Abstract
In order to study the chemical properties of clay pots, constant-boiling hydrochloric acid-, water- and ammonium acetic acid extractable minerals were determined.
1. Among the minerals extracted by constant-boiling hydrochloric acid, Al2O3 and Fe2O3 were comparatively high, whereas SiO2 was very low in each sample notwithstanding its high contents in the raw material. Two samples of Tokyo (A and B) had the highest contents in each extractable mineral, but that of Kitaibaraki (D), the lowest.
2. Water-extractable K2O, Na2O, CaO and MgO were relatively high, whereas the other elements such as SiO2, Al2O3, Fe2O3 and P2O5 were very low. Two samples of Tokyo (A and B) had the highest quantity of each water-extractable mineral, while samples of Kitaibaraki (D) and three districts of Aichi pref. (E, F and G) had much less in water-extractable CaO and MgO. Increased extraction of these minerals was found with the increment of water ratio to pot materials from 2: 1 to 20: 1, especially between 10:1 and 20:1.
After the first extraction by water at the ratio of 10:1, the second extraction was done at the same ratio. These secondary water-extractable minerals were considerably less than the first one except P2O5. Contents of K2O and Na2O dropped to about 60-20% of the first extract, while those of CaO and MgO decreased more remarkably.
3. The contents of NH4OAc-extractable K2O, CaO and MgO were more than those of water-extractable ones, except Na2O. These exchangeable cations of samples of Tokyo (A and B) were considerably higher than those of the other districts, as in the case of the constant-boiling hydrochloric acid- and the water-extractable ones.
4. The results obtained in this experiment suggest that minerals which can be absorbed by plant roots are K2O, Na2O, CaO and MgO, but the extractable quantities of these minerals from clay pots seem to vary considerably with chemical compositions of raw materials the firing temperatures and so on.
