THE WATER ANALOG

The endothermicity of the hydration reactions was confirmed. The Gibbs energies amount to AG = 6.7 and 12.8 kcal/mol for the chloride and ammonium replacements of the water. Analogous values for transplatin are 9.4 and 11.5 kcal/mol. These dechlorination results match the experimental data fairly accurately. 

Carnot s 118-page Reflections on the Motive Power of Fire received favorable reviews, then fell into obscurity. This was partly because the world was not ready to understand it, and partly because the theory s champion, Carnot, died in a cholera epidemic when he was 36 (and his personal effects, including many of his papers, were burned). And it was partly because the water analogy had limitations. 

The reader can easily imagine an electric circuit where a battery is analogous to the water pump, and two resistors are analogous to the valves shown above. Of course, the flow of electric current would be double that of the case where there is only a single resistor, very similar to the behavior of the water analog. If the voltage is the same but the current is doubled in the two-resistor case, then Ohm s law tells us that the total resistance in the two-resistor case must be half that of the one-resistor case. This is quite intuitive and simple, when both resistors are equal. 

Reciprocals of a third and fourth (or more) resistances could also be added to the ones in equation 3.3. The water analog shows intuitively why that is allowed any number of faucets could be added, and if the pressure is held constant, they simply add to the total flow, and therefore they decrease the total resistance to flow. Once all this is understood, equation 3. 3 does not really have to be memorized. The reader only needs to know that the voltage could be cancelled out, giving the general form (equation 3.3, which is often the only form shown in other electronics books, and usually without explanation.)... 

This bathochromic shift is typical of 77 —> tt transitions. The behavior of the water solution when acidified was attributed by Albert (175) absorption by the thiazolium cation, by analogy with pyridine. However, allowance is made for the very weak basicity of thiazole (pK = 2.52) compared with that of pyridine (pK = 5.2), Ellis and Griffiths (176) consider the differences between the spectrum of thiazole in water and in... 

As will be seen shortly, an analogous result is obtained with the silica-water system, where the BET monolayer capacity of water calculated from the water isotherm is roughly equal to the hydroxyl content of the silica surface. 

Somewhat analogous to these rice products is Oatrim, a material based on oat flour. It was developed at the Northern Laboratory of the USDA and is offered commercially by several firms. Oatrim contains 5% proteia, 5% P-glucan, 2% pentosans, and 83% maltodextrias. Unique properties are claimed based on the P-glucan component, and preparation of Oatrim is disclosed ia USDA pubHcations and patents. Briefly, oat flour is broken down by a-amylase, then the water-soluble component is dried and is the product of commerce, aimed at ground meat product usage. 

Endotliermic Decompositions These decompositions are mostly reversible. The most investigated substances have been hydrates and hydroxides, which give off water, and carbonates, which give off CO9. Dehydration is analogous to evaporation, and its rate depends on the moisture content of the gas. Activation energies are nearly the same as reaction enthalpies. As the reaction proceeds in the particle, the rate of reaction is impeded hy resistance to diffusion of the water through the already formed product. A particular substance may have sever hydrates. Which one is present will depend on the... 

The fuel cell must be cooled with either water or air, and the heat can be converted to electricity in a bottoming cycle. The dc electrical output ot the stack is usually converted to ac and stepped up or down in voltage, depending on the application. Analogous to PAFds, M(iF(i stacks are about 1 nr (10.8 ft") in plan area and quite tall. A stack generates 200 to 300 kW. Market entiy is expected in 1999. 

A notable exploitation of this reaction has been used for the preparation of potential anticancer agents. In an attempt to control the water solubility of thiophene analogs, a series of sodium salts of 2,5-dicarboethoxy-3,4-dihydroxythiophene have been produced by condensation between thiodiglycolate esters and diethyloxalate. These condensation reactions consistently proceeded in good yield. 

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