Marquis Reagent: What It Detects, Color Chart and How to Read Results
Marquis is the broadest single reagent: instant purple-black for MDMA, orange-brown for amphetamine, and no reaction for fentanyl. Full colour chart, timing, and the false readings that fool people.
The short answer: Marquis is the broadest-spectrum reagent you can buy — it reacts with MDMA, MDA, meth, amphetamine, 2C-x, DXM, opioids and more, giving you a colour within seconds. It is also the most commonly misread. The colour is a clue, not a verdict: Marquis alone cannot confirm identity, and no Marquis reaction — or lack of one — tells you anything about fentanyl.
| Marquis colour | Likely substance | Confidence |
|---|---|---|
| Instant purple → black | MDMA / MDA | Strong (confirm with Simon's for MDMA vs MDA) |
| Orange → brown | Amphetamine, meth | Moderate |
| Yellow → green | 2C-B, 2C-I | Moderate |
| No reaction / slow | Possibly fentanyl, or a substance Marquis doesn't catch | Never treat as safe |
| Pink → deep red (slow) | Aspirin, some cuts | Weak |
The #1 mistake: testing one tiny crumb. Adulterants cluster — the "chocolate chip cookie effect" means a clean crumb proves nothing about the rest. Dissolve and test the whole portion you intend to use.
→ Marquis Reagent Kit ($25) · Full reagent colour chart · Marquis vs Mecke vs Froehde
What Is Marquis Reagent?
Marquis reagent is a chemical testing solution that produces specific color reactions when it comes into contact with various psychoactive substances. It was first discovered and tested in 1896 by the pharmacologist Eduard Marquis (1871-1944) for forensic toxicology, and it remains one of the most widely used drug checking reagents in the world.
Chemical composition: Formaldehyde (CH₂O) in concentrated sulfuric acid (H₂SO₄)
Why it works: The reagent reacts with specific functional groups on drug molecules, producing colored oxidation products. Different drug classes have different molecular structures, so they produce different colors.
What Marquis Detects (and What It Misses)
Marquis is a general-purpose screening reagent. It reacts with a wide range of substances but cannot distinguish between all of them. This is why it should always be used as part of a multi-reagent protocol.
| Substance | Marquis Reaction | Notes |
|---|---|---|
| MDMA / MDA | Immediate purple → black | The classic reaction, instant and unmistakable |
| Amphetamine | Orange → brown | Slower development than MDMA |
| Methamphetamine | Orange → red-brown | Similar to amphetamine, use Simon's to distinguish |
| Cocaine | No reaction / pale yellow | Marquis NOT reacting is actually useful, it rules out stimulant adulterants |
| Heroin | Purple → dark purple | Distinctive, but similar to MDMA, use Mecke for confirmation |
| Morphine / Codeine | Purple → dark purple | Opioid alkaloids react strongly |
| Oxycodone | Orange → brown | Slower reaction than heroin |
| LSD | No reaction / pale yellow | Use Ehrlich instead |
| Ketamine | No reaction | Use Morris + Mandelin |
| 2C-B | Yellow → green | Distinctive, one of the few substances that produces a green reaction |
| PMA / PMMA | No reaction | This is a critical safety signal, if a sample looks like MDMA but Marquis does not turn purple, you may have PMA, which has caused numerous fatalities |
| Mescaline | Orange → brown | Slow reaction, similar to amphetamine |
| DMT | Orange / brown | Distinct from LSD (no reaction) and psilocybin |
| Psilocybin / Psilocin | Orange → brown | Similar to DMT, use Ehrlich for confirmation |
| Caffeine | No reaction | Common adulterant, Marquis won't catch it |
| Aspirin | Pink → deep red | Slow reaction, can cause false positives in pressed pills |
The Important Signal: What Marquis Does NOT Do
Experienced testers know that a non-reaction from Marquis can be just as informative as a color change:
- White powder + no Marquis reaction: Could be cocaine, ketamine, or an inert adulterant like MSM or baking soda
- Pressed pill sold as MDMA + no Marquis reaction: MAJOR RED FLAG. PMA/PMMA does not react with Marquis. Numerous overdose deaths have occurred when people took pressed pills sold as MDMA that were actually PMA. If Marquis does not turn purple, DO NOT consume the sample.
- Clear liquid + no Marquis reaction: Could be GHB, GBL, or water. Marquis will not detect GHB/GBL, use specific GHB test strips.
How to Use Marquis Reagent
- Prepare a small sample, scrape a tiny amount (about the size of a match head) onto a clean ceramic testing plate or white surface
- Add 1-2 drops of Marquis reagent, the reagent is clear/colorless when fresh. If it has turned brown or pink, it has degraded.
- Observe the color change within 30 seconds, note the initial color and any changes over the next 2-3 minutes
- Record your result, take a photo if possible, especially if you plan to share with a community testing service for verification
Protect your connection while traveling
Marquis Reagent Shelf Life
| Condition | Duration |
|---|---|
| Unopened, refrigerated | 12-18 months |
| Opened, refrigerated | 6-12 months |
| Opened, room temperature | 3-6 months |
| Signs of degradation | Brown/pink discoloration, crystallization |
Marquis is particularly sensitive to light and heat. Always store it in a dark glass bottle in a cool place. Do not freeze, the sulfuric acid can crystallize.
Where to Buy Marquis Reagent
Marquis is the most widely available reagent and is included in most starter kits:
- TestKitPlus Marquis, at TestKitPlus: $25.00 CAD (individual bottle, ~50 tests; our catalog: $25.00)
- Starter 3-in-1 Kit, at TestKitPlus: $60.00 CAD (Marquis + Morris + Ehrlich, ~150 tests total; our catalog: $60.00)
- Complete 9-Reagent Kit, at TestKitPlus: $150.00 CAD (full lab setup; our catalog: $150.00)
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Kits Mentioned in This Article
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