The dropping mercury electrode (dme) is used to obtain very accurate current-potential measurements for the reduction of hydroxylamine as a function of temperature. The experimental set-up is fully computerized to obtain a large number of experimental points for proper statistical analysis of the results (100-150 points on each Tafel line). The Nemst slope for the reversible reduction of Cd* + and Tl+ is used as an internal standard to determine the overall reliability of the experimental setup. Agreement to within 0.&0.6% with theory is observed over the whole range of temperatures measured, from 1°C to 94°C. The Tafel lines for the reduction of hydroxylamine are found to be linear over 4 decades of current, showing that the transfer coefficient and the symmetry factor are strictly independent of potential (over 0.35-0.45 V). Tafel slopes are measured with a standard deviation of 0.4-1.0 mV and are found to follow the expected temperature dependence, with the transfer coefficient (and symmetry factor) independent of temperature.
This is the first reported case of a complex electrode reaction for which the transfer coefficient was measured with high accuracy (0.619+0.004) and found to be independent of temperature.