“…Speed of sound for various ILs vs molar mass of anions at 298.15 K; blue open circles, [C 2 C 1 im] + ; red open squares, [C 4 C 1 im] + ; green open diamonds, [C 6 C 1 im] + ; magenta open triangles, [C 8 C 1 im] + ; black filled circles, [C 4 C 1 pyr] + ; stars, [C 4 -3-C 1 py] + ) [C 2 C 1 im][NTf 2 ], ,, [C 2 C 1 im][TFO], , [C 2 C 1 im][C 2 SO 4 ], ,, [C 2 C 1 im][Ac], [C 2 C 1 im][C 1 SO 4 ], ,,, [C 2 C 1 im][BF 4 ], − [C 2 C 1 im][Cl]; , [C 4 C 1 im][NTf 2 ], ,,, [C 4 C 1 im][C 8 SO 4 ], [C 4 C 1 im][TFO], ,,, [C 4 C 1 im][PF 6 ], ,,,,,− [C 4 C 1 im][Asp], [C 4 C 1 im][Ac], [C 4 C 1 im][C 1 SO 4 ], ,, [C 4 C 1 im][BF 4 ], ,,,, [C 4 C 1 im][N(CN) 2 ], , [C 4 C 1 im][Cl], ,, [C 6 C 1 im][NTf 2 ], ,,, [C 6 C 1 im][BF 4 ], , [C 6 C 1 im][Br], , [C 6 C 1 im][N(CN) 2 ], [C 8 C 1 im][NTf 2 ], [C 8 C 1 im][PF 6 ], ,, [C 8 C 1 im][BF 4 ], , [C 8 C 1 im][Cl], , [C 4 C 1 pyr][NTf 2 ],…”