http://www.basicchem.com/ or Univar.com for the big stuff if you're going to be using a tonne quantities
Otherwise if its just for passivating lab glassware you can buy lab scale quantities from places like http://www.sigmaaldrich.com/united-states.html or any of the usual lab suppliers
http://www.grainger.com/Grainger/wwg/start.shtml also seem to stock nitric acid as well
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