Water + methanol mixtures

The following data have been reported for methanol-water mixtures at 20°C Handbook of Chemistry and Physics, U.S. Rubber Co.) ... 

Reversed-phase hplc has been used to separate PPG into its components using evaporative light scattering and uv detection of their 3,5-dinitroben2oyl derivatives. Acetonitrile—water or methanol—water mixtures effected the separation (175). Polymer glycols in PUR elastomers have been identified (176) by pyrolysis-gc. The pyrolysis was carried out at 600°C and produced a small amount of ethane, CO2, propane, and mostiy propylene, CO, and CH4. The species responsible for a musty odor present in some PUR foam was separated and identified by gc (Supelco SP-2100 capillary column)... 

Employing an iterative computer program, in conjunction with the above equations, Katz et al. examined a wide range of values for (k) and (Vmw) nd calculated the volume change on mixing of a series of methanol/water mixtures having assumed volume fractions of methanol. The results for each selected values of (k) and (Vmw) and each volume fraction of methanol were compared with experimentally determined values of (vj) and the specific values of (k) and (Vmw) that gave the minimum error... 

Figure 25. Graph of Volume Change on Mixing against Solvent Composition for Methanol/Water Mixtures...

Using the average value for the equilibrium constant, the distribution concentration of the different components of a methanol water mixture were calculated for initial methanol concentrations ranging from zero to 100%v/v. The curves they obtained are shown in Figure 28. The molar refractivities of 11.88 is also in accordance with that expected since the molar refractivity s of water and methanol are 3.72 and 8.28 respectively. The refractive index of the associate of 1.3502 is, as would be expected, higher than that of either water or methanol. 

Using the results calculated from the density data, the concentration of the individual components of the methanol/water mixture at different temperatures can be computed thus disclosing the effect of temperature on the elution properties of methanol/water mixtures. The results are shown in Figure 30. 

Considering the hexadecane/water-methanol system the same arguments and treatment can be afforded to the methanol/water mixture on the assumption that it is a ternary mixture containing methanol, water and methanol associated with water. Thus, the equation used for the system of Katz et al. reduces to... 

Figure 31. Graph of the Distribution Coefficient of the Solutes between Methanol/Water Mixtures and Hexadecane against Volume Fraction of Methanol in the Original Mixture...

The crude ketal from the Birch reduction is dissolved in a mixture of 700 ml ethyl acetate, 1260 ml absolute ethanol and 31.5 ml water. To this solution is added 198 ml of 0.01 Mp-toluenesulfonic acid in absolute ethanol. (Methanol cannot be substituted for the ethanol nor can denatured ethanol containing methanol be used. In the presence of methanol, the diethyl ketal forms the mixed methyl ethyl ketal at C-17 and this mixed ketal hydrolyzes at a much slower rate than does the diethyl ketal.) The mixture is stirred at room temperature under nitrogen for 10 min and 56 ml of 10% potassium bicarbonate solution is added to neutralize the toluenesulfonic acid. The organic solvents are removed in a rotary vacuum evaporator and water is added as the organic solvents distill. When all of the organic solvents have been distilled, the granular precipitate of 1,4-dihydroestrone 3- methyl ether is collected on a filter and washed well with cold water. The solid is sucked dry and is dissolved in 800 ml of methyl ethyl ketone. To this solution is added 1600 ml of 1 1 methanol-water mixture and the resulting mixture is cooled in an ice bath for 1 hr. The solid is collected, rinsed with cold methanol-water (1 1), air-dried, and finally dried in a vacuum oven at 60° yield, 71.5 g (81 % based on estrone methyl ether actually carried into the Birch reduction as the ketal) mp 139-141°, reported mp 141-141.5°. The material has an enol ether assay of 99%, a residual aromatics content of 0.6% and a 19-norandrost-5(10)-ene-3,17-dione content of 0.5% (from hydrolysis of the 3-enol ether). It contains less than 0.1 % of 17-ol and only a trace of ketal formed by addition of ethanol to the 3-enol ether. 

Figure 8-4. Fraction of total base present as hydroxide as a function of the percentage of water in the binary solvent, lor ethanol-water and methanol-water mixtures. ...

Hydrogenation was accomplished over freshly prepared W-2 Ra-Ni in a 5 1 methanol-water mixture containing 3 equiv of acetic or boric acid. The hydrogenolysis has been applied smoothly to the synthesis of C-nucleosides... 

The column was then eluted with 0.0025N sulfuric acid in methanol-water mixture (1 1 v/v). A total of 900 ml of fractions containing a substance which showed UV absorption at 290 m/u was collected. After removal of methanol by distillation, the residual liquid was adjusted to pH 6.0 with Dowex 44 (OH type) and freeze-dried to obtain 9.3 g (95% yield) of NK631 monosulfate (copper-free form) in the form of pale yellowish-white amorphous powder. 

We have found that in the system of presulfate initiator, the PVAc latexes are not dissolved transparently in the methanol-water mixture [8], and in the system of HPO initiator, the extraction of the polymer from the PVAc latex films with acetone greatly depends on the polymerization condition [9]. These results suggest that if a polymerization method can be found in which the grafting polymerization of VAc onto PVA is controlled to the minimum, a large portion of PVAc in the latex film will have a chance of extraction with solvents. In this Chapter, the preparations of the unique porous films from the PVAc latexes containing PVA as a protective colloid by an extraction of the PVAc particles with acetone and the characteristic properties of the porous films are summarized. 

Electrodes and Galvanic Cells. The Silver-Silver Chloride Electrode. The Hydrogen Electrode. Half-cells Containing an Amalgam, Electrode. Two Cells Placed Back to Back. Cells Containing Equimolal Solutions. The Alkali Chlorides as Solutes. HC1 in Methanol or Ethanol Containing a Trace of Water. The Alkali Chlorides in Methanol-Water Mixtures. The Heal of Solution of HC1. Proton Transfer Equilibrium from Measurements of E.M.F. 

In the cells discussed in Sec. 57 the solvent in every case was water. But in this chapter we shall discuss cells placed back to back, where one solution contains a solute dissolved in water, while the other contains the same solute dissolved in ethanol, or in methanol, or in a methanol-water mixture. When, for example, a hydrogen electrode containing IIC1 dissolved in ethanol is coupled to a Ag/AgCl electrode, also containing HC1 dissolved in ethanol, the cell may be written... 

The cells with equimolaj solutions of IIC1, placed back to back, were found to yield an e.m.f. of 0.232 volt. Converting to electron-volts, and subtracting 0.030, we find 0.202 as the value of the work required to transfer one Cl- ion and one proton from water to methanol. This value, 0.202, has been plotted on the right-hand side of Fig. 61 the other points plotted give values obtained with methanol-water mixtures. These will be discussed below. 

The Alkali Chlorides as Solutes. In order to make a similar study of the transference of KC1, NaCl, and LiCl between water and methanol-water mixtures, the hydrogen electrode was replaced by an amalgam electrode, as described in Sec. 111. The arrangement when two cells having potassium amalgam electrodes are placed back to back may be written... 

Fin. 01. Abscissas give the reciprocal of the dielectric constant of the methanol-water mixture. 

In their measurements with the cell (195) containing methanol, Non-hebel and Hartley1 verified by direct experiment that the addition of a small drop of water to either side of the cell, sufficient to give a mole fraction of I120 equal to about 0.001, produced a change in the e.m.f. equal to a few millivolts. This was attributed mainly to the proton transfer (44). The curve for HOI in methanol-water mixtures must thus have a very steep slope, as has been sketched on the right-hand side of Fig. 01. 

The Alkali Chlorides in Methanol-Water Mixtures. Turning to the results for KC1, NaCl, and LiCl, plotted in Fig. 61, we see that in each case the values are nearly linear with 1/t, suggesting that the results may be simply interpreted in terms of electrostatic theory. This apparent simplicity is, however, illusory. In the first place, KC1 gives greater e.m.f. s than NaCl, while LiCl gives smaller e.m.f. s whereas in Sec. 114 we deduced from (199) that the contrary should be the case. In the second place, if a simple electrostatic interpretation is to be given for the variation of AF with the composition of the solvent, a similar simple... 

Mole fraction of methanol Fiu 64. AF, —T AS, and AH for the transfer of the ion pair (Na+ + CS-) from water to methanol-water mixtures. 

The sequence Gly-Glu-Arg... folds better in water than in methanol as shown below. Many folding investigations have shown clearly different influences of the solvents. Even in many cases, folding can be enhanced in methanol, or methanol/water mixtures, trifluoroethanol, buffer solutions, or higher concentrated salt solutions. 

The dead point is obtained by including in the sample a trace of an unretained solute or, more often, one of the components of the mobile phase. For example, when using a methanol water mixture as the mobile phase, the dead point is obtained from the elution of a pure sample of methanol. The pure methanol can often be monitored, even by a UV detector, as the transient change in refractive index resulting from the methanol is sufficient to cause a disturbance that is detectable. 

ODS3 is a "bulk type" reverse phase (the meaning of which will be discussed later) which has a fairly high capacity and is reasonably stable to small changes in pH. The column was 25 cm long, 4.6 mm in diameter and the mobile phase a methanol water mixture containing acetic acid. In this particular separation the solvent mixture was programmed, a development procedure which will also be discussed in a later chapter. 

It is the solvent, in this case methanol, that is responsible for reducing the distribution coefficients of the solutes with respect to the stationaiy phase (and consequently, their retention) by increasing the solute-solvent interactions in the mobile phase. Bearing this in mind, then the curves shown in figure 11 can explain some of the unique characteristics of methanol water mixtures when used as the mobile phase in reversed phase LC. 

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