Water-methanol

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

Add 0 1 g. of the aldehyde in 5 ml. of 50 per cent, ethanol to 2 ml. of a 10 per cent, or saturated alcoholic solution of dimedone. If a precipitate does not form immediately, warm for 5 mintues if the solution is still clear at the end of this period, add hot water until the mixture is just cloudy and cool to about 6°. Collect the crystalline derivative and recrystallise it from methanol - water or ethanol - water. 

A solution of chilled dilute H2SO4 (C) is dropped in a solution af methanol, water and NaN02 (B), then methyl nitrite is generated. 

TABLE 8.17 Standard Reference Values pH for the Measurement of Acidity in 50 Weight Percent Methanol-Water... 

The quahty of formamide suppHed by BASE is certified as having a minimum assay of 99.5%. The principal impurities in the material are ammonium formate, methanol, water, and traces of iron. The quaUty of formamide supphed by BASE is certified to meet the specifications given in Table 3. 

The composition of PPG—PEG blends has been determined using gpc with coupled density and RI detectors. PEG and PPG have different response factors for the density and RI detectors which were exploited (173). An hplc system with CHROMPAC RP-18C2g column at 298°C and acetonitrile—water or methanol—water as the mobile phase has been used to gather information about the functionaUty of PPO (174). 

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)... 

Polytitanosiloxane (PTS) polymers containing Si—O—Ti linkages have also been synthesized through hydrolysis—polycondensation or hydrolysis—polycondensation—pyrolysis reactions involving clear precursor sol solutions consisting of monomeric silanes, TYZOR TET, methanol, water, and hydrochloric acid (Fig. 2). These PTS polymers could be used to form excellent corrosion protection coatings on aluminum substrates (171). 

Chromatographic conditions elution with 50 50 methanol/water solvent at the rate of 1.5 ml,/min through a DuPont Zorbax ODS column using a Waters R-401 Refractive Index Detector. 

The electrochemical conversions of conjugated dienes iato alkadienedioic acid have been known for some time. Butadiene has been converted iato diethyl-3,7-decadiene-l,10,dioate by electrolysis ia a methanol—water solvent (67). An improvement described ia the patent Hterature (68) uses an anhydrous aprotic solvent and an electrolyte along with essentially equimolar amounts of carbon dioxide and butadiene a mixture of decadienedioic acids is formed. This material can be hydrogenated to give sebacic acid. 

Fig. 7. Extractive distillation column profiles for the acetone—methanol—water separation (40). (a) Liquid composition versus theoretical tray location where...

RGA Example In order to illustrate use of the RGA method, consider the following steady-state version of a transfer function model for a pilot-scale, methanol-water distillation column (Wood and Berry, Terminal Composition Control of a Binaiy Distillation Column, Chem. Eng. Sci, 28, 1707, 1973) Ku = 12.8, K = -18.9, K. i = 6.6, and Koo = —19.4. It follows that A = 2 and... 

For ethylene glycol systems copper tubing is often used (up to 3 in), while pumps, cooler tubes, or coils are made of iron, steel, brass, copper, or aluminum. Galvanized tubes should not be used in ethylene glycol systems because of reac tion of the inhibitor with the zinc. Methanol water solutions are compatible with most materials but in sufficient concentration will badly corrode aluminum. 

Ethanol water is a solution of denatured grain alcohol. Its main advantage is that it is nontoxic and thus is widely used in the food and chemic industry. By using corrosion inhibitors it could be made non-corrosive for brine service. It is more expensive than methanol water and has somewhat lower heat transfer coefficients. As an alcohol derivate it is flammable. 

Comparison of Efficiency of Various Plates Several studies of various plates have been carried out under conditions such that direct and meaningful comparisons are possible. Required conditions include identical system, same pressure, same column diameter, and equivalent submergence. Standart and coworkers [B/ Chem. Eng., 11 (11), 1370 (1966) Sep. Sci, 2, 439 (1967)] used the methanol-water system at atmospheric pressure in a 1.0-m (3.3-ft) column. For a plate spacing of 0.4 m (15.7 in) they studied the following ... 

Work at the University of Manchester Institue of Science and Technology (UMIST) has resulted in several papers reporting efficiency data taken in a 0.6-m-diameter column. The systems methanol/water, isopropanoil/water, and toluene methylcyclohexane have been used. The results may be found in Lockett and Ahmed [Chem. Eng. Re.s. Des., 61, 110 (1983)], Korchinsky et al. [Trans. Chem. E., 72, 406 (1994)], and Korchinsky [ibid., 472]... 

The reseai ch has been carried out by the liquid chromatograph Perkin-Elmer (Series 200), which has tandem detectors the diode array (X=210 nm) and the refractometer. The temperature of a column was 30 C, speed of a mobile phase is 1.5 ml/ min. As a mobile phase, mixtures of solvents methanol - water and acetonitrile - water with addition of sodium perchlorate. The columns with the modified silica gel C8 and Cl8 (4.6x220 mm, 5 pm) were used for sepai ation of the AIST and FAS components. In order to make the identification of AIST and FAS components more reliable the ratio of the values of the above-mentioned detectors signals of each substance analyzed. 

We have found out, that a mobile phase methanol - water and a column of the sorbent C8 should be used for sepai ation AIST and FAS components. The duration of the analysis has been 20 minutes. The error of AIST determination does not exceed 2 percent. 

Esi-ms measurements were performed on a Agilent LC M,SD system with the following operational parameters capillary voltage 4.0 kV, cone voltage, 50 V and solvent flow (methanol - water, 50% v/v) 0.3 inL/min. All esi mass specttal data in the positive ion mode were acquired and processed using HP Chem.Station software. The concenttation of aluminum was 0.5 mmol dm while that of mfx were varied in the interval 0.5-1.0 mmol dm. The pH values were pH 4.0, 6.0, 7.2 and 8.5. The specttum obtained at A1 to mfx concenttation ratio 1 2 and pH 4.0 is shown in Fig. 1. 

HPLC analysis of anatoxin-a was first carried out by Astrachan and Archer, " who extracted the toxin from Anabaenaflos-aquae using chloroform followed by hydrochloric acid. The HPLC analysis was carried out on an ODS column using hypochlorate-methanol. Other systems used since include acetic acid extraction and analysis on a reversed-phase C g column using methanol-water mobile phase, and extraction in water after ultrasonication and analysis on reversed-phase... 

It was recrystd twice as the free base from ethanol or methanol/water by dropwise addition of NaOH (less than O.IM). The ppte was washed with water and dried under vacuum. It was dissolved in CHCI3 and chromatographed on alumina the main sharp band was collected, concentrated and cooled to -20 . The ppte was filtered, dried in air, then dried for 2h under vacuum at 70°- [Stone and Bradley J Am Chem Soc 83 3627 1961 , Blauer and Linschitz J Phys Chem 66 453 1962.]... 

Ethanol-water Methanol-water Other solvents Y... 

Silica gel, per se, is not so frequently used in LC as the reversed phases or the bonded phases, because silica separates substances largely by polar interactions with the silanol groups on the silica surface. In contrast, the reversed and bonded phases separate material largely by interactions with the dispersive components of the solute. As the dispersive character of substances, in general, vary more subtly than does their polar character, the reversed and bonded phases are usually preferred. In addition, silica has a significant solubility in many solvents, particularly aqueous solvents and, thus, silica columns can be less stable than those packed with bonded phases. The analytical procedure can be a little more complex and costly with silica gel columns as, in general, a wider variety of more expensive solvents are required. Reversed and bonded phases utilize blended solvents such as hexane/ethanol, methanol/water or acetonitrile/water mixtures as the mobile phase and, consequently, are considerably more economical. Nevertheless, silica gel has certain areas of application for which it is particularly useful and is very effective for separating polarizable substances such as the polynuclear aromatic hydrocarbons and substances... 

When the relationship between the distribution coefficient of a solute and solvent composition, or the corrected retention volume and solvent composition, was evaluated for aqueous solvent mixtures, it was found that the simple relationship identified by Purnell and Laub and Katz et al. no longer applied. The suspected cause for the failure was the strong association between the solvent and water. As a consequence, the mixture was not binary in nature but, in fact, a ternary system. An aqueous solution of methanol, for example, contained methanol, water and methanol associated with water. It follows that the prediction of the net distribution coefficient or net retention volume for a ternary system would require the use of three distribution coefficients one representing the distribution of the solute between the stationary phase and water, one representing that between the stationary phase and methanol and one between the stationary phase and the methanol/water associate. Unfortunately, as the relative amount of association varies with the initial... 

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