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Discusses Plato's dialogue Ion, in which it is claimed that poets and performers of poetry succeed in their arts not by knowledge or the expertise (techne) of a craftsman, but by inspiration. A link is suggested with modern views, stemming from romanticism, that art is the domain of irrationality and genius rather than the application of generalizable rational principles. However, Plato gives a low evaluation of poetry because of its alleged distance from this kind of knowledge.

Cosmology is a subject that borders on and sometimes merges with philosophy and religion. Since antiquity, the deep mysteries of the universe have intrigued mankind. Who are we? Where do we come from? What are we made of? Is the development of advanced intelligence capable of comprehending the grand design of the cosmos, the ultimate purpose of the universe? Is there life elsewhere in the universe? Is ours the only advanced intelligence or the most advanced intelligence in the universe? These questions have motivated great thinkers to pursue what Einstein called "the highest wisdom and the most radiant beauty." In the fourth century B.C., the essence of the cosmological question was formulated by the philosopher Chuang Tzu:… If there was a beginning, then there was a time before that beginning. And a time before the time which was before the time of that beginning. If there is existence, there must have been non-existence. And if there was a time when nothing existed, then there must be a time before that—when even nothing did not exist. Suddenly, when nothing came into existence, could one really say whether it belonged to the category of existence or of nonexistence? Even the very words I have just uttered, I cannot say whether they have really been uttered or not. There is nothing under the canopy of heaven greater than the tip of an autumn hair. A vast mountain is a small thing. Neither is there any age greater than that of a child cut off in infancy. P'eng Tsu [a Chinese Methuselah] himself died young. The universe and I came into being together; and I, and everything therein, are one. … Fortunately, our subject matter, solar system chemistry, is less esoteric than the questions asked by Chuang Tzu. A schematic diagram showing the principal pathways by which our solar system is formed is given in figure 4.1. The great triumphs of modern science have been summarized in this figure as fundamental contributions to the five "origins": (a) origin of the universe, (b) origin of the elements, (c) origin of the solar system, (d) origin of life, and (e) origin of advanced intelligence.

The discovery of isotopes is best understood in the context of the spectacular advances in physics and chemistry that transpired during the last 200 years. Around the year 1800, compounds and elements had been distinguished. About 39 elements were recognized, and discoveries of new elements were occurring rapidly. At about this time, the chemist John Dalton revived the ancient idea of the atom, a word derived from the Greek “atomos,” which literally means “indivisible.” According to Dalton’s theory, all matter is made of atoms which are immutable and which cannot be further subdivided. Moreover, Dalton argued that all atoms of a given element are identical in all respects, including mass, but that atoms of different elements have different masses. Even today, Dalton’s atomic theory would be accepted by a casual reader, yet later developments have shown that it is erroneous in almost every one of its key aspects. Nevertheless, Dalton’s concept of the atom was a great advance, and, with it, he not only produced the first table of atomic weights, but also generated the concept that compounds comprise elements combined in definite proportions. His theory laid the groundwork for many other important advances in early nineteenth-century chemistry, including Avogadro’s 1811 hypothesis that equal volumes of gas contain equal numbers of particles, and Prout’s 1815 hypothesis that the atomic weights of the elements are integral multiples of the weight of hydrogen. By 1870, approximately 65 elements had been identified. In that year, Mendeleev codified much of the available chemical knowledge in his “periodic table,” which basically portrayed the relationships between the chemical properties of the elements and their atomic weights. The regularities that Mendeleev found directly lead to the discovery of several “new” elements—for example, Sc, Ga, Ge, and Hf—that filled vacancies in his table and confirmed his predictions of their chemical properties and atomic weights. Similarly, shortly after Rayleigh and Ramsay isolated Ar from air in 1894, the element He was isolated from uranium minerals in 1895; the elements Ne, Kr, and Xe were found in air in 1898; and Rn was discovered in 1900.

This chapter describes the development of elastomeric microfabricated cell sorters that allow for high sensitivity, no cross contamination, and lower cost than any conventional fluorescence-activated cell sorting. The course of this development depends heavily on two key technologies that have advanced rapidly within the past decade: microfluidics and soft lithography. Sorting in the microfabricated cell sorter is accomplished via different means of microfluidic control. This confers several advantages over the conventional sorting of aerosol droplets: novel algorithms of sorting or cell manipulation can be accomplished, dispensing of reagents and biochemical reactions can occur immediately before or after the sorting event, completely enclosed fluidic devices allow for studies of biohazardous/infectious cells or particles in a safer environment, and integration of other technologies can be implemented into the cell sorter. In addition, because of the easy fabrication process and inexpensive materials used in soft lithography, this elastomeric microfabricated cell sorter is affordable to every research laboratory and can be disposable just as a gel in gel electrophoresis, which eliminates any cross contamination from previous runs. Because of the advent of soft lithography, many inexpensive, flexible, and microfabricated devices could be designed to replace flow chambers in conventional flow cytometers. Soft lithography is a micromachining technique that uses the process of rapid prototyping and replica molding to fabricate inexpensive elastomeric microfluidic devices with materials such as plastics and polymers. The elastomeric properties of plastics and polymers allow for an easy fabrication process and for cleaning for reuse or disposal. A variety of biological assays can also be carried out as a result of the chemical compatibilities of different plastic materials with different solvents. More accurate sorting of cells can be accomplished because the sorting region is at or immediately after the interrogation point. On-chip chemical processing of cells has been accomplished and can be observed at any spot on the chip before or after sorting. Time-course measurements of a single cell for kinetic studies can be implemented using novel sorting schemes. Furthermore, linear arrays of channels on a single chip, the multiplex system, may be simultaneously detected by an array of photomultiplier tubes (PMT) for multiple analysis of different channels.

Having derived a set of equations describing the equilibrium state of a multicomponent system and devised a scheme for solving them, we can begin to model the chemistries of natural waters. In this chapter we construct four models, each posing special challenges, and look in detail at the meaning of the calculation results. In each case, we use program REACT and employ an extended form of the Debye-Hückel equation for calculating species' activity coefficients, as discussed in Chapter 7. In running REACT, you work interactively following the general procedure: • Swap into the basis any needed species, minerals, or gases. Table 6.1 shows the basis in its original configuration (as it exists when you start the program). You might want to change the basis by replacing SiO2(aq) with quartz so that equilibrium with this mineral can be used to constrain the model. Or to set a fugacity buffer you might swap CO2(g) for either H+ or HCO-3. • Set a constraint for each basis member that you want to include in the calculation. For instance, the constraint might be the total concentration of sodium in the fluid, the free mass of a mineral, or the fugacity of a gas. You may also set temperature (25°C, by default) or special program options. • Run the program by typing go. • Revise the basis or constraints and reexecute the program as often as you wish. In this book, input scripts for running the various programs are set in a "typewriter" typeface. Unless a script is marked as a continuation of the previous script, you should start the program anew or type reset to clear your previous configuration. For a first chemical model, we calculate the distribution of species in surface seawater, a problem first undertaken by Garrels and Thompson (1962; see also Thompson, 1992). We base our calculation on the major element composition of seawater (Table 6.2), as determined by chemical analysis. To set pH, we assume equilibrium with CO2 in the atmosphere (Table 6.3).

Among the most vexing tasks for geochemical modelers, especially when they work with concentrated solutions, is estimating values for the activity coefficients of electrolyte species. To understand in a qualitative sense why activity coefficients in electrolyte solutions vary, we can imagine how solution concentration affects species activities. In the solution, electrical attraction draws anions around cations and cations around anions. We might think of a dilute solution as an imperfect crystal of loosely packed, hydrated ions that, within a matrix of solvent water, is constantly rearranging itself by Brownian motion. A solution of uncharged, nonpolar species, by contrast, would be nearly random in structure. The electrolyte solution is lower in free energy G than it would be if the species did not interact electrically because of the energy liberated by moving ions of opposite charge together while separating those of like charge. The chemical potentials of the species, for the same reason, are smaller than they would be in the absence of electrostatic forces.

An important consideration in constructing certain types of geochemical models, especially those applied to environmental problems, is to account for the sorption of ions from solution onto mineral surfaces. Metal oxides and aluminosilicate minerals, as well as other phases, can sorb electrolytes strongly because of their high reactivities and large surface areas (e.g., Davis and Kent, 1990). When a fluid comes in contact with minerals such as iron or aluminum oxides and zeolites, sorption may significantly diminish the mobility of dissolved components in solution, especially those present in minor amounts. Sorption, for example, may retard the spread of radionuclides near a radioactive waste repository or the migration of contaminants away from a polluting landfill. In acid mine drainages, ferric oxide sorbs heavy metals from surface water, helping limit their downstream movement (see Chapter 23). A geochemical model useful in investigating such cases must provide an accurate assessment of the effects of surface reactions. Many of the sorption theories now in use are too simplistic to be incorporated into a geochemical model intended for general use. To be useful in modeling electrolyte sorption, a theory must account for the electrical charge on the mineral surface and provide for mass balance on the sorbing sites. In addition, an internally consistent and sufficiently broad database of sorption reactions must accompany the theory. The Freundlich and Langmuir theories, which use distribution coefficients Kd to set the ratios of sorbed to dissolved ions, are applied widely in groundwater studies (Domenico and Schwartz, 1990) and used with considerable success to describe sorption of uncharged organic molecules (Adamson, 1976). The models, however, do not account for the electrical state of the surface, which varies sharply with pH, ionic strength, and solution composition. Freundlich theory prescribes no concept of mass balance, so that a surface might be predicted to sorb from solution without limit. Both theories require that distribution coefficients be determined experimentally for individual fluid and rock compositions, and hence both theories lack generality. Ion exchange theory (Stumm and Morgan, 1981; Sposito, 1989) suffers from similar limitations. Surface complexation models, on the other hand, account explicitly for the electrical state of the sorbing surface (e.g., Adamson, 1976; Stumm, 1992).