Word: cobalt
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Fortnight ago, five Glaoui sons gathered at Marrakech to divvy up the sprawling wealth El Glaoui had left. Reportedly there was $17 million in cash lying around the old mud-red palace. There were palaces and houses in virtually every major Moroccan city, stock in lead, cobalt and manganese mines, bank accounts in Paris, London and Geneva. The rumor spread that El Glaoui's sons were maneuvering to block a plan sponsored by Morocco's new government to redistribute the huge land holdings El Glaoui had amassed in southern Morocco...
Better Chemists. Weiss and Shipman dried the clam flesh, reduced it to ash and dissolved the ash in dilute acid. The solution showed characteristic gamma rays that could come only from cobalt 60. This was odd, they thought; cobalt 60 is not a fission product, and it had not been found in other radioactive material, even in samples from much closer to Ground Zero. To make doubly sure. Weiss and Shipman ran a careful analysis. One clam proved to contain one-tenth of a microcurie of cobalt 60; the other had one-third of a microcurie...
These are not very dangerous amounts; the maximum permissible concentration of cobalt 60 in the human body is listed by the Bureau of Standards as three microcuries. A man would have to eat at least ten of the hot clams (20 Ibs. of flesh) to exceed this limit. But Weiss and Shipman cannot be sure that cobalt 60 was not heavily concentrated in some special part of the clam's tissue, increasing the danger proportionately...
Since the dangerously radioactive cobalt 60 is not a product of fission, it must have come from some other element, perhaps nonradioactive cobalt 59, exposed to free neutrons given off by the thermonuclear explosion. It could never have been more than a trace in the sea water, or the careful tests made in the Marshalls just after the explosion would have detected it. But clams are apparently better chemists than men are; they went after the cobalt 60 for reasons of their own and collected an astonishing amount of the radioacitve isotope...
Unsuspected Mechanism. Weiss and Shipman were not aware when they began their work that clams have a love for cobalt. To find out whether other species than the giant clam like to collect it, they added a little cobalt to San Francisco Bay water (which normally has no detectable trace) and put some local clams into it. Later analysis by the Navy team showed that these clams also have the trait of collecting cobalt...