||Gently heating a small sample of cocaine on a piece of aluminum foil is an imprecise street test (called the "foil test" or "burn test") that can provide a rough indication of the purity of cocaine. However, one needs to have a good sense of how cocaine looks when burned on foil compared to how materials that are used as cuts look in order to use this method.|
Most street cocaine contains a combination of coca alkaloids and a small amount on foil will burn off completely when a flame is applied beneath it, leaving behind a dark reddish-brown stain and only a bit of residue (which can be detected by wiping a finger across the stain). Pure pharmaceutical cocaine will not leave much of a stain or residue. In comparison, other substances can leave black or brown residue, will bubble, can produce particular identifiable smells when burning, or will not burn at all. For example, baking soda and talc will not melt, vaporize, or decompose when a flame is applied from below.
According to The Pleasures of Cocaine, the following are some of the reactions of common cocaine cuts to the foil/burn test:
There are additional street tests for checking purity such as the "bleach test" (or "clorox test"), where the manner in which a sample dissolves in a glass of bleach can provide some information about its composition to an experienced eye. However, most people find commercially available cocaine purity tests such as the "EZ Test White" to be a simpler approach toward getting a rough sense of the purity of material.
While some adulterants in illicit cocaine are fairly innocuous, others, such as levamisole, have been associated with a higher incidence of reported adverse effects.
Cocaine Adulterated with Levamisole on the Rise (Status as of Sep 2009)
- Mannitol: Melts and evaporates with little visible fumes and leaves no residue.
- Inositol: Melts, then burns or decomposes to a black ash.
- Lactose: Bubbles, caramelizes, and decomposes to a black ash, while producing a sweetish-smelling smoke like the odor of toasting marshmallows.
- Dextrose: Same responses as lactose.
- Pemoline: Melts, produces white fumes with burningplastic odor and leaves golden-brown stain.
- Procaine hydrochloride: Melts, producing much white fumes with mild chlorine odor. The molten mass turns yellow, progresses to dark gold and leaves a golden-brown stain.
- Procaine (free base): Melts quickly with little visible fumes and leaves no residue.
- Butacaine sulfate: Decomposes with much fumes and a faint burning rubber or gunpowder odor and leaves a thick black ash.
- Methedrine (Methamphetamine): Melts and vaporizes much like cocaine, but sizzles and pops. Leaves no residue.
- Yohimbine hydrochloride: Melts, producing heavy white fumes with indole odor (a fetid odor with a slight pungency like moth flakes). The molten mass turns golden-brown and disappears, leaving a black stain.
- Talc: Does not melt, vaporize or decompose.
- Baking soda: Does not melt, vaporize or decompose.
- Boric acid: After somewhat more heating than is required to decompose cocaine and most other cuts, it will bubble and fuse to a solid lump, but not decompose.
- Epson salts: Does not melt, vaporize or decompose.