This sixth-form chemistry activity describes how students can use acid-base titrimetry to investigate how adding salt to the aqueous phase may change the value of the partition coefficient of an organic acid between water and 2-methylpropan-1-ol. While the presence of lithium chloride and sodium chloride increases the value of the partition coefficient (the acid favouring the organic to the aqueous phase), the chlorides of potassium and caesium have the opposite effect. The activity provides a practical context for a full investigation and a discussion of the general principles of polarity, intermolecular forces and solubility.