1. Feigl, F.: Chemistry of Specific, Selective and Sensitive Reactions, Academic Press, Inc., New York, 1949, p. 8.
2. Flagg, J. F.: Organic Reagents, Interscience Publishers, Inc., New York, 1948, p. 155.
3. Majumdar, A. K.: J. Indian chem. Soc. 19, 396 (1942); 21, 347 (1944).
4. Majumdar, A. K., and M. M. Chakrabartty: Z. analyt. Chem. 154, 262 (1957).