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?

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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!

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  • $\begingroup$ 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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