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Chemical Extraction of Potassium from Soils and Micaceous Minerals With Solutions Containing Sodium Tetraphenylboron: II. Biotite¹

ABSTRACT

Biotite samples were treated with NaCl-NaBPh₄ solutions and various methods of separating the precipitated K from the resulting mixture were evaluated. As a result, a boiling NH₄Cl solution method was adopted for K extraction experiments with small samples and a foaming method was used in the preparation of a large sample of degraded biotite for mineral property studies.

Most of the K in biotite was easily extracted by placing the biotite in 1N NaCl-0.067N NaBPh₄ solutions that also contained EDTA. The rate of K removal, however, varied with the size of the particles. In the case of < 50µ biotite, K was removed at an average rate of 1.6 mg. per 100 g. per minute for 3 days. The K in vermiculite particles of the same size was removed even faster.

Na-degraded biotite that contained only 3.9 me. K per 100 g. had an expanding structure. With water and glycerol treatment, however, expansion was limited to about 5 Å. Air-dry, water-treated samples had a basal spacing of 12.3 Å. corresponding to 1 layer of water. The loss of this interlayer water resulted in an endothermic peak at 135° C. in the differential thermal curve of this sample.

¹ Journal Paper No. J-4054 of the Iowa Agr. and Home Econ. Exp. Sta., Ames. Project No. 1234.

² Professor and Research Associate in Soils, respectively.

Received for publication February 9, 1961. Accepted for publication March 13, 1961.