Recent mud sediments of Mississippi Sound, Mobile Bay and contributory rivers contain a clay mineral assemblage composed essentially of kaolinite and montmorillonite. Illite is present as a minor component.

The montmorillonite in these sediments appears to be at least partially complexed with organic material. This association is particularly evident in river and river mouth deposits and seems to be modified or partially destroyed in sea water. Organic material has been leached from river sediments with a sodium hydroxide solution and combined as a clay-organic complex with montmorillonite from Clay Spur, Wyoming.

The clay mineralogy of sediments from Mobile Bay and areas outside of the barrier island chain is very similar to that of the river sediments. Within Mississippi Sound an apparent increase in the montmorillonite-illite content of the sediments relative to kaolinite from east to west is attributed to the invasion of mud from the Mississippi Delta into the western part of the Sound.

Chemical analyses of these sediments along a section from fresh water to Mississippi Sound localities have shown a progressive increase in magnesium, potassium, and sodium, and a decrease in calcium.

When dehydroxylation of kaolinite powder is carried out in the usual way, the linear relations anticipated for first-order kinetics and for the Arrhenius plot of log k versus 1/T are satisfied only very approximately. Factors relating to the form of the specimen, (shape, size, compaction, container, etc.) are shown to be very important. A method is developed for obtaining data for a specimen in the form of an infinitely thin disc. The first-order kinetic relation and the Arrhenius relation are then linear, and the latter gives an activation energy of 65 K cal./mol. The dehydroxylation process is shown by x-ray analysis to proceed crystal by crystal and this leads to an interpretation of the first-order kinetics. The x-ray method is used to study the distribution of reacted and unreacted material throughout a disc of material. Although isothermal conditions are employed, large differences are found between the interior and exterior of a partially dehydroxylated disc. These effects are attributed to the influence of a water vapor atmosphere within the heated disc.

X-ray diffraction patterns and cation-exchange data are presented for centrifuged Wyoming bentonite to demonstrate the heterogeneous nature of montmorillonite. It has been shown that in the bentonite samples studied, the montmorillonite can be separated into at least two fractions. One phase consists of essentially a sodium montmorillonite while the other consists of essentially a calcium-magnesium montmorillonite. It is postulated that these differences occur because of differences in the isomorphous substitutions within the montmorillonite crystal lattice.

Treatment of a muscovite (Delamica) with molten lithium nitrate produced a lowering of the layer charge on the mica. By gradual reduction of the density of surface charge the dependence of interlamellar expansion on the attainment of a critical value of about 6.7 × 104 e.s.u./cm2 was demonstrated in a straightforward manner.

Diffraction from oriented flakes of four montmorillonites that had been treated with an excess of four glycols was obtained. Peak areas for the 00l diffraction from each of the treated clays were plotted against sin θ/λ.

It was assumed that the observed diffraction intensity for the complexes was equal to that of the clay plus or minus that of the organic part of the complex. By assuming also that the contribution from the organic part of the complex is the same for each clay at any one value of sin θ/λ, a systematic consideration of all the possible levels of contribution by the organic interlayer material could be made. At values of sin θ/λ where intensity data were closely spaced, it was found that only one of the possible levels of contribution by the organic interlayer material would allow a residual intensity (attributable to the clay) that fit on smooth curves.

Curves of the diffraction intensity attributable to each of the clays resembled, in their gross features, the calculated structure factor curve of mica. Displacements of the nodes along the sin θ/λ axis and differences in loop heights are sufficient to make this experimental structure factor curve for each of the five clays quite distinctive.

Organophilic bentonites prepared by reacting various amounts of n-laurylamine hydrochloride and dimethyldioctadecyl ammonium chloride with bentonite have been studied by the method of Fourier transforms. The transform curves obtained from the x-ray diffraction patterns of these samples show how different numbers of organic layers between clay laminae are produced by different kinds and amounts of organic material added to the clay. It has been found that as the organic material reacts by base exchange with the clay surfaces, the number of organic layers between each two clay platelets increases in a regular and stepwise manner.

Glycerol-treated montmorillonite gradually loses one layer of the normal two-layer glycerol complex upon moderate heating at 110°C, forming a monolayer complex with a sharp x-ray diffraction peak at about 14A. In the presence of free glycerol vapor, this complex is quantitatively stable on further heating. A simple gravimetric procedure has been devised to determine the weight of glycerol retained. The procedure involves addition of a dilute glycerol solution to a dried and weighed sample of clay in an aluminum foil dish, and subsequent oven drying over a glycerol surface until constant weight is attained. The portion of the glycerol retained on external surfaces is assessed by measuring the retention of a replicate sample previously collapsed irreversibly by heating at 600°C or higher.

The retention of monolayer glycerol complexes of vermiculite and endellite can be similarly determined. Ethylene glycol forms an analogous series of complexes, and its retention against heating can be measured in exactly the same way. Differential thermal analysis of glycerol- and glycol-treated montmorillonite suggests that both complexes decompose with endothermic reactions at about 300°C.

Glycerol retention values were shown to be independent of sample size and to be almost independent of equilibration temperature between 70°C and 150°C. As expected, they are inversely proportional to particle size. Cation saturation affects the values of both internal and external retention for montmorillonites. It is shown that retention is a function of montmorillonite content in a series of artificial mixtures. Glycerol retention values of a number of clay materials are presented.

The use of glycerol retention measurements to calculate surface areas of clay minerals is described. Assuming that the glycerol retained on external surfaces is monomolecular in thickness, and that both this layer and the monomolecular glycerol layers adsorbed on internal surfaces of montmorillonite, vermiculite, and halloysite are of the density of liquid glycerol, it is calculated that each percentage of glycerol retained corresponds to an area of 17.6 square meters per gram on external surfaces and 35.3 on internal surfaces. The corresponding figures for ethylene glycol retention under these conditions are 22.3 and 44.6, respectively. For nonexpanding clays, surface areas calculated from glycerol retention values agree well with published figures derived from Brunauer, Emmett, and Teller (B.E.T.) gas adsorption measurements. For montmorillonites, surface areas agree reasonably well with published determinations based on B.E.T. treatment using polar adsorbates. Values of surface area are also presented for samples of vermiculite and endellite and for the nonexpanding clay minerals—illite, kaolinite, halloysite, and allophane.

Calculations of the surface area as a function of particle size for montmorillonites of hypothetically uniform particle sizes show that montmorillonites dispersed into very thin flakes must have an appreciable external surface. The ratio of internal to total surface is shown to furnish an estimate of the thickness of the individual montmorillonite flakes. Glycerol retention data for a Wyoming bentonite saturated with a number of different cations are interpreted as indicating particle thicknesses varying from 3 unit cells (about 30A) for Na+ saturation to about 20 unit cells for saturation with a number of polyvalent cations.

Stabilities of Mg-, Ca-, and Na-montmorillonite- and vermiculite-glycol complexes are compared by heating experiments with the oscillating-heating x-ray powder diffraction method. In the course of expulsion of glycol from the 17A two-layer glycol complexes of the Mg-, Ca-, and Na-montmorillonites, a 14A one-layer complex is encountered which is substantially the same as the 14A one-layer vermiculite-glycol complex. One-dimensional Fourier methods are utilized for analysis of interlayer liquid distributions.