抄録
A study was carried out on the assignment of infrared absorption at 1540 cm-1 of humic acid from a recent lake sediment. A relationship between absorbance of the 1540 cm-1 and nitrogen content, and chemical form of nitrogen in humic acid were examined. It was concluded that this band corresponds to the amide II of protein-like substances. Moreover, an example was given, showing a possibility of estimating proteinous nitrogen content of humic acid from lake sediments by the use of this band. It was suggested that, in the surface layer of lake bottom mud, all nitrogen in humic acid is present in proteinous form, on the other hand, in the deeper layer, proteinous nitrogen constitutes about 70% of the total nitrogen present in the humic acid.
