I believe as well, that when you get it down to those anhydrous concentrations it (more so than always) makes more funky radicals as things oxidize when exposed to air. My darling mother (who went to berkeley in the 60's getting a PHd in chemistry) explained that they used to do the heavy duty filtering thing to crank the concentration way up for parties, but they had to very carefully store it under nitrogen and use it by adding to water quickly - if you did that everything was fine - if you let the high concentration stuff sit out it formed lots of funky free radicals with exposure to oxygen - which in turn produced the killer hangovers for which the stuff is legendary.

Having said that - anythign over 90 is just fine for stove fuel <img src="/forums/images/graemlins/smile.gif" alt="" />
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