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I have long been an advocate of using strong bleaches such as Domestos and Parazone. Critics suggested that these were likely to be contaminated by sodium hydroxide and hence might give weak but confusing ‘K’ reactions in addition to C reactions. In order to reassure myself that such bleaches contained only trace amounts of hydroxide, I tried applying them to the thallus of
Xanthoriaparietinaand observed a weak reddish reaction. I assumed that this was due to trace contamination by sodium hydroxide but contented myself that these bleaches were still useful, especially because I couldn’t get any detectable ‘K+ yellow’ on species such as Lecanora chlarotera(suggesting that any contamination was very slight). Last night, stimulated by a Twitter exchange, I performed further experiments. Now we have a very sensitive K/UV reaction for atranorin (the K spot on e.g.
Lecanora chlaroteragives an intense yellow fluorescence). Could this be used to detect whether or not there is any hydroxide present in bleach? I applied both potassium and sodium hydroxide solutions to Lecanora chlaroterathallus and both gave K+ yellow, K/UV+ intense yellow. Now I applied Domestos and Parazone and, even when dry, those spots gave absolutely no hint of fluorescence. Despite proving that they are devoid of hydroxide, I find that these bleaches give a weak but distinct red reaction on Xanthoria parietina. This suggests that pure sodium hypochlorite (C) itself gives a reaction with (at least some) anthraquinone pigments. I also have a bottle of what claims to be pure sodium hypochlorite solution and this does the same (no K/UV+ yellow on L. chlarotera, C+ red on X. parietina). https://twitter.com/obfuscans3/status/1211336659264057344 https://twitter.com/obfuscans3/status/1211778307445968898 I dredged from my memory that Jack Laundon had reported C+ red reactions in
Caloplaca: Laundon, J.R. New British species of Caloplaca. Lichenologist 24: 1-5. At that time the phenomenon had not been previously reported and then seems to have been forgotten about subsequently. In my own notation, I consider
Xanthoria parietinato have the following reactions: K+++++ red-purple, C+ red, UV++++ orange.
My quibble wasn’t whether Domestos contained sodium hydroxide or not, but that it gives a red reaction. A few years back I was running a beginners’ session and provided them with KOH, Domestos, and Xanthoria parietina. “Does a spot of K give a reaction?” I ask. Yes! they reply delightedly. “Does C give a reaction?” Yes! they reply – leaving me looking sheepish. Same kind of problem with C and Lecidella elaeochroma. “That one with black fruits will go orange if you put bleach on it if it is the one I think it is.” said I. No reaction at all!
If you already know what something is then you won’t be doing the chemical test. If it is an unknown and you are working from a key then you can easily be misled. I rarely need to check the commonest species these days, and when I do and it doesn’t give the “correct” reaction I persist until it inevitably does. However, I am frequently confounded by material I am not so familiar with.
Here are a couple of snaps of Xanthoria parietina, Lecanora chlarotera and Lecidella elaeochroma with a spot of Domestos that was applied in the previous minute. Red Xanthoria, red spots in the Lecanora (due to a parasite) and pretty much unreactive Lecidella. Traps for the unwary.
on a related matter-
What UV torch are people using currently? I need an upgrade.
Happy New Year
Juliet
I agree with your quibble in the sense that it would be useful to know exactly what is going on and to describe the phenomenon accurately. Although I have presented my provisional results above, they still need checking further. Either an anthraquinone in Xanthoria parietinareacts red with hypochlorite or bleach IS contaminated with hydroxide and I have failed in my attempt to prove its absence. My reason for advocating strong bleach results from early experience with the Churchyard Group when some people would fail to detect any C+ orange with
Lecidella scabra(using value bleach). Ivan would come along with his gloopy Domestos and demonstrate that the same specimen was, indeed C+ orange. From then on, even if Domestos contained a bit of hydroxide contamination I was happy to use it for the strength of C reaction it gave. I find that different individuals of
Lecidella elaeochroma, even growing in the same mosaic-forming population, vary in their C+ orange reaction (and this can be seen very effectively by shining UV on to those mosaics where the ones that react strongly C+ orange give the strongest UV+ orange fluorescence). On the subject of UV torches, the Convoy S2+ with Nichia 365nm chip is the one that is remarkably powerful and useful even in the field. Bear in mind that it uses 18650 type batteries (not commonly available in ordinary shops). I bought a couple of rechargeable ones with a charger.
I think that I have demonstrated Jack Laundon’s C+ reaction in the apothecia of Caloplaca albolutescens(probably identical in this sense to C. teicholytawhich he mentions, and he may not have distinguished between them at that time). I will post the extract from Jack’s paper, then the apothecial margin of Caloplaca albolutescensin water, then in C and then in K.
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