1955 Volume 41 Issue 4 Pages 412-416
For studying the relation of the specific rate constant and the concentrations of carbon and oxygen in reactants, the rate of the carbon removal in molten Fe-C alloys containing about 4-0•2% carbon was measured by oxygen gas stream which had previously been prepared to have constant partial pressures of 20, 150, 300mm Hg respectively by mixing pure oxygen (or nitrogen) into air.
Then the specific rate constant K0 was estimated at a given concentration of carbon accor- ding to the process used in the preceeding reports.
If the reactants combined together to form the activated complex according to the following equation, the specific rate constant K0 might be given by the expression. where differcnt γ terms represented the activity coefficients of the reactants and the activated complex respectively. If the activity coefficient was defined with respect to the infinitely dilute solution as the standard state, k01 was the specific rate constant at the infinite dilute soluton of the reactants.
From the ratio of k0 to k01, which was obtained by extrapolating at the zero concentration of carbon, γoγc/γco =f term in the above equation was estimated.
Although the rate of the carbon removal increased with the carbon concentration at a given oxygen pressure, k0 increased with the diminution of carbon, in consequence of which it was found that f term was independent of the oxygen pressure at a given carbon concentration and increased with the diminution of the carbon concentration at the partial pressure between 20-300mm Hg.
These results might be considered to indicate that the activity coefficient of the reactants at the interface varied with the carbon concentrations on the existence of oxygen.
Nitrogen gas which existed together with oxygen gas had no influence on these terms.