"Quote:
Distinguishing between mdma and meth is the main reason people buy the testing kits in the first place.
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Unless of course there is a mixture of both present in a tablet. It is sometimes possible to tell, but mostly, the darker color of the MDMA reaction will dominate and the lighter orange color (marquis) may not be seen. Mandelin is possibly the better reagent to use as the meth reaction is usually very fast, although it's not fool proof either"
From another thread