Development of the Tetraphenylboron Method for the Determination of Extractable Soil Potassium1
- Allison C. Bennett and
- Robert M. Reed2
Many county and small commercial laboratories make quick tests on soil samples. These laboratories need a simple precise analytical procedure for extractable soil potassium. A turbidimetric method, using sodium tetraphenylboron, proposed by Sunderman and Sunderman was modified and further developed. Six Oklahoma soils were collected for this investigation. Sodium acetate and sodium nitrate at three concentrations (0.1, 0.5, and 3.0n) were used as extractants. Three extractant-soil ratios (5:1, 7:1 and 10:1) were also employed. The most suitable extractant was 0.1n sodium nitrate at an extractant-soil ratio of 5:1. Injection of sodium tetraphenylboron with a hypodermic syringe was the most satisfactory method. For maximum flocculation, there was a time-temperature interaction. Ammonium ion concentrations of 3 ppm or less were complexed by formaldehyde. Calcium and magnesium interferences were alleviated by EDTA.
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