Lichen spot tests

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Simon Horsnall
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Lichen spot tests

Post by Simon Horsnall » Fri Feb 12, 2016 8:56 am

This is more of a hypothetical question than something I am planning in the near future but looking at the hypochlorite test on lichens. The BLS website suggests that sodium hypochlorite may give false results because of the sodium ions present and suggesting calcium hypochlorite as the suitable reagent. However, further down the page it suggests sodium hypochlorite.

Does sodium hypochlorite produce false results because of the sodium ions or is it suitable for spot tests?
If calcium hypochlorite has to be used, can anybody suggest a source? The BLS recommended source, Milton Sterilising Fluid, is sodium hypochlorite.

Many thanks

marksteer
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Re: Lichen spot tests

Post by marksteer » Mon Feb 15, 2016 9:46 pm

Simon Horsnall wrote:This is more of a hypothetical question than something I am planning in the near future but looking at the hypochlorite test on lichens. The BLS website suggests that sodium hypochlorite may give false results because of the sodium ions present and suggesting calcium hypochlorite as the suitable reagent. However, further down the page it suggests sodium hypochlorite.

Does sodium hypochlorite produce false results because of the sodium ions or is it suitable for spot tests?
If calcium hypochlorite has to be used, can anybody suggest a source? The BLS recommended source, Milton Sterilising Fluid, is sodium hypochlorite.

Many thanks
Not sure about test on lichens but I think you should be able to find Calcium Hypochlorite at swimming pool chemical suppliers - it seems to be available on Amazon etc
'The more I know the more I realise I don't know'

Steve
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Location: Sheffield, Yorkshire

Re: Lichen spot tests

Post by Steve » Sun Feb 21, 2016 10:21 pm

Hi Simon.
It's not just C reagent that can be a problem. I went out on a lichen walk with the local expert, who tested a yellow crustose lichen with K (Potassium hydoxide) reagent, and pronounced it to be Candelariella (K -ve). I checked myself with my own K reagent and the lichen turned bright red - as did the expert! It was Caloplaca citrina! His K reagent was old and had turned to potassium carbonate. So you should always check K on litmus or on a bit of Xanthoria parietina (should turn red). I think you should do the same with C reagent - if it turns Xanthoria parietina red then it contains sodium hydroxide and is no good. (If I remember correctly :lol: ). Another complication is that there seem to be plenty of chemotypes ie species varieties which react in an aberrant/"wrong" way to K or C. Also, some of these reactions are very fleeting and can be easily misinterpreted. You also might want to soak up the reagent on a bit of filter paper/tissue to see the reacted reagent, as it's not always easy to see on the lichen itself. P reagent seems unstable and dangerous and I don't even consider it. At the moment I just use fresh K reagent and nothing else. But I'm just looking at Cladonia.
My motto with fungi is "Nothing is easy" (Jethro Tull). And not just fungi. But anything worthwhile always takes a bit of work!
Steve

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