Liquid ciystal solution

The solution viscosity y5 concentration plots do not exhiUt a maximum in contrast to ical polymer liquid ciystal solutions. As noted in the introduction, this same behavior is exhibited by other cellulose-solvent systems (.9,14) and, as discussed in the introduction, suggests the mesophase is metastable. 

As stated in Secs. 1-7 and 1-8, it is possible, by using group theory, to classify the normal vibration into various symmetry species. Experimentally, measurements of the infrared dichroism and polarization properties of Raman lines of an orientated ciystal provide valuable information about the symmetry of normal vibrations (Sec. 1-23). Here we consider the polarization properties of Raman lines in liquids and solutions in which molecules or ions take completely random orientations. ... 

Phospholipids. For the removal of ionic contaminants from raw zwitterionic phosphoUpids, most Upids are purified twice by mixed-bed ionic exchange resins (Amberlite AB-2) of methanoUc solutions. (About Ig of lipid in 10ml of MeOH). With both runs the first 1ml of the eluate is discarded. The main fraction of the solution is evaporated at 40 C under dry N2 and reciystallised three times from n-pentane. The resulting white powder is dried for about 4 hours at 50 under reduced pressure and stored at 3 . Some samples are purified by mixed-bed ion exchange of aqueous suspensions of the ciystal/liquid ciystal phase. [Kaatze et al. J Phys Chem 89 2565 1985.]... 

Miscibility is identified as an existence of a single phase thus, the term refers to liquid systems solutions and melts (some authors treat co-ciystallization as a solid-state miscibility). Most polymer blends available oti the market are immiscible, but with adequate interactions across the interphase. For example, by 1980 ca. 42 % film producers used immiscible LLDPE/LDPE blends, where LLDPE improved modulus and strength and LDPE enhanced processability and ductility. Properties of LLDPE/LDPE blends have been described in several publications (Utracki and Schlund 1986,1987 Schlund and Utracki 1987 Zahavich and Vlachopoulos 1997). Blends of LLDPE with PP were also studied (Dumouhn et al. 1987, 1988, 1991 Dumoulin and Utracki 1990). Similarly, blends of PE with PC were described (Utracki and Sammut 1989, 1990b). 

Salt Brines The typical curve of freezing point is shown in Fig. II-IIO. Brine of concentration x (water concentration is I-x) will not solidify at 0°C (freezing temperature for water, point A). When the temperature drops to B, the first ciystal of ice is formed. As the temperature decreases to C, ice ciystals continue to form and their mixture with the brine solution forms the slush. At the point C there will be part ice in the mixture /(/i+L), and liquid (brine) /i/(/i-t-L). At point D there is mixture of mi parts eutectic brine solution Di [concentration mi/(mi-t-mg)], and mo parts of ice [concentration mol m -t- mo)]. Coohng the mixture below D solidifies the entire solution at the eutectic temperature. Eutectic temperature is the lowest temperature that can be reached with no solidification. 

Highest heat-transfer coefficients are obtained in FC evaporators when the liquid is aUowed to boil in the tubes, as in the type shown in Fig. 11-122 7. The heating element projects into the vapor head, and the hquid level is maintained near and usuaUy slightly below the top tube sheet. This type of FC evaporator is not well suited to salting solutions because boiling in the tubes increases the chances of salt deposit on the waUs and the sudden flashing at the tube exits promotes excessive nucleation and production of fine ciystals. Consequently, this type of evaporator is seldom used except when there are headroom hmitations or when the hquid forms neither salt nor scale. 

Purification of a chemical species by solidification from a liquid mixture can be termed either solution crystallization or ciystallization from the melt. The distinction between these two operations is somewhat subtle. The term melt crystallization has been defined as the separation of components of a binaiy mixture without addition of solvent, but this definition is somewhat restrictive. In solution crystallization a diluent solvent is added to the mixture the solution is then directly or indirec tly cooled, and/or solvent is evaporated to effect ciystallization. The solid phase is formed and maintained somewhat below its pure-component freezing-point temperature. In melt ciystallization no diluent solvent is added to the reaction mixture, and the solid phase is formed by cooling of the melt. Product is frequently maintained near or above its pure-component freezing point in the refining sec tion of the apparatus. 

CiystaUization is the preferred method of forming many final prod-uc ts because veiy high purification is possible. High purity antibiotic ciystals can be produced from colored, rather impure solutions if the filter cake is uniform and amenable to good washingto remove the mother hquor. When a sterile pharmaceutical produc t is desired, ciystals are formed from liquid streams that have been sterihzed by filtration. 

Reaction.—Make a solution of 4 grams stannous chloride in TO c.c. cone, hydrochloric acid, add 2 grams aminoazobenzene, and boil for a few minutes. On cooling ciystals of the hydrochlorides of aniline and yi-phenylenediamine separate out. The liquid is filtered and washed with a little cone, hydrochloric acid to remove the tin salts. If the precipitate is dissolved in water and made alkaline with caustic soda, a mixture of liquid aniline and solid/-phenylenediamine is precipitated, from which the former may be removed by filtering, washing, and draining on a porous plate. 

In systems where the liquid phase interaction between the solute and solvent is close to ideal, then Eq. 2 can be used successfully on it s own to fit and extrapolate solubility data with respect to temperature. The technique is valuable in an industrial setting, where time pressures are always present. Solubility data points are often available without any additional effort, from initial work on the process chemistiy. The relative volume of solvent that is required to dissolve a solute at the highest process temperature in the ciystallization is often known, together with the low temperature solubility by analysis of the filtrates. If these data points fit reasonably well to the ideal solubility equation then it can be used to extrapolate the data and predict the available crystallization yield and productivity. This quickly identifies if the process will be acceptable for long term manufacture, and if further solvent selection is necessary. 

Interactions between solute and solvent molecules can have a significant effect on the shape of a crystal. This can be accounted for by specific adsorption of the solvent molecule on ciystal faces. Current oystal growth theories indicate that when interactions between solute and solvent are strong the solute molecules are solvated and a solvation layer dsts at the oystal-liquid interface which likely can vary as a function of ciystal face. Crystal growth requires desolvation of die solute molecule and desolvation of the surface site on the crystal. The molecule then surface diffuses imtil it reaches an incorporation (kink) site. 

Test for the Presence of Blood. Gunning has discovered in acetate of zinc a rea ut that precipitates the slightest traces of tee coloring matter of blood from solutions, even where the liquids are so dilate as to be colorless. Blood washed from the hands in a pail of water can readily be detected in this way. The flocculent precipitate thrown down by acetate of zinc must be washed by decantation, and Anally collected on a watch-glass, and allowed to dry, when the microscope will readily reveal ciystals if any blood bo present. (See Ab. 6415.)... 

In ciysiallization, nuciention is the formation of a solid phase from a liquid phase. The process differs from growth in that a naw ciystal results from the transfer of solute from the liquid to (he solid in growth, solid is deposited on an existing ciystal. Because it is the phenomenon of crystal formation, nucleation sets the cheracter of the ciystailization process, and it is tharefore the most critical component in relating ciystallizer desiga and operation to ciystal size distribution . 

Re = mass of dissolved solute in liquid discharged from the ciystallizer per unit mass of discharged solvent... 

In solution crystallization product purity is controlled to a great extent by the efficiency of solid-liquid separation. Impurities dissolved in the ciystallizer liquid are normally removed by spinning liquor from the crystals and then washing the resulting cake. The residual impurity level is a function of factors listed in the following equation ... 

SHI Shang, M., Matsuyama, H., Maki, T., Teramoto, M., and Lloyd, D.R., Effect of ciystallization and hquid-liquid phase separation on phase-separation kinetics in poly(ethylene-co-vinyl alcohol)/glycerol solution, J. Polym. Sci. Part B Polym. Phys., 41, 184, 2003. 

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