Suppression zone volume

Ducry and Roberge reported controlled nitration of phenol in a glass microreactor with a channel width of 500 pm and an internal volume of 2.0 ml [2]. Nitration was most efficient and controlled under nearly solvent-free conditions at 20 °C without the addition of sulfuric acid or acetic acid (Scheme 4.2). Under these concentrated conditions, autocatalysis spontaneously started in the mixing zone, allowing safe control of the reaction. Undesirable polymer formation, which is significant in batch reactions, was effectively suppressed by a factor of 10. 

Leaking phosgene gas can be destroyed by spraying the contaminated zone with large volumes of water. Although the reaction is slow, the excess of water helps to suppress dispersion [1318]. Water should not be sprayed directly onto phosgene cylinders, however, since this may increase the size of the leak as a result of the formation of corrosive HCI [1318,1486]. 

Powders are especially powerful against flaming when the powder jet is directed to the flame zone instead of the seat of the fire. The flame volume to be controlled should not exceed the area that can be covered by a single shot of powder. If the seat of the fire comprises glowing particles, it should be sprinkled with light water until flaming has been suppressed, otherwise the flammable material may re-ignite. 

It is evident that, since concentration gradient suppresses nuclei growth along the longitudinal direction, nature will find the possibility to increase the nucleus s volume (and reduce Gibbs free energy) by transversal growth. Hiis statement means that the nuclei formed in the diffusion zone must be nonspherical. Because of this, it is necessary to take into account the shape optimization for each fixed volume of a nucleus. 

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