Crystals from confluentic acid??

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Dave Lamacraft
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Crystals from confluentic acid??

Post by Dave Lamacraft » Thu Jul 23, 2020 4:21 pm

Hi,

I've been dabbling in the world of saxicolous lichens for a change and think I have Lecidea confluens, maybe. One of the most obvious features under the microscope was the formation of some pretty spectacular crystals with the addition of K, see pics. There is no mention of this in LGBI that I can see, but I was thinking if my tentative ID is right, then maybe it's a reaction with confluentic acid....?

Thanks v much

Dave

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AlanFUSA
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Re: Crystals from confluentic acid??

Post by AlanFUSA » Thu Jul 23, 2020 5:13 pm

Hi Dave:
Species containing confuentic acid produce numerous oil droplets with KOH. I wrote a short article about this in the BLS Bulletin in c. 1990. Apparently, NaOH produces crystals, but I haven't tested this myself. Could it be that you have NaOH not KOH!
Alan

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Re: Crystals from confluentic acid??

Post by AlanFUSA » Thu Jul 23, 2020 5:29 pm

The confluentic acid article is in British Lichen Society Bulletin 70: 31. 1991

Dave Lamacraft
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Re: Crystals from confluentic acid??

Post by Dave Lamacraft » Thu Jul 23, 2020 5:58 pm

Thanks Alan. Well, that's intriguing, I've just checked the ingredients of the caustic soda I use and it is indeed NaOH! So it seems my 'K' has actually been Na for a few years now! Life's full of surprises. Are KOH and NaOH completely interchangeable or it worth actually tracking down some KOH?

And, I guess that may still add up to evidence of confluentic acid....

Thanks again Alan, much appreciated.

Dave

Neil Sanderson
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Re: Crystals from confluentic acid??

Post by Neil Sanderson » Thu Jul 23, 2020 8:55 pm

Dave, there is also Mark’s new confluentic test, shine a UV torch on a K spot test and you will get a bright mauve fluorescence if confluentic acid is present.

KOH verses NaOH: there are a few differences, the confluentic acid as discussed, also Candelariella sp can go reddish, which is a bit confusing with Caloplaca but is not much like the K + crimson of actual Caloplaca K reactions. The plus is that NaOH is easy to get and presumably a bit safer, as it is a bit less reactive

Neil
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Dave Lamacraft
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Re: Crystals from confluentic acid??

Post by Dave Lamacraft » Fri Jul 24, 2020 12:36 pm

Thanks Neil, handy to know the K/UV, will give it a go later.

And handy to know about KOH vs NaOH, wikipedia suggested KOH is 'strongly exothermic' when mixed with water so, yes, NaOH may be safer!

Neil Sanderson
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Re: Crystals from confluentic acid??

Post by Neil Sanderson » Sat Jul 25, 2020 3:00 pm

Dave

NaOH is quite exothermic too so needs care too on mixing with water. CaOH lime wash should work as well and I did read a report of Caloplaca species going K + red on the application of lime wash to a wall, but obviously NaOH much more practical.

Neil
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Dave Lamacraft
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Re: Crystals from confluentic acid??

Post by Dave Lamacraft » Mon Jul 27, 2020 11:48 am

Thanks Neil. The K/UV worked ‑ a good mauve reaction.

Cheers

Dave

Neil Sanderson
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Re: Crystals from confluentic acid??

Post by Neil Sanderson » Mon Jul 27, 2020 12:27 pm

Yes it is a good easy test, confluentic is not common but the field test does solve a few difficult dichotomies. On trees Lecanographa lyncea/Lecanographa amylacea is especially valuable (the former with it and the latter without).

I have another excellent use for Mark’s other new test K/UV (Dry) + bright neon yellow for atranorin. Separating Megalaria pulverea which was Pd negative from Megalospora tuberculosa is not easy. Less sorediate Megalospora tuberculosa has distinctive white corticate tubercules (warts), AKA bald heads, but I have seen fully sorediate fertile material in Ireland, which would have been totally indistinguishable from Megalaria pulverea. Now the new atranorin test has come to the rescue. Megalaria pulverea always has atranorin, even when it is Pd -, and Megalospora tuberculosa does not. I have tested this on quite a few herbarium specimens and it works well Megalaria pulverea is K/UV (Wet) - and K/UV (Dry) + bright neon yellow, while Megalospora tuberculosa is K/UV (Wet & Dry) -

Neil
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Dave Lamacraft
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Re: Crystals from confluentic acid??

Post by Dave Lamacraft » Tue Jul 28, 2020 3:28 pm

That's funny, I'd just yesterday drafted a post on Megalospora tuberculosa, prompted by a very sorediate specimen of something I think is probably tuberculosa, which led me to thinking about the K/UV for atranorin, and just the UV itself. I'll finish it and post it anyway, might be of interest.

Cheers

Dave

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