[NHCOLL-L:3751] Re: Liquid-preserved charophytes

[Moore, Simon]

Hi,
 
Just a quick rider to add to John Simmon's reply.  If you don't have a hydrometer you can also try a Schleren optics test - won't help you quantitavely but will tell you if glycerol or a denser water-miscible fluid is present: try pipetting a drop of the mystery fluid into a container if water - if you see lots of wiggly mixing lines (Schleren optics), then you have a denser fluid.  A useful test but it won't distinguish between glycerol and glycols.  I always advocate the addition of a humectant.
 
As John said, don't rush the rehydration but keep and eye on the specimens - charophytes can rehydrate slightly irregularly and end up with air bubbles inside them but which should gradually dissipate in the IMS.
 

With all good wishes, 
Simon Moore, MIScT, FLS, ACR, 
Senior Conservator of Natural Sciences. 
Hampshire County Council 
Recreation & Heritage Department, 
Museums & Archives Service, 
Chilcomb House, Chilcomb Lane, 
Winchester SO23 8RD. UK. 
Internal  8 327 6737 
01962 826737 
http://www.hants.gov.uk/museum/biology 

ALFRED THE GREAT: Warfare, Wealth & wisdom 
2 February - 27 April 

A momentous, once-in-a-lifetime exhibition in The Gallery, Winchester Discovery Centre, Jewry Street, Winchester. 
Information:  www.discoverycentres.co.uk/winchester <http://www.discoverycentres.co.uk/winchester>  
Ticket hotline: www.theatre-royal-winchester.co.uk <http://www.theatre-royal-winchester.co.uk/>  
Supported by the Heritage Lottery Fund and Renaissance SE 

 

________________________________

From: owner-nhcoll-l at lists.yale.edu [mailto:owner-nhcoll-l at lists.yale.edu] On Behalf Of John E Simmons
Sent: 08 February 2008 03:33
To: dlewis at iastate.edu
Cc: NHCOLL-L at lists.yale.edu; herbaria at nacse.org
Subject: [NHCOLL-L:3747] Re: Liquid-preserved charophytes


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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