Measurement of solution

For example, the measurements of solution osmotic pressure made with membranes by Traube and Pfeffer were used by van t Hoff in 1887 to develop his limit law, which explains the behavior of ideal dilute solutions. This work led direcdy to the van t Hoff equation. At about the same time, the concept of a perfectly selective semipermeable membrane was used by MaxweU and others in developing the kinetic theory of gases. 

B measure of solute—membrane pore waU interaction force l ... 

Retention Rejection and Reflection Retention and rejection are used almost interchangeably. A third term, reflection, includes a measure of solute-solvent coupling, and is the term used in irreversible thermodynamic descriptions of membrane separations. It is important in only a few practical cases. Rejection is the term of trade in reverse osmosis (RO) and NF, and retention is usually used in UF and MF. 

Garside, J. and Mullin, J.W., 1966. Continuous measurement of solution concentration in a crystallizer. Chemistry and Industry, November 26, pp. 2007-2008. 

Comparing Eqs. (8-95) and (8-97) shows that the quantity m X is a measure of solution acidity in excess of the ideal state this gives rise to the term excess acidity method for the X acidity function approach. We also have, from Eqs. (8-87) and (8-88),... 

When the full distribution is needed, it is measured by size-exclusion chromatography (also called gel permeation chromatography). This is a solution technique that requires dissolution of the polymer in a reasonable solvent such as tetrahydrofuran or tetrachlorlobenzene. For polymers that require exotic solvents or solution temperatures above about 150°C, a simple measurement of solution viscosity can be a useful surrogate for the actual molecular weight. The viscosity of the pure polymer (i.e., a polymer melt viscosity) can also be used. Such simplified techniques are often satisfactory for routine quality control, particularly for condensation polymers such as PET that vary in average molecular weight but usually have a polydispersity of 2. 

This can be carried out in vitro (in brain slices, cultured cell preparations) or in vivo and involves penetrating the experimental tissue with a carbon-fibre electrode of 5-30 pm in diameter (Fig. 4.9). This serves as an oxidising electrode and the Faradaic current generated by the oxidation of solutes on the surface of the electrode is proportional to their concentration. Obviously, only neurotransmitters which can be oxidised can be measured in this way so the technique is mainly limited to the study of monoamines and their metabolites. The amplitude of each peak on the ensuing voltammogram is a measure of solute concentration and individual peaks can be identified because different... 

Direct measurements of solute activity are based on studies of the equilibria in which a given substance is involved. The parameters of these equilibria (the distribution coefficients, equilibrium constants, and EMF of galvanic cells) are determined at different concentrations. Then these data are extrapolated to very low concentrations, where the activity coincides with concentration and the activity coefficient becomes unity. 

The majority of RDC studies have concentrated on the measurement of solute transfer resistances, in particular, focusing on their relevance as model systems for drug transfer across skin [14,39-41]. In these studies, isopropyl myristate is commonly used as a solvent, since it is considered to serve as a model compound for skin lipids. However, it has since been reported that the true interfacial kinetics cannot be resolved with the RDC due to the severe mass transport limitations inherent in the technique [15]. The RDC has also been used to study more complicated interfacial processes such as kinetics in a microemulsion system [42], where one of the compartments contains an emulsion. 

The competition model and solvent interaction model were at one time heatedly debated but current thinking maintains that under defined r iitions the two theories are equivalent, however, it is impossible to distinguish between then on the basis of experimental retention data alone [231,249]. Based on the measurement of solute and solvent activity coefficients it was concluded that both models operate alternately. At higher solvent B concentrations, the competition effect diminishes, since under these conditions the solute molecule can enter the Interfacial layer without displacing solvent molecules. The competition model, in its expanded form, is more general, and can be used to derive the principal results of the solvent interaction model as a special case. In essence, it seems that the end result is the same, only the tenet that surface adsorption or solvent association are the dominant retention interactions remain at variance. 

Composition Profile Measurement. Results of Zieba et al. (1997) will be given as an example of the measurement of solute distribution in an alloy undergoing a phase transformation. They studied discontinuous precipitation in cobalt-tungsten alloys, in which a Co-32 wt% W alloy was aged in the temperature range 875 K to 1025 K, and high spatial resolution X-ray microanalysis of thin foils by STEM was used to measure the solute distribution near the reaction front. 

The Henry s law constant is essentially an air-water partition coefficient which can be determined by measurement of solute concentrations in both phases. This raises the difficulty of accurate analytical determination in two very different media which usually requires different techniques. Accordingly, effort has been devoted to devising techniques in which concentrations are measured in only one phase and the other concentration is deduced from a mass balance. These methods are generally more accurate. The principal difficulty arises with hydrophobic, low-volatility chemicals which can establish only very small concentrations in both phases. 

Jenke, D.R., Hayward, D.S., Kenley, R.A. (1990) Liquid chromatographic measurement of solute/solvent partition coefficients application to solute/container interactions. J. Chromatogr. Sci. 20, 609-6612. 

An extreme example of the measurement of solution enthalpies is provided by that of lanthanum trichloride in molten potassium chloride. The value reported, which refers to infinite dilution, is - 20.8 kcal mol-1 (-87.0 kJ mol-1), at 890°C (223). This value is comparable with those for dissolution in lower alcohols at normal temperatures. 

Direct measurement of solute sorption-desorption kinetics in chromatographic systems provides some useful insights into the mechanism... 

In order to characterize the intermediates leading to the photo-Fries/cleavage and hydroperoxide products shown in Schemes I and II, laser flash photolysis measurements of solutions of both MDI and TDI based polyurethanes were conducted. The results from this study are interpreted by comparison with transient spectra of an aryl monocarbamate and the bispropyl carbamate of MDI. In addition, a dimethylsilicon analog of the MDI bispropyl carbamate is used to... 

Titrimetric analysis is sometimes called volumetric analysis because it is characterized by the frequent measurement of solution volume utilizing precision glassware. 

We also note two reports on the degradation of stacked films of oriented PET. In the first [36], photodegradation is said to be two-step in nature with weak links cleaving first followed by a much slower cleaving of the strong links . The chain scission process was tracked versus exposure time by measurement of solution viscosity [37], In the second paper [38], the surface nature of the degradation was reported and the rationale elucidated for why surface degradation causes overall mechanical failure limited by that layer, much as we have discussed in the impact properties of the PECT (see above). 

We start the chapter with a few simpler applications Beer-Lambert s law and Gaussian curves. Light absorption measurements of solutions are most commonly used for the investigation of many chemical processes. A good understanding of Beer-Lambert s law and in particular the application of the very elegant matrix notation, is useful for the methods developed later in the... 

Vibrating Flow Densimeter. One of the major advances made in making density measurements of solutions was the system developed by Kratky et al. (21) which measures the natural vibration frequency of a tube containing a liquid. The oscillating frequency (f) of the tube is related to its mass (m) by... 

The instrument constant B can be determined by measuring the t in two fluids of known density. Air and water are used by most workers (22). In our laboratory we used seawater of known conductivity and pure water to calibrate our vibrating flow systems (53). The system gives accurate densities in dilute solutions, however, care must be taken when using the system in concentrated solutions or in solutions with large viscosities. The development of commercial flow densimeters has caused a rapid increase in the output of density measurements of solutions. Desnoyers, Jolicoeur and coworkers (54-69) have used this system to measure the densities of numerous electrolyte solutions. We have used the system to study the densities of electrolyte mixtures and natural waters (53,70-81). We routinely take our system to sea on oceanographic cruises (79) and find the system to perform very well on a rocking ship. 

McLaughlin GE, Kim KJ, Berg MM, Agoris P, Lubman RL, Crandall ED (1993) Measurement of solute fluxes in isolated rat lungs. Respir Physiol 91 321-334. 

Dorr and Buttgereit (1963), using U.V. measurements of solutions of mesitylene and hexamethylbenzene in chloroform, bromoform, carbon tetrachloride and carbon tetrabromide, were able to demonstrate a weak electron transfer complex formation with these solvents. These investigations show that hexamethylbenzene is a more powerful electron donor than mesitylene. A similar influence on an acceptor property... 

Efficiency or plate count (N)—an assessment of column performance. N should be fairly constant for a particular column and can be calculated from the retention time and the peak widths. Selectivity (a)—the ratio of retention k ) of two adjacent peaks. Sample capacity— the maximum mass of sample that can be loaded on the column without destroying peak resolution. Capacity factor k )—a measure of solute retention obtained by dividing the net retention time by the void time. 

Paar turbidimeter analychem Avisual-extinction device for measurement of solution turbidity the length of the column of liquid suspension is adjusted until the light filament can no longer be seen. par. tor-bo dim-ad-ar) paired electron phys chem One of two electrons that form a valence bond between two atoms. jperd i lek,tran ... 

If the branching density is sufficiently high to hinder segmental flexibility and impose strong excluded volume and even steric interactions, molecular dimensions become rigid. Measurements of solution and melt viscosity showed that the properties of dendritic molecules approached that of solid spheres as the... 

Chai, X.S. and Zhu, J.Y. Simultaneous measurements of solute concentration and Hetrry s constant trsing mrrltiple headspace extraction gas chromatography, Anal. Chem., 70(16) 3481-3487, 1998a. 

Dipole moment measurements of solutions of cis- (64BSF2119 65JCS571) and tru/ii-thianthrene 5,10-dioxide (65JCS571) and of thianthrene 5,5,10,10-tetroxide (65JCS57I) gave values of 1.86 and 1.70, 4.88, and 5.11 D, from which fold angles of 139°, 130°, and 140° respectively, were calculated. 

Another experimental approach (93. 941 to CSD control involved the use of on line solution and slurry density measurements as measured variables with jacket temperature and residence time as manipulated variables. This was attempted in a 10 liter MSMPR crystallizer employing K-alum. Results showed that this scheme was able to retirin the crystallizer to a steady state after the introduction of an upset and that on-line density measurements of solution and slurry could be obtained and used. 

From the consecutive measurements of solution concentrations and crystal purities during the optical resolution by preferential crystallization, the crystallization of D-threonlne other than the seeded component (L-threonine) was observed In the later stage of the resolution. Washing of the seed crystals was found to be effective to delay the purity decrease. D-threonine was believed to be Introduced... 

In 1C, the election-detection mode is the one based on conductivity measurements of solutions in which the ionic load of the eluent is low, either due to the use of eluents of low specific conductivity, or due to the chemical suppression of the eluent conductivity achieved by proper devices (see further). Nevertheless, there are applications in which this kind of detection is not applicable, e.g., for species with low specific conductivity or for species (metals) that can precipitate during the classical detection with suppression. Among the techniques that can be used as an alternative to conductometric detection, spectrophotometry, amperometry, and spectroscopy (atomic absorption, AA, atomic emission, AE) or spectrometry (inductively coupled plasma-mass spectrometry, ICP-MS, and MS) are those most widely used. Hence, the wide number of techniques available, together with the improvement of stationary phase technology, makes it possible to widen the spectrum of substances analyzable by 1C and to achieve extremely low detection limits. 

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