[Nhcoll-l] What water to use with spirit specimens

[Dirk Neumann]

Hi Tonya,

this depends on the quality of your tap water; if your tap water uses 
chemicals such as Cl2 or others for purification, or such chemicals are 
used occasionally in the pipe system to prevent microbial growth, you 
should test your water first or request this data from your local water 
supplier. Also, if your tap water is known to have low ion-loads (e.g. 
because of respective filters or other mechanical purification by your 
water supplier), the desired effect might be marginal.

What Simon describes is sedimentation (mainly) of carbonates; if you use 
tap water, the mixture needs to rest for one day until the alcohol can 
be used, because the shifts in the solubility equilibrium will cause 
precipitation of ions.

If these are mainly carbonates (cf. data of your local water supplier), 
that the minerals can be suited to stabilise the specimens inside jars 
or to buffer against pH-shift. However, we know little about the ion 
activity of hydrogen-ions in alcohol mixtures and their effect on 
pH-shifts and measuring of the pH in alcohol mixtures is a tricky task 
(the only reliable way would be titration).

On the other hand, distilled or bi-distilled water attracts CO2 from the 
surrounding air and leads to pH values of 5 or lower in freshly 
distilled water.

So there are pros and cons. We have very good and pure tap water here in 
our museum, and I have been using tap water for nearly 20 years without 
any negative results.

Hope this helps
Dirk


Am 27.09.2018 um 18:43 schrieb Simon Moore:
>
> Hi Tonya, I have found it okay to use tap for diluting formalin 
> whereas alcohol produces a precipitate with tap so I use deionised or 
> RO for diluting alcohol.
>
> Best, Simon
>
> Sent from my Windows 10 device
>
> *From: *Tonya.Haff at csiro.au <mailto:Tonya.Haff at csiro.au>
> *Sent: *27 September 2018 03:31
> *To: *nhcoll-l at mailman.yale.edu <mailto:nhcoll-l at mailman.yale.edu>
> *Subject: *[Nhcoll-l] What water to use with spirit specimens
>
> Hello all,
>
> I’ve been thinking about the best water to use for diluting ETOH down 
> to 70% for storing formalin-preserved vertebrates.  Early on I was 
> taught to only every use deionised water, to avoid the introduction of 
> other chemicals, impurities, etc. However,  I have recently heard that 
> using good quality tap water may be in fact better than 
> deionised/demineralised water, as deionised water is not in a stable 
> state and so can in fact pull minerals out of the specimen. I would 
> love to hear what other people use and what your thoughts may be on 
> this. Thanks!
>
> Cheers,
>
> Tonya
>
> ---------------------------------------------------------
>
> Dr Tonya Haff
>
> Collections Manager
>
> Australian National Wildlife Collection
>
> National Research Collections Australia, CSIRO
>
> Canberra, Australia
>
> Phone: (+61) 02 62421566
>
>
>
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-- 
Dirk Neumann

Tel: 089 / 8107-111
Fax: 089 / 8107-300
*new email: neumann(a)snsb.de*

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Staatliche Naturwissenschaftliche Sammlungen Bayerns
Zoologische Staatssammlung München
Dirk Neumann, Sektion Ichthyologie / DNA-Storage
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81247 München

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---------

Dirk Neumann

Tel: +49-89-8107-111
Fax: +49-89-8107-300
*new email: neumann(a)snsb.de*

postal address:

Bavarian Natural History Collections
The Bavarian State Collection of Zoology
Dirk Neumann, Section Ichthyology / DNA-Storage
Muenchhausenstr. 21
81247 Munich (Germany)

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