Weak, solubilities

Both the carboxyl and the mercapto moieties of thioglycolic acid are acidic. Dissociation constants at 25°C are for pR, 3.6 pi, 10.5. ThioglycoHc acid is miscible ia water, ether, chloroform, dichloroethane and esters. It is weakly soluble ia aHphatic hydrocarbons such as heptane, hexane. Solvents such as alcohols and ketones can also react with thioglycolic acid. 

Oxides (Ln Oj), fluorides (LnF ), sulfides (Ln S, LnS), sulfofluorides (LnSF) of lanthanides are bases of different functional materials. Analytical control of such materials must include non-destructive methods for the identification of compound s chemical forms and quantitative detenuination methods which does not require analytical standards. The main difficulties of this analysis by chemical methods are that it is necessary to transform weakly soluble samples in solution. 

In order, for the two liquids to separate into two phases, they must be very weakly soluble in each other. When exposed to each other by mixing or shaking in a separatory funnel, they may not interpenetrate each other s realm to any extent. At the molecular level, we infer that the two species of molecules have no significant affinity for each other, rather they are predominantly attracted to other molecules with the same structure. To model this aversion, the joining and breaking rules must encode this behavior. The cells of liquids X and Y must respond to rules typified by those shown in the parameter setup tables below. With these rules we anticipate that liquid X will favor associating with other X molecules, while molecule Y will be found predominantly among other Y molecules. 

Matveev V.V. Porous Electrode with Weakly Soluble Nonelectroconducting Reagents Polarization Characteristic of an Elementary Cell. Russ. J. Electrochem, 1997 33 839-46. 

According to this method and under the hypothesis of weak solubility interactions, the logarithm of the partition coefficient of a sorbent layer with respect to a certain volatile species is the linear combination of five terms expressing the intensity of five basic interaction mechanisms. They are polarizability, polarity, two terms describe the hydrogen bonding considering the analyte acting as an acid and a base respectively, and... 

Although convection, axial diffusion, and radial diffusion actually occur simultaneously, a multistep procedure was adopted in the finite-difference calculation. For each 5-cm increment in tidal volume and for each time increment At, the differential mass-balance equations were solved for convection, axial difihision, and radial diffusion in that order. This method may slightly underestimate the dosage for weakly soluble gases, because the concentration gradient in the airway may be decreased. 

The products were weakly soluble in the ionic phase. They were separated by extraction with ether. The viscous ionic liquid could be reused in five runs without any loss of activity after thorough washing with ether and drying at 80°C after each run. In contrast, the reaction did not proceed in the polar organic solvents DMF and 7V-methylpyrrolidine, even at higher temperatures (75-80°C). The ionic liquids [Bu4N]C1 and [BMIM]C1 were also found to be ineffective. 

Enhanced reaction rates, improved yields, and high functional group compatibility are the features demonstrated by these ionic liquids. The products are weakly soluble in the ionic phase, so that they are easily separated by simple extraction with ether. 

The toxicity of fluoride depends on the type of compound ingested. Generally, the more soluble salts of inorganic fluorides, such as sodium fluoride, are more toxic that those that are either weakly soluble or insoluble [42]. Readily soluble fluoride compounds release free fluoride ions on dissolution, while fluoride compounds that are insoluble or poorly soluble do not [57,58]. Fluoride from the former... 

Sulfur is weakly soluble in H2O (10 M at 298 K) [33, 34], but Na2S is very soluble [35]. In deaerated aqueous solutions, the alkali-metal polysulfide system contains, in addition to H2O and alkali-metal cations, OH , H+, H2S, HS ,... 

Those submicron particulates which enter the alveolar sacs may undergo various degrees of absorption, depending upon the solubility of their components, or are transported to the base of the ciliated bronchiolar epithelium (54). Alveolar absorptive efficiency for most trace elements is 50-80% (50). Retention or absorption is not necessarily a simple function of solubility. Silver iodide, for example, is rapidly absorbed from the lungs even though it is weakly soluble in water (56). Likewise, insoluble elemental lead deposited in the respiratory passages is absorbed, but the mechanism involved remains to be elucidated (49). Vanadium probably accumulates in human lungs in insoluble forms... 

Thus, the concentrations of fatty acids and esters found in brandy distillates are greatly affected by the nature of the wine at the time of distillation, particularly the time interval between fermentation and distillation since most of the yeast cells settle out fairly quickly after fermentation has ceased. Obviously the degree of resuspension of the settled lees into the wine when distilled affects the amount of fatty acids and esters recovered in the distillates. The method and techniques of distillation are also very important since this class of congeners, having relatively high boiling points and weak solubility in water, exhibit wide ranges of volatility as affected by the alcohol content of the liquid volatilized. 

In this section we discuss five different materials as examples with different charging mechanisms mercury, silver iodide, oxides, mica, and semiconductors. Mercury is one example of an inert metal. Silver iodide is an example of a weakly soluble salt. Oxides are an important class of minerals. For most biological substances like proteins or lipids a similar charging process dominates. Mica is an example for a clay mineral. In addition, it is widely used as a substrate in surface force measurements and microscopy. We also included a general discussion of semiconductors because the potential in the semiconductor can be described similarly to the diffuse layer in electrolytes and there is an increasing effort to make a direct contact between a liquid or a living cell and a semiconductor. 

Different processes are responsible for the build-up of surface charge in different materials such as metals, weakly soluble salts, oxides, and clay minerals. 

In 1932, Jannik Bjerrums) started work on ammonia complexes of copper(l) and Cu(II). Some of the results were obtained with more direct techniques, such as measurement of the ammonia vapour pressure over the solution, or solubility of weakly soluble salts in various supernatant solutions. However, most of the work involved determination of the free concentration of ammonia [NH3 ] via measurements with a glass electrode of... 

The solubility-product equilibrium constant for a weakly soluble salt, MnAm,... 

In many cases the potential application of single-walled carbon nanotubes is associated with solubility of this nanomaterial in different solvents. Unfortunately, nanotubes are poorly soluble in the most of organic solvents and are insoluble in water, and this fact especially hinders biological using SWNT. Weak solubility of SWNT is a result of substantial van der Waals attractions between nanotubes aggregated in bundles. To solve nanotubes in water without any covalent functionalization, a surfactant would be added into aqueous solution, and then this mixture is suspended by sonication. It is supposed that the sound wave splits bundles in aqueous solution. A surfactant in suspension adsorbed onto the nanotube surfaces precludes aggregation of nanotubes in bundles. 

Tetracyclines are classified as broad-spectrum antibiotics obtained from soil acti-nomycetes. All tetracyclines are slightly bitter solids and are weakly soluble in water. Although tetracyclines develop organism resistance, they are the drugs of first choice in venereal disease, atypical pneumonia, cholera, brucellosis, and plague. Tetracyclines also are used in urinary tract infections, amebiasis, acne, and as prophylaxis against meningitis. 

The hydrophobicity of an organic molecule is quantified by means of its partition coefficient between octanol and water (Kow)- Kow is equal to the ratio of compound concentrations at saturation in n-octanol and in water at equilibrium and at a specific temperature. n-Octanol possesses structural properties analogous to lipidic tissues of organisms, and so Kow allows evaluation of the lipophilic character of the contaminant and thus of its capacity to be accumulated in the lipidic tissues of living organisms. The Kow value of hydrophobic organic pollutants (HOPs) is higher than 100. They are nonpolar molecules with a low water solubility. Their weak solubility and their hydrophobicity... 

Interphase inhibition [52] occurs where the inhibitive layer has a three-dimensional structure situated between the corroding metal and the electrolyte. The interphase layers generally consist of weakly soluble compounds such as oxides, hydroxides, carbonates, inhibitors, etc. and are considered to be porous. Non-porous three-dimensional layers are characteristic of passivated metals. The inhibitive efficiency depends on the properties of the three-dimensional layer, especially on porosity and stability. Interphase inhibition is generally encountered in neutral media, either in the presence or absence of oxygen. In aerated solutions, the inhibitor efficiency may be correlated with the reduction in the oxygen transport limited current at the metal surface. 

The first experiments reported here lead us to think that the impregnation of porous supports by drugs can be achieved by means of supercritical fluids. This one-step method yields a final product exempt from any residual trace of toxic solvent. The kinetics of the mass transfer is faster, besides the thermodynamics of the adsorption seems more favourable here. The main problem encountered up to now is the weak solubility of many active molecules in pure C02, which induces a limitation of the percentage of deposited product. However, this difficulty can be overcome by the use of few amount of an entrainer. In particular, ethanol which does not show any toxicity, would greatly extend the range of active substances which could be used. 

Similar analyses can be carried out for acidic or alkaline salts that are weakly soluble. One may define a dissociation constant, pK o, for a dissociation reaction of a dihydrogen phosphate of a w-valent metal, given by... 

Because of its strongly polar groups, uracil itself shows only a weak solubility in the normal solvents (0.358 parts of uracil in 100 parts of water at 25°C almost insoluble in alcohol or ether pKfl = 9.45). It is soluble in hot water and in aqueous alkali or ammonia, forming ionized species (cf. Scheme 1). Thus, uracil is, with few exceptions, not suited for chemical reactions in organic solvents. For this reason, 1,3-dimethyluracil [1,3-dimethyl-2,4(l, 3//)pyrimidinedione] has been chosen by many research groups as a versatile model compound (Scheme 18). 

Ferrocene-containing molecules present some drawbacks, however, such as a weak solubility and a tendency to decompose upon oxidation. Substituted ferro-cenes, in particular pentamethylferrocenes, are interesting alternatives. With a spacer made of three phenylene and four vinylene units, an intervalence band has been obtained, corresponding to a 0.01 eV coupling for a metal-metal distance of 26.5 A [71b]. 

Many processes involve the absorption of a gas into a liquid. Most gases are weakly soluble in liquids (such as air in water), and for such dUule solutions the mole fractions of a species i in (he gas and liquid phases at the interface are observed to be proportional to each other. That is, y, y/ or... 

Assumptions 1 Both the air and water vapor are ideal gases. 2 Air is weakly soluble in water so that Henry s law is applicable. 

Np(VI) and Pu(VI) hydroxides are weakly soluble in water, but are highly-soluble in mineral acids with formation of the hydrated Np02 and Pu02 ions or their complexes. The solubility product of Pu02(0H)2 has been estimated as 310 [79]. The solubility heats of Np02(0H)2 in IM HCl and IM HCIO4 are -53.17 and -53.80 kJ/mol, respectively [84]. This allowed calculation of AHforniation 1370 kj/mol. 

Some solids are only weakly soluble in water but dissolve readily in acidic solutions. Copper and nickel sulfides from ores, for example, can be brought into solution with strong acids, a fact that aids greatly in the separation and recovery of these valuable metals in their elemental forms. The effect of pH on solubility is shown dramatically in the damage done to buildings and monuments by acid precipitation (Fig. 16.8). Both marble and limestone are made up of small crystals of calcite (CaCOs), which dissolves to only a limited extent in natural rain (with a pH of about 5.6) but dissolves much more extensively as the rainwater becomes more acidic. The reaction... 

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