Solubility general

The maximum concentration atltainable under such conditions is termed the solubility of the substance at the specific temperature used in the experiment, since solubility generally increases with rising temperature. Solubility is usually expressed in grams per 100 g of solvent, or grams per 100 g of solution. Sometimes, for practical convenience, it may be expressed in grams per 100 ml of solvent or solution. 

Fra.ctiona.1 Precipituition. A preliminary enrichment of certain lanthanides can be carried out by selective precipitation of the hydroxides or double salts. The lighter lanthanides (La, Ce, Pr, Nd, Sm) do not easily form soluble double sulfates, whereas those of the heavier lanthanides (Ho, Er, Tm, Yb, Lu) and yttrium are soluble. Generally, the use of this method has been confined to cmde separation of the rare-earth mixture into three groups light, medium, and heavy. 

Films or membranes of silkworm silk have been produced by air-drying aqueous solutions prepared from the concentrated salts, followed by dialysis (11,28). The films, which are water soluble, generally contain silk in the silk I conformation with a significant content of random coil. Many different treatments have been used to modify these films to decrease their water solubiUty by converting silk I to silk II in a process found usehil for enzyme entrapment (28). Silk membranes have also been cast from fibroin solutions and characterized for permeation properties. Oxygen and water vapor transmission rates were dependent on the exposure conditions to methanol to faciUtate the conversion to silk II (29). Thin monolayer films have been formed from solubilized silkworm silk using Langmuir techniques to faciUtate stmctural characterization of the protein (30). ResolubiLized silkworm cocoon silk has been spun into fibers (31), as have recombinant silkworm silks (32). 

Solubility. Generally, resins are soluble in most common organic solvents, especially aromatics, esters, and chlorinated solvents. They are insoluble in... 

Precipitation is usually carried out in hot solutions, since the solubility generally increases with rise in temperature. 

Solution reactions between diacid chlorides and diols or diphenols are carried out in THF or CH2C12 at —10 to 30°C in die presence of tertiary amines such as triethylamine or pyridine, which play a role of both reaction catalyst and HC1 acceptor (Scheme 2.26). This synthetic mediod is also termed acceptor-catalytic polyesterification.295-297 High-temperature solution reactions have also been reported for a number of less soluble, generally semicrystalline, aromatic polyesters.6 They yield high-molar-mass polyesters exhibiting good mechanical properties and thermal stability. 

Solubility generally decreases with increase in chain size and extent of branching. The solubility of dextran can be divided into four groups — those that are readily soluble at room temperature in water, IMF, DMSO and dilute base those that have difficulty dissolving in water those that are soluble in aqueous solution only in the presence of base and, those that are soluble only under pressure, at high temperatures (> 100°C) and in the presence of base. Dextran B-512 readily dissolves in water and 6M, 2M glycine and 50% glucose aqueous solutions. 

Considering the rather complicated processes that take place during dissolution it is not surprising that some systems show peculiar behavior. For example, while solubility generally increases with temperature, there are also polymers that exhibit a negative temperature coefficient of solubility in certain solvents. Thus, poly(ethylene oxide), poly(N-isopropylacrylamide), or poly(methyl vinyl ether) dissolve in water at room temperature but precipitate upon warming. This behavior is found for all polymer-solvent systems showing a lower critical solution temperature (LCST). It can be explained by the temperature-dependent... 

Reduces contaminant solubilities, generally by chemical changes. 

Water solubility Generally, increases in logP( w are associated with a decrease in water solubility. Very poorly water soluble chemicals ([Pg.365]

Ionic strength Salts compete with water for the binding sites on amino acid side groups the amount of water bound to a protein is a function of salt concentration ( ]. The effect of ionic strength on protein functionality has been focused primarily on its effect on solubility ( ). Generally, protein solubility increases at low salt concentrations and decreases at high salt concentrations. 

Gas solubility. Generally, the greater the solubility of the solute in the solvent, the easier it is to absorb the gas, reducing the quantity of solvent and the equipment size needed for the separation. Often, a solvent that is chemically similar to the solute or that reacts chemically with the solute will provide high gas solubility. 

As a group of surfactants, ADPODSs all show very good chemical stability and high solubility, generally better than LAS. They are sold as per cent active solutions, the Dowfax series being the best known. 

In Chapter 8, you examined factors that affect the solubility of a compound. As well, you learned that the terms soluble and insoluble are relative, because no substance is completely insoluble in water. Soluble generally means that more than about 1 g of solute will dissolve in 100 mL of water at room temperature. Insoluble means that the solubility is less than 0.1 g per 100 mL. While many ionic compounds are soluble in water, many others are not. Cooks, chemists, farmers, pharmacists, and gardeners need to know which compounds are soluble and which are insoluble. (See Figure 9.1.)... 

Solid-liquid extraction, 27 of horse urine, 92 Solis, 526 Solium, 446 Soliwax, 569 Solprin, 361 Solubacter, 1041 Solubility, general notice, xiv... 

Trinitrobenzoic acid and tetranitromethane. These result from oxidation in case of overheating or pressure. The intense odor of the tetranitromethane is sometimes observed in the factories, but the trinitrobenzoic acid, owing to its solubility, generally escapes detection. ... 

A molecule that does not contain polar or ionizable groups is not likely to be soluble in water. The structures of biological molecules that arc not water soluble generally contain only aromatic or aliphatic (alkane-like) components. These groups do not interact well with water and are said to be lipophilic. If an alkane (e.g., octane) is added to a container of water it will not associate with the water but will form a separate layer on top of the water. (If the molecule were more dense than water, it would sink to the bottom to form a separate layer)... 

The calculation of the activity coefficient of a solid in a saturated solution of a n-component mixture constitutes the main difficulty in predicting the solid solubility. Generally speaking, the activity coefficient of a solid in a saturated solution of a n-component mixture can be predicted using either group-contribution methods, such as UNIFAC and ASOG, or the experimental solubilities of the solid in subsystems of the multi-component mixed solvent combined with the Wilson, NRTL, etc. equation (Acree, 1984 Prausnitz et al., 1986). 

Solubility enhancement in the presence of impurities, especially in the mother liquor, is a familiar phenomenon. Impurities in the mother liquor may not be well characterized, although their chemical structures have some similarity to the desired compound. In practical applications, the impact of impurities on solubility generally is unknown a priori and must be determined experimentally. Due to the potential impact of impurities on solubility, care should be taken in conducting crystallization experiments if the starting materials have vaiy-ing levels of impurities from batch to batch. The presence of impurities can further affect crystallization kinetics, which will be addressed in the next chapter. 

Temperature affects solubility generally, solubility of solids increases with increasing temperature. 

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