Hydrogen continued exchange

Effects of Radiation Quenching, Ion-Bombardment, and Annealing on Catalytic Activity of Pure Nickel and Platinum Surfaces. II. Hydrogenation of Ethylene (continued). Hydrogen-Deuterium Exchange f... 

The amino acids of peptides in aqueous solution continuously exchange labile hydrogens with the solvent. The labile (exchangeable) hydrogens in peptides are those bound to heteroatoms such as sulfur, oxygen, and nitrogen (Figure 1.3). 

In 1850 Williamson suggested that in any chemical system atoms and molecules exist in a state of dynamic equilibrium, a molecule continually exchanging atoms or radicals with other molecules. In a drop of hydrochloric acid hydrogen and chlorine atoms of different molecules continually exchange partners, and during the process they must exist for a very small time in the free state. Williamson did not assume that they were electrically charged. >... 

A process by which 15% sol can be made directly by ion exchange was developed by Her and Wolter (19), whereby a heel of water or dilute sodium. silicate is heated and stirred and then. wet, drained, regenerated hydrogen ion-exchange resin (preferably of the weak acid type) and relatively concentrated sodium silicate solution are added simultaneously at such a rate as to maintain the pH at around 9. Depending on temperature and relative amount and size of particles in the heel, the rates of addition of resin and silicate can be regulated to increase the size of the silica particles without further nucleation. A similar process is operated in a column or fluidized, bed by which resin is continuously added at the top and withdrawn at the bottom in counterflow to the silica sol (20). 

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