The pyridinium-based ionic liquids have a promising prospect,since they exhibit high heat capacities,high thermal stability and low cost.The pyridinium-based ionic liquids have been used as cost effective and green absorbents for SO2 capture,solvents for many organic reactions,and extractants for aromatic heterocyclic sulfur compounds.In addition,the ILs with N(CN)2 anions are used as novel hypergolic materials,absorbents to capture CO2,and electrolytes to investigate the performance and the characteristic in dye-sensitized solar cells.In recent years,there has been a developing trend in the literature toward estimation of the physicochemical properties for compounds by semiempirical methods,in particular,for ILs.The estimated result provides valuable insight into the origins of the behavior of materials.Among all the empirical methods,parachor is the simplest.In order to expand the data of ionic parachor for ionic liquids,this paper reports the new experimental data of pyridinium-based ionic liquids,as the following:(1)Five dicyanamide ionic liquids [Cnpy][DCA](n = 2,3,4,5,6)were prepared and characterization;(2)In terms of the standard addition method(SAM),the values of density and surface tension for [Cnpy][DCA](n = 2,3,4,5,6)were measured at(298.15 ± 0.01)K.Firstly,ionic parachor was applied to the [Cnpy][DCA],[DCA]-was seen as a reference ion.Then,using data in literature and P+ of [Cnpy]+ and [Cnmim]+,the values of the anionic parachor [EtSO4]-,[NTf2]-were obtained,respectively,the result shows that the values of the anionic parachor [EtSO4]-and [NTf2]-are approximately equal.This implies that the value of ionic parachor obtained by the second extrathermodynamic assumption is more reasonable and reliable.According to the values of ionic parachor for [Cnpy][DCA],[Cnmim][DCA],[Cnmim][OAc] and [Cnmim][BF4],we can see that,for the different ionic liquids with 1:1 electrolyte,if the structure of cation or anion is the same,the value of cationic or anionic parachor is approximately equal.Secondly,according to the ionic parachor or parachor data of different ILs,we can see that the predicted values using the neutral contribution to parachor and the estimated values using the second extrathermodynamic assumption are little difference,but the estimated values are more closed to the experiment values.This implies that Coulomb force between ions can not be ignored.Finally,in order to verify the reliability of ionic parachors for [Cnpy]+ the parachor and surface tension of the investigated ionic liquids in literature were estimated.In comparison,the estimated values correlate quite well with their matching experimental values.