Homogeneity determination definition

Bajoras and Makuska investigated the effect of hydrogen bonding complexes on the reactivities of (meth)acrylic and isotonic acids in a binary mixture of dimethyl sulfoxide and water using IR spectroscopy (Bajoras and Makuska, 1986). They demonstrated that by altering the solvent composition it was possible to carry out copolymerization in the azeotropic which resulted in the production of homogeneous copolymers of definite compositions at high conversions. Furthermore, it was shown that water solvent fraction determines the rate of copolymerization and the reactivity ratios of the comonomers. This in turn determines the copolymer composition. 

We adopt this kinetic definition of reaction order without reference to the actual number of molecules involved in each act of chemical transformation. In homogeneous reactions the kinetically determined order is equal to the number of molecules participating in the actual change of which the rate is being measured. In heterogeneous reactions this equality is not necessarily preserved. It will be convenient to call the order inferred from the effect of pressure on the time of half-change the apparent order, and to refer to the number of molecules involved as the true order of the reaction. We have now to consider the relation of the true and the apparent order in various cases. ... 

The second anomalous feature is that, as can be clearly seen in Fig. 12, the volume fraction of the respective phases in the coexistence-temperature range is a monotonic function of temperature. This indicates that the state of gel in this temperature range is a distinct thermodynamic state. This state is characterized by mixing of the two phases, and is not identifiable to any of the homogeneous phases. The mixing ratio is not arbitrary but takes a definite value determined as a function of temperature. 

Ecotoxicological considerations and the effort to achieve an increasingly accurate description of the state of the environment challenge analytical chemists who need to determine increasingly lower concentrations of various analytes in samples that have complex and even non-homogenous matrices. The newly coined expression "analytics" emphasizes the interdisciplinary nature of available methods for obtaining information about material systems, with many methods that exceed the strict definition of analytical chemistry. Drawing on the disciplines of chemistry, physics, computer science, electronics, material science, and chemometrics, this book provides in depth information on the most important problems in analytics of samples from aquatic ecosystems. 

Spectroscopy is also extensively applied to determination of reaction mechanisms and transient intermediates in homogeneous systems (34-37) and at interfaces (38). Spectroscopic theory and methods are integral to the very definition of photochemical reactions, i.e. chemical reactions occurring via molecular excited states (39-42). Photochemical reactions are different in rate, product yield and distribution from thermally induced reactions, even in solution. Surface mediated photochemistry (43) represents a potential resource for the direction of reactions which is multifaceted and barely tapped. One such facet, that of solar-excited electrochemical reactions, has been extensively, but by no means, exhaustively studied under the rubric photoelectrochemistry (PEC) (44-48). 

Adsorbed films between two immiscible liquids. The question of the meaning of the term pn in the surface layer has been raised by Crax-ford, Gatty, and Teorell,2 without, however, coming to any very clear decision. Danielli s estimate was a very rough one, based on the application of the Donnan equilibrium between the surface layer and the interior, and suffers from the difficulties always attending an attempt to consider concentrations in the surface layer in a similar way to concentrations in a bulk phase the surface layer is not homogeneous. pH is closely related to, and is determined by, the electrochemical potential (see Chap. VIII, pp. 304 ff.), and this depends on the electrostatic potential, which varies rapidly at different levels near to the surface it appears possible that the only satisfactory definition of pa in the surface may be one which varies rapidly at different depths. The question appears one which would repay... 

When determining the percentage composition by mass of a homogeneous sample, the size of the sample does not matter. According to the law of definite proportions, there is a fixed proportion of each element in the compound, no matter how much of the compound you have. This means that you can choose a convenient sample size when calculating percentage composition from a formula. 

If metabolism in animal models is extensive or the generated metabolite(s) is shown to have toxic effects, in vitro metabolism studies using isolated P-450 isozymes, tissue homogenates containing the microsomal fraction, hepatocytes, and liver slices are commonly conducted to determine if the extent of metabolism and the metabolite profile is similar for animals and humans. The results from these in vitro metabolism comparison studies can be used to select the animal models for definitive development studies that have similar metabolism profiles to humans. 

When a pure liquid is placed in an evacuated bulb, molecules will leave the liquid phase and enter the gas phase until the pressure of the vapor in the bulb reaches a definite value, which is determined by the nature of the liquid and its temperature. This pressure is called the vapor pressure of the liquid at a given temperature. The equilibrium vapor pressure is independent of the quantity of liquid and vapor present, as long as both phases exist in equilibrium with each other at the specified temperature. As the temperature is increased, the vapor pressure also increases up to the critical point, at which the two-phase system becomes a homogeneous, one-phase fluid. 

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