Liquid initial solution

The physical process of Hquid—Hquid extraction separates a dissolved component from its solvent by transfer to a second solvent, immiscible with the first but having a higher affinity for the transferred component. The latter is sometimes called the consolute component. Liquid—Hquid extraction can purify a consolute component with respect to dissolved components which are not soluble in the second solvent, and often the extract solution contains a higher concentration of the consolute component than the initial solution. In the process of fractional extraction, two or more consolute components can be extracted and also separated if these have different distribution ratios between the two solvents. 

A second general reaction that proceeds by an SrnI mechanistic pattern involves aryl halides. Aryl halides undergo substitution by eertain nueleophiles by a ehain mechanism of the SrnI class.Many of the reactions are initiated photochemically, and most have been conducted in liquid ammonia solution. 

Another point is related to the high acidity level of the final solution, which leads to certain limitations in the subsequent technological steps. Specifically, the high acidity of the initial solution eliminates any possibility for selective extraction, i.e. sequential separation of tantalum and then of niobium. Due to the high concentration of acids, only collective extraction (of tantalum and niobium together) can be performed, at least at the first step. In addition, extraction from a highly acidic solution might cause additional contamination of the final products with antimony and other related impurities. In order to reduce the level of contaminants in the initial solution, some special additives are applied prior to the liquid-liquid extraction. For instance, some mineral acids and base metals are added to the solution at certain temperatures to cause the precipitation of antimony [455 - 457]. 

Two main schemes exist for the separation and purification of tantalum and niobium using liquid-liquid extraction. The first is based on the collective extraction of tantalum and niobium from an initial solution into an organic phase so as to separate them from impurities that remain in the aqueous media, the raffinate. The separation of tantalum and niobium is subsequently performed by fractional stripping into two different aqueous solutions. In this case, stripping of niobium is performed using relatively weak acids prior to the stripping of tantalum. Fig. 125 presents a flow chart of the process. 

Details of the tantalum and niobium extraction process depend on the type of raw material used, decomposition method, initial solution composition, extractant type, equipment specifications, type of final products and desired purity. Therefore, process parameters are usually defined individually for each specific case. This may be the reason for the existence of the wide variety of publications devoted to the liquid-liquid extraction of tantalum and niobium. Nevertheless, some common features of the process should be emphasized. 

Baviere et al. [41] determined the adsorption of C18 AOS onto kaolinite by agitating tubes containing 2 g of kaolinite per 10 g of surfactant solution for 4 h in a thermostat. Solids were separated from the liquid phase by centrifugation and the supernatant liquid titrated for sulfonate. The amount of AOS adsorbed is the difference between initial solution concentration and supernatant solution concentration at equilibrium. 

The solution of this equation has been discussed by DANCKWERTSt28), and here a solution will be obtained using the Laplace transform method for a semi-infinite liquid initially free of solute. On the assumption that the liquid is in contact with pure solute gas, the concentration Cm at the liquid interface will be constant and equal to the saturation value. The boundary conditions will be those applicable to the penetration theory, that is ... 

State the assumptions made in the penetration theory for the absorption of a pure gas inlo a liquid. The surface of an initially solute-free liquid is suddenly exposed to a soluble gas and the liquid is sufficiently deep for no solute to have time to reach the bottom of the liquid. Starting with Hick s second law ol diffusion obtain an expression for (i) the concentration, and (ii) the muss transfer rate at a time t and a depth v below the surface. 

These equations can be solved simultaneously, using the boundary conditions that at z = 0, Cf = CQ and Cd — 0, where Ca is the initial dye concentration introduced into the liquid. The solutions are... 

Fig. 29 The observed strength as a function of the initial modulus of filaments taken from a single yarn of cellulose II spun from a liquid crystalline solution compared with the calculated curves [26]...

Such a chemical approach which links ionic conductivity with thermodynamic characteristics of the dissociating species was initially proposed by Ravaine and Souquet (1977). Since it simply extends to glasses the theory of electrolytic dissociation proposed a century ago by Arrhenius for liquid ionic solutions, this approach is currently called the weak electrolyte theory. The weak electrolyte approach allows, for a glass in which the ionic conductivity is mainly dominated by an MY salt, a simple relationship between the cationic conductivity a+, the electrical mobility u+ of the charge carrier, the dissociation constant and the thermodynamic activity of the salt with a partial molar free energy AG y with respect to an arbitrary reference state ... 

Immediately mix 1 part of the 20 mg/mL initial solution with 1 part of either Mylanta Double Strength Liquid, Extra Strength Maalox Plus Suspension, or Maalox TC Suspension for a final dispensing concentration of 10 mg/mL. For patient home use, dispense the admixture in flint-glass or plastic bottles with child-resistant closures. This admixture is stable for 30 days under refrigeration at 2° to 8°C (36° to 46°F). 

The bis(2-ethylhexyl) sodium sulfosuccinate system was initially investigated because its structure of liquid crystalline solution phases and mechanism of solubilization with water had been reported by Rogers and Winsor (10). In our studies, we substituted methanol for water. Table I lists critical micelle concentrations for bis(2-ethylhexyl) sodium sulfosuccinate, triethylammonium linoleate and tetradecyldimethylammonium linoleate in methanol and 2-octanol at 25°C. Literature references for critical micelle concentrations in methanol are sparse, and it has even been suggested that in polar solvents such as ethanol, either micellization does not occur or, if it does, only to a small degree (4). The data of Table I show that micellization occurs in methanol at low concentrations. 

Some field measurements of HN03 suggest that the formation of liquid or solid Type I PSCs depends on the initial background sulfate aerosols on which the PSCs form. If they are liquid, then liquid ternary solution PSCs tend to form first as the temperature drops below 192 K, whereas if the sulfate particles are initially solids, solid Type lc PSCs may be generated (Santee et al., 1998). 

Leonard Katzin I want to make two comments, one on this last point in relation to the point that Dr. Margerum made about substituents. Chromium (I II) in the hexahyd rated state is quite resistant to penetration of the coordination shell by nitrate ion. Yet if one takes the% violet chromium nitrate hexahydrate in solid state and treats it with liquid tributylphosphate, within a matter of minutes one gets chromium compound in solution by the mechanism of substituting tributylphosphate for water. So this reaction is fast. This initial solution is violet Within the space of an hour or two it is green. And we have had for some years now infrared evidence that this color change is accompanied by penetration of the nitrate ion into the coordination sphere (4). So this again is a matter of the substituent s changing the relationship of the water. 

Filling of gas chromatography capillary column with ionic liquid monomer/initiator solution... 

The need to reliably describe liquid systems for practical purposes as condensed matter with high mobility at a given finite temperature initiated attempts, therefore, to make use of statistical mechanical procedures in combination with molecular models taking into account structure and reactivity of all species present in a liquid and a solution, respectively. The two approaches to such a description, namely Monte Carlo (MC) simulations and molecular dynamics (MD), are still the basis for all common theoretical methods to deal with liquid systems. While MC simulations can provide mainly structural and thermodynamical data, MD simulations give also access to time-dependent processes, such as reaction dynamics and vibrational spectra, thus supplying — connected with a higher computational effort — much more insight into the properties of liquids and solutions. 

One of the most interesting processes in electrically initiated polymerization was an initiation with the solvated electron proposed by Laurin and Parravano (22), who studied electro-anionic polymerization of 4-vinylpyridine in liquid ammonia solution of alkali metal salts in the temperature range — 33 to — 78° C. Rapid and efficient polymerization occurred and conversions of monomer to polymers formed exclusively at the cathode in the form of an orange-red, porous, solid deposit, suggesting the formation of a pile of living polymers. 

Here ArX is the halothiophene and ArY the product. The nature of the initiation and termination steps is not known. Thus irradiation of 3-bromothiophene in liquid ammonia in presence of potassium acetone enolate gives the monothienylation product (492 51%) and the dithienylation product (493 25%). Instead of employing photostimulation, the reaction can be brought about in lower yields by dissolving sodium or potassium metal in the liquid ammonia solution. Here the corresponding alcohol is a side product. 

An interesting class of exact self-similar solutions (H2) can be deduced for the case where the newly formed phase density is a function of temperature only. The method involves a transformation to Lagrangian coordinates, based upon the principle of conservation of mass within the new phase. A similarity variable akin to that employed by Zener (Z2) is then introduced which immobilizes the moving boundary in the transformed space. A particular case which has been studied in detail is that of a column of liquid, initially at the saturation temperature T , in contact with a flat, horizontal plate whose temperature is suddenly increased to a large value, Tw T . Suppose that the density of nucleation sites is so great that individual bubbles coalesce immediately upon formation into a continuous vapor film of uniform thickness, which increases with time. Eventually the liquid-vapor interface becomes severely distorted, in part due to Taylor instability but the vapor film growth, before such effects become important, can be treated as a one-dimensional problem. This problem is closely related to reactor safety problems associated with fast power transients. The assumptions made are ... 

Physical Equilibria and Solvent Selection. In nrder lor two separale liquid phases to exist in equilibrium, there must be a considerable degree of thermodynamically nonideal behavior. If the Gibbs free energy. G. nf a mixture of two solutions exceeds the energies of the initial solutions, mixing does not occur and the system remains in iwo phases. For the binary system containing only components A and B. the condition for the formation of two phases is... 

Many ccllulosic derivatives form anisotropic, i.e.. liquid crystalline, solutions, and cellulose acetate and triacetate are no exception. Various cellulose acetate anisotropic solutions have been made using a variety ol solvents. The nature of Ihe polymer -solvent interaction determines the concentration at which liquid crystalline behavior is initiated. The better the interaction, the lower the concentration needed to form the anisotropic, birclringenl polymer solution. Strong organic acids, eg, trifluoroac etic acid, are most effective and can produce an anisotropic phase with concentrations as low as... 

Another interesting example belonging to the same general principle was described by Graham (56). On one hand he prepared an amine terminated polystyrene (sodium amide initiation in liquid ammonia) and showed that it contained only one terminal primary amine group per polymer chain. On the other hand copolymers were prepared by free-radical initiated solution copolymerization of small amounts of /S-iso-cyanatoethyl methacrylate with several other monomers as methyl, butyl and lauryl methacrylates, acrylonitrile and styrene. 

The thermoplastic-rich phase may be separated in the course of polymerization (Sec. 13.4.2) or can be incorporated as a dispersed powder in the initial formulation (Sec. 13.4.3). A strong drawback of the in situ-phase separation for processing purposes is the high viscosity of the initial solution which results from the much higher average molar mass of the TP compared with the liquid rubbers. Also, for the same reason, the critical concentration crit has a smaller value (phase inversion is observed at smaller concentrations of modifier). 

Grafting Method. The initiator solutions of Mn ions were prepared from aqueous base solutions of MnSO, KMnO, Na PjO- and SO,. The concentrations of chemicals in the reaction vessel (total liquid Volume 500 ml) were 2.0 mmole/1 Mi (in most cases), 2.0, 4.0 or 6.0 mmole/1 Na O, and 80 mmole/1 I SO (which gives pH 1.7). The Mn + ions are stable in aqueous solution as pyrophosphate ion complex. 

A more realistic situation for diffusion in a laminate is illustrated in Fig. 7-14b, which shows the solute concentration profile in the barrier layer after a short contact time t=tj. In this illustration the concentration profile of the solute just reaches the polymer/liquid interface and cL.t = 0. If we now consider a similar case with a semi-infinite polymer system with the initial solute concentration (cP>e) at the distance x < xQ = a+b/2 and cP=0 at x>x0 and t=0 (Fig.7-14c), then the possible concentration profiles for the three different times, tctj, t=t, and t>tj can be illustrated in Fig. 7-14d. If we assume a mass transfer through the interface A at x=x at t=t, in Fig. 7-14d, then mpt/A = 0.5cpepp(d-X ), which corresponds to mP, /A= cPepp(x0-a) = cPeppb/2 in Fig. 7-14c. If we combine this result with Eq. (7-54) for t=t, then we obtain the time... 

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