Hess, Henri

Hess Henri Germain (1802-1850) Swiss, prof, of chem.in Rus. St. Petersburg Univ., founder of thermochemistry, formulated (Hess ) Law stating that amount of heat evolved is irrespective to intermediary stages... 

Quinamine, CjgH240jN2. This alkaloid was isolated from Cinchona succiruhra bark by Hesse and subsequently found by him in the barks of several cinchona spp. but especially in C. ledgeriana bark. It has been examined in detail recently by Henry, Kirby and Shaw. )... 

If no external evidence is available, it is still possible to determine the unit cell dimensions of crystals of low symmetry from powder diffraction patterns, provided that sharp patterns with high resolution are avail able. Hesse (1948) and Lipson (1949) have used numerical methods successfully for orthorhombic crystals. (Sec also Henry, Lipson, and Wooster, 1951 Bunn 1955.) Ito (1950) has devised a method which in principle will lead to a possible unit cell for a crystal of any symmetry. It may not be the true unit cell appropriate to the crystal symmetry, but when a possible cell satisfying all the diffraction peaks on a powder pattern lias been obtained by Ito s method, the true unit cell can be obtained by a reduction process first devised by Delaunay (1933). Ito applies the reduction process to the reciprocal lattice (see p. 185), but International Tables (1952) recommend that the procedure should be applied to the direct space lattice. 

Radon is slightly soluble in water, and obeys Henry s Law. At 20°C the partition coefficient (amount of radon per litre of water at equilibrium divided by the amount per litre of air) is 0.26. Despite the low solubility, water supplies derived locally from granite and metamorphic rocks can be an important source of airborne radon in dwellings (Nero Nazaroff, 1984 Hess etal., 1987). Radon is more soluble in fats and organic liquids, and the partition coefficient between air and human fat is about unity at 37°C. 

Germain Henri Hess is noted today for two fundamental principles of thermochemistry the law of constant summation of heat (known simply as Hess s law) and the law of thermoneutrality. These discoveries were remarkable in that they were postulated without any supporting theoretical framework and took place in a field of study almost totally neglected by his contemporaries. Hess s law is of immense practical importance and is used to this day to determine heats of reaction when their direct measurements are difficult or impossible. 

Leicester, Henry M. (1951). Germain Henri Hess and the Foundation of Thermochemistry. Journal of Chemical Education 28 581-583. 

Germain Henri Hess developed Hess s Law in 1840 after studying the heat required or emitted from reactions composed of several steps. 

Russell S. Harmon, Henry P. Schwarcz, Mel Gascoyne, John W. Hess, and Derek C. Ford ... 

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