Einstein you have peeked my interest and brought up a question I had never thought to ask thru 1/2 a dozen chemistry classes. How do we determine a mole of anything if there is no reference of weight. If I measure 12 grams of carbon 12 I have 1 mole of carbon 12. How do I measure it in a weightless state. I can't count molecules to 6.02 x 10^23 and then say I have 1 mole and therefore 12 grams of carbon 12. I need moles and grams to do stoichiometric calculations. For 12 years I had Ksp's, enthalpies of formation, moles, and grams that let me do my job. I never considered having to think about them without weight. I had the same professor for 4 classes and he gave me a CRC handbook. I've never considered that the book may be useless in space or on another planet. I feel that I must be missing something and weight as determined by gravity is not the only consideration. I am irritated by this thought. I has been 15 years since I left that job and I'm sure I have just forgotten something. Or maybe it's something I never knew. I've come to depend on Darby's input to some of the questions posted on this site and I hope he has something this time too. I just think it bothers me that I never thought of it before. Stupid Gravity.