Used to Determine Solubility

When restrictions are not placed on the amount of time or the amount of material, different solvents or different quantities of acid or base are usually used as variables. It is not only important to know the solubility of the compounds in aqueous solutions but also in other solvents to which the compound might be exposed during synthesis and formulation. The solvents usually have a wide range of dielectric constants and the experimental results provide a solubility profile which can be utilized in the selection of appropriate solvents to use during the development of the compound. Since the compounds almost always selected for development are either weak acids or weak bases, the solubilities of the compounds will be pH-dependent. The use of different amounts of acid or base with an excess amount of compound permits the determination of a pH-solubility profile. 

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Since buffers are an example of the common-ion effect, the concentration of ions (hence the pH) of a buffer solution can be calculated using a method that is similar to the method you used to determine solubility in a common ion effect problem. You will use Ka, however, instead of Kgp. Also, buffers are in homogeneous equilibria, unlike saturated solubility systems, which are in heterogeneous equilibria. Therefore, you need to consider the initial concentration of the reactants. (The reactants are not solids, so their concentration is not constant.)... 

Molecular emission cavity analysis has been used to determine soluble sulfate in soil [69]. 

The p]< values, solubilities and partition coefficients of a series of On-acylpropranolol prodrugs... were determined. Titrations in a range of aqueous meBianolic solutions were used to estimate the pKg, while titration under non-logarithmic conditions (when excess undissolved base was present in the system) was used to determine solubilities."... 

This expression shows that for a non reacting gas (K = 0),the first moment of the response peak can be used to determine solubility of A in the liquid. ... 

Solubility tests should be performed on every unknown. They are extremely important in determining the nature of the main functional group of the imknown compound. The tests are very simple and require only small amounts of the unknown. In addition, solubility tests reveal whether the compoimd is a strong base (amine), a weak acid (phenol), a strong acid (carboxylic acid), or a neutral substance (aldehyde, ketone, alcohol, ester). The common solvents used to determine solubility types are... 

It has been more than fifty years since the discovery of the transuranium elements. The initial activities in this field established the fundamental solution and solid-state chemistry of the first two of these elements and their compounds under the auspices of the Manhattan Project. New separation methods including solvent extraction techniques and uranium isotope separation played a leading role in these programs. Tracer techniques were widely used to determine solubilities (or solubility liinits) of transuranium compounds as well as to obtain information about the coorination chemistry in aqueous solution. A little later, special solvent extraction and ion-exchange techniques were developed to isolate pure transplutonium elements on the milligram and smaller scale. The second edition of The Chemistry of the Actinide Elements, published in 1986 (i), covers most of these topics. A detailed overview of the history of transuranium chemistry is given in Transuranium Elements A Half Century (2). 

Randomly select ten apricots per tree. Remove the stone from flesh and macerate flesh with a blender. The pureed flesh is then sieved and the juice is collected. The juice is then used to determine soluble solid content and sugar content. 

The method is used to determine the molecular weight primarily of those compounds which are too slightly soluble in the usual cold solvents for the more efficient freezing-point method to be nployed. 

The use of accurate isotope ratio measurement is exemplified here by a method used to determine the temperature of the Mediterranean Sea 10,000 years ago. It is known that the relative solubility of the two isotopic forms of carbon dioxide COj) in sea water depends on temperature... 

Instrumental Quantitative Analysis. Methods such as x-ray spectroscopy, oaes, and naa do not necessarily require pretreatment of samples to soluble forms. Only reUable and verified standards are needed. Other instmmental methods that can be used to determine a wide range of chromium concentrations are atomic absorption spectroscopy (aas), flame photometry, icap-aes, and direct current plasma—atomic emission spectroscopy (dcp-aes). These methods caimot distinguish the oxidation states of chromium, and speciation at trace levels usually requires a previous wet-chemical separation. However, the instmmental methods are preferred over (3)-diphenylcarbazide for trace chromium concentrations, because of the difficulty of oxidizing very small quantities of Cr(III). 

The Freundlich liquid phase isotherm can be used to determine the effect of solubility on the adsorptive capacity of activated carbon over a range of different concentrations. Phenol is highly soluble due to its polar nature whilst, in comparison, tetrachloroethylene (PCE) has a low solubility due to being non-polar. In the isotherms illustrated, the concentration of phenol is low relative to its solubility limit and consequently, the adsorptive capacity peaks at 18% maximum (see Figure 9). In comparison the concentration of tetrachloroethylene is relatively close to its solubility limit and, accordingly, the adsorptive capacity is exceptionally good. 

The simplest method to measure gas solubilities is what we will call the stoichiometric technique. It can be done either at constant pressure or with a constant volume of gas. For the constant pressure technique, a given mass of IL is brought into contact with the gas at a fixed pressure. The liquid is stirred vigorously to enhance mass transfer and to allow approach to equilibrium. The total volume of gas delivered to the system (minus the vapor space) is used to determine the solubility. If the experiments are performed at pressures sufficiently high that the ideal gas law does not apply, then accurate equations of state can be employed to convert the volume of gas into moles. For the constant volume technique, a loiown volume of gas is brought into contact with the stirred ionic liquid sample. Once equilibrium is reached, the pressure is noted, and the solubility is determined as before. The effect of temperature (and thus enthalpies and entropies) can be determined by repetition of the experiment at multiple temperatures. 

Aniline is an aromatic amine (CgHjNHj). When used as a solvent, it is selective to aromatic molecules at low temperatures, and paraffins and naphthenes at higher temperature. Aniline is used to determine aromaticity of oil products, including FCC feedstocks. Aniline point (AP) is the minimum temperature for complete solubility of an oii sample in aniline. 

The general approach illustrated by Example 18.7 is widely used to determine equilibrium constants for solution reactions. The pH meter in particular can be used to determine acid or base equilibrium constants by measuring the pH of solutions containing known concentrations of weak acids or bases. Specific ion electrodes are readily adapted to the determination of solubility product constants. For example, a chloride ion electrode can be used to find [Cl-] in equilibrium with AgCl(s) and a known [Ag+]. From that information, Ksp of AgCl can be calculated. 

The compound Cr(OH), is very insoluble in water therefore, electrochemical methods must be used to determine its fCsp. Given that the reduction of Cr(OH)3(s) to Cr(s) and hydroxide ions has a standard potential of —1.34 V, calculate the solubility product for Cr(OH)3. 

Table 3 shows some physicochemical properties used as international GA quality parameters, for example moisture, total ash content, volatile matter and internal energy, with reference to gums taken from Acacia Senegal species in Sudan (FAO, 1990, Larson Bromley, 1991). The physicochemical properties of GA may vary depending on the origin and age of trees, the exudation time, the storage type, and climate. The moisture content facilitates the solubility of GA carbohydrate hydrophilic and hydrophobic proteins. The total ash content is used to determine the critical levels of foreign matter, insoluble matter in... 

Various methods have been used to determine the redox potentials (Table XI). Very commonly, EPR-monitored chemical redox titration is performed, which can be used to measure the redox potential not only in isolated complexes but also in membrane preparations. In general, there is good agreement between redox potentials determined in membranes, isolated complexes, or isolated Rieske proteins or fragments the only exception is the water-soluble Rieske fragment from spinach bef complex where differences of more than 50 mV have been observed by the same group but using different methods (31). 

The MUF resin pH was determined using pH meter model pH 340-A/SET l-MTM. The pH meter was calibrated before it was used to determine the pH of the resin. The viscosity was determined using the Cole-Parmer 98936-15 viscometer (R2 spindle, lOOrpm speed). The storage life was a test of shelf life of the MUF resin under the ambient environment. Resin was first stored at ambient room temperature. Viscosity of the resin was checked for every three to four days. The ratio of water that can be added into resin before it turned turbid or precipitated is called resin solubility. The resin solubility was determined by divide the weight of resin and the weight of water added into resin before it turned turbid or precipitated. The curing period of a resin was defined as the time period for the resin to be hardened after application in a 30°C and 1.0% of NH4CI powder (as hardener). 

This paper concerns the main properties of water soluble pectins in sol and gel states. First of all, the methods of purification and characterization are discussed. The method of steric exclusion chromatography equipped with different detectors is demonstrated as the most useful to determine the macromolecular characteristics of these polymers the role of aggregation is pointed out. 

High-performance liquid chromatography (HPLC) with a micellar mobile phase or with a selective pre-column or reaction detection system has also been used to determine alkylenebis(dithiocarbamaes). ° Zineb and mancozeb residues in feed were determined by ion-pair HPLC with ultraviolet (UV) detection at 272 nm. These compounds were converted to water-soluble sodium salts with ethylenediaminetetra-acetic acid (EDTA) and sodium hydroxide. The extracts were ion-pair methylated with tetrabuthylammonium hydrogensulfate (ion-pair reagent) in a chloroform-hexane solvent mixture at pH 6.5-8.S. The use of an electrochemical detector has also been reported. ... 

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