They try it, the problem is that you can compare mass better than you can count molecules. So one of the approaches is, to manufacture a Si sphere as perfect as

They try it, the problem is that you can compare mass better than you can count molecules. So one of the approaches is, to manufacture a Si sphere as perfect as possible and calculate the mass from the radius and the properties of Si crystals. As far as I know, this had no practical results, except cool photos of strangely rendered looking spheres. [1] http://www.theepochtimes.com/n2/images/stories/large/2011/03/27/10301_big_2.jpg http://www.theepochtimes.com/n2/images/stories/large/2011/03... [2] http://www.ptb.de/cms/en/themenrundgaenge/hueterindereinheiten/das-si/avogadro.html http://www.ptb.de/cms/en/themenrundgaenge/hueterindereinheit...