Organic liquids, miscibility numbers

Two nonpolar organic liquids, hexane (QH,4) and heptane (CyHig), are mixed, (a) Do you expect A/4,i to be a large positive number, a large negative number, or close to zero Explain, (b) Hexane and heptane are miscible with each other in aU proportions. In making a solution of them, is the entropy of the system increased, decreased, or close to zero, compared to the separate pure liquids ... 

While it is possible to use a number of volatile solvents as the mobile phase for SCF chromatography, the most commonly used mobile phase is carbon dioxide. However, carbon dioxide is not a good solvent for polar compounds so it is common to add a small amount of some additional polar organic liquid such as an alcohol or even water as a modifier. However, the modifier needs to be miscible with carbon dioxide. Much of the other technology associated with either GC or HPLC in terms of sample inlets and types of pumps are adapted to specific applications but the key attribute of the SCF-type chromatography is the maintenance of T, P) conditions near the critical point of the mobile phase. A selection of columns is available just as for GC or HPLC. 

Liquid sulfur dioxide expands by ca 10% when warmed from 20 to 60°C under pressure. Pure liquid sulfur dioxide is a poor conductor of electricity, but high conductivity solutions of some salts in sulfur dioxide can be made (216). Liquid sulfur dioxide is only slightly miscible with water. The gas is soluble to the extent of 36 volumes pet volume of water at 20°C, but it is very soluble (several hundred volumes per volume of solvent) in a number of organic solvents, eg, acetone, other ketones, and formic acid. Sulfur dioxide is less soluble in nonpolar solvents (215,217,218). The use of sulfur dioxide as a solvent and reaction medium has been reviewed (216,219). 

Catalysis in ionic liquids is not limited to biphasic reaction systems. When the reaction mixture is homogeneous, an extraction solvent that is immiscible with the ionic liquid can be used to remove the product. A number of organic solvents display little or only limited miscibility with these liquids. However, this advantage is of limited value in practice, because one major incentive for using ionic liquids is to avoid volatile organic compounds. 

During the 1940s, a large amount of solubility data was obtained by Francis (6, 7), who carried out measurements on hundreds of binary and ternary systems with liquid carbon dioxide just below its critical point. Francis (6, 7) found that liquid carbon dioxide is also an excellent solvent for organic materials and that many of the compounds studied were completely miscible. In 1955, Todd and Elgin (8) reported on phase equilibrium studies with supercritical ethylene and a number of... 

Properties Yellow, oily liquid mild odor. D 0.940 (20/20C), sapon number 125, fp indefinite, becomes cloudy at -32C, solidifies at -65C, flash p 230F (110C) (OC), refr index 1.4614 (20C), Saybolt viscosity 123 sec at 100F, wt/gal 7.8 lb (20C), autoign temp 725F (385C). Miscible with most organic solvents. Almost insoluble in water. Combustible. 

Properties Clear liquid very mild odor. D 1.078, saponification number 369, acidity (as phthalic acid) 0.01 max. Miscible with most organic solvents. Combustible. 

Properties Clear, moderately viscous, pale-yellow liquid mild odor. Miscible with most organic solvents. D 0.965 (25/25C), saponification number 170, hydroxyl value 270, solidifies at-20C, insoluble in water. Combustible. 

---