A new test kit is also available from dancesafe.org. This is aimed specifically at the American market and makes it easier to to see the difference betweem DXM and MDMA. This kit uses the Mecke reagent. to order this or see the other Dancesafe kits go to
http://www.dancesafe.org/testingkits/orderform.php
Dancesafe claims that their kit is "Superiour to Marquis". This is misleading. Mecke is better at differentiating between DXM and MDxx than Marquis, but is actually less effective at discriminating between MDxx and other compouns. All tests should start with Marquis and use this result to cross reference.
Can't the marquis reagent test for DXM?
Yes although it can be hard to distinguish the difference from this and MDMA as MDMA can go black. If there is ONLY DXM in a pill you will NEVER see the typical purple of an Ecstasy like substance.
A DXM reaction will be slower to the MDxx reaction and will typically be a grey/black rather than the purple black of MDxx. Don't let an initial puff of smoke make you think you automatically have DXM (see above). DXM is most common in North America and therefore it is a good idea to purchase a Dancesafe Mecke reagent if your major concern is distinguishing between DXM and MDMA. But remember to combine it with a Marquis reagent for true peace of mind.
Basically you can only order the Mecke kit online from Dancesafe at the moment.