Water mixtures

The simplest way to dehydrate or de-oil an oil water mixture is to use settlingor skimming tanks respectively. Over time the relative density differences will separate the two liquids. Unfortunately this process takes time and space, both of which are often a constraint in... 

We have considered the surface tension behavior of several types of systems, and now it is desirable to discuss in slightly more detail the very important case of aqueous mixtures. If the surface tensions of the separate pure liquids differ appreciably, as in the case of alcohol-water mixtures, then the addition of small amounts of the second component generally results in a marked decrease in surface tension from that of the pure water. The case of ethanol and water is shown in Fig. III-9c. As seen in Section III-5, this effect may be accounted for in terms of selective adsorption of the alcohol at the interface. Dilute aqueous solutions of organic substances can be treated with a semiempirical equation attributed to von Szyszkowski [89,90]... 

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

Estimate the interfacial tension gradient formed in alcohol-water mixtures as a function of alcohol content. Determine the minimum alcohol content necessary to form wine tears on a vertical glass wall [174] (experimental veriflcation is possible). 

The speed of wetting has been measured by running a tape of material that is wetted either downward through the liquid-air interface, or upward through the interface. For a polyester tape and a glycerol-water mixture, a wetting speed of about 20 cm/sec and a dewetting speed of about 0.6 cm/sec has been reported [37]. Conversely, the time of rupture of thin films can be important (see Ref. 38). 

Raduge C, Pfiumio V and Shen Y R 1997 Surface vibrational spectroscopy of sulfuric acid-water mixtures at the liquid-vapor interface Chem. Phys. Lett. 274 140... 

Venables D S and Schmuttenmaer C A 1998 Far-infrared spectra and associated dynamics in acetonitrile-water mixtures measured with femtosecond THz pulse spectroscopy J. Ohem. Rhys. 108 4935-44... 

Since the amphiphilic nature is essential for the phase behaviour, systems of small molecules (e.g., lipid water mixtures) and polymeric systems (e.g., homopolymer copolymer blends) share many connnon features. 

Filter the crystals at the pump, wash them with water, and drain well. To save time, the product may be recrystallised directly from an ethanol-water mixture (1 2 by vol.), and obtained as colourless crystals, m.p. 68°. Alternatively, the crude product can be dried in a desiccator (yield of dry product, I-9-2 0 g., m.p. 65-67°) and recrystallised from petroleum (b.p. 60-80°), and obtained as needles, m.p. 68°. 

Add 40 ml. of ethyl alcohol to 21 -5 g. of 70 per cent, ethylenediamine solution (0 -25 mol) dissolve 36 -5 g. of adipic acid (0 -25 mol) in 50 ml. of a 6 1 mixture of ethyl alcohol and water. Mix the two solutions, stir and cool. Filter off the resulting salt and recrystalliae it from 60 ml. of a 6 1 ethyl alcohol - water mixture, and dry the salt in the air. Heat the salt in an atmosphere of oxygen-free nitrogen or of carbon dioxide in an oil bath until it melts (ca. 160°) the product will sohdify after a short time. Reduce the pressure to 15 mm. of mercury or less and raise the temperature of the oil bath until the product remelts (about 290°) and continue the heating for 4r-5 hours. Upon coohng, a nylon type polymer is obtained. 

Breslow studied the dimerisation of cyclopentadiene and the reaction between substituted maleimides and 9-(hydroxymethyl)anthracene in alcohol-water mixtures. He successfully correlated the rate constant with the solubility of the starting materials for each Diels-Alder reaction. From these relations he estimated the change in solvent accessible surface between initial state and activated complex " . Again, Breslow completely neglects hydrogen bonding interactions, but since he only studied alcohol-water mixtures, the enforced hydrophobic interactions will dominate the behaviour. Recently, also Diels-Alder reactions in dilute salt solutions in aqueous ethanol have been studied and minor rate increases have been observed Lubineau has demonstrated that addition of sugars can induce an extra acceleration of the aqueous Diels-Alder reaction . Also the effect of surfactants on Diels-Alder reactions has been studied. This topic will be extensively reviewed in Chapter 4. 

Finally, in the last step, the chelating auxiliary had to be removed Ideally, one would like to convert 4.54 into ketone 4.55 via a retro Mannich reaction. Unfortunately, repeated attempts to accomplish this failed. These attempts included refluxing in aqueous ethanol under acidic and basic conditions and refluxing in a 1 1 acetone - water mixture in the presence of excess paraformaldehyde under acidic conditions, in order to trap any liberated diamine. Tliese procedures were repeated under neutral conditions in the presence of copper(II)nitrate, but without success. 

To find the correct temperature on a thermometer reading 80°C and that shows a reading of — 0.30°C in a melting ice/water mixture and 99.0°C in steam at 760 mm pressure of mercury ... 

Freezing point of ethyl alcohol-water mixtures ... 

Acetic acid containing less than 1% water is called glacial. It is hygroscopic and the freezing point is a convenient way to determine purity (7). Water is nearly always present in far greater quantities than any other impurity. Table 1 shows the freezing points for acetic acid-water mixtures. 

Acetic acid forms a monohydrate containing about 23% water thus the density of acetic acid-water mixtures goes through a maximum between ... 

Fig. 1. The free2ing point of monochloroacetic acid (MCAA)—water mixtures. For wt % acid >75% fp(°C) = 2.17 ...

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