A. D. Scott's research while affiliated with Iowa State University and other places

A mathematical expression that describes the release of interlayer K from mica particles in NaCl‐NaTPB solutions was derived. The mica particles were assumed to be circular discs and the rate determining process for the release of K was considered to be the simultaneous diffusion of K and Na within the particle. Therefore, this derivation involved the solution of a two‐dimensional radial diffusion problem in which K diffuses from a receding weathering front to the periphery of the particle. The validity of these assumptions and the resulting expression was evaluated with experimentally determined K release data. The experimental data were obtained with different size fractions of biotite and muscovite placed in NaCl‐NaTPB solutions for different periods of time. The results obtained with each size fraction were accurately described by the theoretical expression. In the case of a 50 to 62 µ biotite fraction, this was true even though 90% of the K was released in a period of 113 hours. On the other hand, the expression did not account for the effect of particle size. A modification of the expression, based on the experimental results, however, accounted for the effects of both time and particle size.

Flame photometric methods for determining potassium precipitated as potassium tetraphenylborate in aqueous systems are described. In one method acetone-water solutions of the potassium tetraphenylborate are used directly. In the others, the potassium is converted to a water-soluble form by heating the tetraphenylborate salt for 20 minutes in a furnace at 350° C. or in boiling aqueous solutions of mercuric chloride. The application of these methods to the determination of potassium extracted from soils or micaceous minerals by aqueous sodium tetraphenylborate solutions is also discussed. With these methods, this potassium can be separated from the mineral residues and determined quantitatively without interference from excess sodium tetraphenylborate, decomposition products of the tetraphenylborate, or other materials in soils and micaceous minerals that are soluble in acetone or water.