Captor

Local exhaust vendladon serves to remove a contaminant near its source of emission into die atmosphere of a workplace. A system normally comprises a hood, ducting which conveys exhausted air and contaminants, a fan, equipment for contaminants collecdon/removal and a stack for dispersion of decontaminated air. Hoods normally comprise an enclosure, a boodi, a captor hood or a receptor hood. Those relying on odier dian complete enclosure should be as close as practicable to die source of polludon to achieve maximum efficiency. 

If enelosure or use of a booth is impraetieable, a captor hood is used. This is plaeed some distanee from the souree of pollution and the rate of air flow needs to be sueh as to eapture eontaminants at die furdiermost point of origin. 

Figure 12.2 Reduction in air velocity with distance from captor hood (distance given as % of hood diameter)...

Goodfellow, H. D., and P. Safe. Theoretical Analysis of Captor Hoods for Contaminant Control. Ann. Occup. Flygiene (October 1988). 

Figure 46.2 Captor-type claw hood for a furnace...

Figure 46.3 Types of hoods, (a) Enclosure (b) receptor (c) captor...

At definite times samples are withdrawn and titrated by an appropriate method. The temperature is controlled either with a constant temperature oil bath or a heating jacket and a P.I.D. regulation with a captor plunged in the reaction medium. 

The alkanephosphonic acid dichlorides obtained by these methods are converted with amines, with all reactions carried out in solvents such as acetone, benzene, or diethyl ether at 10°C with triethylamine as HC1 captor. The conversion runs quantitatively followed by a purification with the help of column chromatography with chloroform/methanol in a ratio of 9 1 as mobile phase. The alkanephosphonic acid bisdiethanolamides could be obtained as pure substances with alkane residues of C8, C10, C12, and Ci4. The N-(2-hydroxyethane) alkanephosphonic acid 0,0-diethanolamide esters were also prepared in high purity. The obtained surfactants are generally stable up to 100°C. Only the alkanephosphonic acid bismonomethylamides are decomposed beneath this temperature forming cyclic compounds. 

Strongly acidic vanadium(V) oxidises bromide in a sulphate ion medium . The reaction is first-order in both oxidant and sulphuric acid. The dependence of the rate on bromide ion concentration is complex and a maximum is exhibited at certain acidities. A more satisfactory examination is that of Julian and Waters who employed a perchlorate ion medium and controlled the ionic strength. They used several organic substrates which acted as captors for bromine radical species. The rate of reduction of V(V) is independent of the substrate employed and almost independent of substrate concentration. At a given acidity the kinetics are... 

RELATIVE VOLATIUTT AND ELECTRON-CAPTORE DETECTOR RESPONSE OF HAL06EK-ONITAININ6 ALKYSILYL ETHER DERIVATIVES... 

I have no doubt, I say, and indeed I have none. Richard of Gloucester has ever been thus, and thus he commands the allegiance of men as much as does his royal blood and the confidence of his brother whom I have learned to call the late King Edward. Have I not made Richard the chief executor of my will, though he be my captor and my enemy even to death ... 

You scum Scoundrels I tried to twist round on my knees to face my captor, but the dagger pricked my throat again. How dare you How dare you I am a sworn knight ... 

We ve our orders, said my captor, pulling me to my feet. Come along. ... 

And now, sitting on the rough grass with my captors waiting for me to finish my meat that we may take the road again, I know that I have had no other earthly love like Louis s not his for me, or mine for him. And now I never shall. 

Then he turned away and vaulted onto his horse unaided, as he always did, though he was small and ill-made, and took the road to Stony Stratford. My only comfort was that as I mounted, unarmed and set about with many well-armed men, I looked at the sky, the clouds, and toward the west. I hope it will not rain, I said to my captors. 

In the first of a projected trilogy, Stephenson explores alchemy as one of the roots of mathematics and computers. With the ancestors of characters appearing in Cryptonomicon (Stephenson s previous novel), this literary adventure traverses Europe of the 1700s, with stops in the laboratories of some of the most famous scientists of the day, while in a separate timeline set one hundred years earlier, a drifter attempts to help a young woman exact revenge against her former captors... 

Garrigues described the use of graphite as a heat captor under the action of micro-wave irradiation. Graphite is a chemically inert support that couples strongly with microwaves by a conduction process and is able to transmit intense thermal energy to the supported reagents [35]. 

Maybe they will," she admitted. "But he s even surer than the others that he ll get off. His attorneys are boasting. Schmitz says his captors were G.I. eager beavers, and when his friends come he ll be set free. Lately, he just frowns and blinks. He s... 

CAPTOR A modification of the "Activated Sludge sewage treatment system, in which the micro-organisms are retained in a reticulated polyether foam. Invented in 1978 at UMIST, Manchester, and developed by Simon-Hardey, UK. 

LINPOR [Linde porous medium] A biological waste water treatment process, using an open-pore plastic foam for retaining the biomass. Its use enables the capacity of an activated sludge plant to be increased without adding extra tanks. Invented at the Technische Universitat, Munich, and further developed by Linde, Munich. See also CAPTOR. 

The concept of captodative substitution implies the simultaneous action of a captor (acceptor) and a donor substituent on a molecule. Furthermore, in the definition of Viehe et al. (1979), which was given for free radicals, both substituents are bonded to the same or to two vinylogous carbon atoms, i.e. 1,1- and 1,3-substitution, and so forth is considered. One might, however, also include 1,2-, 1,4-,. .. disubstitution, a situation which is more often referred to as push-pull substitution. Before discussing captodative substituent effects it might be helpful to analyse the terms capto and dative in more detail. 

At first glance the significance of these two terms seems to be obvious. A substituent which withdraws electron density is a captor and a substituent which donates electron density is a donor. However, both properties cannot be discussed independently from a partner from which they accept, or to which they donate, electrons. This raises the question of whether it is in principle possible to define a universal donor or acceptor character for a substituent. 

As a summary of these considerations we must conclude that on the basis of polar effects most substituents are captors and that it is the resonance effect which leads to the discrimination of two classes of substituents. 

The first indication of the existence of a captodative substituent effect by Dewar (1952) was based on 7t-molecular orbital theory. The combined action of the n-electrons of a donor and a captor substituent on the total Jt-electron energy of a free radical was derived by perturbation theory. Besides the formulation of this special stabilizing situation and the quotation of a literature example [5] (Goldschmidt, 1920, 1929) as experimental evidence, the elaboration of the phenomenon was not pursued further, neither theoretically nor experimentally. 

Fig. 1 FMO diagram for the formation of a captodative-substituted radical c—C—d by successive interaction of (A) a carbon radical with a captor (c) and of (B) a captor-substituted carbon radical with a donor (d) substituent.

All these examples, and it would be possible to quote more, are a manifestation that captor and donor subtituents stabilize radicals. Judged by the temperature range where dissociation occurs it seems as if captodative substitution stabilizes better than dicaptor substitution (Stella et al., 1981). Mostly, however, these are qualitative or semiquantitative observations which do not allow one to evaluate the magnitude of stabilization in kcal mol". In particular, the question of a synergetic action of the captor and the donor substituent cannot be answered satisfactorily. In part, the observed effects might be related to steric interactions of the substituents. 

It is evident from the data in Table 6 that, with only one exception (entry 13), the combination of two captor or two donor substituents does not produce an additive effect, whereas, without exception, the captodative combinations display synergetic behaviour. Thus, the delocalization of the unpaired spin density in captodative radicals is markedly increased in comparison to pure additive superposition of capto and dative effects. This result is all the more significant since two identical substituents do not... 

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