Induction period before

In the absence of zinc oxide, cross-linking proceeds through an accelerator polysulfide. With TBSI (14) and other sulfenamides, the accelerator decomposes upon heating during the induction period (before cross-linking) as shown in Figure 2 (13). 

The dependence of reaction rates on pH and on the relative and absolute concentrations of reacting species, coupled with the possibility of autocatalysis and induction periods, has led to the discovery of some spectacular kinetic effects such as H. Landolt s chemical clock (1885) an acidified solution of Na2S03 is reacted with an excess of iodic acid solution in the presence of starch indicator — the induction period before the appearance of the deep-blue starch-iodine colour can be increased systematically from seconds to minutes by appropriate dilution of the solutions before mixing. With an excess of sulfite, free iodine may appear and then disappear as a single pulse due to the following sequence of reactions ... 

Owing to the hydrolysis reaction, pit development is an autocatalytic process and often there is an induction period before pit growth attains... 

Mechanisms involving glycol bond fission have been proposed for the oxidation of vicinal diols, and hydride transfer for other diols in the oxidation of diols by bromine in acid solution.The kinetics of oxidation of some five-ring heterocyclic aldehydes by acidic bromate have been studied. The reaction of phenothiazin-5-ium 3-amino-7-dimethylamino-2-methyl chloride (toluidine blue) with acidic bromate has been studied. Kinetic studies revealed an initial induction period before the rapid consumption of substrate and this is accounted for by a mechanism in which bromide ion is converted into the active bromate and hyperbromous acid during induction and the substrate is converted into the demethylated sulfoxide. 

It is not possible to propose a general mechanism from these studies, for results do not correspond to a definite pattern. Although, in all the systems, secondary amines are the most effective inhibitors, the role played by tertiary amines is confusing. In several systems (Table I, No. 1, 2, and 3) tertiary amines are much more effective than primary amines, but in others they appear to have little or no effect. Again, in acetaldehyde oxidation (Table I, No. 1 and 2) there is generally a linear relationship between the amount of inhibitor added and the induction period before either slow oxidation or ignition of the fuel occurs. In other systems (Table I, No. 3, 4, and 5), however, a much more complex relationship is obtained. Thus, amines may be acting by different mechanisms in different systems. 

Regardless of how the hot spot in an expl is created, its chemical reaction will occur at a much higher rate than that in the body of the expl, where it may be virtually zero. However, during most of the induction period before expln... 

The dialkylzincs up to the dibutyl derivatives readily ignite and bum in air. The higher alkyls fume but do not always ignite [1]. During preparation of dialkylzincs, reaction of the copper—zinc alloy with mixed alkyl bromides and iodides must begin (exotherm, often after a long induction period), before too much halide mixture is added, or violent explosions may occur [2]. Reactions with water may be explosive [3]. 

Besides copper, the principal catalyst, other materials are added to the direct reaction. About 0.1 1% of au electropositive element (Al, Mg, or Ca) is added to speed the reaction with methyl chloride, and to shorten the induction period before chlorosilanes begin to be produced in good yield. An element which forms a low-melting chloride (usually zinc)... 

Exothermic reactions can prove to be a major problem on a large scale since they are prone to induction periods before reaction starts. After the induction period, the reaction can heat up rapidly and, unless extreme care is taken in these situations, the reaction can easily go out of control. It is recommended that very careful monitoring of the temperature is undertaken in such cases, and any addition of reagents which may lead to an exothermic reaction is carried out slowly. 

There was an induction period before this rate was achieved. 

The induction period before foaming is smaller with COj because of the latent heat of vaporization of the CFC-11. 

The precipitation of the zirconium-molybdenum material is a function of acid strength, temperature and time. The rate of precipitation is lower with lower temperatures, low zirconium concentrations and higher acid strengths. There also appears to be an induction period before the onset of precipitation. Discussed here is the characterization of the zirconium molybdate solids, as obtained separately from nitric acid solutions chemical analyses, thermogravimetry and X-ray powder diffraction were used to characterize these solids. 

Frequently autocatalytic and exhibit an induction period before reaction commences. 

All the iron [6.5.6]-P-N-N-P hydrogenation catalysts require activation by an external base. The catalytic profile for achiral complex 32 showed that there is an induction period before rapid catalysis takes place for the TH of acetophenone in basic isopropanol. Unexpectedly, reacting 32 with sodium isopropoxide in either benzene or isopropanol yields the pentadentate ferraaziridine complex 39, which was isolated and structurally characterized (Scheme 10).> This unusual complex is diamagnetic, with... 

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