Rapid Dissolution of Allophane and Kaolinite-Halloysite After Dehydration

Isao Hashimoto1
1Department of Soils, University of Wisconsin, Madison, Wisconsin

Tóm tắt

AbstractDifferential dissolution in NaOH solution was investigated as a means of purification of clay. It was discovered that a large quantity of allophane and free alumina and silica were dissolved from clay preparations in 0.5 N NaOH solution by boiling for as little as 2.5 min, provided the ratio of clay weight to solution volume was kept less than 100 mg to 100 ml. Reprecipitation of dissolved silica occurred if a more prolonged digestion or higher sample to solution ratio was employed. Also, prolonged digestion in the NaOH solution (for 80 min) dissolved as much as 50 percent of kaolinite (Merck) and 25 percent of Wyoming montmorillonite, but only a small quantity of these crystalline minerals was dissolved during the 2.5 min digestion period. Subsequent dithionite-citrate-bicarbonate treatment removed the released iron. Marked improvement of x-ray diffraction patterns of the clays resulted. This rapid and selective dissolution of allophane and free oxides greatly improves the quantitative analysis of crystalline minerals by conventional methods.After dehydroxylation at 500°C, kaolinite and halloysite became amorphous and also dissolved by the same differential dissolution procedure. Heat-stable (aluminous) montmorillonite and chlorite were only slightly dissolved by this treatment. The selective removal of the 1 : 1 layer aluminosilicates greatly improves the quantitative analysis of the remaining crystalline components of clays by conventional methods.

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Tài liệu tham khảo

Jackson, 1956, Soil Chemical Analysis—Advanced Course, 991

Aomine, S. and Jackson, M. L. (1959) Soil allophane determination by cation-exchange delta value: Proc. Soil Sci. Soc. Amer. In press.

Pask, J. A. and Davies, B. (1945) Thermal analysis of clays and acid extraction of alumina from clays: U.S. Bur. Mines Tech. Paper 664, pp. 56–78.

10.1107/S0365110X5100177X

10.2136/sssaj1950.036159950014000C0017x

Jackson, 1958, Soil Chemical Analysis·, 498

10.3133/pp185G

10.1126/science.129.3363.1616

Brindley, 1951, X-ray Identification and Crystal Structures of Clay Minerals, 173

Steger, 1953, Quantitative chemical determination of muscovite in clays, Clay Min. Bull., 2, 23

Oda, 1954, x-Ray investigations on clays in Manchuria. IV. On the chemical composition of the iron chlorite in aluminous shales, J. Chem. Soc. Japan (pure chem. sect.), 75, 1320

Whittig, L. D. (1954) Crystalline and x-amorphous mineral weathering products in some soils of temperate and tropical origin: Ph.D. Thesis, University of Wisconsin, Madison, Wisconsin.

White, 1953, Allophanes from Lawrence County, Indiana, Amer. Min., 38, 634

Hislop, 1944, The decomposition of clay by heat, Trans. Brit. Geram. Soc., 43, 49

10.1346/CCMN.1958.0070122

10.1016/0016-7037(53)90003-9