The essay serves as a proxy for the conceptual issue of treatment of confusio and commixtio in the Justinianean sources, particularly in the Institutiones, also posing a relationship between these ways of acquiring domain over things with others whith similar features, as are the accession between moveable things and creating a new object (nova specie facerem) and also review the traditional distinction that has been made between confusio and commixtio using as criteria the liquidity or solidity of the objects mixed.