Free Alumina Research Articles

火成岩の風化に関する研究

(1) The author has studied on the weathering of biotite hornblende andesite found at Oh-ata-mura, Saihaku-gun, Tottori Prefecture. The fresh. rock, weathered rock, and light brown soil (B2 horizon) were used as material for the investigation. (Annual mean temperature…… 13.6°, annual rainfall…… 2200mm). (2) With the progress of the weathering, NIGGLI's values si, c, alk, and si/al decreased, . while al and h increased, k, m/c, f, and m slightly increased. In the weathering of this rock, the hornblende was not decomposed, however the plagioclase and the ground mass were decom-posed more rapidly than those in the pyroxene andesite previously reported. Al, Ca, and Mg in the rock partly remained in the undecomposed hornblende. (3) The light brown soil contained a small amount of free alumina (about 1%). In the weathered rock and soil, a large portion of the iron soluble in HCl was existent in the form of free iron oxide consisting of both limonitic (L) and hematitic oxide (H), and the ratio, of H/(H+L) increased in upper horizons. (4) The formation of weathering complex A1 and A2 from this rock began at an earlier stage of the weathering process. The complex A1 was allophane-like substance, and the complex A2 halloysitic, The kaolinite formation took place at a later stage of the weathering. The soil from this rock was rich in allitic allophane-like substance. On the contrary, the soils from the other igneous rocks in the same district were poor in allophane-like substance, and were siallitic. These facts show that the soil formation from the biotite hornblende andesite studied was highly influenced by the intrinsic factor. This character is important for classifying this soil. (5) In the light brown soil, the amount of exchangeable bases was very small, and the hydrolytic acidity was very high, though the exchange acidity was not so high, and the hydrolytic acidity was 32.4 times as great as the exchange acidity. (6) The clay separated from this andesite soil contained both allophane-like substance and halloysite.

THE HYDRATION OF THE ALUMINATES OF CALCIUM: V. THE HYDROTHERMAL DECOMPOSITION PRODUCTS OF TRICALCIUM ALUMINATE AT 350 °C.

When tricalcium aluminate is treated in saturated steam at 350 °C. hydrolysis occurs with the formation of a crystalline product of the composition 4CaO.3Al2O3.3H2O and calcium hydroxide. The same products result when a 3:1 mixture of calcium hydroxide and hydrated alumina are similarly treated. The calcium hydroxide as well as any hexahydrate of tricalcium aluminate formed at lower temperature may be removed from the hydrothermal product by extraction with a solution of acetic acid buffered with calcium acetate.The 4:3:3 calcium hydroaluminate crystallizes in colourless elongated rectangular plates with parallel extinction, positive elongation, and low birefrigence. The average refractive index is close to 1.627 and the density 2.71 (at 20 °C). The crystals are probably orthorhombic.Appreciable dehydration of the product does not occur on heating below 475° to 500 °C. Dehydration between 650° and 750 °C. in a stream of dry air appears to produce decomposition with the liberation of free alumina and probable formation of the product 12Ca0.7Al2O3.The factors affecting the yield of the 4:3:3 calcium hydroaluminate and the mechanism of the hydrothermal reactions of tricalcium aluminate and its hydrates are discussed. Readings of X-ray powder patterns of the 4:3:3 hydroaluminate and its dehydration products are given.

Procedure for Special Type of Mechanical and Mineralogical Soil Analysis

SummaryIn certain types of mechanical and mineralogical soil analysis, it is essential that the colloidal binding material consisting of organic matter, free iron and aluminum oxides, and colloidal silica be removed so as to get complete dispersion of the soil particles. The organic matter is commonly removed by means of hydrogen peroxide. Previously, the use of hydrogen sulfide had been suggested for removing the free iron oxide. Recently, it was found that the addition of oxalic acid to a soil suspension containing sodium sulfide, producing nascent hydrogen sulfide, is many times more effective than ordinary hydrogen sulfide for this purpose. With this improved procedure, it is possible to dissolve the free iron oxide in about ten minutes without greater acidification than pH 3.5. Free alumina is also dissolved. Boiling for a few minutes right after the addition of the sodium sulfide, which is quite alkaline, serves to dissolve colloidal silica. The amounts of these constituents dissolved are later added to the clay fraction. After this pretreatment and subsequent saturation with sodium, the soil is in ideal condition for mechanical and mineralogical analysis. Adoption of 2u as the upper limit of clay particle size is favored because clay thus separated consists largely of secondary minerals along with a few very resistant primary minerals like quartz and muscovite. Feldspars, the major group of primary minerals, are practically extinct below 2u. Separation at 5u does not allow this simple and desirable assumption. A centrifuge equipped with special centrifuge tubes, direct reading speedometer, and automatic time switch, and a special shaking machine are desirable equipment for making these analyses.

Free Alumina in Soils

IN the literature of soil science, the assumption is frequently made that, because a soil or product of rock weathering yields, when chemically analysed by acid digestion and fusion methods, a high proportion of alumina, it must therefore contain at least a part of its aluminous components in the uncombined state. That this is not necessarily the case has been indicated1 by the application of an alizarin adsorption method, devised by me, to a series of laterites, bauxites, kaolins, subsoils and surface soils, including some that are red in colour, collected mainly in the West Indies. The alizarin method depends on the fact (apparently first discovered in 1928 by Schmelev) that gibbsite (Al2O3.3H2O) and diaspore (Al2O3.H2O) after heating to temperatures around 800° C., but not before heating, develop the ability to adsorb in suitable circumstances appreciable quantities of alizarin. The amount adsorbed may be determined colorimetrically by extracting the stained washed material with acidified sodium oxalate solution.

Studies in Tropical Soils I. Identification and Approximate Estimation of Sesquioxide Components by Adsorption of Alizarin

1. An alizarin-adsorption method discovered by Schmelev has been successfully applied, with suitable modification, to the identification and approximate estimation of the free sesquioxide components of clays and soils.2. Details of the tested procedure are presented, together with some preliminary results obtained.3. The free alumina component of clays and soils appears to adsorb alizarin only after ignition, whereas the free iron oxide component adsorbs it only in the fresh, unignited state. Hence, by applying the procedure to the fresh, as well as to the ignited material, an approximate estimate of both components may be accomplished in a relatively short time.

X-RAY INVESTIGATION OF THE EFFECT OF HEAT ON CHINA CLAYS1

X-ray diffraction patterns were obtained from an English china clay and a Georgia sedimentary kaolin, both raw and fired to various temperatures. The chief crystalline constituent of the raw clays was found to be kaolinite. Upon dehydration the kaolinite lattice was destroyed and the clays gave no diffraction pattern. Mullite was formed in both clays at 950°C and the amount increased with increase of firing temperature. In addition to the mullite, free alumina was present in the Georgia clay from 950 to 1100°C and cristobalite at temperatures above 1200°C.

A STUDY OF THE HEATING AND COOLING CURVES OF JAPANESE KAOLINITE

ABSTRACTEffect of heating Japanese kaolinite at 100° to 1400° C for 3 to 4 hours.—Ignition loss of weight Was found to occur chiefly between 400° and 600°C, the rate of increase per degree reaching a maximum at about 460 °C. Changes of microstructure were observed at 600°, 900–1000°, 1250–1300° and at 1400 °C, when sillimanite began to develop.Heating and cooling curves for Japanese kaolinite, to 1400°C.—A differential method was used with quartz sand as the comparison substance. In addition to the known reactions: (1) an endothermic from 450° to 700°, and (2) an exothermic near 950°, (3) an exothermic change between 1200° and 1300° was discovered, and it was observed that the endothermic reaction seems to include two periods of heat absorption, (1a) 450° to 650° and (1b) 650° to 700°. In explanation, the author suggests that 1a is due to dehydration, 1b to dissociation of kaolinite into free alumina and free silica, 2 to a polymerization of the alumia and 3 to the formation of amorphous sillimanite. In the discussion, E. W. Washburn calls attention to the fact that the author has neglected the endothermic reaction of quartz at 575 °C and suggests that some of his conclusions are therefore erroneous.Heating and cooling curves for alumina obtained from the nitrate, hydroxide and sulfate by calcination are given in figure 6. Exothermic reactions which are ascribed by the author to polymerization of alumia occur at 800° to 900° and at 1100° to 1200° instead of at 950° and at 1250° as in the case of kaolinite.