1. Department of Applied Chemistry, Waseda University, Okubo, Shinjuku‐ku, Tokyo 169, Japan
2. Nihon Parkerizing Company, Limited, Central Research Laboratories, Ohgami, Hiratsuka‐shi, Kanagawa 254, Japan
3. Oki Electric Industry Company, Limited, Research Laboratories, Higashi asakawa‐cho, Hachioji‐shi, Tokyo 193, Japan