In order to know the difference of properties among the ceramic clay materials from different localities, plastic clays from Seto, Tono, and Iga districts, were analized for pH (H₂0, KC₁) electric conductivity, CEC, and extractable cations. Reagents used for the extraction of cations were water, O. IN HCl, IN CH₃COONH₄ and IN KC1. The results obtained are summarized as follows:
I. The total amount of the soluble cations increased in the order of Seto-<Tono-<Iga-clay.
2. Seto-clay, one of the clays of best quality and of widest use for ceramic industries in Japan, contained high content of exchangeable and water soluble K ion as compared with Iga-and Tono-clay.
3. The clay having low pH (KC1) and a large exchange acidity (pH (H₂0)-pH (KC1)) showed poor dispersion and high viscosity in water.
4. Iga-clay was least in the amount of KC1-extractable Al, and highest in the amounts of KC1-extractable Fe and water-soluble organic matter, among the clay samples examined.
The observed differences of the clay samples from the different districts were discussed in relation to their genesis or the environment of deposition.