白浆土胡敏酸的电位滴定分析

POTENTIOMETRIC TITRATION STUDIES ON THE HUMIC ACIDS EXTRACTED FROM CULTIVATED ALBIC BLEACHED SOILS

对耕地白浆土等土壤中胡敏酸进行酸碱电位滴定分析结果,划分出弱酸基和极弱酸基两类酸性基团。它们的中和等当量点分别在 pH7.93±0.17和 pH10.08±0.10。胡敏酸中两类酸基的数量和其表观解离常数(pa),岗地白浆土与草甸土和暗棕壤相比较,没有明显的区别。

There are some differences in the contents and average dissocia- tion constant(PK~—a)of weakly acidic and very weakly acidic functional groups between the humic acids from albic bleached soils on terrace and alluvial plain. No significant differences are found belween cultivated albic bleached soils and dark brown forest soils,virgin meadow soils.The potentionmetric acid-base titrations of the humic acids reveal only two kinds of acid types:weakly acidic and very weakly acidic functional groups.Their neutralizing equilivalent points are at pH 7.93±0.17 and pH 10.08+0.10 separately.The PK~—a values are useful for the approach of chemical structure of the humic acids,but further studies are required.