Hess

The fundamental law of thermo-chemistry was discovered in 1840 by Hess. This law states that the heat of formation of a compound is the same whether the compound be formed directly from the elements, or indirectly in any way whatever. Lead sulphate, for example, may be prepared in two different ways as follows  

Any of the calorimeters described in Chapter II. is in principle capable of being used for the determination of heats of reaction. In any actual case it will, of course, be necessary to adapt the apparatus to the purpose which it is intended to serve. Jul. Thomsen, Berthelot, Favre and Silbermann, Stoh-mann, de Forcrand, Luginin, and of late years Th. W. Richards, AVrede, and W. A. Roth have been the chief workers in the development of thermo-chemistry. The more important of the apparatus devised and used by them are described in detail in many text-books. 

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Born-Haber cycle A thermodynamic cycle derived by application of Hess s law. Commonly used to calculate lattice energies of ionic solids and average bond energies of covalent compounds. E.g. NaCl ... 

Hess s law Sometimes called the law of constant heat summation, it states that the total heat change accompanying a chemical reaction is independent of the route taken in reactants becoming products. Hess s law is an application of the first law of thermodynamics to chemical reactions. 

Bonn M, Funk S, Hess C, Denzier D N, Stampfl C, Soheffler M, Wolf M and ErtI G 1999 Phonon versus eleotron-mediated desorption and oxidation of CO on Ru(OOI) Science 285 1042... 

Hess H F, Kochanski G P, Doyle J M, Greytak T J, and Kleppner D 1986 Spin-polarized hydrogen maser Phys.Rev. A 34 1602-4... 

DIeleman J, Blermann U K P and Hess P (eds) 1995 Photon-assisted processing of surfaces and thin films Proc. Symp. B E-MRS Cent. (1994) Appl. Surf. Sc/. 86 543-81... 

Pullerits T, Visscher K J, Hess S, Sundstrom V, Freiberg A, Timpmann K and Van Grondelle R 1994 Energy-transfer in the inhomogeneously broadened core antenna of purple bacteria-a simultaneous fit of low-intensity picosecond absorption and fluorescence kinetics Biophys. J. 66 236-48... 

B. A. Hess and C. M. Marian, Relativistic Effects in the Calculation of the Electronic Energy, in Computational Molecular Spectroscopy, P. Jensen and P. Bunker, eds., John Wiley Sc Sons, Inc., Chichester, UK, 2000, pp. 169-220. 

Zigmond, 1988). The ATP-hydrolysis that accompanies actin polymerization, ATP —> ADP + Pj, and the subsequent release of the cleaved phosphate (Pj) are believed to act as a clock (Pollard et ah, 1992 Allen et ah, 1996), altering in a time-dependent manner the mechanical properties of the filament and its propensity to depolymerize. Molecular dynamics simulations suggested a so-called back door mechanism for the hydrolysis reaction ATP ADP - - Pj in which ATP enters the actin from one side, ADP leaves from the same side, but Pj leaves from the opposite side, the back door (Wriggers and Schulten, 1997b). This hypothesis can explain the effect of the toxin phalloidin which blocks the exit of the putative back door pathway and, thereby, delays Pi release as observed experimentally (Dancker and Hess, 1990). 

Dancker and Hess, 1990] Dancker, P., and Hess, L. Phalloidin reduces the release of inorganic phosphate during actin polymerization. Biochira. Biophys. Acta. 1035 (1990) 197-200... 

All the experimental teats described so far have been confined to binary mixtures, but of course it is also desirable to know whether flux relations adequate in binary mixtures are still successful in mixtures with more than two components. Even in the case of ternary mixtures the form of explicit flux relations is very complex, and a complete investigation of the various matrix elements, in their dependence on both pressure and composition, would be a forbidding undertaking. Nevertheless some progress in this direction has beet made by Hesse and Koder [55] and by Remick and Geankoplis [56]. 

In general, tests have tended to concentrate attention on the ability of a flux model to interpolate through the intermediate pressure range between Knudsen diffusion control and bulk diffusion control. What is also important, but seldom known at present, is whether a model predicts a composition dependence consistent with experiment for the matrix elements in equation (10.2). In multicomponent mixtures an enormous amount of experimental work would be needed to investigate this thoroughly, but it should be possible to supplement a systematic investigation of a flux model applied to binary systems with some limited experiments on particular multicomponent mixtures, as in the work of Hesse and Koder, and Remick and Geankoplia. Interpretation of such tests would be simplest and most direct if they were to be carried out with only small differences in composition between the two sides of the porous medium. Diffusion would then occur in a system of essentially uniform composition, so that flux measurements would provide values for the matrix elements in (10.2) at well-defined compositions. 

Isobaric—see Counterdiffusion Knudsen, 3, 8-11, 65 measurements of Graham, 50-52 measurements of Hesse and Koder,... 

NODE, CORD, PMAT, NDF, MAXBN,NCOD, BC, TEMP, VEL, HESS... 

B. A. Hess, C. M. Marian, S. D. Peyerimhoff, Modern Electronic Structure Theory D. R. Yarkony, Ed., 152, World Scientihc, Singapore (1995). 

Mason, R. L. Gunst, R. F. Hess, J. L. Statistical Design and Analysis of Experiments. Wiley New York, 1989. 

I. Kompis, M. Hesse, and H. Schmid, Eloydia 34, 269 (1971) (gives a much mote elaborate classification scheme). 

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