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Comment by knoepfle | Hacker News Reader

"Pure acid" isn't quite right; it's an aqueous solution with a pH of zero. Zero isn't a special value. You can have negative pH (cf. http://pubs.acs.org/doi/pdf/10.1021/ed083p1465).

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Yep. Iron Mountain Mine makes this place look pretty wimpy. pH -3.6, temps above 47C, boiling sulfur dioxide, etc, etc. Dunno if the pH -3.6 they sampled has anything living in it.

Well, based on this article it either was not tested for life or it didn't have it.

There are at least 5 extremophile species in the biofilms at Iron Mountain, according to the sequencing done at the JGI[0][1] in the early 2000s. They've continued[3] sequencing more samples form the mine ove3r the last decade, so I suspect the actual number of known species is far higher.

The effort to sequence their genomes was one of the first attempts to directly sequence an environmental sample without first culturing and separating the individual species (with environmental samples, the separation happens during assembly). This is important when there no known way to culture the bacteria/archaea under investigation.

[0] Disclosure: I provided software support for this project.

[1] http://jgi.doe.gov/news_2_2_04/

[2] http://genome.jgi.doe.gov/?core=genome&query=acid%20mine&sea...

This is one of those epic replies[1] that makes HN so neat. Wondering whether anything lives in Iron Mountain's hostile environment? No worries - the guy who provided software support for that project will elucidate the matter (with links to boot!).

[1] Perhaps the most epic of epic replies was Colin Percival's legendary snorter: https://news.ycombinator.com/item?id=35079

I don't think they actually found living microbes in the pH -3.4 wash, though.

Ferroplasma acidarmanus lives as a biofilm directly in the acid streams[1][2]. I'm not sure what the pH is in those specific areas, but it's very low (below 0). Compared to abiotic leeching of the iron pyrite in the mine, Ferroplasma greatly speeds up the reaction by using ferric iron as a catalyst:

    4Fe2+ + O2 + 4H+ → 4Fe3+ + 2H2O 
    FeS2 + 14Fe3+ + 8H2O → 15Fe2+ + 2SO42- + 16H+

The natural pyrite ore does not produce the extreme acid runoff. The problem starts when we mine out an area and oxygen is introduced, which is used to create Fe3+. This allows a much more efficient conversion of pyrite into a lot of acid.

This extremophile excretes pure sulfuric acid.

[1] https://microbewiki.kenyon.edu/index.php/File:Ferroplasma_1....

[2] https://digital.wwnorton.com/ebooks/epub/microbio4/OEBPS/ima...

Wow. Thanks, I wasn't aware of Ferroplasma acidarmanus or any other organism that excretes strong acids.

Thank you, we've updated the headline.

What would be the threshold for calling something "pure acid" (in the acid/base sense ;) )?

Well not in terms of pH, but there are several acids that can exist as a pure liquid, undiluted by water. Pure vinegar, undiluted by water, is called glacial acetic acid. It is something that can be bought from a chemical company. Because there is no water, there isn't really a pH. That doesn't mean it isn't incredibly hazardous, though.

>Because there is no water, there isn't really a pH.

Could you elaborate? Wikipedia doesn't seem to suggest water is necessary (it talks about moles per unit volume) but I may be misunderstanding something.

I'd say you have moles per unit volume of H3O+ ions. These form as the combination of H+ ions (readily present in copious amounts of acid) and crucially, H2O molecules.

The definition of pH is pretty much a measure of the proton concentration of things dissolved in water. You can look at similar measures in non aqueous solution but then it doesn't fit the definition properly.

On the other hand, pure oleic acid isn't especially toxic. It's a major component of Lorenzos oil.

Nuthin but protons?

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