Special Meanings for

Equilibrium constants are also sometimes equal to system properties of interest, such as vapor pressures, solubilities, phase compositions, and so on. This is because quite often it can be arranged that all activity terms drop out (are equal to 1.0) except the one of interest, which can then be converted to a pressure or composition. In Chapter 14 we will see that wherever this is the case, we are dealing with a buffered reaction, and the subject is developed further there. 

In our quartz-water example (Equation 9.3), the equilibrium constant expression is 

At this point the expression is perfectly general, valid for any conditions, and K is calculable from Equation (9.11) if we know the Gibbs energies of the three species in their reference states. In this case we are dealing with pure quartz and water saturated with quartz. The quartz is in its reference state, and the water contains so little silica that it is almost pure. By our definitions then (Equations 8.30) = 1 and UhjO = 1- Therefore 

This shows that assuming yH4Si04 is 1.0, which happens to be an excellent approximation in this case, we can calculate the concentration of silica (wh sjoJ in equilibrium with quartz, that is, the solubility of quartz. 

Thus the molality of Si02 in a solution in equilibrium with quartz is about 10-4064 or about 5.2 ppm.  

---

Of special meaning for ionic reactions like cationic polymerization is the consideration of the interaction between reactants and solvent. This was attained by use of the extended solvent continuum model introduced by Huron and Claverie 69,70). Specific interactions between molecule and solvent cannot be taken into account by this model. For the above reason, the solvent is not considered to be an interacting partner, rather as a factor influencing the reacting species (see part 2.3.4). 

Temperature offers an additional point of view on the stmcture of a material, and that s why it should be used with careful thinking and not randomly. In this respect, it is important to stress that what is the ambient temperature for the experimentalist may have no special meaning for the material under study. On the other hand, a given species may be of little interest at low temperature apart from the data quality improvement (this is especially true for compounds biological interest). 

The ideas of chemical graph theory have a special meaning for benzenoid hydrocarbons (BHs). As the structures of BHs do not allow for the cis/trans isomers, there is a rigorous correspondence between the adjacency matrices of BHs and their properties. In other words, any property JP(G) of the benzenoid molecule G is a function of only its adjacency matrix A(G)... 

Since efficiency can be increased by improving the density of the packing, several commercial units use special means for compressing the column after it is packed. Both radial and axial compression are available. Other columns have been designed for use with soft gels that tend to swell and shrink during use. They have movable end pieces that can be adjusted... 

The ancient Chinese proverb that a journey of one thousand miles begins with a single step has special meaning for people who want to get their blood pressure down. In fact, the worst thing an unfit person could do would be to put on a pair of running shoes and go out for a five-mile jog. Start slowly but surely. 

Apart from the point defects, there are impurity defects in ionic crystals due to some impurities in raw materials. The impact of impurity segregation on ionic conductivity of the solid electrolytes will be considered in detail in section 1.4 of this chapter. The vacancies, developed in the solid solutions during the substitution of the main ion (M in the solid solution M(Mi)02 x) by the ion substituent (Mj) of the different valence, have special meaning for solid electrolytes among impurity defects. In this case, the vacancies must appear from one of the solid-state sublattices... 

Suspension polymerization (60-63) is of special meaning for the production of technically important polymers, as for instance, expanded polystyrene and poly(vinyl chloride). Suspension polymerization refers to the carrying out of a polymerization in micron-sized droplets with oil-soluble initiators. Emulsification and polymerization take place in the same vessel and at the same time. A polymeric stabilizer or protective colloid is... 

Isolated. Not readily accessible to persons unless special means for access are used. 

Specifically, in a system where reactors like the BMN-170 are mainly intended to maintain neutron balance, specialized means for burning minor actinides and transmutation of some fission products (reactors-bumers) can be provided along with traditional thermal and fast power reactors. In spite of the possibility of using the BMN-170 for these purposes, the option of reactor loading with fuel of low minor actinide content has not yet been considered. 

In still other cases the new azeotrope which is formed does not separate into two insoluble liquids, and special means for separating it, such as liquid extraction, must be provided, but this is less desirable. 

The impressive amount of results which link personal variables to the occurrence of accidents cannot be overlooked. There are certain combinations of personality traits which facilitate accidents in specific situations. Kunkel (1973) points out "A model of accident proneness in which the degree of accident proneness is seen as a quality which supervenes with a certain constellation of several situational factors seems much more realistic. In these constellations, several factors can take on special meaning. For example, in one case a lack of intelligence may be of importance, whereas in another case risk behavior, or a massive disturbance in reaction behavior can be set in relation to accident proneness" (p. 73). 

---