“…This is not the first observation on the beneficial effects of tin in the reaction medium. Previous investigators (1,8,4,6,8,11,12,18,19,21,86,40,50,55) have shown that the presence of tin in various reaction media contributed to the more efficient and reproducible extraction of the oxygen content as well. The role played by the tin is not clear although a number of desirable functions have been attributed to it (12).…”