Types of Solutions

Although we think of solutions as solids (or solutes) dissolved in liquids as solvents, other phases can form solutions. Table 4.6.1 shows examples of the different types. 

Liquid Gas Fizzy drinks (t. g. carbon dioxide in water) 

Liquid Liquid Alcoholic drinks (ethanol in water) Antifreeze (ethylene glycol in water) 

Solid Solid Metal alloys such as brass (zinc in copper), 9 ct gold (gold in copper) 

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Fig. 32. Maximum flux obtained with various protein solutions as a function of protein concentration according to equation 3. Feed flow rates, cm /min = A, 3000 B, 2000 C, 1000 and D, 500. The flux decreases exponentially as the protein concentration increases. The extrapolated protein concentration at no flux is the gel point for this type of solution (approx 28%). These results were obtained in a flow-through cell and demonstrate the...

Electrowinning from Aqueous Solutions. Electrowinriing is the recovery of a metal by electrochemical reduction of one of its compounds dissolved in a suitable electrolyte. Various types of solutions can be used, but sulfuric acid and sulfate solutions are preferred because these are less corrosive than others and the reagents are fairly cheap. From an electrochemical viewpoint, the high mobiUty of the hydrogen ion leads to high conductivity and low ohmic losses, and the sulfate ion is electrochemicaHy inert under normal conditions. 

Solution Polymerization. Two types of solution polymerization technologies are used for LLDPE synthesis. One process utilizes heavy solvents the other is carried out in mixtures of supercritical ethylene and molten PE as a polymerization medium. Original solution processes were introduced for low pressure manufacture of PE resins in the late 1950s subsequent improvements of these processes gradually made them economically competitive with later, more advanced technologies. 

The second type of solution polymerization concept uses mixtures of supercritical ethylene and molten PE as the medium for ethylene polymerization. Some reactors previously used for free-radical ethylene polymerization in supercritical ethylene at high pressure (see Olefin POLYMERS,LOW DENSITY polyethylene) were converted for the catalytic synthesis of LLDPE. Both stirred and tubular autoclaves operating at 30—200 MPa (4,500—30,000 psig) and 170—350°C can also be used for this purpose. Residence times in these reactors are short, from 1 to 5 minutes. Three types of catalysts are used in these processes. The first type includes pseudo-homogeneous Ziegler catalysts. In this case, all catalyst components are introduced into a reactor as hquids or solutions but form soHd catalysts when combined in the reactor. Examples of such catalysts include titanium tetrachloride as well as its mixtures with vanadium oxytrichloride and a trialkyl aluminum compound (53,54). The second type of catalysts are soHd Ziegler catalysts (55). Both of these catalysts produce compositionaHy nonuniform LLDPE resins. Exxon Chemical Company uses a third type of catalysts, metallocene catalysts, in a similar solution process to produce uniformly branched ethylene copolymers with 1-butene and 1-hexene called Exact resins (56). 

Hydrated Stannic Oxide. Hydrated stannic oxide of variable water content is obtained by the hydrolysis of stannates. Acidification of a sodium stannate solution precipitates the hydrate as a flocculent white mass. The colloidal solution, which is obtained by washing the mass free of water-soluble ions and peptization with potassium hydroxide, is stable below 50°C and forms the basis for the patented Tin Sol process for replenishing tin in staimate tin-plating baths. A similar type of solution (Staimasol A and B) is prepared by the direct electrolysis of concentrated potassium staimate solutions (26). 

Fig. 10. Three types of solution mining mbblized (explosives or mining), hydrofracted, or chemically iaduced porosity, where A represents the oxidized B,...

Where physieal systems are so eomplex that mathematieal solutions are not possible, experimental teehniques based on various analogies may be one type of solution. Eleetrieal systems that are analogous to meehanieal systems are usually the easiest, eheapest, and fastest solution to the problem. The analogy between systems is a mathematieal one based on the similarity of the differential equations. Thomson has given an exeellent treatise on this subjeet in his book on vibration. Some of the highlights are given here. 

The author has often wondered how often machines are redesigned and rebuilt or even replaced for reasons that were later found to be incorrect. Based on observations over a considerable number of years, the number might be staggering. Ironically, the incorrect diagnosis sometimes results in a solution that will at least for the time being appear to fix the problem. This type of solution may possibly lead to a future problem because an incorrect symptom-cause relationship is established that will not hold true on another application at another time. All of this is being said to stress the need for proper and careful problem solving that accurately determines the real cause for the problem. It is difficult to address the common sense side of reliability and not make some type of... 

Figure 11. The Different Types of Solute Interaction that can Occur on a Silica Surface Containing a Solvent Bi-layer...

Scott and Kucera [4] carried out some experiments that were designed to confirm that the two types of solute/stationary phase interaction, sorption and displacement, did, in fact, occur in chromatographic systems. They dispersed about 10 g of silica gel in a solvent mixture made up of 0.35 %w/v of ethyl acetate in n-heptane. It is seen from the adsorption isotherms shown in Figure 8 that at an ethyl acetate concentration of 0.35%w/v more than 95% of the first layer of ethyl acetate has been formed on the silica gel. In addition, at this solvent composition, very little of the second layer was formed. Consequently, this concentration was chosen to ensure that if significant amounts of ethyl acetate were displaced by the solute, it would be derived from the first layer on the silica and not the less strongly held second layer. 

The solvent used was 5 %v/v ethyl acetate in n-hexane at a flow rate of 0.5 ml/min. Each solute was dissolved in the mobile phase at a concentration appropriate to its extinction coefficient. Each determination was carried out in triplicate and, if any individual measurement differed by more than 3% from either or both replicates, then further replicate samples were injected. All peaks were symmetrical (i.e., the asymmetry ratio was less than 1.1). The efficiency of each solute peak was taken as four times the square of the ratio of the retention time in seconds to the peak width in seconds measured at 0.6065 of the peak height. The diffusivities obtained for 69 different solutes are included with other physical and chromatographic properties in table 1. The diffusivity values are included here as they can be useful in many theoretical studies and there is a dearth of such data available in the literature (particularly for the type of solutes and solvents commonly used in LC separations). 

The simplest type of solutions which exhibit non-randomness are those in which the non-randomness is attributable solely to geometric factors, i.e. it does not come from non-ideal energetic effects, which are assumed equal to zero. This is the model of an athermal solution, for which... 

In order to represent the basic type of solution flowing in a line, designations or codes to assign to the lines can be developed for each process. Some typical codes are ... 

This type of evaluation of a distillation system involves a material and heat balance around each tray. It is extremely tedious to do by conventional means, and is now handled with computers. But even with this untiring worker, the volume of calculations is large and requires a relatively long time. Only those special systems that defy a reasonable and apparently economical solution by other approaches are even considered for this type of solution. 

Electropolishing which exploits a generally similar type of solution, but introduces anodic currents as an additional means of dissolution thereby providing better control of rapid processing. Electrosmoothing and electrobrightening are terms used to describe inferior finishes which may have lustre but have lower specular reflectivity. 

Aqueous solutions of non-electrolytes, especially of non-polar solutes, may show the reverse effect and increase the proportions of ice-like components. The non-polar part of organic electrolytes such as soaps and wetting agents may predominate in increasing the ice component. Thus solutes can be divided into two classes structure making and structure breaking, and in some metal-finishing process solutions both types of solute may be added. 

Review of Solutions in General. In the discussion of these various examples we have noticed at extreme dilution the prevalence of the term — In Xb, or alternatively — In yB. The origin of this common factor in many different types of solutions can be shown, as we might suspect, to be of a fundamental nature. For this purpose let us make the familiar comparison between a dilute solution and a gas. Since the nineteenth century it has been recognized that the behavior of any solute in extremely dilute solution is, in some ways, similar to that of a gas at low pressure. Now when a vessel of volume v contains n particles of a perfect gas at a lixed temperature, the value of the entropy depends on the number of particles per unit volume, n/v. In fact, when an additional number of particles is introduced into the vessel, the increment in the entropy, per particle added, is of the form... 

The fact that tantalum and niobium complexes form in fluoride solutions not only supplements fundamental data on the coordination chemistry of fluoride compounds, but also has a broad practical importance. This type of solution is widely used in the technology of tantalum and niobium compounds in raw material digestion, liquid-liquid extraction, precipitation and re-pulping of hydroxides, and in the crystallization and re-crystallization of K-salts and other complex fluoride compounds. 

A discussion of the different types of solute-solute and solute-solvent interactions acting in homogeneous catalysis by transition metal complexes. E. Cesarotti, R. Ugo and L. Kapan, Coord. Chem. Rev., 1982,43, 275-298 (47). 

Returning now to the subject of the chapter, in addition to appropriate retentive characteristics, a potential stationary phase must have other key physical characteristics before it can be considered suitable for use in LC. It is extremely important that the stationary phase is completely insoluble (or virtually so) in all solvents that are likely to be used as a mobile phase. Furthermore, it must be insensitive to changes in pH and be capable of assuming the range of interactive characteristics that are necessary for the retention of all types of solutes. In addition, the material must be available as solid particles a few microns in diameter, so that it can be packed into a column and at the same time be mechanically strong enough to sustain bed pressures of 6,000 p.s.i. or more. It is clear that the need for versatile interactive characteristics, virtually universal solvent insolubility together with other critical physical characteristics severely restricts the choice of materials suitable for LC stationary phases. 

Most acids and bases are weak. A solution of a weak acid contains the acid and water as major species, and a solution of a weak base contains the base and water as major species. Proton-transfer equilibria determine the concentrations of hydronium ions and hydroxide ions in these solutions. To determine the concentrations at equilibrium, we must apply the general equilibrium strategy to these types of solutions. 

There are many other types of solution required in a sterile form for use particularly in hospitals. 

Existing SEC retention theories have been independently developed for each of the molecular-shape models shown in Figure 1. The deep hollow cyclin-drical pore in the figure (A, B, and C) illustrates the SEC exclusion effect on three types of solute molecules, hard-sphere, rigid-rod, and random-coil, respectively. The individual theories and their bases of commonality are now reviewed briefly. 

The choice of the stationary phase depends on the type of solutes. Silica gel is usually used if there are no special requirements as far as stationary phase is concerned. 

Which of the following is the most unstable type of solution ... 

Strong acid (PK, < 2) Sulfonated dyes 2 - 7.4 These solutes are ionized throughout the pH range actual pH selected is dependent upon other types of solutes present. 

A solution is a mixture of two or more substances. The substances involved are mixed so intimately (on the atomic scale) that it is not possible to distinguish their individual properties. A solution constitutes a single phase, as distinct from heterogeneous systems which contain several phases. A solution, however, differs from a chemical compound in that its composition is not fixed but can vary over a range. It is customary to designate the major component of a solution as the solvent, and the minor ones as the solutes. A solvent as well as a solute can be a gas, a solid or a liquid. Depending upon the state of the solute and/or the solvent, several types of solutions may exist. 

Whether the pyro or the hydro-route of processing of nodules is used, it is found that -depending upon the treatment given - three types of solutions are produced, these being chloride solution, sulfate solution, and ammonia solution. Each of these solutions is entirely processible to recover the metals values held by them. 

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