1. Bond, G. C., and Wells, P. B., Second Intern. Congr. Catalysis, Paper 55 (Paris, 1960).
2. Yates, J. T., and Garland, C. W., J. Phys. Chem., 65, 617 (1961).
3. Campbell, K. C., and Thomson, S. J., Trans. Farad. Soc., 55, 306 (1959); 57, 279 (1961).
4. Charman, H. B., Dell, R. M., and Teale, S. S., Trans. Farad. Soc. (in the press).
5. Charman, H. B., and Dell, R. M., Trans. Farad. Soc. (in the press).