain most satisfactorily the significant relation between the degree of swelling on hydration and the composition of the clay minerals. In the kaolinite group, in which there are generally no replacements, the small number of exchangeable cations associated with the clay structure are presumed to be held by broken bonds on the edges of the sheets. Even though kaolinite, as shown by Marshall, is more highly ionized than montmorillonite, this greater ionization, because of the small number of cations present and their location on the edges of the sheets, cannot pry the units apart or leave the sheets sufficiently charged to cause the mineral to exhibit the phenomenon of swelling. In the montmorillonite structure, on the other hand, isomorphous replacements, most commonly of magnesium and ferrous iron for aluminum in the octahedral layer, and, to a slight degree, replacement of aluminum for silicon in the tetrahedral layer, give the structure a net residual charge of 0.7 to 1.10 milliequivalents, which is neutralized by cations held electrostatically and located, for the most part, between the sheets. On hydration such a structure tends to ionize, the degree of ionization depending on (a) the nature of the exchangeable cation and (b) the kind and extent of isomorphous replacements. The characteristically great swelling of sodium montmorillonite as compared with calcium montmorillonite can be correlated with its much greater ionization. The differences in swelling of different montmorillonites have been correlated with the nature and extent of octahedral substitution and are attributed to the effect of these replacements on the anionic strength of the structural unit and its consequent degree of ionization as influenced by the changes in polarization throughout the structure caused by these replacements. Hydrous mica, with the same structure as montmorillonite, is characterized by even a greater degree of isomorphous replacements and, consequently, a greater charge. However, a large part of this charge is neutralized by fixed, nonexchangeable and nonionizable potassium, and ionization of the exchangeable cations is unable to overcome the effect of this fixed potassium. It is probable that the greater replacements in the hydrous mica structure, as in the montmorillonite structure, have a depressing effect on ionization. The result is that hydrous micas are characterized by a very low degree of swelling.

Lattice Expansion and Rheological Behavior Relationships in Water-Montmorillonite Systems

Abstract: Some divergent experimental data have been reported on the swelling behavior of sodium montmorillonite. At water contents above 50 percent (based on the weight of dry clay) the basal reflection of sodium montmorillonite at 19.2 A becomes weak and very diffuse; some workers have stated that it disappears altogether while others report a persistent weak line even at very high water content. The pronounced differences in physical properties of sodium and calcium montmorillonite suggest that their lattice expansions should also be dissimilar. This paper describes some X-ray diffraction experiments using purified lithium, sodium, and potassium montmorillonites dispersed in water and in salt solutions which were conducted for the purpose of resolving some of these disputed points. The X-ray diffraction instrument employed was a General Electric geiger counter spectrometer unit with a copper tube and nickel filters. The knowledge thus gained has provided some insight into other properties of these clays, such as their rheological behavior. A recording Couette-type viscometer designed to provide a wide spectrum of shear rates and shearing stresses has been used to examine the rheological transformations which occur in passing from states of maximum dispersion to states of varying degrees of agglomeration as a result of interactions between LiCl, NaCl, KCl, and CaCl2, and the Li, Na, K, and Ca salts of montmorillonite in terms of certain ideal rheological models. Filtration characteristics of these systems have also been explored using a standard technique.

The Effect of Clays on the Permeability of Reservoir Sands to Waters of Different Saline Contents

Abstract: The average results of air- and water-permeability determinations are given for petroleum-reservoir sands in three Wyoming fields. The average amounts of materials of clay size in the sands and the types of clays present, as identified by X-ray diffraction methods, are also presented and discussed. The sands are shown to be more permeable to air than to brines and more permeable to brines than to fresh water. Each of the sands exhibited different behavior when wetted by waters, and the percentage loss of permeability to waters, as compared to air, varied from sand to sand. The sand containing kaolins, illites, and mixed-layer clay (illite-montmorillonite) was found to be the most sensitive to water, and the sand containing only small amounts of kaolins and illites was the least sensitive. The sand that contained the most kaolins and illites was intermediate in water sensitivity. The water-permeability behavior of the sands and the dependence of this behavior on the clays present and the salinity of the water are discussed.

Anomalies in the Ethylene Glycol Solvation Technique used in X-ray Diffraction*

Abstract: X-ray diffraction results are presented to show that some montmorillonites will not retain two layers of ethylene glycol in the interiayer space when dried under atmospheric conditions. Diffraction data obtained from such samples of montmorillonite may erroneously be attributed to mixed layer minerals. Studies have shown however that this difficulty may largely be overcome by initially saturating the sample with ethylene glycol by the vaporization technique described, after which the sample is placed in a saturated atmosphere of ethylene glycol for a period of 12–24 hours to come to equilibrium and then irradiated.

Method of Screening Chemical Bonding Agents for Clay Soils

Abstract: The constant consideration, punctuated by periods of almost frantic concentration of effort and by periods of dull lassitude, given to chemically bonding soil particles into structural materials has yielded some useful products, some laboratory curiosities, and some ideas as to how current and future efforts may be more meaningfully evaluated Current work indicates that attempts to evaluate chemicals for bonding clay soils are significantly clouded by: (1) lack of knowledge of the soil-chemical bond; (2) lack of knowledge of the type of soil surface susceptible to bonding; (3) lack of knowledge of the inhibitors to chemical reactions present in soil systems; (4) lack of a correlation of the differences in response to treatment between readily indentifiable clays and soil fractions apparently composed of these clays; and (5) lack of satisfactory laboratory techniques by which rapidly reacting chemicals can be properly incorporated with soils A program is proposed whereby standards of response to treatment are established for different categories of known bonding agents when used with fractionated silica, kaolin and kaolinitic soils, montmorillonite and montmorillonitic soils A device suitable for laboratory use in this program is suggested

Clay Minerals in Petroleum Reservoir Sands and Water Sensitivity Effects

Abstract: The ability of some petroleum reservoir sands to conduct oil is decreased by interaction of the porous rock with water, usually water fresher than that coexisting with oil in rock interstices. Shales penetrated by drilling operations may swell upon interaction with relatively fresh water drilling liquids. The question of the relation of specific clay mineral content to reservoir sand water sensitivity has not been investigated in detail by other workers, although bentonitic clays often have been considered responsible.

Electron Microscopy of Clay Surfaces

Abstract: Improvements in replica techniques have made possible the high magnification study of textural characteristics and surface features of clay aggregrates found either in nature or in the laboratory. The most successful method of sample preparation involves pre-shadowing the specimen with platinum and backing this with a layer of carbon prior to removal of the clay with a suitable solvent.

The Effect of Acid and Heat Treatment on Montmorillonoids

Abstract: H-montmorillonite, -beidellite, and -nontronite were found to change spontaneously into Al-clays. Rates of conversion of H- to Al-clay were slow at 0°C, but at temperatures of around 100°C, moist H-montmorillonite changed to Al-saturated montmorillonite within 24 hours. It appeared that Al-ions moved from lattice positions to exchange positions, with octahedral Al moving more rapidly than tetrahedral Al.

Reference Chlorite Characterization for Chlorite Identification in Soil Clays

Abstract: Literature pertaining to differential thermal and X-ray diffraction of chlorite minerals is reviewed. Optical, DTA, and X-ray data for eleven chlorite samples of clinochlore, prochlorite, thuringite, corundophilite, and leuchtenbergite are given. The effect of particle size (105 to −1 μ) on DTA, X-ray diffraction, glycol retention, and cation exchange capacity are given for two thuringites, one clinochlore, and one prochlorite. Identification of chlorite by DTA in a soil clay containing a mixture of minerals is improbable at the present time except under very favorable circumstances. However, for relatively pure chlorite samples, variations in chemical composition are reflected in the differential thermal curves. The largest change in the thermogram is produced by ferric iron which lowers the peak temperature from 720° C to 610° C. Differences in thermal behavior between low and high ferric iron chlorite species are maintained for any given particle size. Chlorite thermograms obtained by different investigators show much greater variation than the differences in thermograms for other clay minerals determined on different equipment. X-ray diffraction can be used to positively identify chlorite in a soil clay, (a) by careful analysis of reflections at least as great as 14 A, and (b) by the influence heat treatment (550° C for 30 minutes) has on the X-ray pattern. Heat treatment produces marked changes in the X-ray pattern of the finer particle size samples and the magnitude of the change effected is greater for high iron chlorites (thuringite) than for low iron chlorites (clinochlore and prochlorite). Olivine is not the recrystallization product for thuringite. The smallest size fractions show no tendency toward vermiculite or montmorillonoid. Cation exchange capacity for silt size chlorites varies from 4 to 32 m.e./100gm., and for −2 μ chlorite particles from 30 to 47 m.e./100gm. Cation exchange capacities for −2 μ and −1 μ chlorites are essentially the same. Ethylene glycol retention increases with decreasing particle size. Glycol retention for −2 μ chlorite samples varies from 25 to 40 mg, glycol/gm, clay. For −1 μ chlorite material, glycol retention is 2 to 4 times greater than for −2 μ material.

Effect of Exchangeable Cation on X-ray Diffraction Patterns and Thermal Behavior of a Montmorillonite Clay

Abstract: A stratum of bentonite in the North Park (?) formation near Granby, Colorado, is composed largely of a dioctahedral Ca-rnontmorillonite whose formula is calculated to be $$\left( {A{l_{2.84}}F{e_{0.50}}M{g_{0.72}}M{n_{0.04}}} \right)\left( {\mathop {A{l_{0.40}}S{i_{7.60}}}\limits^{\mathop \uparrow \limits^{{X_{0.86}}} } } \right){O_{20}}{\left( {OH} \right)_4}.$$ Na+, K+, Li+, H+, NH4+, Ca++, and Mg++ modifications were stored at 52 percent relative humidity and at 105° C-110° C. Results of X-ray diffraction, differential thermal, and thermal balance analysis depend upon the exchangeable cation and prior treatment. As with many montmorillonoids, d(001) = 22.7−30.1 A under room conditions; ao = 5.20 A and b0= 9.00 A. The (001 ) interference indicates that the unit cell typically includes two packets, or possibly more, which may be derived geometrically from each other by a glide of 1.73 A along (110) and 180° rotation. Weight loss above 190° C-3670 C exceeds that indicated by the Hofmann structure but conforms reasonably with loss indicated by a structure after that proposed by Edelman. Inverted Si-O tetrahedra are presumed to equal the number of univalent cations It is suggested that the exchangeable cations form hydroxides during thermal analysis by reaction with (OH)− at the apex of inverted Si-0 tetrahedra. The resulting H2O and NH4OH are lost during thermal analysis, thus explaining excessive weight loss. Ca (OH)2 and Mg(OH)2 so produced release one mole of H2O during thermal analysis. KOH, NaOH, and LiOH are not decomposed below 1,000° C. Thermal products vary with exchangeable cation and crystallinity increases with prior drying. The Li+ and Ca++ modifications produce beta-quartz and alpha-cristobalite with spinel and glass, whereas the other modifications produce only spinel and glass.

Clay Minerals in Some Illinois Soils Developed from Loess and Till Under Grass Vegetation

Abstract: Clay mineral analyses were made of three groups of soil profiles — one developed from Peorian loess overlying Illinoian till — one associated with glacial till of Wisconsin age — one developed on deep to thin loess overlying Wisconsin till. These groups were investigated to determine the influence of parent material and intensity of weathering upon the soil profile development and clay mineral composition. Montmorillonite, illite, and chlorite are the dominant clay minerals in all the samples studied. In known loess samples, montmorillonite is invariably the most abundant clay mineral component. In the samples of unweathered till of Wisconsin age, illite and chlorite are the abundant clay minerals.

Clay Mineral Studies of Some Recent Marine Sediments Off the North Carolina Coast

Abstract: Studies of Recent marine sediments from the North Atlantic Ocean were made in order to understand better the effects of diagenesis on the clay minerals. Samples from the continental shelf, the continental slope and the floor of the northwestern basin, north of Bermuda, were made available through the courtesy of the Lamont Geological Observatory of Columbia University. Most of the argillaceous material in these sediments is a poorly crystalline, complex mixture of chlorite and illite. The samples contain a small amount of kaolinite and montmorillonite. Some of the problems involved in the identification of these complex mixtures are discussed. Studies of the clay minerals reveal that a slight diagenetic change takes place, as indicated by the increasing crystallinity of chlorite and illite, with increasing depth below the clay-water interface and with increasing water depth. Some of the cores contain zones of red clay and the clay minerals contained therein are relatively well crystallized materials in contrast to the clay minerals in the greenish-gray clays. An hypothesis based on the oxidation state of the iron is advanced to explain the differences between the crystallinity of the three layer clay minerals in the red and greenish-gray clays.

DTA of Kaolinite and Montmorillonite Under Water Vapor Pressures up to Six Atmospheres

Abstract: Thermograms of kaolinite and montmorillonite were obtained at water-vapor pressures varying from approximately 0.0001 to 4,500 mm. of Hg with a variable pressure, dynamic gas, differential thermal analysis apparatus. The beginning of the kaolinite endotherm is shifted to a higher temperature with increasing water-vapor pressure. The sharp kaolinite exotherm is shifted to a lower temperature until at six atmospheres water-vapor pressure it makes a small broad peak at approximately 900° C. The dehydroxylation endotherm of montmorillonite is almost unaffected. The 900° C endotherm and the recrystallization exotherm are shifted to a lower temperature with increasing water-vapor pressure. The temperatures of the start of the endothermic peaks associated with exchange cations are shifted upward by increased gas (N2) pressure.

Interstratified Layer Silicates in Some Soils of Northern Wisconsin

Abstract: Examination of the silt and clay fractions of two northern Wisconsin soils, Omega loamy sand of the Brown Podzolic group and Ahmeek loam of the Brown Forest group, revealed considerable quantities of interstratified layer silicates. The two soils contained montmorin, vermiculite, chlorite, and illite both as discrete and interstratified components. Regularly alternating montmorin-illite structures, which registered a 28 A first order diffraction peak, and vermiculite-illite structures, which yielded a 24 A first order peak, were observed in the fine silt fractions of the Ahmeek loam A3 and B22 horizons, respectively. Weak diffraction peaks in general and lack of binary mixture average spacings was suggestive of ternary or quarternary interstratification of illite, chlorite, vermiculite, and montmorin in the medium and fine clay fractions of the Ahmeek loam horizons. Randomly interstratified vermiculite-chlorite and vermiculite-montmorin, as revealed by comparative basal diffraction peaks before and after heating potassium saturated samples, were evidenced in the fine silt and clay fractions of the Omega profile. Mixed layer components in the Omega and Ahmeek soils originated from illite and chlorite in the? horizons with a progressive increase in proportions of first vermiculite and finally montmorin with proximity to the soil surface. The observed weathering transitions within the mixed layer structures illustrates the effects of accelerated leaching which has taken place in these coarse textured soil profiles, even though these soils are relatively young (late Pleistocene).

Studies of Some Vermiculite-Type Clay Minerals*

Abstract: X-ray and electron-diffraction studies, and differential thermal analyses of the clay fraction of some soils from Virginia, New Jersey, and Wisconsin indicate an abundance of minerals resembling vermiculite. Measurements of the 060 spacing for these minerals give values lower than those obtained for trioctahedral vermiculites. It is suggested that the minerals studied are dioctahedral forms, which have resulted from the weathering of muscovite-type micas.

The Clay Mineral Composition of Representative Soils from Five Geological Regions of Texas

Abstract: Mineralogical studies for the <2 μ fractions are presented for seventeen soil profiles and two surface horizon samples, which represent eight soil types and five geological regions in the state. There was no evidence of clay mineral formation in the upper 6 feet or more of soil. X-ray diffraction data from the Lufkin, Ruston and Katy soils suggested some decomposition of montmorillonite and kaolinite in the upper horizon. However, the overall picture is one of little change in clay mineral composition between the soils and parent sediments.

Electron Micrographic Studies of Clays

Abstract: In order to provide a set of reference photographs to be used in identification studies, electron micrographs at relatively high magnification (40,000 to 132,000 diameters), together with some electron diffraction patterns, have been obtained of a group of (a) kaolinites, (b) halloysites, and (c) South Texas outcrop soil samples. Some of the kaolinites consist of well-formed hexagonal crystal plates with edges still sharp at a magnification of 132,000 diameters. Other kaolinites consist of irregular, relatively thin crystal sheets, which may be bent or folded. In one instance it has been possible to demonstrate that the average thickness of the sheets is only 10 A. At high magnification the halloysite clay minerals exhibit a structure consisting of rolled sheets, rather than hollow rods. In some cases, it is evident that several separate crystal sheets are coaxially rolled to form multiple concentric hollow tubes. In the South Texas outcrop samples, the morphology is very complex, as the samples do not consist of one uniform type of particle. Matted sheets composed of interlaced bundles of lath-like particles have been observed. These oriented particles exhibit typical “fiber” type electron diffraction patterns. Kikuchi lines were observed in a thin quartz crystal plate, examined for comparative purposes.

Measurement of Moisture Content and Density of Soil Masses Using Radioactivity Methods

Abstract: This paper deals with the application of methods involving the scattering of neutrons and gamma rays to the measurement of moisture content and density of granular materials. The measurement of moisture content is based on the principle that when fast neutrons emitted from a radioactive source collide with hydrogen atoms they are slowed down to a much greater extent than by collisions with other atoms. The number of slow neutrons thus produced is a measure of the number of hydrogen atoms present in the vicinity of the source. Water is the principal contributor of hydrogen atoms in a soil medium. A probe, containing a source of fast neutrons and a slow neutron detector, is inserted into the soil. The probe is connected by a cable to a suitably calibrated scaling instrument, and the moisture content determined from the count rate. The density of a soil is measured with a probe that is similar but provided with a source and a detector of gamma radiation. The gamma rays emitted from this source are scattered by collisions with electrons of atoms in their path. The higher the density of the surrounding medium, the greater the scattering. In the range of densities normally occurring in soils, greater scattering results in fewer gamma rays returning to the detector. Thus, the density of the medium can also be related to the count rate obtained with the scaling instrument. The advantages of the radioactivity methods are that continuous or repeated measurements of moisture content and density at any desired depth can be made, and that measurements are integrated over a large volume of soil, so that representative values are obtained. In addition, water may be detected in the solid or vapor states as well as in the liquid state. The soil undergoes a minimum of disturbance because the probe is lowered into an access tube slightly greater than 1 inch in diameter. Measurements can be made in a short time; once the access tube has been placed, it takes an average of about six minutes to determine both moisture content and density at a given depth. The instruments are not influenced by ordinary temperature changes. The method appears to be relatively independent of soil type, so that a single calibration curve for moisture content, and one for density, may be applicable to a wide range of materials. A description of the theory of scattering of neutrons and gamma rays is included in this report as well as a discussion of the various types of sources and detectors which can be employed in the procedure. Field and laboratory tests utilizing these instruments are described, and the accuracy of test results discussed. It is concluded that application of this method will provide a rapid, simple and accurate means for measuring moisture content and density of soils or similar granular materials. On this basis, recommendations for future research and more extensive applications of the method are reviewed.

Water Sorption Properties of Homoionic Montmorillonite

Abstract: Homoionic samples of four montmorillonite clays, selected on the basis of the properties which control their economic uses, were prepared by treating with two normal neutral solutions of ammonium acetate, lithium, sodium, potassium, calcium, and magnesium chloride. Atterberg plastic and liquid limits, slopes of the liquid limit curves, and water sorption curves were determined. Among the results suggested, the following are particularly considered:

Stability and Swell Pressure Characteristics of Compacted Clays

Abstract: This paper discusses some of the factors affecting the density vs. stability relationships of compacted clays and some of the limitations of the concept that the stability of a compacted soil increases with an increase in density. A series of tests performed on silty clay, in which stability was measured by triaxial compression tests, are described. It is shown that the relationship between density and stability of a soil depends on the criterion used to define stability; the greater the permissible strain before a sample is considered unstable, the greater is the possibility that an increase in density will cause an increase in stability. For the silty clay, when the stability is defined as the load required to cause 10 percent strain or less, an increase in density at a given water content caused an increase or decrease in stability depending upon the water content and the range of densities involved; at constant degrees of saturation, however, an increase in density always caused an increase in stability. The effect of compaction method on the density vs. stability relationship is illustrated. Test data are presented for two soils, a silty clay and a sandy clay, comparing the stabilities, at various water contents and densities, of partially saturated samples compacted by impact methods, static pressure and kneading action. It is shown that, at equal water contents and densities, samples compacted by static pressures exhibit higher stabilities than samples compacted by impact or kneading methods; also, that the stabilities of samples at equal densities and water contents, compacted by impact and kneading methods, are very similar, with kneading compaction producing somewhat higher stabilities at lower degrees of saturation, and impact compaction producing slightly higher stabilities at higher degrees of saturation. For static compaction, both soils showed an increase of stability with increase in density at all water contents, while for samples compacted by impact and kneading methods, an increase in density at a given water content did not necessarily lead to an increase in stability. The effect of saturation on the stability of compacted clays is shown and the influence of water content at compaction on the stability of saturated samples having the same density and water content is illustrated. Finally, a comparison is made of the stability and swell pressures developed at various densities of samples of the sandy clay compacted by kneading action and static pressure and subsequently saturated by exudation of moisture from the samples under static loads. It is shown that very much higher swell pressures and stabilities are exhibited by the statically compacted samples than by the samples prepared by kneading action.

Structural Irregularities in Hydrous Magnesium Silicates

Abstract: The crystal structures of chrysotile, antigorite, attapulgite, sepiolite, vermiculite, and montmorillonite are discussed in the light of the degree to which they resemble chlorite. The proposal is advanced that the perfection of articulation between tetrahedrally and octahedrally coordinated layers is temperature-sensitive, and that the several crystallizations reflect the degree to which difficulty of articulation limits the growth of particular compositions.

A Study in Morphology by Electron Diffraction

Abstract: A stabilized halloysite-glycerol complex was studied by electron microscope and electron diffraction techniques. The basal reflection was found to be 10.7 A by both electron diffraction and X-ray diffraction analyses. Electron micrographs of the expanded lattice (halloysite-glycerol complex) were not different from those of the collapsed lattice (halloysite). On the basis of the tubes evident in the micrographs and the fact that the basal reflection was present in the transmission electron diffraction pattern, it was established that the halloysite-glycerol complex is tubular. Since this complex has an expanded lattice 0.6 A greater than hydrated halloysite, it is believed that hydrated halloysite (endellite) is tubular as postulated by Bates, Hildebrand and Swineford.

The Reversible Dehydroxylization of Clay Minerals

Abstract: Rehydroxylization of the anhydrous modification of dioctahedral montmorillonites can be carried out under DTA conditions with controlled atmosphere techniques. The structural character of the rehydrate prepared in this way is determined from X-ray and DTA data. The mechanism of the reactions by which the rehydrate can be formed is also considered. Thermal analysis curves of the rehydrate form of several pure mont-morillonite samples failed to show any large variation such as is shown by the curves of the original clays themselves. The possibility is considered that such large variations in the dehydroxylization curves of montmorillonites are related to structural instead of compositional variations within the sample. It is suggested that montmorillonites showing two reactions attributable to dehydroxylization may be mixtures of the rehydrate form and montmorillonite.

Variations in Viscosity of Clay-Water Suspensions of Georgia Kaolins

Abstract: The viscosity of clay-water suspensions is an important factor in determining commercial uses of Georgia Kaolins. Impurities, such as montmorillonite type minerals, in these basically kaolinite clays play a part in causing variations in viscosity. However, seemingly pure kaolinite clays also show variations which seem to be related to morphology and degree of crystallinity. Studies are underway to determine the various factors involved.

Quantitative Evaluation of the Kaolinite and Illite in Underclays

Abstract: Oriented slides of twelve different mixtures of kaolinitic and illitic underclays were studied with the X-ray spectrometer and the resulting curves were evaluated on the basis of the area of the 001 peaks. Although the areas from the unmixed components varied greatly, within any given mixture the two clays were quantitatively comparable on the basis of a 1/1 001 peak area ratio. The considerable peak area variations from slide to slide are the result of different degrees of preferred orientation and are not due to any appreciable differences in crystallinity. Mixed-layering of expandable material with the illitic component does not affect the quantitative comparisons significantly.

A Method for the Determination of the Cation Exchange Capacity of Clay Minerals and Soils

Abstract: For many purposes it is desirable to have a method for the determination of the cation exchange capacity of clay minerals based on principles as free from ambiguity as possible. Most of the many methods previously proposed have the drawback of entailing a great deal of work if one is to make sure that the mineral is completely saturated with the reagent in use, or that an excess of the reagent is absent. What might be called the complete chromatographic method by its very nature does not suffer from this difficulty. A known weight of clay is suspended on an appropriate inert filter aid (such as Gooch asbestos), packed into a glass tube, and the exchangeable ions eluted with a solution of cesium chloride traced with radioactive Cs 137. The effluent is collected in a series of appropriately sized samples, and the specific radioactivity of each of these determined. When the activity of the effluent has risen to that of the influent solution, one is certain that complete exchange has taken place. A simple computation gives the total cesium holdup of the column, and if the column was initially dry, the exchange capacity of the clay sample. As a routine method, particularly when results of the highest precision are not needed, the effluent may be collected in only two samples, one large sample and finally one small sample to check for complete exchange. This procedure requires a minimum of work and attention but suffers from the disadvantage that the result depends upon the difference of the two counting rates measured and is thus subject to greater uncertainty. These methods have been compared with the Bower-Truog method (Ind. and Eng. Chem., Anal. Ed., 12, 411 (1940)) on Chambers, Arizona, montmorillonite, a nontronite, and an attapulgite. Generally the Bower-Truog method gave more variable and somewhat lower results. Thus for the Chambers montmorillonite the Bower-Truog method gave 0.97 meq./gm.; the chromatographic method, 1.054 meq./gm. The method has been further tested by initially saturating columns with manganous ion, determining the weight of solution held up in the column, and then eluting with traced CsCl. Effluent Mn was determined colorimetrically and the Cs in the Geiger counter. The results agreed within experimental error for the following clays of the API series: montmorillonites H19, H23, H24; illite H36; and nontronite H33b.

Swelling of Clay under Pressure

Abstract: An experimental technique for studying the swelling of clay under constraint and some preliminary results for the swelling of Wyoming bentonite in several media are presented and discussed. Fractionated, powdered clay is mixed with an equal weight of non-swelling microporous porcelain, which serves to distribute the swelling agent rapidly and uniformly. The mix is compacted in a cell at high pressure and permitted to imbibe fluid through a porous porcelain plate under simultaneously applied almost equal pressures from 0 to 10,000 psig on both sides of the fluid-gel interface. The unidirectionally constrained volume change of the sample is measured by displacement of mercury in a steel buret. Degree of swelling is taken as the volume ratio of gel to 105° C dry clay. In the range of pressure from 0 to 10,000 psig, the colloidal magnesium sodium montmorillonite swells from about 93 to 231 percent (volume ratio 1.93 to 3.31) depending on the composition of imbibed fluid. Aqueous 0.171N sodium chloride and magnesium chloride solutions produce 14 and 11 percent, respectively, more swelling at 1,500 than at 0 psig. Swelling in calcium chloride solution is insensitive to this pressure change. At 10,000 psig these solutions, and hydrochloric acid, produce less swelling than at 1,500 psig and, in fact, produce almost equal swellings of 130± 4 percent. It is inferred that swelling in chloride solutions at this pressure may be essentially cation-independent. Within the concentration range of 0 to 171N there appears to be little practical difference in the degree of swelling of the clay by sodium chloride and calcium chloride solutions; the swelling is a linear function of the logarithm of the salt concentration. Comparison of d(001) spacings calculated from swelling ratios with those obtained by X-ray diffraction lead to the conclusion that the method measures crystalline swelling in contradistinction to osmotic swelling.

Peptization Resistance of Selected Samples of Kaolinitic, Montmorillonitic, and Illitic Clay Materials

Abstract: Variations in the peptization resistance of selected samples of clay mineralogical materials toward alkaline dispersing agents are discussed from a quantitative point of view. Clay samples, collected from South Carolina, Wyoming, Illinois, New Mexico, South Wales, Great Britain and Cornwall, England were subjected to the action of solutions of Calgon (“sodium hexametaphosphate”), ammonia, sodium hydroxide, sodium carbonate, sodium pyrophosphate, and “sodium lignosulfonate.” The resulting apparent dispersion, in each case, was expressed as a function of the employed concentration and chemical nature of the dispersing agent. Pipette analysis and Oden balance techniques at constant temperature were used to measure the degree of dispersion. All clay samples employed were identified as to type by X-ray diffraction, chemical analysis, thermal analysis, and electron microscopy. All samples examined exhibited a maximum in apparent dispersion (suspension stability) at a specific concentration of dispersing agent. Such maximum was followed by a sudden decrease in apparent dispersion, i.e., flocculation, at higher concentrations of dispersing agent. Concentrations of dispersing agent were varied in steps of one part per thousand. One hundred and twenty experimental runs were made on each type of material examined. Differences in the degree of apparent dispersion attained by use of different dispersing agents were expressed in terms of a threshold concentration which altered “equivalent diameter” one tenth of a phi unit. Among dispersing agents employed, “sodium lignosulfonate” was found to be least selective of clay mineral type in its peptizing action. An equation for the calculation of a “peptization resistance factor” is presented. Results obtained by application of this equation indicate that differences in the response of the same clay material to different alkaline dispersing agents may be attributed, in part, to differences in degree of peptization achieved by “threshold mechanisms” of peptization and by “adjustment mechanisms” along the peptization path. Such equation may have future value in the differentiation of marine and terrestrial clay deposits.