On Thu, 15 Aug 2013 22:56:57 +0000, Dave Angel wrote: > To expand a little on that, the unit of "amount of something" is a "gram > mole", which is 6.2 **23 grams times the molecular (or atomic) weight.
The unit of amount of substance is mole. Gram-mole is an unfortunate synonym for mole. Unfortunate, because it looks like it should have dimensions of Mass, but it is actually a dimensionless number, and exactly equal to mole. As usual, we can blame the damn engineers and their sloppy, ad-hoc thinking for abominations like this: http://web.utk.edu/~dad/mole.html Also, you're quoting Avogadro's Constant incorrectly: it's 6.02e23, or if you prefer, 6.02*10**23, not 6.2**23, which is a factor of about 358581 too small. > My dad (research chemist) used to have to order supplies for his lab in > "ton moles", and he used some very small multipliers, since he usually > needed a kilogram or less in his lab. That's just sad. The supplier won't be counting out individual molecules, they'll be putting it on a scale and weighing it. So your dad had to convert the desired weight into a ridiculously impractical unit to place the order, and the supplier no doubt had to convert that unit back into mass in order to weigh it out and supply it. If you want a kilogram of X, why not order a kilogram of X, instead of converting it into megamol? Sigh, I know the answer to that question. "We've always done it this way." -- Steven -- http://mail.python.org/mailman/listinfo/python-list
