Induction time for the

Since the above treatment would insert an additional parameter in the system (i.e. an additional piece of uncertainty), that of kwsi> and since water soluble impurities usually manifest themselves as an induction time for the polymerization reaction, the empirical treatment of (32) might be more than satisfactory. 

Figure 1 The theoretical plot of induction time of oxidation determined for wr — 0, (zero rate of initiation according to reaction 1 of Scheme 1) on composition of the mixture of inhibitors InH (chain-breaking antioxidant) and D (peroxide decomposer) having the total sum of concentrations 0.01 mol/l. The curve 2 below is the plot of induction times for the same values of parameters as for line 1 but w, = 5 x 10-8 mol/l. The initial concentration of hydroperoxides was 0.001 mol/l.

These tests can also be used to evaluate the induction time for the start of an exothermic decomposition, and the compatibility with metals, additives, and contaminants. The initial part of the runaway behavior can also be investigated by Dewar tests and adiabatic storage tests. To record the complete runaway behavior and often the adibatic temperature rise, that is, the consequences of a runaway, the accelerating rate calorimeter (ARC) can be used, although it is a smaller scale test. 

Today one of the most common chemical applications of ultrasound is the initiation of a reluctant Grignard reaction. The quantitative effects of ultrasound on the induction times for the formation of a Grignard reagent in various grades of ether is given in Tab. 3.2 [88]. 

Flo. 16. Induction time for the isomerization of 1-butene on cut single crystal catalyst of MoS2 (14,37). 1-Butene (25 torr) was added first, followed by the addition of H2 (75 torr) at 100 C. 

Thus, it is possible to define the maximum allowable temperature by considering the acceptable induction time for the thermal explosion. This assessment of the probability of a runaway by using a zero-order reaction model may be too cautious. 

Regardless of the initial source of rhodium, that is, whether it is added just as a halide or as a phosphine complex, under the reaction conditions 4.1 is formed. With phosphine complexes, the phosphine is converted to a phospho-nium (PRj" or 11 PR, ) counter-cation. As chelating phosphines bind more strongly than the monodentate ones, the induction time for the formation of 4.1 with chelating phosphines is longer. 

Figure 1. Induction time for the CO + 20% mixture as a function of initial...

Induction times for nucleation of a tripalmitin melt at different temperatures are shown in Figure 12 (36). The tripalmitin melt was cooled quickly from 80°C to the different crystallization temperatures indicated on the figure and induction time measured as the first point of detection of crystals on a polarized light microscope. The relative time scales for the onset of nucleation are clearly shown, with the less-stable ot form taking significantly less time to nucleate than the (3 polymorph. The induction time for the most stable (3 polymorph was substantially longer than for either of the less-stable polymorphs. 

AMF, MF-TAG, and MF-DAG obtained from measurements of light-scattering intensities are shown in Figure 5. In this case, MF-TAG crystallized first, and AMF had the longest induction times. The induction times for the crystallization curves are reported in Table 2. 

The induction time for the initial endothermic bond breaking reaction can be calculated using the high pressure, high temperature transition state theory. Experimental unimolecular gas phase reaction rates under low temperature (<1000K) shock conditions obey the usual Arrhenius law ... 

For effective use of the developed model, information on the induction time and droplet evaporation rates, as a function of the local conditions in the shock-heated mixture, is needed. Currently, in the absence of such information, parametric studies with various constant induction times and droplet evaporation rates have been carried out. The predicted detonation velocity as a function of the initial droplet size is shown in Fig. 11.6 for a nominalJP-lO-oxygen mixture with an equivalence ratio of 0.12. A d -law evaporation with a rate of 0.1 cm /s and an induction time for the fuel-vapor of 1 //s was used for this series of simulations. The velocity deficit observed previously in many experimental studies of multiphase detonations is predicted by the numerical model. In the absence... 

Recently, the asymmetric hydrogenation of two related substrates with precatalysts of the type [Rh(DuPHOS)(diolefin)]BF4 has been investigated (4). It was demonstrated that the COD-containing complex required an induction time for the COD ligand to be removed from the precatalyst. This manifested itself as very low initial rate of hydrogen uptake, which increased as more catalyst became available. Conversely, for the NBD precatalyst there was no observable induction time and the hydrogenation reactions were complete in a fraction of the time required for the COD containing systems. Furthermore, at the end of the reactions they were able to show that in the case of the COD systems, approximately half the precatalyst introduced to the reaction system had not been converted to active catalyst. 

As the electrode size is reduced still further, we reach a point where only a single nucleus is able to develop during the period of the experiment and the determination of the nucleation rate is achieved by measuring the induction time for the appearance of the first nucleus and the growth rate of this single nucleus can be determined from the subsequent current-time transient. The nucleation is, of course, a stochastic process and therefore the induction time will vary. The determination of the nucleation rate therefore requires a large number of transients to be studied. 

Figure 11.10 Rate and induction time for the nucleation of lovastatin from methanol at 25 °C plotted according to Classical Nucleation Theory. (Reprinted from Mahajan, A.J., and Kirwan, D.J., J. Crystal Growth 144, pp. 281-286. 1994 with permission from Elsevier Science.)...

Acute exposure to vanadium compounds causes irritation of the eyes and the upper and lower respiratory tract. Mild effects are characterized by sneezing rhinitis, cough, chest pain and conjunctivitis. These effects seem to be concentration-dependent and usually reversible. Exposure of healthy volunteers to vanadium pentoxide dust (1 mg/m ) produced respiratory irritation and a persistent cough lasting 8 days this occurred after about 12 h. Exposure to a lower concentration (0.2 mg/m ) had the same effect but the induction time for the persistent cough was longer (about 20 h). Concentrations of 0.1 mg/m caused no irritation (Zenz and Berg. 1967). 

Further quantitative interpretation of induction times for the extraction of information about individual rate coefficients, pursued particularly by Gardiner and co-workers, has involved explicit attention to the values of C, and 0/, and has led to such discoveries as ... 

It is necessary to exceed the critical anodic potential (23) bd for the electrochemical breakdown of passivation by pitting and consists of these factors (i) presence of halides at the interface (ii) induction time for the initiation of the breakdown process, leading to localized conditions that may increase the localized corrosion current density (iii) development of favorable conditions inside the pits for propagation when the local sites become immobile and localized at certain sites. Electrochemical breakdown of some metal oxides is possible in the case of copper, lead, and tin cathodically to metal while ferric oxide is reduced to the ferrous ion in aqueous solutions. Zinc and aluminum oxides are not cathodically reducible and in these cases hydrogen is reduced. The vigorous evolution of hydrogen assisted by electron conducting zinc oxide can accelerate the breakdown of passivity. 

Further, we have seen that the amount of water converted into hydrates depends somewhat on die asphaltene content of the emulsion systems. However, in the systems investigated die composition of die continuous phase also influences the hydrate formation. We have not been able to be conclusive about how the state of the asphaltenes (monomeric or aggregated) relates to the hydrate conversion. In the investigated systems, waxes reduce the induction time for the gas hydrate formation, probably because the waxes act as crystallization nuclei. The conversion rate was not influenced by the presence of waxes. To what extent the results from the model systems can be applied to real systems is not clear at present. 

Induction time for the nucleation of new fibers on the host fibers... 

Gunawardena, G., Hills, G. and Scharifker, B.R. (1981) Induction times for the formation of single mercury nuclei on a platinum microelectrode. Journal of Eiectroanaiyticai Chemistry, 130, 99-112. 

The one component that significantly affects the cure rate of photocurable polymers is the photoinitiator. Decreasing the concentration of a photoinitiator from 0.5 to 0.3% can more than double the induction time for the reaction. Since the photoinitiation is frequently the most expensive of the photopolymer ingredients, DPC offers a fast, reliable method for optimising and verifying the concentration of the photoinitiator. 

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