The group contribution method proposed by Valderrama and Robles in 2007 and extended by Valderrama and Rojas in 2009 to estimate the critical properties of ionic liquids is revised and an additional test for determining the consistency of the estimated properties is proposed. The new testing method includes the calculation of the saturation pressure at the normal boiling temperature using an equation of state and an accurate model to represent the temperature function of the attractive term in the equation of state. In determining the vapor pressure, the critical temperature, the critical pressure, the critical volume, and the acentric factor determined by group contribution are included. The proposed method complements the previous density test of the authors that tested the critical temperature, the critical volume, and the normal boiling temperature only. A total of 1130 ionic liquids are considered in this work, and double checking, using the density and the normal vapor pressure, is applied. Also, a spreadsheet file that allows any reader to calculate and check the critical properties of other ionic liquids containing any of the 44 groups defined by the method is provided.

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The group contribution method proposed by Valderrama and Robles in 2007 and updated by Valderrama and coworkers in 2012 to estimate the critical properties of ionic liquids is extended to evaluate these properties for ionic liquids of higher molecular mass. The modifications are done to follow the behavior that these properties have for other type of substances, such as the asymptotic tendency of the normal boiling temperature as the molecular mass M increases. The magnitudes of the modifications are found so that the pressure test and the density test previously defined by the authors are fulfilled for most substances. The proposed extension does not change anything of the original method already in use which is valid for ILs with M < 500 g/mol. A total of 316 ionic liquids with M > 500 g/mol are considered in this work. Of these, 310 passed the pressure test. Also, 111 of these ILs have experimental density values and 103 pass the density test, with absolute average deviation of 4.1 %. A spreadsheet for calculating the critical properties and performing the tests is provided as Supporting Information. The spreadsheet file includes at present the properties for 1630 ionic liquids of molecular mass going from 77 to 1730.

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