[NHCOLL-L:3349] (no subject)

[Chris Conroy]

NHColl,

       Here are replies to my questions about Densitometers, 
hydrometers, etc. , and question about transferring from denatured 
etoh to non-denatured ethanol.

Thanks,

Chris Conroy


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1. I have always used the floating hydrometers that wine-makers use and
then a thin graduated cylinder to float them in - I think I obtained
them from Fisher Scientific. I can check down to 8 fluid oz. jars, and
then adjust accordingly the concentration - most of the time bringing it
up to 70%. While the collections of fluids I care for close to your size
210,000 catalogued herps, circa 10,000 uncatalogued, and 6000 fluid
birds, I only have circa 16,000 jars and 220 tanks. You will probably
use many barrels of alcohol to bring the collection up to proper
concentration.

2. Denatured alcohol is not all created equal. You can purchase
Denatured alcohol from 10 different companies, and each can use a
different chemical to denature it with. How a specimen holds up can
differ with what is contained in the solution. You can Google different
companies and find many denaturing agents. If the person donating the
collection has records of what company they purchased the fluid from,
you might find additional info. I also would NOT transfer to 95%
ethanol. If they are in formalin, leave them there but perhaps add
buffering agents. If in 80% denatured, I would transfer to 80% standard
ethanol.


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To check the concentration, I recommend a digital density meter. 
These are far more accurate than hygrometers and require a much 
smaller volume of fluid for the measurement.

There are a lot of approved denaturants used in alcohol.  It is rare 
that we know what particular denaturants were used in any one batch 
of ETOH.  You should note in the catalog or other specimen records 
that these specimens were kept in denatured alcohol even though you 
probaby won't be able to find out which chemicals were added to it.

I do not recommend keeping tadpoles in alcohol--they dehydrate badly 
and shrivel up.  If they are not yet dehydrated, I would probably 
change them to a standard buffered 10% formalin by staging through 
concentration steps of about 20%.

The use of density meters, the problem of unknown denaturants, and a 
protocol for staging specimens from one soltuion to another can be 
found in "Herpetological Collecting and Collections Management" 
(2002), available from the Society for the Study of Amphibians and 
Reptiles.

**************************************************

We usually mark with a wax pencil the glass top or plastic lid of 
tested jars with a code like CA07 to show the alcohol was checked, 
the jar topped up and the lid or gasket changed in 2007.  We also 
fill our jars right to the brim.  By being filled to a standard 
level, we can easily pick out problem jars or fasteners by noting if 
the alcohol level drops below our standard fill height.  Every time 
any jar is opened, we go through the testing (unless it has been 
tested before) and topping and relidding.  This ensures that the 
bottles will be trouble-free for years to come.

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We use a Densito Density Meter by Mettler Toledo to check our alcohol 
collection.  We bought it from Fisher Scientific in 2002.  The rep 
gave us a substantial discount, so we ended up paying approximately $ 
1800.00 before shipping.

I know this isn't cheap, but it is portable and fairly easy to use 
once you have figured it out.


**************************************************

In reponse to your enquiries:
Have you tried Anton Paar Ltd for the hydrometer?  Not sure how 
reasonably-priced they are but you never know.

If you're keeping material for DNA purposes then stick to alcohol. 
Formalin is OK for fixation and should be used anyway since alcohol 
fixation is more stabilising through rapid dehydration and causes 
tissue damage.  I would advise keeping your specimens in the 80% 
alcohol and those for DNA may be transferred to 96%.  Watch out for 
evaporation which also dilutes the alcohol since a transfer leap of 
over 20% (alcohol strength) can cause osmotic stress to the tissue.

Long-term storage in formalin will cause DNA coding to be masked.

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To keep track is tricky, dependant on previous consciencious curators 
and conservators - ha!  Excuse the cynicism.  I designed a label some 
while ago which just has Fixative.............. 
Preservative......... printed on the bottom line and if the fixative 
is unknown I just add a ? mark so that ast least I know.  The 
preservative can be analysed by the normal specific gravity testing 
of course, or, and I still find this alarming, by the 'sniff test' 
but you can't stop human nature!

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