Comparison of Case 3c and 7c with a previous formulation (but otherwise identical parameters) that excludes the ratio of molar masses from the volatile mass–partial pressure relationship (Eqs. (2) and (A.1)). (a) CO₂ volume mixing ratio, (b) abundance of CO₂ in the melt, (c) depletion fraction (%), which is relative to the initial amount of volatile that was partitioned into the interior according to the volatile mass balance.