Dangerous reactions concentration

All other dangerous reactions consist of oxidations of bismuth by strong oxidants. Thus, chloric and perchloric acids lead to highly sensitive explosives (probably bismuth chlorate and perchlorate). Fuming nitric acid causes the incandescence of bismuth at ambient temperature whereas a detonation occurs when molten bismuth is mixed with concentrated nitric acid. Rnally, a bismuth/molten ammonium nitrate mixture causes a very violent or even an explosive reaction. 

Chlorine dioxide, CIO2 (17.23) is a yellow gas (bp 283 K), and is produced in the highly dangerous reaction between potassium chlorate, KCIO3, and concentrated H2SO4. Reaction 17.48 is a safer method of synthesis, and reactions 17.2 and 17.3 showed two of the commercial methods used to make CIO2. CIO2 is used to bleach flour and wood pulp and... 

Plant operator should check the compatibility of wastes (mixed feed) before feeding for preventing dangerous reactions, formation and subsequent release of toxic compounds and concentration of pollutants (e.g. halogens, sulphurous compounds) in waste and feed rate should be controlled as per capacity of air pollution control facilities. 

When drops of concentrated sulfuric acid are allowed to fall on powdered potassium chlorate, a crackling sound ensues. In this notoriously dangerous reaction, the noise is the explosive decomposition of evolved chlorine dioxide gas ... 

Aqueous sulfamic acid solutions are quite stable at room temperature. At higher temperatures, however, acidic solutions and the ammonium salt hydroly2e to sulfates. Rates increase rapidly with temperature elevation, lower pH, and increased concentrations. These hydrolysis reactions are exothermic. Concentrated solutions heated in closed containers or in vessels having adequate venting can generate sufficient internal pressure to cause container mpture. An ammonium sulfamate, 60 wt % aqueous solution exhibits mnaway hydrolysis when heated to 200°C at pH 5 or to 130°C at pH 2. The danger is minimised in a weU-vented container, however, because the 60 wt % solution boils at 107°C (8,10). Hydrolysis reactions are ... 

Can hazards from the reaction be reduced by changing the relative concentration of reactants or other operating conditions Can side reactions produce toxic or explosive material, or cause dangerous fouling ... 

Jencks has emphasized a danger in the technique of reducing the reaction order by using an excess concentration of one reactant. If this reactant contains an impurity that itself is very reactive, the impurity concentration may be sufficiently high to lead to spurious results from the unsuspected reaction. 

Ordinarily, reaction rate is directly related to reactant concentration. The higher the concentration of starting materials, the more rapidly a reaction takes place. Pure hydrogen peroxide, in which the concentration of H202 molecules is about 40 mol/L, is an extremely dangerous substance. In the presence of trace impurities, it decomposes explosively... 

A process is inherently safe in a rigorous sense, when no fluctuation or disturbance can cause an accident. To search for synthetic routes that avoid hazardous reactants, intermediates, and reaction mixtures, is an impetus to be seriously considered by chemists and process designers. Nevertheless, there will always be a need to cope with potentially hazardous materials and reaction mixtures in future process design work, the more so because process streams are expected to become potentially more dangerous in the future. The process streams will be more concentrated to increase energy efficiency, to ease purification, and to decrease the load of wastewater and spent acids. More concentrated process streams have a higher specific content of latent energy and are hence less stable. 

It is exactly the same with the haloform reaction. If chloroform is poured onto the acetone/sodium hydroxide mixture, there can be an explosion whereas incorporating hydroxide in the other two substances would not be dangerous. In this case the risk factor is the high hydroxide concentration. 

All vapourisation processes of solutions made of unstable substances are dangerous because the concentration of the unstable substance increases. In this category the heterogeneous reactions can be grouped together they lead to accidents because of compounds with too thin a particle size distribution. So it is possible to control the reaction of phenyllithium by using thick pieces of lithium. 

When o-nitroaniiine is heated in the presence of concentrated sulphuric acid above 200°C it gives rise to a violent reaction after a period of induction. There is also the formation of a black foam that has a volume 150 times greater than the original volume. This is a dangerous variant of the spectacular black snake experiment that is made with a nitrated derivative of a very similar structure and is described on p. 343. This is a phenomenon that can be compared with the ones described concerning p-nitrotoluene sulphonation on p.301. 

During the preparation of the hexamethoxides of rhenium, molybdenum and tungsten by co-condensation with excess tetramethoxysilane on a cold surface, simultaneous co-condensation is necessary to avoid the danger of explosion present when sequential condensation of the reactants is employed. In the latter case, the high concentrations of hexafluoride at the interface leads to violent reaction with the silane. 

Chlorine trifluoride will dissolve in carbon tetrachloride at low temperatures without reaction. Such solutions are dangerous, being capable of detonation. If it is used as a solvent for fluorination with the trifluoride, it is therefore important to prevent build-up of high concentrations of the latter. 

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