1. N. Hedley and H. Tabachnik,Internat. Tech. Bull. 31 Wayne, New Jersey (1968).
2. E. M. Wise, ?Gole, Recovery, Properties and Application?, D. Van Nostrand Co., New Jersey (1965).
3. F. Habashi,J. Chem. Education 42 (1965) 318.
4. T. P. Pan and C. C. Wan, to be published inJ. Electrochem.
5. K. J. Cathro and D. F. A. Koch,J. Electrochem. Soc. 111 (1964) 1416.