Amount Of Mg Ions Research Articles

Nanosized Silk-Magnesium Complexes for Promotion of Angiogenic and Osteogenic Activities.

Injectable hydrogels with osteogenic and angiogenetic properties are of interest in bone tissue engineering. Since the bioactivity of ions is concentration-dependent, nanosized silk-magnesium (Mg) complexes were previously developed and assembled into hydrogels with angiogenic capabilities but failed to control both osteogenic and angiogenetic activities effectively. Here, nanosized silk particles with different sizes were obtained by using ultrasonic treatment to control silk-Mg coordination and particle formation, resulting in silk-Mg hydrogels with different types of bioactivity. Fourier transform infrared and X-ray diffraction results revealed that different coordination intensities were present in the different complexes as a basis for the differences in activities. Slow Mg ion release was controlled by these nanosized silk-Mg complexes through degradation. With the same amount of Mg ions, the different silk-Mg complexes exhibited different angiogenic and osteogenic capacities. Complexes with both angiogenic and osteogenic capacities were developed by optimizing the sizes of the silk particles, resulting in faster and improved quality of bone formed in vivo than complexes with the same composition of silk and Mg but only angiogenic or osteogenic capacities. The biological selectivity of silk-Mg complexes should facilitate applications in tissue regeneration.

Surface Characteristics and Corrosion Behavior of Wire Electrical Discharge Machining Processed Mg-4Zn Alloy

In the present work, wire electrical discharge machining (WEDM) has been investigated for surface characteristics and corrosion behavior of Mg-4Zn alloy. Using Taguchi’s design of experiment technique, the influence of WEDM parameters, namely spark-on time, spark-off time, and servo voltage, has been studied on surface roughness (SR) and corrosion rate (CR). SEM observations showed that WEDM processing has a significant influence on the surface modification of Mg-4Zn alloy. Increasing discharge energy in the WEDM process has resulted in large surface craters, a higher density of micro-cracks, and micropores resulting in higher SR and accelerated CR in Mg-4Zn alloy. Corresponding to minimum SR and CR, the optimal set of WEDM parameters has been selected to prepare the WEDMed Mg-4Zn samples that were further analyzed for electrochemical polarization, apatite formation, and weight loss in simulated body fluid (SBF) and were additionally compared to polished samples of Mg-4Zn over a period of 21 days. Electrochemical polarization tests demonstrate that the CR increases rapidly upon the exposure time of 7 days; beyond that, the CR decreases with further exposure time up to 21 days. Initially, up to 24 hours, WEDMed samples showed better electrochemical corrosion resistance, whereas, later on, polished samples demonstrated an increased corrosion resistance for up to 21 days. Higher mineralization (or apatite formation) has been observed on WEDMed samples, which directly affects the amount of Mg ions released into the SBF solution; thus, weight loss was higher in the WEDMed sample than the polished sample. The weight loss for polished and WEDMed Mg-alloy samples after 21 days of immersion test was 9.3% and 13.5%, respectively. SEM analysis revealed the distinct corrosion morphology among the corroded surface of polished and WEDMed samples.

The promotion of magnesium ions on aragonite precipitation in MICP process

This study examines the magnesium ions effect on carbonate crystal polymorph when Ca(CH3COO)2/urea acts as cementation solution in microbially induced carbonate precipitation (MICP) process. The results of unconfined compressive strength (UCS) indicates that the involvement of Mg ions in Ca(CH3COO)2/urea cementation solution can greatly improve the physical and engineering properties of bio-cemented samples. Compared with the bio-cemented sample without any Mg ions, additional 0.01 M Mg ions in 0.5 M Ca(CH3COO)2/urea solution will contribute to 40% higher UCS, and additional 0.5 M Mg ions in 0.5 M Ca(CH3COO)2/urea solution will make the average UCS twofold higher. While, UCS of the samples treated with MgCl2/urea with poor crystallinity magnesium carbonate is one-tenth of that treated with 0.5 M Ca(CH3COO)2/urea. Furthermore, X-ray diffraction (XRD) analysis and scanning electron microscopy (SEM) with energy dispersive X-ray spectroscopy (EDS) images show that acicular aragonite and rhombohedral calcite are two main types of calcium carbonate crystal precipitated when Ca(CH3COO)2/urea acts as the cementation solution, and the incorporation of Mg ions modifies the crystal polymorph, promoting more aragonite precipitation but inhibiting calcite growth. The mechanism of magnesium ions effect on crystal polymorph is also summarized in the end. The efficiency of Ca(CH3COO)2/urea with a small amount of Mg ions is particularly noteworthy in MICP process.

Nanopatterned silk-coated AZ31 magnesium alloy with enhanced antibacterial and corrosion properties.

Because of unique properties such as the lightweight, natural biodegradability, and biocompatibility, magnesium alloys are promising in biomedical implants. However, inadequate corrosion resistance in the physiological environment remains a technical hurdle and application of coatings is a viable means to overcome the deficiency. Also, the antibacterial properties are very important in order to mitigate post-implantation complications arising from bacterial infection. In this study, a biocompatible silk film is deposited on AZ31 Mg alloy to enhance the corrosion resistance and by means of oxygen plasma etching, nature-inspired nanopatterns are fabricated on the surface of the silk film to improve the inherent antibacterial properties. The biocompatibility and antibacterial properties are determined with MC3T3-E1 osteoblast cells and E. coli and S. aureus, respectively. The antimicrobial properties of the silk coated AZ31 are better than those of the bare alloy probably due to the combined effects of the nanopatterns and alkalinity associated with leaching of Mg ions. The β-sheets formed on the silk film is found to result in 104 times reduction in the corrosion current density and 50% reduction in Mg leaching after 1day. Although degradation of the β-sheets is observed to begin after 1day, the amount of Mg ions leached to the medium from silk-coated AZ31 is still 17% lower than that from the bare one. The biomimicking nanopatterns on the natural silk film improve the corrosion resistance, biocompatibility, and antibacterial properties simultaneously and have large clinical potential.

Nanoscale ice-type structural fluctuation in spinel titanates

In the spinel titanate ${\mathrm{MgTi}}_{2}{\mathrm{O}}_{4}$, the tetragonal phase collapses upon substitution of a tiny amount of Mg ions at the Ti site, and the cubic phase with the geometrical frustration is resurrected. The atomic pair distribution function (PDF) and the extended x-ray absorption fine structure (EXAFS) reveal the nanoscale structural fluctuation, in which the Ti atomic displacement has the two-in two-out configuration in the cubic phase. We argue that the geometrical frustration plays an essential role in the collapse of the tetragonal phase and the resultant nanoscale ice-type structural fluctuation.

Magnesium-Free Spinel Oxides for Cathode Materials of Magnesium Rechargeable Batteries

Development of high potential rechargeable batteries (i.e., combining higher energy densities, higher safety, lower cost, etc) is strongly demanded for large-scale energy storage technologies, such as electronic vehicles and stationary electrical energy storage systems. Although lithium ion batteries (LIBs) are currently used for these purposes, their energy densities are approaching the theoretical limit. If Li metal could be used as an anode material instead of carbonaceous materials currently used, LIBs would have significantly high energy densities. However, the fatal problem that Li-metal dendrites are unfortunately formed in charge, which is responsible for short circuit, hinders construction of Li-metal-anode batteries. Mg metal can be an alternative to Li in that it can deposit non-dendritic formation. Furthermore, Mg metal is very attractive to realize high energy density; it has high theoretical capacity (2205 mAh g- 1), which is approximately six times larger than that of carbonaceous materials, and relatively low electrode potential (-2.38 V vs. SHE) among other candidates for anode materials. Especially, its high abundance and inexpensiveness are advantageous to practical application and elements strategy. Whereas magnesium rechargeable batteries (MRBs) have been seen as a potential candidate for next-generation battery, there are many difficulties to realize MRBs actually. One of the serious problem is that there are few cathode materials which can accommodate large amount of Mg ions at high potentials. Recently, we have substantiated several spinel oxides containing Mg and transition metals such as MgCo2O4, MgFe2O4, MgMn2O4, etc., for new cathode active materials[1]. For example, in the case of MgCo2O4, its discharge capacity approximately amounts to 200 mAh g-1 and the discharge potential is 2.0 - 3.0 V vs. Mg2+/Mg. These values are extremely high compared to that of Chevrel compounds[2]. In the previous work[1], by using CsTFSA based ionic liquid (melting temperature: c.a. 120 °C) for the electrolyte, we demonstrated that Mg cation was possible to be a carrier when the operated temperature was set at 150 °C. Furthermore, it was revealed that the spinel structure coherently transformed into rocksalt structure accompanied by the Mg2+ insertion, where the Mg2+ intercalation into vacant 16c sites (octahedral sites) of a spinel structure causes “push-out” of the cations located at the 8a sites (tetragonal sites) to other 16c sites, which eventually forms a rocksalt structure. Although these spinel oxides are attractive candidates for cathode materials of MRBs, there remains some problems in cycle properties. In the case of MgCo2O4, when the battery tests were conducted at 150 °C in the ionic liquid, the discharge capacity at high potential (~ 2.5 V vs. Mg2+ / Mg) decreases with an increase in charge/discharge cycles. This would be due to a difficulty of reverting to ideal initial spinel structure completely after cycling, which would depend on the fact that Mg has a nature of forming rocksalt-structure oxides, that is, Mg intrinsically tends to favor octahedral site. Furthermore, it is expected that such degradation would also be accelerated by its relatively large volume changes in charge/discharge cycles. Based on these assumptions, we examined magnesium-free spinel oxides such as X1(Co or Fe)2O4 (X = Ni, Zn). In ZnFe2O4, for example, its cycle property is found to be much improved in comparison with that of MgCo2O4, this would be because its lattice size based on the interatomic distance of oxygen anions is very similar to that in MgO and Zn is expected to favor tetrahedral site (in that ZnO forms wurtzite structure). Although its discharge potential is around 1.8 V vs. Mg2+ / Mg, being lower than that of MgCo2O4, an advantageous point is the fact that both Zn and Fe are inexpensive abundant elements. Thus, we can offer toiler-made spinel oxide materials for MRB cathodes.

Enhanced quantum efficiency with magnesium doping in europium-containing silicon oxynitride phosphor

Abstract Two types of europium (Eu)-containing silicon oxynitride phosphors were prepared by the polymer-derived method via polycarbosilane and Eu acetylacetonate with/without magnesium (Mg) acetylacetonate. The influences of Mg doping on the phase structure, surface morphology, microstructure and photoluminescence property of the Eu-containing silicon oxynitride phosphor were investigated. It was found that both the phosphors had almost single crystalized particles with a β-Si 3 N 4 like major phase and a strong emission band ranging 430–440 nm. Doping a small amount of Mg ions into the Eu-containing silicon oxynitride phosphor not only enlarged the crystalline and particle sizes, but also significantly enhanced the quantum efficiency from 34.53% to 93.81%. By comparing with the pure silicon oxynitride powder, possible mechanisms for the major emission band in the region of 430–440 nm and the shoulder emission band at around 550 nm are discussed.

Micromorphological effect of calcium phosphate coating on compatibility of magnesium alloy with osteoblast

Octacalcium phosphate (OCP) and hydroxyapatite (HAp) coatings were developed to control the degradation speed and to improve the biocompatibility of biodegradable magnesium alloys. Osteoblast MG-63 was cultured directly on OCP- and HAp-coated Mg-3Al-1Zn (wt%, AZ31) alloy (OCP- and HAp-AZ31) to evaluate cell compatibility. Cell proliferation was remarkably improved with OCP and HAp coatings which reduced the corrosion and prevented the H2O2 generation on Mg alloy substrate. OCP-AZ31 showed sparse distribution of living cell colonies and dead cells. HAp-AZ31 showed dense and homogeneous distribution of living cells, with dead cells localized over and around corrosion pits, some of which were formed underneath the coating. These results demonstrated that cells were dead due to changes in the local environment, and it is necessary to evaluate the local biocompatibility of magnesium alloys. Cell density on HAp-AZ31 was higher than that on OCP-AZ31 although there was not a significant difference in the amount of Mg ions released in medium between OCP- and HAp-AZ31. The outer layer of OCP and HAp coatings consisted of plate-like crystal with a thickness of around 0.1 μm and rod-like crystals with a diameter of around 0.1 μm, respectively, which grew from a continuous inner layer. Osteoblasts formed focal contacts on the tips of plate-like OCP and rod-like HAp crystals, with heights of 2–5 μm. The spacing between OCP tips of 0.8–1.1 μm was wider than that between HAp tips of 0.2–0.3 μm. These results demonstrated that cell proliferation depended on the micromorphology of the coatings which governed spacing of focal contacts. Consequently, HAp coating is suitable for improving cell compatibility and bone-forming ability of the Mg alloy.

Gas Formation and Its Effect After Implantation of Bioabsorbable Metal Magnesium

Category: Basic Sciences/Biologics Introduction/Purpose: Metallic biomaterials (stainless steel and titanium) are most commonly used for osteotomy and fusion surgery in foot and ankle. But it results in the physical and psychological burden to the patients owing to the second surgery (hardware removal). Bioabsorbable polymer has the disadvantages such as mechanically weak strength and osteolysis. To overcome these, bioabsorbable metal such as magnesium (Mg) implant have been developed recently and applied clinically, but it has also drawback such as gas formation by the biodegradation of magnesium alloys. However, there is no study on the characteristics of the gas formation and its effect on the surrounding tissue. The purpose of this study is to identify the characteristics of gas formation and histological reaction during the absorption of Mg on surrounding tissue using in vitro and in vivo rodent model. Methods: Pure Mg plate (15 × 15 × 2 mm) was immersed in EBSS (Earle’s balanced salt solution) for in vitro immersion test for 30 days. Intramuscular implantation of Mg plate (25×5×0.25 mm) was performed on twenty-four rat’s back muscle and divided as two groups: implantation and sham surgery. Gas volume and compositions, corrosion rate and surface morphology of Mg plate, and histological exam were evaluated at every 5 days for 30 days. Results: Gas is mainly composed of H2 (2.483 ×104± 0.028 μV), but a small amount of CO (93.428±0.14 μV) and CO2 (57.18±0.53 μV) was detected in in vitro immersion test. Gas volume shows significantly higher at 5 days (0.084 ml) than other times (0.005 mL for 30 days) after implantation, and is gradually decreased over time. Corrosion rate is also faster in at 5 days and decreased over time in both in vitro and in vivo study. Surface morphology shows a lot of cracks and the formation of apatite paticles on Mg plate. Histological examination shows that nuclei gathered densely around the small and multiple air bubble pocket at 5 days and the number of gas bubbles and their volumes were reduced over time in tissue surrounded implant, and there is no difference in kidney and liver tissue between implant and sham surgery. Conclusion: The immersion of Mg in EBSS generated H2 as the major forming gas, and CO and CO2. The in vivo implantation of Mg into rats’ back muscle generated gas pockets inside the tissues because the initial gas formation rate was faster than the gas- absorbing rate; however, gas volume decreased after 15 days as the gas formation and absorbing rates became similar. The amount of Mg ions inside the liver and kidneys changed as well, but it was within a normal range, such that inflammation and tissue deformation were not found.

Polycaprolactone coating with varying thicknesses for controlled corrosion of magnesium

Controlled corrosion of magnesium is critical for its clinical application to orthopedic devices. For this purpose, we coated the surface of Mg with a biodegradable polymer, polycaprolactone (PCL) and attempted to control the Mg corrosion with varied coating thicknesses in a reproducible manner. As we increased the coating thickness from 0 to 13.31 ± 0.36 μm, the volume of hydrogen gas and amount of Mg ions, the indicators of Mg corrosion, decreased by almost half from 0.57 mL/cm2/day and 0.55 mg/day to 0.20 mL/cm2/day and 0.26 mg/day, respectively. However, the elemental compositions on the surface revealed possible detachment of polymer coating and rapid water absorption at the early stage of corrosion for all coating thicknesses. Therefore, the lessons learned from this study suggest pre-treatment of the Mg surface for better polymer–metal adhesion, as well as preparation of the coating with lowered porosity as a stronger water-permeation barrier, to eventually allow precise control on Mg corrosion.

Preparation and properties of polyimide/graphene oxide nanocomposite films with Mg ion crosslinker

Polyimide(PI)/graphene oxide(GO) nanocomposite films were prepared by chemical cross-linking using small amounts of divalent Mg ions. The PI/GO nanocomposites showed enhanced tensile properties compared to pristine PI due to the presence of exfoliated GO in the PI matrix as well as crosslinking between poly(amic acid) (PAA), which is a precursor of PI, and GO by Mg ions. The hydrogen bonds between PAA and GO suppressed the phase separation between PI and GO, and small amounts of Mg ions can bond between the oxygen functional groups and carboxylate groups of GO and PAA.

Influence of magnesium ions and amino acids on the nucleation and growth of hydroxyapatite

It has long been known that magnesium (Mg) ions are effective inhibitors of hydroxyapatite (HAP) crystal nucleation and growth. During the HAP nucleation, it is now generally recognized that the involvement of assembled amorphous calcium phosphate (ACP) nuclei and prenuclei may be of greater importance in the overall crystallization mechanism. In the calcium-phosphate (Ca–P) biomineralization process significant amounts of Mg ions are present in animal skeletons where they are thought to stabilize ACP mineral phases. However, there is still some uncertainty concerning the precise roles of Mg in the nucleation and growth of apatite minerals. Herein, a slow, well-controlled, Ca–P crystallization study under a precisely defined thermodynamic driving force shows that Mg ions are able to prevent the nucleation of HAP in supersaturated Ca–P solutions by stabilizing gel-like ACP phases, prolonging the induction and subsequent transformation times, under near-physiological conditions (pH 7.400, ionic strength (I) = 0.150 mol L−1, 37.0 °C). Relatively large HAP crystals growing from the ACP surfaces were characterized by HRTEM and SEM. Surprisingly, EDS spectra revealed that no Mg ions were present in either the gel-like ACP or final crystalline phase. Following the addition of amino acids to the supersaturated solutions both in the presence and absence of Mg ions, the nucleation of HAP was promoted by shortening the induction and transformation times, and at the same time, the sizes of ACP and HAP crystals decreased as compared with the controls. Our results suggest that the formation of magnesium-phosphate (Mg–P) ion pairs may reduce the thermodynamic driving force for nucleation and phase transformation to HAP.

Quantification of MgO surface excess on the SnO2 nanoparticles and relationship with nanostability and growth

In this work, we experimentally showed that the spontaneous segregation of MgO as surface excess in MgO doped SnO2 nanoparticles plays an important role in the system's energetics and stability. Using X-ray fluorescence in specially treated samples, we quantitatively determined the fraction of MgO forming surface excess when doping SnO2 with several different concentrations and established a relationship between this amount and the surface energy of the nanoparticles using the Gibbs approach. We concluded that the amount of Mg ions on the surface was directly related to the nanoparticles total free energy, in a sense that the dopant will always spontaneously distribute itself to minimize it if enough diffusion is provided. Because we were dealing with nanosized particles, the effect of MgO on the surface was particularly important and has a direct effect on the equilibrium particle size (nanoparticle stability), such that the lower the surface energy is, the smaller the particle sizes are, evidencing and quantifying the thermodynamic basis of using additives to control SnO2 nanoparticles stability.

Adsorption of uranium from aqueous solution on heat and acid treated sepiolites

In this work adsorption of uranium on natural, heat and acid treated sepiolite was studied. For acid treatment HCl and H(2)SO(4) were used separately. Heat and acid treatment caused some changes in sepiolite such as surface area, micropore volume (cm(3)/g) and average pore diameter (A). Different amounts of Mg ions were extracted from the lattice depending on the type of acid. After acid treatment with HCl, the amount of Mg left in the sepiolite changed a little. During H(2)SO(4) treatment the sepiolite structure was progressively transformed into amorphous silica. These heat and acid treatments changed adsorption capacity and mechanism of uranium on sepiolite. Data obtained from the adsorption experiments were applied to Langmuir and Dubinin-Radushkevich (D-R) adsorption isotherms. Using these isotherms different adsorption capacities were found for natural and treated sepiolite samples. The capacity values were 3.58x10(-3), 3.14x10(-3), 2.78x10(-3) and 1.55x10(-3)mol/g for HCl treated, heat treated, natural and H(2)SO(4) treated sepiolite samples, respectively. In order to evaluate the adsorption mechanism adsorption energies were calculated by the D-R isotherm. According to the adsorption energy values uranium fixed to the natural and heat treated sepiolite surface with ion exchange (12.75 and 12.12 kJ/mol, respectively). Simple physical attractions were the driving force for adsorption on HCl and H(2)SO(4) treated ones (6.62 and 6.87 kJ/mol, respectively).

The effect of Mg doping on the Raman spectra of LiNbO3 crystals

AbstractLiNbO3:Mg crystals doped with 0‐8 mol% Mg with stoichiometric, intermediate and congruent compositions were systematically investigated by Raman spectroscopy in backscattering y(zx)y and y(zz)y geometries. The halfwidths of E(TO3) – E(TO9) and A1(TO1) – A1(TO4) bands, which have a significant composition dependence for undoped LiNbO3 crystals, show only weak Mg‐concentration dependence below the photorefractive threshold. This is a consequence of the counteracting effect of the decreasing amount of Nb ions at Li‐ion sites (NbLi) and increasing amount of Mg ions at Li‐ion sites (MgLi). The halfwidths of these bands, however, increase linearly with growing Mg content for samples above the threshold, irrespective of the Li/Nb ratio. The same effect was observed in the Mg dependence of the position and halfwidth of the two‐phonon band at about 689 – 705 cm–1. The change in the Mg concentration dependence of these parameters at a given Li/Nb ratio determines the same threshold value as that concluded from IR and UV spectroscopic measurements. (© 2007 WILEY‐VCH Verlag GmbH & Co. KGaA, Weinheim)

Template‐Dependent Morphogenesis of Oriented Calcite Crystals in the Presence of Magnesium Ions

Template‐Dependent Morphogenesis of Oriented Calcite Crystals in the Presence of Magnesium Ions

A bentonite bed in the Aceguá (RS, Brazil) and Melo (Uruguay) areas: a highly crystallized montmorillonite

Two occurrences of bentonite beds have been studied in Aceguá (RS, Brazil) and Melo (Uruguay). Despite their different thicknesses, the two profiles seem to belong to the same bentonite bed because of their similar petrographical and mineralogical properties (color, density, composition). Both are composed of a nearly pure smectite mineral that is dominantly a montmorillonite. High amounts of Mg ions in the octahedral sheet elevate the layer charge approximately 0.5 per Si 4O 10. The layer charge is mostly compensated for by Ca 2+ ions in the interlayer. The rare earth element (REE) patterns are different from the post-Archean Australian average shale (PAAS) standard. In particular, when the data are PAAS normalized, the pattern obtained shows that the bentonite is LREE depleted. Thus, it cannot have originated from detrital sources. Despite diagenetic conditions that favor the crystallization of random illite/smectite mixed layers from detrital clays in the surrounding formations, the mineral reactions in the bentonite bed are limited to a few Al for Si substitutions in the tetrahedral sheets. The clays remain dominantly montmorillonite with abnormally high crystallinity.

Salt Displacement and Titration of AlCl3‐Treated Trioctahedral Vermiculites

AbstractFreshly prepared and 45‐day‐aged Al‐saturated trioctahedral vermiculites from Libby, Montana, and northeastern Transvaal, South Africa, were: (i) leached with 1N and 0.05N solutions of NaCl, KCl, and CaCl2, (ii) subjected to repeated cycles of 1N NaCl leaching and Al saturation, and (iii) potentiometrically titrated in H2O or N NaCl. In the leaching experiments, the exchange acidity, exchangeable H, Al, and Mg, and the CEC after leaching were determined.Salt solutions displaced only part of the adsorbed Al, with less from South African than from Libby samples. Also displaced were H3O and small amounts of Mg ions. The exchange acidity (H3O + Al), the ratio of H3O to Al, the displaced Mg, and the apparent CEC after Al saturation and displacement varied with the kind and concentration of the displacing solution, the source of vermiculite, the aging period, and the number of cycles of Al saturation and displacement.With freshly prepared Libby samples, the exchange acidity varied from about 60 to 80% of the CEC, with Al constituting 60 to 90%. The corresponding ranges for South African samples were 35 to 50% and 30 to 85%. Of the three salts, KCl solutions gave the smallest exchange acidity and the lowest values for Al/exchange acidity; CaCl2 effected the highest values, with NaCl in between. Dilution of displacing solutions generally increased the H3O ion component of exchange actidity. Repeated Al saturation and displacement resulted in decreased exchange acidity.Potentiometric titration curves of Al‐vermiculites in H2O did not suggest the presence of appreciable amounts of exchangeable H3O. Titration curves in NaCl had buffer ranges interpreted as suggesting the presence of H3O, Al, and another component presumed to be mostly monohydroxy‐Al ions.The two Al‐vermiculites manifested by X‐ray analysis different collapsibility on K saturation and heat treatment. The X‐ray data support the conclusion that Al hydrolysis occurs between vermiculite plates, with general correspondence between the amount of nonexchangeable Al and the failure of the minerals to collapse to 10A upon K saturation and drying.