Two suggestions as to the structure of sorbed water on clays have received considerable attention. Macey (1942), arguing from the similarity between the structure of ice and of the oxygen atoms exposed at a sheet surface, has suggested that the first layers of such water might have a structure similar to that of ice. Hendricks and Jefferson (1938), on the other hand, suggested the well-known “hexagonal-net” structure, a concept which was later extended to montmorillonite (Hendricks, Nelson and Alexander, 1940), and which has recently been used increasingly in the interpretation of the properties of clays (Grim and Cuthbert, 1945; Grim, 1942; Mering, 1946).

Some difficulties in the application of these theories to montmorillonite have already been pointed out by Williamson (1947-48), but some other aspects of the problem appear to merit further consideration. For example, there is an obvious space problem which is influenced by the position of the exchangeable cations and their frequency of distribution in the space available for water.

Clay mineral research was started at Wagingen in 1935 by Dr F. A. van Baren. Later Dr J. Ch. L. Favejee continued his work. Some papers were published on X-ray work, based on Dutch clays. The clay fractions of Dutch clays are mixtures of quartz, illite, kaolinite and montmorillonite in varying proportions. Favejee and Hardon analysed also a number of characteristic soil colloids from Java. The lateritic soils contain kaolinite; the very heavy black clays are montmorillonite, the terra-rossa soils on limestones contain (meta) halloysite; the same mineral was found in the (podzolic) mountain soils. In the true residual soils no mixtures of clay minerals were observed.

This work is part of a more general study of interactions between montmorillonite and organic substances, carried out in connection with the fundamental results of MacEwan and Mackenzie. The object of this work was the study of adsorption of acetone in the vapor phase.

Samples of sodium and calcium montmorillonites were placed in pyrex tubes provided each with a ground glass stopper and a tap. Each tube was joined to a vacuum pump through a desiccating column and heated for several hours to 280°C so as to desorb the water contained in the clay and on the glass walls. At the conclusion of the evacuation, the tube was opened while hot, so as to introduce a recipient containing acetone in solution in castor oil (which had been previously degassed in vacuum). The tube was again closed, re-evacuated, cooled, then isolated from the vacuum pump and put into a thermostat (40°C).

Activated clays may be used as catalysts for the polymerisation of vinyl aromatic substances such as styrene, α-methyl styrene or mixtures of these two compounds when in solution in an aromatic solvent.

Among the lithological types making up the northern Appennines, an important part is played by the (occasionally schistose) clays which make up the main bulk of an enormous nappe (“liguride,” according to Stille) which has slipped from the Ligurian region towards the Po valley. These clays are particularly well developed in the mid-mountain region, and can, because of their plasticity, insinuate into the more recent formations.

Within the argillaceous nappe, frequent nuclei of basic and ultrabasic rocks (gabbros, diabases, serpentines) are observed, of size ranging from that of a pebble to masses of many thousands of cubic meters (Monte Penna, Sasso Tignoso), which appear immersed in the clay mass without having produced in it the well-known contact phenomena.

The catalytic cracking process, which first came into prominence during the recent war, was one of the means adopted by the petroleum industry to meet the demand for aviation spirit of high quality to fuel the Allies' air forces. It was applied mainly in the United States and quantitatively made the largest contribution of any process. The process is a modification of the older thermal cracking process, the presence of the catalyst bringing about at a lower temperature the breakdown of large hydrocarbon molecules into smaller ones (some in the petrol boiling range) whilst at the same time promoting side reactions which improve the quality of the spirit.

Montmorillonites from various parts of the world have been tested. The main interest was focussed on the colloidal sections of the clay from which the heavy impurities were separated by dispersion and sedimentation. Use was made of the gold-shadow technique first described by Wyckoff to estimate the thickness of plates from the angle of shadowing.

While the writer was working on an unusual form of calcium carbonate usually found in caves, he collected some material closely resembling it from an adit of the disused Odin Lead Mine, Near Castleton, Derbyshire.

This material was pure white in colour, tending in places to translucency. It had a S.G. of 2.125 and a R.I. of about 1.5, though determination of the latter was rendered uncertain on account of included water. It took the from of a rippled flow covering the Carboniferous Limestone walls and roof of the passage. It was very soft, being obviously in the process of formation, though in places it had dried to form a slightly resistant encrustation.

This mineral is found in an ahnost pure state, forming a layer 1–2 m. thick at an average depth of about 50 m. beneath ground level, on the northern slope of the Monteti near to Capelbio (Orbetello, Tuscany). Above the layer of micaceous mineral there is developed a series of clays containing halloysite, metahalloysite, montmorillonite and kaolinite, locally rich in iron and manganese hydroxides. The series is quaternary, and lies on top of phyllites which have been attributed to the Permian. The whole series of clayey and ochreous minerals is of low-temperature hydrothermal origin, as I have shown in a recent communication (1948).

The yield of gasoline on distilling crude petroleum is of the order of 10 to 45 per cent., but in order to satisfy the enormous demand for motor fuel this yield may be increased by thermal treatment of heavy fractions such as gas oil at temperatures in the region of 500°C. Under these conditions, the oil is “cracked” or broken down to give gas, gasoline, and heavier fuels. Cracking increases the anti-knock value of gasoline as well as the yield.

Investigations of clay minerals are being actively pursued in the Fuel and Physics Departments of the University; while the investigations are being carried on independently of each other, a close liaison is maintained between the two laboratories and the special techniques developed in each are at the service of the other.

Clay minerals possess the peculiar characteristic that they normally occur as very small crystals. We cannot, therefore, afford to ignore the contribution that colloid science can make to the study of clay minerals. Many colloidal systems are stable because the particles are electrically charged. There is, of course, electrical neutrality of the system as a whole, but there is an electric separation within the system whereby electricity of one kind (it may be a positive or negative, depending on the system) is anchored for the time being to the particles while the complementary charge exists as ions (counter ions they are often called). Some of the counter ions must be regarded as in solution in the suspending medium (normally water) for it is their mobility relative to the particles which gives rise to electrical conductivity and to electrophoresis, electro-endosmosis and streaming potential.

I am going to speak about the results which we have obtained on nickel hydroxide gels. These experiments have been undertaken as a preliminary to the synthesis of certain clays; the intention is to study systematically the conditions of synthesis starting from hydroxides, while varying certain physico-chemical factors; especially the age of the gels.

As both attapulgite clays and some montmorillonite clays are termed “fuller's earths” in the literature, a comparison is made between the physical properties of the two groups of material, with special reference to those which are important commercially.

This work has so far been concerned mainly with montmonllonite. We have been attempting to study the behaviour of this mineral in contact with different reagents. It was with this general idea that Miss R. Glaeser took up the study of equilibria in the vapour phase with a series of organic substances. The first results are expected soon. The principal difficulty arises from the fact that it is necessary to operate in an anhydrous medium: as is well known it is difficult to eliminate all the water fixed by montmorillonite without partially altering the mineral.