[NHCOLL-L:4490] RE: resitivity for water used in wet collections?

[Rogers, Steve]

Dear Ms Opitz,

 

Mixing ethyl alcohol with tap water often creates a precipitate made of inorganic salts of calcium and other dissolved ions. Just adding tap water often creates a cloud of material of which only some will settle and the rest may remain suspended because of the fine nature of the material. Distilled water is the proper choice as it is essentially free of contaminant, but I have used the water I obtain from my de-humidifier I run in my basement at home which is “free” as we don’t have a distiller on premises.

 

Also, rather than completely changing the fluid, it probably is better to simply bring up the specimen to 75% from a lower concentration of ethanol. Every time you change fluids totally more material leak out of the specimen - fats or colors or other things. There is an equilibrium that the specimen had inside the fluid and if you change the fluid entirely, it modifies the remaining specimen. I have always used a hydrometer to check the concentration and bring the lower concentrations up to 70% by simply adding full strength alcohol.

 

Formalin based fluids should be stepped up from rinsing in water going through a series of concentrations - perhaps a day at 40% ethanol, then a day at 50%, followed by 70% for a week, switching out the fluid to remove the formalin which leaches out to the solution each time. I use the second rinse solution from a jar as the first rinse solution on another jar as the concentration of alcohol has often dropped from 50% back down to 40% as it reaches equilibrium with the specimen leaching formalin out and alcohol into it.

 

Get a copy of John Simmons’ book Herpetological Collecting and Collections Management, it is invaluable.

 

Stephen P. Rogers (Mr.)

Collection Manager of Section of Birds

and Section of Amphibians and Reptiles

Carnegie Museum of Natural History

4400 Forbes Avenue

Pittsburgh PA 15213-4080

Phone: 412-622-3255 or 3258

Email: rogerss at CarnegieMNH.org

http://www.carnegiemnh.org/birds/index.html

http://www.carnegiemnh.org/herps/index.htm

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From: owner-nhcoll-l at lists.yale.edu [mailto:owner-nhcoll-l at lists.yale.edu] On Behalf Of Opitz, Cindy
Sent: Tuesday, September 01, 2009 12:05 PM
To: 'NHCOLL-L at lists.yale.edu'
Subject: [NHCOLL-L:4488] resitivity for water used in wet collections?

 

I’m new to processing wet collections-not a collector of new specimens, but faced with transferring existing collections into newer fluids, due to evaporation, etc.  I understand the transfer process, and I’ve been told I should use de-ionized water, but I’m unclear about what resistivity is desired for the de-ionized water we mix with ethanol for our storage solution. I have available to me a Type I system, including a sink spigot with water reading 13-15.4 MΩ, and a wall box that filters the same water to a reading of 18.3 MΩ.  Are both appropriate for using in storage (with ethanol) of natural history specimens, or do we really need that extra boost to an 18+ reading?  The sink spigot would fill our water container about 20 times faster than the wall box.

Our wet collections include leeches, crayfish, small rodents, reptiles, and amphibians, which have been collected over the past 150 years and until now have been stored in a variety of fluids (70% EtOH, 95%, and some formalin-based).  We’re standardizing to 75% EtOH.

I’m grateful for any advice you might offer!

 

Cindy Opitz

Collections Manager

Pentacrest Museums: Museum of Natural History

and Old Capitol Museum

11 Macbride Hall

The University of Iowa

Iowa City IA 52242

319-335-0481

www.uiowa.edu/~nathist

www.uiowa.edu/~oldcap

 

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