Middle aqueous layer

The hydrolysis and condensation are usually fast and depend on the pH as well as on the solvent. For example, PW120 starts to decompose above pH 2 and coexists with PWnOj, and PW90 [28]. In this respect, pure PWuO should be isolated as free acid by the extraction by ether, the so-called etherate method. If a very acidic solution of the heteropolyanion is shaken with excess diethyl ether, three phases separate a top ether layer, a middle aqueous layer, and a bottom... 

Bromine (128 g., 0.80 mole) is added dropwise to the well-stirred mixture over a period of 40 minutes (Note 4). After all the bromine has been added, the molten mixture is stirred at 80-85° on a steam bath for 1 hour, or until it solidifies if that happens first (Note 5). The complex is added in portions to a well-stirred mixture of 1.3 1. of cracked ice and 100 ml. of concentrated hydrochloric acid in a 2-1. beaker (Note 6). Part of the cold aqueous layer is added to the reaction flask to decompose whatever part of the reaction mixture remains there, and the resulting mixture is added to the beaker. The dark oil that settles out is extracted from the mixture with four 150-ml. portions of ether. The extracts are combined, washed consecutively with 100 ml. of water and 100 ml. of 5% aqueous sodium bicarbonate solution, dried with anhydrous sodium sulfate, and transferred to a short-necked distillation flask. The ether is removed by distillation at atmospheric pressure, and crude 3-bromo-acetophenone is stripped from a few grams of heavy dark residue by distillation at reduced pressure. The colorless distillate is carefully fractionated in a column 20 cm. long and 1.5 cm. in diameter that is filled with Carborundum or Heli-Pak filling. 4 hc combined middle fractions of constant refractive index are taken as 3-l)romoaccto])lu iu)nc weight, 94 -100 g. (70-75%) l).p. 75 76°/0.5 mm. tif 1.57,38 1.5742 m.]). 7 8° (Notes 7 and 8). 

Figure Density distribution in the direction normal to the bilayer plane for indicated groups, z 0 corresponds to the middle of the lipid layer z 1.8 corresponds to the center of the aqueous layer.

A middle 7-pm thick aqueous layer secreted by the lacrymal glands, with an average debit of... 

The block-polymers containing a middle block of polystyrene and two blocks of polyethylene oxide have some unusual properties. They are soluble in methyl ethyl ketone and cannot be precipitated from this solvent by methanol. Addition of water produces a slight cloudiness but still no precipitation although the block polymer is not soluble in pure water. The polymer is also soluble in benzene, but addition of water to this solution causes its precipitation. On the other hand, neither homopolystyrene nor homo-polyethylene oxide or their mixtures are precipitated from benzene solution by addition of water. This strange behaviour is explained by Richards and Szwarc (45) in terms of hydrogen bonding which depends on the chemical potential of water in the aqueous layer and therefore also in the benzene solution. 

The mixture of the product of hydrolytic cocondensation (silanol) and water from the bottom part of the hydrolyser continuously enters the middle part of separator 10, where silanol and water separate. The aqueous layer from the separator is analysed (to determine its acidity). Silanol from the top part of the separator is continuously sent into the middle part of flusher 12. There is hydroejector 11 in this direction, which is filled with water from heater 7 for washing silanol. The quantity of water sent to flushing can vary depending on pH of silanol. 

For the 1 M NaCl system the solubility region was further reduced. Fig. 13, and the water solubilization maximum found at even higher surfactant/cosurfactant ratio. The series with the lower ratios of surfactant to cosurfactant showed an uptake of the aqueous solution somewhat similar to the series in the system with 0.5 M NaCl. The series with the surfactant/(cosurfactant + surfactant) ratio equal to 0.4 gave an initial liquid crystal formation lasting for 2-3 days folllowed by a middle phase lasting a longer time. The liquid crystalline and the middle phase layer were both more pronounced for the sample with initial salt concentration equal in the water and in the microemulsion. Fig. 14A, than for the sample with all the salt in the water. Fig. 14B. 

Figure 5. Time-resolved fluorescence of pyranine at the wavelength of maximum

Iodine (0.5 g) is added to diacetone alcohol (700 g), and the mixture is distilled through a small column. After about two-thirds have distilled, the remaining one-third of the distillate of b.p. 125-130° (pure mesityl oxide) is collected separately. The first two-thirds form two layers, of which the lower, aqueous phase is discarded. The upper layer is dried over calcium chloride and fractionated, affording an acetone fraction (b.p. 60-80°), a middle fraction (b.p. 80-125°), and a mesityl oxide fraction (b.p. 126-130°). Saturating the aqueous layer with potassium carbonate affords a further small amount (11 g) of an oil that consists of equal parts of acetone and mesityl oxide. The total yield of crude mesityl oxide is 578 g (97.8%). According to Conant and Tuttle,41 0.1 g of iodine suffices for 1100 g of crude diacetone alcohol. 

Cold saturated KaFe(CN)6 solution (40 ml.) is treated slowly and in the cold with 40 ml. of fuming HCl the mixture is allowed to stand in an ice bath with frequent agitation for about half an hour. The KCl precipitate is removed by filtration and the filtrate is shaken with 70 ml. of ether. Three layers are formed aqueous, oily and ethereal. After draining the aqueous layer, the middle, oily layer is allowed to clarify. It is then separated from the ether layer and the oil is completely freed of ether under vacuum. This results in crystallization of a yellow etherate of H3Fe(CN)6 finally, however, pure H3Fe(CN)6 remains as a brown mass. The acid may be recrystallized by solution in absolute ethanol and evaporation of the solvent. The compound must not be allowed to contact metal or rubber and should be kept as dry as possible. 

In the water in oil in water (w/o/w) double emulsions, the internal and external aqueous phases are separated by an oil layer. For their formation and stability, at least two surfactants, one having a low HLB to form the primary water in oil (w/o) emulsion and the other having a higher HLB to achieve secondary emulsification, are required to emulsify water in oil emulsion into water. These anulsion (w/o/w) systems, being less viscous, are excellent candidates for controlled release of hydrophilic drags dne to the existence of a middle oil layer that acts as a liquid membrane. 

In this context, it should be noted that the tar acids, which are mostly phenol, cresols, and xyle-nols, can be recovered by mixing the crude middle oils with a dilute solution of caustic soda, separating the aqueous layer, and passing steam through it to remove residual hydrocarbons. The acids are then recovered by treatment of the aqueous extract with carbon dioxide or with dilute sulfuric acid and are then fractionated by distillation in vacuo. 

Detailed analyses of the temperature dependence of X-ray diffraction patterns of alkali stearate salts in water have allowed rather complex phase diagrams to be constructed [63]. An example involving potassium stearate (KS), based on samples cooled from 373 K but not annealed at subambient temperatures, is shown in Figure 1.7. The lowest temperature dotted line represents the separation between the coagel phase (solid soap particles (C) dispersed in water (E)) and tempera-tures/compositions at which various gel phases (G) can exist or coexist with a solid. Between 303 and c. 316K and at 30 wt% of KS, a stable transparent gel (G) is observed. The L (neat) phase consists of bilayer sheets (lamellae) of KS molecules whose alkyl chains are melted and separated by aqueous layers whose average thickness depends upon the phase composition. The M (middle) phase is composed of... 

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