Ethanol-water composition, solute solubility

The salt effects of potassium bromide and a series office symmetrical tetraalkylammonium bromides on vapor-liquid equilibrium at constant pressure in various ethanol-water mixtures were determined. For these systems, the composition of the binary solvent was held constant while the dependence of the equilibrium vapor composition on salt concentration was investigated these studies were done at various fixed compositions of the mixed solvent. Good agreement with the equation of Furter and Johnson was observed for the salts exhibiting either mainly electrostrictive or mainly hydrophobic behavior however, the correlation was unsatisfactory in the case of the one salt (tetraethylammonium bromide) where these two types of solute-solvent interactions were in close competition. The transition from salting out of the ethanol to salting in, observed as the tetraalkylammonium salt series is ascended, was interpreted in terms of the solute-solvent interactions as related to physical properties of the system components, particularly solubilities and surface tensions. 

Reaction mixtures are complex multicomponent systems, and their phase behavior is dictated by the composition of the mixture and operating conditions. Organic solvents present in the reaction medium as reagents may act as cosolvents and result in solute solubility enhancement (as discussed in Section 4.2). For example, the decrease in reaction rate observed at high ethanol concentrations for the lipase-catalyzed esterification of myristic acid + ethanol in SCCO2 has been, in part, attributed to the solubility enhancement of water, resulting in drying of the enzyme... 

Raman spectroscopy has been shown to be useful in the study of the kinetics associated with the solution-mediated aqueous transformation of anhydrous carbamazepine to its dihydrate phase. Using a Raman immersion probe to establish the phase composition, the thermodynamics associated with the system were studied in ethanol-water mixtures through measurements of the solubility of both forms over the temperature range of 0-60 Raman spectroscopy was also... 

Figure 2 shows the incremental surface tension (y - Yq) 0,2% (w/w) polymer solutions as a function of solvent composition for both HEC and HMHEC over the entire composition range in which each polymer was soluble. Also shown is the surface tension of the solvent itself. The incremental surface tension of the control polymer increases with the percentage of ethanol in the solvent. This is expected since the HEC is highly water-soluble. More interesting, however, is the result from the HMHEC solution. A minimum is found in the Incremental surface tension at 50% (v/v) (44% w/w) ethanol, identifying this composition as the "best" EtOH/water solvent for this polymer at room temperature. Note that this optimum solvent composition does not depend on the total polymer content of the solution, since the solution has been optimized with respect to polymer/solvent interactions. Hence 50% (v/v) ethanol/water was used as the solvent for all HMHEC solutions. 

There appear to be at least two zinc chloride complexes of pyridine, one of m.p. 207 and composition 2CsH,N,ZnCh, sind the other of m.p. 152° and probable composition 2C,H,N,ZnClt,HCl. The former is slightly soluble in water and in hot ethyl alcohol the latter passes into the former in aqueous solution, is readily soluble in hot absolute ethanol and can therefore be readily recrystaUised from this solvent. 

Poly(Vinylpyrrolidinone-CO Vinyl Acetate). The first commercially successful class of VP copolymers, poly(vinylpyrroHdinone-co-vinyl acetate) is currently manufactured in sizeable quantities by both ISP and BASF. A wide variety of compositions and molecular weights are available as powders or as solutions in ethanol, isopropanol, or water (if soluble). Properties of some examples of this class of copolymers are Hsted in Table 15. 

Sample Preparation. Liquid crystalline phases, i.e. cubic and lamellar phases, were prepared by weighing the components in stoppered test tubes or into glass ampoules (which were flame-sealed). Water soluble substances were added to the system as water solutions. The hydrophobic substances were dissolved in ethanol together with MO, and the ethanol was then removed under reduced pressure. The mixing of water and MO solutions were made at about 40 C, by adding the MO solution dropwise. The samples for the in vivo study were made under aseptic conditions. The tubes and ampoules were allowed to equilibrate for typically five days in the dark at room temperature. The phases formed were examined by visual inspection using crossed polarizers. The compositions for all the samples used in this work are given in Tables II and III. 

The complexity of wine composition is a central reason for the vast variety of wines in the marketplace. In addition to water and ethanol, the major components, a variety of organic acids as well as metal ions from minerals in the skin of the grape are present. Initially, all of these substances remain dissolved in the bottled grape juice. As the fermentation process occurs, the increasing alcohol concentration in the wine alters the solubility of particular combinations of acid and metal ions. Unable to remain in solution, the insoluble substances settle as crystals. Since the process of red-wine making involves extended contact of the grape juice with the skins of the grapes (where the minerals are concentrated), wine crystals are more common in red wines than in white wines. 

If a salt which is somewhat soluble in both water and ethanol is added to a binary mixture, the composition of the liquid phase is modified such that the solution can be considered to consist of a binary mixture formed by free water and ethanol with a composition richer in ethanol than the initial binary mixture... 

To test the solubility of a solid, transfer an amount roughly estimated to be about 10 mg (the amount that forms a symmetrical mound on the end of a stainless steel spatula) into a 10 x 75-mm test tube and add about 0.25 mL of solvent from a calibrated dropper or pipette. Stir with a fire-polished stirring rod (4-mm), break up any lumps, and determine if the solid is readily soluble at room temperature. If the substance is readily soluble in methanol, ethanol, acetone, or acetic acid at room temperature, add a few drops of water from a wash bottle to see if a solid precipitates. If it does, heat the mixture, adjust the composition of the solvent pair to produce a hot solution saturated at the boiling point, let the solution stand undisturbed, and note the character of the crystals that form. If the substance fails to dissolve in a given solvent at room temperature, heat the suspension and see if solution occurs. If the solvent is flammable, heat the test tube on the steam bath or in a small beaker of water kept warm on the steam bath or a hot plate. If the solid completely dissolves, it can be declared readily soluble in the hot solvent if some but not all dissolves, it is said to be moderately soluble, and further small amounts of solvent should then be added until solution is complete. When a substance has been dissolved in hot solvent, cool the solution by holding the flask under the tap and, if necessary, induce crystallization by rubbing the walls of the tube with a stirring rod to make sure that the concentration permits crystallization. Then reheat to dissolve the solid, let the solution stand undisturbed, and inspect the character of the ultimate crystals. 

A 15-stage extraction column similar to the one in Example 2.22 is set up to separate acetone and ethanol using two solvents, pure water and pure chloroform. The only added features to Fig. E2.22 in Example 2.22 are (1) that you must consider two solutes in each solvent instead of one solute in the two solvents and (2) the acetone-ethanol feed is introduced into stage 6. You know that the feed composition is 50 mol % ethanol and 50 mol % acetone and that the feed rate is 20 lb mol/hr. Assume that the water and chloroform are not soluble in each other. You want to have 1.50 mol % ethanol in the exit stream from the bottom of the column, and 2 X 10 mol % acetone in the exit stream from the top of the column. Determine the rates of flow of the two solvents. In each stage you are given a relationship between Xf and Xf (/ = 1, 2, 3) in the two phases in terms of mole fractions ... 

The alcohols, melhanol. ethanol and 1 and 2-propanol are completely miscible with water, i.e. any composition is possible between 0% and 100% of the atcohol and 100% and 0% of water. As the hydrophobic ( water repelling) hydrocarbon content increases, alcohols become progressively less soluble m water, pentadecanol dissolving only to the extent ol l tO %byrnass and would be classed as Insoluble. Mon-polar leirachlorornethane dissolves in water at 25 C to give an 8 10 mol dm solulion and hexane dissolves lo give only a 1.3- 10 mol dm solution. 

The disappearance of the solid phase in a solubility cell can be observed under isothermal conditions while adding small portions of fresh solvent to a solution-suspension of known composition. Mullin and Sipek (1982) have described one use of this technique for solubility measurements in the three-phase system potash-alum-water-ethanol. 

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