抄録
It is well known that the absorption of dye-stuff by the soil is always governed by the amout as well as the nature of colloidal part of the soil-Consequently, if the colloidal part is changed in its amount and also nature, the absorption of dye-stuff is expected to be changed in its degree and feature to an extent depending upon the nature of colloidal part. On this report the authors tried to trace the change of colloidal part, when heated in several degrees ; the change was being possibly expected to show the nature of colloidal part. Of three soils, different in their molecular ratios of alumina to silica (1-2<), the absorptive powers for dye stuff were determined by the use of photoelectric cell. More precisely written, the amount of dye-stuff absorbed by the soil was calculated from the transmittance-concentration courve (see Plate 1) obtained by the use of cobalt-coloured filter. The results were as shown in Table 3. From the results of Table 3,the following inclinations were observed. With the increase of heating temperature the absorptive power of the soils of higher ratio of SiO_2/Al_2O_3 (2<) decreased, while that of those of lower ratio increased. The above inclinations of quite opposite nature when compiled of the soils from genetic horizon of each soil type, are expected to become one of the suitable criteria for designation of each soil type. The following report of the same title will discuss the above designation.
