From equation 16 one can determine the value of activity coefficient of  which
can lead to simultaneous removal of carbon and phosphorus.

Let us calculate the    when molten metal contains 2% C and 0.15% P and
temperature T=1773K. The mole fraction of in slag is 0.1.

(17)

  
        
We can calculate  and from equations 15 and 17. Substituting all the values
into equation 16 we get . We can also calculate  at temperatures 1673K and 1873K.
The results are given below

The calculations show:

• Both decarburization and dephosphorization are possible simultaneously in presence of slag in
  which   has extremely low value.
• Low temperature requires in slag to be higher than at high temperature.
  Thus low temperature is favourable.

References

• A. Ghosh and A. Chatterjee; Ironmaking and steelmaking
• R. Tupkary et.al. Modern methods of steelmaking
• A.K.Chakrabarti: Steelmaking