I have been very satisfied with the DMSO I bought from Robert L. Brock at DMSO.net his DMSO is 99.996 % pure. That is good enough for me. All I could find local is 99 % and that leaves 1% of unknown. That might be fine for a silver coin but not for DMSO. I know this stuff is pure because it freezed right at the tempurature of the chemical. It was 65 degrees and it was frozen solid. The freezing point is 65.4 degrees of pure DMSO.