The viscosity of room temperature ionic liquid + molecular solvents is correlated using the Jouyban−Acree model, and the accuracy of the model is evaluated using average relative deviations (ARD) of the calculated and experimental values. The overall ARD of 6.9 % was obtained for the proposed model where the overall ARD for a similar model from the literature was 22.4 %. The mean difference between ARDs of the models was statistically significant. Combined forms of the Jouyban−Acree model and the Abraham parameters were used for predicting the viscosity of the mixtures at various temperatures. The overall ARD for the investigated mixtures was 15.0 % when the experimental viscosity of the pure solvents was included. The ARD of the in silico version of the model was 20.7 %. ■ INTRODUCTIONRoom temperature ionic liquids (RTILs) are a new class of solvents attracting considerable attention in the pharmaceutical/ chemical industries. RTILs are used in manufacturing nanomaterials, high temperature lubricants, excipients for new drug delivery systems, novel stationary phases for gas chromatographic systems, and extraction solvents for separation of analytes. Very low vapor pressure, multiple solvation interactions with organic and inorganic compounds, very good chemical and thermal stability, high ionic conductivity, and wide melting point temperature ranges are the main advantages of RTILs over common molecular solvents. In addition to the applications of RTILs, their mixtures with molecular solvents are used in the industry providing wider physicochemical properties. Viscosity data of the mixtures are required in some related computations and a number of attempts have been made to collect the experimental values of the viscosity and density of these mixtures.1−23 Despite these experimental efforts, a number of mathematical models were proposed to compute the properties. The aims of this work are to propose a mathematical model to fit the viscosity data of RTILs + solvent mixtures at various temperatures and also provide global versions of the model to predict the viscosity data.

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The solubility of tris(hydroxymethyl)-aminomethane (TRIS) in various mass fractions of water + methanol solvent mixtures at (293.2, 298.2, 303.2, 308.2, and 313.2) K was measured using a laser monitoring technique. The generated data were mathematically represented using the Jouyban−Acree model. The back-calculated mole fraction solubilities are in good agreement with the corresponding experimental values as documented by an overall mean percentage deviation of 3.2 %. ■ INTRODUCTIONSolubility data enable researchers to select the most appropriate solvent system for solubilization or crystallization of a solute. Mixed solvents provide "tunable polarity solvents" to alter the solubility of a given solute. These mixtures are also used as mobile phases and/or solvents for the background electrolytes in analytical separation methods such as high-performance liquid chromatography (HPLC) or capillary electrophoresis (CE) where the low solubility of electrolytes at higher concentrations of the organic solvent might be a limiting parameter. Mixed solvents applied in this context may improve the solubility of the analyte, the resolution of the peaks of various analytes, or determine other relevant analytical parameters like pK a values, partition coefficients, or electrophoretic and electroosmotic mobilities. A quick survey on the published HPLC and CE methods for pharmaceutical analysis showed that TRIS buffer has been used primarily in the following binary solvent systems. The most frequently used mixed solvents are water + acetonitrile (55 %), followed by water + methanol (36 %), water + ethanol (4 %), methanol + acetonitrile (3 %), and water + 1-propanol (2 %). 12Because of this high practical importance, it was our intention to measure the solubility of TRIS in binary aqueous mixtures of methanol at different temperatures for validating a lab-made setup and to extend the available database of solubilities. 13 To enable the calculation of the solubility of TRIS at any composition of the binary solvent mixture and temperatures, we fitted the data to the Jouyban−Acree model and its combined version with the van't Hoff equation.

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