what about this then?

[cyberkid]

mdxx turns the test straight to dark purple/black right?
Dxm turns the test to black over a longer period of time right?
well what if the two substances are in the same pill, it would already be black from the mdxx and ive heard that a combo of dxm and mdxx is dangerous.
i may have missed something so please dont flame me if i sound a cock!

 

[E'in]

DXM releases smoke when the chemical touches the powder. You must look very carefully.

 

[johnboy]

yes but "smoke" is also common in reactions with strong MDxx powder.
the question is really how can you detect a mixture of DXM and MDxx in the same pill? the answer is you can't, not with traditional reagent techniques anyways. with TLC plates you could.
but do people make such pills? no, none have been found so far, and it seems unlikely that anyone would. DXM was, and maybe still is, used as substitute for MDxx because it is cheap and legal and gives a "trippy" effect that an inexperienced user might think is MDxx. If a pill manufacturer has access to real MDxx it seems very unlikely they would bother putting DXM in the same pill.
so it's possible but unlikely. also keep in mind that if they do exist, one such mixed pill is unlikely to kill you. MDxx and DXM are contraindicated, but with one pill you will probably just end up a bit sick. It is in no way as lethal a combination as PMA/MDxx.
remember that most people who have died from DXM, and PMA for that matter, have been caning it, ie taking numerous pills and other chems and staying up for days. this is what will kill you...