Solvent capacity

Aguilar M A and Olivares del Valle F J 1989 Solute-solvent interactions. A simple procedure for constructing the solvent capacity for retaining a molecular solute Ohem. Rhys. 129 439-50... 

Among the properties sought in the solvent are low cost, avadabihty, stabiUty, low volatiUty at ambient temperature, limited miscibility in aqueous systems present in the process, no solvent capacity for the salts, good solvent capacity for the acids, and sufficient difference in distribution coefficient of the two acids to permit their separation in the solvent-extraction operation. Practical solvents are C, C, and alcohols. For industrial process, alcohols are the best choice (see Amyl alcohols). Small quantities of potassium nitrate continue to be produced from natural sources, eg, the caUche deposits in Chile. 

Column Source pH range Maximm solvent (%) Capacity... 

Supercritical carbon dioxide was used for bone delipidation. It appeared that this technology is very efficient since supercritical CO2 is able to diffuse into microporous solids much better than liqnids and that it has a good solvent capacity for lipids. Moreover, it is safe since it involves no toxic chemical and is potentially usable with allografts as well as xenografts (Fages et al., 1994). 

A way around this issue may have been found with the use of supercritical fluids. These materials, such as liquid carbon dioxide, have many interesting properties from the point of view of pharmacutical processing since they combine liquid-like solvent properties with gas-like transportation properties. Small changes in the applied pressure or temperature can result in large changes of the fluid density and, correspondingly, the solvent capacity and properties of the resultant particles. 

The relative retention of two components is the quotient of their adjusted retention times. The capacity factor for a single component is the adjusted retention time divided by the elution time for solvent. Capacity factor gives the ratio of time spent by solute in the stationary phase to time spent in the mobile phase. When a separation is scaled up from a small load to a large load, the cross-sectional area of the column should be increased in proportion to the loading. Column length and linear flow rate are held constant. 

The viscosity of nitrocellulose solutions is to some extent dependent on the composition of the solvent, and on its solvent capacity or strength . Masson and McCall [58] have examined the viscosity of nitrocellulose solutions in acetone to which different amounts of water had been added. They obtained a curve, reproduced in Fig. 101, that illustrates the effect of the water content of the acetone on the viscosity of nitrocellulose solutions. 

The gas anti-solvent processes overcome the limited solvent capacity of supercritical gases for substances with high molecular weight by using a classical liquid solvent. 

FORMAMIDE. Form amide (meibanamide), HCONHi. is the lirsi member of the primary amide series and is the only one liquid at room temperature. II is hygroscopic and has a faint odor of ammonia. Formamide is a colorless to pale yellowish liquid, freely miscible with water, lower alcohols and glycols, and lower esters and acetone. It is virtually immiscible in almost all aliphatic and aromatic hydrocarbons, chlorinated hydrocarbons, and ethers. By virtue of its high dielectric constant, close to that of water and unusual for an organic compound, formamide has a high solvent capacity lor many heavy-metal salts and for salts of alkali and alkalinc-carth metals. It is an important solvent, in particular for resins and plasticizers. As a chemical intermediate, formamide is especially useful in the synthesis of heterocyclic compounds, pharmaceuticals, crop protection agents, pesticides, and for the manufacture of hydrocyanic acid. 

Additional naturally occurring lipids may be minor components of oral lipid-based formulations. Terpenes such as peppermint oil (>50% menthol) are fairly hydrophobic but can provide some solvent capacity. Steroids such as cholesterol, while important in topical and in parenteral liposomal products, are not important as oral pharmaceutical adjuvants. Phospholipids (e.g., egg or soybean phosphatidylcholine) an essential component of cell membranes, are considered polar lipids, and have surfactant properties. 

SigniDcance of aqueous Limited Solvent capacity Some loss of solvent SigniDcant phase... 

Since both ethylene and ethane have reduced temperatures nearly equal to unity at the extraction conditions of 20 C, (T =. 98) and ethylene (T = 1.04), their respective solvent capacities for butene should be about the same. This is the case as is reflected in the same values for the selectivity against butene for all pure solvent gases. One can conclude that the primary effect of the non-polar solvent is to increase the capacity of the "vapor" phase for the extracted solute near the critical. The influence of the second solvent provides only the option of modifying the physical parameters namely, pressure and temperature, under which the optimal extraction is to be conducted. The evidence for this is the effect of the ammonia on the selectivity as calculated by the EOS in Table V. The higher values for the selectivities in the ethylene mixtures are pronounced. It can be concluded that the solvent mixture interaction parameters must dominate the solubility of butene in the vapor phase. 

Closely linked to its extraordinary solvent capacities is water s role in transporting dissolved materials throughout the organism. With the exception of air-filled channels like the tracheal systems of insects, most of the transport processes of organisms involve movement of dissolved solutes. Diffusion of solutes within water is rapid, as is the translational and rotational movement of water itself. The extensive networks of hydrogen bonds that form among water molecules and between water and solutes do not impede this dynamic move-... 

The chemical properties that appear to underlie the fitness of the four classes of organic osmolytes include the following. First, these osmolytes are polar molecules that have high solubilities in water. They can be accumulated to high concentrations without unduly taxing the solvent capacity of the cell. Glycerol,... 

A familiar example of this type of metabolite adaptation is the thiol ester derivative of acetic acid, acetyl-coenzymeA (acetylCoA). AcetylCoA has a much larger negative free energy of hydrolysis than acetate, so metabolic transformations involving the acetate ion can occur with much lower concentrations of acetylCoA than of acetate. Phosphorylated metabolic intermediates likewise allow metabolites to have high chemical potentials and occur at relatively low concentrations in the cellular water. Use of such activated intermediates enables the cell to avoid high concentrations of metabolites that can tax solvent capacity and, perhaps more important, disrupt the cell through uncontrolled chemical reactions with inappropriate molecules. 

Atkinson, D.E. (1969). Limitation of metabolite concentrations and the conservation of solvent capacity in the living cell. In Current Topics in Cellular Regulation 1 29-43. New York Academic Press. 

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