Alcohols isopropanol/water mixture

The shifting of A] A2 is of practical use in separating water rich isopropanol/water mixtures (Fig. 2-31 b). A feed/"is almost completely separated into water flow rate JV leaving column DCl and a isopropanol flow rate P leaving column DC2. Both columns are operated at ambient pressure. The overhead products AT, and JC2 are practically of azeotropic composition (point Aj, Fig. 2-31 a). In the condenser C, most of the condensed overhead products form the reflux / , or / 2, to the columns DCl or DC2, respectively. The remainder is then separated into a water rich fraction >i and an alcohol rich fraction >2 in the diffusion distillation unit DA (Fig. 2-31 c shows the diffusion separation unit). Some of the overhead product fluxes Kj and K2 are heating the unit while water is used for cooling. 

In the presence of salt it was assumed that electrical double layer repulsion is suppressed and the action of the SDS/NaCl solutions was simply to enhance wetting. In a parallel study with isopropanol /water mixtures 5 we found that there exists a linear relationship between wjj and yl where Wq = 0 when the liquid surface tension is equal to the critical wetting tension yc. The value of Yc in these alcohol/water mixtures was ca 22 mNm i which is lower than Ys PET because of the well known adsorption effect 20 and hence the complete inhibition of adhesion due to wetting occurs when yc YS Similar adsorption effects have been observed for SDS solutions 2 and this is reflected by the value of yc oi ca lOmNm determined in this work from contact angle measurements on Mylar film. The measured Wq (= 0.95 yN) in water gives the fallowing expression for as a function of yl assuming that a linear interpolation can be made between YL YC 10 Nm l and yl Ywater 72.2 mNm"l. 

We have studied the effect of monomer concentration in the dispersion polymerization of styrene carried out in alcohol-water mixtures as the dispersion media. We used AIBN and poly(acrylic acid) as the initiator and the stabilizer, respectively, and we tried isopropanol, 1-butanol, and 2-butanol as the alcohols [89]. The largest average particle size values were obtained with the highest monomer-dispersion medium volumetric ratios in 1-butanol-water medium having the alcohol-water volumetric ratio of 90 10. The SEM micrographs of these particles are given in Fig. 15. As seen here, a certain size distribution by the formation of small particles, possibly with a secondary nucleation, was observed in the poly-... 

The construction and preparation of these electrodes were described in chapter 3.1. The modern version of this electrode, produced by Radelkis, Budapest, is a compromise between the original construction described by Pungor etal. [310,311, 313] and a system with a compact membrane. Electrodes with silver chloride, bromide and iodide are manufactured. According to the manufacturer these electrodes should be soaked before use for 1-2 hours in a dilute solution of the corresponding silver halide. They can be used in a pH region from 2 to 12 and the dFisE/d log [X ] value is approximately 56mV. These electrodes can be employed for various automatic analytical methods (see chapter 5). They can readily be used in mixtures of alcohol with water, for example up to 90% ethanol and methanol and up to 4% n-propanol and isopropanol [196]. In mixtures of acetone-water and dimethylformamide-water, they work reliably only in the presence of a large excess of water [197]. 

The free base is liberated from the acid solution with 20% sodium hydroxide solution and taken up in ether. The ether layer is washed with water, saturated with NaCI and then shaken with solid potassium hydroxide. The ether is removed by distillation, 200 parts of benzene added and distilled off. The residue is distilled in vacuo and the fraction 150°-165°C/2 mm is collected and amounts to 433 parts. The hydrochloride salt is prepared by dissolving the free base in anhydrous ether and slowly adding an alcoholic solution of hydrogen chloride. The solid is recrystallized from absolute alcohol-ether mixture or isopropanol-ether mixture and has a MP of 161-162°C. 

An ink is first prepared by stirring a mixture of the catalyst and Nafion solution in an alcohol (e.g., isopropanol)-water solution for several hours. A PTFE emulsion is normally added immediately before the spray process. The ink is then repeatedly sprayed using air brush, air-less spr or electrostatic spray, depending on the size of the electrodes, onto the GDL. Between each spraying, the electrode is sintered. The last step can be the electrode rolling to produce a thin layer of uniform thickness and low porosity. 

Thiamin may be extracted from tissues, foodstuffs or pharmaceutical preparations with aqueous alcohol mixtures at a pH of 4-6 and separated from closely related compounds and metabolites by TLC on cellulose layers or silica gel. Various mobile phases have been used, including isopropanol-water-trichloracetic acid-ammonia (71 9 20 0.3) and butan-l-ol-acetic acid-water (40 10 50) (1). Thiamin may be separated from its hydrolysis and oxidation products by TLC/densitometry (2) and other chromatographic techniques have been reviewed (3). Sandwich-type chambers afford rapid... 

The lower portion of the trap was removed and the inlet tube and dip leg were washed with water into the lower tube. The final volume was adjusted to 2 ml. The aqueous solution was analyzed by gas chromatography for alcohol content. Mixtures containing methanol, ethanol, and isopropanol were readily resolved. Standard solutions of alcohol in water at 5 to 1400 y g/ml were prepared and chromatographed under identical conditions. Peak heights were measured and used to construct a linear calibration curve of peak height vs. alcohol concentration. From this curve, the amount of each alcohol derived from alkoxy present was determined. Percent alkoxy was then calculated using appropriate dilution and weight conversion. 

A general method for the successful recrystallization of such surfactants in good yields has been found that exploits both kinds of phase behavior [99]. In the case of CgAH, for example, the compound may be mixed with acetonitrile (a solvent in which it is poorly soluble) and dissolved by the addition of water or a lower alcohol (methanol, ethanol, isopropanol). Such mixtures are often very good solvents for such compounds but do not yield the crystal phase in acceptable yields on cooling. 

In liquid mixtures of type (2), the solutions of primary interest are azeotropic and other mixtures containing variable amounts of water in organics dehydration of organic solvents containing very small amounts of water. Removal of water from azeotropic mixtures of ethanol-water, isopropanol-water, etc., is extensively practiced using polymeric membranes (of crosslinked polyvinyl alcohol) that are highly polar and selective for water. On the other hand, the membranes that are used to remove VOCs selectively from aqueous solutions are usually highly nonpolar rubbery polymeric membranes, e.g. dimethyl siloxane (silicone rubber). 

H. is produced by - alkoxylation of alkali-cellulose suspended in solvents, such as acetone, isopropanol or tcrt.butanol 0.8-1.5 moles of alkali per AGU are necessary. To decrease viscosity, the alkali-cellulose is degraded by aging (- cellulose) before reaction or by adding hydrogen peroxide to the alkaline reaction mixture. For better efficiency, the addition of ethylene oxide is carried out in two stages. After the first reaction step, only catalytic amounts of alkali are necessary. Reaction takes place in 1-4 h at 30-80 °C and is stopped by neutralization with hydrochloric or acetic acid. Salts are removed by washing with alcohol/water mixtures. If retarded dissolution in water is desired, the wet product is treated with glyoxal. 

The baseline resolution of the first three alcohols reported in Table 4.8 was also obtained by eluting with different mixtures of n-hexane-2-propanol and isopropanol-water (80 20, v/v). It should be noted that enantiomers of Troger s base and 1-acenaphthenol were also resolved on MCTA plates with a- and Rs-values comparable to those found on CTB plates for alcohol and higher for the base. 

A mixture of 14 g (0.05 mol) of a A-diphenyl-7-dlmethylaminovaleronitrile, 16 g (0.2 mol) of sodium acetate, 14 g (0.2 mol) of hydroxylamine hydrochloride and 75 ml of ethyl alcohol was refluxed IB hours. The mixture was cooled, poured Into water and neutralized with ammonium hydroxide. The heavy white precipitate solidified on standing. The material was filtered and recrystallized from isopropanol. After three recrystallizations the aminopentamide product melted at 177° to 179°C. 

The direct synthetic process is described in U.S. Patent 2,772,280. A solution of 73.3 g (0.332 mol) of (3-aminoxyalanine ethyl ester dihydrochloride in 100 ml of water was stirred in a 500 ml 3-necked round-bottomed flask cooled in an ice-bath. To the above solution was added over a 30-minute period 65.6 g (1.17 mols) of potassium hydroxide dissolved in 100 ml of water. While the pH of the reaction mixture was 7 to 10.5, a red color appeared which disappeared when the pH reached 11 to 11.5. The light yellow solution was allowed to stand at room temperature for 14 hour and then added to 1,800 ml of 1 1 ethanol-isopropanol. The reaction flask was washed twice with 10 ml portions of water and the washings added to the alcohol solution. The precipitated salts were filtered out of the alcohol solution and the filtrate cooled to 5°C in a 5 liter 3-necked round-bottomed flask. To the cold, well-stirred solution was added dropwise over a 35-minute period sufficient glacial acetic acid to bring the pH of the alcohol solution to 6.0. When the pH of the solution had reached 7 to 7.5, the solution was seeded and no further acetic acid added until Crystallization of the oil already precipitated had definitely begun. The crystalline precipitate was collected on a filter, washed twice with 1 1 ethanol-isopropanol and twice with ether. The yield of 4-amino-3-isoxazolidone was 22.7 g. 

The selective separation of water from aqueous solutions of isopropanol or the dehydration of isopropanol can be carried out with different membranes, which contain polar groups, either in the backbone or as pendent moieties. For the dehydration of such a mixture, poly(vinyl alcohol) (PVA) and PVA-based membranes have been used extensively. PVA is the primary material from which the commercial membranes are fabricated and has been studied intensively for pervaporation because of its excellent film forming, high hydrophilicity due to -OH groups as pendant moieties, and chemical-resistant properties. On the contrary, PVA has poor stability at higher water concentrations, and hence selectivity decreases remarkably. 

Hybrid membranes composed of poly(vinyl alcohol) (PVA) and tetraethylorthosilicate (TEOS), synthetised via hydrolysis and a co-condensation reaction for the pervaporation separation of water-isopropanol mixtures has also been reported [32], These hybrid membranes show a significant improvement in the membrane performance for water-isopropanol mixture separation. The separation factor increased drastically upon increasing the crosslinking (TEOS) density due to a reduction of free volume and increased chain stiffness. However, the separation factor decreased drastically when PVA was crosslinked with the highest amount of TEOS (mass ratio of TEOS to PVA is 2 1). The highest separation selectivity is found to be 900 for PVA TEOS (1.5 1 w/w) at 30°C. For all membranes, the selectivity decreased drastically up to 20 mass % of water in the feed and then remained almost constant beyond 20 mass %, signifying that the separation selectivity is much influenced at lower composition of water in the feed. 

Much emphasis has been placed on the selectivity of quaternary ammonium borohydrides in their reduction of aldehydes and ketones [18-20]. Predictably, steric factors are important, as are mesomeric electronic effects in the case of 4-substituted benzaldehydes. However, comparison of the relative merits of the use of tetraethyl-ammonium, or tetra-n-butylammonium borohydride in dichloromethane, and of sodium borohydride in isopropanol, has shown that, in the competitive reduction of benzaldehyde and acetophenone, each system preferentially reduces the aldehyde and that the ratio of benzyl alcohol to 1-phenylethanol is invariably ca. 4 1 [18-20], Thus, the only advantage in the use of the ammonium salts would appear to facilitate the use of non-hydroxylic solvents. In all reductions, the use of the more lipophilic tetra-n-butylammonium salt is to be preferred and the only advantage in using the tetraethylammonium salt is its ready removal from the reaction mixture by dissolution in water. 

A mixture of 70% 2-propanol (isopropanol) and 30% water is sold as rubbing alcohol, which may be used to help reduce a fever. Explain how this process works. 

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