Solutions and concentration

However, for more complex fluids such as high-polymer solutions and concentrated ionic solutions, where the range of intemiolecular forces is much longer than that for simple fluids and Nq is much smaller, mean-field behaviour is observed much closer to the critical point. Thus the crossover is sharper, and it can also be nonmonotonic. 

SO, + 2H,0 + Br, — HjSO, + 2HBr Alternatively, the acid mixture may be obtained from the reaction between potassium bromide solution and concentrated sulphuric acid below 76° the potassium hydrogen sulphate crystallises out and is removed by filtration ... 

Boil the crude coumarin with 200 ml. of water to which 0 -2 g. of decolourising carbon is added, filter the hot solution, and concentrate it to a volume of 80 ml. Cool, collect the coumarin which separates, and recrystallise it from 40 per cent, aqueous methanol. The yield of coumarin, m.p. 68-69°, is 1 0 g. 

Preparation of 4-aza-5-(N-methyi-4-piperidyiidene)-10,11-dihydro-5H-dibenzo[a,d]cyciohep-tene Heat 5.4 g of the carbinol and 270 g of polyphosphoric acid for 12 hours at 140°-170°C. Pour into ice water and make alkaline with sodium hydroxide. Extract with ether. Dry ether solution and concentrate to a residue. Crystallize from isopropyl ether, MP 124°-126 C. 

The thus-obtained residue was dissolved in a mixture of 268 ml of methanol and 26.8 ml of 3N aqueous sulfuric acid and heated under reflux for 40 minutes, with a color change from yellow to green. The reaction mixture was then cooled, neutralized by addition of 127 ml of 5% sodium bicarbonate solution, and concentrated under reduced pressure until almost all the methanol was removed. The resulting solid was removed by filtration, washed with water, dried, and twice crystallized from ethyl acetate to give 1.1 g of 11/3-hydroxy-Ba-methylprogesterone having a MP of 155° to 158°C, according to U.S. Patent 2,864,837. 

Ethyl cinnamate[7] To 2.96 g (20.0 mmol) of cinnamic acid in 25 mL of anhydrous THF 3.24 g (20.0 mmol) of CDI was added. When C02 evolution had ceased, 5 mL of ethanol was added and the mixture was refluxed for 30 min. After concentration in a rotary evaporator the residue was taken up in 100 mL of diethylether and extracted three times each with 50 mL of water. After drying of the ethereal solution and concentration in vacuo the residue was distilled to give ethyl cinnamate (b.p. 145-147 °C/17 mm) in 80% yield. 

The subsequent text will be restricted to aqueous solutions and concentrations will be used instead of activities. Thus, the neutral point is given by the condition [H20+] = [OH ] = K J12,... 

An evaporator is a device that eliminates excess solvent from a liquid solution and concentrates the solutes by vaporizing a portion or all of the solvent. The modern way to accomplish this is by using a stream of inert gas blowing over the surface of the solution while applying gentle heat. 

Desoxycholic Acid, Fatty Acids, Cholesterol.—The first alcoholic filtrate obtained during the crystallisation of the cholic acid (see above) is made strongly alkaline to phenolphthalein paper with 2 N-sodium hydroxide solution and concentrated to a syrupy consistency in a porcelain basin on the water bath. The syrup is taken up in 250 c.c. of water, transferred to a separating funnel, cooled, covered... 

A 1-L, oven-dried, round-bottomed flask equipped with a magnetic stirrer is charged with 9.92 g (27.9 mmol) of methyl R)-3-(tert-butyldiphenylsilyloxy)-2-methylpropionate and 200 mL of dry hexanes (Note 15). The solution is cooled to -78°C, and 31.5 mL (31.5 mmol) of 1 M diisobutylaluminum hydride (in hexane) (DIBAL-H) (Note 16) is added dropwise over 15 min via a syringe pump. After the addition is complete, the resultant solution is stirred at -78°C for 2 hr. The reaction is quenched by pouring the cold solution info 250 mL of saturated aqueous Rochelle s salt. Ether (300 mL) and HjO (75 mL) are added and the biphasic mixture is stirred vigorously for 1 hr (Note 17). The layers are separated and the ether layer is washed with brine. The aqueous layer is extracted with ether (2 x 50 mL) and the combined extracts are dried over Na2S04. Filtration of the solution and concentration of the filtrate under reduced pressure followed by purification of the crude product by flash chromatography (Note 18) yields 7.85 g (86%) of (R)-3-(tert-bUtyldiphenylsilyloxy)-2-methylpropanal as a white solid (Note 19). 

White granular powder or cubic crystals refractive index 2.071 darkens on exposure to hght density 5.56 g/cm Moh s hardness 2.5 melts at 455°C vaporizes at 1,547°C vapor pressure 1 and 5 torr at 912 and 1,019°C insoluble in water, alcohol and dilute acids soluble in ammonia solution and concentrated sulfuric acid, alkali cyanide, ammonium carbonate also soluble in potassium bromide and sodium thiosulfate solutions. 

Figure 3-36 The dependence of interdiffusivity on composition for two models (Equations 3-137c versus 3-138b) for ideal solutions and concentration-independent T>a and X>b- The solid curve is for interdiffusion of two ions of identical charge. The dashed curve is for interdiffusion of neutral atomic species such as in an alloy.

Table 10.1 Odour quality, odour threshold value in water and/or ethanol solution, and concentration range of single volatile compounds in distilled spirits produced during alcoholic fermentation from carbohydrates by yeasts and other microorganisms ...

The freezing point of an aqueous solution is governed by the concentration of solutes in the solution. The relationship between the freezing point of a simple aqueous solution and concentration of solute is described by a relation based on Raoult s law ... 

Buma (1980) reported viscosities for concentrated lactose solutions and concentrated cheese whey in the range of 10 to 40% total solids at temperatures of 20° to 60°C. A 40% lactose solution was considerably more viscous than a corresponding sucrose solution. The viscosity of the whey concentrate was much higher than that of the lactose however, whey viscosity is also influenced by composition and heat treatment. 

A satisfactory description of the state of solution is therefore only obtained in the case of a thermodynamically good solvent by taking five distinct states of solution into consideration, namely ideally-dilute particle solutions, semi-dilute particle solutions, semi-dilute network solution, concentrated particle solution, and concentrated network solution (Fig. 27). 

Block copolymers are widely used industrially. In the solid and rubbery states they are used as thermoplastic elastomers, with applications such as impact modification, compatibilization and pressure-sensitive adhesion. In solution, their surfactant properties are exploited in foams, oil additives, solubilizers, thickeners and dispersion agents to name a few. Particularly useful reviews of applications of block copolymers in the solid state are contained in the two books edited by Goodman (1982,1985) and the review article by Riess etal. (1985). The applications of block copolymers in solution have been summarized by Schmolka (1991) and Nace (1996). This book is concerned with the physics underlying the practical applications of block copolymers. Both structural and dynamical properties are considered for melts, solids, dilute solutions and concentrated solutions. The book is organized such that each of these states is considered in a separate chapter. 

A technique for the determination of methylmercury in aqueous samples (natural and seawater) involved the conversion of methylmercury to gaseous methyl-ethylmercury by reaction with sodium tetraethylborate (Bloom, 1989 Bloom and Watras, 1989). The volatile derivative was purged from the solution and concentrated on a graphitic column at room temperature. The derivative was thermally desorbed from the column, and then analysed by cryogenic gas chromatography with cold vapour atomic fluorescence detection. In addition to methylmercury, labile Hg11 species could be determined (as diethylmercury) as well as dimethylmercury (which is not ethylated). The detection limit for... 

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