The i.r. spectrum of K depleted biotites (structural OH stretching range) has been studied with monocrystals equilibrated at various water contents. Prior to spectroscopic measurements, the samples were submitted to deuteration treatments which displaced the hydration water spectrum to the OD region and made it possible to observe the behaviour of the structural hydroxyls without interference from hydration water.

In these conditions it was shown that the high frequency absorption of K depleted biotites (N + I bands) is the sum of two absorptions: the first corresponds to the initial mica spectrum, the second corresponds to the hydrated phase in which component bands (according to Vedder and Wilkins) are shifted by 36 cm-1 towards low frequencies.

Simultaneously it was shown that low frequency bands (V bands) decreased in intensity. This unexpected observation has been explained by a partial deuteration of structural OH, which takes place during the preliminary contacts of the samples with D2O vapour.

The Olympic Games have grown to be the largest, gender-equal sporting event in the world, and the International Olympic Committee is committed to gender equality in sports encouraging and supporting the promotion of women in sports at all levels and in all structures with a view to implementing the principle of equality of men and women (IOC, 2023). Women competed for the first time at the 1900 Olympic Games in Paris, and the number of women competing has grown exponentially over the last 100 years, so an estimated 5494 female athletes (48 %) competed in the Summer Olympic Games 2021 in Tokyo. Supporting women (alongside men) in achieving optimum performance is crucial, and understanding that there are sex and gender gaps in sports nutrition research is important. One reason for this gap is the historical bias in sports and exercise science research towards male participants. This has led to a poor understanding of the unique physiological and nutritional needs of female athletes. In summary, a balanced approach is crucial to address the nutritional needs of both male and female athletes. Researchers should continue exploring this important area to optimise performance and health for all athletes. The aim of this review is to summarise current sports nutrition literature and highlight research that seeks to understand and address where the gaps are with respect to several key areas in sports nutrition recommendations that can impact advice and practice with both males and females.

Organic diacid (oxalic and succinic) adsorption onto montmorillonite is feasible, but weak (~1 mg/g). The comparison of chemical and radiochemical determinations reveals that 80% of the acid in contact with the smectite is used to attack the clay lattice. The pH is the main parameter involved in adsorption, and fixation passes through a minimum for pH 6 to 7. Polyacrylate adsorption is also weak (~1.5 mg/g). It changes with the nature of the exchangeable cation of smectite. Its pH-dependence displays a pronounced maximum for a value corresponding to the pKa of the acidic functions (pH ~6.8), and a minimum at about pH 8. On the assumption that a polyacrylate macromolecule is 100% hydrolyzed, it follows that the-COOH groups carried by 20% hydrolyzed Polyacrylamide molecules (such as those used in the tertiary recovery of petroleum) contribute at the very most to 10% of the total adsorption onto clay. Fixation, therefore, involves predominantly protonation of the amide functions at the edge surfaces of the clay. The acidic functions play a minor role in the adsorption phenomenon in that they affect the length of the macromolecule. The extent of this contribution, however, is virtually impossible to estimate.

The oxidative power of a smectite can be measured quantitatively by oxidation of hydro-quinone to p-benzoquinone in a clay slurry. Oxidation takes place in the presence of O2 (air) but not N2 unless Fe3+ or Cu2+ are the exchangeable cations. This study examined 26 smectite samples with varying compositions and processing. The oxidative power increases with decreasing Li-fixation and increasing cation exchange capacity. Li-fixation does not depend upon the tetrahedral Al. The cation exchange capacity can decrease markedly by mere storage in water.

The oxidation proceeds principally on the surface by adsorbed oxygen molecules or radicals. A mechanism is proposed. With Fe3+ or Cu2+ present, even under N2, oxidation occurs via electron transfer. With smectites containing Fe2+, both the Fe and the hydroquinone are oxidized in the same reaction.

pH- and conductometric titration curves of acid sauconite, freshly prepared by the action of H-resin on sauconite showed four segments, each, where H+, Al3+ and Zn2+ ions and a weak acid reacted with the added base in the sequence mentioned. The H+, Al3+ and Zn2+ ions, but not the weak acid, could be exchanged for the cations of a neutral salt. The exchangeable Al3+ and Zn2+ ions were derived from the lateral surfaces by the action of the H-resin. When the acid sauconite was allowed to age in water, the exchangeable H+ and Al3+ ions were gradually replaced by Zn2+ ions giving, finally, a Zn-clay. The pH rose from 4·2 to 6·3 and the total amount of exchangeable cations increased as aging proceeded. When the Zn-clay was formed, the increase in cation exchange capacity was about 70 per cent. Octahedral Al at the edges, carrying positive charges, were discharged by hydrolysis during the aging, causing the net negative charge and, hence, cation exchange capacity, to increase. Aging had little effect on the amount of the weak acid. Zn and Al ions at the edges exhibited the weak acid function. Only edge-Zn was active in the fully aged clay.

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.

The adsorption of CO2 at low temperature (~ -70°C) on thin films of homoionic smectites was studied by X-ray diffraction and by i.r. absorption. An increase in the d001 spacings of these clay films upon adsorption of CO2 was observed. In addition, a dichroic effect was readily discernible by comparing the i.r. spectra at two different orientations of the smectite films; i.e. with the film normal and tilted 35° with respect to the i.r. beam. The CO2 stretching vibration at 2350 cm-1 was used for the i.r. study. These observations conclusively show that CO2 intercalates the smectite structure rather than being adsorbed only in pores between clay tactoids—the limiting process proposed by other investigators.

Adsorption isotherm data from earlier surface area studies are re-examined here through application of the Dubinin equation. Again, intercalation is demonstrated by convergence of the plotted experimental data for smectites containing large monovalent interlayer cations toward a pore volume that is near the calculated theoretical value for a monolayer of intercalated CO2.

Scanning electron photomicrographs of Li- and Cs- smectites provide additional evidence that aggregation differences are not responsible for the large observed difference in BET surface areas obtained for these smectites with CO2 as the adsorbate. At low magnification, visual differences in macro-aggregates are apparent, but at high magnification no significant differences are observed in the micro-structure of individual aggregates where the major amount of gas adsorption really occurs.

Various kaolinites, a dickite and halloysites have been treated by DMSO in presence of D2O and subsequently washed by D2O. This procedure allowed to record OD stretching bands which are due specifically to the intercalated fraction and, for the washed samples, to the fraction of the solid which has been intercalated and has subsequently collapsed.

No structural difference is found between the intercalated materials prepared from the various minerals. Washing usually restores the starting mineral; however, for a non-tubular halloysite, DMSO intercalation and subsequent washing gave a product similar to kaolinite.

Shales from six locations in Oklahoma were subjected to natural weathering for 2 yr. Simulated weathering of these shales was effected in the laboratory by subjecting them to ultrasonic treatment in a tank type device. Both treatments produced disaggregation. X-ray diffraction patterns for the ultrasoni-cally treated and weathered shales indicated no major changes in the types of clay minerals. However, natural weathering in the field produced degradation of the clay minerals in addition to disaggregation of the shales. Ultrasonic treatment appears to be a good predictive test for determining the durability and weatherability of the shales; however, it can simulate field weathering only so far as the engineering index properties of the shale are concerned. It is not a predictive test where the mineralogical characteristics are of significance.

Petrographic studies have shown that brucite is a major constituent of the New Idria serpentinite and of the short-fiber asbestos deposit associated with it. Acid-leaching data suggest that the serpentinite averages 7–8 weight per cent brucite, which contains approximately 15 mole per cent “Fe(OH)2”. Unit cell parameters and electron probe analysis suggest an empirical formula close to (Mg10Fe2)(OH)24 for this phase. Brucite formed during the initial serpentinization of an olivine-rich parent and is concentrated today in the hard, dense serpentinite fragments scattered throughout a highly sheared matrix of soft, friable asbestos. Although brueite is abundant in the fresh serpentinite it is almost absent from the surface weathering zone, which persists to a depth of 20–30 ft across the entire body. Here, serpentinite fragments have oxidized and brueite has transformed in situ into pyroaurite [Mg6Fe2CO3(OH)16.4H2O] and a new mineral, coalingite [Mg10Fe2CO3(OH)24.2H2O]. Brueite in the matrix material has dissolved in the CO2-rich ground waters, yielding soluble magnesium ions and amorphous iron oxides which discolor the surface asbestos.

In the laboratory, samples of fresh serpentinite oxidized and disintegrated completely when exposed to the atmosphere for a few months, due to the brucite-coalingite transformation. In the presence of O2 and CO2, brueite dissolved completely from a water slurry of the serpentinite, yielding a dark brown residue and a clear filtrate which later precipitated hydromagnesite [Mg4(OH)2(CO3)3.3H2O]. These data indicate that in the relatively impervious environment of the residual serpentinite “boulders”, iron-rich brueite oxidizes in air, picking up CO2 and H2O to form coalingite. In the presence of excess ground waters, brueite in the friable matrix dissolves, leaving behind a residue of amorphous iron oxides. Dissolved magnesium ions later precipitate as hydromagnesite, which is also abundant in the surface weathering zone of the serpentinite.