Archived posting to the Leica Users Group, 2009/01/08[Author Prev] [Author Next] [Thread Prev] [Thread Next] [Author Index] [Topic Index] [Home] [Search]
Hi! Thorium is?the second in the ?Actinide element Series - that contains Uranium, (Lantinum starting it's own S eries ). Many lenses (Apo-Lanthars) contaied the oxide of these elements - ThO2 for eample in the Aero-Ektar, and gives glass Low Dispersion - ?High Refractive Index properties. It's use ?was very good at the time. The oxides are fairly harmles , but Thorium metal is very radioactive and is looked at as a source of reactor fuel!! Th 232 , the most common goes throuh a number of alpha and beta decays over a thousand years or so before it turns to lead, Pb - Who says one element can't be turned into another naturaly?? :-) I wonder if after a thousand years someone will test these lenses, and see if the Ref. Index has changed because half the ThO2 will be PbO2? ----- We'll never know! Ed - I Just like chemistry!