How to store the volume that each ingredient takes in the medication?

We need to store the volume that each ingredient takes in the medication. For example, if the vial is 5mg/5ml and the amount added was 25 mg, then this ingredient would increase 25 ml in the total volume of the Medication. This additional volume can impact the calculation for the drug concentration in the solution. 

We have not found an element in Medication.ingredient to store this information. Our suggestion is to create a new element (Quantity) in Medication.ingredient called volume limited to the units of measure of liters and milliliters.