Premium
ACIDIC PROPERTIES OF PLANT LIGNINS AND HUMIC MATERIALS OF SOILS
Author(s) -
THOMPSON S. O.,
CHESTERS G.
Publication year - 1969
Publication title -
journal of soil science
Language(s) - English
Resource type - Journals
SCImago Journal Rank - 1.244
H-Index - 111
eISSN - 1365-2389
pISSN - 0022-4588
DOI - 10.1111/j.1365-2389.1969.tb01583.x
Subject(s) - chemistry , potentiometric titration , humic acid , titration , titration curve , aqueous solution , dimethylformamide , loam , soil water , inorganic chemistry , nuclear chemistry , organic chemistry , fertilizer , environmental science , ion , solvent , soil science
Summary The acidic properties of lignins from the native vegetation of a virgin Ella loamy sand and the humic acids, the 1, 4‐dioxane extractable humic fraction and residual humic acids from the virgin and cultivated soils were investigated by determining solid‐state cation exchange capacities for Cu and Ca and by non‐aqueous potentiometric titration, using potassium methoxide in a benzene‐methanol mixture as titrant. The lignins and soil dioxane extracts were titrated in pyridine; the humic acids in dimethylformamide. Platinized Pt and CH 3 OH modified calomel electrodes formed the electrode combination. The CEC of the humic acids were much higher than the CEC of lignins with both cations but the Cu: Ca absorption ratios were less for humic acids than for lignins. Titration curves of lignins showed two potential breaks with total acidities of 960 to 1,190 me/100 g. Titration curves of the humic acids showed three to six potential breaks while curves of the soil dioxane extracts showed three and four. The total acidities of the two types of humic isolates were 1,100‐1,200 me/100 g. The equivalent weights of most lignins and humic materials were very similar although the acid groups might be different with respect to types and acid strength. Lignins from other plant materials and humic isolates from other soils were also investigated by non‐aqueous titration to determine the general applicability of the results obtained with isolates from the Ella soils.