Showing papers in "Clays and Clay Minerals in 1970"

Methylene blue absorption by clay minerals. determination of surface areas and cation exchange capacities (clay-organic studies xviii)

Abstract: Under appropriate conditions, both surface areas and cation exchange capacities of clay minerals can be measured by absorption of methylene blue from aqueous solutions. The method has been applied to two kaolinites, one illite, and one montmorillonite, all initially saturated with Na + ions. For Na-montmorillonite, the total area, internal plus external, is measured. For Ca-montmorillo- nite, entry of methylene blue molecules appears to be restricted by the much smaller expansion of the Ca- clay in water. X-ray diffraction data clarify the absorption behavior in Na- and Ca-montmor- illonite, and in particular it is shown that two orientations of the methylene blue molecules are in- volved.

Burial Diagenesis in Gulf Coast Pelitic Sediments

Abstract: Subsurface samples of shales ranging in age from Pleistocene to Eocene obtained from five Gulf Coast oil wells were examined mineralogically and chemically to determine the nature and extent of burial diagenesis in pelitic sediments. Illite/montmorillonite dominates the mineralogy and undergoes a monotonic decrease in expandability from about 80 to a limit of 20 per cent montmorillonite layers with increasing depth. The interstratification changes from random to ordered at about 35 per cent expanded layers. Discrete illite and kaolinite phases are ubiquitous and judged detrital. The discrete illite (mica) content of the whole rock decreases with depth, while the kaolinite shows no systematic variation. Chlorite occurs in appreciable amounts in only one well and there only in samples from the shallow water facies. This chlorite is also considered detrital.

The Nature of Interlayering in Mixed-Layer Illite-Montmorillonites

Abstract: The nature of interstratification in mixed-layer illite-montmorillonites has been investigated by comparison of diffraction patterns of ethylene glycol and ethylene glycol monoethyl ether treated samples with calculated one-dimensional diffraction profiles. The calculated profiles take into account the effects of particle size distribution, chemical composition, and convolution factors as well as proportions of layers and interstratification type. On the basis of detailed matching of diffraction patterns of monomineralic illite-montmorillonites of known chemical composition it is concluded that there are three types of interstratification: (1) random, (2) allevardite-like ordering, and (3) superlattice units consisting of three illite and one montmorillonite layers (IMII). By comparison of suites of calculated profiles with the diffraction patterns of many samples of illite-montmorillonites it is concluded that virtually all illite-montmorillonites with expandabilities from about 40 to 100 per cent are randomly interstratified (allevardite being exceptional); at >40 per cent montmorillonite layers they almost always have ordered interstratification. Allevardite-like ordering predominates in illitemontmorillonites which have ordered interstratification, with the IMII superlattice varieties confined to samples with about 10 per cent montmorillonite layers.

Pore Size Distributions in Clays

Abstract: Abstraet-A knowledge of the distribution of pore sizes in clay and soil bodies is a useful element in the microstructural characterization of such materials. Pore-size distributions and total porosity of a number of reference clays, naturally-occurring subsoils, and commercial clay samples prepared in various ways were determined by mercury porosimetry. The range of equivalent pore diameter explored covered almost five orders of magnitude, from several hundred microns down to approximately 150A. The method and its assumptions are critically evaluated, and measurements of the contact angle of mercury on clays yield values of 139 ~ for montmorillonite and 147 ~ for kaolinite and illite clays. The extent of shrinkage on oven-drying prior to mercury intrusion is assessed in each case and found to vary from insignificant to as much as 30 per cent of the pore space, depending on microstructural state and degree of initial saturation. The development of techniques for water removal which do not involve change in pore structure is explored. Some preliminary results for structurally weak saturated clays suggest that critical-region drying and perhaps freeze-drying procedures may be practical.

Potassium and cesium ion selectivity in relation to clay mineral structure

Abstract: Selectivity of a number of vermiculites, montmorillonites and micas for K and Cs ions was determined by sorption of these ions from equilibrium solutions of diverse concentrations. The selec- tivity coefficients were related to the layer charge density and the area of the frayed edges in layer silicates. Montmorillonites had the smallest selectivity for the two ions, while biotite and illite had the great- est selectivity. Selectivity of biotite and illite was limited to small concentrations of K, however. At greater concentrations the selectivity of vermiculite for K exceeded the selectivity of the micas. The greater selectivity of vermiculites than montmorillonites for K and Cs ions was attributed to the greater layer charge density in vermiculites. The greater selectivity of micas than montmorillonites and vermiculites was attributed to the frayed edges of micas in addition to their larger layer charge density. As the frayed edRes in illite were increased in area by removal of the interlayer K, the selec- tivity of illite for K also increased; thus confirming the selectivity of frayed edges for the K ions.

Polytypism of Chlorite in Sedimentary Rocks

Abstract: Four chlorite polytypes of Bailey and Brown (962) have been identified by X-ray diffraction in clay-size chlorites of soils, sediments, and sedimentary rocks: (1) IIb, the polytype of common metamorphic and igneous chlorites; (2) Ib(s = 90°); (3) Ib(s = 97°); (4) Ia. An additional stacking arrangement. Iba, is defined herein as disordered chlorite which lacks an h0l diffraction band in the 2.4–2.5 A region. Most type-I chlorites are authigenic, as demonstrated by thin-section petrography. Type-I chlorites form during diagenesis, or less commonly during halmyrolysis, at temperatures and pressures less than those of low-grade metamorphism. A type-1 crystallization sequence is proposed, from least to most stable: Iba → Ib(s = 97°) → Ib(s = 90°). Conditions of low-grade metamorphism usually are necessary to cause conversion of Iba(s = 90°) to IIb, the most stable and common polytype. Chemical composition has little or no influence upon polytype relative stabilities; temperature is much more important. Sediment source areas with high relief, abundant rainfall, cold climate, and which contain IIb-chlorite-bearing metamorphic rocks, may yield essentially unweathered IIb chlorite to sites of deposition. Thus, clay-size IIb chlorite in unmetamorphosed sedimentary rocks can be interpreted as detrital. Caution is required, however, because IIb may be able to form authigenically at submetamor-phic temperatures, because it is the most stable polytype. Petrographic evidence is useful in such cases. Chlorite polytypism as a geothermometer can be applied to several geologic problems: (1) the authigenic versus detrital origin of clay minerals in sedimentary rocks, particularly in graywacke matrix; (2) the recognition of diagenetic facies or gradients, areally and stratigraphically, within given geologic provinces; (3) the detection of hydrothermal and incipient metamorphic effects. Chlorite polytypism merits general application as an interpretive tool.

Prototropy in kaolinite during percussive grinding

Abstract: When kaolinite undergoes percussive grinding, pronounced changes take place in its i.r. absorption spectrum even in the earliest stages of the grinding when the lattice is not yet destroyed. In this report, attention is directed to the change in the stretching bands of the hydroxyl ions. A remarkably rapid effect on the band of the intralayer hydroxyl ions has been observed and is attributed to a permanent removal of the protons from these ions. Auxiliary measurements of X-ray diffraction, thermal water loss, and DTA were used to corroborate the spectroscopic evidence for this ready prototropy.

Surface Area of Homoionic Illite and Montmorillonite Clay Minerals as Measured by the Sorption of Nitrogen and Carbon Dioxide

Abstract: The surface areas obtained by application of the B.E.T. theory to adsorption isotherms of nitrogen and carbon dioxide gases at 77~ and 195~ respectively on homoionic samples of illite and montmorillonite clays have been examined. The isotherms were obtained using a standard volumetric adsorption system and the results are compared with those obtained by Thomas and Bohor (1968) using a dynamic sorption system. Small amounts of residual water have been shown to have a marked influence on the accessibility of the internal surfaces of the montmorillonite clays to nitrogen and carbon dioxide adsorption, in this respect the standard outgassing procedure under high vacuum seems more efficient than that used in dynamic systems. The present data indicate that provided the sample has been satisfactorily outgassed there is little penetration of nitrogen or carbon dioxide gases into the quasi-crystalline regions of montmorillonite clays. With the exception of the caesium saturated montmorillonites the surfaces of the clays are more accessible to the smaller nitrogen molecules than to carbon dioxide assuming the values used for molecular area are correct. IN A RECENT paper Thomas and Bohor (1968) have examined the accessibility of the surfaces of homoionic montmorillonite clays to nitrogen and carbon dioxide adsorbates at 77~ and 195~ respectively using a dynamic measuring system (Nelson and Eggertsen, 1958). From variations in the surface area obtained by application of the B.E.T. (1938) theory to these measurements these authors considered that there was a certain degree of penetration of both nitrogen and carbon dioxide between the unit platelets or lamellae forming the crystals of montmorillonite. Their experimental data indicated that the extent of penetration was time dependent and also a function of the interlayer forces as governed by the size and charge of the replaceable cations. Aylmore and Quirk (1967) have recently pointed out that in the dry state montmorillonite clay forms a complexly interwoven matrix in which one lamella may conceivably pass through several apparently crystalline regions. It is considered that the term "quasi-crystalline" (Aylmore and Quirk, 1969) may be the most appropriate descrip- tion here since in these regions the lamellae are stacked in parallel array but not necessarily in perfect crystalline order. In these circumstances 91 the definition of apparent crystal size must be somewhat arbitrary. It was considered that the area determined by nitrogen adsorption at low temperatures was essentially a measure of the surface area external to these quasi-crystalline regions. The differences in specific surface area observed between montmorillonite saturated with different exchangeable cations was attributed partly to differences in the degree of association of the lamellae in aqueous suspensions (Edwards, Posner and Quirk, 1965) and the subsequent statis- tical arrangement of the units on drying, and partly to variations in accessibility of areas of overlap of quasi-crystalline regions with size of the exchangeable cations. Since the data reported by Thomas and Bohor (1968) was obtained using a dynamic sorption system (Nelson and Eggertsen, 1958) the results of similar sorption measurements obtained using a standard volumetric adsorption system are reported here.

Interactions of Clay Minerals with Organic Polymers. Some Practical Applications

Abstract: An account is given of the interactions between clay minerals and organic polymers with particular reference to their applications in agriculture, foundation engineering and industry.

Titanium as Free Oxide and Substituted Forms in Kaolinites and Other Soil Minerals

Abstract: Titanium in TiO2 minerals was differentiated from that isomorphously substituted into minerals by the use of dihydrogen hexafluorotitanate (hydrofluotitanic acid, H2TiF6), which selectively dissolved minerals containing substituted Ti4+, leaving free crystalline TiO2 minerals in the residue. Titanium analyses on the original samples and the residues remaining after H2TiF6 treatment, by both wet chemical (Tiron) and neutron activation methods, indicated that an average of 86 per cent of the titanium in seven kaolinite samples was present in the residual TiO2 form (largely anatase), whereas only 28 per cent in two bentonites was present in the TiO2 form. Residual Ti accounted for 100 per cent of the Ti in synthetic anatase and for 92 per cent of the Ti in coarse clay sized rutile, the latter value suggesting that about 8 per cent amorphous TiO2 was removed from the mechanically dry ground rutile by the H2TiF6 reagent. The Ti present as residual TiO2 in a variety of other samples ranged from 0 to 100 per cent.

Precipitation of Kaolinite at 25°C and 1 ATM

Abstract: The 0.2–5μ particle size fraction of montmorillonite from three sources was equilibrated with various solutions at room temperature. After 3–4 yr, kaolinite was found in some of the samples that were supersaturated with respect to kaolinite, but not in any of the undersaturated samples or in the original montmorillonite. X-ray diffraction analysis of the precipitated kaolinite showed no inter-layer expansion of glycerated, oriented samples. Random powder samples indicated a poor crystal-Unity. The thermal stability of the precipitated material was indistinguishable from that of crystalline kaolinite. The electron microscope did not reveal any distinctive sizes or shapes. Equilibration behavior of several samples defined a single kaolinite solubility line at or above which kaolinite apparently begins to precipitate. The solubility line is equivalent to a standard free energy of formation (AG) of -904.2 kcal per mole of kaolinite. This represents highly crystalline kaolinite. The stability of kaolinite actually precipitated at room temperature probably depends upon precipitation conditions. Thus kaolinite stability could range from poorly crystalline up to the equivalent of the kaolinite solubility line at which initial precipitation begins.

Adsorption of surfactants on montmorillonite.

Abstract: Some authors have stated that anionic surfactants are not adsorbed by montmorillonite while others indicate very minor adsorption. Attempts to quantitatively determine the degree of adsorption have shown that certain problems exist which, unless recognized, will completely mask results. Some of these difficulties have been overcome but exact data have not yet been obtained. However, enough information has been gathered to prove that adsorption of anionic surfactants on montmorillonite is real and substantial. Reliable adsorption data for cationic and nonionic surfactants and one having both nonionic and anionic character have been obtained. It is indicated that 550 mg of these surfactants are adsorbed by 1 g of montmorillonite. X-ray diffraction data for complexes of all surfactants investigated confirm positive adsorption. However, the thickness of the adsorbed surfactant layers cannot always be quantitatively related to the amount of adsorbed surfactant.

I.R. Study of Alkyl-Ammonium Vermiculite Complexes

Abstract: Two octyl-ammonium vermiculite complexes with different 001 periodicities have been studied by i.r. spectroscopy. In each case i.r. spectroscopy affords information on the orientation of the-NH3 + groups and the strength of the hydrogen bond between these groups and the silicate oxygen surfaces. Also a perturbation of the vibration of the OH groups of the silicate has been observed that seems to be related to the distance from the center of the layer at which the-NH3 + groups are situated. The i.r. results are discussed in relation to the structural models deduced from X-ray analysis.

Factors affecting potassium fixation and cation exchange capacities of soil vermiculite clays

Abstract: Soil vermiculite clays of varying tetrahedral and octahedral composition and cation exchange capacity (CEC) were examined for their ability to fix K § in both the wet and dry states. Fixation capacity, expressed as per cent of the CEC, in the wet state was fairly high for most samples but it was enhanced greatly upon drying the K saturated samples. This enhancement indicated that each sample contained a number of vermiculite species with different CECs. The vermiculite clays, as a group, exhibited a much higher fixation capacity at a much lower CEC than those of the coarse grained vermiculites. This enhanced fixation is believed due to the diocta- hedral nature of the coarse grained vermiculites. In samples of nearly equal CECs only those con- taining AP § in tetrahedral positions exhibited an enhanced fixation capacity in the dry state but not in the wet state. In was remarkable to find that the state of oxidation of crystal structure iron strongly affected the fixation and the CEC. Reduction of Fe z+ to Fe z+ caused a decrease infixation even though the CEC increased as a result of this change. Conversely these reactions and their effects were found to be reversible. The variation in the orientation of the dipole of the hydroxyl ion in the octahedral layer with respect to the cleavage plane of the crystal is believed to be responsible for some of the noted differences.

Mica weathering rates as related to mica type and composition

Abstract: Potassium release rates from micas varying widely in type and composition were measured. A sodium tetraphenylboron solution was used as the extracting agent. Muscovites were found to be two orders of magnitude more stable than a naturally occurring phlogopite and biotite. Synthetic fluorphlogopite was as stable as some muscovites. Lepidolite was the most stable mica. Primary factors affecting mica stability are thought to be: Hydroxyl bond orientation, isomorphous replacement of OH- by F-, the stronger Lewis base, and structural factors that lead to compression or stretching of the K---O bond.

Iron Alkoxide Obtained by Reacting Iron Oxides with Glycerol

Abstract: Goethite, lepidocrocite and hematite were reacted with glycerol and reaction products were studied at various steps of the reaction. After a treatment of 16 hr at 245°C the final form of the reaction product, a deep green soft solid, was obtained whatever the starting material. According to hydrolysis and chemical analysis, the reaction product can be identified as iron alkoxide. Hydrolysis of the solid by boiling water yielded glycerol and a strongly magnetic material characterized by a spinel structure like maghemite and magnetite.

Vermiculite as a Model System in the Testing of Double Layer Theory

Abstract: The microelectrophoretic and adsorption behaviour of lithium vermiculite has been studied as a function of lithium chloride concentration. This was done in an attempt to establish the applicability of such systems to the testing of theories of interaction of flat plates, and in so doing to throw further light on swelling measurements performed on such materials. The studied behaviour, while highly unusual, gave quite good agreement between adsorption and microelectrophoretic parameters and agreed, qualitalively, with some earlier measurements on similar materials. The observed properties appear to be due to some rather specific structuring effects, either of the oxide surface or of the electrolyte ions. If this is so, these systems are far from ideal models for the testing of the theory of interaclion of two uniform flat plates.

Relation Between Crystal-Lattice Configuration and Swelling of Montmorillonites

Abstract: Prompted by Foster’s observation that free swelling is related to octahedral substitution, the authors determined the free swelling of six Na-montmorillonites with different amounts of octahedral and tetrahedral substitution. They found that the montmorillonites exhibited marked differences in free swelling. These differences were not related to differences in cation exchange capacity. Nor were they related to differences in ζ potential, which is a criterion of cation dissociation. Further, calculations indicated that they could not be accounted for by differences in double-layer repulsion or van der Waals attraction. Therefore, to see if dimensional changes produced by isomorphous substitution were responsible, free swelling was plotted against the b-dimension of the clay structure, which was calculated from its mineralogical composition. The result was a straight line with a negative slope. A similar result was obtained with Foster’s data. In addition, free swelling was plotted against the degree of tetrahedral rotation in the clay structure, which was also calculated from its mineralogical composition. The result was a family of nearly parallel straight lines that were distinguished from each other by the amount of tetrahedral Al3+ in the clays identified with them. These results led to the proposal that the clay surface acts as a template for the structure of the adjacent water and that, as the configuration of the surface changes, the water structure changes accordingly. This causes a change in the free energy of the water and, hence, in the swelling of the clay.

Ion Selectivity by Weathered Micas as Determined by Electron Microprobe Analysis

Abstract: Electron probe micro-analysis studies on individual particles (40–60 mesh) of weathered micas treated with solutions containing equivalent amounts of Rb and Sr showed partial segregation of these elements. Rb was concentrated at particle and step edges, at cracks, and, in the case of partially K-depleted biotite, at boundaries of vermiculite and mica zones (“wedge zones”). The scarcity of wedge zones in mica from which nearly all of the K had been removed reduced the overall selectivity for Rb. The restricted exchange of interlayer Mg ions from vermiculite-like zones by a mixed Rb-Sr solution was observed in earlier studies with these micas. The proposed explanation for these results was a closing down of the interlayer space at the edge of the particle due to Rb concentration in these positions. This explanation is confirmed by the present study.

The Origin of Pyrophyllite Rectorite in Shales of North Central Utah

Abstract: Pyrophyllite is widespread in pelitic rocks of the Manning Canyon Shale in north central Utah, and the association of this mineral with other clay minerals, especially rectorite is related to the origin. The regular mixed-layer clay mineral rectorite seems to form as a result of the alteration of muscovite-paragonite during late stages of diagenesis and represents an intermediate metastable phase in the mineral paragenetic sequence. Pyrophyllite subsequently formed from the alteration of rectorite during advancing metamorphism and is the stable end member of the clay mineral assemblage. Structural interpretations of rectorite found in the Manning Canyon Shale shows a regular, alter- nating sequence which consists of a fixed layer of 9.6 ,~ and an expandable layer, varying from 10 A to 17 A. With ethylene glycol saturation in the natural state a basal reflection of 26-60 A is recorded.

A Hydromuscovite from the Shakanai Mine, Akita Prefecture, Japan

Abstract: A hydromuscovite in association with gypsum and anhydrite was collected from the Shakanai mine, Akita Prefecture, Japan. Chemical composition: SiO2 47·14%; TiO2 0·34%; A12O3 37·09%; Fe2O3 0·49%; MgO 0·83%; CaO 0·57%; Na2O 0·35%; K2O 7·10%; H2O+ 5.18%; H20–0·99%; P2O5 0·01%; total 100·09%. Differential thermal and i.r. absorption analyses were similar to those of hydromuscovite. The X-ray diffraction pattern differed clearly from those of the 1M and/or 2M1 polymorphs and it was similar to that of the 2M2 polymorph, which is known to occur in lepido-lites.

Thermal reactions of synthetic hectorite

Abstract: The thermal reaction sequence of a synthetic hectorite (Laponite CP) was studied by X-ray diffraction, i.r. spectroscopy and thermal analysis. Although most of the interlayer water is removed at 200°C, a smally steady weight loss occurs until dehydroxylation is complete at about 700°C, indicating that an anhydrous intermediate phase is not formed prior to dehydroxylation. Immediately after dehydroxylation, enstatite and cristobalite can be identified, but lithium silicates are formed only from lithium-saturated hectorite. Around 1200°C a glass is formed by reaction of the alkalis with cristobalite, and removal of silica from the enstatite produces some forsterite. An inhomogeneous mechanism of dehydroxylation is postulated by analogy with that proposed for talc.

Conditions of Kaolinite Formation During Alteration of Some Silicates by Water at 200°C

Abstract: When a mineral of the montmorillonite group, saturated with Na cations, is placed in a dilute solution of hydrochloric acid, and maintained at 200°C, it should alter and produce the corresponding mineral of the kaolinite group, according to the following reaction: triphormic clay + H+ ⇌ diphormic clay + SiO2 + Na+. The formation of the diphormic clay should depend only on the value of the [Na+]/[H+] ratio, for the various temperatures used in the process. In a number of experiments, a few minerals of various types were subjected to this alteration process, carried out under a wide variety of conditions; namely, duration of the alteration treatment, clay and acid concentrations and value of the [Na+]/[H+] ratio. Formation of kaolinite, was not found but instead either an amorphous gel, or a well-crystallized boehmite, or else no dissolution at all of the initial mineral. We have already shown that a feldspar, when subjected to an alteration under similar conditions, never produces kaolinite, but forms a poorly crystallized boehmite instead. This intermediate product is the only one able to fix silica in its numerous active sites, and thus produce kaolinite. In this investigation we sought to induce a formation of poorly crystallized boehmite, from montmorillonites, with a view to a subsequent growth of kaolinite. This was achieved by inserting layers of aluminum hydroxy-polymer between the layers of a montmorillonite, followed by an alteration conducted under the same conditions as previously. At the end of a 17 hr treatment, a number of fibers of poorly crystallized boehmite (pseudo-boehmite b) appeared. At the end of a 15 days period, large amounts of kaolinite were formed, and kaolinite alone remained at the end of one month. These experiments substantiate the need of some ‘storage’ of the aluminum in an intermediate poorly crystallized mineral. This is an essential preliminary condition to any formation of clay. This clay can be formed only when the silica-monomer can be fixed on active sites of the intermediate product.

Stretching Frequencies of Structural Hydroxyls of Hectorite and K-Depleted Phlogopite as Influenced by Interlayer Cation and Hydration

Abstract: The frequencies of structural OH stretching vibrations in swelling trioctahedral minerals such as hectorite or K-depleted phlogopite depend on the ionic form and hydration of the sample. The trioctahedral structure is evidently a suitable case for the observation of spectral changes, since hydroxyl groups are in conditions of high reactivity with the surrounding medium. These changes are attributed to the field which originates either from the cations or the residual water molecules, and the joint analysis of spectroscopic and X-ray diffraction data permits an interpretation that frequencies quoted for unaltered mica are only perturbed frequencies.

Formation and Stability of Hydroxy-Mg Interlayers in Phyllosilicates

Abstract: A study was conducted to (1) determine the conditions of hydroxy-Mg interlayer formation with respect to type of clay mineral, acidity, and time; (2) evaluate the stability of this interlayer to dissolution treatments; and (3) ascertain the effects of such treatments upon the determination of clay minerals in soils and sediments. Hydroxy-Mg interlayers were formed in montmorillonite and vermicu- lite by adding MgCI~ and NaOH in amounts to give a wide range of pH. The resulting chloritic intergrades were examined after 10 days, 6 months, and 1 yr. Alkaline conditions favored the formation of hydroxy magnesium interlayers in phyllosilicates. Hydroxy-Mg interlayered montmoriUonite which resulted from 10 days equilibration at pH 10.4 did not expand upon solvation with ethylene glycol and exhibited practically no collapse after K-saturation and heating at 550~ A small amount of interlayer was formed between pH 6.8 and 9.8 (10 days). In contrast, vermiculite exhibited no evidence of interlayer formation at pH values up to 9-7 (10 days). Chloritic intergrades formed at pH 10-7 did not collapse after K-saturation and heating at 300~ but did so at 550~ Hydroxy-Mg interlayers were not formed in either mineral by using a drying method. This method apparently failed to provide the required alkaline conditions for interlayer formation. The amount of magnesium interlayers present in the phyllosilicate systems decreased with time. The interlayers formed in vermiculite decreased more sharply than those in montmorillonite. Sequential dissolution treatments included boiling 2 per cent Na~CO3, buffered sodium citrate- dithionite, a second citrate-dithionite treatment, and boiling NaOH. Hydroxy-Mg interlayers in montmorillonite exhibited a higher stability to sequential treatments than the interlayers formed in vermiculite. A stable 14 ,~ line was observed in interlayered montmorillonite after the dithionite- citrate and NaOH treatments. The interlayers in montmorillonite showed a relatively high stability to HCI dissolution treatments. In contrast, most of the magnesium interlayer in vermiculite was removed by two HC1 washings. The reagents used in this study are sometimes used to remove coatings and cementing agents from soil surfaces prior to particle size and clay analysis. The present data show that these treatments also remove some hydroxy-Mg interlayers and produce changes in properties of clays, A proper interpre- tation of data for clay mineral identification and characterization must recognize these changes due to treatment. HYDROXY-Mg interlayers in phyllosilicates would be expected to occur in soils (Brydon, et al., 1961) and marine sediments (Rich, 1968), but they have received little attention compared to aluminum interlayers. Singleton (1965) reported the presence of hydroxy-Mg in addition to hydroxy-Al and -Fe in the interlayer space of clays from the Lookout series in Oregon. The formation of secondary chlorite in the dark magnesium clay soils of Hawaii and in Grumusols (Ladybrook Series) of Queens- land, Australia, was related to the hydroxy-Mg interlayering in montmorillonite (Jackson, 1959).

Adsorption studies on kaolinites

Abstract: Adsorption studies have been performed on Georgia kaolins having a broad range of crystallinity and particle size distributions (from 0·1μ to 44μ) using N2 (78°K.), H2O (273°K.), and BuNH2 (298°K.). Using both vapor and liquid phase adsorption techniques, surface affinities of the adsorbates were determined. Modified Frenkel-Halsey-Hill plots were used to compute the preferential adsorptivity of H2O vapor over N2 (hydrophilicity index, H.I.) as a function of crystallinity index, C.I., and particle size. For amine adsorptivity, non-aqueous adsorption isotherms were obtained. Within any geographic deposit, crystallinity exhibits an inconsistent pattern with respect to particle size. A single generality is the tendency for crystallinity to increase toward the fine particle size range, D → 0·2μ. Adsorptivities of N2, H2O, and BuNH2 show no dependence upon crystallinity within a given particle size range. However, F.H.H. compensated slopes, describing the preferential adsorptivity over N2, show a definite decrease as crystallinity increases. A striking anomaly occurs in the vicinity of 0·2 > C.I. > 0·7 where H.I. increases briefly then returns to the original trend. The rate of decrease of H.I. vs. C.I. is consistently steeper with increasing particle size. Adsorption of water vapor most likely occurs as a 1:1 configuration on each silica-alumina edge group, 1:1 on each basal silica, and 1:2 (hindered configuration) on each basal alumina group. The data suggest that amines adsorb preferentially and quantitatively on the edges, i.e. the Lewis and Bronsted acid sites, and follow a Langmuir pattern.

Differential release of potassium from interstratified mica clay minerals as related to probable differences in their mica layer components

Abstract: Release of potassium by extraction with solutions containing sodium tetraphenyl boron or by leaching with 0.1 N barium chloride seemed to be related to the nature of the mica layers in the interstratified minerals studied. The rate of potassium release was lower when the calculated Si/AlIV ratio of the mica component layers resembled muscovite and higher when this ratio was intermediate between muscovite and pyrophyllite. This supported a recent hypothesis that the composition and structure of the mica component layers may vary in different interstratified minerals of similar total chemical composition.

Effects of potassium removal on the b-dimension of phlogopite.

Abstract: Potassium was removed from 5 to 20-μ size fractions of two phlogopites by treatment with sodium tetraphenylboron and replaced with various exchange ions. The b-dimension of the mica increased with K+ removal, which suggests that the K+ ion in phlogopite acts to constrain b. This being the case, the K—O bond in phlogopite must be lengthened and weakened relative to the K—O bond in dioctahedral micas.

Extraction of Interlayer K from Phlogopite Specific Effects of Cations Role of Na and H Concentrations in Extraction Solutions

Abstract: The accurate optical observation of alteration fringes developing in phlogopite flakes, shows that the morphology of the fringes is specific for some cations, such as Na, Mg and Ca, replacing K. A careful chemical study of the exchange kinetics of interlayer K shows that, beside the classical effect of blocking the exchange reaction with cations such as K, Rb, Cs, NH4, it is possible to induce an increase of the rate of K exchange when adding to a concentrated solution of one cation, a very small amount of other cation such as Na or H. The effects of mixtures such as Ca-Na and Ca-H are reported here in detail. Attention is drawn to the decisive part played by the impurities which may be contained in the reagents used.