腐植酸の形成に関する物理化学的研究(第5報) : 腐植酸の吸収スペクトル

抄録

The author studied absorption spectra of natural and artificial hnmic acid solutions. The results were summarized as follws : l. The intensity of light absorption of humic acid dissolved in dilute alkaline solution decreased gradually with the lapse of time at all waves, especially remarkably at long waves. But in ultra-violet region, the absorption intensity tended to increase again after about 50 days. In the case of soil humic acids, the decrease of light absorption became greater with the lowering of humification. Artificial humic acids were very unstable compared with natural soil humic acids (Table l). 2. The absorption curves of the soil humic acids hardly changed their shapes after the acids was reprecipitated 5 to 7 times, but the curves of artificial humic acids showed an inclination of getting steep shape after the reprecipitation. This inclination was probably due to the partial decomposition or denaturation of the acids (Table 2). 3. No visible bands were found in the absorption spectra of humic acids in the visible region except in those from podsol and diluvial soil (Fig. 1 and 2). The humic acids from these soils showed absorption bands clearly at about 620 mμ and somewhat indistinctly at about 570 and 470mμ. 4. Absorption curves of humic acids were very similar in their shapes at the waves, from 200 to 2,OOOmμ having a lowest part at about 1,100mμ, and turning upward from this wavelength (Fig. 3).