I have a reagent bottle with an unknown chemical that came with some other lab gear about 30 years ago, I stumbled on it again when clearing out some old stuff.

It is a standard brown glass Merck of about 250ml size. It has no label and never had any indication of a label and I do not know if it is the original bottle.

The powder is a fine dark free flowing crystalline solid. It is DARK green with a gold iridescent sheen when in bright light, something like a butterfly wing or some anti-forgery inks on banknotes.

Yet if I wet a very small portion it dissolves completely and creates a vivid dark blue solution that dries blue in a thin film. If the crystals dry in a clump they form a smutty dark green gold pasty lump that is reminiscent of the original bulk colour.

I had to hand some potassium permanganate crystals and when I mixed a pinch of the two together and added a drop of water a gas evolved and the colour seemed to be somewhere between the permanganate and the mystery chemical blue when spread on paper. Adding a few drops of acetic acid seemed to have no effect.

Can anyone think of an obvious candidate or some simple experiments that could be used to determine the material?


closed as too broad by Mithoron, airhuff, Jan, Nilay Ghosh, Tyberius Nov 8 '17 at 15:25

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    $\begingroup$ A picture would really help IMHO... $\endgroup$ – paracetamol Nov 7 '17 at 15:25
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    $\begingroup$ In general, I don't advise experiments on unknown substances, particularly because it is unknown. $\endgroup$ – Zhe Nov 7 '17 at 15:44
  • $\begingroup$ @Zhe But we wouldn't know what we're dealing with until we "experiment" >:-D $\endgroup$ – paracetamol Nov 7 '17 at 16:08
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    $\begingroup$ That's true, but frankly, from a safety perspective, that's strongly ill-advised. Will your analysis liberate hydrogen cyanide? Probably not, but for unknown substances, without a lot of context, you can't really know for sure. $\endgroup$ – Zhe Nov 7 '17 at 16:46
  • $\begingroup$ The pasty lump seems to indicate an organic molecule. Obviously with quite an extended conjugation. Why not to proceed with analysis? Obviously with an eye at safety first. I mean really go through solubility test, Lassaigne. ... It seems you are in a lab.... $\endgroup$ – Alchimista Nov 7 '17 at 21:00

I worked for a time with squaraine dyes that were often greenish in the crystalline state, but ink-blue when in solution.

Squaraine dyes

However, I would suggest that you take an analytical approach to identifying this compound. Have you done any NMR, IR or even UV/Vis spectroscopy? Elemental analysis?

These would be a much safer way to go about identifying the mystery compound.

Good luck, and I'd love to know what you discover!

  • $\begingroup$ Cool, never heard of these but it is a likely candidate. The colour shifting seems to be common with them depending on solvents and concentration - chm.uri.edu/levinegroup/documents/pub2.pdf $\endgroup$ – KalleMP Nov 9 '17 at 4:53

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