One Mole

by Elio

If you mul­ti­ply the num­ber of bac­te­ria thought to ex­ist in one hu­man be­ing, say 1 x 10¹⁴ by how many hu­mans there are, about 6.6 x 10⁹, you get close to a fa­mil­iar num­ber.

And who was Avo­gadro any­way? Some eponyms fail to do jus­tice to the éponymee. My fa­vorite ex­am­ple is Amerigo Vespucci, whose name is on all the land of this hemi­sphere but about whom most peo­ple, me in­cluded, know noth­ing. So with Avo­gadro, which is why I looked it up. I found out that in 1811 he pro­posed that "at a given tem­per­a­ture and pres­sure the vol­ume of a gas is pro­por­tional to the num­ber of atoms or mol­e­cules re­gard­less of the na­ture of the gas." Pretty good stuff for the times. In 1909, a French physi­cist, Jean Per­rin, pro­posed that this con­stant be named af­ter Dr. A. The fa­vor was re­paid be­cause Per­rin later went on to get the No­bel prize in Physics for ac­tu­ally de­ter­min­ing the value of the con­stant. He could have got­ten a close value by count­ing the to­tal num­ber of bac­te­ria in all hu­mans in­stead.

Amadeo Avo­gadro was born to a no­ble fam­ily in 1776 and died in 1856 in Turin, where he was pro­fes­sor of Physics. He was ac­tive in a rev­o­lu­tion­ary move­ment that suc­ceeded in es­tab­lish­ing a con­sti­tu­tion for the King­dom of Pied­mont. For a pe­riod of 10 years, he was re­moved from his aca­d­e­mic chair but he even­tu­ally re­turned to it.