For those brothers and sisters looking for a source of 99.9% n-Butane or Propane, consider R-600 Refrigerant from Eco Green Industries at http://ecogreenindustries.net/ .
$240 for Lp-5 tank of 99.9% n-Butane, and they ship. Hee, hee, hee, hee, awhooooooooooooooooooooooooooooooo!!!!!!!!!!!!1
Here are the Gas Chronograph/Mass Spectrometer results from a nationally certified third party forensic lab, which shows the usual green alligators and long necked geese at the parts per billionth level, but not at levels of health concern by any current standards.