1. Rydon, H. M., and Smith, P. W. G., Nature, 169, 922 (1952).
2. Reindel, F., and Hoppe, W., Chem. Ber., 87, 1103 (1954).
3. Smith, P. W. G., J. Chem. Soc., 3985 (1957).
4. “The Merck Index”, sixth ed., 226 (Merck and Co., Inc., 1952).
5. Cf. Greig, C. G., Leaback, D. H., and Walker, P. G., J. Chem. Soc. (in the press).