Poisoning fundamental questions

The combined use of the modem tools of surface science should allow one to understand many fundamental questions in catalysis, at least for metals. These tools afford the experimentalist with an abundance of information on surface structure, surface composition, surface electronic structure, reaction mechanism, and reaction rate parameters for elementary steps. In combination they yield direct information on the effects of surface structure and composition on heterogeneous reactivity or, more accurately, surface reactivity. Consequently, the origin of well-known effects in catalysis such as structure sensitivity, selective poisoning, ligand and ensemble effects in alloy catalysis, catalytic promotion, chemical specificity, volcano effects, to name just a few, should be subject to study via surface science. In addition, mechanistic and kinetic studies can yield information helpful in unraveling results obtained in flow reactors under greatly different operating conditions. 

Despite the prevalence of lead poisoning and the seriousness of the health problems associated with lead poisoning, many fundamental questions about the mechanism of lead poisoning still remain unanswered (29). These include... 

The fundamental question of protective mask design was first addressed in World War I should the mask completely isolate the soldier from the poisonous environment or should the mask simply remove the specific threat substance from the ambient air before it can reach the respiratory mucosa The first approach requires that a self-contained oxygen supply be provided. Because of a multitude of practical logistical constraints (eg, weight, size, expense), this approach is not used except for specialty applications in which the entire body must be enclosed. 

The problem of assessing homogeneity is of fundamental importance to the whole of polysaccharide chemistry the pertinent questions can very readily be asked, but there are, at the moment, very few satisfactory answers. Polysaccharides have often to be separated from admixtures with other polysaccharides and also proteins. How is it shown unambiguously that the poisoner product is homogeneous, and how are such mixtures of polysaccharides effectively separated ... 

A besetting problem with the study of alkene hydrogenation is deactivation of the catalyst by strongly-adsorbed carbonaceous deposits - or acetylenic residues that form even well below room temperature the base metals of Groups 8 and 10 are especially prone to this, but even the noble metals are not immune, and even the most fundamental studies are necessarily made on equilibrium surfaces, much of which is permanently inactivated. This raises the vexed question of whether such poisoned surfaces truly reflect the character of the metal, and indeed whether it is not on the carbonaceous overlayer that the catalysis occurs. Another idea that has been seriously suggested is that reaction actually occurs, in... 

Furthermore, the difference between remedy and poison is relative to each individual depending on their body mass, metabolism and sensitivity. Thus, the philosopher of science has to confront the fact that any given chemical substance does not — essentially — have a determined physiological effect. This opens up a debate similar to one in physics about the relationship between universal laws and individual phenomena as realized in the physical world [Cartwright, 1983]. Every treatment — irrespective of whether it works or not — is an experiment in this sense, with a chemical ascribed certain properties (reduction of fever for an antipyretic, reduction of allergic reactions for an antihistamine) being applied in a new and unique context. The reaction of the pharmacist is, like the physicist, to try to master the maximum number of parameters. This desire has led to the development of pharmacodynamics and pharmacokinetics, fields that study how rapidly the active principle of a medicament diffuses around the body. Nevertheless, this response does not resolve the fundamental philosophical question of the nature of the chemical substance that is introduced into the body — does it possess (in an essential manner) physiological properties, and if so, how ... 

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