In a recent publication¹ Elliott, Lynch and Brown (ELB) have criticized the early Flood and Grjotheim (FG) treatment² of slag-metal equilibria. The present paper demonstrates that part of the difference between the ELB and FG treatment is in the different choice of standard state. However, the standard state used by ELB was introduced in 1959³ for the treatment of this type of equilibria. A fundamental thermodynamic error is introduced in the ELB derivation by the use of single ion activity coefficients which invalidates their treatment of experimental data.