[NHCOLL-L:4497] RE: resitivity for water used in wet collections?

[Moore, Simon]

Hi Cindy,
 
Resistivity should hold no problems for alcohol dilution but check the pH of the water before any dilution is carried out as sometimes this can be quite low (5 or below).  For diluting alcohol with tap water, you may get some precipitation occurring, depending on the water coming through your pipes.  
You seem to have chosen a percentage between the USA (70%) and UK (80%) - playing safe?
Do you have a DMA 35n meter (via Anton Paar) for checking alcohol specific gravity?  Reason I ask is that alcohol self dilutes as it evaporates so that a low level of alcohol in a jar may only be 30% alcohol and topping it up may give you a total percentage of about 60%!  Also, the more fragile specimens don't appreciate the sudden osmotic pressure change due to a sudden raising of alcohol percentage and may need taking up an alchohol dehydration ladder to the required 75%.
Let me know if you need any more info. particularly with ordering a meter (they're quite expensive!)

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


 

________________________________

From: owner-nhcoll-l at lists.yale.edu [mailto:owner-nhcoll-l at lists.yale.edu] On Behalf Of Opitz, Cindy
Sent: 01 September 2009 17:05
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

 

-------------- next part --------------
An HTML attachment was scrubbed...
URL: http://mailman.yale.edu/mailman/private/nhcoll-l/attachments/20090902/cf046b14/attachment.html