1. Powers, H. E. C., Nature, 178, 139 (1956).
2. Hill, S., and Dobbs, A. G. R., Analyst, 83, 143; also Gardiner, S. D., and Keyte, H. J., ibid., 150.
3. Carruthers, A., Oldfield, J. F. T., Shore, M., and Wootton, A. E., “Studies in the Chemistry of Sulphitation”, 10th Tech. Con. British Sugar Corporation (1957).