On the Activities of Coexisting Elements in Molten Iron. III : The Activity of Mn in Molten Fe-Mn Alloy

By constructing the following electrode concentration cell and with a potentiometer, the authors measured the e. m. f. corresponding to the change in the Mn content in iron. ⊕ Fe-Mn |SiO_2-MnO-CaO-MgO|Mn ⊖ The temperature of the experiment was about 1, 590±5℃ and for the measurement of temperature, a Pt-Pt/Rh thermocouple was used. The theoretical relation between the e. m. f., E(V) and the activity of Mn, a_ was as follows : E = RT/nF×In a^i_/^a_ -RT/nF×In a^i_/a\u27_ (1) where a^i_= the activity of Mn ion in the molten slag a\u27_= the activity of pure Mn When pure Mn was selected so as to be in a standard state, the following equation was obtained from eq. (I) : E ≒ -0.0002T/n × log a_ (2) n was approximately determined as n = 2 by a calculation from the authors data. From eq. (2) the activities of Mn were determined all over the range. From the authors result, FeMn binary solution was recognized to be an approximately ideal solution all over the range. Judging from consideration made from several points of view, Fe-Ni and Fe-Co binary solutions were also considered to follow the Raoult\u27s law as in the case of Fe-Mn binary solution