it's 1 part formaldehyde, 9 parts sulfuric acid. not formaldehyde acid.
Simon's reagent is sodium nitroprusside (also known as sodium nitroferricyanide, Na2Fe(CN)5(NO)·2H2O), which is the active reagent. It is a test for secondary amines. Since secondary amines (e.g. R-NHCH3) have one and only one hydrogen on their amino group, I am guessing that the nitro group (nitro groups are good 'leaving groups' in inorganic chemistry) substitutes with that hydrogen and forms a drug-ferricyanide complex. ferricyanides are typically quite colored. Simon's reagent also contains sodium carbonate (Na2CO3) as a buffer, so that the reaction occurs under basic conditions.
btw - a secondary amine is one which is connected to two atoms that are not hydrogen. MDMA, methamphetamine, and cocaine (the usual subject of the Simon's reagent test) are secondary amines. MDA and amphetamine are primary amines, and give negative results with the Simon's reagent.
two others:
Mecke reagent: selenious sulfuric acid. Turns green in the presence of indoles, furans and compounds with phenolic oxygen.
Mandelin reagent: vanadyl sulfate. not sure what this one does.
i got those from a post i made on may 3rd, and in that post i said:
in the august 1990 issue of the journal of chromatography, there's an article (hayakawa et al) that describes how to test for methamphetamine using bis(2,4,6-trichlorophenyl)oxalate and hydrogen peroxide.
no one got it (i'm not surprised =)) but...
bis(2,4,6-trichlorophenyl)oxalate and hydrogen peroxide are two of the active ingredients in glowsticks. the other is a chromophore dye, such as 1,10-diphenylanthracene.
