Shambles
Bluelight Crew
I'm not a chemist, nor even able to guess at what a chemist's answer might be, but I do know that any residual impurities would have to be several times the potency of LSD in order for them to have any effect whatsoever. If you had a blotter that supposedly held 100 micrograms of 75% pure LSD (and nothing else), then the impurity / impurities would need to be active at <25 micrograms in order to have a discernible effect on the trip.
There aren't too many chemicals active at doses of under 25 micrograms. Placebomine, however, is highly active at doses of 0mg. So draw your own conclusions.
As stated above, it's possible for 'LSD' to not be LSD, kinda:
But other than that? Set, setting and dealer bullshit.
This. Nice to see a bit of common sense and logic here amongst all the magic, mystique and mythology. I think a lotta people tend to forget just how potent a substance LSD is compared to almost any other substance imaginable. The amount of impurity in even the 'dirtiest' acid would be so minute it's barely conceivable it could have any truly significant effect on a trip. Set & Setting all the way.
That and the fact that low-dose acid can feel a bit weird anyway at times and if it's not such great quality acid your 100ug or whatever may actually only be a fraction of that so you never really get to where you expected to be and end up in that weird not-quite-tripping-properly-but-too-far-from-sober-to-make-sense-of-the-fact place that's just a bit uncomfortable in general.