1. Numerous papers since 1935.
2. Privately communicated.
3. Médard, C. R., 197, 833 (1933); 199, 1615 (1934). Angus and Leckie, Nature, 134, 572 (1934); Proc. Roy. Soc., 149, 327 (1934). Briner and Susz, Helv. chim. Acta, 18, 378 (1935). Venkateswaran, Proc. Indian Acad. Sci., A, 4, 174 (1936).