[NHCOLL-L:3747] Re: Liquid-preserved charophytes

[John E Simmons]

There isn't really a short and easy answer to your questions, but in general
here is what I think you should do:

Assuming the prior preservative was FAA, there are the additional problems
that (1) alcohol evaporates faster from the solution than the formaldehyde
and acetic acid and (2) you don't know what the original ratios of
formaldehyde, alcohol, and acetic acid were (more than one formula for FAA
has been published).  FAA was concocted in an attempt to make a universal
fixative and preservative, but in truth there is no reason to use the
mixture of chemicals it contains.

If you have access to a density meter of hydrometer, you might start by
checking the fluid to see what the density is.  Formaldehyde is mostly
water, so it won't interfere much and most of the formulas call for small
amounts of acetic acid, so that may not be much of a factor either, leaving
you with a density that should be close to what the alcohol content is.
Based on that, you can then stage the specimens up to a solution of 70%
ethyl alcohol (diluted with distilled or deionized water) by increments of
20%.

If you don't have access to a density meter or hydrometer, in the short term
you can top up with 70% ethyl alcohol, but you run a risk of not having
sufficient alcohol to be a biocide (that will depend on the alcohol
concentration of the present fluid).

Concerning the samples that are completely dried out--are the specimens
completely dry, or still moist and pliable?  If they are moist, you should
stage them into 70% ethyl alcohol by 20% steps.  If they are dry, you can
place the specimen and/or the container and specimen together on a rack over
a pool of distilled or deionized water that has a few thymol crystals in it
until the specimens are softened (the thymol is to prevent bacterial growth
in the water), then stage them up to 20%.  Don't try to rush the
re-hydration, but monitor the specimens for signs of mold or bacterial
growth.

If you have other questions, feel free to contact me off-list.

--John

John E. Simmons
Museologica
1528 ½ Puddintown Road
State College, Pennsylvania 16801
simmons.johne at gmail.com
303-681-5708


On Feb 7, 2008 2:16 PM, Deborah A Lewis <dlewis at iastate.edu> wrote:

> We have recently acquired for deposit in ISC more than 100 bottles of
> liquid-preserved charophytes (Chara, Nitella and Tolypella --
> stoneworts) that in part are vouchers for a study done in the 1970s.
> I haven't checked for sure, but I think that the preservative is FAA.
> The amount of liquid remaining in the bottles varies -- some bottles
> are (nearly) full, some samples are completely dried out, and others
> are at levels in between. I am looking for suggestions on how these
> samples should be handled. Should they simply be topped-off? And if
> so, with what? Should the preservative currently in the bottles be
> decanted as much as possible and replaced with ethanol? (if so, what
> is the recommended percent ethanol?) Or with 70% ethanol/1%
> glycerol/water or some other preservative? Should the samples be
> "rinsed" with ethanol and then bottles filled with ethanol or some
> other preservative?
>
> Thanks in advance for any help with this!
> Deb Lewis
>
>
> Deborah Lewis, Curator
> Ada Hayden Herbarium    Phone: 515-294-9499
> 340 Bessey Hall         FAX:  515-294-1337
> Iowa State University           Email: dlewis at iastate.edu
> Ames, IA  50011-1020
>
>


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