Decomposition, heat

Chemical reaction sources catalysis, reaction with powerful oxidants, reaction of metals with halocarhons, thermite reaction, thermally unstahle materials, accumulation of unstahle materials, pyrophoric materials, polymerization, decomposition, heat of adsorption, water reactive solids, incompatihle materials. 

A useful indication of a chemical reactivity hazard is the heat (energy) of reaction. For some reaction types, the heat of reaction may be known by another name, such as heat of decomposition, heat of combustion or heat of polymerization. 

If the adiabatic temperature increase of the reaction is less than 50 K during normal operation and the starting materials, reaction mixture or products have no thermal instabilities within a temperature range of (Tpr0cess + ATadiab) then the normal operation can be regarded as safe. The same applies when secondary decomposition reactions produce so little heat that the sum of this decomposition heat and the heat of reaction does not cause an adiabatic temperature increase of more than 50 K. 

In the last reaction the decompn is endothermic, and if the gaseous mixt of products of decompn is heated, these react exothermically with explosive effect (See also Heat of Decomposition, Heat of Dissociation and Heat of Explosion of AN)... 

The discontinuous explosion process is the oldest technical process. It was mainly used for the production of color blacks. Continuous processes were later developed with production rates up to 500 kg/h [4.20], Acetylene or acetylene-containing gases are fed into a preheated, cylindrical reactor with a ceramic inner liner. Once ignited, the reaction is maintained by the decomposition heat that is evolved. The carbon black is collected in settling chambers and cyclones. Approximately 95-99% of the theoretical yield is obtained. 

Phenyl methyl selenium bromo-iodide, (C6H5)(CH3)SeIBr, is obtained when the dibromide is triturated with a cold solution of potassium iodide of the same concentration. The yield is quantitative, and the product separates from alcohol as red, ill-defined, compact crystals, M.pt. 85° C. with decomposition. Heating at 100° C. causes quantitative decomposition to methyl iodide and bromoselenobenzene, the reaction being represented as follows r... 

The free energy of formation of anhydrous H202 liquid at 25°C is calculated as -28.78 kcal/mol. The decomposition heat of pure liquid H202 to water and oxygen at 25°C is -23.44 kcal/mol. 

Some gases explode by themselves without being mixed with other gases. For example, acetylene, ethylene oxide and ozone fall into this category. This property is recognized experimentally and no common evaluation method has been established. If the calculated decomposition heat of lg of the gas is large, it is assumed that the material may induce a decomposition explosion. 

Thermodynamic and Energy Release Evaluation Program", ASTM DS51 (1974) b) Mitsuru Arai, Kazuhiro Tohyama, Masamitsu Tamura, Tadao Yoshida, "Correlations between CHETAH Decomposition Heats and Performances of Explosive Compounds", Kogyo Kayaku (J. Ind. Explosive Soc. Japan), 41, 293 (1980)... 

DSC(l) data were obtained with a Model DSC20 apparatus (Shimadzu Co., Ltd.) at Yoshida laboratory, The University of Tokyo. A sealed cell made of soft stainless steel was used as the sample cell K 1. The extrapolated decomposition temperature 1" was taken as the decomposition start temperature (Tdsc or Tdta). In DSC(l),the peak area was obtained by weighing the peak-area cutout. The apparatus constant, k, which is used to determine the DSC decomposition heat (Qdsc(1)) from the peak area, was determined by obtaining the values of heat of fusion for potassium nitrate, indium, tin, and potassium perchlorate. 

Chemical decomposition Heating of organic peroxide formulations requiring refrigeration Provide adequate temperature controls MSDS... 

Thermolysis of JV-thioacylamino-2,4,6-triphenylpyridinium salts (110) leads to complete decomposition. Heating the salts with triphenylpyridine gives the nitriles (RCN) by loss of sulfur.88... 

Pressure-Generating Substances Filling an apparent gap in the statutory definitions, CPSC regulations provide that a substance that generates pressure through decomposition, heat or other means imder Section 2(fKl)(A) is a hazardous substance under the following circumstances ... 

In order to come within the basic definition of hazardous substance , a substance (or mixture) must meet two requirements. First it must be toxic , corrosive , and irritant a strong sensitizer designated as such by the Secretary, flammable , or be a substance which generates pressure through decomposition, heat, or other means. (All these terms, except the self-explanatory phrase generates pressure through decomposition, heat, or other means , are defined in the bill.) Secondly, it must be a substance (or mixture) which—... 

The temperature profile displays a drop due to the injection of propellant followed by a peak related to the exothermic decomposition. Heat transfer to the reactor leads to a return to the initial temperature of the catalyst. 

Salts of the type [H2L][Zn ] (X = C1 or Br HjL = HN+(CH2CH2)3N+H) have been prepared and show interesting behaviour on thermal decomposition.Heating to 423 K results in elimination of HX to form the ZnX3LH complex, in which the HL molecule now also occupies a position in a deformed tetrahedral coordination sphere. 

Combustible liquid flash point 72°C (163°F). It is least combustible among the heavy metal alkyls. The fire hazard is significantly low. The rate and spontaneity of air oxidation is also low. However, because of its moderate endothermicity (A// within the range -1-215 kcal/mol), it should be reasonably unstable and therefore susceptible to violent decomposition. Heating, rigorous agitation or prolonged contact with oxidants and nonmetal halides should, therefore, be considered a potential hazard. It is liable to explode if exposed to air for several days. 

Most azido compounds explode in their decomposition. But thermochemistry, photochemistry, and discharge methods can slow down the decomposition reaction. The products of explosive decomposition are the corresponding simple substances. Decomposition heat of one compound equals its standard formation heat. 

For the effective specific heat capacity, the energy change during decomposition (i.e., decomposition heat) must be considered. The rate of energy absorbed for decomposition (endothermic reaction) is determined by the reaction rate, that is, the decomposition rate that is obtained by the decomposition model (Eq. (2.19)). Combining Eq. (2.19) and Eq. (4.30) gives ... 

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