Complete First Certificate Workbook with Answers (+ Audio CD)

For one thing, it was a rare and precious metal. For another, it enabled people to begin suspecting magic again. Can platinum be expected to behave as a middleman as saltpeter does? At first blush, the answer to that would seem to be in the negative. Of all substances, platinum is one of the most inert. It doesn't combine with oxygen or hydrogen under any normal circumstances. How, then, can it cause the two to combine? If our metaphorical catalyst is a bricklayer, then plati num can only be a bricklayer tightly bound in a strait jacket. Well, then, are we reduced to magic? To molecular action at a distance? Chemists searched for something more prosaic. The suspicion grew during the nineteenth century that the inert ness of platinum is, in one sense at least, an illusion. In the body of the metal, platinum atoms are attached to each other in all directions and are satisfied to remain so. In bulk, then, platinum will not react with oxygen or hydro gen (or most other chemicals, either). On the surface of the platinum, however, atoms on the metal boundary and immediately adjacent to the air have no other platinum atoms, in the air-direction at least, to attach themselves to ...»