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Clay Mineral Content of the Colloidal Material Extracted from a Solodi Soil Profile
Author(s) -
Brown A. L.,
Caldwell A. C.
Publication year - 1947
Publication title -
soil science society of america journal
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 0.836
H-Index - 168
eISSN - 1435-0661
pISSN - 0361-5995
DOI - 10.2136/sssaj1947.036159950011000c0040x
Subject(s) - citation , library science , soil water , environmental science , soil science , computer science
T N a paper published recently (4), the authors re1 ported on the chemical composition of the colloids of some solodi soils of Minnesota. When this work was done, as an adjunct to it, X-ray analyses were made of the colloidal material extracted from one profile. These-data and related material are presented in this paper. Van Bemmelen (2), Schloesing (15), and others (6, 9, 13) have suggested the presence of many different substances in clay, but it is now generally accepted that the bulk of the colloidal material in soils 'is composed of clay minerals which are crystalline in character. These are secondary minerals which are formed by the weathering of igneous, metamorphic, and sedimentary rocks. Many clay minerals have been identified with the aid of X-ray, chemical, and other data, and three distinct groups have been recognized, viz., (a) kaolinite-halloysite, (b) montmorillonite beidellite, and (c) hydrous micas. The concepts of clay material have been discussed quite extensively by Grim (7), who describes the numerous clay minerals that have been identified by many workers and •discusses the structures, properties, and water relations of the minerals. The chemical composition of soil colloidal material, including the determination of exchangeable bases (6), has been studied by many investigators (i, 2, 3, 5). Published information on the mineral constitution of the fine clay fraction has shown that chemical methods alone do not give sufficient data for identification purposes. Silica-sesquioxide ratios and other . silica ratios have been shown by several workers (8, 10, ii) to be of limited use in identifying mineral components due to the possible presence of free oxides of iron, aluminum minerals, and free silica, as well as variations in the chemical composition of the clay minerals caused by isomorphous replacements. Hendricks and Alexander (8) a'nd Bray (3) have pointed out that the nonexchangeable potassium content indicates the presence of hydrous mica, as this mineral is the only one among the common minerals of the soil colloid which contains potassium. More than i% of nonexchangeable potassium indicates hydrous mica as a prominent constituent. Similarly, the same workers point out that nonexchangeable magnesium in excess of I %' indicates magnesium substituted clay minerals other than those of the kaolinite group.