Amendments to the Determination of “Uronic Acids” in Soils With Carbazole
1962
Dormaar, J. F. | Lynch, D. L.
The release of soil “uronic acids” from four soil profiles was determined using 0.5N NaOH extracting solutions at 22° and 70°C, with an intermediate treatment using N HF-HCl. The amounts of “uronic acids” released by alkali extractions were compared with the amounts released by either an HCl or H₂SO₄ hydrolyses of these soils. An exchange resin Amberlite IR-120 (hydrogen form) and other means were investigated as to their efficiency in removing excessive amounts of iron from these soil solutions. A comparison of recoveries of pure galacturonic acid after hydrolysis with HCl and H₂SO₄ solutions was also made. Both the extraction and the hydrolytic procedures released large amounts of soil “uronic acids” from the four soils. However, in terms of time and simplicity the hydrolytic methods are to be preferred. Iron was most effectively removed from these soil solutions by an ion-exchange resin (Amberlite IR-120). A more rapid rate of decarboxylation of pure galacturonic acid occurred with HCl hydrolyses than similar hydrolyses with equivalent solutions of H₂SO₄. The content of “uronic acids” ranged from 1.2 to 3.9% of the organic matter in the four soil profiles.
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