Volume demand

Pure Substances We will begin with the simplest case, namely change of volume in transformations of substances. Every substance needs a certain amount of space. How much this is depends upon how much space is needed by its atoms and the gaps in between them. The volume taken up is greater, the more of the substance there is. In order to compare the volume needed by different substances (Experiment 8.1), one relates the volume to amount of substance. This so-called molar volume Vm then serves as the measiue of the space needed by a pure substance  

The names or formulas of a substance can take the place of the index for example, Fh20 = 18.07 cm moP or y(H20) = 18.07 cm mol for the molar volume of (liquid) water. 

The volume demand of a substance is by no means constant, but also depends upon its miheu. Substances are compressible to some extent and can expand when 

Experiment 8.1 Volume demand of various pure substances. How different the volume demand, i.e., the space taken up by various pure substances can be, is easy to show. Cylindrical blocks all representing an amount of substance of 1 mol are placed side by side. 

Also in the case of molar volume the standard value is the value at room conditions, meaning 298 K and 100 kPa. As before, we add the symbol as upper index to the symbol of the quantity, for example, 

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Although the risk of scale deposition and fouling in the boiler section is related to several factors such as the FW volume demands, boiler pressure, and heat flux density at various boiler surfaces, it is equally a function of the level of FW contaminants such as residual hardness, sulfates, silica, and iron. Thus, as a generality, the higher the quality of FW (reduced levels of contaminants), the lower the risk of deposition on boiler surfaces. 

Where RW of basic good quality is supplied for LP steam boilers (that is, firebox, Scotch marine, cast-iron sectional boilers, etc. at operating pressures below 15 psig) and where the MU water volume demand exceeds 5% of the FW, pretreatment by ion-exchange softening should be additionally provided. This rule also applies to electrical resistance boilers, electrode boilers, vertical boilers, and coil boilers. 

Despite the simplicity of chemistries presently employed for the commercially available hyperbranched polymers, these materials are still relatively high priced compared to traditional commodity polymers. This is undoubtedly related to the early stage, low volume demands for these products. Hyperbranched polymers will evolve as substitutes for traditional polymers as their unique properties are used to greatly enhance products on a cost-performance basis. In summary, the enhanced used of hyperbranched polymers in engineered products will depend upon many of the following prerequisites ... 

The processes utilized in the refinery to produce finished fuels such as gasoline, jet fuel, diesel fuel, and heating oil can be quite complex. Constant monitoring of the refining process is required by engineers. This is because the characteristics of the various crude oils refined can change frequently and also because the finished product volume demand can change often. 

Adipic acid is a very large-volume organic chemical. It is one of the top 50 chemicals produced in the United States in terms of volume. Demand is highly cyclic, reflecting the automotive and housing markets especially. Prices usually follow the variability in crude oil prices. Adipic acid for nylon takes about 60% of U.S. cyclohexane production the remainder goes to caprolactam for nylon-6, export, and miscellaneous uses. 

In addition to data gathering, QA will want the validation batches made entirely by the production department. When this stipulation is satisfied, it will be demonstrated that the process control is independent of the technical background of the operating personnel. This kind of approach demonstrates that the manufacturing process will support the soon-to-be-marketed product s volume demands. This approach also allows QA to have a baseline activity with which it can compare future audit activities. 

Processes are now available to provide controlled release to liquid pesticides, molten lower melting point pesticides, and solid higher melting point pesticide crystals in the size range and volume demanded of pesticide products. These processes will continue to develop into more robust and simpler systems. New processes wiU be developed. 

Based on the above considerations, the types of reactions that are amenable to inorganic membrane reactors in the first wave of industrial implementation will probably be as follows (1) The reactions are heterogeneous catalytic reactions, particularly dehydrogenation processes (2) The reaction temperature exceeds approximately 200°C (3) When the reactions call for high-purity reactant(s) or produces) and the volume demand is relatively small, dense membrane reactors (e.g., Pd-based) can be used. On the other hand, if high productivity is critical for the process involved, porous membrane reactors are necessary to make the process economically viable. 

While maleic acid does not have the volume demand of such oxidation... 

In general, wliat has been said in regard to the oxidation of naphthalene to phthalie anhydride applies to the oxidation of benzene to maleic acid with the exception tliat the volume demand for phthalie anhydride is greater. Somewhat different methods are also used in the recovery of product due to its different nature. 

Dissolved Substances It is noteworthy that the volume demand for a substance also depends upon what kind of a chemical enviromnent it is in. Consider this example. 1 mol of pure water with a volume of about 18 cm is stirred into 1 m of concentrated sulfuric acid, and then the warmed mixture is cooled back down to the initial temperature. One finds that the entire volume has increased by only 8.5 cm and not by 18 cm as might have been expected. Obviously, water dissolved in sulfuric acid requires less space and the molar volume is smaller in this milieu ... 

The volume demand for some substances in certain solvents can even be negative. The volume shrinks when such a substance is dissolved. An example of this is the solution of sodium hydroxide in water ... 

As we have seen, the molar volume for a pure substance can be easily defined and calculated. How should we proceed, though, when we want to find the volume demand of a substance distributed inside another material environment ... 

Consider a body that absorbs a small amount of a substance. It will generally expand somewhat (Fig. 8.2). The volume grows because the substance now inside the body needs space, and by taking this space, the particles loosen the body s atomic structure. An example would be the volume demand of water penetrating a more or less moist block of wood causing the wood to expand more. The measure of... 

Experiment 8.3 Negative volume demand of NaOH in water The flat-bottomed flask is filled with colored water up to the mark (with the cooling water running). Subsequently, as many pellets of sodium hydroxide as possible are put into the flask. After dissolution of the sodium hydroxide and cooling down of the resulting solution, the water level is considerably lower than before. 

We use the value of at infinite dilution (c —> 0) as the basic value of the molar volume of a dissolved substance, meaning the volume demand of the substance in the practically pure solvent. The basic value at standard temperature... 

If the molar volumes Va and Vb in a mixture of A and B are known for a certain composition, the volume of a portion of this mixture results from the amounts and volume demands of the components ... 

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