Mecke reagent
The Mecke reagent is used as a simple spot-test to presumptively identify alkaloids as well as other compounds. It is composed of a mixture of selenous acid and concentrated sulfuric acid, which is dripped onto the substance being tested.
The United States Department of Justice method for producing the reagent is the addition of 100 mL of concentrated sulfuric acid to 1 g of selenous acid.
| Substance | Color |
| Chlorpromazine HCl | Blackish red |
| Codeine | Very dark bluish green |
| Diacetylmorphine HCl | Deep bluish green |
| Dimethoxy-meth HCl | Dark brown |
| Doxepin HCl | Very dark red |
| Dristan | Light olive brown |
| Exedrine | Dark greyish yellow |
| LSD | Greenish black |
| Mace | Dark greyish olive |
| Methylenedioxyamphetamine HCl | Very dark blue |
| Mescaline HCl | Moderate olive |
| Morphine monohydrate | Very dark bluish green |
| Opium | Olive black |
| Oxycodone HCl | Moderate olive |
| Propoxyphene HCl | Deep reddish brown |
| PMMA | Pale olive green |
| PMA | Pale olive green or light green |
| Sugar | Brilliant greenish yellow |