Abstract: The distribution coefficients of n-propionic acid and n-butyric acid have been determined in the benzene phase in equilibrium with the water as well as the aqueous salt solution phases,thus enabling us to get the activity coefficient of each of the acids.The salts used are LiCl,NaCl,KCl,SrCl₂,BaCl₂,LiBr,NaBr,and KBr.Following the Randall and Failley's treatment of the weak acid,we have calculated the concentrations of its ions and obtained the concentration and finally the activity coefficient of the undissociated part of the acid fuThe salt concentrations Cs used are 0→1 mol e/1.When we plot log fu vs.C_sfor the salts,the results obtained are all straight lines.On comparison of the slopes of these lines,the salting-out order is SrCl₂> BaCl₂>LiCl≈NaCl>LiBr≈NaBr>KCl>KBr for propionic acid,and is SrCl₂>BaCl₂>NaCl≈LiCl>NaBr≈KCl≈LiBr>KBr for butyric acid.We have calculated the salting-out constants of these acids in the solutions of alkaline and alkaline-earth halides by the formula of (1) Debye-McAulay,(2) McDevit-Long,and (3) Conway-Desnoyes-Smith.With the exception of the lithium salts,they all give the right salting order of the salts,but formula (3) gives the results in better agreement with the experiment than those of (1) and (2).