Peculiar effects of alkali thiocyanates on the activity coefficients of aromatic hydrocarbons in water

Among twenty-two 1:1 electrolytes examined, LiSCN, CsSCN, KSCN and CsI have a considerable effect on the aqueous solubilities of a series of nonelectrolytes. LiSCN shows a salting-in effect for all the nonelectrolytes examined including 1-octanol, benzene, naphthalene and biphenyl while CsSCN and CsI show a salting-out effect for 1-octanol but a salting-in effect for all the aromatic hydrocarbons. The effect of NaSCN and KSCN on the solubilities of naphthalene and biphenyl results in an anomalous concentration depencence, i.e., both salting-in and salting-out effects occur depending upon the electrolyte concentration. It is suggested that the anomalous salt effects may partly be explained through perturbation of preexisting ion-ion structural hydration interaction upon introduction of the solute molecules.