DXM is a dissociative drug (in the same family as ketamine) which also has activity in the serotonin system. It is most popular in the US as it is readily found in some cough medicines but is also found as a white powder in other places.
Cough syrup cannot be tested with reagents because it contains a number of other chemicals such as water, sugars and colourings. Fortunately it is a legal product and also tends to have an ingredients list to warn about dangerous additives like chlorpheniramine and paracetamol (AKA acetaminophen in the US).
DXM reacts with reagent tests as follows. Slow reactions can be a bit confusing so we would recommend a minimum of two reagents but ideally three or more.
As an aside, reagent tests do not give “purity” readings but they do detect substitution and often adulteration, too.
|Gray > Black (slow)||Purple > Black||Bright Yellow||Green > Pale Blue (Fast)||Yellow|
The plus side of a slow reaction is that if a fast reaction to a different colour happens while you are waiting, you know that there is something else present.