Soluble Constituents

Coal is usually considered to be a high-molecular-weight organic material composed of a variety of carbon systans. Indeed, many structures have been postulated for coal and all of these postulates invoke the concept of an extremely complex systan having a high molecular weight. 

Solvent extraction under mild conditions has been and continnes to be actively pursued, primarily as a tool to probe the molecular properties and structure of coal and, in some instances, for conuner-cial applications. Research shows that the effectiveness of solvents for coal extraction is influenced by coal type, rank, and petrographic composition, and by the chanical nature of the solvent. 

Whether the vitrinite in coal is a micellar complex (Van Krevelen, 1993) or three-dimensional network (Given, 1984a) ranains to be proven, and whether solvent effectiveness can be explained entirely by solubility parameter (Van Krevelen, 1965), donor-acceptor number (SzeUga and Marzec, 1983), hydrogen bonding (Larsen et al., 1985), solvent synergism (lino et al., 1985), or other associative forces (Nishioka and Larsen, 1990) is stUl open to debate. 

Though still relevant today, solvents nsed to extract coal have been classified into four groups (Oele et al., 1951). Solvents in the first category, nonspecific extraction, extract only a few percent of the coal at temperatures below about 100°C (212°F). These solvents (e.g., benzene, hexane, carbon tetrachloride, and ethanol) extract only a few percent of the coal thought to be primarily resins and waxes. In specific extraction, the coal material solubilized can typically amount to about 20% to 40% w/w at temperatures up to about 200°C (390°F). Many of these solvents are (1) nucleophilic, (2) have electron donor-acceptor properties, and (3) high internal pressure. However, it must be recognized in any such system that the efficiency of solvents in this system is closely related (even dictated) by temperature. 

The extractive chemical disintegration process can be called direct coal liquefaction. Here, solvents rich in hydroaromatic components are especially suited in extracting nearly all of the reactive coal macerals. These types of solvents actively participate chemically in bond breakage and stabilization, are consumed or structurally changed, and are normally used at temperatures considerably in excess of 300°C (570°F). On the other hand, because of the heterogeneous nature of coal it is a distinct possibility there may be/could be no clear operational or mechanistic distinction between extractive disintegration and extractive chemical disintegration processes. 

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Soybean concentrate production involves the removal of soluble carbohydrates, peptides, phytates, ash, and substances contributing undesirable flavors from defatted flakes after solvent extraction of the oil. Typical concentrate production processes include moist heat treatment to insolubilize proteins, followed by aqueous extraction of soluble constituents aqueous alcohol extraction and dilute aqueous acid extraction at pH 4.5. 

Commercial soy protein concentrates typically contain 70 to 72% cmde protein, ie, nitrogen x 6.25, dry wt basis. Soy protein isolates are prepared from desolventhed, defatted flakes. A three-stage aqueous countercurrent extraction at pH 8.5 is used to disperse proteins and dissolve water-soluble constituents. Centrifugation then removes the extracted flakes, and the protein is precipitated from the aqueous phase by acidifying with HCl at pH 4.5. 

Leaching is the removal of a soluble fraction, in the form of a solution, from an insoluble, permeable sohd phase with which it is associated. The separation usually involves selective dissolution, with or without diffusion, but in the extreme case of simple washing it consists merely of the displacement (with some mixing) of one interstitial liquid by another with which it is miscible. The soluble constituent may be solid or liquid and it may be incorporated within, chemically combined with, adsorbed upon, or held mechanically in the pore structure of the insoluble material. The insoluble sohd may be massive and porous more often it is particulate, and the particles may be openly porous, cellular with selectively permeable cell walls, or surface-activated. 

Karrer and Schmid have examined the water-soluble constituents in poppy straw after extraction of the alkaloids, and have recorded the presence of -hydroxybenzaldehyde, vanillin, -hydroxystyrene, meconin and the following acids fumaric, dZ-lactic, benzoic, -hydroxycinnamic, p-hydroxybenzoic, 2-hydroxycinchoninic, vanillic, phthalic, hemipinic and m-hemipinic, with a more highly unsaturated, carboxylic acid J, b.p. 170-570-02 mm., and three unidentified substances Fa , m.p. 271-2° Wx, m.p. 310° (dec.) and Q, m.p. 260° the two latter are free from nitrogen and contain no methoxyl. 

Comparing the undissolved essential oil with that which was dissolved in the waters, it is seen that the former is richer in esters, poorer in free menthol and total menthol, and richer in menthone than the second. In other words the relatively sparingly soluble constituents are esters and menthone, whilst menthol is particularly soluble. 

It is fairly soluble in dilute alcohol, and in about 35 parts of water. It can therefore be fairly easily separated from less soluble constituents by shaking with 5 or 10 per cent, alcohol. Apart from its actual perfume value, benzyl alcohol is of considerable value to the perfumer, since it acts as a very valuable fixative, and is, moreover, one of the best-known solvents for artificial musk. 

The need for temperature cycling should be taken into account when designing or conducting tests. The nature of the test vessel should be considered for tests in aqueous solutions at temperatures above about 60°C since soluble constituents of the test vessel material can inhibit or accelerate the corrosion process. An inhibiting effect of soluble species from glass, notably silica, on the behaviour of steel in hot water has been shown . Pure quartz or polymeric materials are often more appropriate for test vessel construction. 

Soil solution is the aqueous phase of soil. It is in the pore space of soils and includes soil water and soluble constituents, such as dissolved inorganic ions and dissolved organic solutes. Soil solution accommodates and nourishes many surface and solution reactions and soil processes, such as soil formation and decomposition of organic matter. Soil solution provides the source and a channel for movement and transport of nutrients and trace elements and regulates their bioavailability in soils to plants. Trace element uptake by organisms and transport in natural systems typically occurs through the solution phase (Traina and Laperche, 1999). 

Figure 7.2 Partial capillary gas chromatogram displaying the principal lipid solvent soluble constituents of a black tarry deposit on the surface of a Neolithic potsherd from Ergolding Fischergasse, Bavaria, Germany. The sample was trimethylsilylated prior to GC (for further details see Heron et al., 1997). Peak identities (confirmed by GC-MS analysis) 1, lupenone 2, lupeol 3, betulin 4, betulinic acid.

There is also a diffusion rate factor when polymers are exposed to any gas or liquid. Usually absorption of fluid (swelling) takes place faster than extraction of soluble constituents of the polymer and builds up to an equilibrium condition as shown in Figure 4.2 (curve A). If extraction is also taking place, for example from a plasticised material, a maximum swelling may be reached (curve B). If the absorption of fluid is accompanied by oxidation, the volume may continue to increase (curve C). 

In the vadose (unsaturated) zone, liquid organic compounds partition into four distinct but related phases NAPL adsorbed onto soil particles, free-phase NAPL, soluble constituents in soil water, and vapor-phase components as part of the soil... 

The extraction apparatus is used chiefly for dissolving out sparingly soluble constituents from mixtures, and for isolating natural products from (dry) vegetable or animal material. Occasionally it is very useful for recrystallising sparingly soluble substances from the extraction thimble by means of an appropriate solvent (especially ether). As a rule, crystals of the dissolved material separate already from the solution in the flask during the process of extraction. This solution soon becomes supersaturated even while hot. 

Leaching is concerned with the extraction of a soluble constituent from a solid by means of a solvent. The process may be used either for the production of a concentrated solution of a valuable solid material, or in order to remove an insoluble solid, such as a pigment, from a soluble material with which it is contaminated. The method used for the extraction is determined by the proportion of soluble constituent present, its distribution throughout the solid, the nature of the solid and the particle size. 

In the following example, a solid consisting of a soluble constituent A and an insoluble constituent B is considered. Leaching is carried out with a pure solvent S and a solution is produced containing a mass a of A, per unit mass of S and the total mass of A in solution is P. It will be assumed that the quantity of solvent removed in the underflow from each of the thickeners is the same, and that this is independent of the concentration of the solution in that thickener. It will be assumed that unit mass of the insoluble material B removes a mass s of solvent S in association with it. Perfect mixing in each thickener will be assumed and any adsorption of solute on the surface of the insoluble solid will be neglected. In a given thickener, therefore, the ratio of solute to solvent will be the same in the underflow as in the overflow. 

H. Inatomi, and N. Mori. Water-soluble constituents of crude drugs. III. 20320 Free amino acids isolated from ginger rhizome. Yakugaku Zasshi 1965 ... 

Figure 2. Foam properties and content of soluble constituents related to pH and percentage of glandless cottonseed flour in aqueous suspensions...

III. WATER (OR WATER-ALCOHOL) SOLUBLE CONSTITUENTS. DETERMINATION IN COMMERCIAL BLASTING EXPLOSIVES... 

The purpose of this procedure is to determine the acid-soluble constituents of commercial Blasting Explosives. To this group of constituents belong starch and antacid Ca carbonate. Infrequently Zn oxide is present, but it appears... 

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