Volatility of the solvent

Solvent volatility is an important factor in electrospinning. Since electrospinning requires a quick evaporation rate and phase separation, vapor pressure of the solvent affects the dr5dng time and evaporation rate. Other parameters affecting evaporation rate are boiling point, specific heat, enthalpy and heat of vaporization, rate of heat supply, interaction between solvent molecules, surface tension of the liquid, and air movement above the liquid surface. 

Solvent volatility is also an important factor in determining the properties of fibrous structures produced by electrospinning. In the electrospinning process, solvent evaporation occurs while the jet travels from the tip of the syringe to the collector. If all of the solvent evaporates on the way, fibers can be formed and deposited on the collector. However, if some solvent remains on the pol5mier, instead of dry fibers, wet fibers or thin films can be produced. Solvent volatility might play a role on the formation of pores in the fibers. A decrease in the solvent volatility resulted in a smoother fiber surface. Low-boiling-point solvents are desirable because evaporation of the solvent is enhanced and deposition of the fibers becomes easier. A rapid evaporation rate of the solvent can cause the fibers to form as ribbons with various cross sections. 

---

Other effects. In addition to the compound formation and ionisation effects which have been considered, it is also necessary to take account of so-called matrix effects. These are predominantly physical factors which will influence the amount of sample reaching the flame, and are related in particular to factors such as the viscosity, the density, the surface tension and the volatility of the solvent used to prepare the test solution. If we wish to compare a series of solutions, e.g. a series of standards to be compared with a test solution, it is clearly essential that the same solvent be used for each, and the solutions should not differ too widely in their bulk composition. This procedure is commonly termed matrix matching. 

Treated solids leave the extraction subsystem with trace amounts of extraction solvent, which usually volatilizes quickly. Ambient air should be monitored to determine if the volatilization of the solvent presents a problem. 

The pressure generated in a reaction vessel, and hence the rate enhancement, depends on a number of factors including the MW power level, the volatility of the solvent, the dielectric loss of the reaction mixture, the size of the vessel and the volume of the reaction mixture [7, 20]. Gedye et al. [20] found that, in the esterification of benzoic acid with a series of aliphatic alcohols (Scheme 4.1) in closed Teflon vessels, the most dramatic rate enhancements were observed with methanol (the most volatile solvent). 

The stability of the deposit after immersion will depend on the volatility of the solvent, amongst other factors. 

Even though all three reactors share the same precursor delivery system, each tool offers specific advantages. For example, a cold-wall reactor (reactor B) helps prevent decomposition of the precursor before it reaches the substrate. A pulsed aerosol injection system at low pressure (reactor C) allows the film to grow under better-defined conditions than in a continuous process (reactor A) because of the minimization of undesirable transient effects caused by the high volatility of the solvents used.46 A more detailed description of each of the conditions for film growth, including reactor type, precursor type, delivery method, deposition temperature, growth time, and other parameters are summarized in Table 6.2. Depositions were done on bare and Mo-coated... 

Another important merit of the in situ gellification , rarely mentioned by various authors in the literature, is that the limitation on electrolyte composition can be relaxed. In the traditional process of making a GPE, the liquid electrolyte has to be heated with the polymer host to form the gel, during which the thermal instability of the lithium salt (LiPFe or LiBF4) and the volatility of the solvents (DMC, EMC, etc) could possibly cause the resultant GPE to deviate from the desired composition or even to degrade. It is for this reason that in most of the literature on GPE the liquid electrolytes have to be based on Lilm, LiBeti as salts, and EC/PC as solvents. In Bellcore technology, on the contrary, the state-of-the-art electrolytes, the typical of which is LiPFe/EC/DMC, could be used, since gellification occurs only after the cells are assembled. ... 

The type of vessel employed depends on volatility of the solvent obviously the conical flask already recommended for "crystallization by cooling" is not suitable for spontaneous evaporation, while a beaker or shallow dish is. When the latter type of vessel is used, "crusts" often form on the sides above the surface of the liquid. Such cmsts seldom consist of pure substance so they should be removed carefully with a spatula or spoon before attempting to filter off the crystals. 

The effect of salts on the vapor-liquid equilibrium of solvent mixtures has been of considerable interest in recent years. Introduction of a salt into a binary solvent mixture results in a change in the relative volatility of the solvents. This effect can be used to an advantage where the separation of the solvents is of interest. Furter and co-workers have demonstrated the potential importance of salts as separating agents in extractive distillation (J, 2, 3). 

Two approaches have been used in correlating the phase equilibrium behavior of complex mixtures involving a non-volatile salt dissolved in a binary solvent mixture. Johnson and Furter (i) developed what appears to be the most popular approach by correlating the ratio of relative volatilities of the solvents as a function of salt concentration. Meranda and Furter (2) review this approach and present experimental determinations of the necessary parameters as a function of mole fraction of one of the solvents. 

Pigments (if required)—to impart colour to the eventual dry film of adhesive. The nature of the solvent plays an important part in establishing the properties of the adhesive as examples, the volatility of the solvent influences the speed of drying and the time during which adhesive-coated surfaces are capable of forming a bond when brought into contact. 

Isolation from atmospheric contaminants and volatility of the solvents may present problems in the application of STM to nonaqueous electrochemical systems. 

The low volatility of the solvent also dictates that it be introduced in the column near the top, above the main feed, in order to maintain the required solvent concentration in as many trays as possible. The column thus contains three sections the top section between the overhead product and the solvent feed, the middle section between the solvent feed and the main feed, and the bottom section between the main feed and the bottoms product. The top section serves to reflux any solvent that might have risen with the vapor above the solvent feed. The objective is to minimize the solvent concentration in the overhead product. The middle section serves to absorb the component whose volatility has been lowered by the solvent and to minimize its concentration in the overhead. The lower section serves to strip out the component with the higher volatility and minimize its concentration in the bottoms. 

An effective solvent for an extractive distillation is one which is attracted to one or more of the components. This attraction of the solvent for these components reduces the volatility of the solvent as well as the volatilities of the components to which it is attracted. It is desirable that the attraction occur in the natural direction, that is, that the solvent be attracted to the relatively heavy components. However, this is not a necessary condition for the behavior of the solvent. Many separations are carried out in which one of the relatively light components is attracted by the solvent and removed in the bottom product with the solvent. 

The development time should be sufficient to separate the components of interest. The rate of solvent movement depends on factors such as the porosity of the paper, the surface tension, viscosity, and volatility of the solvent, and the ambient temperature. Reasonable Ri values for good resolution are about 0.4-0.8 typical separation times for modern PC papers are in the range of 2-4 hours. 

Steam stripping is also long established and its cost is very dependent on the relative volatility of the solvent being stripped from the water. In favourable circumstances, when P is very large, figures below US 1/m before solvent credit maybe achieved, but for methanol US 3-4 would be more likely. 

---