Showing papers on "Vermiculite published in 1969"

Weathering of Mica by Fungi1

Abstract: Three trioctahedral micas and one dioctahedral mica size fractions) were used as sources of K for seven fungi grown in nutrient solution buffered at pH 6. Vermiculite formed from the mica. The mechanism involved was exchange of solution Na for mica K, with the fungi functioning as K-sinks. Reducing the concentration of solution Na from 0.054M to 0.017M resulted in decreased rate of utilization of mica K. Growth of fungi and release of K were greater for trioctahedral micas than for the dioctahedral mica and generally followed the K ease-of-release pattern established using sodium tetraphenylboron and NaCl solutions. The fungi differed in their capacities to promote the mica-to-vermiculite transition, and this was probably due mainly to their relative effectiveness as K-sinks. Additional

Chemical composition of soil vermiculite clays as related to their genesis

Abstract: Chemical and mineralogical analyses of the clay fraction of eleven soils containing a large amount of vermiculite clay and representing a wide range of parent materials revealed that two types of vermiculite clays exist: (1) An aluminous type in which Al3+ substitutes for Si4+ in tetrahedral positions in the same order of magnitude as in the coarse grained vermiculites and micas, and with Al3+ as the dominant octahedral ion. (2) A silicious type in which only Si4+ occupies the tetrahedral positions, and with Fe3+ and Mg2+ as the dominant octahedral ions. The aluminous vermiculite clay was found to occur in soils derived from acid igneous rocks and is usally associated with mica, whereas the silicious type was found to occur in soils derived from basic igneous rocks which do not contain mica. Because of this close association of these two types to their parent material, it was concluded that the aluminous vermiculite is a product of alteration of mica whereas the silicious type is a product of synthesis from primary oxides of silica, alumina, iron, and magnesium. Both types of vermiculite clays tend to be dioctahedral in contrast to the trioctahedral nature of the coarse-grained vermiculite.

Surface area of vermiculite with nitrogen and carbon dioxide as adsorbates

Abstract: Surface-area studies were made on several homoionic vermiculites with both nitrogen and carbon dioxide as adsorbates. These studies show that only very slight penetration occurs between individual vermiculite platelets. This is in contrast to an earlier investigation of montmorillonite where it was found that the degree of penetration between layers is quite high, particularly for carbon dioxide, and is governed by the size and charge of the interlayer cation. The inability of these adsorbates to penetrate substantially between vermiculite platelets is due primarily to this mineral’s high surface-charge density.

Delayed Exchange of Potassium from some Edges of Mica Flakes

Abstract: WHEN micas weather in the soil, their interlayer potassium is replaced by a hydrated cation, and a swelling mineral resembling vermiculite is formed1. Although this natural process may be simulated in the laboratory2,3,9, we have found evidence to suggest that micas may alter less rapidly in natural conditions than laboratory investigations of ground or cut material suggest. Our results show that the nature of the crystal edge affects the rate of alteration of micas.

Effects of pretreatment on a 14 Å swelling mineral from Gartly, Aberdeenshire

Abstract: A 14 A swelling mineral, interlayered with what is probably an organo- metallic complex, occurs in the surface horizon of a gleyed soil near Gartly, Aberdeen- shire. The interlayer material is thermally stable at 300 r C and is easily removed by oxidation with H202 and NaOC1. Treatment with HC1 and Na2EDTA destroys the ability of the mineral to expand with glycerol, although not if the clay is H202 treated beforehand. The Gartly clay mineral is also unusual in that Mg-saturation, using magnesium acetate at pH 7, leads to the rapid formation of brucite-like interlayers. It is concluded that in the investigation of soil clays it is best to avoid all pretreatments. The positive identification of the 14 A minerals commonly found in soil clays has long been a subject of study. In general, montmorillonite and vermiculite may be distinguished by observing the effect of a polar organic liquid such as glycerol on the X-ray diffraction pattern, although under certain circumstances presaturation with Mg 2+ may be necessary to distinguish between vermiculites and montmoril- lonites with similar swelling characteristics (Walker, 1958). Chlorite may be differentiated from vermiculite by observing the response of the 14 A reflection after heating at 300 ~ C; at this temperature the chlorite structure remains stable whilst vermiculite collapses to 10 A, although precautions against rehydration during cooling must be taken. If interlayer contaminants are present this structural contraction is impeded and usually spacings intermediate between 10 and 14 A are recorded. Swelling chlorite may be detected by a combination of glycerol and heat treatment. However, some soil clays, such as those described by Beutelspacher & Fiedler (1964), are not amenable to standard diagnostic procedures. These clays yielded a broad diffraction band between 10 and 14 A which varied in position and intensity according to various pretreatments, thereby precluding unequivocal identification. The writers encountered similar difficulties during an investigation on some Aberdeenshire soil clays. It was found that several commonly used pretreatments affected the dominant 14 A mineral to such an extent that a positive identification was rendered * Present Address: Centro de Edafologia y Biologia Vegetal, Cortijo de Cuarto, Seville. Spain.

A naturally occurring sodium vermiculite from unst, shetland

Abstract: A naturally occurring macroscopic sodium vermiculite from Unst, Shetland is described. It is similar in many respects to synthetic materials recently pre- pared from phlogopite by potassium replacement. In other respects, however, it is more akin to macroscopic Mg-vermiculites.

THE EQUILIBRIA OF K:Al EXCHANGE IN CLAY MINERALS AND ACID SOILS1

Abstract: Summary Conventional K: Al exchange isotherms for montmorillonite showed that Al3+ was strongly preferred to K+ in o-oin solutions. The exchange coefficient, K', calculated using the isotopically exchangeable K, was greater than unity and did not vary with the Al-saturation or with the initial pH of the AlCl3 solutions. Isotherms for vermiculite, illite, and soils in o·oin solutions also showed Al3+-preference but unlike those for montmorillonite were not asymptotic to qAl/qo= 1, qAl being the amount of adsorbed Al and qo the total adsorbed (Al + K), indicating that some of the isotopically exchangeable K could not easily be exchanged by Al3+ ions; this difficultly exchangeable K (DEK) was estimated for each exchanger. K' values for vermiculite, illite, and soils were less than unity and did not vary with Al-saturation or initial pH if the isotopically exchangeable K was corrected for DEK. This showed that K+ was adsorbed more strongly than Al3+. Strengths of K+ adsorption referred to Al3+ as the counter-cation were in order: soils > vermiculite, illite > montmorillonite.

Electron Microprobe Analysis of Thin Sections of Soil to Observe Loci of Cation Exchange1

Abstract: To observe the loci of cation exchange in natural soils, (16 cm³) cubes of soil with such micromorphological features as silt and clay varves, isolated clay bodies in a silty matrix, and clay and silt skins on ped surfaces, were leached repeatedly with CsCl. After the soil cubes were saturated with Cs, they were dried and impregnated with a polyester resin. X-ray images and Cs activity measurements, determined on thin sections with the electron microprobe, demonstrated that Cs sorbed by microstructures enriched with clay was nearly twice that of silty matrices. These observations illustrate that the loci of cation exchange are heterogeneously distributed within the undisturbed soil horizon and are influenced by micromorphological features produced by geologic and pedogenic processes. Cesium sorbed by weathered biotite sand grains was eight times greater than by clay bodies. The greater exchange capacity of the weathered biotite was attributed to the loss of interlayer potassium and conversion to a vermiculite-like mineral. The smaller exchange capacity of the clay was attributed to the presence of illite, chlorite, and kaolinite, of low exchange capacity, to pedogenic weathering and aluminum interlayer formation in vermiculite and to the presence of 40 to 50% pore space. Although weathered biotite sand grains constituted only 1.6% of the whole soil, they contributed about 15% to the total exchange capacity of Charlton soil.

Heat-resistant sealing compositions containing

Abstract: Heat-resistant sealing compounds for use in mines consisting of a cement binder, expanded vermiculite, a filler, a substance to prevent contraction during water absorption and substance to improve the rheology of the wet mix. The mixture in powder form is mixed with water and sprayed into position. Good weathering properties; easily applicable; fire-proof. Vermiculite particle size less than 0.9 cm; filler usually CaCO3 of less than 150 B.S.S. mesh; substance to prevent contraction a metal oxide, Ca sulphoaluminate or anhydrite rheology improver methyl cellulose etc and/or sulphite waste liquor. The compsn. can also contain a polyvinyl ester.

Fire Proof Building Board

Abstract: 1,158,460. Timber substitutes. W. R. GRACE & Co. 20 June, 1967 [1 July, 1966], No. 28465/67. Headings C3C, C3N and C3R. A building board comprises a blend of wood particles, unexpanded, expandable mineral ore, e.g. vermiculite or perlite, and a binder, and integral therewith on at least one side a layer or layers of compressed exfoliated vermiculite or unexpanded vermiculite ore. There may be a second layer, integral with the first, of exfoliated vermiculite. The board may be made by spreading in the bottom half of a press: (a) a mixture of exfoliated vermiculate and synthetic resin; and on this layer spreading (b) a mattress of wood chips, unexpanded vermiculite, and synthetic resin binder; and on this layer a futher layer of (a), and hot-pressing. The assembly may be cold-pressed before hot-pressing. The wood particles may be chips, flakes, shavings, splinters, or sawdust. The wood may have moisture content 7A2%. In (b) there may be 10-80 wt. per cent vermiculite based on wood. The binder may be ureaformaldehyde, phenol-formaldehyde, or melamine-formaldehyde. Paraffin-based wax emulsions may also be added. In a contrasting example (b) contains no vermiculite.

Reactions of Some Clays with Ferric-Ferricyanide (Prussian Brown)

Abstract: The intensification of the auto-reduction of Prussian Brown by clay minerals was studied. The reaction is catalyzed mainly by the expanding clay minerals montmorillonite and vermiculite, but is inhibited by aluminium oxide and allophane, although these also sorb Prussian Brown. The influence of surface acidity and exchangeable cation on the reaction is discussed.