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Color change reactions of Hofmann reagent with LSD

What is Hofmann reagent?

Hofmann reagent test (often misspelled as “Hoffman” or “Hoffmann”) is named after the inventor of LSD-25, the Swiss chemist Albert Hofmann. It is primarily used for the identification of psychedelic indoles such as lysergamides and tryptamines. Together with Ehrlich’s reagent, it forms the foundation of testing for LSD, DMT, and their derivatives.

In scientific literature, this reagent is generally referred to as the Van Urk reagent or p-DMAB-ts (Test Solution). It contains sulfuric acid, p-DMAB (para-dimethylaminobenzaldehyde), and ferric chloride. PRO Test uses a slightly modified formula, which offers increased sensitivity and faster reaction time.

This colorimetric test is a modification of the Ehrlich reagent, characterized by a broader range of color reactions that allow for distinguishing many common indoles — for example, melatonin from LSD and DMT. While the Ehrlich reagent is more popular than Hofmann’s, it typically produces a single color with both psychoactive and non-active indoles. In contrast, Hofmann reagent reacts with non-lysergamide indoles by turning yellow-green, whereas lysergamides are expected to produce a deep blue color. However, exceptions do occur and will be discussed below.

Color reactions of Hofmann reagent with LSD

The Hofmann reagent serves as a simple colorimetric test for the preliminary identification of indoles, and as such, carries a risk of ambiguous results. In this article, we focus on the range of reaction colors observed with LSD.

A deep blue color, sometimes with a hint of purple, is the typical reaction of the Hofmann reagent with LSD. The reaction usually occurs within a few to several minutes. We recommend observing the reaction for up to 60 minutes. Using a larger sample or one with a relatively high concentration of LSD increases the chances of producing a strong deep blue reaction. Adding a drop of water or alcohol may also help.

Strong reactions of Hofmann reagent with LSD

A deep blue color, sometimes with a hint of purple, is the typical reaction of the Hofmann reagent with LSD. The reaction usually occurs within a few to several minutes. We recommend observing the reaction for up to 60 minutes. Using a larger sample or one with a relatively high concentration of LSD increases the chances of producing a strong deep blue reaction. Adding a drop of water or alcohol may also help.
Using a small LSD sample — for example, 1/8 of a blotter (a piece of blotter paper, commonly referred to simply as a "blotter") — usually results in a weaker reaction. It may appear grayish-blue. It's important to remember that the intensity of the reaction is not particularly significant. Even if only the sample itself changes color as described, it still clearly indicates a positive result.

Weak reaction of Hofmann reagent with LSD

Using a small LSD sample — for example, 1/8 of a blotter (a piece of blotter paper, commonly referred to simply as a “blotter”) — usually results in a weaker reaction. It may appear grayish-blue. It’s important to remember that the intensity of the reaction is not particularly significant. Even if only the sample itself changes color as described, it still clearly indicates a positive result.
For various reasons, such as composition of blotter paper or gel used as LSD carrier, but perhaps also due to sample potency, the Hofmann reagent result can sometimes look more purple than blue. This is a fairly common occurance and should be still considered a positive test result, indicating the presence of a lysergamide, such as LSD.

Purple reaction of Hofmann reagent test with LSD

For various reasons, such as composition of blotter paper or gel used as LSD carrier, but perhaps also due to sample potency, the Hofmann reagent result can sometimes look more purple than blue. This is a fairly common occurance and should be still considered a positive test result, indicating the presence of a lysergamide, such as LSD.
Since the Hofmann reagent test contains a relatively large amount of sulfuric acid, it’s not surprising that it may react with the paper or dyes present in blotters or LSD gels. Additionally, when using crystalline reagents, the reaction gradually spreads from the sample toward the edges of the reagent drop. As a result, the initial deep blue color change may appear more gray than blue. In such cases, we recommend extended observation.

Grey reaction of Hofmann reagent test with LSD

Since the Hofmann reagent test contains a relatively large amount of sulfuric acid, it’s not surprising that it may react with the paper or dyes present in blotters or LSD gels. Additionally, when using crystalline reagents, the reaction gradually spreads from the sample toward the edges of the reagent drop. As a result, the initial deep blue color change may appear more gray than blue. In such cases, we recommend extended observation.
Thanks to members of the reddit.com/r/reagenttesting community, it was discovered that some blotters contain an unidentified substance that causes a brown reaction with the Hofmann reagent. Together with user /u/Ok-Bedroom495, we found a solution to this issue. Before applying the Hofmann reagent, simply soak the sample in a small amount of alcohol, or add 1–2 drops of alcohol just before adding the reagent. This way, the reagent will almost instantly produce the expected dark blue color.

Brown color reaction of Hofmann reagent with LSD

Thanks to members of the reddit.com/r/reagenttesting community, it was discovered that some blotters contain an unidentified substance that causes a brown reaction with the Hofmann reagent. Together with user /u/Ok-Bedroom495, we found a solution to this issue. Before applying the Hofmann reagent, simply soak the sample in a small amount of alcohol, or add 1–2 drops of alcohol just before adding the reagent. This way, the reagent will almost instantly produce the expected dark blue color.

When is it best to use Hofmann reagent test?

The Hofmann reagent is best used alongside the Ehrlich test. No single reagent is 100% reliable, so make sure you have several reagents in your LSD testing kit or DMT test kit. Based on thousands of lab test results, it can generally be assumed that a sample confirmed to contain LSD has a negligible chance of also containing a non-trace amount of another psychoactive substance. 

If you’re testing lysergamides or tryptamines and the result is negative, be sure to learn how to avoid unwanted phenethylamines such as NBOMe or DOC. To rule out their presence, you should use at least two of the following reagents: Marquis, Mecke, Liebermann, or Froehde — all of which are available in our LSD reagent kit or DMT testing kit. When using reagent tests to rule out phenethylamines, look for an immediate and vivid color change. Do not confuse a true positive reaction with a false positive — a weak, slow burn of organic material caused by the corrosive nature of some reagent tests. 

Sources used in this article:

  • https://en.wikipedia.org/wiki/Ehrlich%27s_reagent
  • https://www.reddit.com/r/ReagentTesting/comments/1ieb2vc/hofmann_turning_green_gray_with_dark_blotter_lsd/
  • https://www.reddit.com/r/ReagentTesting/comments/1iaxeni/need_help_determining_my_acid_tabs_are_real/
  • https://www.reddit.com/r/ReagentTesting/comments/1l4ddv9/hofmann_turning_grey_with_lsd/
  • Photos submitted directly to PRO Test

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