Reagent testing: what Marquis, Ehrlich, Mecke and Simon’s each tell you (and what they don’t)

Colour-change reagent kits are the cheapest, most available harm-reduction tool, and the most misread. They are presumptive (they narrow down an identity), not confirmatory (they cannot prove purity or dose). Here is what each is actually for. The common reagents - Marquis: the broad first screen. Different colours point at broad families (e.g. a fast dark purple/black is the classic MDMA-class response; other colours point elsewhere). It tells you a family, not a compound. - Mecke and Mandelin: run alongside Marquis to disambiguate — the combination of colours across two or three reagents is far more informative than one. - Simon's: distinguishes secondary amines (MDMA reacts) from primary amines (MDA does not), so it separates two things Marquis alone cannot. - Ehrlich: detects indoles (the LSD/tryptamine family) — useful for the opposite question, "is there an indole here at all". The three things reagents cannot do 1. Tell you how much. Colour intensity is not a dose; a reagent cannot measure strength. 2. See a masked or minority adulterant. A reagent reacts with whatever is most reactive; a dangerous component present in a small amount can be hidden by a benign bulk one. This is the "false-negative" that kills. 3. Detect fentanyl. Reagent colour tests are not a fentanyl test — use dedicated fentanyl test strips (separate thread) for that. Always: scrape a tiny sample onto a white ceramic plate, never test in the bag, and compare against a current colour chart. Mechanism and the multi-reagent matrix: https://wiki.soapbox.community/wiki/Colorimetric_Reagents_and_Presumptive_Chemical_Testing Kits and charts: dancesafe.org