> with('ScientificConstants'); > GetElement('Na'); ... atomicweight = ([value = 22.989770, uncertainty = 2.*10^(6(, units = u]), ... So if I do the following, I expect 22.989770 (grams/mol) > evalf(Element('Na',atomicweight)); -26 3.817543727 10 What is happening here? Why does "atomicweight" mean one thing in one context and another in another? Cheers Geoff Russell