A sample of ferripyrophyllite, a mineral with ideal composition Fe2SiO10(OH)2, was analyzed by Mössbauer spectroscopy, magnetization and magnetic susceptibility measurements. The iron is entirely ferric, and the main feature of the Mössbauer spectrum at room temperature is a single absorption line with isomer shift δ = 0.36(1) mm/sec due to iron in M2 sites. The line is broadened by a slight quadrupole splitting Δ = 0.18(1) mm/sec, the smallest yet reported for a sheet silicate. Weaker features corresponding to quadrupole doublets with relative intensities of 7% and 8% having δ = 0.43(1) mm/sec; Δ = 1.22(2) mm/sec and δ = 0.14(1) mm/sec; Δ = 0.59(2) mm/sec are assigned to ferric iron in nonequivalent octahedral and tetrahedral sites, respectively, giving the following formula, based on published chemical analysis: Ca0.05(Fe3+1.87Mg0.11Al0.09)VI(Si3.80Fe3+0.16Al0.04)IVO10(OH)2, where Ca is in interlayer sites. Ferripyrophyllite orders antiferromagnetically at 18(2)°K. The Mössbauer spectrum at 4.2°K consists of a single, resolved magnetic pattern with hyperfine field Bhf = 51.8 T. The relatively high Néel temperature compared with other dioctahedral ferric phyllosilicates provides further evidence that Fe3+ cations tend to be ordered on M2 sites within the octahedral sheet.

Polycations of limited molecular size were prepared from 0.1 M solutions of Fe(III)(NO3)3 and A1(NO3)3 by ultrafiltration. Various amounts of the polycations were added to Na-kaolinite, Na-mont-morillonite, and a Na-soil clay and the effect on the flocculation of the clay and electrophoretic mobility compared. Flocculation occurred just before zero net charge was obtained. Addition of further polycation resulted in the dispersion of clay with a net positive charge. The Al polycations possessed a high positive charge (0.49 per gram atom of Al), and their interaction with the clays indicated a planar shape. Adsorption of Al polycations decreased markedly the cation-exchange capacities of the kaolinite and the soil clay but had little effect on surface areas determined by low-temperature N2 adsorption. The Fe polycations were spheres 10–100 Å in diameter with a positive charge of 0.2 per gram atom. The surface areas of the kaolinite and the soil clay were substantially increased by the addition of the Fe polycations but their cation-exchange capacities were reduced by one fifth. Al polycations increased the surface areas of the montmorillonite (to 300 m2) presumably by propping open the interlamellar spaces and rendering the a-b planes accessible for nitrogen adsorption. The Al polycations in interlamellar spaces prevented collapse to 14 Å on heating to 150°C. There was no evidence of regular interlayer Fe as might be anticipated from the size of the spheres.

Photon correlation spectroscopy (PCS), a dynamic light-scattering technique for particle size measurement, was used to determine the coagulation rates of aqueous dispersions of relatively monodisperse South Carolina Peerless kaolinite, Silver Hill, Montana, illite, Wyoming montmorillonite, and Florida palygorskite. This technique allows quantitative measurement of the rate of coagulation for clay particles where the traditional turbidity method gives only a qualitative measure. The critical coagulation concentrations for KCl at pH = 10.0 were: 0.199 M for kaolinite, 0.202 M for illite, 0.290 M for montmorillonite, and 0.034 M for palygorskite. The effective Hamaker constants, calculated using Derjaguin-Landau-Verwey-Overbeek theory, were: 3.1 × 10−20 J for kaolinite, 2.5 × 10−20 J for illite, 2.2 × 10−20 J for montmorillonite, and 1.63 × 10−19 J for palygorskite. Stern potentials at the critical coagulation concentration at pH 10.0 were: −42.7 mV for kaolinite, −40.7 mV for illite,‒21.2 mV for montmorillonite, and −66.9 mV for palygorskite.

Activity expressions are presented for a six end-member, regular solution, site-mixing model for chlorites. The end members are ideal 14-Å chlorites for which experimental stability data are lacking. Estimates were made of the standard state 25°C and 1 bar molar 3rd law entropies, volumes, and the Maier-Kelley heat capacity coefficients. Experimental stability data from the literature for 14-Å chlorites were used with different sets of exchange energies, for cations on adjacent sites, to compute estimates of the standard state chemical potentials of the end members at 25°C and 1 bar. More experimental data are needed for an adequate definition of the exchange energies and the standard state chemical potentials. The model was applied to diagenesis in clastic reservoirs. Aqueous activity ratios of Mg2+:Fe2+ were computed as an equilibrium function of the corresponding molar ratios in authigenic chlorites. The aqueous activity ratio was independent of the chlorite Al content at a constant molar ratio of Mg2+:Fe2+ in the chlorite. The model predicts a wide range of molar Mg2+:Fe2+ ratios in authigenic chlorites in equilibrium with reservoir fluids. Trends in these molar ratios should be independent of the Al content in the chlorites. The model can be applied directly to 7-Å chlorites when experimental data become available to estimate the various thermodynamic parameters of the 7-Å end members.

Several new, room-temperature luminescent phenomena, resulting from the interaction of kaolin and various amino compounds, have been observed. The emission of light from kaolin pastes (treated with quinoline, pyridine, hydrazine, monoethanolamine, n-butylamine, and piperidine) was shown to decay monotonically over a period of hours to days. More light was released by a given amino compound after it was dried and purified. Hydrazine, in addition to the monotonically decaying photon release, produces delayed pulses of light with peak emission wavelength of 365 nm which last between several hours and several days. These photon bursts are acutely sensitive to the initial dryness of the hydrazine, both in the number of bursts and the integrated photon output. The amount of light and the capacity of the kaolin to produce the delayed burst appeared to be strongly dependent on preliminary heating and on gamma-irradiation, analogous to the dehydration-induced light pulse previously reported from the Ames Research Center. A small, delayed burst of photons occurred when piperidine and n-butylamine were removed by evaporation into an H2SO4 reservoir.

Adsorption of Cu2+ and Co2+ by synthetic imogolite, synthetic allophanes with a range of SiO2/ Al2O3 ratios, and allophanic clay fractions from volcanic ash soils was measured in an ionic medium of 0.05 M Ca(NO3)2. The effect of pH (and metal concentration) on adsorption was qualitatively similar for the synthetic and natural allophanes with relatively minor changes in behavior caused by variable SiO2/Al2O3 ratios. Cu and Co were chemisorbed by allophane at pH 5.0–5.5 and 6.9–7.2 (pH values for 50% adsorption level), respectively, with concomitant release of 1.6–1.9 protons/metal ion adsorbed. Quantitatively, adsorption by imogolite was less than that by the allophanes, presumably because of fewer sites available for chemisorption on the tubular structure of imogolite. Electron spin resonance studies of the imogolite and allophanes revealed that Cu2+ was adsorbed as a monomer on two types of surface sites. The preferred sites were likely adjacent AlOH groups binding Cu2+ by a binuclear mechanism; weaker bonding occurred at isolated AlOH or SiOH groups. These chemisorbed forms of Cu2+ were readily extracted by EDTA, CH3COOH, and metals capable of specific adsorption, but were not exchangeable. In addition, the H2O and/or OH− ligands of chemisorbed Cu2+ were readily displaced by NH3, with the formation of ternary Cu-ammonia-surface complexes.

Resilication of bauxite produced kaolin at and beneath an old erosion surface on bauxite at the Alabama Street Mine of ALCOA in Saline County, Arkansas. The transitional alteration can be traced in morphology by scanning electron microscopy, (SEM) and in Al:Si ratio by energy dispersive analysis. In one illustrated example, the sequence of resilication took place within 1 mm thickness; in another, across 80 mm. The first morphologic alteration of gibbsite (bauxite) appears to be to allophane that occurs in micrometer-size plates which show elongate cracking and/or straight to highly curved elongate edges. The next phase is kaolinite, first in micrometer-size flakes followed by coarser flakes that grade into a zone of typical stacked kaolinite, likewise identified by X-ray powder diffraction. Notably large stacks and small flakes of kaolinite are intimately mixed in the SEMs, thus suggesting that unequal sizes of kaolinite crystals can grow during one episode of an in-situ genesis.

The effect of the surface acidity of montmorillonite and kaolinite on the hydrolysis rate constants of different agricultural chemicals was studied at variable moisture contents. Ethyl acetate, cyclohexene oxide, isopropyl bromide, 1-(4-methoxyphenyl)-2,3-epoxypropane, and N-methyl p-tolyl carbamate were chosen as representatives of classes of chemicals that exhibit acid-catalyzed, base-catalyzed, and neutral hydrolysis. In addition to being commercially available in pure forms, these chemicals have well-characterized homogeneous kinetics. The presence of montmorillonite or kaolinite in water suspensions had a small effect on the hydrolysis rate constants (kh), whereas, the addition of moisture to oven-dried clays up to the limits of sorbed water resulted in an increase in the rate of hydrolysis of the epoxide by a factor of 10.

The increase in the hydrolysis rate constant suggests that the surface pH of montmorillonite or kaolinite might be 1–2 pH units lower than the bulk pH. The kh value for the carbamate on Na-montmorillonite surface (bulk pH = 8.5) is 6.4 × 10−8/sec which is equivalent to the rate constant at pH values ≤7. The hydrolysis rate constant of the epoxide was reduced by a factor of 4 when the moisture content exceeded the limit of sorbed water. The addition of humic acid to the clay minerals resulted in about a 40% reduction of the epoxide hydrolysis rate constant.

Ferrous or ferric Perchlorate, 0.01 M, was reacted with calcite in stirred aqueous suspensions which were bubbled vigorously with an oxidizing purge gas. Two and three equivalents of CaCO3 were dissolved per mole of Fe2+ and Fe3+ neutralized, respectively. With Fe(ClO4)2, the crystalline Fe oxide products partially coated the calcite surface. The dominant products were lepidocrocite and goethite when the purge gas was air or 20% CO2 (balance air), respectively. After reaction with Fe2+ the edges and corners of the calcite crystals were generally rounded and the faces were non-uniformly pitted; however, after reaction with Fe3+, a mosaic pattern with distinct ridges and channels was evident on the calcite. These ridges were somewhat pitted, but distinct stepped dislocations were present leading to a featureless and generally flat channel floor. When the calcite was separated from the Fe solution by a semi-permeable membrane, precipitation occurred predominantly on the calcite side and on the Fe side of the membrane in the Fe2+ and Fe3+ systems, respectively.

Fe oxyhydroxides precipitated from the Fe(ClO4)3 and Fe(ClO4)2 solutions by different mechanisms. In the Fe(ClO4)3 system, although the initial reaction may have been at the calcite surface, the bulk of the poorly crystalline ferrihydrite was formed by hydrolysis of Fe polymers in suspension. Neutralization occurred by the reaction with basic products of a surface-controlled dissolution of calcite, rather than by a direct reaction of acidic polymers with the calcite surface. In the Fe(ClO4)2 system, lepidocrocite or goethite formed by the partial hydrolysis of Fe2+ or Fe3+ by reaction with calcite or the basic products of calcite dissolution and subsequent precipitation of simple Fe species on existing FeOOH nuclei.

White saponite occurs in joints and open fracture zones in metamorphosed dolomitic limestone near Ballarat, California. The saponite appears to have formed by hydrothermal alteration, possibly during Pliocene times. The material shows a 06l X-ray powder diffraction peak at 1.529 Å, A12O3 and MgO contents of about 4.4 and 23.5%, respectively, and a half-cell octahedral atoms summation value of about 2.82. The saponite appears to consist of a single, uniform clay species; the main impurities are fine shards of diopside and tremolite. The infrared and thermal properties of the Ballarat saponite are similar to those of the Allt Ribhein saponite. It has a lower water-holding capacity than montmorillonite and is characterized by lower Atterberg limits and expansion pressures and higher compaction densities. The apparent density of the saponite, 2.865 g/cm3, is greater than that of montmorillonite. This saponite is available from the Source Clays Repository of The Clay Minerals Society.

The exchange of Na, K, and Ca ions in vermiculite has been studied between 50 and 150°C at a total normality of 0.1. The free energy changes were negative in the Na → K, Ca → K, and Na → Ca exchange reactions, and the cation preference in the vermiculite was Na < Ca < K in the temperature range examined. The enthalpy changes, calculated by application of the van't Hoff equation to the relation between equilibrium constant and temperature, were positive. The cation preference in the vermiculite seems to have been largely controlled by the increase in entropy which was due to the positive values of the entropy change term in the solid for the Na-K and Ca-K exchanges and the positive values of the entropy change in the solution for the Na-Ca exchange. From a thermodynamic analysis of the cation-mixing properties in vermiculite, the observed free energy change in the Na-K exchange was determined solely by the differences of the intrinsic electrostatic binding energy of the cations on the clay surface. That in the Na-Ca exchange was interpreted by taking into account an extra interaction energy of Ca-Ca pairs in addition to the intrinsic energy change. Furthermore, an additional interaction energy between K ions and the clay surface appears to have been added to the free energy change in the Ca-K exchange. In the Na → K and Ca → K exchange reactions a structural modification occurred in the K-equivalent fraction (X̄K) range 0.05–0.6, and a regularly interstratified phase of 15-Å and 10-Å members was formed at 0.05 < X̄K < 0.4.

Copper adsorption on a hydroxy-aluminum-hectorite complex (OH-Al-hectorite) at pH 4.5, 5.7, 7.4, and 7.8 was examined by means of electron spin resonance. The spectra of these samples were compared to those of Cu2+-hectorite and various aluminum hydrous oxides. Copper on the OH-Al-hectorite in aqueous gels occurred as mobile Cu(H20)62+ and chemisorbed to discrete sites of the OH-Al interlayer. As pH was increased, the ratio of chemisorbed to mobile Cu2+ increased. At pHs above 7 the solubility product of Cu(OH)2 was exceeded, but chemisorbed Cu2+ remained as the dominant species. These results contrast with the precipitation of Cu observed on microcry stalline gibbsite above pH 5 and indicate that the interlayer OH-A1 retained more Cu2+ on discrete sites. The greater adsorption capacity probably resulted in part from a higher specific surface area. Electron spin resonance spectra of Cu2+ in air-dried films of the OH-Al-hectorite at pH 4.5 and 7.4 showed Cu2+ in square planar symmetry, oriented with the z-axis perpendicular to the OH-Al-hectorite a-b plane. At the higher pH, the spectrum resembled that of Cu(OH)42- on alumina, suggesting a ligand exchange mechanism for Cu2+ adsorption on the complex.

Sulfate adsorption on kaolinite was followed at 0.7 μeq/ml to 99 μeq/ml solution concentrations at 30°C and at pH 6.0, and the amount of OH~ ions released and the change in surface charge were determined. Sulfate was adsorbed at positive and neutral sites by displacing OH2 and OH− groups, respectively. Adsorption of sulfate occurred predominantly at positive sites at low (0.7 μeq/ml to 0.9 /μeq/ml) solution concentrations, whereas at higher solution concentrations, the proportion of the sulfate adsorbed at the neutral sites increased, varying from 51% at 4.9 μeq/ml to 68% at 99 μeq/ml. The form of sulfate bonding was apparently governed by the level of the positive charge on the clay surface. Higher positive charge at low and intermediate levels of sulfate saturation resulted in the adsorption of sulfate as a divalent anion by forming a 6-member ring with surface Al. With a decrease in positive charge at higher levels of adsorption, the sulfate ion formed both monodentate and bidentate complexes.

The gas-phase adsorption of trimethylphosphine onto hectorite, exchanged with Co(II) and Ni(II), gives trigonal complexes of the type [M(Ol)3(PMe3)]2+ (M = Co, Ni). Ten Dq values of PMe3 are 2.1 and 2.4 times larger than those of the structural oxygens or solvent molecules. The same complexes form between dimethylphenylphosphine and Ni(II) on hectorite and on synthetic zeolite Y. Co(II) forms pseudotetrahedral complexes with dimethylphenylphosphine ligands. These surface-immobilized transition-metal complexes interact strongly with NO and CH ≡ CH and to a lesser extent with CO and CH2=CH2, giving new types of complexes.

An X-ray diffraction study of aqueous emulsions of a Na-montmorillonite shows that: (1) At low water content, the d-spacings of the montmorillonite increased stepwise with increasing water content; (2) At high water content, sharp (001) peaks due to regular stacking of montmorillonite layers were not detectable, but broad, halo patterns were observed in the low-angle scattering region; and (3) The addition of Ca2+ or H+ to the aqueous emulsions caused Ca-montmorillonite or H-montmorillonite crystals to form. A zig-zag column model of montmorillonite layers fits the observed data for aqueous emulsions of Na-montmorillonite.