Tiron Dissolution Method Used to Remove and Characterize Inorganic Components in Soils

Treatments using NaOH and Na 2 CO 3 have been widely used to remove poorly crystalline and noncrystalline aluminosilicates and hydrous oxides of Si and Al. However, NaOH treatment is often too harsh and Na 2 CO 3 treatment is usually too mild and must be repeated. Treatment using alkaline Tiron (4,5‐dihydroxy‐1,3‐benzene‐disulfonic acid [disodium salt], C 6 H 4 Na 2 O 8 S 2 ) was as effective as acid oxalate in the dissolution of allophane, imogolite, and poorly crystalline hydrous Fe oxides. In contrast to oxalate, Tiron effectively removed opaline silica, and the difference between extracted Si could be used to measure the amount of opaline silica. Unlike oxalate, Tiron dissolved little magnetite. As gibbsite is partially dissolved by Tiron, the rates of Al release by gibbsite (<2 µm) dissolution at different temperatures were used to estimate the gibbsite contents of soil clays containing this mineral. Generally, a single treatment with Tiron appears to be sufficient to mildly but effectively clean up samples for x‐ray diffraction of crystalline minerals with amounts of extracted Si, Al, and Fe indicating the presence and quantities of poorly crystalline and noncrystalline aluminosilicates as well as hydrous oxides of Fe, Al, and Si, including opaline silica.