Solubilities, conductance determination

In the field of soluble conducting polymers new data have been published on poly(3-alkylthiophenes " l They show that the solubility of undoped polymers increases with increasing chain length of the substituent in the order n-butyl > ethyl methyl. But, on the other hand, it has turned out that in the doped state the electro-chemically synthesized polymers cannot be dissolved in reasonable concentrations In a very recent paper Feldhues et al. have reported that some poly(3-alkoxythio-phenes) electropolymerized under special experimental conditions are completely soluble in dipolar aprotic solvents in both the undoped and doped states. The molecular weights were determined in the undoped state by a combination of gel-permeation chromatography (GPC), mass spectroscopy and UV/VIS spectroscopy. It was established that the usual chain length of soluble poly(3-methoxthythiophene) consists of six monomer units. 

For the alkaline earth metals, only the Mg2"1" complexes were soluble enough to allow a conductivity determination in methanol. A non-electrolyte was indicated and suggested that the species was dinuclear with Mg2+ in the outer cavity (52). This is confirmed by the X-ray structure289 which shows two trans water molecules helping to achieve coordinative saturation. 

In many cases the important property will actually be the permeability, which is the product of the diffusion coefficient and the solubility of the dopant in the polymer. The solubility is determined by the degree of interaction between the diffusant and the polymer. The picture is further complicated, since reactions may take place so that several different species are diffusing. The reaction of a gaseous dopant with a conducting polymer is a complicated diffusion and reaction process. We must consider the solubility and diffusion of the molecular gas, the charge-transfer reaction to dope the polymer, the diffusion of the resulting ions in the doped (intercalated) structure and any reaction between the dopant ions and the polymer which may lead to covalent bonding. 

Strong WH, Yu DH-S, Zhu C. Determination of solution aggregation using solubility, conductivity, calorimetry, and pH measurements. Int J Pharm 1996 135 43-52. 

Sodium Chloride Solubilities in Amine-Water Mixtures. The sodium chloride solubilities were determined as a function of the amine concentration at the crystallization temperature in the single liquid phase region. The experiments were carried out in the equilibrium vessel as described in the previous section. The vessel was filled with a saturated sodium chloride solution. At the crystallization temperature a known amount of amine was added, resulting in the crystallization of sodium chloride. After a period of at least 60 minutes the stirring was stopped and liquid samples of the mixture were taken. Conductivity measurements showed that this period of time was sufficient to reach chemical equilibrium. The salt concentrations in the liquid samples were determined gravimetrically. 

As an extension of our earlier work we have studied soluble conductive polymers (sulfonic acids doped polyaniline (4), poly(3-alkyl thiophenes) (5)) for the design of a new generation of microwave absorbing materials (6). These studies have own that microwave properties were very dependent on minor changes in e q)erimental procedures. Therefore it was necessary to determine how synthetic conditions effects influence structural parameters of polymers, and how these structural parameters influence electrical, optical properties and stability over time. In the case of poly(a]kylthiophene)s, solubility of polymers permits a complete structural characterization and then a better understanding of links between... 

Since electrochemical reduction of the fullerene films involves incorporation of cations to form a new phase, the nature of the background electrolyte cation is the most important factor determining the electrochemical behavior of the film. Properties of the new phase, such as solubility, conductivity and kinetics of the phase reorganization affect the electrochemistry of the film. The nature of the solvent, on the other hand, mainly affects the solubility of the reduced film. Since the reduced fullerenes dissolve easily in many non-aqueous solvents (see Section 1.1), the electrochemical studies of the thin fullerene films have been limited mainly to acetonitrile with a few studies in propylene carbonate [136,144] or y-butyrolactone [151]. Unless otherwise stated, all the results described below have been obtained with acetonitrile as solvent. 

Solubility of Sparingly Soluble Saits.—Determinations of the conductivity may also be employed, very advantageously, for the determination of the solubility of sparingly soluble salts. 

The conductivity of the water employed should first be determined at 25°. A quantity of finely powdered lead sulphate or silver chloride is then shaken repeatedly with the conductivity water in order to remove any impurities of a comparatively soluble nature. The well-washed salt is then placed along with conductivity water in a hard-glass vessel, which is placed in a thermostat at 25°, and shaken from time to time. After intervals of about quarter of an hour, a quantity of the solution is transferred to a conductivity cell, and the conductivity determined. This is repeated with fresh samples of the solution, until constant values are obtained. 

The solubility of brucite was studied from undersaturation in the experiments of Brown, Drummond and Palmer (1996). In this study, the formation of brucite was confirmed by X-ray diffraction, and its formation was shown to be both rapid and reversible. The other four studies conducted experiments from oversaturation, with Xiong (2008) conducting experiments from both undersaturation and oversaturation. The agreement between the studies (i.e. from oversaturation and undersaturation) confirms the reversibility and rapidity of the solubility reaction. It is critical to demonstrate that the product formed from both oversaturation and undersaturation is identical (Xiong, 2008), as has been done. Therefore, the solubility constant determined is representative of that of brucite. 

It is frequently advisable in the routine examination of an ester, and before any derivatives are considered, to determine the saponification equivalent of the ester. In order to ensure that complete hydrolysis takes place in a comparatively short time, the quantitative saponi fication is conducted with a standardised alcoholic solution of caustic alkali—preferably potassium hydroxide since the potassium salts of organic acids are usuaUy more soluble than the sodium salts. A knowledge of the b.p. and the saponification equivalent of the unknown ester would provide the basis for a fairly accurate approximation of the size of the ester molecule. It must, however, be borne in mind that certain structures may effect the values of the equivalent thus aliphatic halo genated esters may consume alkali because of hydrolysis of part of the halogen during the determination, nitro esters may be reduced by the alkaline hydrolysis medium, etc. 

One method for measuring the temperature of the sea is to measure this ratio. Of course, if you were to do it now, you would take a thermometer and not a mass spectrometer. But how do you determine the temperature of the sea as it was 10,000 years ago The answer lies with tiny sea creatures called diatoms. These have shells made from calcium carbonate, itself derived from carbon dioxide in sea water. As the diatoms die, they fall to the sea floor and build a sediment of calcium carbonate. If a sample is taken from a layer of sediment 10,000 years old, the carbon dioxide can be released by addition of acid. If this carbon dioxide is put into a suitable mass spectrometer, the ratio of carbon isotopes can be measured accurately. From this value and the graph of solubilities of isotopic forms of carbon dioxide with temperature (Figure 46.5), a temperature can be extrapolated. This is the temperature of the sea during the time the diatoms were alive. To conduct such experiments in a significant manner, it is essential that the isotope abundance ratios be measured very accurately. 

TI4SCI4 and T SeCh melt at 440 and 442°C, respectively. They can be distilled between 650 and 700°C without decomposition. They are insoluble in H2O and organic solvents, but soluble in aqueous alkaline solutions. With cone, acids, decomposition takes place. The electric conductivity has been determined to be 1.4-10 and 2.1-10 fl cm for TI4SCI4 and TUSeCU, respectively. The probable structural formula is Tl3(TlCl4Y). The compounds thus, presumably, consist of Tli,4Cl4,4Y2/8 octahedra that are interconnected by the chalcogen atoms to linear chains (321). 

There are various parameters and assumptions defining radionuclide behavior that are frequently part of model descriptions that require constraints. While these must generally be determined for each particular site, laboratory experiments must also be conducted to further define the range of possibilities and the operation of particular mechanisms. These include the reversibility of adsorption, the relative rates of radionuclide leaching, the rates of irreversible incorporation of sorbed nuclides, and the rates of precipitation when concentrations are above Th or U mineral solubility limits. A key issue is whether the recoil rates of radionuclides can be clearly related to the release rates of Rn the models are most useful for providing precise values for parameters such as retardation factors, and many values rely on a reliable value for the recoil fluxes, and this is always obtained from Rn groundwater activities. These values are only as well constrained as this assumption, which therefore must be bolstered by clearer evidence. 

Salts such as silver chloride or lead sulfate which are ordinarily called insoluble do have a definite value of solubility in water. This value can be determined from conductance measurements of their saturated solutions. Since a very small amount of solute is present it must be completely dissociated into ions even in a saturated solution so that the equivalent conductivity, KV, is equal to the equivalent conductivity at infinite dilution which according to Kohlrausch s law is the sum of ionic conductances or ionic mobilities (ionic conductances are often referred to as ionic mobilities on account of the dependence of ionic conductances on the velocities at which ions migrate under the influence of an applied emf) ... 

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