Some amazing artifacts - original standard weights for the pound and troy pound. The troy pound is made from pure platinum! A correction.. The silicon isotope used is 28, not 29 as stated in the video! Sorry! The Professor is joined at the Royal Society by none other than Michael from Vsauce - http://www.youtube.com/user/vsauce More chemistry at http://www.periodicvideos.com/ Follow us on Facebook at http://www.facebook.com/periodicvideos And on Twitter at http://twitter.com/periodicvideos Periodic Videos films are by video journalist Brady Haran With thanks to the Royal Society: http://royalsociety.org/