Two sulfonate-containing zwitterions, 1-methylimidazolium-3-propylsulfonate zwitterion (MimC(3)SO(3), C(7)H(12)N(2)O(3)S; CAS 179863-07-1) and 1-methylimidazolium-3-butylsulfonate zwitterion (MimC(4)SO(3); C(8)N(14)O(3)S; CAS 148019-49-2), were prepared, and the structures were characterized by (1)H NMR and (13)C NMR and ESI-MS. The thermodynamic properties are investigated through adiabatic caloremetry (AC). differential scanning calorimetry (DSC). and thermogravimetric (TG) analysis. The low-temperature heat capacity (C(p,m)) of MimC(3)SO(3) and MimC(4)SO(3) was measured in the temperature range from (78 to 400) K with a high precision automated calorimeter. The thermodynamic functions [H(T) - H(298.15)] and [S(T) - S(298.15)] were calculated based on the heal capacity data in the range from (80 to 400) K with an interval of 5 K.