Testing Drug Purity

[pharmapsyche]

A commercially produced pharmaceutical is almost pure. In contrast, the purity of illegal drugs is ofcourse, unspecified: the user may get the supposed drug, a diluted verison of the drug, or an entirely different substance.
Every illegal drug has been sold in bogus forms at some point in history. Almost all street cocaine, for example is heavily diluted with other substances. In a study of purported mescaline, ever sample proved to be something else (usually LSD or PCP). It is very easy to pass off cheap pills and powders as a similar-looking drug.
Because synthtic drugs dicerted from pharmaceutical sources have the greatest purity, many illegally made synthetics are made to look like them, with fake labels and packaging. Even natural drugs such as psilocybin may be store-bought mushrooms dusted with amphetamine or another cheap stimulant.
The low purity of illegal drugs also results from sloppy manufacturing. Illicit labs have little regard for precision, proper storage, or avoiding contamination. The result is the production of chemicals of which drug makers have little knowledge.
The user is very lucky if a synthetic illegal drug is 90% pure- and it's purity is more likely to anywhere from 60% down to 10%, or it may contain none of the supposed drug at all. What are the other ingredient, you ask? They can be anything from fillers such as cornstarch and talcum powder, to cheaper substances that mimic the drugs effects, such as local anesthetics, caffeine and strychnine.
Drugs are "cut" to increase volume by mixing the pure drug with other, cheaper substances. This is usually done with a sharp knifeor a razor blade, finely chopping and mixing the powders so that it looks like a uniform substance. It is easy to dilute powders in this way, but drugs in hard chunks are more diffcult to combine with other substances without the result being quite obviously a mixture-the chunks have to be broken up to mix them, and even then the final product looks clearly diluted. For this reason, rock-like cocaine is often perferred, and even heavily cut cocaine will be with a few rocks to make it look more authentic.

There are many tests of drug purity, ranging from sophisticated laboratory methods to relatively crude appraisals. Some commerical laboratories will provide an accurate and confidential analysis of a drug for a small fee.
A very effective home method is to check the melting point of a drug. Using an apparatus called a hot box, a flask of mineral oil is placed over a flame. A thermometer is placed in the oil to measure it's temperature. Suspended in the oil is a test-tube containing a small amount of the drug. When the drug begins to melt, the temperature is noted. Different chemicals melt at very specific temperatures.
This procedure is so precise that even the percentage of adulteration can be determined. For example, if about 25% of a sample melts at 187 degrees and the rest melts at 203 degrees, it can be assumed that the sample is 25% cocaine and 75% lactose.

Melting points in degrees Celsius
Cocaine freebase-98
Lidocaine-127
MDMA-148
Mannitol-165
Methamphetamine-170
Heroin-173
Quinine-177
Cocaine hydrochloride (powder)-187
Lactose-203
Vitamine B powder-224
Caffeine-237
PCP-243
Ephedrine-247
Baking Soda-270

Paul Gahlinger, M.D., Ph.D.

[scitech]

First of all, its simple enough to get the right apparatus to check melting points that the setup SWIY suggests is just silly. Its called a thiele tube kids, you pour some oil in there, heat the sidearm and watch your capilary tube ruberbanded next to your thermometer until you see it melt

Second: an impure substance will always melt lower then any of its components, going down as low to what is known as the eutectic point. This effect is very evident in pipe solder: the alloy of the two components melts drastically lower then either of the components. You wont see anything "melt away" reliably at the correct temperature, this is NOT a distillation. Period. However, you are correct in stating that the purity of a material can be judged by its melting point/range. However, there is no definite formula SWIM can remember....so its mostly assumption, depending on the chemical and the impurities.

You should also note that not all compounds will melt before being oxidized: caffeine and sucrose are two commonly encountered "cuts" that will oxidize before or at thier melting points

Beyond that...decent post, and welcome ^_^

-sCi

[radiometer]

Also, some compounds may have a range of melting ponts:

Only the anhydrous form [of MDMA] has a sharp mp; the published reports describe all possible one degree melting point values over the range from 148-153 ° C. The variously hydrated polymorphs have distinct infrared spectra, but have broad mps that depend on the rate of heating.

http://www.erowid.org/library/books_online/pihkal/pihkal109.shtml

[fatmanstan]

Hey, hopefully someone here reading this may be able to answer a question for a friend. Mr. "Q" acquired some 2C-I from two separate sources. Using a temperature calibration device, he wanted to see how pure the two samples were. Approx 1 mg of each sample was heated until melting, actually, only the one really melted, the other kind of sublimated. Regardless, the first sample, from the not-so-on-the-up-and-up source darkened and began melting at approx 228C, and was completely melted at approx 239C.

The other sample was still white crystals till approx 242, then began to slightly darken. Melting (sublimation, ie disappearing mass) started around 245C and by 248C was completely gone.

Q has no concerns about the second sample, but what does the first set of results mean? Is there any way to guage purity based on relative melting point? The stated MP of 2C-I is 246-247C.

Thanks for any help.