Methanol, properties surface tension

As has already been described in Table 9.1, transport properties are enhanced in CXLs compared with conventional solvents. For example, diffusivities of solutes are enhanced up to 7-fold in carbon dioxide expanded methanol, with little effect being seen on the nature of the solute (benzene pyrazine). Therefore, it is thought that physical rather than chemical interactions are causing this phenomenon, including reduced viscosity and surface tension upon carbon dioxide addition. The solubility of solids, liquids and gases in CXLs will... 

Solubility practically insoluble in ether very soluble in acetone, ethanol (95%), methanol, propanol, and water. Aqueous solutions of benzalkonium chloride foam when shaken, have a low surface tension and possess detergent and emulsifying properties. 

Very recently, the separation of polar analytes has also been performed by using pure water under subcritical conditions. Subcritical water has several unique characteristics. For example, the dielectric constant, surface tension, and viscosity of water are dramatically decreased by raising the water temperature while a moderate pressure is applied to keep water in the liquid state. At 200 -250°C, the values of these physical properties are similar to those of pure methanol or acetonitrile at ambient conditions. Therefore, subcritical water may be a potential mobile phase for polar analytes. SFC mobile phases other than CO2 are reviewed separately in this encyclopedia. 

Properties (Pure 100% absolute alcohol, dehydrated) Colorless, limpid, volatile liquid ethereal vinous odor pungent taste. Bp 78.3C, fp -117.3C, refr index 1.3651 (15C), surface tension 22.3 dynes/ cm (20C), viscosity 0.0141 cP (20C), vap press 43 mm Hg (20C), specific heat 0.618 cal/g K (23C), flash p 55F (12.7C), d 0.816 (15.56C), bp 78C, fp -114C, autoign temp 793F (422C). Miscible with water, methanol, ether, chloroform, and acetone. (95% alcohol)... 

The viscosity of liquids is a material property, whose value can span several orders of magnitude. Whereas, for example, the surface tension a and the density p of liquids differ not more than hy a factor of 3 from one another (e.g. a of methanol and water and p of methanol and concentrated sulfuric acid), the differences in the viscosity between water and e.g. sugar syrup at room temperature amounted to 5 x lO This fact has a large influence on flow behaviour and on momentum, mass and heat transfer. 

Here Y denotes a general bulk property, Tw that of pure water and Ys that of the pure co-solvent, and the y, are listed coefficients, generally up to i=3 being required. Annotated data are provided in (Marcus 2002) for the viscosity rj, relative permittivity r, refractive index (at the sodium D-line) d. excess molar Gibbs energy G, excess molar enthalpy excess molar isobaric heat capacity Cp, excess molar volume V, isobaric expansibility ap, adiabatic compressibility ks, and surface tension Y of aqueous mixtures with many co-solvents. These include methanol, ethanol, 1-propanol, 2-propanol, 2-methyl-2-propanol (tert-butanol), 1,2-ethanediol, tetrahydrofuran, 1,4-dioxane, pyridine, acetone, acetonitrile, N, N-dimethylformamide, and dimethylsulfoxide and a few others. 

Frisch and Frisch also measured the critical surface tension on several epoxy/polyurethane SINs. Water-methanol and methanol-ethylene glycol mixtures were employed, using the advancing contact angle method. Interestingly, at the network compositions where the SIN samples possessed maxima in their ultimate mechanical properties, such as lap-shear strength (see Figure 7.17), the critical surface tensions exhibited pronounced minima. 

The solution properties of ordinary salts, such as NaCl, in water are rather simple. One can dissolve at a given temperature a specific amount of NaCl, giving a saturated solution (approximately 5 mol/L). Similarly, the solution characteristics of methanol or ethanol in water are also simple and straightforward. These alcohols mix with water in all proportions. However, the solution behavior of surfactant molecules in water is much more complex. Besides the effect on surface tension, the solution behavior is found to be dependent on the charge of the surfactant. Surfactant aqueous solutions manifest two major forces that determine the solution behavior. The alkyl part being hydrophobic would tend to separate out as a distinct phase, while the polar part tends to stay in solution. The difference between these two opposing forces thus determines the solution properties. The factors that one has to consider are the following ... 

Acetone, IPA, and methanol were purchased on lab or from local chemical vendors and were used, as received. All chemicals were of high grade purity (>99.5% pure). Standard distilled water was used for the pure water and diluted water/methanol tests. To reduce uncertainty in the data due to a reduction in water surface tension due to the presence of impurities, the water bottles were subjected to the shake test to ensure minimum surfactant concentration. The shake test uses the property that foam fraction is an effective separation process for surfactants in aqueous solutions. Simply shake a sample of the water in a clean volumetric flask. Any bubbles will immediately break if the surfactant concentration due to contamination is ignorable. 

The temperature dependence of many properties of methanol has been described in figures, tables, and equations. Plots of vapor pressure, liquid density, liquid heat capacity, vapor heat capacity, heat of vaporization, surface tension, liquid thermal conductivity, vapor thermal conductivity, liquid viscosity, and vapor viscosity against temperature have been given by Yaws [13] and by Flick [14]. Tables of vapor pressure [3,1517], liquid density [3,15,17], liquid volume [16], vapor density [15,17], vapor volume [16], liquid viscosity [15,18], vapor viscosity [15], surface tension [15,19], liquid heat capacity [15,17,20], vapor heat capacity [3,15,17], solid heat capacity [11], liquid thermal conductivity [15,17], vapor thermal conductivity [15], second viral coefficient [16], dielectric constant [21], refractive index [3], and heat of vaporization [16] have also been published. Thermodynamic properties of methanol in the condensed phases have been tabulated by Wilhoit et al. [11], and those in the gas phase have been given by Chao et aL [9]. 

Properties including freezing point, boiling point, and flash point of methanol-water solutions of different methanol contents have been given by Flick [14]. Data for density [14,29], viscosity [14], vapor pressure [14,29], thermal conductivity [14], specific heat [14,29], surface tension [30], and refractive index [31] at selected temperatures have also been tabulated. Heat of mixing can be found in Reference 32. Diffusion coefficients of methanol and water in methanol-water solutions have been evaluated in detail by Derlacki et al. [33]. 

Anderson s group (Pino et al., 2009) studied the micellar properties of aqueous solutions of two ILs, l-hexadecyl-3-butylimidazolium bromide and 1,3-didodecylimidazolium bromide, in the presence of several organic solvents (methanol, 1-propanol, 1-butanol, l-p>entanol, and acetonitrile) by surface tensiometiy. For both ILs, increases in the cmc values and minimum surface area per surfactant molecule, decreases in the maximum surface excess concentration, adsorption efficiency and effectiveness of surface tension reduction were obtained when increasing the organic solvent content. 

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