Tiny amount of powder. like enough to fit in a drop or two.
Reccomend a white, ceramic plate like a saucer. Put the molly on the edge of the inside lip and then apply a drop so that it flows onto the powder down the lip. Color should go black quickly. DXM fizzles, I would say if this happens, test a slightly larger amount and see if the reaction produces a wisp of vapor. I know that bk-MDMA will turn a vibrant yellow color when marquis is applied.
100mg known pure bk-MDMA was donated to a guy offering to test people's stuff for $5, and it was more than needed to see the color reaction with it among 5 different reagents. I was curious, and felt he would benefit from having a clean sample of it tested. Marquis was the most distinctive reaction though, reaction was rapid. "Molly" in many cases does not always mean MDMA, it stands for molecule, and in the end I consider bk-MDMA a better example of "molly" mostly because purity is often much more pure than MDMA molly, and I have fed people bk-mdma as bk-mdma, and they have tried to tell me that it was MDMA. The big difference is that MDMA is much more abrasive on the body, wheras most get much less of a comedown from bk, but bk also hits earlier and more gradually, the dose is a little higher, duration a little shorter, less love more hedonism. A worthwhile substance, but I would never pay MDMA prices for it.