"Spot Test" techniques as applied to agronomic research Part. I. Detection of soil cations

Abstract

Two new and original microchemical techniques (Fernandes 1969, 1970) classified by the author as "Hopf chromatographic spot-tests” are presented for detection of cations in inorganic or organic-inorganic solutions. The techniques are based on different colored bands of Eriochrome black-T metal complexes, obtained by percolation of the solution on a strip of filter paper impregnated with the Erio-T reagent. The tests are very helpful for preliminary detection of magnesium, manganese, ferrous iron, aluminum and oxonium which have been displaced from a soil sample by means of a normal sodium chloride solution. Samples of different groups or soil entities provide distinct and specific chromatograms. One of the two tests is applicable and recommended for approximately quantitative determination of exchangeable magnesium. Some statistical aspects of the problem are presented.