Because of the leveling effect of common solvents, studies on super acids are conducted in more differentiating solvents that are very weakly basic such as sulfur dioxide (liquefied) and SO2ClF. Types of solvent on the basis of proton interaction On the basis of proton interaction, solvents are of four types, (i) Protophilic solvents: Solvents which have greater tendency to accept protons, i.e., water, alcohol, liquid ammonia, etc. (ii) Protogenic solvents: Solvents which have the tendency to produce protons, i.e., water, liquid hydrogen chloride, glacial acetic acid, etc. (iii) Amphiprotic solvents: Solvents which act both as protophilic or protogenic, e.g., water, ammonia, ethyl alcohol, etc. (iv) Aprotic solvents: Solvents which neither donate nor accept protons, e.g., benzene, carbon tetrachloride, carbon disulphide, etc. HCl acts as an acid in H2O, a stronger acid in NH3, a weak acid in CH3COOH, neutral in C6H6 and a weak base in HF. References Acid–base chemistry