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The Weathering of Some Boron-Bearing Materials¹

ABSTRACT

The weathering properties of several boron-containing minerals and materials were studied for their solubilities and reactions in water and their exchange reactions in contact with clay.

The amounts of boron released from the minerals Howlite, Bakerite, Colemanite, Tourmaline, and boron frits, 176-E and 176-F, some commercial preparations, were investigated by treating these materials with distilled water at room temperature, hot distilled water as in a Soxlet extraction, hydrogen-saturated IR-120 amberlite, Putnam clay, and sodium EDTA. The bakerite and tourmaline minerals were studied for the availability of the mineral-held boron as demonstrated by growing alfalfa plants in sand-clay cultures that had received treatments of these minerals as a source of boron.

The amount of boron released was related to the nature of the mineral and to the type of weathering agent employed. The calcium borosilicates, Howlite and Bakerite, were weathered most highly by the weathering agents with high calcium-bonding energies such as amberlite IR-120 and EDTA. They were moderately weathered by hot water extraction, and weathered least by distilled water. The calcium borate, Colemanite, and the two boron frit compounds released the largest amount of boron when treated with the hydrogen-saturated IR-120. The Tourmaline released only traces of boron, regardless of the weathering treatments.

The plant root study of the availability of boron revealed the Bakerite mineral as an actively available source of boron, even such that it released excess amounts. The boron held in Tourmaline is unavailable to the plants.

¹ Contribution from Department of Soils, Missouri Agr. Exp. Sta., Journal Series No. 1706. Approved by Director. The interest and cooperation by the Pacific Coast Borax Co. in this study is sincerely appreciated. Presented before Div. II, Soil Science Society of America, Nov. 13, 1956 at Cincinnati, Ohio.

² Professor of Soils.

Received for publication January 22, 1957. Accepted for publication May 27, 1957.