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

[Tom Schiøtte]

In support of Dirk (below): For small and thin-shelled mollusks destilled water is horrible. After a few years you have no shell left. Here in Denmark our tap-water is deep ground water, and Denmark is built on cretaceous chalk. Under those conditions I use tap water and with good results.

Tom


Tom Schiøtte

Collection manager, Echinodermata & Mollusca
Natural History Museum of Denmark (Zoology)
Universitetsparken 15
DK 2100 Copenhagen OE

+45 35 32 10 48
TSchioette at snm.ku.dk<mailto:TSchioette at snm.ku.dk>



From: Nhcoll-l <nhcoll-l-bounces at mailman.yale.edu> On Behalf Of Dirk Neumann
Sent: 28. september 2018 11:21
To: nhcoll-l at mailman.yale.edu
Subject: Re: [Nhcoll-l] What water to use with spirit specimens

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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